While designing a turbine, the blade twist is apparent from the velocity triangles, and this analysis only depends on the velocity.

However, would there be any difference for different media? When all conditions stay the same but the density of the fluid changes, would the twist stay the same?

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    $\begingroup$ What media/fluid are you expecting the turbine to run in? $\endgroup$ – CrossRoads Apr 29 '19 at 12:50
  • $\begingroup$ The design is for water, but I am interested in how the design procedure (just the part for the blade twist calculations) could be tweaked for compressible flows like air or carbon dioxide, say. $\endgroup$ – user2505282 Apr 30 '19 at 0:41
  • $\begingroup$ Can you provide more details about which conditions remain the same? RPM, volumetric flow rate, mass flow rate, inlet pressure, outlet pressure, kinematic viscosity, dynamic viscosity, ...? Otherwise, the answer simply is: "yes the twist would change". $\endgroup$ – hrobeers May 23 '19 at 11:23

A classic comparison would be boat props vs aircraft at various RPM. A higher density (viscosity) fluid would put more stress on the blade tips, hence shorter and more robustly built blades. The amount of twist would depend on loading of props and would include chord length. A tapered prop may have a different twist from an untapered or reverse tapered. Diameter and RPM are also factors in loading. And, as in aircraft, twist would also play a role in cruise efficiency or acceleration from standing still.

So there is no one rule about this going from one fluid to another (rare application). Variations of design and performance in one fluid are much more common.


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