Review of numerical simulations for high-speed, turbulent cavity flows
Introduction
Research into flows over weapons bays, more generally termed cavity flow, started as early as the 1940's. Experimental studies were commissioned by military companies such as English Electric [1], [2], [3] and Boeing [4] to study flow over weapons bays installed in aircraft such as the Canberra and the B47, and to study the impact of the cavity environment on stores and sensitive equipment contained within it.
The main focus of cavity research is still from the aerospace industry relating to understanding the mechanisms that drive the flow in a weapons bay. At high subsonic and supersonic speeds, deployment of stores is very difficult as the cavity environment becomes particularly harsh. Depending on the geometry of the weapons bays, problems could arise in relation to ejection of the stores through the turbulent air at the cavity opening or high intensity acoustic noise could damage the stores and the surrounding cavity structures. Therefore many military aircraft began loading stores onto pylons under the wings. This causes other issues, as external stores can account for up to 30% of the total aircraft drag and are also subjected to aerodynamic heating. In an attempt to overcome the store release problem, aircraft such as the F102 (Fig. 1(a)) had rigs installed to forcefully push the store through the cavity opening and away from the aircraft. However, such mechanisms were prone to jamming and so were not reliable. Therefore, effort was directed towards implementing flow control devices to make the cavity environment more suitable for internal store carriage and release. Modern military aircraft, such as the X-45 Uninhabited Combat Air Vehicles (UCAV) shown in Fig. 1(b), have put even more emphasis on internal store carriage due to the need for stealth characteristics.
Cavity flow research, however, is not exclusively military related. For example, an active area of research involves reducing the far-field noise produced by undercarriage wells when the landing gear is deployed. Around airports, the noise produced by these cavities equals that produced by the engine. Also, the automotive industry studies cavity flows in relation to sunroofs and open windows and door cavities, with the aim of reducing drag and the noise produced.
Since the first experimental studies, a large body of research has been performed in an attempt to better understand the complex fluid dynamics and aeroacoustics that are created when exposing a cavity to the free-stream flow. The Engineering Sciences Data Unit (ESDU) has produced summarising data sheets for the industrial community [7], [8], [9], [10], with both experimental and Computational Fluid Dynamics (CFD) results included. The paper provides a review of the literature in this area and additionally summarises an extensive work programme to add to the understanding of cavities and the influence of flow control devices. The full ‘effects of the control devices on the cavity flow-field are not fully understood and so understanding how simple devices, such as a spoiler at the leading edge, alter the cavity shear layer and cavity environment is key for developing more effective control devices. Finally, a set of computer animations are available on the Publisher's web pages to give interested readers further insight in the turbulent flow encountered in transonic cavity flows. A list of the available animations along with brief descriptions is presented as an appendix.
Section snippets
Literature review
The main objective of this literature review is to gain an understanding of published works related to cavity flow and learn from their finding about the basic flow physics of the problem and the influencing parameters. The process will also identify areas of the cavity flow problem that have not been fully documented. The review will focus on transonic cavity flow, with particular emphasis on passive flow control, the CFD methods used and cavities with stores.
The three main search engines used
Experimental study
Validation through comparisons to experimental data is an important part of post-processing numerical computations. To contribute to the demonstration of this, experimental data for two different cases is available. The first is the M219 cavity model, which is an idealised case in the sense that the cavity cross-section is orthogonal and it is surrounded by a flat plate. The second is the 1303 UCAV model, which has been tested with and without a weapons bay installed. Details of the experiments
Concluding remarks
The rich physics of cavity flows and the attempts to understand, simulate and control this unsteady turbulent flow were presented in this review. A wealth of experimental data has so far been reported in the literature with several of these sets freely available. The experiments provided substantial insight in cavity flows and also allowed for the detailed validation of predictions obtained with theoretical analyses as well as computational fluid dynamics. High quality surveys of pressure
Acknowledgements
The financial support of the Engineering and Physical Sciences Research Council through Grant EP/C533380/1 is gratefully acknowledged. The authors would like to extend their gratitude to Trevor Birch of DSTL for providing the experimental data. The use of the HECToR system as part of the 2nd Applied Aerodynamics Consortium of UK is also acknowledged.
References (247)
- et al.
Flow induced pressure oscillations in shallow cavities
Journal of Sound and Vibration
(1971) - et al.
Direct computation of noise radiated by the flow past a cavity
Comptes Rendus Academie des Sciences, Acoustics, Waves, Vibrations
(2000) - et al.
The prediction of laminarization with a two-equation model of turbulence
International Journal of Heat and Mass Transfer
(1972) - et al.
Attenuation of cavity flow oscillation through leading edge flow control
Journal of Sound and Vibration
(1999) - et al.
On a mechanism of stabilizing turbulent free shear layers in cavity flows
Computers and Fluids
(2007) - Electric E. Pressure plotting of bulkheads fore and Aft of bomb bay with bomb doors open. Technical Report WT Rep. AX9,...
- Electric E. Canberra. Investigation into flow in and around the bomb bay. Technical Report WT Rep. AX61, English...
- Electric E. Investigation into the effect of depth–length ratio on the incremental drag of a bomb bay. Technical Report...
- Norton D. Investigation of B47 Bomb Bay Buffet, Technical Report Doc. No. D12675, Boeing Airplane Co.;...
- Image of F-102 Delta Dagger, 〈http://www.aerospaceweb.org/question/history/q0185.shtml〉;...
Mode-switching and nonlinear effects in compressible flow over a cavity
Physics of Fluids
Joint time-frequency analysis
Experimental investigation of oscillations in flows over shallow cavities
AIAA Journal
An investigation of separated flows—part I: the pressure field
Journal of the Aerospace Sciences
Application of an acoustic analogy to PIV data from rectangular cavity flows
Experiments in Fluids
On self-sustained oscillations in two-dimensional compressible flow over rectangular cavities
Journal of Fluid Mechanics
Analysis of turbulent boundary layers
Analyses of pressure oscillations in an open cavity
AIAA Journal
Numerical simulation of supersonic flow over a three-dimensional cavity
AIAA Journal
Computational and experimental investigation of cavity flow-fields
AIAA Journal
Navier–Stokes calculations of transonic flows past cavities
Journal of Fluids Engineering, Transactions of the ASME
Flow-field simulation about the stratospheric observatory for infrared astronomy
Journal of Aircraft
Algebraic turbulence model simulations of supersonic open-cavity flow physics
AIAA Journal
A comparison of baldwin-lomax turbulence models for 2-D open cavity computations
AIAA Journal
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