Theoretical discharge coefficient of a critical circular-arc nozzle with laminar boundary layer and its verification by measurements using super-accurate nozzles

The discharge coefficient of a circular-are critical Venturi nozzle is deri ved theoretically by combining theories to calculate mass flow defects caus ed by the core flow distribution and the laminar boundary layer. The equati on obtained is verified by measurements using a constant volume tank system and nozzles of similar shape machined by super accurate lathes, which achi eved mirror finish without polishing thus resulting in a machining error of less than 1 mu m. The agreement of the theoretical and measured discharge coefficients is better than 0.04% at Reynolds numbers larger than 8x10(4), the minimum used. The equation derived is in an analytical form, which enab les an estimation of the effects of specific heat ratio as well as nozzle s hape. (C) 2000 Elsevier Science Ltd. All rights reserved.