On the influence of internal flow structure on performance of plain-orifice atomizers

A series of parametric simulations was conducted to investigate the unstead y internal flow behavior in plain orifice, or "pressure" atomizers. The uns teady behavior is attributed to instabilities in the vena contracta and the presence of cavitation in this region. Even though the present calculation s are laminar, they exhibit turbulent-like characteristics due to this inst ability. Orifice mass flow is shown to be periodic in most instances with f luctuations occurring at frequencies consistent with the orifice transit ti me. Cavitation is shown to enhance fluctuations, in some cases quite dramat ically. Results are presented for a range of flow conditions and orifice ge ometries.