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A roughness-dependent model

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Revision as of 15:18, 19 June 2007 by R.absi (Talk | contribs)
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Two-equation eddy viscosity model

\nu _t  = C_{\mu} {{k^2 } \over \varepsilon }

where:  C_{\mu} = 0.09

One-equation eddy viscosity model

\nu _t  = k^{{1 \over 2}}  l 

Algebraic eddy viscosity model

\nu _t(y)  = {C_{\mu}}^{{1 \over 4}} l_m(y) k^{{1 \over 2}}(y) 

l_m is the mixing length.

Algebraic model for the turbulent kinetic Energy

k^{{1 \over 2}}(y) = {1 \over {C_{\mu}}^{{1 \over 4}}}  u_\tau  e^{\frac{-y}{A}} 

u_\tau is the shear velocity and A a model parameter.

Algebraic model for the mixing length, based on (4) [Absi (2006)]

l_m(y) = \kappa \left( A - \left(A - y_0\right) e^{\frac{-(y-y_0)}{A}} \right)

\kappa = 0.4, y_0 is the hydrodynamic roughness

the algebraic eddy viscosity model is therefore

\nu _t(y)  = \kappa \left( A - \left(A - y_0\right) e^{\frac{-(y-y_0)}{A}} \right)
 u_\tau  e^{\frac{-y}{A}}  


  • Absi, R. (2006), "A roughness and time dependent mixing length equation", Journal of Hydraulic, Coastal and Environmental Engineering, Japan Society of Civil Engineers, (Doboku Gakkai Ronbunshuu B), Vol. 62, No. 4, pp.437-446.

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