[Rakkiran]

Dear All,

I have to perform overset mesh simulation with 2 degrees of freedom (DOF) motion. But the mesh motion is wrong when I run preview mesh motion. However, when I run a 1 DOF motion the meshes are working fine.

UDF am using is as follows for 2 DOF and the images are attached of mesh for reference. 1 DOF work good but the deviation of wing from the XZ plane while I am trying to move about the wing tip and about the wing chord it is moving in some different direction.

I have given the position of center of gravity in dynamic mesh is the midpoint of wing root(one side of the rectangular wing)

#include "udf.h"

DEFINE_CG_MOTION(wing_motion, dt, vel, omega, time, dtime)
{
real pi, f, phi_m, phi_0, alpha_m, phi, alpha, delta, phi_alpha, d_phi, d_alpha, d_delta, C_p , C_a, degToRad;

pi = 3.14159265359;
degToRad = pi/180;
f = 0.1; // flapping frequency
C_p = 0.8;
C_a = 2.7;
phi_m = 75*pi/180; // sweep angle amplitude
phi_0 = 0*pi/180; // sweep angle offset
alpha_m = 45 * pi/180; // inclination angle amplitude
phi_alpha = 0 * pi/180 ; // inclination angle phase shift (20)

// Angular displacement
phi = (phi_0 + (phi_m / asin(C_p) * asin(C_p * cos(2 * pi * f * time))))*180/pi;

alpha = ((pi / 2 - alpha_m) / tanh(C_a) * tanh(C_a * sin(2 * pi * f * time - phi_alpha)))* 180/pi;
delta = 0.0;

// Angular velocities
d_phi = -(2 * pi * C_p * f * phi_m * sin(2 * pi * f * time)) / (asin(C_p) * sqrt(1 - C_p*C_p * cos(2 * pi * f * time)*cos(2 * pi * f * time)));

d_alpha = (2 * pi * C_a * (pi/2-alpha_m) * f * cos(2 * pi * f * time-phi_alpha)) / (cosh(C_a * sin(2 * pi * f * time-phi_alpha))*cosh(C_a * sin(2 * pi * f * time-phi_alpha)) * tanh(C_a)) ;


vel[0] = 0.0;
vel[1] = 0.0;
vel[2] = 0.0;

omega[0] = d_alpha;
omega[1] = d_phi;
omega[2] = 0.0;
}


Also I wish to learn how the zone motion and things related to overset meshes. Kindly suggest me some resources to start (I have already read through fluent user guide but I did not understand much).


Thanks in Advance.