Floating Particles in DPM or MPM?

denbjornen · July 23, 2017, 16:29

Hello,

I'm having a really hard time trying to do macroscopic particle tracking in open channel flow. At first I was using the VOF model with a free surface pressure outlet for air, until I realized that I wasn't at all concerned with the interaction between the two phases. I switched my free surface to a zero shear wall and was able to get convergence rather quickly. First I solved the steady laminar problem, which I used as the initialization for the viscous turbulent model. Finally, I switched over to transient simulation to do particle tracking.

My problem is this: I want to simulate the motion of "trash" in the flow. It should be captured in a collection filter in the side of the channel. I'd like to see if the design of the walls will successfully divert the particle stream into the collection filter. Right now I've simulated unsteady DPM and MPM to no avail. I'm able to get particle tracks, but all of the particles sink as soon as they are injectd into the flow. I thought this was simply due to density, but I just ran a simulation with particle density at 50 kg/m3 and the particles are still unable to float. I'm injecting 1 particle every second with initial velocity equal to the area weighted average velocity of the flow at the inlet, each particle has a diameter of 0.07 m. Does anybody know why they are sinking?

myaghoobi2 · November 13, 2017, 07:50

Hi
MPM model does consider the buoyancy and also gravity forces but there is not any possibility to get the value of those forces that is so important especially when you want to apply VOF model and have multiphases with different densities. But I can assure you that upon my recent simulations, the value of buoyancy and gravity are calculated correctly.

July 23, 2017, 16:29	Floating Particles in DPM or MPM?	#1
denbjornen New Member Brandon Johnson Join Date: Jul 2017 Posts: 6 Rep Power: 8	Hello, I'm having a really hard time trying to do macroscopic particle tracking in open channel flow. At first I was using the VOF model with a free surface pressure outlet for air, until I realized that I wasn't at all concerned with the interaction between the two phases. I switched my free surface to a zero shear wall and was able to get convergence rather quickly. First I solved the steady laminar problem, which I used as the initialization for the viscous turbulent model. Finally, I switched over to transient simulation to do particle tracking. My problem is this: I want to simulate the motion of "trash" in the flow. It should be captured in a collection filter in the side of the channel. I'd like to see if the design of the walls will successfully divert the particle stream into the collection filter. Right now I've simulated unsteady DPM and MPM to no avail. I'm able to get particle tracks, but all of the particles sink as soon as they are injectd into the flow. I thought this was simply due to density, but I just ran a simulation with particle density at 50 kg/m3 and the particles are still unable to float. I'm injecting 1 particle every second with initial velocity equal to the area weighted average velocity of the flow at the inlet, each particle has a diameter of 0.07 m. Does anybody know why they are sinking?

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November 13, 2017, 07:50		#2
myaghoobi2 New Member mohammad Join Date: May 2016 Location: Tehran Posts: 17 Rep Power: 9	Hi MPM model does consider the buoyancy and also gravity forces but there is not any possibility to get the value of those forces that is so important especially when you want to apply VOF model and have multiphases with different densities. But I can assure you that upon my recent simulations, the value of buoyancy and gravity are calculated correctly.