How to scale the ABL velocity profile?

Ahmed Hassan · November 19, 2017, 07:39

Hello all,

I am modelling the flow around a lowrise building. I use the ABL and I have been using 1:1 scale since I started. However, I would like now to reduce my model to a 1:100 scale and I should reduce my ABL logaritmic velocity profile as a consequence.

However, since it is not a linear velocity profile, maybe the reduction could not be exactly proportional. I mean, if I used Zref=10 and Uref=10, maybe the reduction wouldn't be Zref=0.1 and Uref=0.1, but Uref=0.08, or something like that, since it is a logaritmic profile instead of a linear profile.

I know that the easier way would be to use linear reduction and forgeting about it. But I would like to do a good work.

I hope you could provide me some information about it.

Thanks in advance.

FMDenaro · November 19, 2017, 07:47

Why don't you start using the velocity profile law in non-dimensional form? Then you can get any scaling you want using your physical quantities.

November 19, 2017, 07:39	How to scale the ABL velocity profile?	#1
Ahmed Hassan New Member Ahmed Hassan Join Date: Nov 2017 Posts: 10 Rep Power: 7	Hello all, I am modelling the flow around a lowrise building. I use the ABL and I have been using 1:1 scale since I started. However, I would like now to reduce my model to a 1:100 scale and I should reduce my ABL logaritmic velocity profile as a consequence. However, since it is not a linear velocity profile, maybe the reduction could not be exactly proportional. I mean, if I used Zref=10 and Uref=10, maybe the reduction wouldn't be Zref=0.1 and Uref=0.1, but Uref=0.08, or something like that, since it is a logaritmic profile instead of a linear profile. I know that the easier way would be to use linear reduction and forgeting about it. But I would like to do a good work. I hope you could provide me some information about it. Thanks in advance.

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November 19, 2017, 07:47		#2
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,290 Rep Power: 67	Why don't you start using the velocity profile law in non-dimensional form? Then you can get any scaling you want using your physical quantities.