CFD Online Discussion Forums - 3D geometry run as 2D symmetry section?

Hi all,

I was curious about how much I can push the simplification in CFD modelling.
Please have a look at following image:

https://imagizer.imageshack.us/v2/53...537/i0eE8F.jpg

My goal is to find the optimum angle $\theta$ for a casting, which obviously is 3D, so that I have least pressure drop. So I may need to create a series of 3D models with different $\theta$ to get a trend and then when I know the minima of a curve of pressure drop versus $\theta$ , I have found my optimum value.

Now, I was thinking, if i only create a 2D sketch of this model with different $\theta$ and obtain the optimum value, I can have some guidance about optimum angle for 3D. Agreed, the actual casting is cylingrical and I am representing it as 2D, and the physics is entirely different. But what I want only, is to get closer to optimum value through the series of 2D simulations. Suppose if I find that the optimum angle for 2D section is say 50 deg, I can then take series of angles close to 50 and run 3D simulations.

It is not about exact result of 2D, but about zeroing in on the range of of angles I need to select for 3D simulations that I can focus on. It is far better to run with range of angles at 45, 47, 50, 53 and 55 deg instead of running with range of 30, 40, 50, 60, 70 deg, to get the accurate inflection point of the curve, to find optimum angle.

Does this approach sound reasonable? Or am I missing something?

Thanks!