Hi All
I know how to find torque via CFD post for wind turbine, select the blade and axis in function calculator. But I find a big difference between the experiment and CFD value at high wind speed.
But I need to how or what formula of methodology used in CFD post to compute torque,
basically the formula is
T=Sum_i(nu*rho*dU/dx)*A*r+sum_i(p*A*r)
where nuand rho are the properties of the fluid, U the velocity, x the spatial coordinates, A the area of the mesh element surface and r the distance from the face center from the axis.
(nu*rho*dU/dx) represent the shear stress, so the torque is given by a viscous contribution Sum(nu*rho*dU/dx)*A*r and an inertial one sum(p*A*r)
Sum_i means summing for all the cell faces corresponding to the patch for which you want the torque.
See this paper
https://www.researchgate.net/publication/265418917_Churning_power_losses_of_ordinary_gears_A_new_approach_based_on_the_internal_fluid_dynamics_simulations
eq. 7 and 8
Article Churning power losses of ordinary gears: A new approach base...
basically the formula is
T=Sum_i(nu*rho*dU/dx)*A*r+sum_i(p*A*r)
where nuand rho are the properties of the fluid, U the velocity, x the spatial coordinates, A the area of the mesh element surface and r the distance from the face center from the axis.
(nu*rho*dU/dx) represent the shear stress, so the torque is given by a viscous contribution Sum(nu*rho*dU/dx)*A*r and an inertial one sum(p*A*r)
Sum_i means summing for all the cell faces corresponding to the patch for which you want the torque.
See this paper
https://www.researchgate.net/publication/265418917_Churning_power_losses_of_ordinary_gears_A_new_approach_based_on_the_internal_fluid_dynamics_simulations
eq. 7 and 8
Article Churning power losses of ordinary gears: A new approach base...
Usually, torque based on CFD results is computed from the following formula for power:
P = mfr * DH = q * omega
where:
- mfr is the mass-flow rate accross the turbine, in kg/s
- DH is the change of stagnation enthalpy through your turbine, in J/kg
- q is the torque, in N.m
- omega is the angular speed, in rad/s
Iyaz,
You can calculate the torque basically with this function:
Torque=torque_x()@turbine
Here the turbine rotates around x axis. You should select this, according to your coordinate axis.
The turbine here, is the body that rotates. Try this one.
Dear Franco and Nicolas thanks for your reply.
@Dear bro Abdullah, I understood how to provide set up for torque computation, I need to know internally how CFD post compute torque based on the set up as u mentioned
Maybe it is as in fluent where you can export just the torque coefficient. So check, and set eventual reference values to 1.
For example
Cd = force_x()@Surface / (0.5*Rho*U^2*A) where A is a representative area calculated as A = reference_length * reference_width in which the reference values are chosen arbitrarily by the user.
Franco
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