College Project - Design a wind tunnel (problem with simulating wind flow)

[Anonymous]

Basically, I've created the 3d model to scale etc in inventor and imported it into Autodesk Simulator CFD. 

As I had only started using Inventor and CFD today, I have absolutely no idea how to place a source of airflow into the object I have created (without creating a physical object i.e. a flat plate to use as a source as ive seen in videos, other than that I wouldnt know where I could place the outbound?). 

I have attatched a screenshot of the design and have marked where I need the virtual fan  to be.

The fan theoretically needs to produce 8.696m/s in velocity to achieve the goal of at least 70m/s at the test section (which is based where the aerofoil test peice is)

Any help will be greatly appreciated.

[Jon.Wilde]

Hi,

Could I suggest you start by looking at a few tutorials here? CFD 2015 Tutorials

What is the actual goal of the analysis?

Do you need to model the entire system?

It might be better with a flow rate inlet and a P=0 outlet along that bottom section - simpler 🙂

Kind regards,

Jon

[Anonymous]

Hey Jon,

Thanks for the response, 

Could I suggest you start by looking at a few tutorials here? CFD Tutorials

Thanks 🙂 I will definatly be spending a good few hours going through these videos.

What is the actual goal of the analysis?

The aim of the project is to create and build a closed-loop wind tunnel with a velocity at the test section of atleast 70m/s. 

and also the following:

• The aim of our project is to construct a wind tunnel with the capability of producing subsonic airflow.

• To study the behavior of air as a fluid medium within the wind tunnel its self, relating to pressure, temperature and airflow.

• To create subsonic laminar flow.

• To have the wind tunnel design produced aim to have to tunnel constructed and “tested”  ready for the project presentations.

Do you need to model the entire system?

As the project is based on how pressure, temperature and velocity changes around the wind tunnel I would have thought yes, although i could possibly create a gap where the fan would be and place inlets and outlets on each side.

It might be better with a flow rate inlet and a P=0 outlet along that bottom section - simpler  

Ill give this ago now and update this post as needed 🙂 Many Thanks

Note: another reason for this simulation is we are unsure of the flow rate the fan needs to produce to get us our 70m/s, in the maths we've done its correct but i'd like to also check on a simulation program such as CFD 🙂

[Jon.Wilde]

Hi,

No problem at all, looks like a fun model.

If you are thinking of subsonic definitely start with the inlet and outlet rather than a fan - any of the simplified parts (fans/resistances) are best avoided for anything other than incompressible flow.

The only downside is that it would not be closed loop, so any thermal changes would not carry forwards from the outlet to the inlet...

You may need to consider a non-standard setup, check out this page as I think it might help you decide what boundary conditions to use (just flow at the inlet and pressure at the outlet won't be sufficient).

Internal Compressible Flow - my go-to page for quick reference for these studies

Compressibility - just the main page but it might prove useful to you

I hope this helps.

Kind regards,

Jon

[Anonymous]

In the videos there is a solid section which they select to use as the fluid, the object I have is hollow on the inside - even when I try and do a simulation with velocity and pressure it doesnt seem to work, from the looks of it (see screenshots attatched) it looks like its trying to flow within the surfaces of the material instead of the hollow inside?

I made the 'surface' be 3mm aluminium and the volume to be air.

I attempted to use geometry tools to add a volume within but it was completely grayed out.

[Jon.Wilde]

Hi,

You need to seal the volume - then CFD will fill it with a fluid for you when launched from CAD. 

Kind regards,

Jon