[nouman95]

hello everyone

i need some clarification about reference value in fluent like area and length of wind turbine blade

in my geometry there is no hub and blade is offset from origin by hub radius.

if i consider hub radius as r and blade length after hub as R then total radius from origin becomes r+R

now if i just consider blade swept area excluding hub for 120 deg domain i used pie*(R^2)/3

i got higher torque co efficient as compare to if consider following area pie*(R^2-r^2)/3 so i am really confused which method is

standard one.

there is no hub so there is no force or torque on that region

what should i consider blade area and length

BLADE AREA ,,, LENGTH

PIE*((R+r)^2 )/3 = (1.55m^2) , r+R=(1.21m),,,r=0.19m

PIE*((R)^2)/3 = (1.24m^2) , R=(1.09m)

PIE*(R^2-r^2) /3 = (1.533m^2)) , R=( 1.09m)

kindly guide me on this issue

Thanks

Best regards

M Nouman Nazir

[LuckyTran]

There is not one single torque coefficient. The reference area and length is decided when you define what is the torque coefficient. I.e. you want to compare your coefficient with somebody else's, then you ask them what reference area and length they used in their torque coefficient. Otherwise, you calculate a different coefficient.

[nouman95]

actually i have two design of blade one is baseline and other is improved one.....so i have to compare them ....in any case whatever i put reference area and length for both blades i got higher cm for improved case......but i wanted to make sure that what is standard method.......can you help me out picking the right formulas for reference blade area and length

[LuckyTran]

If you haven't decided on an area and length then there is no meaning to calculating any coefficient. Just compare actual torque values if that's the case.

[nouman95]

so reference values not affect actual torque for both cases?

[LuckyTran]

Reference values are for calculating derived values like coefficients only they don't affect any solution values. You can check this easily. Just put in non-sensical numbers for them and watch how the solution doesn't change.

[nouman95]

ok.....i will try it.....
Thanks

[LuckyTran]

Just do it. It's only a few button clicks. There's nothing to be scared about. Explore! Learn something about Fluent. Good Luck.