Surface Pressure Fluctuations Due to an Impinging Supersonic Underexpanded Jet

2010 ◽  
Author(s):  
Binu Pundir ◽  
Manhar Dhanak
Keyword(s):  
Surface Pressure ◽  
Pressure Fluctuations ◽  
Underexpanded Jet ◽  
Supersonic Underexpanded Jet

Separated flow surface pressure fluctuations and pressure-velocity correlations on prolate spheroid

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 266-274
Author(s):  
Michael C. Goody ◽  
Roger L. Simpson ◽  
Christopher J. Chesnakas
Keyword(s):  
Surface Pressure ◽  
Pressure Fluctuations ◽  
Separated Flow ◽  
Prolate Spheroid ◽  
Flow Surface

Aeroacoustic analysis of slat tones

2021 ◽  
Vol 263 (1) ◽  
pp. 5650-5663
Author(s):  
Hasan Kamliya Jawahar ◽  
Syamir Alihan Showkat Ali ◽  
Mahdi Azarpeyvand
Keyword(s):  
Wavelet Transform ◽  
Surface Pressure ◽  
Wavelet Coefficient ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Stream Velocity ◽  
High Lift ◽  
Unsteady Surface Pressure ◽  
Slat Noise ◽  
Generation Mechanisms

Experimental measurements were carried out to assess the aeroacoustic characteristics of a 30P30N high-lift device, with particular attention to slat tonal noise. Three different types of slat modifications, namely slat cove filler, serrated slat cusp, and slat finlets have been experimentally examined. The results are presented for an angle of attack of α = 18 at a free-stream velocity of U = 30 m/s, which corresponds to a chord-based Reynolds number of Re = 7 x 10. The unsteady surface pressure near the slat region and far-field noise were made simultaneously to gain a deeper understanding of the slat noise generation mechanisms. The nature of the low-frequency broadband hump and the slat tones were investigated using higher-order statistical approaches for the baseline 30P30N and modified slat configurations. Continuous wavelet transform of the unsteady surface pressure fluctuations along with secondary wavelet transform of the broadband hump and tones were carried out to analyze the intermittent events induced by the tone generating resonant mechanisms. Stochastic analysis of the wavelet coefficient modulus of the surface pressure fluctuations was also carried out to demonstrate the inherent differences of different tonal frequencies. An understanding into the nature of the noise generated from the slat will help design the new generation of quite high-lift devices.

scholarly journals A three-dimensional theory of wind pumping

1991 ◽  
Vol 37 (125) ◽  
pp. 89-96 ◽  
Author(s):  
Garry K. C. Clarke ◽  
Edwin D. Waddington
Keyword(s):  
Heat Source ◽  
Surface Pressure ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Normal Component ◽  
Three Dimensional ◽  
Lower Atmosphere ◽  
Dimensional Theory ◽  
Theoretical Formulation ◽  
Near Surface

AbstractQuantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source.Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface.

Flow Stucture of Supersonic Underexpanded Jet With Microjets Injection

2013 ◽  
Vol 8 (1) ◽  
pp. 44-55
Author(s):  
Dmitriy Gubanov ◽  
Valeriy Zapryagaev ◽  
Nikolay Kiselev
Keyword(s):  
Flow Structure ◽  
Numerical Study ◽  
Mixing Layer ◽  
Supersonic Jet ◽  
Wave Structure ◽  
Streamwise Vortices ◽  
Jet Mixing ◽  
Underexpanded Jet ◽  
Supersonic Underexpanded Jet ◽  
The Impact

Experimental and numerical study of transversal microjets injection influence on the supersonic underexpanded jet flow structure has been performed. Data of measurements and calculation have acceptable agreement. Interaction of microjets with main supersonic jet sets to a decrease of an initial gasdynamic region. Microjets lead to a longitudinal streamwise vortices generation and a mushroom-like flow structures create on an external jet mixing layer. Dissipation of longitudinal streamwise vortices was observed at the second jet cell. Complex gasdynamic flow structure of the supersonic underexpanded jet interacting with supersonic microjets has been studied for the first time. This structure contains system of complex chock waves and expansion waves spreading from the position of the impact microjets/main jet localization place. Future of interaction process a chock-wave structure of main jet with additional shock waves has been studied

scholarly journals Numerical Analysis and Characterization of Surface Pressure Fluctuations of High-Speed Trains Using Wavenumber–Frequency Analysis

2019 ◽  
Vol 9 (22) ◽  
pp. 4924
Author(s):  
Lee ◽  
Cheong ◽  
Kim ◽  
Kim
Keyword(s):  
Flow Field ◽  
Open Field ◽  
Frequency Analysis ◽  
Surface Pressure ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Interior Noise ◽  
High Speed Train ◽  
Pressure Fields ◽  
Time Space

The high-speed train interior noise induced by the exterior flow field is one of the critical issues for product developers to consider during design. The reliable numerical prediction of noise in a passenger cabin due to exterior flow requires the decomposition of surface pressure fluctuations into the hydrodynamic (incompressible) and the acoustic (compressible) components, as well as the accurate computation of the near aeroacoustic field, since the transmission characteristics of incompressible and compressible pressure waves through the wall panel of the cabin are quite different from each other. In this paper, a systematic numerical methodology is presented to obtain separate incompressible and compressible surface pressure fields in the wavenumber–frequency and space–time domains. First, large eddy simulation techniques were employed to predict the exterior flow field, including a highly-resolved acoustic near-field, around a high-speed train running at the speed of 300 km/h in an open field. Pressure fluctuations on the train surface were then decomposed into incompressible and compressible fluctuations using the wavenumber–frequency analysis. Finally, the separated incompressible and compressible surface pressure fields were obtained from the inverse Fourier transform of the wavenumber–frequency spectrum. The current method was illustratively applied to the high-speed train HEMU-430X running at a speed of 300 km/h in an open field. The results showed that the separate incompressible and compressible surface pressure fields in the time–space domain could be obtained together with the associated aerodynamic source mechanism. The power levels due to each pressure field were also estimated, and these can be directly used for interior noise prediction.

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