Dear All,
We are using Autodesk cfd to calculate the air flow in a single sided naturally ventilated room, where air flow depends only on buoyancy due to temperature difference between inside and outside.
in the first case -as in attached pictures- the flow seems reasonable: hot air rises up, while cold air flows near to floor.
in the second case we tried to add a scalar representing Co2, the results shown in second picture can never be true, cold air rises up !!
I have been stuck in this for 2 months now (Hence: the air material in both cases is variable so that buoyancy takes place)
The flow network model can be solved with comparatively less computational cost; however, all the airflows between nodes should be modeled as one‐dimensional. The airflows and their transports in a room are not one‐dimensional but three‐dimensional. CFD is a convenient tool for analyzing such three‐dimensional flows and transports. The equations are non‐linear, and their solutions are usually obtained numerically. The CFD analysis requires considerable computation resources and computational time.
CO2 is heavier than air. So perhaps it's the CO2 concentration that drives the flow. Maybe you can check the mass density of your gas in the simulation domain to check this.
The flow network model can be solved with comparatively less computational cost; however, all the airflows between nodes should be modeled as one‐dimensional. The airflows and their transports in a room are not one‐dimensional but three‐dimensional. CFD is a convenient tool for analyzing such three‐dimensional flows and transports. The equations are non‐linear, and their solutions are usually obtained numerically. The CFD analysis requires considerable computation resources and computational time.
I think you need to check boundary conditions of your model again. There must be issue with properties you're currently incorporating i.e. mass, density.
Moreover try it in ANSYS too, hope it helps
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