# turbulance parameter

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 January 3, 2014, 07:49 turbulance parameter #1 New Member   razieh anari Join Date: May 2013 Posts: 6 Rep Power: 5 Hi 1- what is the mean of pressure in flow 3d? dynamic or static? 2- what is the mean of turbulent energy? is the same kinetic energy of turbulence? k=0.5(u'2+v'2+w'2) u', v', w' are Average volatility. thanks a lot .

 January 3, 2014, 13:57 #2 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 9 1) p = static pressure. 2) turbulent energy = turbulent kinetic energy, TKE, just as you have guessed: k = 0.5(u'^2+v'^2+w'^2). TKE has units of L^2/t^2 (J/kg in SI). On the Simulation Manager tab (and in Analyze > Probe > General History Data) there is an output called "mass-averaged turbulent energy": MTKE = sum(k*mass)/sum(mass). In FLOW-3D variables, MTKE = sum(k*rho*f*vf*del)/sum(rho*f*vf*del). Rho is local fluid density, f is local fluid fraction (volume fluid in cell/open volume in cell), and vf is local volume fraction (open volume in cell/total volume in cell), and del is the cell volume dx*dy*dz. The term rho*f*vf*del = mass of fluid in cell. zhouyu3092070 and mina00 like this.

 April 26, 2014, 14:30 turbulent dissipation #3 New Member   razieh anari Join Date: May 2013 Posts: 6 Rep Power: 5 hello, thank you for your answers: please tell me, what is the differences between turbulent energy and turbulent dissipation? turbulent dissipation is reynolds stresses?if not, what's its formula? i need u' , v' , w' , can i have these from out put result? Milad h likes this.

July 13, 2014, 06:40
#4
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mh
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Quote:
 Originally Posted by razieh anari hello, thank you for your answers: please tell me, what is the differences between turbulent energy and turbulent dissipation? turbulent dissipation is reynolds stresses?if not, what's its formula? i need u' , v' , w' , can i have these from out put result?
hi razieh
(i need u' , v' , w' , can i have these from out put result?)
can you solve this problem?

 July 14, 2014, 11:00 #5 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 9 You can get u', v', w' from LES turbulence modeling. You can't get the velocity fluctuation components separately from RANS turbulence (like k-e or k-w). Milad h likes this.

July 14, 2014, 17:11
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mh
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Quote:
 Originally Posted by JBurnham You can get u', v', w' from LES turbulence modeling. You can't get the velocity fluctuation components separately from RANS turbulence (like k-e or k-w).
Hi JBurnham
thank u
but, How do i get u', v', w' from output??

 July 18, 2014, 13:17 #7 Senior Member   Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 9 Use FlowSight (the new post-processor that comes with v11). It can calculate the time-mean velocity values u_, v_, w_ in all cells over a steady-state flow. Then have FlowSight perform an arithmetic operation to subtract: u, v, w - u_, v_, w_ = u', v', w'. From the new fluctuation variables, you can find the max/min, 95th percentile, etc. Milad h likes this.

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