How to simulate upper surface blowing?

[jsenna]

Hello, I am a student and new to using autodesk simulator

I am trying to get the force generated by the combined effects of the Coanda effect and bernoulis principle on a surface. I designed a simble L-shaped model where one wall has a prescibed velocity that blows over the other. However, when I tried to simulate it it acted as if the fluid was flowing on the inside of my model, instead of being blown over it.. Is there a setting I need to change to make the flow external and the object solid? Also, has this kind of calculation been attempted before with this software?

Ive attached a screenshot of my results

[Joey.X]

Could you post your whole model and all boundary conditions applied? 

Any numerical model is partial portion of the physical model, the model setup(cincluding BCs) depends on the assumptions. 

[John_Holtz]

Hi jsenna,

I do not understand your figure, and only partially understand your description. But it sounds like you modeled the solid. In a fluid flow analysis, you need to model the fluid, not the solid. The surfaces of the fluid in contact with the solids will automatically receive a 0 velocity constraint (unless you apply a different load to such surfaces).

[jsenna]

Thank you for the responses.

I realized that I needed to do external fluid analyis, so I used that feature to create a box around my model, however when I try to run the simulation now it shows an error. 

unknown error (16):
Input data may have wrong boundary mesh or illegal elements.

I tried researching this error but could not get it to go away. Could I be importing my model wrong?

My steps are:

Design part in Inventor 2012

click simulate under add-ins in Inventor

click external fluid under mesh

prescribe a fluid velocity to one of the model faces

Is this correct or am I just missing some information in my model?

I have attached my model and fea files for clarification. Any help is appreciated, and I working file with description of changes would be very helpful.

Thanks

[Joey.X]

According your posted model, and assuming the .ipt model is the solid parts

Two obvious fixes are necessary

- Set up your simulation for fluid parts only, and the boundary conditions is on the surfaces of the fluid parts, all solid parts should be excluded if imported from CAD

- Ensure suffcient mesh nodes (mesh density) in the fluid interior and surfaces

Please refer thread titled as How to find the drag on a 3d Body? for your model setups, which has lots similarity as your model. 

[jsenna]

I've come a long way from the previous mdoel I psoted. Since then I have succesfully made several models.

However, while running my most recent test I ran into an unexpected problem that I can't figure out how to solve. In my newset model I am using a duct to blow air over a surface. I am using an internal fluid for inside the dcut, and an external fluid for the surrounding enviroment. I use an external fan intake on one side of the internal fluid, and an external fan exhause on the other.

The problem I am running into is that my mdoel will eityher fail analyis with the error of analysis was not comleted.

When I look at the log it seems the only wraning/error is a number of dead nodes, telling me to use tetrahedra and wedges (boundary layer) to solve the problem.

However, when I change the mesh type to tetraheda and wedges (boundary layer), the mdoel fials meshing with the error: Error Number 340: Boundary layer meshing failed. Reducing extrusion distance might help.

How can I get this thing to finally finish analysis!

Any help is appreciated

[Joey.X]

Hi, jsenna

Glad to know to get progress on your projects.

For meshing failures on boundary layer mesh, you can try single layer boundary layer and reduce thickness of the boundary layer, which helps to pass the meshing. 

For the warning of dead elements in fluid flow processor, it is probably allowable depending on your own judgment on the result (pattern and values), but it is preferred to use boundary layer mesh to relief this issue. 

Thanks for the feedback.