Unrealistic high wind speed

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Ila
Posts: 25
Joined: Sun Sep 16, 2018 4:22 pm

Unrealistic high wind speed

Postby Ila » Fri May 15, 2020 1:30 pm

Hello Envi_met team,
I'm not able to explain the wind behavior: the speed is up to 4.4 m/s at the building corner. (screen attached here).
I've increased the open space around the buildings, but this behavior persists.

Last test dimension
Simple forcing= wind speed: 1,7 m/s, direction: 55°
Model area 175x75x40 + 3 nesting grid, telescoping factor, 1m resolution.
Space between building and model borders = 20m
Max h= 30m
Difference between top and model= 45m

Have you got some suggestions? Thank you very much!
Best regards
Ilaria
Attachments
V14 175.png
Wind speed at 14. Similar also at 11 and 17
Vv14 175.png
Wind speed at 14. Similar also at 11 and 17

Tim
Posts: 1401
Joined: Mon May 15, 2017 3:46 pm

Re: Unrealistic high wind speed

Postby Tim » Fri May 15, 2020 2:06 pm

Hi Ilaria,

I think that it looks pretty realistic. The wind cannot go anywhere else so it is pressed around and over the building and thus becomes faster. You could make it more realistic by increasing the model area surrounding significantly, maybe 250x200 grid cells in your resolution only with open space. Wind flow could then start earlier to move around the building and the wind speeds will not get that high. That is why we always recommend to use a lot of open space especially at the inflow border.

Best regards,
Tim

Ila
Posts: 25
Joined: Sun Sep 16, 2018 4:22 pm

Re: Unrealistic high wind speed

Postby Ila » Sun May 17, 2020 10:13 am

Thank you Tim for your explanation and suggestion, now it makes sense to me.
Best regards

Ilaria


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