Solution is diverging (Only the continuity equation)
 

Hii, I'm trying to simulate a sloshing problem in which I'm applying Acos(w*t) velocity in the x-direction at the bottom surface of the cylindrical tank having water at the base and the top is filled with air and open to the atmosphere. For this, I applied dynamic mesh (Layering option ) only by using UDF as shown below. the problem is my solution is diverging especially the continuity equation. Can anyone suggest me what should I do?

UDF:
#include "udf.h"
static real velx =0.0;
DEFINE_CG_MOTION(bottom,dt,vel,omega,time,dtime)
{
NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);
velx =0.012566*cos(6.28*time);
vel[0] = velx;
Message ("time= %f, vel[0]=%f\n", time, vel[0]);
}

Relaxation factor:
Pressure-0.6
Density-0.8
Body force-0.5
momentum-0.4
volume fraction-0.6

Suggest me something.

Thank you.