Abstract:
This paper investigates the sensitivity of time step and time increment on the
performance of 1800 twist helical Savonius rotor using commercial
computational fluid dynamic code based on flow-driven method. The best
combination of time step and time increment was first determined by
comparing simulated rotational speed with the actual rotor speed generated
by wind speed of 5 m/s. Other rotational speeds at 2, 3, 4 and 6 m/s are then
predicted based on this condition. The results show that time step and time
increment have a significant impact on the accuracy of the predicted rotor
rotational speed (RPM). A small time increment and a large time step require
longer computational time but in return give closer rotor RPM to the actual
experiment. On the contrary, a larger time increment with smaller r time step
dramatically reduced the computational time but resulted in poor rotor RPM
prediction. The results also show that the closest RPM predicted by this
analysis is when the time step and time increment were at 8000 and 0.0015
seconds respectively. This paper concludes that an accurate prediction of rotor
rotational speed can be achieved by setting the right combination of time step
and time increment.
