Transcript Slide 1

CATs
COHERENT APPLICATION
WindTHREADS
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
Pressure P
(normal to
surface)
V
L
Lift is net pressure force:
normal to velocity *
D
Shear stress t
(parallel to
surface)
Drag is net shear force:
parallel to velocity *
* Assumes no separation/stall
BASIS
FOR
LIFT FORCE
Streamline: tangent to
velocity
Streamtube: constant
flow rate
L
Free stream
V
p
Stagnation
streamline
Higher velocity
Lower Pressure
Lower Velocity
Higher
Pressure
p+½rV 2 =constant
4
PRESSURE FIELD
L
V
Low
High
Ambient
PRESSURE FIELD: 4 DEG ANGLE OR
ATTACK
L
V
Low
High
Ambient
PRESSURE FIELD: 12 DEG ANGLE OF
ATTACK
L
V
Low
High
Ambient
BLADE LIFT AND DRAG
x
y
Wind
DRAG
D
Dy
x
y
Dx
Wind
Velocity
Total
Velocity
Vector
Lx
Ly
Velocity
due to
rotation
Lx + Dx is the net “thrust” force
Ly - Dy is the net “torque”
force that produces power
L
LIFT