# turbulence

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 July 4, 2005, 13:32 turbulence #1 wilson Guest   Posts: n/a hi guys in the wind tunnel analysis i have one doubt i have a car in a box just like wind tunnel. i am giving some turbulence values in the form of turbulence and intensity scale at inlet. now the question is suppose i am reducing the scale ratio of my car model keeping the tunnel dimensions same, then should i change the value of turbulence quantities. for instance, initially i keep car in tunnel and give turbulence quantity say x, now my tunnel size is same but car shape is reduced to 1/3 scale should i change the turbulence quantity to x/3

 July 4, 2005, 19:09 Re: turbulence #2 Glenn Horrocks Guest   Posts: n/a Hi, Good question Wilson. Have a look in a textbook under non-dimensionalisation theory. I think you will find it is not possible to scale everything, usually you can scale a model keeping one non-dimensional number the same (eg Reynolds Number), but the other non-dimensional numbers have to change. This means you have to choose what is the most important parameter to keep constant during scaling. But I am not sure that is what you are asking. Can you explain what you are trying to do a bit more? Regards, Glenn Horrocks

 July 5, 2005, 14:40 Re: turbulence #3 wilson Guest   Posts: n/a hi Glenn i am simply focusing on turbulence at the inlet. if the dimensions of wind tunnel remain the same, should i decrease the turbulence with the same ratio as that of vehicle. i feel that the turbulence parameters remain the same irrespective of the vehicle dimensions.

 July 5, 2005, 18:55 Re: turbulence #4 Glenn Horrocks Guest   Posts: n/a Hi, So you have wind tunnel results using a scale model and you have done your CFX model on this scale model; and now you wish to model the full size thing with CFX? In that case it appears you are not using non-dimensional scaling anyway as the Reynolds number of the full sized thing will be different to the model. Shouldn't you use the turbulence levels typical of the real situation, rather than the wind tunnel? For instance external aerodynamics of vehicles need quite low levels of incoming turbulence in general. Regards, Glenn Horrocks

 July 7, 2005, 10:21 Re: turbulence #5 jorge sancho Guest   Posts: n/a Look at the turbulence quantity dimensions, to have them adimensional. Ex, if you use lenght scale as a turbulence paramenter, you should scale it with your caracteristic dimension (lenght of the car). But others are non dimensional, like viscosity ratio.

 August 9, 2005, 10:57 Re: turbulence #6 Andrea Guest   Posts: n/a

 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 Mohsin FLUENT 2 October 3, 2016 14:18 rizhang CFX 2 April 22, 2016 07:22 Eric FLUENT 1 March 7, 2012 05:30 Wen Long Main CFD Forum 3 May 15, 2009 09:52

All times are GMT -4. The time now is 04:29.

 Contact Us - CFD Online - Privacy Statement - Top