Changeset 4585 for palm/trunk

Timestamp:

Jun 30, 2020 3:05:20 PM (4 years ago)

Author:

suehring

Message:

Limit logarithmically interpolated particle speed to the velocity component at the first prognostic grid point (since no stability corrected interpolation is employed the particle speed could be overestimated in unstable conditions violating the CFL restriction made for particle speeds)

File:

• palm/trunk/SOURCE/lagrangian_particle_model_mod.f90 (modified) (3 diffs)

palm/trunk/SOURCE/lagrangian_particle_model_mod.f90

@@ -25 +25 @@
 ! -----------------
 ! $Id$
+! Limit logarithmically interpolated particle speed to the velocity component
+! at the first prognostic grid point (since no stability corrected interpolation
+! is employed the particle speed could be overestimated in unstable conditions).
+! 
+! 4546 2020-05-24 12:16:41Z raasch
 ! Variables iran and iran_part completely removed, added I/O of parallel random numbers to restart
 ! file
@@ -3717 +3722 @@
 !--                as sensitivity studies revealed no significant effect of
 !--                using the neutral solution also for un/stable situations.
+!--                However, as the stability correction is missing the particle
+!--                speed may be overestimated compared to the velocity component
+!--                at the first prognostic grid point. Hence, the particle speed
+!--                is limited.
                    u_int(n) = -usws_int / ( us_int * kappa + 1E-10_wp )        &
                                * log_z_z0_int - u_gtrans
+
+                   u_int(n) = SIGN( MIN( ABS( u_int(n) ), ABS( u(k_wall+1,jp,ip) ) ), u_int(n) )
+
                 ENDIF
 !
@@ -3812 +3824 @@
 !--                as sensitivity studies revealed no significant effect of
 !--                using the neutral solution also for un/stable situations.
+!--                However, as the stability correction is missing the particle
+!--                speed may be overestimated compared to the velocity component
+!--                at the first prognostic grid point. Hence, the particle speed
+!--                is limited.
                    v_int(n) = -vsws_int / ( us_int * kappa + 1E-10_wp )        &
                             * log_z_z0_int - v_gtrans
+
+                   v_int(n) = SIGN( MIN( ABS( v_int(n) ), ABS( v(k_wall+1,jp,ip) ) ), v_int(n) )
 
                 ENDIF