DEFINE_ADJUST UDF for the parallel solver
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Additional code is sometimes required to make a UDF work in parallel. One example is a DEFINE_ADJUST macro for calculating a mass weighted average or area weighted average of one or more flow quantities on a boundary thread. The use of the global sum operator, described in Section 3.12 of the Fluent 6 UDF guide is required, but more modifications are needed. Consider the following DEFINE ADJUST function to calculate the area average pressure on a face:
DEFINE_ADJUST(face_av,domain) { int surface_thread_id= 7 ; real total_area=0.0; real total_pres_a=0.0; Thread* thread; face_t face; real area[ND_ND]; thread = Lookup_Thread(domain,surface_thread_id); begin_f_loop(face,thread) { F_AREA(area,face,thread); total_area += NV_MAG(area); total_pres_a += NV_MAG(area)*F_P(face,thread); } end_f_loop(face,thread) Message("Average pressure on Surface %d is %f Pan",surface_thread_id,(total_pres_a/total_area)); } An example of how to make this function work in parallel is shown in the Resolution field. A cleaner, more recent version of this example can be found in the FLUENT 6.3 UDF Manual http://www.fluentusers.com/fluent6326/doc/ori/html/udf/node218.htmDEFINE_ADJUST(face_av,domain)http://www.fluentusers.com/fluent6326/doc/ori/html/udf/node218.htmDEFINE_ADJUST(face_av,domain) { int surface_thread_id= 7 ; real total_area=0.0; real total_pres_a=0.0; #if !RP_HOST Thread* thread; /* these variables are only defined on "calculating" processes (Nodes & serial) face_t face; real area[ND_ND]; #endif /* !RP_HOST */ host_to_node_int_1(surface_thread_id); /* Does nothing in SERIAL */ #if RP_NODE Message("nNode %d is calculating on thread # %dn",myid,surface_thread_id); #endif /* RP_NODE */ #if !RP_HOST /* SERIAL or NODE */ thread = Lookup_Thread(domain,surface_thread_id); begin_f_loop(face,thread) # if RP_NODE if (I_AM_NODE_SAME_P(F_PART(f,thread))) /* Check to see if face is allocated to this partition (Actually C0 of face) */ # endif { F_AREA(area,face,thread); total_area += NV_MAG(area); total_pres_a += NV_MAG(area)*F_P(face,thread); } end_f_loop(face,thread) # if RP_NODE Message("Total Area Before Summing %fn",total_area); Message("Total Normal Force Before Summing %fn",total_pres_a); total_area = PRF_GRSUM1(total_area); total_pres_a = PRF_GRSUM1(total_pres_a); # endif /* RP_NODE */ #endif /* !RP_HOST */ node_to_host_real_2(total_area,total_pres_a); /* Does nothing in SERIAL */ Message("Total Area After Summing: %fn",total_area); Message("Total Normal Force After Summing %fn",total_pres_a); Message("Average pressure on Surface %d is %f Pan",surface_thread_id,(total_pres_a/total_area)); } |
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