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Vinay Morabad February 5, 2008 23:47

Regarding Negative volume detected in Dynamic mesh
Hello, currently i am working on Dynamic mesh of Rotary Engine(Wankel Engine). After compiling the user defined function(UDF) in Fluent 6.3 and setting all the dynamic parameters and dynamic zones paramaters when i check the dynamic mesh motion it is giving me the message of NEGATIVE VOLUME DETECTED .i.e. dynamic mesh update failed. Even after this i varied many parameters and also i refined the mesh quality still it is giving the same error message.


Thanks and Regards Vinay

mAx February 6, 2008 02:33

Re: Regarding Negative volume detected in Dynamic
it gives you this message before or after iterating (or checking motion)? I assume it's given after checking the motion. Try to reduce your time step.

Vinay Morabad February 6, 2008 03:56

Re: Regarding Negative volume detected in Dynamic
Thanks for your reply, I tried this option with various steps like reducing the time step as well as increasing the time step. But still i am getting the same error. What are the reasons for negative volume error. vinay

mAx February 6, 2008 04:05

Re: Regarding Negative volume detected in Dynamic
in my cases, I got negative volume, when dynamic zones are wrong defined, or when time step are too big Are you using Layering, smoothing, remeshing methods?

Vinay Morabad February 6, 2008 04:11

Re: Regarding Negative volume detected in Dynamic
I am using smoothing and remeshing. I am not using layering...In my case there are two zones .i.e. trochoid (casing) inside this casing only the rotor rotates. so for rotating body i am using rigid body and for foxed casing i am using deforming option..Then can u tell me how to define cell height. As i am not able to find the cell height for the elements what i have created in GAMBIT..

mAx February 6, 2008 06:09

Re: Regarding Negative volume detected in Dynamic
under define/dynamic mesh/parameters in the remeshing parameters you have info about your mesh height are you sure that MDM is the right choice for your model? for rotor/stator, sliding mesh yould be better are you solving 2d/3d?

Vinay February 6, 2008 09:56

Re: Regarding Negative volume detected in Dynamic
i am solving 2d pbm and i am sure that i have defined correct MDM for both rotor and trochoid.

mAx February 6, 2008 12:38

Re: Regarding Negative volume detected in Dynamic
ok I can I have a look at it if you want. you can send me an email

m.r_khani November 27, 2011 09:01

hello dear friend
can you send me your udf for motion pf wankel engine?

i have a simalr project that i want to see how can i write a udf for rotatin as an irrigular shape
me email:

sanjeetlimbu April 10, 2015 23:00

5 Attachment(s)
Hi i am using a 2D simple mesh- for simulating compression stroke. I using the profile define to get the dynamic motion.. average velocity is 9m/s to max 14m/s . cell size= 0.0001m, stroke length 254mm, clearance voume 14mm. The crevice is very important part for physics in combustion. I had the crevice and body part split between two zones. the crivece zone is moving -rigid body and body as deforming.
But when i using the preview mesh motion I am getting the negative volume error. even i tried to reduce the time step to 4.1667E-8, also getting the same error

Pl tell if I can do anything to change the negative volume error

kennyboy December 16, 2015 01:31

Hi vinay. I am currently working on a wankel profile as well. Similarly, I face the problem of negative mesh volume while trying to do a 2D simulation of the eccentric motion in fluent. So I was wondering how did you solve this issue in the end?

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