Wind gradient calculation

[TAW_Impalor]

Hello Devs!

 

What formula do you use to calculate true wind speed at deck height (60ft)? I am trying to make sense of the LSO screen's wind over deck numbers.

 

I made a simple mission with CV going upwind at 15 knots, and depending on true wind speeds I see the following WOD on LSO screen:

 

W33 WOD

3 19

5 22

10 30

15 38

20 45

 

This implies the following true wind speeds at deck height, along with ratio to wind at 33ft (ignoring angled deck for now):

 

W60 Ratio

4 1.33

7 1.40

15 1.50

23 1.53

30 1.50

 

The ratios seem high and, moreover, depend on the wind speed itself. I would expect some constant proportion, based on wind gradient theory here: https://en.wikipedia.org/wiki/Wind_gradient

 

I noticed in the ME wind at 1600 ft automatically depends on wind at 33 ft at roughly 2.1:1 ratio. This implies Hellmans exponent a = 0.19. Applying this gradient to 60 ft we should be getting

 

W60/W33 = (60/33)^0.19 = 1.12, i.e. wind at deck height must me stronger than wind at 33ft by only 12%, not 50%!

 

Leaving it as is seems unrealistic.

 

Thanks!

[Frederf]

DCS wind model is linear interpolation to zero at some negative altitude (-4000')?

[TAW_Impalor]

DCS wind model is linear interpolation to zero at some negative altitude (-4000')?

 

This is not what I see on LSO screen! If it were linear, the wind over deck would be much smaller.

[Fri13]

It is challenging to really even understand well the wind modeling in DCS at this moment. And as it is going very likely change once the new weather system comes out, I wouldn't spend much time to try learn the current one functionality.

[Yo-Yo]

Hello Devs!

 

What formula do you use to calculate true wind speed at deck height (60ft)? I am trying to make sense of the LSO screen's wind over deck numbers.

 

I made a simple mission with CV going upwind at 15 knots, and depending on true wind speeds I see the following WOD on LSO screen:

 

W33 WOD

3 19

5 22

10 30

15 38

20 45

 

This implies the following true wind speeds at deck height, along with ratio to wind at 33ft (ignoring angled deck for now):

 

W60 Ratio

4 1.33

7 1.40

15 1.50

23 1.53

30 1.50

 

The ratios seem high and, moreover, depend on the wind speed itself. I would expect some constant proportion, based on wind gradient theory here: https://en.wikipedia.org/wiki/Wind_gradient

 

I noticed in the ME wind at 1600 ft automatically depends on wind at 33 ft at roughly 2.1:1 ratio. This implies Hellmans exponent a = 0.19. Applying this gradient to 60 ft we should be getting

 

W60/W33 = (60/33)^0.19 = 1.12, i.e. wind at deck height must me stronger than wind at 33ft by only 12%, not 50%!

 

Leaving it as is seems unrealistic.

 

Thanks!

 

Thank you for your observation. It's not the atmosphere matter - the point where the wind speed is sampled for LSO was much higher than the deck altitude.

Edited October 7, 2020 by Yo-Yo

[TAW_Impalor]

Thanks for your reply! If WOD should ideally be 25-30 knots, what value on LSO screen should we target in this case?

[Yo-Yo]

Thanks for your reply! If WOD should ideally be 25-30 knots, what value on LSO screen should we target in this case?

 

Just as you estimated.

[=4c=Nikola]

Thank you for your observation. It's not the atmosphere matter - the point where the wind speed is sampled for LSO was much higher than the deck altitude.

 

You say "was much higher". Does that mean it's set to correct altitude now?

[BarTzi]

You say "was much higher". Does that mean it's set to correct altitude now?

 

Probably not in our build

[Yo-Yo]

Probably not in our build

 

Just fixed, and probably will be in the next update.

[BarTzi]

I think this was changed in the update today. impalor, can you confirm?