Numerical and experimental investigation of unsteady effects in critical Venturi nozzles

Numerical Investigation of Transonic Resonance with a Convergent-Divergent Nozzle

“…Another numerical work [15] brought to the authors' attention also merit a discussion. This work concerned flow metering using Venturi nozzles.…”

“…For certain conditions, a quasi-periodic fluctuation was observed in the computed flow field. From the data provided in [15] it was not possible to determine if the frequencies followed the correlation equations of [1]. However, the symptoms appeared similar and the unsteadiness seemed likely to be of the same origin as the transonic resonance.…”

“…17). Except for the similarity that all three simulations (present, [13] and [15]) involved axisymmetric or twodimensional codes, different algorithms and procedures were followed. The upstream boundary layer in the present simulation was 'laminar', that in [13] was apparently turbulent.…”

Optical Measurements of Shock Waves in Critical Nozzles at Low Reynolds Numbers

“…Also, they demonstrated that the critical back pressure ratio is a function of the theoretical Reynolds number only, not dependent on the throat diameter. Furthermore, the change of the discharge coefficients occurs abruptly when the back pressure ratio approaches the critical value, and the distribution of the discharge coefficient against the back pressure ratio has at least one local maximum and one local minimum when the back pressure ratio is above the critical value and they explained the phenomena in terms of the interaction between the shock wave and the boundary layer in the diffuser, as Von Lavante et al [1] [2] showed in their numerical simulation.…”

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

“…Theoretical flow rate through CFVN assuming onedimensional isentropic flow of perfect gas (kg s À 1 ) the transition regime is very difficult, but it will be achieved by CFD [23,31] in the near future. These data confirm the pioneers' experiences and predictions [3][4][5]9] such as that the transition takes place at Reynolds numbers between 1 Â 10 6 and 2 Â 10 6 and also that the magnitude of the jump of the discharge coefficient by the transition is about 0.2%.…”