basizeland wrote:is this what you meant by using naca airfoils for the co2 chamber
Would have to see a top view. Airfoil shapes have significantly lower drag coefficients than spheres/cylinders; nearly an order of magnitude less. (As a side note: look at the shape of most slender fish, such as trout or salmon. The shape of their body, looking from the top, generally has the shape of a typical NACA airfoil. This is an adaptation that increases the efficiency of their energy usage as they swim through the water.) The reason an airfoil has such a significantly lower drag is due to flow separation at the back end. If the flow can be reintroduced to the free stream smoothly, the low pressure wake that is left can be minimized, thus reducing the drag.
One complication that you would have to consider is the fact that the CO2 cartridge is also contributing to the flow. If the wake left by the body is the same size or slightly smaller than the plume from the cartridge then that should be sufficient. This is why Jersey Tom recommended including it in your CFD, if possible. I'm not specifically an expert in CFD, as I work in FEA and Hydrocodes, but if you post any information on boundary conditions and mesh sizes, some of the guys here might be able to give you some insight as to how valid your results are or how you could improve them.