[pilakin]

I have a moving layering mesh you can see in the picture. The wall on the right is a rigid body and is moving to the left. Now comes an area where the domain becomes thinner. The moving wall stays the same length though. You can see the result of this in the second pitcure. Is there a way to shorten the length of the moving wall with UDFs or can you think of any work around?

[upeksa]

You must first find the relation between the lateral displacement of your case and the length of the right boundary.

Then you have to update as well the displacement of the nodes in that right boundary.

Cheers

[pilakin]

Originally Posted by upeksa

You must first find the relation between the lateral displacement of your case and the length of the right boundary.

Then you have to update as well the displacement of the nodes in that right boundary.

Cheers

the length of the wall would depend on the height of the circlish left area. but my main problem is, I don't know how to displace the nodes in the wall. I was using an UDF with define_cg_motion to move the wall and defined the wall as a rigid body.
right now I'm playing around with the define_grid_motion UDF macro as this seems to be the way to go about this problem.

[pilakin]

I solved the problem. Here's the code I developed. It might help you if you're having a similar issue.

#include "udf.h"
#include "dynamesh_tools.h"

#define CELL_HEIGHT 0.0032
#define MAIN_ZONE_LENGTH 0.71
#define SIMULATION_DURATION 500
#define CYLINDER_LENGTH 0.66
#define RADIUS 0.165
#define NOZZLE_LENGTH 0.03
#define TANK_LENGTH 0.792



DEFINE_GRID_MOTION(wall50motion,domain,dt,time,dtime)
{
	Thread *currentThread = DT_THREAD(dt);
	face_t currentFace;
	Node *currentNode;
	real NV_VEC(Xaxis);
	real NV_VEC(Yaxis);
	real wallMovingXspeed;
	int nodeID;
	real Xc;
	real YpbCurrent;
	real YpbAfter;
	real XpbCurrent;
	real XpbAfter;
	real XpbAtShrinkingStartTime;
	real shrinkingStartTime;
	real NodeYcurrent;
	real NodeYafter;
	
	
	
	int i = 0;
	Xc = RADIUS + NOZZLE_LENGTH;
	XpbAtShrinkingStartTime = (TANK_LENGTH - CYLINDER_LENGTH) / 2 + NOZZLE_LENGTH;
	wallMovingXspeed = -(MAIN_ZONE_LENGTH-CELL_HEIGHT)/SIMULATION_DURATION;
	shrinkingStartTime = CYLINDER_LENGTH / (-wallMovingXspeed);
	NV_D(Xaxis, =, 1.0, 0.0, 0.0);
	NV_D(Yaxis, =, 0.0, 1.0, 0.0);
	
	if (CURRENT_TIME >= 0 && CURRENT_TIME < shrinkingStartTime)
	{
		begin_f_loop(currentFace,currentThread)
		{
			f_node_loop(currentFace,currentThread,nodeID)
			{
				currentNode = F_NODE(currentFace,currentThread,nodeID); 
				if ( NODE_POS_NEED_UPDATE (currentNode))
				{
					NODE_POS_UPDATED(currentNode);
					NV_V_VS(NODE_COORD(currentNode), =, NODE_COORD(currentNode), +, Xaxis,*,wallMovingXspeed*dtime);
				}
			}
		}
		end_f_loop(currentFace,currentThread);
	}
	else if (CURRENT_TIME >= shrinkingStartTime && CURRENT_TIME < SIMULATION_DURATION)
	{
		begin_f_loop(currentFace,currentThread)
		{
			i++;
			f_node_loop(currentFace,currentThread,nodeID)
			{
				currentNode = F_NODE(currentFace,currentThread,nodeID); 
				if ( NODE_POS_NEED_UPDATE (currentNode))
				{
					NODE_POS_UPDATED(currentNode);;
					NV_V_VS(NODE_COORD(currentNode), =, NODE_COORD(currentNode), +, Xaxis,*,wallMovingXspeed*dtime);
					XpbCurrent = XpbAtShrinkingStartTime + wallMovingXspeed * (CURRENT_TIME-shrinkingStartTime);
					XpbAfter = XpbAtShrinkingStartTime + wallMovingXspeed * (CURRENT_TIME+dtime-shrinkingStartTime);
					YpbCurrent = RADIUS * sin(acos((Xc-XpbCurrent)/RADIUS));
					YpbAfter = RADIUS * sin(acos((Xc-XpbAfter)/RADIUS));
					NodeYcurrent = NODE_Y(currentNode);
					NodeYafter = NodeYcurrent/YpbCurrent*YpbAfter;
					NV_V_VS(NODE_COORD(currentNode), =, NODE_COORD(currentNode), +, Yaxis,*,NodeYafter-NodeYcurrent);
				}
			}
		}
		end_f_loop(currentFace,currentThread);
	}
}