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Global node coordinates values FSI-UDF

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Old   February 8, 2021, 05:58
Unhappy Global node coordinates values FSI-UDF
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Marcelo Ruiz
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Hello everybody,

I am traying to reproduce the motion of a fish in 2D. I am using the Macro DEFINE_GRID_MOTION(). I want to extract the initial coordinates of the fish, so that I can use it over all simulation. I other words, motion is defined by the initial position f(x_0,y_0,t). I have tried to code it in the same macro. Nevertheless, I have not succeed.

Could you please provide me any advice?
Which macro I can use to extract the Initial values and store it in a global variable matrix/array?


In the next code I try to extract the minimum and maximum coordinates before the deformation. However it did not work properly:

Code:
DEFINE_GRID_MOTION(motion, domain, dt, time, dtime)
{

	Thread* tf = DT_THREAD(dt);
	face_t f;
	Node* v;
	
	double xprev, yprev, hprev, d, h;
	int n;

	double x_max, x_min;
	x_max = -0.99e38;
	x_min = 0.99e38;
	
	begin_f_loop(f, tf) // I used this loop to find the maximum and minimum and maximum but it did not work
	{
		f_node_loop(f, tf,n)
		{
			v = F_NODE(f,tf, n);
			x_max = MAX(x_max, NODE_X(v));
			x_min = MIN(x_min, NODE_X(v));
		}
	}end_f_loop(f, tf)

#if RP_NODE
		x_max = PRF_GRHIGH1(x_max);
		x_min = PRF_GRHIGH1(x_min);
#endif
	SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));

	begin_f_loop(f, tf)
	{
		f_node_loop(f, tf, n)
		{
			v = F_NODE(f, tf, n);

			if (NODE_POS_NEED_UPDATE(v))
			{
				NODE_POS_UPDATED(v);
				
				if (CURRENT_TIME > 0.0)
				{ 
					xprev = NODE_X(v);
					yprev = NODE_Y(v);
					hprev = kinematics(xprev, PREVIOUS_TIME,x_max,x_min); //Function for the kinematics of fish
					d = yprev;
					h = kinematics(xprev, CURRENT_TIME, x_max, x_min); //Function for the kinematics of fish
					NODE_Y(v) = d+hprev-h;
				}
			}
		}
	}
	end_f_loop(f,tf)
}


Thank you for the advice,
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Old   February 27, 2021, 09:36
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Quote:
Originally Posted by CFDavatar View Post
Hello everybody,

I am traying to reproduce the motion of a fish in 2D. I am using the Macro DEFINE_GRID_MOTION(). I want to extract the initial coordinates of the fish, so that I can use it over all simulation. I other words, motion is defined by the initial position f(x_0,y_0,t). I have tried to code it in the same macro. Nevertheless, I have not succeed.

Could you please provide me any advice?
Which macro I can use to extract the Initial values and store it in a global variable matrix/array?


In the next code I try to extract the minimum and maximum coordinates before the deformation. However it did not work properly:

Code:
DEFINE_GRID_MOTION(motion, domain, dt, time, dtime)
{

	Thread* tf = DT_THREAD(dt);
	face_t f;
	Node* v;
	
	double xprev, yprev, hprev, d, h;
	int n;

	double x_max, x_min;
	x_max = -0.99e38;
	x_min = 0.99e38;
	
	begin_f_loop(f, tf) // I used this loop to find the maximum and minimum and maximum but it did not work
	{
		f_node_loop(f, tf,n)
		{
			v = F_NODE(f,tf, n);
			x_max = MAX(x_max, NODE_X(v));
			x_min = MIN(x_min, NODE_X(v));
		}
	}end_f_loop(f, tf)

#if RP_NODE
		x_max = PRF_GRHIGH1(x_max);
		x_min = PRF_GRHIGH1(x_min);
#endif
	SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));

	begin_f_loop(f, tf)
	{
		f_node_loop(f, tf, n)
		{
			v = F_NODE(f, tf, n);

			if (NODE_POS_NEED_UPDATE(v))
			{
				NODE_POS_UPDATED(v);
				
				if (CURRENT_TIME > 0.0)
				{ 
					xprev = NODE_X(v);
					yprev = NODE_Y(v);
					hprev = kinematics(xprev, PREVIOUS_TIME,x_max,x_min); //Function for the kinematics of fish
					d = yprev;
					h = kinematics(xprev, CURRENT_TIME, x_max, x_min); //Function for the kinematics of fish
					NODE_Y(v) = d+hprev-h;
				}
			}
		}
	}
	end_f_loop(f,tf)
}


Thank you for the advice,
Hi. I think this can help you:
after this code use N_UDMI(v,0) & N_UDMI(v,1) as the initial condition nodes for x and y. please search about DEFINE_ON_DEMAND macro. Don't forget that you must "Execute on Demand" it in fluent after Initialization.

DEFINE_ON_DEMAND(NODE_FIRST)
{
Domain *d= Get_Domain(1);
Thread *t=Lookup_Thread(d,ID);
face_t f;
Node *v;
int n;
FILE *fout;
real time=CURRENT_TIME;
thread_loop_f (t,d)
{
begin_f_loop(f,t)
{
f_node_loop(f,t,n)
{
v = F_NODE(f,t,n);
N_UDMI(v,0) = NODE_X(v);
N_UDMI(v,1) = NODE_Y(v);
}
}
}
end_f_loop (f,t)
}
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Old   October 26, 2021, 23:49
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Thomas Sprengeler
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Were you able to store the initial coordinates and make this work?
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Old   October 27, 2021, 10:25
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Marcelo Ruiz
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Quote:
Originally Posted by sprengeler View Post
Were you able to store the initial coordinates and make this work?
Hello, at the end I just kept the fish swiiming from a fixed reference coordinate system. You can try with etedalgara suggestion above
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Old   October 27, 2021, 12:27
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Thomas Sprengeler
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Quote:
Originally Posted by CFDavatar View Post
Hello, at the end I just kept the fish swiiming from a fixed reference coordinate system. You can try with etedalgara suggestion above
Is there a way to specify a fixed reference coordinate system in your UDF?
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