A Comparison of Three Critical Flow Venturi Designs

Abstract

Three critical flow venturi designs have been examined from the standpoint of their sensitivity to initial boundary-layer thickness, inlet flow nonuniformity, separation, and transition point location. These sensitivity studies were carried out with a finite-difference computer code which represents a coupled solution of the inviscid potential core and the viscous boundary layer. Since it makes good sense to select a design that is least sensitive to these effects, it is expected that this information will be of interest to potential users of these devices. Differences between the sensitivities of the various designs were found to be small; however, a slight advantage is seen in designs which employ a circular arc entrance section and a circular arc throat.

Discharge coefficient equation for critical-flow toroidal-throat venturi nozzles covering the boundary-layer transition regime

“…Recent measurements [25][26][27][28][29][30] revealed stable boundary-layer transition in well-made CFVNs that yielded systematic variation of the discharge coefficient along the Reynolds number during the transition. Theoretical investigation of the experimental data in …”

“…As the use of CFVNs spread, measurement data in the low Reynolds number regime were also accumulated [9][10][11][12][13][14]. In the 1990s, high-precision nozzles (HPN) were machined by superaccurate lathes to produce a mirror finish with average surface roughness of 0.04 μm without being polished, thus almost eliminating the effect of geometry errors on the discharge coefficient in a certain flow rate range, and so their calibration data showed negligible scattering in the measured discharge coefficients [15][16][17][18].…”