porous media

jdbustosv · May 14, 2024, 16:16

Good day. I'm having a problem that I didn't use to have. When configuring a volume as a porous medium, I use the term linear and quadratic to simulate the resistance to flow. This causes a pressure drop and should cause a deceleration of the fluid as it passes through the pore volume.

It turns out that the simulation is giving me the opposite: the fluid is accelerating as it passes the porous medium. The pressure drops as expected. But the velocity of the fluid is increasing. I tried changing the streamwise direction vector to (-1) but nothing works. The fluid does not slow down. I appreciate any help.

Opaque · May 14, 2024, 17:37

Quote:

Originally Posted by jdbustosv

Good day. I'm having a problem that I didn't use to have. When configuring a volume as a porous medium, I use the term linear and quadratic to simulate the resistance to flow. This causes a pressure drop and should cause a deceleration of the fluid as it passes through the pore volume.

It turns out that the simulation is giving me the opposite: the fluid is accelerating as it passes the porous medium. The pressure drops as expected. But the velocity of the fluid is increasing. I tried changing the streamwise direction vector to (-1) but nothing works. The fluid does not slow down. I appreciate any help.

Which velocity are you comparing? Superficial velocity, or local velocity.

If you have an open medium, say fluid domain, and it enters a porous media and you use local/true velocity formulation the velocity will INCREASE regardless of the pressure drop.

True/Local Velocity = Superficial Velocity / Volume Porosity

jdbustosv · May 14, 2024, 18:22

Thanks for your answer. Using any formulation (true or superficial) in the porous medium setup, I get the same response. It accelerates.

evcelica · May 15, 2024, 12:06

Why would it decelerate? That should not ever happen depending on geometry.
Even Superficial velocity would remain constant in a continuum of incompressible flow.
Are you using a compressible fluid? If so, pressure drop causes reduced density and therefore acceleration of the fluid.
If this isn't it, then we need more info regarding your geometry and setup:
Are you using a general loss subdomain in your fluid domain, or a Separate Porous Domain? If the latter what are you using for Volume Porosity, superficial/true velocity specification, and values.

May 14, 2024, 16:16	porous media	#1
jdbustosv New Member Daniel Join Date: Oct 2023 Posts: 4 Rep Power: 2	Good day. I'm having a problem that I didn't use to have. When configuring a volume as a porous medium, I use the term linear and quadratic to simulate the resistance to flow. This causes a pressure drop and should cause a deceleration of the fluid as it passes through the pore volume. It turns out that the simulation is giving me the opposite: the fluid is accelerating as it passes the porous medium. The pressure drops as expected. But the velocity of the fluid is increasing. I tried changing the streamwise direction vector to (-1) but nothing works. The fluid does not slow down. I appreciate any help.

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May 14, 2024, 18:22		#3
jdbustosv New Member Daniel Join Date: Oct 2023 Posts: 4 Rep Power: 2	Thanks for your answer. Using any formulation (true or superficial) in the porous medium setup, I get the same response. It accelerates.

May 15, 2024, 12:06		#4
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,171 Rep Power: 23	Why would it decelerate? That should not ever happen depending on geometry. Even Superficial velocity would remain constant in a continuum of incompressible flow. Are you using a compressible fluid? If so, pressure drop causes reduced density and therefore acceleration of the fluid. If this isn't it, then we need more info regarding your geometry and setup: Are you using a general loss subdomain in your fluid domain, or a Separate Porous Domain? If the latter what are you using for Volume Porosity, superficial/true velocity specification, and values.