Page 18 - Wind Energy Handbook

xviii LIST OF SYMBOLS

d PL pitch diameter of planet gear
D drag force; tower diameter; rotor diameter; flexural rigidity of plate
E energy capture, i.e., energy generated by turbine over defined time
period; modulus of elasticity
Efg time averaged value of expression within brackets
f tip loss factor; Coriolis parameter
f( ) probability density function
f j (t) blade tip displacement in jth mode
f in (t) blade tip displacement in ith mode at the end of the nth time step
f J (t) blade j first mode tip displacement
f T (t) hub displacement for tower first mode
F force
F X load in x (downwind) direction
load in y direction
F Y
force between gear teeth at right angles to the line joining the gear
F t
centres
F(ì) function determining the radial distribution of induced velocity
normal to the plane of the rotor
F( ) cumulative probability density function
g vortex sheet strength; peak factor, defined as the number of standard
deviations of a variable to be added to the mean to obtain the extreme
value in a particular exposure period, for zero-up-crossing frequency,
í
g 0 peak factor as above, but for zero upcrossing frequency n 0
G geostrophic wind speed; shear modulus; gearbox ratio
G(t) t second gust factor
h height of atmospheric boundary layer; duration of time step; thickness
of thin-walled panel; maximum height of single gear tooth contact
above critical root section
H hub height
H jk elements of transformational matrix, H, used in wind simulation
H i (n) complex frequency response function for the ith mode
I turbulence intensity; second moment of area; moment of inertia;
electrical current (shown in bold when complex)
I B blade inertia about root
ambient turbulence intensity
I 0
added turbulence intensity
I þ
added turbulence intensity above hub height
I þþ
inertia of rotor about horizontal axis in its plane
I R
longitudinal turbulence intensity
I u
lateral turbulence intensity
I v
vertical turbulence intensity
I w
total wake turbulence intensity
I wake p ffiffiffiffiffiffiffi
j 1
k shape parameter for Weibull function; integer; reduced frequency,
(øc=2W)
k i generalized stiffness with respect to the ith mode, defined as m i ø 2
i