Noise and Flow Characteristics of Coaxial Jets

Abstract

The noise from cold subsonic coaxial jets issuing from concentric nozzles with external mixing has been examined and an attempt made to relate the results to the flow patterns of the jets. As the velocity of the annular jet was increased in relation to a given central jet velocity, an initial attenuation of the jet noise was observed. On further increasing the annular jet velocity until the velocities of the two streams were nearly equal, the noise was in excess of that of the central jet alone. An attempt has been made to predict the curve relating the attenuation attained to the coaxial jet velocity. In comparing the attenuation produced by a coaxial jet combination with that of a single jet, it could be argued that the total thrust in each case should be the same and experimental results are presented on this basis. Results are also available for a nozzle configuration in which the jets are mixed internally in a tube before discharge, and the paper is completed with the results obtained from an annular nozzle acting alone.

Comparison of measured and predicted flight effects on high-bypass coaxial jet exhaust noise

“…The NASA interim method, based on exte lion of the earlier F studies of Olsen and Friedman and Williams, et al 5 has been shown to agree reasonably well with full-J scale static and flight data 6 for low to moderately-high bypass ratio coaxial jets.…”

Dynamics of Jets Issuing from Trailing-Edge Modified Nozzles

“…An analytical two-dimensional model on turbulent coaxial jets was proposed by Morton [46], while another model was proposed for a coaxial burning jet by Beer et al [7]. The importance of the velocityratio between the two coaxial jet streams with respect to noise attenuation was first demonstrated by Williams et al [102] and their study was soon followed by those of Champagne and Wygnaski [14], Kwan and Ko [29][30][31] and Ko and Au [28], just to name a few. On the other hand, influences due to other flow parameters of interest, such as the initial turbulent intensity and the wall thickness, were investigated by Matsumoto et al [40].…”

Thermal Diffusion Phenomena in Free Jets from Concentric Annulus

“…There are numerous studies on the coaxial jets discharging into the still air and their unique phenomenon. The works on the vertical structures of the coaxial jets were reported by many researchers (Chigier, 1964;66 S. TORII Williams, 1969;Champange, 1971;Ko, 1985;Rehab, 1997). Kiwata et al (1997) indicated the existence of a recirculating region along the axis of the coaxial jets.…”