The paper describes primary calibration of high-precision nozzles (HPNs), which have ideal geometries, at critical condition, theoretical calculation of the discharge coefficient to be verified by the primary calibration, concept of fluid dynamical standard using HPN, precise measurement of boundary layer transition in HPNs in terms of flowrate, superfine structure in the critical flowrate, discrepancy which can occur between primary calibrations and field applications of critical nozzles, and 3D flow velocity field measurements based on recovery temperature, which visualizes many interesting phenomena in axi-symmetric transonic flow as shock interactions, acceleration by edge, reflection of shocks, Fano flow and so on.
The Discharge Coefficients of Critical Nozzles Made by Using Super-accurate Lathes