Numerical Study of Strong Interplay Between Cavity and Store During Launching

AbstractNumerical investigation of the strong interplay between a cavity and a store under supersonic inflow condition is conducted by using Improved Delayed Detach-Eddy Simulation (IDDES). Pressure fluctuations in the cavity are analyzed with smooth pseudo Winger-Vile distribution method and the time-frequency features are obtained. The effects of fluctuating flow inside the cavity on the aerodynamic loads of the store are also studied. It was shown that when the store is falling through the shear layer, the self-sustained oscillation loop is destroyed and the cavity tone vanishes. Vortex structures concentrate in the back of the cavity, as a result the noise levels at the rear of the cavity increase. After the store falls out of the cavity, the oblique shock wave formed at store's head interferences with the shear layer, which changes the cavity tone frequencies. The forces and moments acting on the store fluctuate strongly influenced by highly unsteady flow-field. Affected by oblique shock and the impact of shear layer, the store's pitch up angle keeps rising up and reaches to 24° at its maximum.

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Instabilities in oblique shock wave/laminar boundary-layer interactions

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.729 ◽

2016 ◽

Vol 789 ◽

pp. 1-35 ◽

Cited By ~ 25

Author(s):

F. Guiho ◽

F. Alizard ◽

J.-Ch. Robinet

Keyword(s):

Boundary Layer ◽

Shock Wave ◽

Shear Layer ◽

Laminar Boundary Layer ◽

Oblique Shock ◽

Oblique Shock Wave ◽

Two Dimensional ◽

Linear Framework ◽

Displacement Thickness ◽

The Impact

The interaction of an oblique shock wave and a laminar boundary layer developing over a flat plate is investigated by means of numerical simulation and global linear-stability analysis. Under the selected flow conditions (free-stream Mach numbers, Reynolds numbers and shock-wave angles), the incoming boundary layer undergoes separation due to the adverse pressure gradient. For a wide range of flow parameters, the oblique shock wave/boundary-layer interaction (OSWBLI) is seen to be globally stable. We show that the onset of two-dimensional large-scale structures is generated by selective noise amplification that is described for each frequency, in a linear framework, by wave-packet trains composed of several global modes. A detailed analysis of both the eigenspectrum and eigenfunctions gives some insight into the relationship between spatial scales (shape and localization) and frequencies. In particular, OSWBLI exhibits a universal behaviour. The lowest frequencies correspond to structures mainly located near the separated shock that emit radiation in the form of Mach waves and are scaled by the interaction length. The medium frequencies are associated with structures mainly localized in the shear layer and are scaled by the displacement thickness at the impact. The linear process by which OSWBLI selects frequencies is analysed by means of the global resolvent. It shows that unsteadiness are mainly associated with instabilities arising from the shear layer. For the lower frequency range, there is no particular selectivity in a linear framework. Two-dimensional numerical simulations show that the linear behaviour is modified for moderate forcing amplitudes by nonlinear mechanisms leading to a significant amplification of low frequencies. Finally, based on the present results, we draw some hypotheses concerning the onset of unsteadiness observed in shock wave/turbulent boundary-layer interactions.

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Effect of Struts Downstream of Low Pressure Turbine on Tone Noise Generation

Volume 2D: Turbomachinery ◽

10.1115/gt2020-15575 ◽

2020 ◽

Author(s):

Ravil Nigmatullin ◽

Larisa Terenteva

Keyword(s):

Stokes Equations ◽

Numerical Study ◽

Pressure Fluctuations ◽

Three Dimensional ◽

Maximum Amplitude ◽

Low Pressure ◽

Mode Analysis ◽

Low Pressure Turbine ◽

Noise Characteristics ◽

The Impact

Abstract In the present work a numerical study of tone noise generated by the last stage of the Low Pressure Turbine (LPT) of an aircraft engine designed for a medium-haul civilian aircraft has been conducted. The impact of struts on the tone noise characteristics is estimated. The method for turbine noise calculation is based on numerical integration of the three-dimensional unsteady Reynolds averaged Navier-Stokes equations using an in-house code for multi-stage simulations. To obtain the tonal characteristics of the generated noise, the pressure pulsation field is processed using the methods of radial mode analysis. The calculated pressure fluctuations contain all possible components of the frequency-modal spectrum, which allows us to determine profile of the generated tone noise and find propagating modes with maximum amplitude. The calculations showed that the presence of struts leads to a scattering effect, which manifests as an increase in the number of generated circumferential modes. These circumferential modes propagate both downstream and upstream and increase the total level of tone noise. The amplitudes of circumferential modes related to two different types of the interaction, rotor-stator and rotor-struts, are compared.

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A numerical study of oblique shock wave reflections over wedges in an ideal quantum gas

Shock Waves ◽

10.1007/s00193-008-0150-1 ◽

2008 ◽

Vol 18 (3) ◽

pp. 193-204 ◽

Cited By ~ 1

Author(s):

J. C. Huang ◽

T. Y. Hsieh ◽

J. Y. Yang ◽

K. Takayama

Keyword(s):

Shock Wave ◽

Numerical Study ◽

Oblique Shock ◽

Oblique Shock Wave ◽

Quantum Gas ◽

Wave Reflections ◽

Ideal Quantum

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Visualization and analysis of flow structures in an open cavity

Modern Physics Letters B ◽

10.1142/s0217984918400109 ◽

2018 ◽

Vol 32 (12n13) ◽

pp. 1840010

Author(s):

Jun Liu ◽

Jinsheng Cai ◽

Dangguo Yang ◽

Junqiang Wu ◽

Xiansheng Wang

Keyword(s):

Numerical Study ◽

Pressure Fluctuations ◽

Leading Edge ◽

Open Cavity ◽

Flow Structures ◽

Sustained Oscillation ◽

Multi Scale ◽

Numerical Visualization ◽

New Type ◽

Attached Vortex

A numerical study is performed on the supersonic flow over an open cavity at Mach number of 1.5. A newly developed visualization method is employed to visualize the complicated flow structures, which provide an insight into major flow physics. Four types of shock/compressive waves which existed in experimental schlieren are observed in numerical visualization results. Furthermore, other flow structures such as multi-scale vortices are also obtained in the numerical results. And a new type of shocklet which is beneath large vortices is found. The shocklet beneath the vortex originates from leading edge, then, is strengthened by successive interactions between feedback compressive waves and its attached vortex. Finally, it collides against the trailing surface and generates a large number of feedback compressive waves and intensive pressure fluctuations. It is suggested that the shocklets beneath vortex play an important role of cavity self-sustained oscillation.

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A numerical study of oblique shock-wave reflections with experimental comparisons

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1985.0028 ◽

1985 ◽

Vol 398 (1814) ◽

pp. 117-140 ◽

Cited By ~ 49

Keyword(s):

Shock Wave ◽

Numerical Study ◽

Wedge Angle ◽

Quantitative Agreement ◽

Oblique Shock ◽

Computational Method ◽

Oblique Shock Wave ◽

Wave Reflections ◽

Inviscid Flows ◽

Reflection Transition

A direct comparison is made for several occurrences of oblique shock-wave reflections between interferometric results obtained at the University of Toronto Institute for Aerospace Studies (UTIAS) 10 cm x 18 cm hyper-velocity shock tube and numerical results obtained by using a current computational method for solving the Euler equations. Very good qualitative agreement is obtained for equilibrium and frozen flow fields except in small regions where the experiments were dominated by viscous flow. The quantitative agreement is very close in some cases but can be out by 10–15% in cases with non-equilibrium flow or viscous structures or both. Additional parametrized sequences of calculations are presented to assess the utility of the present numerical method in constructing the various reflection–transition lines for perfect inviscid flows in the shock-wave Mach number, wedge-angle ( M s , θ w )-plane, and the validity of the ‘boundary-layer defect’ theory.

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The interaction of an oblique shock wave with a laminar boundary layer revisited. An experimental and numerical study

Journal of Fluid Mechanics ◽

10.1017/s0022112087000946 ◽

1987 ◽

Vol 177 ◽

pp. 247-263 ◽

Cited By ~ 45

Author(s):

G. Degrez ◽

C. H. Boccadoro ◽

J. F. Wendt

Keyword(s):

Boundary Layer ◽

Shock Wave ◽

Laminar Boundary Layer ◽

Stokes Equations ◽

Numerical Study ◽

Pressure Ratio ◽

Oblique Shock ◽

Oblique Shock Wave ◽

Approximate Factorization ◽

Pressure Distributions

An investigation of an oblique shock wave/laminar boundary layer interaction is presented. The Mach number was 2.15, the Reynolds number was 105 and the overall pressure ratio was 1.55. The interation has been demonstrated to be laminar and nominally two-dimensional. Experimental results include pressure distributions on the plate and single component laser-Doppler velocimetry velocity measurements both in the attached and separated regions.The numerical results have been obtained by solving the full compressible Navier-Stokes equations with the implicit approximate factorization algorithm by Beam & Warming (1980). Comparison with experimental data shows good agreement in terms of pressure distributions, positions of separation and reattachment and velocity profiles.

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A Numerical Study on Flow Characteristics of Super Sonic Diffuser for the Position and Nose Cone Angles of Center Body

Volume 3A: Fluid Applications and Systems ◽

10.1115/ajkfluids2019-5430 ◽

2019 ◽

Author(s):

Sunghun Lee ◽

Myeongwon Lee ◽

Jin Park ◽

Hongjip Kim

Keyword(s):

Shock Wave ◽

Supersonic Flow ◽

Numerical Study ◽

Flow Characteristics ◽

Oblique Shock ◽

Oblique Shock Wave ◽

Starting Point ◽

Nose Cone ◽

Supersonic Diffuser ◽

Center Body

Abstract The center body diffuser is one of supersonic diffuser that can simulate high-altitude environment. There is center-body structure inside the diffuser, and a complex fluid flow is occurred inside the diffuser because of the interaction of the CB structure with gas exhausted from the nozzle outlet. In this study, starting point and flow characteristics of diffuser were investigated according to changing the CB nose cone angle and the length of distance between nozzle and CB structure. The differences of the supersonic flow were compared through each parameter of CB distance and CB nose angle. First changed parameter was length between nozzle and CB. According to the length of distance between nozzle and CB, axial momentum was developed and oblique shock wave moved front of CB from end of CB nose cone. Also, when CB position was located on a certain length, starting point of CBD decreased. Next change parameter was angle of CB nose cone. According to the angle raised, angle of oblique shock wave was raised and radial momentum of supersonic diffuser developed. But, according to radial momentum of supersonic flow over certain angle, the starting pressure of CBD increased. Because axial momentum which isolated vacuum chamber from atmospheric pressure. Through these CFD analysis results, it was shown that angle and length of distance between nozzle and CB influent performance of CBD.

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