CFD Online Discussion Forums - Setting condition on a VAWT

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to cfd les
which mehtode u r using for find out moment and plz share u r images of mesh file ...as i share it .....will specify all details then i will able to help u ...........

Dear Patil,

What is relation of moment to torque? I mean how do you convert moment to torque?

i am taking moments from report forces --moments -- here u have to specify centre of roatations of moments which u wanted if u r centre is zero zero then give centre of roations =00 ... ya i am taking that momont is torque ....

Quote:

Originally Posted by esp-m1000 (Post 262061)

Hi nana,
sorry, when i wrote "HAWT like yours" i mean VAWT. But the Cp values i gave to u are right. I'm doing simulation on a VAWT similar to yours but i have 5 blades instead of 4 and a non-symmetric airfoil. But this don't mean ur turbine works with drag; Lift is always bigger than drag for airfoil, if they work in normal condition (no-stall).
So your turbine works with lift.
I have looked at your model, i think that cylinder surface are too near blades, and the free stream volume is also too little. I think u must have a bigger cylinder in whinch locate the turbine and a bigger free stream volume. If u can't becouse u have to simulate in a real wind tunnel maybe u have to use a scaled model and so reduce the scale of your model.

For my simulations I have a problem, i had a report moment of 7600 N-m, how i can obtain the power? as i wrote after if i multiply for the time step i obtain a too high value.....

hi dear esp
i have the problem as you had.
my torque amounts which are take from turbine are too big .
what can i do??
how did you figure out your problem?

Quote:

Originally Posted by enry (Post 249509)

Hi,
yes, of course, T is torque per unit area.
I wrote a UDF in order to get the time average torque, that FLUENT can't give you.
Bye.

hi enry
i had simulated a wind turbine using fluent and now i want to calculate the power out put
i,m using this formula: p=torque (NM) *omega(rpm)*2*pi /60
and my rotation axis is y and my center of rotation is (0,0,0).i had set my moment center on (0,0,0) too.
the amount of this power output is 10 times bigger than real results.

what can i do:(
would you plz help me??

i thought u r formula for calculating power is worng ..use...............
power= cp /(1/2 * raho*A*Vinfi ^3)

Quote:

Originally Posted by p.bhushan2727@gmail.com (Post 430350)

i thought u r formula for calculating power is worng ..use...............
power= cp /(1/2 * raho*A*Vinfi ^3)

tnx dear
would you plz what you mean of "cp" ,"raho" and the other parameters:confused:
in addition i,m using fluent for my simulation.

HERE CP=Coefficeint of power ,
raho= dencity of liquid for water =1000 for air=1.998,
Vinfi = inlet velocity kkkkkkask if u need any help

Quote:

Originally Posted by p.bhushan2727@gmail.com (Post 430397)

HERE CP=Coefficeint of power ,
raho= dencity of liquid for water =1000 for air=1.998,
Vinfi = inlet velocity kkkkkkask if u need any help

tnx dear
what is the amount of cp??
can i find it in fluent results????

hi....can u please tell me why i get negative cm all the time...i have used tri meshing in icm cfd and sliding meshing technique....

Quote:

Originally Posted by shafqat (Post 491063)

hi....can u please tell me why i get negative cm all the time...i have used tri meshing in icm cfd and sliding meshing technique....

please share your boundry conditions and mesh file here at images of it then we will move forward

i am using ke realizable enhancement wall treatment ........for reference values i use swept area in area and length of turbine in length

CFD of propeller

Hi i am doing CFD of aircraft propeller.
i want to know torque which i got from fluent is ok ????
thrust force which i got from fluent is ok ?????
or there is need to calculate thrust by momentum equation for it.. . . . .
i.e

T = [ MASS FLOW RATE * (Ve - Vi ) ]

looking forward.
thanks

LES vs K-w turbulence model simulations on wind turbine rotor

Hi all,
I am doing unsteady CFD simulations on 3 bladed NREL wind turbine rotor using k-w as well as LES technique with rotational velocity of 14 rpm with wind shear at inlet ( udf).Operating pressure as 1 atm and at outlet radial eq. pressure distribution. But m getting pressure coefficient value for different sections of blade in the range +20 to -70, using both models. I doubt the values coz always I have never seen such high values.

Following inputs have been used:
regarding mesh : I meshed the blades in ICEM with proper mesh check and 15 prism layers unstructured mesh and sufficiently finer( as per the requirement of LES).
Fluent :
Velocity inlet with wind shear and TI :0.15, Turbulence viscosity ratio: 10
At first, steady simulation were carried out for 1000 iterations using MRF and kw model.
Once flow gets stabilized, changing it to transient and sliding mesh and using steady flow results for initialization .
Pressure-vel coupling :SIMPLE (in both models).

Reference values:( from velocity inlet)
Area:238 (planform of single blade)
Length:1 (later can be changed in matlab as variable chord distribution in the blade)
pressure: 0 atm( operating pressure is already
1 atm)

I want to ask where have I done mistake because of which m getting such high values for pressure coefficient? Any help would be appreciated. kindly reply