# K-ε model in ANSYS

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 September 18, 2011, 04:30 K-ε model in ANSYS #1 New Member   Join Date: Sep 2011 Posts: 1 Rep Power: 0 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?

 September 19, 2011, 03:40 #2 Member     Omid Seyedashraf Join Date: May 2010 Location: Iran Posts: 46 Rep Power: 8 for example : k= 1.5(U_average*I)^2 ε = C_u^0.75*(K/l)^1.5

 September 22, 2011, 12:20 #3 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,299 Blog Entries: 6 Rep Power: 43 take a look on turbulence modelling book by wilcox

 September 22, 2011, 21:25 #4 New Member   John Moore Join Date: Oct 2010 Posts: 9 Rep Power: 8 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

 September 27, 2011, 11:55 #5 New Member   Ayothi Ramanathan Join Date: Sep 2011 Posts: 28 Rep Power: 7 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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