Negative cell volume error during 3d simulation

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  • Last Post 19 December 2019
jitsinha posted this 19 October 2019

I am using a 3D cylindrical domain. Inside which there is an 3D elliptic airfoil, which will have a sinusoidal motion vertically (heaving motion). 

In DESIGN MODULE of ansys i used Boolean to subtract the airfoil from cylinder. And by that i have created a elliptical cavity inside cylindrical domain. Right side of domain is outlet. Left side is inlet.

I am using structured mesh as per attached file. 

This are the only parameters i am giving as input in fluent during simulation -

1. General tab - transient

2. Boundary condition - airfoil (No slip condition)

3. Compile the UDF for heaving motion

4. Dynamic mesh - Airfoil (rigid body), specify the CG location.

Smoothing - Diffusion based, Boundary distance, diffusion factor = 1

Re-meshing using default values, remesh interval = 1

time step = 0.0001 sec

 

But after certain iteration in preview mesh motion, nagative cell volume error is coming.

My query - 

1. Does re-meshing work for 3D structured mesh?

2. What are the boundary condition i need to specify? specially on the side walls as the wall mesh will move when airfoil oscillates.

3. What are the zones i need to specify inside dynamic mesh tab. (like zone wise deforming, cell height, etc)?

4. How to resolve negative cell volume error.?

 

Please need your help in this regard. 

Attached Files

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rwoolhou posted this 21 October 2019

Have a look at the tutorials and YouTube videos, and also review the moving mesh threads on here. 

jitsinha posted this 18 December 2019

Sir,

My domain looks like these (see the attached picture)

I have kept the domain faces as deforming. Airfoil rigid body. Fluid zone as deforming. 

Once i am doing the preview mesh motion, after 400 iterations this face cells are deforming outside. As a result i am getting negative cell volume error.

 

domaindeformed cells on face

How to rectify these issue.

Please help !!!

rwoolhou posted this 18 December 2019

I think you need to fix the nodes on the "end" faces so that that can only move in x & y. 

jitsinha posted this 18 December 2019

can you please guide me how to do it Sir?

 

rwoolhou posted this 19 December 2019

I'm not sure, it'll be covered in tutorials/YouTube: I have colleagues to do moving mesh problems! 

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