Maximum efficiency comes in this system when the inter-disk spacing approximates the thickness of the boundary layer, and since boundary layer thickness is dependent on viscosity and pressure, the claim that a single design can be used efficiently for a variety of fuels and fluids is incorrect.
12.
The turbulent boundary layer thickness formula assumes 1 ) the flow is turbulent right from the start of the boundary layer and 2 ) the turbulent boundary layer behaves in a geometrically similar manner ( i . e . the velocity profiles are geometrically similar along the flow in the x-direction, differing only by stretching factors in y and u ( y ) ).
