Dynamics and Response to Control of Single and Dual Supersonic Impinging Jets

Abstract

An impinging jet produces a highly unsteady flowfield which results in very high noise levels, harmful structural vibrations, and significant loss of lift and stability in applications such as the short takeoff and vertical landing aircraft. An understanding of the flowfield and implementation of an effective flow control technique are necessary to reduce these adverse effects. The presence of multiple impinging jets leads to the generation of a fountain flow, which further adds to the complexity of the flowfield dynamics. In the present study, flowfields of a single supersonic round jet (Mach 1.5) and dual impinging jets (consisting of a Mach 1.5 supersonic jet and an additional sonic jet) are explored. A microjet-based control method is applied to attenuate flow unsteadiness by modifying shear layer instability characteristics of the supersonic jet. Passive and active influence of the microjet hardware on acoustics are examined over a range of impingement distances (2.25D–10D) with a fine resolution (D/16) to obtain detailed resonance characteristics. Based on the resonance tone behavior as a function of impingement distances, detailed flowfield characteristics at certain impingement distances are investigated with the help of schlieren visualization, near-field acoustics, and unsteady surface pressure measurements. The effectiveness of the microjet flow control method in reducing noise is also evaluated in the flowfield of single and dual impinging jets. For single and dual impinging jets configuration, relative to their respective baseline cases, the microjet control on dual impinging jets shows better noise attenuation of overall sound pressure level within short impingement distances ([Formula: see text]).

Reduction of noise in cold and hot supersonic jets using active flow control guided by a genetic algorithm

“…The nozzle cross-section is presented schematically in figure 2(b), detailing the injection ports for the microjet actuators. Four rings of microjets are considered in this experiment, with one ring (R1) upstream of the nozzle throat by a streamwise distance s = 11 mm, two rings (R2, R3) downstream of the nozzle throat, both evenly spaced by s between the throat and the nozzle lip, and one ring (R4) injecting outside of the nozzle, replicating the arrangement typically found in previous studies for jet noise reduction (Krothapalli et al 2003;Henderson 2010;Song et al 2022). Ring R4 consists of microjets discharging at the shear layer of the main jet at an angle of 70 • with the free stream and at a 1.9 mm streamwise distance from the nozzle lip.…”

“…2003; Henderson 2010; Song et al. 2022). Ring R4 consists of microjets discharging at the shear layer of the main jet at an angle of with the free stream and at a 1.9 mm streamwise distance from the nozzle lip.…”

Acoustic characteristics of jets impinging on permeable plates

“…Elavarasan et al 29 destroyed the feedback loop by inserting a baffle plate near the nozzle exit in the outside ambient flow region. Kastner and Samimy 30 used Hartmann tube fluidic actuators and steady injection; Sarpotdar et al 31 employed Powered Resonance Tube (PRT) actuators whereas, Alvi and group 27,32 applied microjets to control the noise. Fluidic inserts are applied to reduce the noise produced by jets impinging on aircraft carrier deck.…”