Drag coefficient calculation – Reference values

- October 20, 2019 at 8:18 pm
  
  egorbena
  Subscriber
  
  Hi,
  
  I'm trying to calculate the drag coefficient of a cylinder with 100 mm diameter . The simulation is 2D and the flow material is air ro = 1.225 kg/m3 and viscosity = 10^-5 m2/s. I'm using a k-epsilon model with curvature and kinetic energy production limiter set on. The mesh provides a y+ < 1.
  
  The values I get are very small, around 0.03 when should be around 1.4.
  
  I tried to improve the results by changing the reference values, from Area = 1 m2, Depth = 1 m, Length 1 m to Area = pi*r^2 m2, Depth = 2*pi*r m, Length 2*pi*r m. The result I get for these reference values is Cd = 1.0.
  
  Does anyone know how I could further improve my result to get a Cd closer to 1.4?
  
  Thank you
- October 21, 2019 at 4:42 am
  
  DrAmine
  Ansys Employee
  
  What about using sst Model and doing some Grid sensitivity Analysis
- October 21, 2019 at 4:46 am
  
  DrAmine
  Ansys Employee
  
  Reference Area is used to calculate drag coefficients so you need to provide the proper area.
- October 21, 2019 at 7:24 am
  
  egorbena
  Subscriber
  
  Hi Amine,
  
  Thank you for your reply. Regarding the reference area, should it be the cross-sectional area of the cylinder ( A = pi*r^2) or the cross-sectional area exposed to the flow (A = Diameter * Depth)?
  
  Best regards,
  
  Eduardo
- October 21, 2019 at 2:43 pm
  
  DrAmine
  Ansys Employee
  
  it does depend how the drag you are looking for is defined. Generally one would use the frontal projection area at zero Angle of Attack.
- October 21, 2019 at 3:06 pm
  
  egorbena
  Subscriber
  
  Thank you Amine!