scale
 

hi guys i am working in an automobile firm. i am trying to calculate coefficient of drag and compare it to experimental drag values. the experimental testing is done in 1/3 rd scale model. now which one is more accurate way of comparing it to experimental results. 1 keeping the cad geometry dimension as in the wind tunnel experiment (1/3 rd model) 2 keeping the cad geometry of full size vehicle without any reduction in dimensions.

Re: scale
 

use the wind tunnel geometry

Re: scale
 

hi dirk

let me put my question in a different way. i have wind tunnel results using a scale model and i have done my Fluent analysis on this scale model; and now i wish to model the full size vehicle with Fluent. question is what values of turbulence paramters i should use while doing the full scale model analysis.

in this whole analysis only the vehicle dimensions are goint to change the tunnel dimension will remain the same. bye

Re: scale
 

If the channel dimensions are equal in both simulations, the turbulence parameters don't need to be changed. I would use a velocity inlet and specify turbulence intensity (measured in experiment) and hydraulic diameter. You don't need to change these parameters as the inflow conditions should be independent from the model in the wind tunnel, if the distance between both is big enough.

Dirk

Re: scale
 

hi dirk

thanks a lot i got my answer