Learning Forum

[Sayantan Biswas]

Hello Everyone,

I'm currently working on passive tracer mixing simulation in air-water system using transient Euler-Euler method. Consider a vessel (an image is attached), water is patched up to a certain height (water domain) and above that air is present (air domain), multiple nozzles are arranged at the bottom of vessel through which air is coming and enhancing the mixing. The flow field (suitable drag model, lift force & turbulent dispersion force) are in reasonably good agreement with experiment (time averaged distribution as well as flow dynamics/ local fluctuation).

Once the flow is established, I'm enabling species transport model for passive mixing simulation i.e. no chemical reaction is involved. The tracer material property is exactly same as water (density, viscosity), constant mass diffusion co-efficient is considered as 9.1e-9 m2/s. A small cylindrical region in the water domain at the central zone (few mm below the air-water interface) is patched with tracer mass fraction 1 at time t=0 sec.

The tracer is defined in water phase. Mixture-Template, mixture density: volume weighted mixing law, mixture viscosity is constant as water, mass diffusivity: Multi-component.

mix_snap.jpg

[Rob]

Check the water volume fraction in the air space, you may have a tiny amount of liquid which is throwing the post processing. Re the mass of tracer, how well is the system converging?n