[ardismo]

Hi;

Im trying to simulate gas-solid cyclone separator used in cement industry. I will mention about boundary conditions and operating conditions. I need some ideas to solve more accurate , quicker solution with same accuracy or to correct my mistakes. These will helpful for me and for others who has need help on this subject.

operating conditions ;

- It is a multilevel system consists of 5 cyclone levels.
- very high dust loading particle.( 0.2 kg particle/ m^3 air)
- 12 to 20 m/s inlet velocity
- nearly 700 m^3 control volume

Boundary Conditions;

1 - velocity inlet
2 - pressure outlet or outflow

****normally outlet is not open to atmosphere. Gas always goes to upper cyclone level. So there must not be reverse flow.

3 - wall ,of cyclone body
4 - wall of dust outlet

Setup settings;

1 - Mesh count : 160K , 700K , 3M, 8M , 30M
2 - Eularian multiphase model with dense DPM option.
3 - Reynols stress model with linear pressure strain option
4 - pressure-velocity coupling scheme;
----Simple : there is no need to set a CFL but long computational time.
----Coupled : I have enough memory. But in Fluent theory manual, it says below 10 is not recommended for Courant number. And if you can't choose wright CFL in coupled , solution monitors fluctuates a lot.
5 - Spatial Discretization ;
---- Gradient :Green Gauss node based
---- Pressure : Presto
---- others : second or third order upwind---- solution monitors fluctuates a lot. So it says you to switch time-dependent simulation.
6 - Under Relaxation Factors : 0.5 for all parameters
7 - Initialization : Normal + FMG with 7 levels


QUESTIONS

1 - I will use Multi-Objective algorithm to get functions of separation efficiency and pressure loss depending on geometric and flow parameters. I could not get efficiency directly . I use 17 injections for 17 different diameters, I need efficiency for all diameters like output parameters.

2 - Is it necessary to set a boundary layer mesh while using RSM ?

3 - Which model would be more suitable for particle drag force calculations ?

Thank you in advance