1. Supplemental Learning Module Introduction to Lift and Drag
COHERENT APPLICATION THREADS
CATs
Wind Turbines
Supplemental Learning Module
ME 303 Fluid Mechanics
Introduction to Lift and Drag
Don Wroblewski
Associate Professor, Mechanical Engineering
Associate Chair, Aerospace Engineering
Undergraduate Program

2. WIND TURBINE BLADE AIRFOILS

3. AIRFOIL LIFT AND DRAG L V D
Pressure P (normal to surface)
Lift is net pressure force: normal to velocity * L V D
Shear stress t (parallel to surface)
Drag is net shear force: parallel to velocity *
* Assumes no separation/stall

4. Streamline: tangent to velocity Streamtube: constant flow rate
Basis for Lift Force
Streamline: tangent to velocity
Streamtube: constant flow rate L
Free stream
Higher velocity
Stagnation streamline
Lower Velocity V p
Explain why streamlines are angled
Lower Pressure
Higher Pressure
p+½rV 2 =constant

5. PRESSURE FIELD L V
Low
High
Ambient

6. PRESSURE FIELD: 4 DEG ANGLE OR ATTACKV
Low
High
Ambient

7. PRESSURE FIELD: 12 DEG ANGLE OF ATTACKV
Low
High
Ambient

8. BLADE LIFT AND DRAG x y x y DRAG D Dy Dx Lx Wind Velocity Wind Ly
Total Velocity Vector L
LIFT
Blades about 15,000 lbs each nacelle+hub+blades=200,000 lbs or about 100 tons tower 400,000 lbs or about 200 tons. Combined system weighs about the same as a 777 aircraft
Velocity due to rotation
Lx + Dx is the net “thrust” force
Ly - Dy is the net “torque” force that produces power