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 June 13, 2003, 08:32 steady/unsteady combustion??? #1 john Guest   Posts: n/a Hi all, Could someone explain to me what steady and unsteady combustion is? I mean when should the simulation be solved for steay state conditions and when should it be solved for unsteady conditions???? Cheers John

 June 13, 2003, 09:04 Re: steady/unsteady combustion??? #2 prasat Guest   Posts: n/a I will be happy to help you out. As in a laminar flow the fluid motion reaches a steady state.Therofre it is enough to simulation the Navier stokes equation steady term(without the unsteady or transient term). But in case of turbulence we nedd to solve the transient term also. You can apply the similar arguments in case of combustion. prasat

 June 13, 2003, 09:55 Re: steady/unsteady combustion??? #3 john Guest   Posts: n/a Hi prasat, Thank you for your reply. Does that mean, that if I want to simulate a furnace i have to do an unsteady simulation which causes large computation time, or is there an assumption I can use to simulate the furnace combustion with steady state formulation. cheers, John.

 June 13, 2003, 10:40 Re: steady/unsteady combustion??? #4 prasat Guest   Posts: n/a What type flow is it turbulent or laminar one. I guess that it will be turbulent only. so that means for simulation you have to take the unsteady term also. prasat

 June 13, 2003, 11:32 Re: steady/unsteady combustion??? #5 john Guest   Posts: n/a I don't know if you use fluent but in their turbulent combustion tutorial the solver is steady state. If the flow is turbulent shouldn't the solver be unsteady? This is the information I really want because if i know why they were able to solve in steady state maybe I too can, saving me a lot of time.

 June 13, 2003, 12:18 Re: steady/unsteady combustion??? #6 gorka Guest   Posts: n/a Hi, If you use RANS (Reynolds Averaged Navier Stokes) approach for modelling turbulence it's not true that you must perform unsteady simulation. In fact, you should solve the unsteady problem only when the unsteadiness is caused by flow features (vortex sheding, time varying BC etc.) Gorka

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