I am testing a vertical turbine by using Ansys Fluent with the sliding mesh technique. What I am doing is that I give a specific angular velocity and I get the torque to apply it in an equation to find the performance, but I am getting positive and negative values, so is that ok?
Do I have to take the average and apply it in the equation only?
I am doubting my results because some of the values are not realistic.
Please give me your opinion.
Dear Baqer Zaki
It might be correct. Vertical axis wind turbines such as the Savonius and Darrieus have negative torque at some angular positions and tip speed ratios. However, it is usually positive. Check the direction of rotation to be correct.
Article Aerodynamic performance of helical Savonius wind rotors with...
Yes, you have to calculate the average torque in a period.
- Make sure your moment axis is correct
- You are using forced motion, which could result in negative moment.
In theory, you can predict the free-motion from forced motion but it is debatable and many researchers object it.
Возможно появление отрицательного момента. Нужно рассмотреть геометрию сочетания направления силы, уклона по лопастям турбины и действия силы тяжести. При определенном сочетании возможно появление вихревых потоков, которое порождает отрицательное направление момента.
It depend on the applied angular velocity. As you know, the result will be calculated in the form of Cp and plotted as cp versus TSR. Your result might be correct. But you need to run for longer time step (no. of revolution). Try observed the torque pattern on every revolution. Make sure the amplitude of the torque stable for a few last revolution. Then do average for the torque data for last revolution. I think you will get a better result ( +ve torque)
Mohd Shahrul Nizam Ibrahim I appreciate your comment. It is really helpful
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