CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

how to use finite-rate/eddy-dissipation?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   September 28, 2007, 00:41
Default how to use finite-rate/eddy-dissipation?
  #1
muro
Guest
 
Posts: n/a
Dear friends,

I've got problem on using finite-rate/eddy-dissipation in the non-premixed combustion simulation. By patching some zones to the high temperature value, I also found that the combustion is not occurred in the chamber. So, please help me to fix this problem.

Thank you very much.

Muhad
  Reply With Quote

Old   July 26, 2012, 07:11
Default
  #2
New Member
 
Prakash Ghose
Join Date: Dec 2011
Posts: 29
Rep Power: 5
pghoseju is on a distinguished road
The Pressure-Based coupled algorithm which is a good alternative to density-based solvers of ANSYS
Fluent when dealing with applications involving high shear flow was employed.
The following spatial discretization schemes were used:
 For gradient the least square cell based method was employed; and
 The second order upwind scheme was employed for density, momentum, modified turbulent
viscosity and the energy equations.
Under relaxation factor of 0.8 was used for the species, energy and density while a value of 0.6 was
applied for the momentum, turbulent kinetic energy, turbulent kinetic dissipation rate and turbulent
viscosity.
In order to monitor convergence as the calculations (iterations) progressed, the following residual
quantities: continuity, x-velocity, y-velocity, energy, turbulent kinetic energy, k, turbulent dissipation
rate, , and all the species were monitored. The absolute convergence criteria which were set for these
quantities are: continuity 10−3, x-velocity 10−3, y-velocity 10−3 and energy 10−4 for cold flow
calculations. For the reacting flow computations, the initial temperature field was patched to initiate the
combustion process. The absolute convergence criteria for the species were then lowered to 10−6.
The initial calculations were performed assuming that all properties except density were constant.
Using constant transport properties (viscosity, thermal conductivity, and mass diffusion coefficients) is
acceptable here because the flow is fully turbulent. The molecular transport properties will play a minor
role compared to turbulent transport. The assumption of constant specific heat, in contrast, has a strong
effect on the combustion solution, and this property was represented with a polynomial function during
the reacting flow computation.
The solution was then initialized. Thereafter, the Full Multigrid (FMG) feature was run. Full
Multigrid initialization often facilitates an easier start-up, thereby, obviating the need for Courant-
Friedrichs-Lewy (CFL) condition ramping, consequently reducing the number of iterations required for
convergence.
pghoseju is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Control Volume , Finite Volume, Finite Control Volume, Finite Element Method technocrat.prakash Main CFD Forum 1 April 24, 2010 19:24
CFX12 rif errors romance CFX 4 October 26, 2009 14:41
Finite volumes vs. finite elements: applications Lionel S. Main CFD Forum 10 January 22, 2007 11:51
Dissipation rate access K. Kevala FLUENT 0 July 14, 2004 11:11
calculation of (turbulent) dissipation energy ? max Main CFD Forum 3 August 18, 1999 09:42


All times are GMT -4. The time now is 16:58.