Editing Tesla turbine (section)

==Theory==
{{blockquote
|In the pump, the radial or static pressure, due to centrifugal force, is added to the tangential or dynamic, thus increasing the effective head and assisting in the expulsion of the fluid. In the motor, on the contrary, the first named pressure, being opposed to that of supply, reduces the effective head and the velocity of radial flow toward the center. Again, in the propelled machine a great torque is always desirable, this calling for an increased number of disks and smaller distance of separation, while in the propelling machine, for numerous economic reasons, the rotary effort should be the smallest and the speed the greatest practicable.|author=Nikola Tesla<ref name="patent-1061206"/>
}}

In standard [[Steam turbine|steam turbines]], the steam must press on the blades for the rotor to extract energy from the steam; the blades must be carefully oriented to minimize the angle of attack to the blade surface area. In other words, in the optimal regime, the orientation of the blades minimizes the angle (blade pitch) with which the steam is hitting their surface area, to create smooth steam flow and to minimize [[turbulence]]. This turbulence reduces the amount of useful energy that can be extracted from the incoming steam flow.{{Citation needed|date=July 2021}}

In the Tesla turbine, considering that there are no blades to be impacted, the mechanics of the reaction forces are different. The reaction force to the steam head pressure builds relatively quickly, in the form of a steam pressure "belt" along the periphery of the turbine. That belt is most dense, and pressurized, in the periphery as its pressure, when the rotor is not under load, will be not much less than the (incoming) steam pressure. In a normal operational mode, that peripheral pressure limits the flow of the incoming stream, and in this way, the Tesla turbine can be said to be self-governing. When the rotor is not under load, the relative speeds between the "steam compressed spirals" (SCS, the steam spirally rotating between the disks) and the disks are minimal.{{Citation needed|date=July 2021}}

When a load is applied to the Tesla turbine, the shaft slows down; that is, the speed of the discs relative to the (moving) fluid increases as the fluid, at least initially, preserves its angular momentum. For example, in a {{convert|10|cm|abbr=on}} radius, where at 9000 [[RPM]] the peripheral disk speeds are {{convert|90|m/s|abbr=on}} when there is no load on the rotor, the disks move at approximately the same speed as the fluid, but when the rotor is loaded, the relative velocity differential (between the SCS and the metal disks) increases and, at a rotor speed of {{convert|45|m/s|abbr=on}}, the rotor has a relative speed of 45 m/s to the SCS. This is a dynamic environment, and these speeds reach these values over time interval and not instantly. Here we have to note that fluids start to behave like solid bodies at high relative velocities, and in the case of the Tesla turbine, we also have to take into consideration the additional pressure. With this pressure and relative velocity toward the faces of the discs, the steam should start behaving like a solid body (SCS) dragging on the disks' surfaces. The created "friction" can only lead to the generation of additional heat directly on the disk and in SCS and will be most pronounced in the peripheral layer, where the relative velocity between the metal discs and SCS discs is the highest. This increase in the temperature, due to the friction between the SCS disks and the turbine disks, will be translated to an increase in the SCS temperature, and that will lead to SCS steam expansion and pressure increase perpendicular to the metal discs as well as radially on the axis of rotation, and so this [[Fluid dynamics|fluid-dynamic]] model appears to be positive feedback for transmitting a stronger "dragging" on the metal disks and consequently increasing the torque at the axis of rotation.{{Citation needed|date=July 2021}}