Numerical Investigation of Supersonic Base Flow with Base Bleed

Sahu, Jubaraj; Heavey, Karen R.

doi:10.2514/2.3173

Cited by 29 publications

(15 citation statements)

References 14 publications

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“…The result is the incompressible form of Q, i.e. (9). Thus using (9) to identify vortical structures might still be viable, since it maintains its original meaning of a balance of rotation and strain while still being Galilean invariant.…”

Section: Influence Of Compressibilitymentioning

confidence: 99%

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Identification of large coherent structures in supersonic axisymmetric wakes

2009

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Direct numerical simulation data of supersonic axisymmetric wakes are analysed for the existence of large coherent structures. Wakes for a range of Reynolds numbers at Ma = 2.46 are considered with results being presented for cases at Re D = 30, 000 and 100,000. Criteria for identification of coherent structures in free-shear flows found in the literature are compiled and discussed, and the role of compressibility is addressed. In particular, the ability and reliability of visualisation techniques intended for incompressible shear-flows to educe meaningful structures in supersonic wakes is scrutinised. It is shown that some of these methods retain their usefulness for identification of vortical structures whose swirling rate is larger than the local compression and expansion rates in the flow field. Best 'visibility' of coherent structures is achieved by employing visualisation techniques and proper orthogonal decomposition in combination with the introduction of artificial perturbations (forcing of the wake). The existence of both helical and longitudinal structures in the shear layer and of hairpin-like structures in the developing wake is demonstrated. In addition, elongated tubes of streamwise vorticity are observed to emanate from the region of recirculating flow.

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Section: Influence Of Compressibilitymentioning

confidence: 99%

“…Methods employed include boat-tailing [5,6,7,8], base-bleeding [9,10,11], or active flow control [12]. Unfortunately, a reliable identification of the inherently three-dimensional coherent structures in this flow is difficult.…”

Section: Introductionmentioning

confidence: 99%

Identification of large coherent structures in supersonic axisymmetric wakes

2009

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“…RANS calculations were also employed for investigating different means of dragreduction, such as the effects of base bleed (see, e.g., Danberg & Nietubicz, 1992;Sahu & Heavey, 1995) and base burning (Nietubicz & Gibeling, 1993). The simulations showed a correct trend for the drag reduction when compared with experimental results but, in some cases, even global flow field characteristics such as the centerline velocity were not in good agreement with experiments.…”

Section: Turbulence Modellingmentioning

confidence: 99%

“…Furthermore, it is of great interest to understand how these structures are altered by passive control mechanisms, such as "boat-tailing" (see Bourdon & Dutton, 2000), "base bleed" (c.f. Cortwright & Schroeder, 1951;Reid & Hastings, 1959;Valentine & Przirembel, 1970;Sahu et al, 1985;Sahu & Heavey, 1995;Mathur & Dutton, 1996a,b), "base burning" (Hubbartt et al, 1981;Ding et al, 1992), etc. Such techniques were shown to modify the mean base flow and, as a consequence, the base-drag.…”

Section: Coherent Structuresmentioning

confidence: 99%

Simulation of Supersonic Base Flows: Numerical Investigations Using DNS, LES, and URANS

Fasel¹,

Sandberg²

2006

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Public Reporting Burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimate or any other aspect of this collection of information, including suggesstions for reducing this burden, Simulation of Supersonic Base Flows: Numerical Investigations Using DNS, LES, and URANS Report Title ABSTRACTTransitional and turbulent supersonic axisymmetric wakes were investigated by conducting various numerical experiments. The main objective was to identify hydrodynamic instability mechanisms in the flow at Mach number M = 2.46 for several Reynolds numbers, and relating these to coherent structures that are found from various visualization techniques. The premise for this approach is the assumption that flow instabilities lead to the formation of coherent structures. The effect of these structures on the mean flow is of particular interest, as they strongly affect the base drag. Three high-order accurate compressible codes were developed in cylindrical coordinates for this research: A spatial Navier-Stokes (N-S) code to conduct Direct Numerical Simulations (DNS), a linearized N-S code for linear stability investigations using two-dimensional basic states, and a temporal N-S code for performing local stability analyses. The ability of numerical simulations to deliberately exclude physical effects is exploited. This includes intentionally eliminating certain azimuthal/helical modes by employing DNS for various circumferential domain-sizes. With this approach, the impact of structures associated with certain modes on the global wake-behavior can be scrutinized. It is concluded that azimuthal modes with low wavenumbers are responsible for a flat mean base-pressure distribution and that k=2 and k=4 are the dominant modes in the trailing wake, producing a four-lobe wake pattern. Complementary spatial and temporal calculations are carried out to investigate whether instabilities are of local or global nature. Circumstatial evidence is presented that absolutely unstable global modes within the recirculation region coexist with convectively unstable shear-layer modes. The flow is found to be absolutely unstable with respect to modes k>0 for Re_D > 5,000 and with respect to the axisymmetric mode for Re_D>100,000. Furthermore, it is investigated whether flow control measures designed to weaken the naturally most significant modes can decrease the base drag. Finally, the novel Flow Simulation Methodology (FSM), using state-of-the-art turbulence closures, was shown to reproduce DNS results at a fraction of the computational cost.

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“…The assumption of drag modulation can be easily achieved using base bleeding technology, since the base pressure of a ballistic projectile can be changed over a wide range. 15,16) A typical value of the physical parameter selected for the vehicle is B m ¼ 12:76. This would provide a sensible aerodynamic force to start entry at the altitude of 120 km.…”

Section: Numerical Examplementioning

confidence: 99%

Explicit Guidance of Ballistic Entry Using Improved Matched Asymptotic Expansions

Kuo¹,

Liu²,

Chang³

2007

Trans. Japan Soc. Aero. S Sci.

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This study presents a means of explicit guidance for ballistic entry using an improved method of matched asymptotic expansions. The trajectory of ballistic entry into a planetary atmosphere is still an important and often critical phase of a mission. In the paper, feedback control via drag modulation is used to guide the vehicle during the atmospheric entry, whereas a matched asymptotic solution for the entry trajectory is available to aim the target. The feedback control ensures the stability of a trajectory around the nominal trajectory by compensating for the non-linear terms in the motion of the vehicle. Using the improved method of matched asymptotic expansions, the control algorithms for the guidance law are derived explicitly and tested against the 1976 U.S. Standard Atmosphere. Simulation results indicate that the control algorithms can effectively control the trajectories in the lower atmosphere under the targeting dispersions of atmospheric variations.

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Numerical Investigation of Supersonic Base Flow with Base Bleed

Cited by 29 publications

References 14 publications

Identification of large coherent structures in supersonic axisymmetric wakes

Identification of large coherent structures in supersonic axisymmetric wakes

Simulation of Supersonic Base Flows: Numerical Investigations Using DNS, LES, and URANS

Explicit Guidance of Ballistic Entry Using Improved Matched Asymptotic Expansions

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