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Jason Floyd edited this page Jul 17, 2024 · 344 revisions

Future Release

Bug Fixes

  • Fixed bug where a user specified RADCAL_ID was ignored

FDS 6.9.1 (v7 beta) (April 9, 2024)

Outputs

  • Add VIEW_ANGLE for particle-based flux gauges.

Bug Fixes

  • Fixed bug related to BURN_AWAY of OBSTs at mesh boundaries.

  • Fixed issue with particle initialization near mesh boundaries (affects sprinkler nozzles located directly on a mesh boundary).

  • (Unstructured Geometry) Fixed particle transport along surfaces of GEOM faces.

  • (Unstructured Geometry) Fixed AIT_EXCLUSION_ZONE for near GEOM surfaces.

Known Issues

  • (Unstructured Geometry) An issue remains with particles turning corners on non-grid aligned geometry.

  • The default MINIMUM_LAYER_THICKNESS on SURF was changed from 1E-6 m to minimum of 1E-4 m or 10 % of the layer THICKNESS. This was done to address numerical stiffness in the wall temperature solution when a pyrolyzing layer becomes very small. For very fine grids (e.g., mm scale) the new default may be too high and setting a smaller value may be required.

FDS 6.9.0 (v7 beta) (March 21, 2024)

New Features

  • The SPyro (Scaling Pyrolysis) method is a new, practical way to model pyrolysis in FDS when cone calorimeter data exists for the material of interest. You can take multiple sets of cone data that vary the reference flux and/or the tested sample thickness and FDS will use the local incident heat flux on the surface to determine the mass flux of pyrolyzate gas into the domain. See the pyro_cone_demo series in the Examples\Pyrolysis\ folder.

  • New ember generation method for use with LEVEL_SET_MODE=4. See the new inputs EMBER_YIELD and EMBER_TRACKING_RATIO on the SURF line.

  • New ember ignition method for spotting with LEVEL_SET_MODE={1,2,3,4} based on the distribution parameters EMBER_IGNITION_POWER_MEAN and EMBER_IGNITION_POWER_SIGMA on the SURF line. See the LS4_ember_ignition case in the Examples\WUI\ folder.

  • RESULTS_DIR may be added to DUMP to organize Smokeview files in your working directory.

  • New external ramp control. It is now possible to externally control the value of a RAMP or the state of a CTRL during a simulation. This feature is a beta feature. See the section on External Control of FDS in the chapter on Devices and Controls Logic.

Enhancements

  • General improvement of 3D heat transfer algorithm.

  • TUNNEL_PRECONDITIONER on PRES may be used with the ULMAT pressure solver.

  • Alternative pressure solvers can now handle different pressure zones, pressure zone changes.

  • Implemented unstructured finite volume method to improve radiation solver with complex geometry.

  • BLOWING has been added to SURF. For non-DNS cases, this adjusts the computed heat transfer coefficients to account for inflow or outflow at the surface.

  • Added HEAT_TRANSFER_MODEL='IMPINGING JET'. This affects flows with stagnation points where under-resolved velocity fields lead to low Reynolds numbers computed near the wall and hence a fictitiously low heat transfer coefficient with typical forced convection correlations.

  • The natural convection correlation for a horizontal surface now accounts for the direction of the temperature gradient.

  • Added RAMP_HEAT_TRANSFER_COEFFICIENT and RAMP_HEAT_TRANSFER_COEFFICIENT_BACK to SURF.

  • ORIENTATION_RAMP has been added to INIT. This controls the orientation of a group of particles placed with an INIT line.

  • CTRL_ID_DEP and DEVC_ID_DEP have been added to RAMP. During RAMP evaluation, specifying one of these will result in the RAMP output being the value of the CTRL or DEVC specified.

  • Improved the logic that checks for sufficient HVAC loss definitions in a duct network.

  • Can specify 3D temperature and species fields using TMPFILE and SPECFILE on CSVF.

  • A table of common combustion, toxic, and reference species that are predefined has been added to the User's Guide to make it easier to find common species.

  • Error messages written by FDS now have error codes that are tabulated in the FDS User's Guide with cross references to applicable Guide section.

  • A particle with a SURF_ID can be defined as TARGET_ONLY. FDS will compute 1D heat transfer into the particle but the particle will not exchange energy with the gas phase.

Outputs

  • PROFile outputs can now use any solid phase QUANTITY that takes a DEPTH.

  • Added solid phase outputs for the 'SOLID CONDUCTIVITY' (optional MATL_ID), 'SOLID MASS FRACTION', and 'SOLID ENTHALPY' (optional MATL_ID) at a DEPTH.

  • Added the gas phase output 'EFFECTIVE FLAME TEMPERATURE', the temperature consistent with the local radiant emission when using a specified radiative fraction.

  • Added 'FIRE DEPTH' output quantity, used in computing the depth of a fire line in wildland fires, for example.

  • DIAGNOSTICS_INTERVAL may be specified by the user which controls the time step interval at which detailed mesh information is written to the .out file.

Verification and Validation

  • Added section on compartment fire growth predictions to validation guide including JH/FRA room-corner experiments.

  • Added section on SPyro bench-scale validation to validation guide.

Bug Fixes

  • Fixed a bug that occurred when particles were killed due to MAXIMUM_PARTICLES being reached.

  • Fixed a bug for DEVC using DB where the centroid of the whole domain was not in a MESH.

  • Fixed a bug where CTRL_ID or DEVC_ID did not correctly turn on/off a VOLUME_FLOW FAN.

  • Fixed a bug when applying SMOOTHING to a DEVC with a TEMPORAL_STATISTIC other than 'INSTANT VALUE', 'TIME AVERAGE', or 'SMOOTHED'.

  • Re-add liquid properties for 'METHANOL' which were inadvertently deleted during 6.8.0 source code reorganization.

  • Several improvements and bug fixes to complex geometry routines.

  • RAMP_T_I added back as an input for SURF.

  • Fixed miscellaneous initialization errors leading to different behavior in gnu and intel build targets.

  • Require an explicit ORIENTATION for gas phase devices like GUAGE HEAT FLUX GAS.

FDS 6.8.0 (v7 beta) April 18, 2023

Planned major changes include:

  • Complex geometry option (the GEOM namelist)

  • 3D heat transfer (includes thin OBST, implicit time step, independent from gas phase resolution)

  • 1D heat transfer no longer limited to zero or one-cell thick obstructions

  • Improved handling of "pressure zones", including diagnostic print-out for each zone, and a better treatment of normal velocity at thin obstructions bordering a pressure zone. There is also a new parameter that allows users to fill small voids whose volumes are less than a user-specified MINIMUM_ZONE_VOLUME. These small voids are often the source of numerical instabilities.

  • HVAC network component and data visualization in Smokeview. This adds WAYPOINTS for ducts (to better visualize the actual route) and DUCT_QUANTITY_ARRAY and NODE_QUANTITY_ARRAY to specify Smokeview outputs. Status of fans, dampers, and air coils is similar to sprinkler status.

  • Ability to specify multiple simple chemistry reactions. To support this some inputs have moved from COMB to REAC. Additionally, one can now use SPEC_ID and MASS_FRACTION with HRRPUA and MLRPUA to specify mixtures of fuels or mixtures of fuels and diluents.

  • Identification of problematic void pressure zones and optional filling of small void volumes

Other changes:

  • ASSUMED_GAS_TEMPERATURE on MISC has been replaced by TMP_GAS_FRONT and TMP_GAS_BACK on SURF with optional RAMP_TMP_GAS_FRONT and RAMP_TMP_GAS_BACK.

  • The default formula for SOOT is now C and SOOT_H_FRACTION has been removed from REAC. To specify a different formula for SOOT use FORMULA on SPEC.

  • Smoothing of heat flux for the CONE_HEAT_FLUX pyrolysis model using CONE_FLUX_SMOOTHING_WINDOW on SURF

  • New method for finding the operating point for a fan on its fan curve. Enabled by setting HVAC_QFAN on MISC

  • Add REFERENCE_ENTHALPY and REFERENCE_ENTHALPY_TEMPERATURE to MATL to set a material reference enthalpy. FDS will now attempt to set references enthalpies automatically to ensure energy conservation when a MATL has a reaction. This can be disabled by setting ADJUST_H on MATL.

  • EVAP_MODEL moved from MISC to PART and changed from an integer to a character string

  • TIME_CONSTANT option for thermocouples

  • OPTICALLY_THIN=T automatically sets KAPPA0=0

  • Allow direct specification of front and back wall temperature values in 1D heat transfer solver

  • Allow variable specific heat in EXTINCTION 1 model

  • SUSPEND_PRESSURE_ITERATIONS=F by default

  • A new "pilot fuel model" allows different fuels to have different AIT values, hence one fuel may be set to burn without an ignition threshold (the "pilot fuel" with AIT=0 K) and other fuels may be subject to an ignition threshold to prevent spurious reignition in under-ventilated fires

  • Allow change of output frequency with RESTART=T. For example, a change in DUMP line parameters DT_DEVC, etc., will overwrite whatever was previously stored in the restart file. Any parameter that is set automatically (e.g., DT_HRR) will resume from the prior run unless explicitly set in the new input file. Note, however, that DT_RESTART will not persist from the previous run unless explicitly set in the new run (this prevents accidental overwrite of the restart files).

  • A much larger selection of species (over 300) are now predefined inlcuding specific heat, Gibbs energy, heat of formation, and Lennard-Jones parameters.

  • Finite rate chemistry now supports automatic specification of N_S, catalytic reactions, and third body reactions with non-unity collision efficiencies. Reverse reactions no longer require specification of the reverse reaction with a seperate REAC input and the standard concentration correction factor was added to the reverse rate.

  • Char model for vegetation updated to include oxygen mass transfer to solid surface. This model is invoked by SURFACE_OXIDATION_MODEL and the parameters NU_O2_CHAR and BETA_CHAR are no longer used.

  • Heat flux outputs that the outgoing radiation from a surface, such as NET HEAT FLUX, now use the linearized outgoing flux for thermally thick surfaces, without an ABSORPTION_COEFFICIENT, Eq. (L.8) in the Technical Reference.

  • Values read in from a BULK_DENSITY_FILE can now be scaled with BULK_DENSITY_FACTOR.

FDS 6.7.9 (June 28, 2022)

  • There were several validation cases (Loughborough Jets, Purdue Flames, SWJTU Tunnels) that had failed due to numerical instabilities:

    • For the Loughborough cases, a pressure gradient force is now used rather than a specified wind. This improves numerical stability at the outlet, where a turbulent combusting jet interacted with an open boundary. Input file commit

    • For the Prudue Flames cases, a minimum Nusselt number is needed at the burner surface. This had been accidentally removed during an overhaul of the convective heat transfer routine. Source commit

    • For the SWJTU Tunnel cases, a bug had been introduced to the ENTHALPY_ADVECTION routine where thin obstructions were not handled properly. Source commit

  • Per the "Known Issues" with 6.7.8, restarts would fail if the original job finished. FDS was automatically outputting restart files at the last time step. This issue has been resolved.

Known Issues with FDS 6.7.8

  • There is a problem running 6.7.8 on Windows from the FDS command prompt. See Issue #10668.

  • There is a problem with the restart. See Issue #10677.

FDS 6.7.8 (May 25, 2022)

  • FDS+Evac no longer supported. This was a difficult decision, but it has become clear that we do not have the bandwidth to maintain FDS+Evac together with continued development of FDS. Please refer to the FDS+Evac website for further information.

  • The treatment stress and vorticity at external "corner edges" has changed. This change was made to fix issues with specified tangential velocity components applied at vents. This change may result is noticeable differences in the flow field near vent outlets for coarse calculations.

  • There are now two executables distributed in the bundle. One is optimized for a single thread (about 20 % faster) and should be used for MPI calculations without OpenMP. The second executable, appended with _openmp, includes OpenMP compile directives and should be used for multi-thread calculations.

  • VOLUME FLOW, MASS FLOW, and HEAT FLOW have been removed. See the User's Guide for details on how to obtain these outputs using other QUANTITY types.

  • Added the TEMPORAL_STATISTIC of SMOOTHED. This outputs the value of a DEVC after applying SMOOTHING FACTOR; this is the value used in evaluating a SETPOINT or the input to a CTRL.

  • Added the output file CHID_devc_ctrl_log.csv. This output file logs each time a DEVC or CTRL changes state.

  • HVAC Changes:

    • Added the HVAC QUANTITY of NODE SENSIBLE ENTHALPY which outputs the sensible enthalpy in kJ/kg of a duct node.
    • Added the HVAC QUANTITY of DUCT LOSS which outputs the loss coefficient for a duct (wall loss, plus duct fitting loss, plus node loss allocated to duct).
    • Renamed the DUCT ENERGY FLOW to DUCT ENTHALPY FLOW to be consistent in naming and calculation to the related gas phase quantity ENTHALPY FLUX.
    • Added AREA as an input for an HVAC FILTER.
    • Added a check to stop FDS when no losses are specified for an HVAC network without fixed flows.
    • A modified approach to setting the node pressure for HVAC was added to improve the stability of HVAC models.

  • If both CONVECTIVE_HEAT_FLUX and TMP_FRONT are specified for a surface type, FDS will now compute the heat transfer coefficient to achieve the desired flux rather than exiting on an error.

  • Solid phase reaction rate expression changed slightly for reactions that are not of first order.

  • XB on ZONE has been removed. ZONEs now use XYZ only.

  • Added a feature to import a BULK_DENSITY_FILE with information on the 3D distribution of vegetation bulk density. See the User's Guide for details of this feature, including the proper file format.

  • We now automatically perform the angular integration for 2D cylindrical mass loss rate output, including the heat release rate in the CHID_hrr.csv file. Additionally, surface integrals in 2D cylindrical now account for angular integration. These changes make the 2D cylindrical output nominally equivalent to a 3D case for easier comparison (the output is no longer dependent on the arbitrary choice of DY in the input file).

  • Added a new pressure solver PRESSURE_SOLVER='ULMAT', which stands for "Unstructured Local MATrix" solver. For meshes with internal solid boundaries, this solver uses the PARDISO solver from Intel MKL as an unstructured solver. For meshes in which the FFT solver boundary conditions are exact, CRAYFISHPAK is used. Approximate boundary conditions are sill applied at mesh interfaces, but solid boundaries are treated exactly (no immersed boundary method), making this solver a good choice for cases with tight mass conservation requirements, like tightly sealed pressure zones.

  • Add SPATIAL_STATISTIC='INTERPOLATION' in the first off-wall grid cell.

  • CHECK_HT=T by default with HT3D. This is needed to avoid numerical instabilities in the explicit scheme. Note it will result in significant time step restrictions compared to previous versions.

FDS 6.7.7 (Nov 19, 2021)

  • TUNNEL_PRECONDITIONER now works with an arbitrary number of MPI processes, including just one.

  • Add TEMPORAL_STATISTIC='FAVRE RMS'; Favre statistics now work with SPATIAL_STATISTIC='INTERPOLATION'.

  • Add ability to evaporate liquid mixtures.

  • Allow SPATIAL_STATISTIC for a linear array of devices.

  • Add TEMPORAL_STATISTIC to record time to peak value.

  • Add SPATIAL_STATISTIC to compute centroids.

  • Add output for memory (RAM) usage on linux platforms.

  • Add HRR_GAS_ONLY to neglect surface oxidation reactions in total HRR output.

  • Add EMBER_GENERATION_HEIGHT(2) to generate embers at a given height over burning surfaces.

  • Fix bug in RESTART.

FDS 6.7.6 (June 1, 2021)

  • Default NEAR_WALL_TURBULENCE_MODEL set to 'WALE'.

  • A feature has been added that stabilizes simulations of fires or ventilation in long tunnels. The parameter, TUNNEL_PRECONDITIONER=T on the PRES line causes FDS to solve a 1-D equation for the pressure along the length of the tunnel, greatly speeding up the iterative solution of the Poisson equation for pressure.

  • Mean forcing for wind has been removed, but the basic input parameters for wind remain the same.

  • A gas phase device for 'GAUGE HEAT FLUX' has been added, similar to 'RADIATIVE HEAT FLUX GAS'.

  • The FDS source code now conforms to the 2018 standard.

  • FDS now uses the 2008 Fortran MPI bindings, i.e. USE MPI_F08 instead of USE MPI.

  • Eight point linear interpolation of device output has been added. To access this feature, use SPATIAL_STATISTIC='INTERPOLATION'.

  • Sprinklers and nozzles can be located on or near mesh boundaries.

  • One can create a conically-shaped fixed volumetric heat source.

  • Known droplet issue in FDS 6.7.5 was fixed.

  • Can now specify a PART_ID for a MATL reaction.

  • Can now specify VEL_PART on SURF to assign a velocity to particles being emitted by the surface that is different from any velocity due to gasses being introduced by the surface.

  • New outputs of 'SOLID CELL CONDUCTIVITY' and 'SOLID CELL SPECIFIC HEAT'

  • 'HCN_YIELD' added to REAC and 'FUEL_N__TO_HCN_FRACTION' to COMB.

  • Add subgrid turbulent dispersion model for massive particles (in beta).

  • Add TEMPORAL_STATISTIC='FAVRE AVERAGE'. Currently works with a single QUANTITY and no other statistics (in development).

Known Issues with FDS 6.7.5

  • A bug was introduced in FDS 6.7.5 that impacts the evaporation of droplets. In cases where the operation time of multiple sprinklers is being determined or where the cooling of gas from water droplets is being determine, it is recommended to use the latest test bundles or FDS 6.7.4.

FDS 6.7.5 (Aug 21, 2020)

  • Addressed issues running on AMD processors under Windows.

  • Added four options for using the level set fire spread algorithm for wildfire spread.

  • Fixed bug in burning rate with BURN_AWAY when an OBST abuts a mesh boundary.

  • Fixed bug in user stop of FDS+Evac with MPI

  • Intel has fixed a memory leak related to MPI, which was evident when using the global matrix Poisson solver and MKL library.

  • Added CONE_HEAT_FLUX on SURF which enables a simple model to extrapolate cone calorimeter data to a time-varying incident heat flux.

  • Improvements to volumetric heat sources. This includes allowing for both volumetric heat sources using INIT and gas phase reactions using REAC, specifying the volumetric source RADIATIVE_FRACTION on INIT, and excluding the volumetric heat source from the RTE correction scheme (avoids averaging the source output over any gas phase reaction that is occuring) by RTE_CORRECTION on INIT.

  • On PART, added MASS_TRANSFER_COEFFICIENT, HEAT_TRANSFER_COEFFICIENT_SOLID, and HEAT_TRANSFER_COEFFICIENT_GAS to allow for user specified values.

  • PROJECTION is now .TRUE. by default.

  • Add ABL (atmospheric boundary layer) HEAT_TRANSFER_MODEL (experimental). Uses Monin-Obukhov stability corrections for both momentum flux and heat flux wall functions (see Stoll and Porte-Agel, Boundary-Layer Meteorology, 2008).

  • Fixed a bug in updating the droplet temperature when a droplet is on a wall.

  • Improved the interpolation of wall temperature when a wall cell shrinks or swells.

  • Fixed a bug when MLRPUA is used when there is a MATL with a difference heat of combustion than that on REAC.

  • Add the output WALL ENTHALPY which gives the total enthalpy associated with a wall cell or a solid particle.

FDS 6.7.4 (March 9, 2020)

  • Allow particles to follow a PATH_RAMP(3) on the INIT line; particle DEVC output works as usual, so this has the effect of allowing DEVC positions to move in time

  • Fix bug with FDS+Evac and ZONEs

  • Fix bug in mass flux of species at exterior boundaries introduced in v6.7.3 for thin obstructions

  • Fix bug that prevented defining an INIT with a species mass fraction of 0 (i.e. override a non-zero MASS_FRACTION_0 on SPEC).

  • Fix bug in the initialization of pressure at ambient ducts nodes to correctly use the reference elevation.

  • Fix bug in the computation of the initial water vapor mass fraction for HUMIDITY.

  • Fix bug preventing the use of TMP_INNER or RAMP_T_I for a particle.

  • Generalize histogram generation for regular devices.

  • Improve MEAN_FORCING functionality by averaging velocity over entire domain, not just entire mesh.

  • Allow level set wildland fire fronts to cross mesh boundaries.

  • Make baroclinic pressure iteration work with GLMAT pressure solver.

Known Issues

  • There is a memory leak in the GLMAT and UGLMAT pressure solvers. This has been isolated as a problem with the Intel libraries and has been reported to Intel. As a work-around, use RESTART check-pointing frequently or dial down your VELOCITY_TOLERANCE and use the default FFT solver.

FDS 6.7.3 (Oct 31, 2019)

  • Allow thin obstructions to burn.

  • Force explicit setting of mesh transformation ID on MESH line via TRNX_ID, etc. This allows for much greater flexibility in assigning different transformations to different mesh groups for large-scale calculations.

  • STRETCH_FACTOR default value set to 2 for all surfaces, even burning surfaces. STRETCH_FACTOR controls the size of solid phase cells used to solve the 1-D heat transfer equation.

  • Fixed a bug involving pressure ZONEs. A post to the Forum on June 18th identified a bug where an OBST that formed a boundary between two ZONEs extended over multiple meshes and changed state during the simulation (i.e. had a CTRL_ID or DEVC_ID). As a result of the bug, the ZONEs were not properly initialized.

  • Fixed a bug in MIN/MAX CTRL functions.

  • Create a ZONE using a single XYZ point instead of an XB volume spanning multiple meshes.

  • Increase length of FORMULA (both REAC and SPEC) to 255 characters

  • PATH_RAMP on INIT can specify a path for a particle.

  • Added HEAT_OF_REACTION_RAMP to MATL to specify a temperature dependent heat of reaction.

  • Added RAMP_T_B to SURF to specify a time dependent back wall gas temperature.

  • Beta version of an aerosol scrubbing model.

  • Beta version of a condensation model.

  • CHECK_VN set to TRUE for all simulation modes.

FDS 6.7.2 (Invalid release)

FDS 6.7.1 (Feb 5, 2019)

  • Windows users not using a third-party graphical interface are now required to run commands from a special command prompt called CMDfds. This special command prompt sets a few path variables and executes a few scripts to ensure that the proper mpiexec command is invoked. We no longer use the command fds at the command prompt, but rather fds_local for jobs running only on the single computer, and mpiexec ... for multi-computer runs. See User's Guide for details.

  • Allow DEVC spatial STATISTICS to cross mesh boundaries. This includes quantities like 'PATH OBSCURATION' and 'LAYER HEIGHT'.

  • Allow combination of spatial and temporal statistics with the parameters SPATIAL_STATISTIC and TEMPORAL_STATISTIC. Deprecate the parameter STATISTICS on the DEVC line.

  • Add a method of extrapolating a temporal max or min to longer time periods. In other words, you can estimate the min or max value of a longer simulation using a statistical (Gumbel) method.

  • Modify 'EXTINCTION 1' such that for large grid cells (like 5 cm and up) extinction does not occur if the bulk cell temperature is greater than approximately 600 C. The exact value depends on the size of the cell.

  • Fix bug in solid phase 1D heat transfer routine when temperature-dependent properties are used. The grid resolution requirement was being over-estimated, causing significantly longer run times than were necessary.

  • SPATIAL_STATISTIC='AREA' added for gas phase.

  • Fix bug for flow loss in an ambient duct node.

  • Add 'ABSOLUTE PRESSURE' and 'DISSIPATION RATE' devices.

  • Add 'DUCT ENERGY FLOW' and 'NODE ENTHALPY' devices for HVAC calculations.

  • Fix bug when multiple MATL are burning on a SURF.

  • Add 'ABS' math control function.

  • Add deposition, agglomeration, and soot surface oxidation documentation to guides.

  • Fix bug in drag calculation of static particles, e.g., screens.

FDS 6.7.0 (June 20, 2018)

  • SIMULATION_MODE replaces RESEARCH_MODE to control the level of physics. For example, SIMULATION_MODE='DNS', sets the code to run in direct numerical simulation model. Other options include 'LES' (high-fidelity, convergent LES simulations), 'VLES' ("very large-eddy simulation" [default] for coarse-grained, practical LES calculations), and finally 'SVLES' ("Simple VLES", makes simplifying physical assumptions, such as constant specific heat ratio, to speed calculations when appropriate).

  • Create look-up table for CRITICAL_FLAME_TEMPERATURE based on minimum extinguishing concentration (MEC) measurements in cup burner experiments with nitrogen as the diluent.

  • FLUX_LIMITER is now specified using a character string on MISC. Defaults are automatically set by SIMULATION_MODE, as discussed in the user guide.

  • Create a new namelist group called COMB for various global combustion parameters, most of which are numerical and were previously specified on the MISC line. This new namelist group is intended to better organize these parameters, but will typically not be needed by most users.

  • Add PRIORITY to the REAC line for cases with multiple fast serial combustion reactions. Without this parameter, all fast reactions are performed in parallel.

  • Set the default radiation PATH_LENGTH to 0.1 m. Previously it was a function of the cell size.

  • Add I_LOWER_SKIP, etc., to MULT line to more easily embed a fine mesh within an array of coarse meshes.

  • Add SHAPE feature to OBST line. When combined with MULT this allows the user to "sculpt" a basic shape (sphere, cylinder, or cone) out of the obstructions.

  • PYRO3D in Beta testing.

  • Fix temperature error at horizontal mesh refinement boundaries with STRATIFICATION. This problem is relevant for atmospheric flow simulations with mesh refinement (coarsening) in the vertical direction.

  • Ensure that TMP_EXTERIOR at OPEN boundaries is properly applied in radiation transport equation.

  • Make RAMP_SPEED functional in WIND simulations.

  • Add CTRL function types for MIN and MAX.

  • Add XENON as a species to give a low conductivity gas.

  • On MISC remove HVAC_DT and add HVAC_LOCAL_PRESSURE. Setting to FALSE improves stability but requires that VENTs connected to the HVAC system lie in pressure ZONEs as this option no longer uses the perturbation pressure and only uses the background pressure plus any stagnation pressure (i.e. air blown at an inlet will still push air into a duct but a fire in a compartment without a ZONE will not).

  • Fix bug in output values for Fractional Incapacitation Concentration (FIC) with user-defined species.

  • Fix bug when sprinklers are present along with a VENT on a boundary that burns away.

  • Add drift flux model for gas phase thermophoretic movement of aerosols (THERMOPHORETIC_SETTLING on MISC)

FDS 6.6.0 (Oct 31, 2017)

  • Implementation of new implicit droplet evaporation scheme. Fixes many stability issues with droplet cases.

  • Add EXTINCTION_MODEL='EXTINCTION 3' for two-step fast CO chemistry. General cleanup of extinction routines. Change in critical flame temperature model to use post-combustion product specific heats. Change in default CFT to 1700 K. Users should take T(OI) (diffusion flame oxygen index) from SFPE Handbook Table 2-7.3 as CFT for specific fuels.

  • Add WIND namelist group. In addition, it is now possible, and preferred, that the user specify a wind and temperature profile using Monin-Obukhov similarity parameters. At a minimum, the user can specify a wind speed and direction, both of which can change in time, plus a parameter to characterize the terrain roughness and a parameter to characterize the stability of the atmosphere.

  • Add global linear matrix solver for pressure, SOLVER='GLMAT' on PRES (in beta). Uses Intel MKL sparse cluster solver and performs a direct solution of the pressure equation (no iteration). Resolves problems of velocity errors at mesh boundaries and velocity penetration errors at all solid boundaries (exterior domain and immersed). Efficiency relative to default FFT solver is problem dependent. Suggest using GLMAT when required velocity error tolerance is tight. See duct_flow_glmat and dancing_eddies_glmat for examples.

  • Multi-mesh capability added to 3D heat transfer in solids (HT3D). Volumetric heat source added to HT3D.

  • Add NEAR_WALL_TURBULENCE_MODEL parameter to MISC. Default is constant Smagorinsky. Newly available option is the Wall-Adapting Local Eddy-viscosity (WALE) model (in beta).

  • Add 'THERMAL WALL UNITS' output. Change 'YPLUS' output to 'VISCOUS WALL UNITS'.

  • Add RAMP_CP_L to SPEC for liquid specific heat ramp.

  • Add VOLUME_FRACTION to INIT namelist.

  • Fix bug when MESH has negative z-coordinates.

  • Fix bug for localized leakage that resulted in the creation of spurious species when there was a large difference between the gas temperature and the wall temperature on the inflow side of a leak.

FDS 6.5.3 (Jan 22, 2017)

  • Precompiled OpenMPI libraries are bundled with OSX and Linux release (to be extracted and installed by user, if desired).

  • Fix undefined heat of formation for unlisted species.

  • Fix bug in OPEN boundary condition at mesh corners.

  • The OPEN boundary condition is altered when MEAN_FORCING=T. The tangential component of velocity is taken from the specified U0, V0, or W0 for inflow (rather than FREE_SLIP). In the abscence of MEAN_FORCING, the user may invoke the new OPEN bc on a specific VENT with SURF_ID='OPEN', WIND=T.

  • Fix bug in PARABOLIC profiles for VENTs that span multiple meshes.

  • Fix bug in MIXTURE FRACTION output.

  • Add PERIODIC_MESH_IDS as a parameter on the MESH line. The ability to use periodic boundaries for multi-mesh cases was broken by the changes made to improve scalability of the code (FDS 6.4.0). Now the user must specify which boundary meshes are connected.

  • Add new chapter to FDS User's Guide to address atmospheric boundary layer parameters.

  • Solid Heat Transfer 3D (HT3D) is in beta testing.

  • Add HVAC_MASS_TRANSPORT (T/[F]) to MISC line to enable transient species and energy transfer in the HVAC sub-model (in beta testing).

FDS 6.5.2 (Aug 25, 2016)

  • Fix bug in particle transport algorithm sub-time step procedure.

  • Add QUANTITY='ADIABATIC SURFACE TEMPERATURE GAS' to get AST away from a solid wall.

  • Simplify discussion and implementation of output related to heat flux.

FDS 6.5.1 (Jul 6, 2016)

  • Fix bug in Windows installation which fails on non-English versions of Windows.

  • Eliminate spurious motion at mesh boundary where grid resolution changes.

  • Ensure VOLUME_FLOW consistent with PARABOLIC profile.

FDS 6.5.0 (Jun 23, 2016)

General Enhancements/Bug Fixes

  • Include computation of baroclinic torque term in the pressure iteration scheme. A number of users have reported numerical instabilities when simulating fires in long, sealed tunnels. The cause of the instabilities has been a mismatch in the pressure field that is solved for in the Poisson equation and the lagged pressure of the baroclinic term.

  • Input parameters added to iterate the radiation solver for multiple mesh cases, but no change in functionality has been made.

  • Fix bug related to discontinuity of HRR after restart.

  • Fix bug related to specific location leakage where LEAK_ENTHALPY=.TRUE.

  • Add HVAC quantities to the restart file

  • Improve method of interpolating particle drag onto grid for use in momentum equation. In the past, the drag was applied at the nearest cell face, whereas now the drag is linearly interpolated onto two nearest cell faces.

FDS 6.4.0 (Apr 5, 2016)

General Enhancements/Bug Fixes

  • Fixed bug in reaction divergence causing below ambient temperatures

  • Fixed bug in species boundedness correction for complex chemistry; this bug was affecting the simple CO mechanism used for Smyth Slot Burner and NIST RSE 1994 validation cases; the Arrhenius constant for the forward CO reaction in the modified Andersen mechanism was recalibrated against the Smyth DNS case with multiple grid resolutions

  • Fixed bugs in thermal conductivity and diffusivity for DNS

  • Limit correction to radiative transport equation (RTE_SOURCE_CORRECTION) to 10

  • RTE_SOURCE_CORRECTION has been made global, so there is a single value, even for multi-mesh calculations (previously RTE correction was done mesh by mesh)

  • Default Von Neumann stability constraint set to 1 from 0.5. This should speed up cases where spuriously high turbulent viscosity near edges was causing a severe time step restriction.

  • Various structural changes were made to enable FDS to run with thousands of MPI processes. Strong and weak scaling studies were added to the FDS V&V suite and reported in the FDS User's Guide.

  • CPU time usage is no longer reported as part of the diagnostic output in the CHID.out file. Instead, wall clock time of the various major subroutines is reported in a new file called CHID_cpu.csv. The times are reported as a function of the MPI process, not the mesh.

  • Remove clipping from gas temperature array

  • Fixed bug in HVAC bc for leakage vents. Inflow and outflow boundaries are handled with slightly different logic and the HVAC model was not appropriately selecting the correct set of logic.

  • Allow LEAK_AREA to be a function of compartment pressure via new ZONE inputs LEAK_REFERENCE_PRESSURE and LEAK_PRESSURE_EXPONENT.

Inputs

  • Add AUTO_IGNITION_TEMPERATURE to INIT namelist. This addresses the problem of spurious re-ignition at OPEN boundaries. You can now set a low AIT near the burner surface to act as an ignition source and set a high AIT elsewhere in the domain to prevent spurious re-ignition. An example may be found in the UMD_Line_Burner validation series.

  • IBLANK_SMV logical on MISC. If .FALSE., Smokeview does not store blanking array for obstructions (default is .TRUE.). IBLANK_SMV=.FALSE. speeds up loading Smokeview significantly, even for moderately sized jobs.

  • Add RAMP LOSS to HVAC DUCT input. Multiplies the LOSS by the output of the RAMP. This could be used to specify a variable position damper.

  • Add RAMP_CHI_R on REAC line for time variation of radiative fraction

Outputs

  • Add gas phase quantity SPECIFIC INTERNAL ENERGY

  • Fixed bug in VOLUME FLOW across multiple meshes

  • Fixed bug in RADIATIVE HEAT FLUX GAS across multiple meshes

  • Fixed bug in HRRPUV REAC

FDS 6.3.2 (Nov 18, 2015)

  • Fix an error related to evaporation of fuel droplets. This release is only a minor fix to 6.3.1.

FDS 6.3.1 (Nov 10, 2015)

General Enhancements/Bug Fixes

  • Fix error in mixing step of combustion model for multiple subtimesteps (does not affect simple chemistry)

  • Output a file called CHID_cpu.csv to record timings of individual routines

  • Output the version of the MPI library in the .out and .err files

  • Add a function call for GET_AVERAGE_SENSIBLE_SPECIFIC_HEAT

  • Fix issues involving the heat of formation for user defined fuels

Inputs

  • Add SUPPRESS_DIAGNOSTICS=.TRUE. on DUMP to reduce output for large jobs

  • Add the keyword DT_HVAC to MISC. If set, it will use the value of DT_HVAC specified in the HVAC solver rather than the FDS timestep. This can dampen oscillations in flow/pressure resulting from the fact that the HVAC pressure solution and the FDS pressure solution are not fully coupled. The downside is one will lose some time resolution for actual transient flows in ducts (the larger the value, the closer the solver will be to computing a steady-state solution at each timestep).

Outputs

  • Add QUANTITY='HRRPUV REAC' with REAC_ID to parse heat release rate from multiple reactions

FDS 6.3.0 (Oct 1, 2015)

Remove heat release rate limiter in combustion model

In past versions of FDS, a bound was set to limit the amount of heat that could be released in a given cell over a given time step. The bound was approximately 2000 kW/m3. Without this bound, numerical instabilities could occur if too much heat was added to a grid cell too quickly. Physically, it is impossible to for fuel and oxygen to react and produce such large amounts of energy in a given cell, but since we used a simple infinitely fast chemistry model, it could happen in the model. Now, we handle the combustion chemistry in such a way as to control the mixing time and prevent such large releases. Thus, the input parameters HRRPUV_AVERAGE and HRRPUA_SHEET, which allowed the user to set the upper bound on the heat release rate of a given cell, are not needed and have been removed.

Set default radiant fraction for various fuels

The default radiative fraction in FDS has been 0.35; that is, the fire is assumed to radiate 35% of its energy. Most users simply accept this value because the literature does not provide an extensive database of these values. Radiative fraction is not an intrinsic property of a fuel; it varies with the size and environment of the fire. However, some fuels, like methane (natural gas), are known to radiate approximately 20%; and some fuels, like heptane and heavier hydrocarbons, radiate approximately 40%. Starting with FDS 6.3.0, certain select fuels like METHANE and HEPTANE will have default values of RADIATIVE_FRACTION other than 35%. METHANE and the alcohols will be 20%; heavier hydrocarbons 40%. Fuels for which we have no traceable reference will remain at 35%. Also, RADIATIVE_FRACTION is now set on the REAC line, not the RADI line. Old input files will be stopped with an ERROR to emphasize the change.

Implement multi-fuel radiant fraction model [A. Gupta et al. FM Global 2015]

If multiple fuels are present, e.g., one fuel for cardboard and one fuel for polystyrene combustion, then the radiant fraction will be computed locally as reaction-weighted value. For example, if the two fuels are 20% and 40% radiative fraction with, respectively, 80% and 20% of the heat in a grid cell, CHI_R would be 0.8 x 0.2 + 0.2 x 0.4 = 0.24. Thus, CHI_R will vary in space and time.

Modify mu and k calculation for gas mixtures

Determining mu (dynamic viscosity) and k (thermal conductivity) for gas mixtures with high accuracy involves a fairly complex averaging process over all pairs of species in the mixture. Prior to FDS 6.3, this cost was avoided by using a simple mole fraction weighting. This method works well if the mixture components have similar molecular weights. For well-ventilated fires of ordinary combustibles, where the mixture in the computational domain is dominated by N2, O2, CO2, and H2O, this limitation is appropriate. In other uses, such as using FDS to examine hydrogen dispersion, this simple approach does not work as well. In FDS 6.3, a new weighting approach has been implemented using a method developed by the US Bureau of Mines. This approach weights by mole fraction and the square root of the molecular weight. Errors for compositions with large molecular weight differences have been reported as under 10 %.

Change to NASA polynomial fits for specific heats

Polynomial fits for specific heats were changed from JANAF data to NASA polynomials where NASA data is available. The main motivation for this change was to make it easier to do direct comparisons between FDS and Cantera, Chemkin, or other kinetics software where NASA polynomials are typically used. For most users this change will go unnoticed as the differences between the two sets of polynomial fits are small.

General Enhancements/Bug Fixes

  • Do not include molecular viscosity when computing output quantity SUBGRID KINETIC ENERGY

  • Add additional math control functions EXP, LOG, COS, SIN, ACOS, ASIN

  • Improvements to energy conservation in droplet evaporation

  • Correct order of H and HS (pseudo-pressure) calculation in BAROCLINIC_CORRECTION (code now achieves second-order temporal convergence for variable density flows)

  • Correct VEL_T orientation for synthetic eddy method and particle insertion

Inputs

  • RADIATIVE_FRACTION moved from RADI to REAC

Outputs

  • TURBULENCE RESOLUTION and SCALAR RESOLUTION have been removed from SLCF and DEVC output until proper handling of resolved TURBULENT KINETIC ENERGY is achieved "on the fly". For the time being, TKE and K_SGS must be output independently as discussed in the FDS User Guide (see section on A Posteriori Mesh Quality Metrics).

FDS 6.2.0 (Apr 14, 2015)

Species Mass Density Transport Overhaul

To address potential realizability violations in species mass fractions (realizability requires Y_i >=0 and sum_i Y_i = 1, for all i), we now solve transport equations for all Ns species and obtain the mass density, rho, from sum_i rhoY_i. This guarantees realizability provided rhoY_i >=0 (i.e., we enforce boundedness). An improved boundedness correction is employed that absorbs any errors in the most abundant species locally (the error absorbing species is not specified a priori).

General Enhancements/Bug Fixes

  • Corrected Deardorff turbulent viscosity at mesh edges, corners, and mirror boundaries.

  • Fix bug in DNS viscosity where previously only the background species molecular viscosity was being used.

  • Added TGA analysis feature whereby one can conduct a simulated thermogravimetric analysis by just adding a flag to the relevant SURF line.

  • Improvements to RESTART capability to increase reliability.

  • New version of RADCAL that includes updating the original RADCAL to Fortran 2008 and adds additional fuel species beyond the original methane.

  • Fix bug in Poisson solver for multi-mesh cylindrical coordinates.

  • Reduction in the size of MPI data exchanges to reduce the potential for MPI timeout errors.

  • Add ability to define a specified leakage location.

  • Add input file line location for namelist error messages.

  • The Windows version of FDS is compiled with Intel MPI, the Linux version is compiled with OpenMPI 1.8.4 and the Mac OSX version is compiled with OpenMPI 1.8.3 .

Inputs

  • SPECIFIC_SOURCE_TERM changed to INTERNAL_HEAT_SOURCE.

  • N_LAYER_CELLS_MAX now user definable.

  • HEAT_TRANSFER_COEFFICIENT_BACK added.

  • GRAVITATIONAL_SETTLING added to allow separate control of gas-phase settling from solid-phase deposition.

  • PR_GAS added as SPEC input to allow user to specify molecular Prandtl number of the gas (default 0.7).

Outputs

  • Can specify a SPEC_ID for wall flow quantities.

  • DIFFUSIVITY, MASS FLUX WALL CELL, and MACH NUMBER outputs added.

  • MLR_TOTAL added to hrr file (replaces BURN_RATE).

FDS 6.1.2 (Oct 1, 2014)

  • Set CHECK_VN=.TRUE. by default (Von Neumann stability check), helps improve stability.

  • Use Intel MPI for Windows version of FDS.

  • Remove OpenMP flags from MPI builds.

  • Make SECOND_ORDER_INTERPOLATED_BOUNDARY mass conserving.

  • Add +/- versions of VOLUME FLOW WALL, MASS FLOW WALL, and HEAT FLOW WALL output quantities.

  • Remove hard coded limit on the number of SPEC inputs, note other inputs with SPEC_ID such as SURF and REAC are still limited to 20 species.

  • Add RAMP_T_I to specify an initial, in-depth, surface temperature profile.

FDS 6.1.1 (Jul 21, 2014)

  • Speed up processing of particles and droplets.

  • Fix bug in 'RADIATIVE HEAT FLUX GAS' output.

  • Add 'NUMBER OF PARTICLES' and 'CPU TIME PER STEP' as DEVC output.

  • Fix radiation heat flux to walls that align with mesh boundary.

  • Add relaxation to HVAC pressure boundary condition.

  • Allow for creation of new primitive species based on a predefined species using the keyword PRIMITIVE.

FDS 6.1.0 (May 29, 2014)

Parallel Computing

  • Release OpenMP version as the default.

  • Include additional bundled libraries for MPI Linux versions of FDS.

  • Use MPI_IN_PLACE in MPI_ALLGATHERV calls.

Species and Combustion

  • Fix ability to define a SPEC with a formula and have chemistry picked up by SIMPLE CHEMISTRY.

  • Additional predefined gas and liquid species added

  • Can now define THIRD_BODY reactions (i.e., reactions like A + B + M -> C + M)

Boundary Conditions

  • Fix vent splitting over meshes for HVAC.

  • Add CONVERT_VOLUME_TO_MASS to SURF for VEL type boundary conditions.

  • Change VOLUME_FLUX to VOLUME_FLOW to be consistent with HVAC.

  • Overhauled treatment of mass flux at solid boundaries.

  • Disallow velocity boundary condition for thin obstructions.

  • MAX_LEAK_PATHS may be set by the user

  • The default BACKING is changed from 'VOID' to 'EXPOSED'

Particles

  • For solid particles with more than one ORIENTATION vector, the radiation heat flux is computed as an integrated average over the appropriate fraction of the surface. Previously, the heat flux was computed to a plate normal to the ORIENTATION vector.

Output

  • Add MASS FLOW WALL, HEAT FLOW WALL, and VOLUME FLOW WALL as SOLID_PHASE_OUTPUT device quantities.

  • Add SPEC_ID to duct output quantities

  • Add QUANTITY_RANGE to DEVC for limiting integration when STATISTICS is set

  • Add AMPUA_Z, CPUA_Z, MPUA_Z, and MPUV_Z output quantities.

FDS 6.0.1 (Dec 10, 2013)

  • The MPI version of FDS is now compiled with Open MPI 1.6.5.

  • Fixes related to lumped species definitions.

  • Use FLUSH statement instead of CLOSE/OPEN in dump routines.

  • Add ability to modify most thermophysical properties for user-defined mixtures.

  • Fix bug in particle tracking algorithm.

  • Fix initialization of back wall temperature.

  • Add inlet velocity profile functionality via RAMP_V_X, etc., on SURF line.

  • Include FDS User, Technical, Verification, Validation, and Configuration guides in bundle.

FDS 6.0.0 (Nov 19, 2013)

Hydrodynamics and Turbulence

  • Conservative, total variation diminishing (TVD) scalar transport is implemented: Superbee (LES default) and CHARM (DNS default). These schemes prevent over-shoots and under-shoots in species concentrations and temperature.

  • Improved models for the turbulent viscosity are implemented: Deardorff (default), Dynamic Smagorinsky, and Vreman. These models provide more dynamic range to the flow field for coarse resolution and converge to the correct solution at fine resolution.

  • The conservative form of the sensible enthalpy equation is satisfied by construction in the FDS 6 formulation, eliminating temperature anomalies and energy conservation errors due to numerical mixing.

  • The baroclinic torque is included by default.

  • Improvements are made to the wall functions for momentum and heat flux. An optional wall heat flux model accounts for variable Prandtl number fluids.

  • Jarrin's Synthetic Eddy Method (SEM) is implemented for turbulent boundary conditions at vents.

Species and Combustion

  • Custom species mixtures ("lumped species") can be defined on the SPEC line.

  • Turbulent combustion is handled with a new partially-stirred batch reactor model. At the subgrid level, species exist in one of two states: unmixed or mixed. The degree of mixing evolves over the FDS time step by the interaction by exchange with the mean (IEM) mixing model. Chemical kinetics may be considered infinitely fast or obey an Arrhenius rate law.

  • It is now possible to transport, produce, and consume toxins such as CO and soot. Chemical mechanisms must be provided by the user and may include reversible reactions.

  • It is now possible to deposit aerosol species onto surfaces.

  • Increased number of predefined species that now include liquid properties.

Lagrangian Particles

  • Moving particles can be assigned a SURF_ID.

  • More alternatives and user-defined option are available for the liquid droplet size distribution.

  • The user can specify the radiative properties of the liquid droplets.

  • Drag effects of thin porous media (i.e., window screens) can be simulated using planes of particles.

Solid Phase Heat Transfer and Pyrolysis

  • The basic 1-D heat transfer and pyrolysis model for solid surfaces remains the same, but there has been a change in several of the input parameters to expand functionality and readability of the input file.

  • More attention should be paid on the specification of MATL densities for the pyrolysis model. Unlike FDS 5, now the pyrolysis model tries to determine if the surface should shrink or swell, based on the MATL densities.

HVAC

  • Filters, louvered vents, and heating/cooling capability has been added for HVAC systems.

  • HVAC now functional with MPI.

Radiation

  • !RadCal database extended to include additional fuel species.

  • It is now possible to assign a !RadCal species to a SPEC.

  • In cells with heat release, the emission term is based on a corrected sigma T^4^ such that when this term is integrated over the flame volume the specified radiative fraction (default 0.3) is recovered. This differs from FDS 5 and earlier where the radiative fraction times the heat release rate is applied locally as the emission term.

Multi-mesh Computations

  • By default, FDS now iterates pressure and velocity at mesh and solid boundaries. The error tolerance and maximum number of iterations may be set by the user.

Control functions

  • CTRL functions have been extended to include math operations.

  • The evaluation of RAMPs and DEVCs can be stopped, freezing their value, based upon the activation of a device or control function.

Devices and Output

  • Multiple pipe networks can be specified for sprinklers for reduction of flow rate based on the number of operating heads.

  • The numerical value of a control function can be output with a DEVC.

  • A line of devices can be specified using a number of POINTS on one DEVC line.

  • Statistical outputs for RMS, covariance, and correlation coefficient are available.

FDS 5.5 (April 6, 2010)

  • Restoration of the baroclinic torque term in the momentum equation, by default (removed in 5.5.3)

  • Secondary breakup model for droplets (simplified version of WAVE model by Reitz 1987)

  • Ability to have a RAMP use a DEVC for the independent variable by the keyword DEVC_ID on RAMP

  • Built-in thermophysical properties for a number of liquids (water and some common fuels)

  • Expanded number of gases with built-in thermophysical properties

  • Expanded set of droplet output quantities from PDPA devices

  • RAMPs and TAUs for EXTERNAL_FLUX on SURF

  • RAMP_PART and TAU_PART on SURF to control PARTICLE_MASS_FLUX

  • Use of a SURF line to describe Lagrangian particles

FDS 5.4 (Sep 1, 2009)

  • Pyrolysis model for solid materials has changed. The most important change is the definition of REFERENCE_TEMPERATURE and the elimination of REFERENCE_RATE. See the FDS User's Guide for more details.

  • Werner-Wengle wall model, a better description of the velocity boundary condition.

  • OpenMP parallelization option. This will allow you to use multiple cores/processors on a single computer to process a single mesh case, or when combined with MPI, will allow each mesh on each computer to exploit the multiple cores/processors.

  • ORIFICE_DIAMETER has been added to PROP inputs to provide a simple way to set droplet velocity. This is an alternative to specifying DROPLET_VELOCITY.

  • Thermally-Induced Electrical Failure (THIEF) model added to predict damage to electrical cables.

FDS 5.3 (Jan 30, 2009)

  • New output quantity: Fractional Effective Dose (FED) by Purser.

  • TIME INTEGRAL statistics is available for device outputs.

  • Yields of any explicitly-defined (via the SPEC line) gas species can be specified on the MATL lines using the new parameter NU_GAS.

  • The user can specify how the sprinkler pipe pressure depends on the number of open nozzles. The flow rate, droplet speed and median diameter are updated correspondingly.

  • The logical keyword DRY has been added to DEVC. When using the mixture fraction and specifying either MASS FRACTION or VOLUME FRACTION, use of DRY will give that fraction minus water vapor (i.e. give an output like a typical gas analyzer).

  • A Phase Doppler Particle Analysis (PDPA) device has been defined for detailed measurements of droplet sprays.

  • A new namelist group called MULT (short for multiplier) allows you to multiply OBSTructions and MESHes easily without having to retype the input lines over and over.

  • A new parameter called BULK_DENSITY has been added to the OBST namelist group to indicate more easily the total combustible mass within an OBSTruction that can BURN_AWAY.

  • Pressure ZONEs can now be opened, and sealed compartments can become unsealed via an OPEN boundary.

  • The output quantity that was once called 'soot density' and the newer version, QUANTITY='DENSITY', SPEC_ID='soot', is now in units of kg/m^3.

  • Device (DEVC) output units can be changed via a CONVERSION_FACTOR.

FDS 5.2 (Aug 1, 2008)

  • A simple "Eddy Dissipation" model is added to predict the mixing time of fuel and oxygen. Previous versions of FDS used the time step, which was tied to the flow velocity via the CFL criterion. The eddy dissipation model ties the mixing time to the turbulent diffusion coefficient, which is ultimately related to the eddy viscosity of the Smagorinsky form of LES. The eddy dissipation concept is based on scaling arguments and involves an empirical coefficient which has been determined by comparing calculations to classical fire plume experiments and correlations.

  • The names of the output quantities have changed, but the old names are still acceptable. The idea is to use parameters like SPEC_ID and PART_ID in conjunction with QUANTITY's like 'MASS FRACTION' and 'VOLUME FRACTION.' Details are in the User's Guide. Also, the underscores in QUANTITY names are no longer needed.

  • The default number of droplets introduced in a spray has increased to 5000 per second, and the insertion time has decreased to 0.01 s. The old values were 1000 and 0.05, respectively.

  • The mean beam length (PATH_LENGTH) for the radiation solver is no longer based on the size of the overall domain, but rather it defaults to 5 times the mesh cell size.

  • It is now possible to declare explicitly a surrogate species for smoke that can be visualized with SMOKE3D and a new output QUANTITY called VISIBILITY.

FDS 5.1 (Jan 8, 2008)

In simulations involving multiple meshes, FDS no longer allows the meshes to be arbitrarily connected. Starting with version 5.1, mesh resolution can only increase or decrease in integer increments. This change in functionality means that some input files that ran previously will no longer run.

Details of FDS Maintenance Releases

Version 6.1.2 - September 26, 2014 (SVN Revision 20564)

Version 6.1.1 - July 10, 2014 (SVN Revision 19882)

Version 6.1.0 - May 27, 2014 (SVN Revision 19412)

Version 6.0.1 - November 26, 2013 (SVN Revision 17534)

Version 6.0.0 - November 4, 2013 (SVN Revision 17279)

Version 5.5.3 - October 29, 2010 (SVN Revision 7031)

Version 5.5.2 - September 3, 2010 (SVN Revision 6706)

Version 5.5.1 - June 23, 2010 (SVN Revision 6385)

Version 5.5.0 - April 6, 2010 (SVN Revision 6006)

Version 5.4.3 - December 4, 2009 (SVN Revision 5210)

Version 5.4.2 - October 19, 2009 (SVN Revision 4957)

Version 5.4.1 - September 10, 2009 (SVN Revision 4697)

Version 5.4.0 - September 1, 2009 (SVN Revision 4629)

Version 5.3.1 - April 8, 2009 (SVN Revision 3729)

Version 5.3.0 - January 30, 2009 (SVN Revision 3193)

Version 5.2.5 - December 10, 2008 (SVN Revision 2828)

Version 5.2.4 - November 11, 2008 (SVN Revision 2651)

Version 5.2.3 - August 16, 2008 (SVN Revision 2514)

Version 5.2.2 - August 16, 2008 (SVN Revision 2510)

Version 5.2.1 - September 15, 2008 (SVN Revision 2376)

Version 5.2.0 - August 1, 2008 (SVN Revision 2087)

Version 5.1.6 - May 8, 2008 (SVN Revision 1673)

Version 5.1.5 - May 8, 2008 (SVN Revision 1650)

Version 5.1.4 - March 14, 2008 (SVN Revision 1437)

Version 5.1.3 - February 26, 2008 (SVN Revision 1373)

Version 5.1.2 - February 1, 2008 (SVN Revision 1262)

Version 5.1.1 - January 21, 2008 (SVN Revision 1217)

Version 5.1.0 - January 8, 2008 (SVN Revision 1162)

Version 5.0.3 - December 5, 2007 (SVN Revision 1069)

Version 5.0.2 - November 12, 2007 (SVN Revision 977)

Version 5.0.1 - October 12, 2007 (SVN Revision 836)

Version 5.0.0 - October 2, 2007 (SVN Revision 721)

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