Based on the thing that you are saying it is same as the wind turbine that you want to simulate it in the water . If you mean that please note my simulation below
would it be wise on my part to ask which section of water turbine?
Say
1. Inlet section of turbine - penstock
2. Is it the scroll casing _reaction turbine
3. Guide vanes
4. Runner vanes
5. Draft tube.
I suggest in CFD , keep geometry simple and take complex physics models to simulate.
All the very best. keep trying for creating geometry with your calculations. Blade profile and rotor vane profiles can be calculated and appropriately simulated.