REYNOLDS STRESS MODEL

1
REYNOLDS STRESS MODEL

• Pauli Paasonen
• Larisa Sogacheva
• Ville Vakkari

2
Reynolds stress (1)

• Reynolds stress the mean forces (per unit area)
  imposed to the mean flow by turbulent fluctuation
  
• It arrises from the nonlinear advection term when
  Navier-Stokes equations are Reynolds decomposed
• and Reynolds averaged
  .
• The general form of the Reynolds stress tensor is

3
Reynolds stress (2)

• Cinematically, the velocity correlation
  represents the momentum flux in the direction
• across a plane perpendicular to direction
  ,
• or the momentum flux in the direction
  across a plane perpendicular to direction
• In a turbulent flow, the divergence of the
  Reynolds stress are of leading order in the mean
  momentum budgets. Typically, it is several orders
  of magnitude larger then the viscous stress.
• In the boundary layer, the most important
  Reynolds stresses are vertical fluxes of
  horizontal momentum.

4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
Fluent's k-e, RNG k-e and RSM models compared
with measurements
Flows in different shapes of combustion
chambers Fluent version 4.3.2, year 1997 Risto
Huhtanen, Isotermisen poltinvirtauksen laskenta,
VTT julkaisuja - publikationer 827, 1997
8
(No Transcript)
9

• RSM gives slightly better results, though
• setting correct boundary conditions harder
• convergence may be difficult to achieve
• discretization has to be done carefully

10
Cyclone separator
http//www.qnet-cfd.net/workshop/4th/pdf/ws4-07.pd
f, 11.12.2006
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)