2D Aerofoil Simulation

[Anonymous]

Hello,

Im only just learning to use CFD, so appologies if this is a stupid question. I have tried to look through the forum for related questions however none of them seem to help.

Im trying to gain an estimate of the downforce produced for a multi-element design, however initially I want to find the co-efficient of lift of a particular aerofoil profile. 

I have created a 2D sketch in Inventor and created a patch around it as shown in the screenshot. 

I have then used the active model link between Inventor and Simulation CFD. I then applied the boundaries of:

- Velocity (30mph) on the left edge
- Slip/Symmetry - top and bottom

- pressure = 0 - right edge

Then added a mesh and made it finer around the aerofoil. And attempted to solve it. 

I then click wall calcuation to get the force (Fy), I select the edge of the aerofoil shape. When I get to the calcuations point I find the force is 2.49e-8 N, and the area is 571.917mm^2. If i then Calculate the Cl I get a number e-8 which is no where near what I am expecting? Is it becuase my model size is too small in which case what is a useable chord length?

I have also attached two visual representations of my CFD.

Any help would be greatly appreachiated. 

[Royce_adsk]

I would suggest to start looking at the various posts regaring the recent conversation on the NACA0012 airfoil model and associated webinar on that topic.

Thanks!

[srhusain]

It appears from the area you mention that the model as received by SimCFD is tiny and this is likely the reason why you are seeing such small forces. Also, once you have scaled the model dimensions properly, you need to have a finer mesh near the body in order to resolve the flow boundary layer accurately.

Hope this helps.

[Anonymous]

Thank you for your adivce, I upped the scale to be more fullsize (571mm) and I still get very small Cl values (0.06 instead of the expected 0.4) not as big of a gap as before. Does the larger the size of the object increase its accuracy? If not there is anything else that could be affecting this?

[OmkarJ]

Be aware of your calculations of Cl here. If you are running this as a 2D, then the lift is per unit length. Check the unit in which you have imported the geometry. If it is mm, then the lift force in your calculation should be the wall force you calculate divided by 1e-3 m. This is a fairly common Rookie mistake.

Also, by the looks of your plots (which should have included the legends for the values anyway) the mesh needs a lot of improving. I would suggest going through Royce's airfoil webinar which offers excellent advise on how to model such cases.

https://www.youtube.com/watch?v=N4z8HcBtL6U&index=6&list=PLIv6vwn776aRRpQtH6KUqHw8QXkZyNlyq