Hi Soude,
CFD isn't really a simple straight forward "someone gives you an algorithm, you repeat it, and it works" type of problem. It takes some knowledge in fluid dynamics to understand what is going on in the background (and to enable you to differentiates a bullshit solution that converged, from one that actually makes sense), and it takes some understanding of the actual methods that run in the background of your CFD solver to know how to adjust it's parameters (mesh type, size, and methods being some but not all of them, as simulation settings influence the solution in a very meaningful way).
I would recommend starting with these tutorials by Cornell university which I found very helpful when I was a student (pay particular attention to the wind turbine one). These are by no means a guarantee of success, but they should help you keep your calculation error at no worse than 40%. If you want better than that, there is a lot of learning involved...