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Search: Posts Made By: ghorrocks
Forum: CFX June 24, 2016, 06:39
Replies: 50
Views: 11,052
Posted By ghorrocks
Do another simulation with the stationary domain...

Do another simulation with the stationary domain boundary twice the distance away. If it is not any different to your first case then your first case is fine.

You can also do this by halving the...
Forum: CFX May 17, 2016, 07:20
Replies: 50
Views: 11,052
Posted By ghorrocks
Have you looked at the accuracy FAQ:...

Have you looked at the accuracy FAQ: http://www.cfd-online.com/Wiki/Ansys_FAQ#Why_are_my_results_inaccurate.3F

There is not a single thing required for accurate results, many things need to be...
Forum: CFX August 28, 2015, 17:13
Replies: 50
Views: 11,052
Posted By ghorrocks
There are many things other than bonuary...

There are many things other than bonuary proximity which can affect accuracy:
http://www.cfd-online.com/Wiki/Ansys_FAQ#Why_are_my_results_inaccurate.3F
Forum: CFX August 14, 2015, 08:25
Replies: 50
Views: 11,052
Posted By ghorrocks
If you model 120 of the full thing you will then...

If you model 120 of the full thing you will then have to multiply the torque by 3 to get the total torque of the device.
Forum: CFX July 24, 2015, 02:59
Replies: 50
Views: 11,052
Posted By ghorrocks
There is no need to define a velocity loss. It...

There is no need to define a velocity loss. It will be part of the solution when the solver conserves mass and momentum so an accurate simulation will already have it.

What is your solver momentum...
Forum: CFX April 20, 2014, 06:35
Replies: 50
Views: 11,052
Posted By ghorrocks
Try the fluent forum for help on this. But...

Try the fluent forum for help on this.

But if you are looking for derivatives of pitching moments and similar coefficients it does not sound like you want to do a 6DOF simulation. This sounds like...
Forum: CFX April 14, 2014, 20:37
Replies: 50
Views: 11,052
Posted By ghorrocks
No - have a think about what determines the...

No - have a think about what determines the steady state operating speed.

The rotor will not accelerate or decelerate when there is no net torque on the rotor. There will be zero net torque when...
Forum: CFX April 14, 2014, 18:53
Replies: 50
Views: 11,052
Posted By ghorrocks
Yes, I do not recommend this. It is much easier...

Yes, I do not recommend this. It is much easier to run a series of fixed rotation speeds then interpolate to find the operating speed based on the torque output of each rotation speed.

But if you...
Forum: CFX October 21, 2013, 17:27
Replies: 50
Views: 11,052
Posted By ghorrocks
You can make the rotational speed a function of...

You can make the rotational speed a function of torque but it significantly complicates the simulation. For most applications it is better to run a sweep of several rotational speeds and interpolate...
Forum: CFX October 20, 2013, 19:55
Replies: 50
Views: 11,052
Posted By ghorrocks
I do not have time to check your simulation in...

I do not have time to check your simulation in detail.

Your assumption that too coarse a mesh cannot result in the generated torque being too high is wrong. It certainly can, so I definitely would...
Forum: CFX October 15, 2013, 19:47
Replies: 50
Views: 11,052
Posted By ghorrocks
Think frames of reference, not objects. The only...

Think frames of reference, not objects. The only rotating thing (which will go in a rotating frame of reference) is the blades. Everything else is stationary. So stick the blades in rotating frame of...
Forum: CFX October 12, 2013, 06:37
Replies: 50
Views: 11,052
Posted By ghorrocks
That depends on what you are modelling. If you...

That depends on what you are modelling. If you just want the steayd performance then steady state.

Also - you appear to have 1/3 periodicity. Why not model just 1/3 of this?
Forum: CFX October 10, 2013, 20:28
Replies: 50
Views: 11,052
Posted By ghorrocks
Torque has nothing to do with wind speed or...

Torque has nothing to do with wind speed or rotation speed. You can get the torque from an expression like torque_x()@BladeSurface, assuming the rotor is on the x axis and the name of the wall...
Forum: CFX October 10, 2013, 17:19
Replies: 50
Views: 11,052
Posted By ghorrocks
Your domain configuration is fine. You have some...

Your domain configuration is fine. You have some other problem causing the inaccuracy - http://www.cfd-online.com/Wiki/Ansys_FAQ#Why_are_my_results_inaccurate.3F

Yes, you can set the rotation...
Forum: CFX September 30, 2013, 18:25
Replies: 50
Views: 11,052
Posted By ghorrocks
Sliding mesh allows you to connect two meshes...

Sliding mesh allows you to connect two meshes which are sliding past one another and multiple frames of reference allows you to do simulations where different parts of the simulation are in different...
Forum: CFX September 10, 2013, 05:51
Replies: 50
Views: 11,052
Posted By ghorrocks
This simulation is quite simple to set up. ...

This simulation is quite simple to set up.

First of all - forget immersed solid. That will not be appropriate for a wind turbine model.

For the rotating frame of reference stuff have a look at...
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