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6DOF Dynamic Mesh Problem with Overset Meshing - Weird velocity contour

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Old   December 5, 2017, 02:12
Default 6DOF Dynamic Mesh Problem with Overset Meshing - Weird velocity contour
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Caster Troy
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Hi everybody,

I'm trying to make a simple falling ball simulation in 2D domain using overset meshing. Here is the grid;

Initial Grid

Upper and lower ends of the background mesh are walls, left end is velocity inlet with 5 m/s of air inflow and right end is pressure outlet with 0 Pa gauge pressure. I obtained steady solution first and here is the velocity contours;

Initial (steady) velocity contours

And here is dynamic mesh settings;

Dyn. mesh settings

Two dyn. mesh zones:
1. Wall of the ball with passive disabled
2. Component zone of ball with passive enabled

After 38 time steps here is the velocity contours;




As you can see solver does weird things when dynamic mesh enabled. I calculates the velocity at wall as maximum, instead of applying no-slip condition. Any help is appreciated. Here is the UDF I used, I defined gravity internally;

Code:
#include "udf.h"
#include "math.h"


DEFINE_SDOF_PROPERTIES(Ball_free_fall, prop, dt, time, dtime)
{
       prop[SDOF_MASS] = 0.5;
       prop[SDOF_ZERO_TRANS_X] = FALSE; 
       prop[SDOF_ZERO_TRANS_Y] = FALSE;
       prop[SDOF_ZERO_TRANS_Z] = TRUE;
       prop[SDOF_ZERO_ROT_X] = TRUE;
       prop[SDOF_ZERO_ROT_Y] = TRUE;
       prop[SDOF_ZERO_ROT_Z] = TRUE;
}

Last edited by Caster_Troy; December 6, 2017 at 08:52. Reason: wrong link
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Old   December 7, 2017, 06:19
Default sixdof
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jingyuanli
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Quote:
Originally Posted by Caster_Troy View Post
Hi everybody,

I'm trying to make a simple falling ball simulation in 2D domain using overset meshing. Here is the grid;

Initial Grid

Upper and lower ends of the background mesh are walls, left end is velocity inlet with 5 m/s of air inflow and right end is pressure outlet with 0 Pa gauge pressure. I obtained steady solution first and here is the velocity contours;

Initial (steady) velocity contours

And here is dynamic mesh settings;

Dyn. mesh settings

Two dyn. mesh zones:
1. Wall of the ball with passive disabled
2. Component zone of ball with passive enabled

After 38 time steps here is the velocity contours;




As you can see solver does weird things when dynamic mesh enabled. I calculates the velocity at wall as maximum, instead of applying no-slip condition. Any help is appreciated. Here is the UDF I used, I defined gravity internally;

Code:
#include "udf.h"
#include "math.h"


DEFINE_SDOF_PROPERTIES(Ball_free_fall, prop, dt, time, dtime)
{
       prop[SDOF_MASS] = 0.5;
       prop[SDOF_ZERO_TRANS_X] = FALSE; 
       prop[SDOF_ZERO_TRANS_Y] = FALSE;
       prop[SDOF_ZERO_TRANS_Z] = TRUE;
       prop[SDOF_ZERO_ROT_X] = TRUE;
       prop[SDOF_ZERO_ROT_Y] = TRUE;
       prop[SDOF_ZERO_ROT_Z] = TRUE;
}


hi Caster
You know how to implement a sphere in the water rising at a constant speed?
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