[bluenail]

First of all,

sorry for poor writing

Now I am studying coal gasification.

it has similar shape like this photo
(I can't upload my own figure bcz of policy)



inlet port has a angle to make a swirl

Basic method of this calculation is like this

1. Pressure based solver
2. steady sate
3. k-e RNG turbulence model
4. Almost discrete scheme is quick
(1st, 2st order also have a good solution, but temperature profile is bad ^^)
5. adapt stochastic tracking for the simulation

Main problem:

after residual stable, temperature contour gradually changed ㅜㅡ

hahahahahahahahahahahaha

Residual is ok, and temperature of each space is ok

But figure of temperature make me crazy

in MIT paper
[Multiphysics Simulations of Entrained Flow Gasification. Part II:
Constructing and Validating the Overall Model]

they say like this

A possible explanation for this observation is that it becomes
increasingly difficult to find a steady-state solution to the
inherently transient problem of turbulent two-phase reacting
flows in gasifiers as increasingly finer structures are captured
though mesh refinement.

-> mesh number cause problem for solution

But in my case, mesh number is little bit small,

almost under 200,000 mesh

I thought basic cause of this simulation is

unstable of turbulence....

bcz k, e value of turbulence defined the reaction rate

But how could I stable turbulent calculation ????

i tried this method
->
http://www.cfd-online.com/Forums/flu...tml#post122278

But it fail too

hahaha

is there anyone know how to stabilize the turbulence calculation during coal combusiton????