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

WIND TURBINE BLADE AIRFOILS

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

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

PRESSURE FIELD L V Low High Ambient

PRESSURE FIELD: 4 DEG ANGLE OR ATTACK V Low High Ambient

PRESSURE FIELD: 12 DEG ANGLE OF ATTACK V Low High Ambient

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