Module 6 - Vortex Panel Method Flashcards
Where are vortex panels placed in the vortex panel method?
Surface of the aerofoil
What is the basic implementation of vortex panel method?
Panels that are straight lines are placed on the surface of the aerofoil, each having different lengths and a unique but constant value for the vortex strength per unit length
What overconstrains the vortex panel method?
Applying the Kutta condition
How is the set of equations being over-determined dealt with in vortex panel method?
Remove one panel equation from the solution
What is the local value of the vortex strength per unit length equal to?
Local velocity tangential to surface of aerofoil
What condition on the velocity is set at each control point on the aerofoil surface is satisfied?
The normal component of the velocity (including free stream component and induced velocity) is zero to ensure aerofoil surface is a streamline
How is the pressure distribution determined using the vortex panel method?
Bernoulli’s equation
What choices affect the accuracy of a vortex panel solution?
- Panelling (density, number, lengths)
- Which panel is removed
How can you use the inviscid vortex panel code to determine the moment at c/4 given the moment at LE?
Aerodynamic centre is where moment independent of alpha. For many aerofoils it is close to c/4. We can use eq4.71 with the lift curve slope a0 and moment curve slope m0 in the linear region
Could also compute moment coefficient about position x and look for location where moment independent of angle of attack
What are the main additions of XFOIL?
- A viscous solver, allowing boundary layers to be resolved and flow separation to be computed
- Set the boundary layer transition point
- Compressibility effects