[Zaqie]

Hi,

I have modelled a water turbine in Rhinoceros and meshed it to sufficient smoothness in ICEM CFD and then imported to Fluent. The boundary conditions are as in the attachment.

In addition, the following BC's are used.

1. Velocity Inlet - at inlet
2. Outflow - at outlet

The simulation is run in Fluent 12.0 in a moving reference frame using k-omega model(SST) and a copled solver. The inputs are velocity at inlet in absolute frame, angular velocity in moving reference frame. Inlet velocity is taken as uniform flow.As estimating angular velocity is difficult for a turbine, I have taken different Tip Speed Ratio (TSR) and then calculated the angular velocties by using a constant flow velocity.

I have taken moment about z axis(flow direction), and about orgin which is the origin of the turbine(Report>Result Reports>Forces>Moments). This moment multiplied with the angular velocity x 3 times(for three blades in periodicity) should give the extracted power.

As seen in experimental studies, the power coefficient increases with TSR, reaches a maximum and them starts to decrease. Unfortunately, the curve I am gettin is quite different. It is increasing with larger TSR's. I have tried with TSR upto 8.

I am perplexed why this is happening. Any suggestions?

Regards

Zaqie Reza

[tony00]

Hi,
I have a similar problem. Is your Fluent predicted torque higher or lower than you would expect? In my case I am getting a much higher torque than expected.

Is there anyone out there who could give us a hint?

Regards

[Zaqie]

Hi

I think good results depend on the mesh quality. Check your mesh sqewness.

I am trying to block and do meshing. Let me see where it takes me.

Also see the link

http://www.cfd-online.com/Forums/ans...tml#post248191

regards

zaqie