Blunt-Body Paradox and Improved Application of Transient-Growth Framework

Paredes, Pedro; Choudhari, Meelan M.; Li, Fēi

doi:10.2514/1.j056678

Cited by 17 publications

(47 citation statements)

References 33 publications

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“…40 The face diameter is D = 2R = 0.0762 m and the remaining dimensions are scaled according to Hollis,40 resulting in a sphere radius of R s = 0.09144 m. The flow conditions at Mach 6 match those of a wind-tunnel experiment in the Adjustable Contour Expansion (ACE) facility at the National Aerothermochemistry Laboratory (NAL) of Texas A&M University. 13,14 Paredes et al 12…”

Section: A Tamu Capsulementioning

confidence: 99%

“…IV and compared to corresponding data for the TAMU capsule. The additional data set for the HLB capsule is used to further substantiate the value of the power-law exponent of the wall to boundary-layer edge temperature ratio of the correlation for roughness-induced transition that was originally proposed by Reshotko & Tumin 11 and the slightly different value recently derived by Paredes et al 12 based on optimal transient-growth data for the TAMU capsule. In Sec.…”

Section: Introductionmentioning

confidence: 96%

“…Since the RT correlation depends only on those two scalings, the modified correlation remained close to the original correlation of Reshotko & Tumin despite the improvements in the calculation of optimal growth factors. Paredes et al 12 also pointed out that the magnitude of transient growth up to the measured transition locations at the experiments at TAMU was rather small, which raises questions regarding the relevance of the optimal growth paradigm.…”

Section: Introductionmentioning

confidence: 99%

“…However, the optimal transient-growth approach of Reshotko & Tumin included some simplifying assumptions. Therefore, Paredes et al 12 used an improved framework of optimal transient-growth analysis which removed the shortcomings of the approach of Reshotko & Tumin and applied it to the scale model of the Orion CEV geometry studied in the Mach 6 ACE wind tunnel at Texas A&M University (TAMU). 13,14 In these experiments, the effect of uniformly distributed surface roughness on transition onset was systematically studied.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, the effects of surface temperature and unit Reynolds number on the optimal transient growth are investigated and compared with the results for the TAMU capsule as a similar Mach number but lower Reynolds numbers. 12 Furthermore, the steady disturbance flow field introduced by the roughness patch on the HLB capsule and its interaction with additional unsteady disturbances is studied by direct numerical simulations (DNS) in order to investigate possible modal or non-modal disturbance growth mechanisms either in the vicinity of the roughness patch or in the wake region behind the patch. The different numerical approaches used are briefly introduced in Sec.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of Roughness Effects on Transition on Spherical Capsules

Hein

Theiß

Giovanni

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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The state of the boundary layer on space re-entry vehicles significantly affects the design of the thermal protection system. However, the physical mechanism that leads to the laminar-turbulent boundary-layer transition on blunt spherical capsules remains an open question in literature. This work numerically assesses the potential of roughness-induced non-modal disturbance growth on re-entry capsules with a spherical-section forebody by optimal transient-growth theory and direct numerical simulation. Two different sets of wind-tunnel experiments are considered. Optimal transient-growth studies have been performed for the blunt capsule experiments at Mach 5.9 in the Hypersonic Ludwieg tube Braunschweig (HLB) of the Technische Universität Braunschweig. In some of these measurements, the capsule model was equipped with a specifically designed patch of distributed micron-sized surface roughness. The transient-growth results for the HLB capsule are compared to corresponding numerical data for a Mach 6 blunt capsule experiment in the Adjustable Contour Expansion (ACE) facility of the Texas A&M University (TAMU) at lower Reynolds number. Similar trends are observed for both configurations. In particular, a rather low maximum energy gain is noted for the surface temperature conditions of the experiments. It is shown that the surface temperature dependence of the optimal transient-growth results is very similar for both capsule configurations. Moreover, the generation of stationary disturbances by well-defined roughness patches on the capsule surface is studied for the conditions of the HLB experiment using direct numerical simulations (DNS). To help explain the observed laminar-turbulent transition downstream of the roughness patch in some of the HLB capsule experiments, additional simulations were carried out to study the evolution of unsteady perturbations within the steady disturbance flow field due to the roughness patch. However, the DNS did not provide any indication of modal or non-modal disturbance growth in the wake of the roughness patch, and hence, the physical mechanism underlying the observed onset of transition remains unknown.

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Section: A Tamu Capsulementioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Numerical Investigation of Roughness Effects on Transition on Spherical Capsules

Hein

Theiß

Giovanni

et al. 2018

2018 AIAA Aerospace Sciences Meeting

Self Cite

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Special issue on the fluid mechanics of hypersonic flight

Theofilis

Pirozzoli

Martin

2022

Theor. Comput. Fluid Dyn.

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Flow phenomena on maneuverable vehicles that fly at hypersonic speeds and altitudes that reach the Earth's upper stratosphere and lower mesosphere pose challenges that collectively form one of the present-day research frontiers of Fluid Mechanics. Research agencies around the world have realized the multiple benefits derived from transitioning a deeper understanding of hypersonic flow phenomena to actual flying platforms, and support for hypersonic research has increased substantially in the last decade. The result can be seen in Fig. 1, showing the distribution over years and originating countries of a total of 26,300 peer-reviewed research papers that have been published since the word hypersonic first appeared in the literature in the early 1940s and have this word in their title. Early peak activity subsided after the Moon landing, but soon picked up in the early 80s and again around the turn of the century, growing monotonically to the present day. As also shown in Fig. 1, a breakdown by country of origin reveals that two-thirds of the total number of hypersonic publications originate from the USA and China, giving rise to concerns raised by strategic think-tanks [57] and policy advisers [61] regarding potential misuse of hypersonic technology.Hypersonic research has not always come to the limelight on account of potential strategic conflicts. The high plateau in number of papers published around the 1990s, shown in the left plate of Fig. 1, corresponds to intense activity that took place on the crest of the success of the early Space Shuttle flights, relating to the new Orient Express [47] of hypersonic travel. Large (and largely drawing board) projects involving substantial research into hypersonic flow physics, namely the National Aerospace Plane in the USA, Buran in the final years of the Soviet Union, HOTOL in the UK, Hermes in France and Sänger in Germany, alongside lower-scale efforts in India and Brazil, all testified to a time of optimism regarding hypersonic travel in a civilian transport V. Theofilis

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