Learning Forum

[Jason Sum]

Dear all,

I am simulating a car passing at 10m/s (dynamic mesh) and induce wind on the S-type wind turbine (dynamic mesh with 6DOF), as shown below. 

My mesh is having hexagonal meshes with sizing of 4mm inside the turbine circle, 5mm out of it, and inflation layers in both blades and cars.

Ortrhogonal quality is > 0.6

Error popped up with "Error: Update-Dynamic-Mesh failed. Negative cell volume detected. Error Object: #f"

I have two questions would like to seek for some directions and solutions:

1. I spot the extension and compression of cells when the car is moving to the right, I am thinking if the error is caused by continuous entension and compression of the cells, making it skew in shape and cause negative cell volume. I have activated the remeshing methods, but still unable to solve.
2. As the 6DOF motion of turbine is passive, usually set with layering and diffusion for rotation motion, while the linear motion of car some suggest deselect layering and use spring/laplace/boundary layer. While only one setup is allowed in the GUI, Can I just go for all mesh methods and diffusion for the whole case?

Note: I ran a trial setting the car just as a wall object without motion, and inlet with some wind, the turbine is able to rotate without errors.

   

[Federico]

Hello, 

hex-mesh is not compatible with remeshing, which is why your are seeing streched out elements on the left and compressed elements on the right, which eventually result in collapsed cells or negative volume elements.

You will need to mesh the volume surrounding the car with tetrahedral cells. An alternative would be to have a structured block of hex cells around the car and use the layering approach.

[Federico]

You can read more on this here: 12.6. Using Dynamic Meshes (ansys.com)

[Federico]

Hello, 

you will need to mesh your domain with tetrahedral elements (hexagonal cells are not compatible with remeshing).