Help With Tidal Turbine Simulation

 Register Blogs Members List Search Today's Posts Mark Forums Read

January 19, 2014, 12:30
Help With Tidal Turbine Simulation
#1
New Member

Nick Osbourne
Join Date: Sep 2013
Posts: 2
Rep Power: 0
Hello everyone,

I am attempting to simulate a horizontal axis tidal turbine in Ansys CFX. The process I have taken so far is below:

I created a simple geometry in Solidworks and imported into Ansys Geometry. I created the fluid domain and used boolean subtract for the turbine. I've attached an image of the fluid domain, which consists of two stationary domains (inlet and outlet) and one rotating domain. For boundary conditions I have:

Inlet: Inlet
Outlet: Outlet
Outside walls: Free slip walls
Turbine walls: No slip walls
Interfaces between stationary and rotating domains: Frozen Rotor

I have run both steady state and transient scenarios. I am using the Shear Stress Transport turbulence model. I have a constant inflow velocity and have set angular velocities for different cases to achieve specific tip speed ratios.

In CFX-Post I utilized the integrated torque function on all of the turbine walls. Then to get power you simply multiply the torque by the angular velocity. I've attached an image of the streamlines from one of the steady state scenarios.

My Questions/Issues are:
1) My Power output that I am reading is far too high (I'm getting Cp values around 6.5)
2) With the transient solution I would expect to be able to create an animation and see the turbine domain rotate. I am however seeing no visual change between timesteps. I am wondering if this is due to the coordinate frame of reference being linked to the rotating reference instead of the stationary's?

I feel like I am either missing an important step, or am misunderstanding a step I have already made. Is there someone with experience that could shed some light for me?

Much appreciated
Attached Images
 Turbine CFD Domain.jpg (20.8 KB, 31 views) Turbine Streamlines.jpg (46.3 KB, 32 views)

 January 19, 2014, 17:52 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,993 Rep Power: 107 Accuracy is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F To get the rotor to rotate in a transient simulation you need to use Transient Rotor Stator in the interface parameters. Frozen rotor assumes the rotor is frozen (obviously).

 January 20, 2014, 13:14 #3 New Member   Nick Osbourne Join Date: Sep 2013 Posts: 2 Rep Power: 0 Hello Ghorrocks, thanks for the reply. I have read through some of the FAQ, in particular the "Why are my results inaccurate" section, and found them quite helpful. Thanks for the tip about the Transient Rotor Stator option, I hadn't noticed this was available for transient solutions. I will update once I do some trouble shooting.

 Tags ansys, cfx, tidal, turbine

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post be_inspired OpenFOAM 51 January 13, 2016 05:59 vincentwks ANSYS 0 April 10, 2012 04:27 altomos CFX 7 March 31, 2011 10:08 moca CFX 1 July 25, 2009 06:48 mehrdadeng CFX 0 March 31, 2009 05:08

All times are GMT -4. The time now is 17:32.