How should holes in a Tesla turbine look like? I think of building a Tesla turbine out of old hard drives.
Now I wonder how to cut ventilation holes in the platters.
On the internet there are a lot of different attempts on that matter. A lot of people cut 3 arcs of 60° somewhere near the center of the platters, others cut round holes of different sizes inside the platters. But to me it seems like the decission on how to cut the holes, for a lot of people is very much a matter of personal flavour.
I didn't find any information yet on


*

*What's the best shape for the holes

*What's the best distance from the center

*What's the best diameter for the holes


(if that matters, my hard drive platters have a diameter of 9.5cm, but maybe in the end I will use different ones)
If round holes are not the best solution, I would also be interested on how "bad" it is to make round holes, as I don't have easy access to a rotary table.
 A: Here are my two cents:   After observing the Tesla turbine I noticed that the force of the air or water input comes from the outer edge of the blades,  which lets me to believe that if you place ventilating holes anywhere of the turbines wheels you are dealing with the preasure that accumulates inside the holes regardless the size they have, That is preasure against preasure.  I really think that if one placed the input of air or water somewhere in the midle of the turbine intead of the edge one will be able to place the vent holes in the inner half of the turbine. However one will have to attach to the shaft a steel flywheel with three steel weight on the tips of the wheels support to make up for loss of power due to the replacement of input nozzle to the center.
A: *

*The holes be should round because that shape causes least disturbance in the movement of fluid. Everywhere you look, fluids always move in circular vessels.

*Holes should be as close to the center as possible. You want to maximize the traveling path of propelling fluid by placing holes near the center. In this way your turbine will use all possible energy of fluid.

*The holes diameter shouldn't exceed the diameter of input pipe. On the picture below you can see how the diameter gradually shrinks as it get's closer to turbine blades. Maybe you should also make holes smaller compared to input pipe and make tests.



