Added flag to ensure that mac velocity not sampled for init or restar…

…t in Actuator (#889)

Co-authored-by: Michael Kuhn <[email protected]>

amr-wind/wind_energy/actuator/Actuator.cpp

@@ -188,7 +188,9 @@ void Actuator::update_positions()
     m_container->update_positions();
 
     // Sample velocities at the new locations
-    if (m_sample_nmhalf) {
+    if (m_sample_nmhalf &&
+        (m_sim.time().current_time() > m_sim.time().start_time())) {
+        // Avoid using mac velocities if at init or restart
         const auto& umac = m_sim.repo().get_field("u_mac");
         const auto& vmac = m_sim.repo().get_field("v_mac");
         const auto& wmac = m_sim.repo().get_field("w_mac");