I want to obtain information about a 3D flow on its plane of reflective symmetry, would modelling it as a 2D flow on this symmetry plane give me the same results? Thanks alot, Kieran

If the problem has a spherical symmetry like a bubble pulsation, you will get a desirable solution. But the problem need to contain a result in the third direction, you should model the problem in the 3d.

Thanks for the reply, there are no velocities in the third dimension but im not entirely sure about other variables as i've only just started CFD-ing. Would modelling a rectangular duct as a 2D model down the centre line work?

I am far from an expert but I guess it would work for a simple rectangular duct. I would imagine the only problem you may have is how narrow it is compared to the length, i.e. the 'developedness' of the flow perpendicular to the symmetry plane.

I would be interested to know more about the answer to this.

If it is a simple rectanglar duct then it would not take too much effort to model in 2D and 3D and compare results.

You can use this method to model the flow over an aerofoil in 2D, as long as the aspect ratio is sufficient so that edge effects are not affecting the flow at the symmetry plane. The results for lift and drag coefficients would be incorrect however as edge effects are ignored.