Irrotational flow Flashcards
Kutta Condition
Due to the presence of boundary layers, the flow is parallel to the airfoil surface at the trailing edge but wraps around the leading edge.
How can the flow around an airfoil be described?
Due to viscous effects/boundary layers, the flow around an airfoil can be seen as the superposition of a uniform flow and a circulating vortex.
What is the total drag? (EQN)
Total drag = Pressure drag + Friction drag
Separation Region
Closed Streamlines (“Recirculating Eddy”)
Dividing streamline
The border between separation and outside region
Separation and Reattachment points
Stagnation points at the start and end of a dividing streamline.
Where does flow separation occur for a stalled airfoil?
On the suction side
Definition of a streamline in a steady flow
A continuous line that is tangential to the velocity vector at all points along it.
What are Stagnation points
Points where streamlines meet and divide. Where the velocity equals zero.
A stream tube
A region of fluid bounded by streamlines.
- Mass flux within a stream tube is constant.
- Continuity: q1S1=q2S2
Vorticity, omega z
The rate of anticlockwise rotation.
Vortex
A local structure in a fluid flow characterized by a concentration of vorticity in a tubular core with circular streamlines around the core axis.
Vorticity (EQN)
ωz=∂V/∂x−∂U/∂y
Shear Distortion (EQN)
εxy=0.5(∂V/∂x+∂U/∂y)
Normal Distortion (EQN)
εxx=∂U/∂x
