# Segmentation Violation

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 February 20, 2012, 12:56 Segmentation Violation #1 New Member   Peter Join Date: Jan 2012 Posts: 29 Rep Power: 5 Hello all, I am currently trying to run a simple simulation on Fluent - a cylinder oscillating in constant velocity field. The udf I am using is - #include"udf.h" /* this function defines velocity of center of gravity for pure plunging motion*/ /* Plunging motion equation is z(t)=h*sin(2*pi*f*t) */ DEFINE_CG_MOTION(plung,dt,vel,omega,time,dtime) { Thread*t; face_t*f; /*reset velocities */ NV_S(vel,=,0.0); NV_S(omega,=,0.0); if(!Data_Valid_P()) return; /* Get the thread pointer for which this motion is defined */ t=DT_THREAD(dt); /* vel[1] is the vertical plunging velocity */ vel[1] = 0.5*sin(time); } The cylinder is of frontal area 1m. The fluid medium is of density 150kg/m3 Viscosity 1kg/m-s I have checked mesh, it runs with the cylinder oscillating and produces no errors. When I run the code, with the cylinder in constant velocity I get the following error - Updating solution at time level N... done. Updating mesh at time level N... done. iter continuity x-velocity y-velocity time/iter No error handler available Error: FLUENT received a fatal signal (SEGMENTATION VIOLATION). Error Object: () If anyone can advise of a solution or something for me to try I would be extremely grateful. Regards, Peter

 February 21, 2012, 11:20 #2 New Member   Peter Join Date: Jan 2012 Posts: 29 Rep Power: 5 Anyone have any ideas? Thanks again.

 March 16, 2012, 01:41 #3 Member   Join Date: Mar 2011 Posts: 50 Rep Power: 6 there are several problems in this udf. I will address one critical one. You are using a grid motion udf and you have written equation in terms of the nodes of the mesh. if 2d: begin_f_loop(f,thread,n) f_node_loop(f,thread,n); if(NODE_POS_NEED_UPDATE(v) NODE_POS_UPDATED(v); vel[0] = NODE_Y(v)*sin(2*pi*time); for time you need to get flow time. there is a macro for that. If your thread were a straight line of nodes, I am moving the nodes in sinusoidal form . Therr are other problems in udf. I am busy. Hope this helps.

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