Outline and Objectives:
 

• Solve a highly compressible flow in FLUENT

 
• Study how lift and drag changes with angle of attack

 
• Study turbulent compressible boundary layer around an airfoil

 
• Study the location, orientation, and intensity of shock wave.

The problem: Turbulent flow past a transonic airfoil at a non-zero angle of attack.

The mesh was made to cover a very large region, from -20C to +25C in the x (along-cord) direction, and -30C to +30C in the vertical, where C = 1 m is the cord length. The origin of the coordinate system is at the nose of the airfoil.

 
 
  Angle of Attack = 4 degrees:

 
 
  Angle of Attack = 10 degrees:

This problem is taken from FLUENT 6.1 Tutorial Guide. See Modeling External Compressible Flow.

Solution Procedure and boundary conditions:
 

• Import the mesh.

 
• Use "coupled" solver with "implicit" formulation.

 
• Turn on Energy equation.

 
• Turn on the Spalart-Allmaras turbulence model.

 
• Use "ideal-gas" as density model and "sutherland" as viscosity material model.

 
• Set operation pressure to zero.

 
• For the "pressure-far-field-1" boundary, set Gauge pressure = 101325 Pa, Mach = 0.8, temp = 300 K, x-component = cos(4) = 0.997564, y-component = sin (4) = 0.069756. Set turbulence specification method to "Turbulent viscosity ratio" and set ratio = 10, meaning at far-field, the turbulent viscosity is 10 times material viscosity.

 
• Solution control: Under-Relaxation factor for modified turbulent viscosity = 0.9; Courant Number = 5.

 
• Turn on Solve-Monitor: Drag, Lift, and moment coefficients.

 
• Double-check to make sure that y+ near the surface is between 30 to 300.