fixedFluxPressure BC

tperet · September 13, 2016, 14:06

Hi everyone,

I want to simulate the water flow into a spray gun and I have some questions on the boundary conditions. Within the Boundaries section of the OF user guide, it is written that it is better to employ on the wall patches the fixedFluxPressure BC instead of the zeroGradient one. However, I'm wondering what are the differences between those two types of BC ? I glanced at the source file but it doesn't help at all. If someone has some piece of information about the equations or steps involved in that BC, I'm really interested.

Thank you all,

Thomas

francois · September 14, 2016, 14:42

This may help you

It's funny because today one of my students just gave me some results of buoyantBoussinesqSimpleFoam simulations to test the influence of this boundary condition.
Disturbingly, the results give significantly different trends between the two cases and I can not explain them for the moment.

Did you notice also the same sensitivity ?

tperet · September 16, 2016, 12:06

Hello,

Thank you for your answer and the link.

I haven't yet compared the impact of the BC on the results by myself. If I do it someday, I'll let you know...

However, I've read several times that people observe discrepancies or claimed that was not surprising at all...

Thomas

September 13, 2016, 14:06	fixedFluxPressure BC	#1
tperet New Member thomas peret Join Date: Jul 2016 Posts: 6 Rep Power: 9	Hi everyone, I want to simulate the water flow into a spray gun and I have some questions on the boundary conditions. Within the Boundaries section of the OF user guide, it is written that it is better to employ on the wall patches the fixedFluxPressure BC instead of the zeroGradient one. However, I'm wondering what are the differences between those two types of BC ? I glanced at the source file but it doesn't help at all. If someone has some piece of information about the equations or steps involved in that BC, I'm really interested. Thank you all, Thomas

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September 14, 2016, 14:42		#2
francois Senior Member Francois Beaubert Join Date: Mar 2009 Location: Lille, France Posts: 147 Rep Power: 17	This may help you It's funny because today one of my students just gave me some results of buoyantBoussinesqSimpleFoam simulations to test the influence of this boundary condition. Disturbingly, the results give significantly different trends between the two cases and I can not explain them for the moment. Did you notice also the same sensitivity ?

September 16, 2016, 12:06		#3
tperet New Member thomas peret Join Date: Jul 2016 Posts: 6 Rep Power: 9	Hello, Thank you for your answer and the link. I haven't yet compared the impact of the BC on the results by myself. If I do it someday, I'll let you know... However, I've read several times that people observe discrepancies or claimed that was not surprising at all... Thomas