Piston cylinder with fluid on both sides

rmawsu · October 11, 2017, 21:34

Hi,

I am going to model a hydraulic piston-cylinder while there are fluids on both sides of the piston (preferably two different fluids). The piston should move based on the pressure difference of the fluids on both sides. I have already tried using rigid body solution and immersed solid in CFX, but the fluid moves through the piston even with high momentum scaling factor and considering smooth inside ims= t expert parameter.
The other problem is that I am not able to set two different fluid zones on sides of the piston.

I think this modeling should be similar to what happens in free piston engines but I haven't found any work on those engines using Fluent or CFX.

Does anyone have any idea how I solve these issues?

Any help would be greatly appreciated.

Christophe · October 12, 2017, 00:45

There are two approaches to this. One is create a 3-d solid which overlaps the fluid domain and then simply acts as a source term to restrict the motion of the fluid based on the momentum scaling factor and the velocity differences, which you've tried. The other is to model the piston as a void in the fluid domain and assign those surfaces as rigid body. There's a CFX tutorial to try. Chapter 22 I believe which is a spring loaded pressure relief valve, to introduce the concept.

October 11, 2017, 21:34	Piston cylinder with fluid on both sides	#1
rmawsu New Member Aida Join Date: Sep 2017 Posts: 1 Rep Power: 0	Hi, I am going to model a hydraulic piston-cylinder while there are fluids on both sides of the piston (preferably two different fluids). The piston should move based on the pressure difference of the fluids on both sides. I have already tried using rigid body solution and immersed solid in CFX, but the fluid moves through the piston even with high momentum scaling factor and considering smooth inside ims= t expert parameter. The other problem is that I am not able to set two different fluid zones on sides of the piston. I think this modeling should be similar to what happens in free piston engines but I haven't found any work on those engines using Fluent or CFX. Does anyone have any idea how I solve these issues? Any help would be greatly appreciated.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
flow over a cylinder urgent!	kevin	FLUENT	8	August 11, 2015 14:00
Moving Piston And cylinder	saeidhomayounslm	FLUENT	0	July 21, 2014 04:11
how to simulate a VIV of the cylinder in a fluid domian use rigid body solution?	Mal	CFX	13	April 14, 2014 14:44
simple 2d open ended cylinder with moving piston: dynamic meshing query	lmarf88	ANSYS	0	January 6, 2014 10:55
Fluid in a rotating cylinder	Fluid Novice	Main CFD Forum	1	December 17, 1998 18:25

October 12, 2017, 00:45		#2
Christophe Member Join Date: Jan 2015 Posts: 62 Rep Power: 11	There are two approaches to this. One is create a 3-d solid which overlaps the fluid domain and then simply acts as a source term to restrict the motion of the fluid based on the momentum scaling factor and the velocity differences, which you've tried. The other is to model the piston as a void in the fluid domain and assign those surfaces as rigid body. There's a CFX tutorial to try. Chapter 22 I believe which is a spring loaded pressure relief valve, to introduce the concept.