Experimental Study on Acoustic Phenomena of Supersonic Jet Impinging on Inclined Flat Plate

Abstract

Acoustic and flow fields of a Mj = 1.8 correctly-expanded jet impinging on a 45 ○ inclined flat plate are investigated experimentally. In the experiments, microphone measurement, Schlieren visualization, and wall static pressure measurement on the inclined plate surface are conducted for different nozzle-plate distances. When the nozzle-plate distance is 5D, two types of acoustic waves, whose characteristics are different in propagation directions, spectra, and source locations, are observed. One propagates in the 30 ○ direction from the inclined plate surface, and the other propagates in the 75 ○ direction. When the nozzleplate distance is varied, the change of the intensities of those two types of acoustic waves is observed, and the correlation between the acoustic waves and the shock structures of the flow field is discussed.

Validation of Overset Discontinuous Galerkin and Hybrid RANS/LES Method for Jet Noise Prediction

“…Indeed the jet potential core length of x/D ∼ 10 is well predicted, and the jet is correctly expanded with no intense shock predicted inside the potential core zone (though some shock train is still formed inside the jet) as is well observed in the experimental studies. 39 In comparison with the measured Mach profile, the predicted Mach number falls off more quickly outside of the jet potential core zone with the HRLES simulations doing slightly better than the (steady) RANS simulations. Our preliminary simulations carried out in larger (both axially and radially) domains indicated that the current domain size is adequate.…”

“…(16). This issue as well as Loci/CHEM validation against the free jet acoustic data available in the literature 39,43 are planned for detailed consideration during next stages of this study.…”

“…The computational domain extends axially over 20D downstream from the nozzle exit and over 12D radially. The plenum chamber stagnation conditions are set to 0.585 MPa at room temperature, 39 and an isentropic inflow boundary condition is used at the inner plenum wall to maintain constant entropy 42 and allow steadystate flow out of the nozzle to be achieved. The predicted Mach number profiles obtained for the free jet conditions using (steady) RANS and (unsteady) HRLES are shown in Fig.…”

Study on Acoustic Prediction and Reduction of Epsilon Launch Vehicle at Liftoff

“…Validation and verification of the computational code are performed extensively by comparing the measured results of the Me=1.8 perfectly expanded cold impinging jet taken by Nakanishi et al [21,22,40], and measured results taken in the SMAP testing campaign for the free jet, impinging jet on the 45-degree-inclined flat plate, and practical launch pad configurations. In this report, a validation study using the microphone results measured of the practical launch pad configuration shown in Fig.…”

“…14(a), are dominant. [17][18][19][20][21][22] The acoustic wave due to the jet impingement propagates omnidirectionally from the vicinity of the impingement region, and determines the acoustic environment surrounding the vehicle. On the other hand, the Mach wave radiation from the wall jet has a strong directivity at roughly 50 degree from the wall jet axis, so that the effect on the vehicle must be small.…”