## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### Calculation Lift and Drag of airfoil

Subscriber

Hi everyone,

I am simulating an airfoil that I want to get its performance curve at different angles of attack. I solve its flow steady.

From an angle of attack of 0-8.5 degrees I get a constant value for lift and drag. If the angle of attack is about 9 degrees, the residuals of the solution as well as the lift and drag graphs that are drawn in Fluent become oscillating. As the angle of attack increases from 9-20 degrees, this behavior still exists.

Can someone help me what should I do to calculate lift and drag in the range of 9-20 degrees of attack angles?

Should the flow be solved in the form of transient in this range (9-20 degrees)?

Regards

• Hemantg_17
Subscriber

What I deduce from your observations is that stalling, or flow separation may have occurred after the 9 degree angle of attack. To get a better understanding of your problem, please provide the following information:

1.Aerofoil type.

2.Images of performance curves (quantities plotted)

3.Have used the parametric option or entered values manually?

Subscriber

Yes, stall or current separation may occur at angles greater than 9 degrees.

I have experienced this for many airfoils.

My question is, in the angles after the stall, to calculate the performance curve of the flow airfoil, should it be solved Steady or Transient?

I did not understand the meaning of your sentence (3.Have used the parametric option or entered values manually?). Can you say more clearly?

I manually input the Cos and Sin values of each angle into Fluent.

• Hemantg_17
Subscriber

It is difficult to determine which settings should be used, whether steady or transient and what is the significance of calculating performance curve after airofoil stalls ?? I would recommend going through the courses available on AIS. What I gather from your statement is that you entered AOA values manually. Please do check the parametric option in Ansys Fluent to generate a set of output parameters based on the input parameters(if interested).