Flow structure in critical flow Venturi nozzle and its effect on the flow rate

The flow fields in toroidal Venturi-nozzles, shaped according to the ISO-9300 Standard, have been investigated using numerical flow simulation. The present study was aimed at clarifying some of the phenomena associated with unchoking the flow in the throat. To this end, the shock structure has been studied for different Reynolds numbers and exit pressure ratios. The flow simulations were carried out in two and three dimensions. The flow fields were always unsteady, displaying a complex shock-boundary layer interaction.