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 skarp July 7, 2007 09:02

Negative volume in mesh motion

Dear Friends

I was solving a moving mesh problem like check valve.y negative volume occurs reason?

ERROR #002100012 has occurred in subroutine cVolSec. Message: A negative ELEMENT volume has been detected. This is a fatal error and execution will be terminated. The location of the first negative volume is reported below. Volume : -0.4107E-13 | Location : ( -0.35156E-02, 0.36065E-01, -0.49511E-03)

 JH July 7, 2007 11:16

Re: Negative volume in mesh motion

Hello. That error is very common when you try to deform a domain. There is no easy answer. The first thing you may do is to identify the small mesh elements in your domain with volume negative (they are so small that were reverse like a t-shirt that you just take off...) try to use planes and volume regions (with "draw lines" active) to locate such elements. Once you know approximately the location, you may have to modify the mesh stiffness equation in order to get a better node displacement when deforming the mesh and check the new elements status (try a mesh stiffness equation: 1 [m^3 s^-1]/Wall Distance; or 1 [m^5 s^-1]/Volume of Finite Volumes). You also may check the surface displacement after deformation, it may be doing a impossible movement. I hope this lines gives you an idea. Good Luck.

 skarp July 9, 2007 00:24

Re: Negative volume in mesh motion

Thanks dude

Can u tell me why negative volume occurs ?

 skarp July 10, 2007 23:53

Re: Negative volume in mesh motion

I have find out the reason for negative volume

F=ma m-mass of the ball,a=acceleration of ball F=force of the flow.

since i have specified only the force of flow and no other opposing force like spring or gravity force.My ball is hiting the wall in first iteration itself and stops saying negative volume.In post the wall bulges.

Can anyone tell how to stop the ball before it reaches the wall.

 Glenn Horrocks July 11, 2007 18:31

Re: Negative volume in mesh motion

Hi,

Negative volume errors occur when an element is turned inside out due to the mesh motion.

You need to check your motion equations and possibly use a finer timestep.

Glenn Horrocks

 SKARP July 11, 2007 23:51

Re: Negative volume in mesh motion

Hi

My problems is I have flow force only and no other force opposing the flow force.

I want to stop the ball before the ball goes and hit the wall. Is there any eqn to resist the motion of the ball only to a certain displacement.

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