Dear ENVI-met,

1. Model basic information: grid 50 × 50 × 30, grid resolution is 10, 10, 2. The building is located in the center of the model and measures 300 meters by 300 meters by 25 meters.

2. Basic information of calculation: the summer wind speed is 2.8m / s (at a height of 10 meters), the initial wind direction is 202.5 °, and the ground roughness is 0.22.

3. The output result is expected:

V0 = 2.8 × (1.5 / 10) ^ 0.22 = 1.84m / s (initial wind speed at 1.5 meters)

Ri = Vi / V0 When Vi is 1.84m / s, Ri = 100% (the wind speed ratio of the initial wind speed at 1.5 meters)

4. Actual output:

1) When Ri is 100%, the corresponding wind speed is 2.27m / s instead of 1.84m / s;

2) When the wind speed at the height of 1.5 meters is 1.84m / s, the corresponding wind speed ratio is about 82% instead of 100%;

What is the reason for the difference? Does it have anything to do with nested grids?

Best wishes,

Pat

## About wind speed to wind speed ratio

### Re: About wind speed to wind speed ratio

Hi Pat,

Nesting grids of course influence your results. I don't understand your model area... where is the building? Did you cut the results in Leonardo?

Why don't you create a super simple model area without buildings and nesting grids for such analysis?

Best regards,

Tim

Nesting grids of course influence your results. I don't understand your model area... where is the building? Did you cut the results in Leonardo?

Why don't you create a super simple model area without buildings and nesting grids for such analysis?

Best regards,

Tim

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