CMS-Flow:Wind Pressure

Wind

In CMS-Flow the wind shear stress is calculated as

     $\tau _{Wi}=\rho _{a}C_{d}|W|W_{i}$ 

The wind drag coefficient $C_{d}$ is calculated using the Hsu (1988)

     $C_{d}={\biggl (}{\frac {\kappa }{14.56-2\ln W}}{\biggr )}^{2}$ 

For measurements of wind speed made at heights other than 10 m, an approximation of the 10-m wind speed is (Shore Protection Manual 1984)

     $W=W_{z}{\biggl (}{\frac {10}{z}}{\biggr )}^{1/7}$ 

Pressure

The atmospheric pressure is included in the momentum equations as an additional pressure gradient term

     ${\frac {1}{\rho _{0}}}{\frac {\partial p_{a}}{\partial x_{j}}}$ 

Symbol Index

Symbol	Description	Units
$\tau _{W}$	Wind shear stress	Pa
$\rho _{a}$	Atmospheric density (~1.2 kg/m^3)	kg/m^3
$C_{d}$	Wind drag coefficient	none
$W$	10-min averaged wind speed at 10 m above the sea surface	m/sec
$\theta$	Wind direction	m/sec

References

• Hsu, S.A. (1988) Coastal meteorology. Academic Press, San Diego, CA.

• Shore Protection Manual (1984) 4th ed., 2nd Vol, U.S. Army Engineer Waterways Experiment Station, U.S. Government Printing Office, Washington, DC.

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