Numerical simulation on the flow structure around the injection nozzles for pneumatic dimensional control systems

A numerical simulation on the airflow exiting from a nozzle in a pneumatic dimensional control system has been conducted using computational fluid dyn amics code FLUENT (V. 4.3), which solves finite-difference equations. The i mportant changes occurring in the velocity and pressure fields in the vicin ity of the nozzle, as the air exiting from the nozzle and impinging on a fl at plate, are the prime objectives of the present studies. Simulation studi es were first focus on examining the flow characteristics of the system wit h the conventional nozzle geometry design. Some comparisons with the experi mental results previously obtained by Crnojevic et al. (Crnojevic, C., Roy, G., Bettahar, A., and Florent, P., ''The Influence or the Regulator Diamet er and Injection Nozzle Geometry on the Flow Structure in Pneumatic Dimensi onal Control Systems, " ASME J. Fluids Eng., 119, pp. 609-615) were also ma de. Further simulation studies were conducted with particular attention to a more efficient nozzle geometry. It was found that a divergent type of noz zle design could effectively eliminate the flow separation regions within t he nozzle head. By allowing the divergent angle of the nozzle head (alpha) to vary (from zero to about 25 degrees), a more extensive and sensitive mea surement range can be achieved at a given pressure regulator diameter to no zzle diameter ratio.