CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Questions about buoyancy driven flow

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   April 9, 2015, 18:59
Question Questions about buoyancy driven flow
New Member
Join Date: Dec 2014
Posts: 7
Rep Power: 2
mep14xw is on a distinguished road
I'm doing a flow diagnostic for a combustion lab. A ventilating hood is suspended above the burner and the hood is connected to a pipe systems where there is a fan at the alternative end.
The hood is like a rectangular nozzle that its smaller cross section is connected to the pipe line as mentioned before. The measured velocity at this cross section is at an average of 5.45m/s.
If the burned gases can successfully reach to the top of the hood(the smaller cross section), they will be ventilated.
It seems that at working condition, the burned gas may escape to the surroundings rather than go up to the top of the hood and then be sucked off.
I'm performing a 2-D axisymmetric simulation now, but doubts arose frequently.
Provided by inlet velocity 10m/s at 800K
The simulation is carried out with B.Cs as following:
velocity inlet: 10m/s, turbulence parameter: intensity 5%, length scale 0.07*D=0.0007m, thermal:800K
Wall-hood: no slip
Wall-free: no shear, slip wall
pressure outlet: gauge pressure 0
Backflow direction: normal to the boundary
average pressure specification: ticked
Target mass flow rate: 0.054398 (0.1m diameter with the measure velocity(5.45m/s)
Turbulence: backflow turbulence intensity: 5% and backflow hydraulic diameter: 0.1m
thermal: backflow total temperature: 500k

Are there some mistakes in the boundary conditions?
Because there were terrible reversed flow at the pressure-outlet and I tried to extend the exit but to no avail.
Could you pls give me some suggestions on this?
And I intended to use Boussinesq Model to account for buoyancy effect; however, in the user's guide, it states that the limitation of this model is large temperature difference. In my case, is it with a large temperature difference?
If this model can be used, how can I determined those inputs for Boussinesq parameters, namely the operating temperature, operating density, thermal expansion coefficient. Moreover, is this operating density the same as that in Material section where the thermal expansion coefficient can be inputted.

I will be so grateful if you could help me on this!!!!!!
And if anything I did not specify or not clearly stated, pls let me know.
Here are the schematic drawings; hope they could make the scenario more clear
fbid=701577913285491&set=pcb.701577973285485&type= 1&theater
mep14xw is offline   Reply With Quote


buoyancy driven flow

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Compressible Pressure Driven Flow mateiu2003k OpenFOAM Running, Solving & CFD 0 August 18, 2014 15:23
Review: Reversed flow CRT FLUENT 0 July 20, 2012 13:03
buoyancy flow and mass transport rembe Main CFD Forum 0 October 14, 2009 06:01
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
Free Surface Gravity Driven Flow Rupp Carriveau FLUENT 4 June 14, 2001 16:54

All times are GMT -4. The time now is 13:02.