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Stable atmospheric boundary layer over the water

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Old   April 27, 2021, 04:39
Default Stable atmospheric boundary layer over the water
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Lorenzo
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Goodmorning everyone

I wanted to set up the simulation of a sailboat. I'm setting up a case with interFoam and at the moment I am considering the various "pieces" of the simulation separately.

I'm having difficulty setting the "atmospheric" part. I have two different speeds: uAir and uWater. To set the airspeed I wanted to set up an atmospheric boundary layer. The reference equations is the following:
u = \frac{u^*}{\kappa} \ln \left( \frac{z - d + z_0}{z_0} \right)
u^* = \frac{u_{ref} \kappa}{\ln\left(\frac{z_{ref} + z_0}{z_0}\right)}
k = \frac{(u^*)^2}{\sqrt{C_\mu}} \sqrt{C_1 \ln \left( \frac{z - d + z_0}{z_0} \right) + C_2}
\epsilon = \frac{(u^*)^3}{\kappa (z - d + z_0)} \sqrt{C_1 \ln \left( \frac{z - d + z_0}{z_0} \right) + C_2}
\omega = \frac{u^*}{\kappa \sqrt{C_\mu}} \frac{1}{z - d + z_0}
Reference in OF user guide
Since @ z = 0 the speed is not zero but it is that of the sea (uWater), I use as uRef = uAir-uWater and once the maximum speed profile is obtained again uWater. Hence I could not used the atmBoundaryLayerInletVelocity BC.

I write the resulting wind profile in a .csv file and it is used as boundary condition for the air inlet.

For the others boundary conditions I used this tutorial as a reference.
I know that I should have used the csv technique also for turbulent boundary conditions but doing the calculation by hand, on the sea where z0 = 0.0002 and at a height z = 0, omega (or epsilon) reaches very high values.
So the only differences with the tutorial are:
  • I cannot impose the ground BC since there is the sea
  • I use the .csv file for U
  • I'm using interFoam instead of simpleFoam

I tried using setExprFields in order to impose the wind profile as an initial condition for the whole domain but it made no difference. The main problem is that near the outlet the turbulence variables increase significantly and this slow down the air near the sea.
This is the result I obtain:
https://gph.is/g/4gMJ9VL

Do you have some suggestions?
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atmospheric bl, interfoam, sailboat, wind

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