Reason for Swril and Backflow in Fan Simulation

Gkchpa · July 2, 2020, 17:04

Hi everyone,
I am trying to Simulate fan in an enclosure of length 500 mm front & behind the fan.

incompressible Unsteady simulations

boundary conditions: Pressure Inlet and Pressure outlet - 0 gauge pressure (default)

Cell zone conditions: Rotating fluid domain with 3000 Rpm

as the Continuity is diverging I reduced relaxation factor momentum to 0.4 and KE to 0.4

run simulation for 150 iterations

So in the pathlines of flow, I can see the swirl and backflow. as I am new to fan Simulation I have no idea whether they are common in the simulation. If they arent how to solve them in the simulation

Thanks in advance

CFDfan · July 4, 2020, 11:38

try with extended 2x, 3x, 4x computational domain

aero_head · November 14, 2020, 17:28

Backflow is occurring because your domain is not long enough. Try modifying that parameter.

SaschaGH · November 17, 2020, 07:40

Hi,

swirl and backflow are common behind the fan.
Indeed extending your outlet section will help to avoid problems related to backflow, as you are providing more computational domain for the flow to settle, but you can also switch from "Outlet" to "Opening" definition, which will allow backflow.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Convergence and backflow problem in cavitation simulation	burakaltintas	CONVERGE	2	August 9, 2016 07:42
Constant Power Fan Model using General Momentum Source	Dano62	CFX	0	April 14, 2016 13:09
Backflow at outlet in a Eulerian gas-solid simulation	audrey	CFX	10	October 25, 2012 06:15
Backflow in eulerian multiphase simulation	xeusater	FLUENT	0	June 26, 2009 07:50
backflow in a jet simulation	Hao	CFX	0	October 3, 2008 02:23

July 4, 2020, 11:38		#2
CFDfan Senior Member Join Date: Jun 2011 Posts: 195 Rep Power: 14	try with extended 2x, 3x, 4x computational domain

November 14, 2020, 17:28		#3
aero_head Senior Member Kira Join Date: Nov 2020 Location: Canada Posts: 435 Rep Power: 8	Backflow is occurring because your domain is not long enough. Try modifying that parameter.

November 17, 2020, 07:40		#4
SaschaGH New Member Sascha Join Date: May 2012 Location: Germany Posts: 14 Rep Power: 13	Hi, swirl and backflow are common behind the fan. Indeed extending your outlet section will help to avoid problems related to backflow, as you are providing more computational domain for the flow to settle, but you can also switch from "Outlet" to "Opening" definition, which will allow backflow.