Grid motion with UDF
Hi to everyone !
I am trying to simulate a moving grid using Fluent dynamic mesh. I have created a structured quad mesh and used layering as a dynamic meshing technique. The grid motion is set from the Dynamic mesh zones Create/Edit menu as User-defined and the UDF supplied is the following : #include"udf.h" DEFINE_GRID_MOTION(motion,domain,dt,time,dtime) { Thread *tf = DT_THREAD(dt); face_t f; Node *v; real NV_VEC(axis); real displ; int n; displ=-17.2*dtime; // grid displacement NV_D(axis, =, 0.0, 1.0, 0.0); begin_f_loop(f,tf) { f_node_loop(f,tf,n) { v = F_NODE(f,tf,n); /* update node if the current node has not been previously visited when looping through previous faces */ if ( NODE_POS_NEED_UPDATE (v)) { /* indicate that node position has been update so that it's not updated more than once */ NODE_POS_UPDATED(v); NV_V_VS(NODE_COORD(v), =, NODE_COORD(v), +, axis,*,displ); } } } end_f_loop(f,tf); } This simple UDF was based on the DEFINE_GRID_MOTION example in the fluent 12 UDF manual. What it actually does is that it displaces the mesh on the Y-axis (axis : 0, 1,0), by -17.2 * time_step (17.2 is the mesh velocity). The UDF compiles and loads and the mesh moves and new elements are generated/merged at stationary zones. But my problem is that when I calculate the mesh velocity, by simply finding its displacement between two times, the mesh velocity is substantially lower than the one set in the UDF (~10m/sec instead of 17.2m/sec) ! What I am missing here? Any ideas are welcome. Thank you in advance. |
I am posting myself because I found the cause of the problem. The problem was not the UDF at all, but the wrong time intervals for the extraction of the output data files.
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can you help me
:)have you, sir , tutorials a bout this domain?
my boreblem is to similate fllaping NACA0012 in 2D of tow degree of 2 freedom. I try to do it with moving gird mesh , but i cant do it :(. please email: bouakkaz10@yagoo.fr |
Define_grid_motion
hello everyone.
does anyone know how to write define grid motion udf with cylindrical coordinates? thanks in advance. |
tutorial
hello dear
can u give me a tutorial about grid motion dynamic mesh? if u have an address link please send me. thanks |
Quote:
hello sir Do you know the meaning of the bottom commands? NODE_POS_UPDATED(v); NODE_COORD(v) NV_D(axis, =, 0.0, 1.0, 0.0); please help me thanks |
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