Convection length scale of shrinking particle

[r-broek]

Dear developers,

Which length scale is used for computing the convective heat transfer to/from a cylindrical particle that is shrinking? Is it the initial diameter of the particle specified by the THINKNESS argument, or is the evolving particle diameter used? Also, in case CONVECTION_LENGTH_SCALE is specified on the SURF line, does this value remain constant or is it scaled to account for shrinkage?

[mcgratta]

The length scale of a shrinking particle is the evolving diameter; Even if specified, the model uses the current diameter.

[r-broek]

I see. Do you happen to know if there is a straightforward method to access the initial particle diameter in Wall.f90 for every time step?

[mcgratta]

Yes, SF%CONV_LENGTH which is short for SURFACE(N)%CONV_LENGTH. In read.f90

   ! Set convection length scale automatically for spheres. Set to 1 m for everything else.

   IF (SF%CONV_LENGTH<0._EB) THEN
      SELECT CASE(SF%GEOMETRY)
         CASE(SURF_SPHERICAL)
            SF%CONV_LENGTH = 2._EB*(SF%INNER_RADIUS+SF%THICKNESS)
         CASE(SURF_CYLINDRICAL)
            SF%CONV_LENGTH = 2._EB*SF%THICKNESS
         CASE DEFAULT
            SF%CONV_LENGTH = 1._EB
      END SELECT
   ENDIF

The statement IF (SF%CONV_LENGTH<0._EB) THEN means "if the user has not specified a length scale, then ..." and THICKNESS is equivalent to radius for a cylindrical surface.

[r-broek]

Thanks a lot for your help