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Old   September 18, 2011, 04:30
Question K-ε model in ANSYS
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I am trying to build a K-ε model in ANSYS to simulate turbulent air flow over two flat plates. Apparently I don't have a sound understanding of K-ε model, so when it required values of K and ε, I was a bit confused. How could I get these values?
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Old   September 19, 2011, 03:40
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for example :
k= 1.5(U_average*I)^2
ε = C_u^0.75*(K/l)^1.5
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Old   September 22, 2011, 12:20
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take a look on turbulence modelling book by wilcox
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Old   September 22, 2011, 21:25
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You can calculate TurbK.E(K) and dissipation (ε) by
K = 0.5*(u'^2+v'^2+w'^2)
ε = (C_mu^0.75)*(K^1.5)/(Kappa*L)
; C_mu = 0.09 ,generally
Kappa = 0.4
L = Lenght
{u', v', w'} = turbulence intensity*free stream velocity

For example, assume
turbulence intensity = 2%
free stream velocity = 6m/s
Lenght = 5mm
u' = v' = w' = 2%*6 = 0.12
K = 0.5*3*0.12 = 0.0216
ε = (0.09^0.75)*(0.0216^1.5)/(0.4*0.005) = 0.26
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Old   September 27, 2011, 11:55
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Hello shirley,
Based on theoretical aspects, Most of flow analysis will be considering in K-ε model because the flow at inlet of domain is considered as the fully developed flow. This topic related material will be easily available in Ansys help in the topic named as "Basic assumptions".
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