Since the original patented design by Tesla in 1913, while some researchers proposed modified designs to the original Tesla turbine design, some researchers showed interest on the modeling and numerical simulation studies aimed at achieving better performance of Tesla turbines. Many investigations have been carried out to determine the performance and efficiency of Tesla turbo-machinery. Most of these investigations had a certain limited application as the objective, with regard to size and speed as well as the nature of the operating fluid. However, some of the investigations have tried to establish the generalized performance of Tesla-type turbomachines. In general, it has been found that the efficiency of the rotor can be very high, at least equal to that achieved by conventional rotors. But it has proved very difficult to achieve efficient nozzles in the case of turbines, and efficient diffusers for pumps and compressors. As a result, only modest machine efficiencies have been demonstrated. Principally for these reasons the Tesla-type turbo-machinery has had little utilization. There is, however, a widespread belief that it will find applications in the future, at least in situations in which conventional turbomachinery is not adequate.