I'm currently running a flow simulation on a Wells turbine and am running into a little difficulty. The Wells turbine is enclosed in a 0.6m pipe, with a tip clearance of 1mm between blade and pipe. I am running tests with a speed range of 1000-2000 rpm. I have enclosed a rotating region around the blades of the Wells turbine. The rotating region covers exactly the width of the blade. I have set an inlet flow of 5.98m/s and static pressure at the outlet. I set a surface goal for torque on the 6 blades of the Wells turbine. When I run the study I am getting negative torque in my results. I have the rotating region rotating in the right direction aswell. The pressure drops across the turbine steadily increase with speed, but my torque increases in the negative direction.
This is giving me negative efficiency when I do calculations. Any ideas where I'm going wrong?
Any advice is greatly appreciated.