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Weird velocity results for low mach number combustion

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Old   June 8, 2018, 11:36
Default Weird velocity results for low mach number combustion
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Rafael Becker Meier
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Hello Foamers,
I am simulating a premixed flame in a narrow channel in normal conditions ( atmospheric T and p ), so the problem is the low mach number problem. I'm using reactingFoam with one step chemical kinetic for the methane with simple structured mesh. My boundary conditions are:



p: inlet - fixedValue || outlet-totalPressure
U: inlet fixedValue(1e-3 0 0) || outlet-pressureInletOutletVelocity;


I add my results,



Temper.png

Velocity.png

pressure.png

pressure_inlet.png

velocity_inlet.png


The simulation converged, but ...


The temperature behavior is normal, but for the pressure and velocity not. The problems is that I'm was expecting a less pressure and velocity variation inside the domain. I show the velocity and pressure behavior at channel's inlet. For me, there are some gradients that seems weird. I'm wondering if this is a compressible effect, because I start the combustion with a strong ignition. Therefore, I



1. This problem can be cause by mesh?


2. Are there more correct boundary conditions for this case?



3. I know that in this forum there was some discussion about reactingFoam behavior and structure for low mach number simulations, but it was not clear for me if is needed to do some adaptations to get correct results.



4. And, if this is not a stupid question regarding third question, how is done the thermodynamic decoupled in reactingFoam or, if exist a way to set the pressure to get a correct behavior for a low mach number combustion



Thanks
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low mach flow, premixed combustion, reactingfoam

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