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Regarding Negative volume detected in Dynamic mesh

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Old   February 5, 2008, 23:47
Default Regarding Negative volume detected in Dynamic mesh
  #1
Vinay Morabad
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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.

CAN ANY ONE PLEASE TELL ME THE SOLUTION FOR THIS PROBLEM AS EARLY AS POSSIBLE.

Thanks and Regards Vinay
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Old   February 6, 2008, 02:33
Default Re: Regarding Negative volume detected in Dynamic
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mAx
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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.

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Old   February 6, 2008, 03:56
Default Re: Regarding Negative volume detected in Dynamic
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Vinay Morabad
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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
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Old   February 6, 2008, 04:05
Default Re: Regarding Negative volume detected in Dynamic
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mAx
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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?
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Old   February 6, 2008, 04:11
Default Re: Regarding Negative volume detected in Dynamic
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Vinay Morabad
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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..
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Old   February 6, 2008, 06:09
Default Re: Regarding Negative volume detected in Dynamic
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mAx
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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?
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Old   February 6, 2008, 09:56
Default Re: Regarding Negative volume detected in Dynamic
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Vinay
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i am solving 2d pbm and i am sure that i have defined correct MDM for both rotor and trochoid.
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Old   February 6, 2008, 12:38
Default Re: Regarding Negative volume detected in Dynamic
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mAx
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ok I can I have a look at it if you want. you can send me an email
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Old   November 27, 2011, 09:01
Default hi
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mohamadreza
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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: m.r_khani@yahoo.com
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Old   April 10, 2015, 23:00
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sanjeet Limbu
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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
Attached Images
File Type: png crevice -piston.PNG (9.7 KB, 6 views)
File Type: jpg Orthogonal_0.9_near partition.jpg (38.9 KB, 5 views)
File Type: jpg skewness_0.355.jpg (49.2 KB, 5 views)
File Type: jpg neg_volume error.jpg (45.9 KB, 5 views)
File Type: jpg dynamic mesh setting+_preview.jpg (47.6 KB, 6 views)
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