[Mohsin]

In the species model, when do we have to disable the "inlet diffusion" and "Diffusion Energy Source" from the option group box???

In the FLUENT manual, it is written that

"For the pressure-based solver in FLUENT the net transport of species at inlets consists of both convection and diffusion components. The convection component is fixed by the inlet species concentration, whereas the diffusion component depends on the gradient of the computed species concentration field (which is not known a priori). In some cases, you may wish to include only the convective transport of species through the inlets of your domain. You can do this by disabling inlet species diffusion. By default, FLUENT includes the diffusion flux of species at inlets. Generally, you would want to disable the Inlet Diffusion option if at one of the

inlets the convective flux is very small, resulting in mass loss by diffusion through that inlet"

How to determine the convective flux???