Learning Forum

[SatishYadavBusa]

Hello,

 

I want to simulate Non Boussinesq Fountain at Low Reynolds it is basically mixing of gas helium at inlet with ambient air inside the domain I have been using Energy equation and Species Transport for the simulation but unable to get the same density/mass fraction field as of the experiment. I attach the image of the mesh here I would like to know where I am doing mistake for not getting the simulation right. I am using Pressure based solver with transient,2d Planar with gravitational acceleration switched on -9.81 in Y direction.Species transport selected with Diffusion energy source switched on.I particularly have the doubt in Cell Zone Operating Conditions if I switch on gravity why is the Boussinesq Temperature getting switched on automatically,what is the operating density here what is the meaning of it how it affects the solution? At the pressure outlet it would be asking for back flow species why do we need to specify them in my case I don't know how much mass fraction of gases will be near the outlet? Also what is the boussinesq in the material density available?

Hereby I attach all the photos of my simulation any one please help me out I have been trying this since 2 months.Basically I have to get the flapping motion of helium air mixture then it should go up and get outside from the pressure outlet.Gases are at same pressure and temperature while mixing.Thermal everywhere 300 k Temperature,initializing with respect to inlet as 0 mass fraction then patching the fluid surface body as 1 mass fraction.I 

 

I have uploaded all the photos of the necessary things any one can help please I would be so grateful to them.

 

 

[Rob]

Staff are not allowed to open attachments or download files: please repost some of the images into the thread. 

Note, 2d planar assumes a 1m thick domain: you're modelling a slot.  2d axi-symmetric make more sense if it's a round jet? 

[SatishYadavBusa]

Respected Sir,

 

I have attached the image of the mesh may I know why aren't I able to do the simulation or is Ansys Fluent does not have the solver which I am doing for the domain. I am using Nozzle with rectangular shape with dimension as specified by the paper.

[Rob]

Fluent will model species & buoyant movement. Have you switched on gravity, defined species etc? 

[SatishYadavBusa]

Sir,

Which fluent model is best for Isothermal Miscible gases Mixing Multiphase-Mixture or Multiphase Eulerian or Species Transport and answer to your question Yes I have switched on Gravity defined species etc as per requirement but I do not get flow field as required by experiment. Please explain this in Detail is Non Boussinesq Approximation of Gases mixing at Low Reynolds Number is it possible to do in fluent at Same Temperatures?

[Rob]

If you expect the gases to fully mix then use species. If you expect the layer of the heavier gas to form (eg propane released into still air) then Eulerian multiphase will give a better result.  The models are explained in the documentation, so please read that: we can't go into too much engineering detail here as it's a public forum (and the US export laws apply to all ANSYS staff).