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-   -   K-ε model in ANSYS (http://www.cfd-online.com/Forums/main/92557-k-model-ansys.html)

shirley September 18, 2011 04:30

K-ε model in ANSYS
 
Hi,
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?

seyedashraf September 19, 2011 03:40

for example :
k= 1.5(U_average*I)^2
ε = C_u^0.75*(K/l)^1.5

Far September 22, 2011 12:20

take a look on turbulence modelling book by wilcox

Joke September 22, 2011 21:25

Hi,shirley

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

ayothicfd September 27, 2011 11:55

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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