Direct numerical simulation of a hypersonic transitional boundary layer at suborbital enthalpies

Renzo, Mario Di; Urzay, Javier

doi:10.1017/jfm.2020.1144

Cited by 39 publications

(30 citation statements)

References 71 publications

(134 reference statements)

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“…Figure 15( a ) (displayed in external units for better clarity) shows that the estimation fails at the peak of , located at , since the coexistence of null temperature gradient and turbulent heat flux causes an overshoot. Such a behaviour was previously observed by Duan & Martín (2011 b ) and Di Renzo & Urzay (2021) (for a discussion about the validity of this assumption for adiabatic hypersonic boundary layers, see Passiatore et al. 2021).…”

Section: Resultssupporting

confidence: 74%

“…In figure 11( a ), a peak emerges on each side of the location (), as classically observed for wall-cooled TBLs (Duan, Beekman & Martín 2010; Zhang et al. 2018; Di Renzo & Urzay 2021). The predominance of the outer r.m.s.…”

Section: Resultssupporting

confidence: 71%

“…The prescribed edge conditions of , and are representative of those downstream of a shock wave generated by a sharp wedge flying at at an altitude of approximately 36 km. The stagnation enthalpy at the edge of the boundary layer is , a value comparable to those of the high-enthalpy cases considered by Duan & Martín (2011 b ) and Di Renzo & Urzay (2021). Air at such free-stream conditions is supposed to be in thermochemical equilibrium (, , being the th species molar fraction).…”

Section: Methodssupporting

confidence: 75%

“…Neither chemical activity nor thermal relaxation process should substantially alter the validity of the transformation since a certain degree of decoupling is observed between the thermochemical and turbulent activities, as previously noticed by Passiatore et al. (2021) and Di Renzo & Urzay (2021).

Figure 4.Wall-normal profiles of ( a ) the van Driest-transformed streamwise velocity, ( b ) Trettel & Larsson's transformation and ( c ) comparison between Trettel & Larsson transformation and total-stress-based scaling of Griffin et al.…”

Section: Resultsmentioning

confidence: 65%

“…The interaction of finite-rate chemistry with transitional and turbulent spatially developing boundary layers was recently investigated by Passiatore et al. (2021) and Di Renzo & Urzay (2021), who isolated the effects of chemical non-equilibrium on pseudo-adiabatic and cooled TBLs, respectively. In both studies, the effect of thermal non-equilibrium was neglected since the selected edge conditions were not expected to promote significant vibrational relaxation phenomena.…”

Section: Introductionmentioning

confidence: 99%

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Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers

et al. 2022

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A hypersonic, spatially evolving turbulent boundary layer at Mach 12.48 with a cooled wall is analysed by means of direct numerical simulations. At the selected conditions, massive kinetic-to-internal energy conversion triggers thermal and chemical non-equilibrium phenomena. Air is assumed to behave as a five-species reacting mixture, and a two-temperature model is adopted to account for vibrational non-equilibrium. Wall cooling partly counteracts the effects of friction heating, and the temperature rise in the boundary layer excites vibrational energy modes while inducing mild chemical dissociation of oxygen. Vibrational non-equilibrium is mostly driven by molecular nitrogen, characterized by slower relaxation rates than the other molecules in the mixture. The results reveal that thermal non-equilibrium is sustained by turbulent mixing: sweep and ejection events efficiently redistribute the gas, contributing to the generation of a vibrationally under-excited state close to the wall, and an over-excited state in the outer region of the boundary layer. The tight coupling between turbulence and thermal effects is quantified by defining an interaction indicator. A modelling strategy for the vibrational energy turbulent flux is proposed, based on the definition of a vibrational turbulent Prandtl number. The validity of the strong Reynolds analogy under thermal non-equilibrium is also evaluated. Strong compressibility effects promote the translational–vibrational energy exchange, but no preferential correlation was detected between expansions/compressions and vibrational over-/under-excitation, as opposed to what has been observed for unconfined turbulent configurations.

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Section: Resultssupporting

confidence: 74%

Section: Resultssupporting

confidence: 71%

Section: Methodssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

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Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers

et al. 2022

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Numerical strategy to perform direct numerical simulations of hypersonic shock/boundary-layer interaction in chemical nonequilibrium

Volpiani

2021

Shock Waves

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Literature regarding hypersonic shock/boundary-layer interaction (SBLI) is mostly restricted to calorically perfect gases, even though this condition is far from reality when temperature rises. Hightemperature effects alter physical and transport properties of the fluid, due to vibrational excitation and gas dissociation, and chemical reactions must be considered in order to compute the flow field. In this work, a code for hypersonic aerodynamics with reactions using parallel machines (CHARLIE ) is described and a numerical methodology is developed to perform direct numerical simulations of shock/boundary-layer interaction in chemical nonequilibrium. The numerical scheme and the characterization of non-reflecting boundary conditions are addressed. Results show that the flow properties differ considerably if chemical reactions are taken into account. A direct numerical simulation of a shock interacting with a turbulent boundary-layer in the hypersonic regime with high-temperature effects is also presented for the first time. Keywords numerical methodology • hypersonic flow • shock/boundary-layer interactions • chemical nonequilibrium 1 IntroductionUnderstanding shock/boundary layer interactions (SBLI) is an imperative step to correctly predict the performance of hypersonic vehicles. These complex phenomena can affect considerably the aerodynamic drag and in a more drastic scenario, be responsible for low-frequency unsteadiness, leading to structural failure, loss of the control surfaces or the unstart in an engine intake. SBLI also increases the wall heat flux, a key factor when designing thermal protection systems. To ensure the safety of the space shuttle these systems are most of the time specified with a large safety factor, with the drawback of carrying extra weight. Therefore, the accurate prediction of aerodynamic heating in hypersonic flight is an important step in the design process, which can reduce the weight of the vehicle, increase the payload and enhance fuel efficiency, amongst various advantages.The majority of the work dealing with shock/boundary-layer interaction considers a calorically perfect gas [

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A High-Order Hybrid Numerical Scheme for Hypersonic Flow Over A Blunt Body

Chen

Fang

Moulinec

et al. 2022

Flow Turbulence Combust

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A hybrid scheme is developed for direct numerical simulations of hypersonic flows over a blunt body. The scheme switches to the first-order AUSMPW+ scheme near the bow shock to provide sufficient dissipation to handle the carbuncle phenomenon. In the smooth part of the computational domain, a sixth-order central scheme with an eighth-order low-pass filter is adopted to provide high spatial accuracy to resolve turbulence. The hybrid scheme is shown to be able to obtain smooth and accurate predictions of laminar hypersonic flows over a blunt body. Using the hybrid scheme, a direct numerical simulation of a Mach 6 hypersonic flow over a circular cylinder is conducted. The result shows the turbulent structures in the near-wall region are well resolved by the hybrid scheme, and the bow shock is also captured without introducing any numerical oscillations. With the boundary layer transition on the cylinder's surface, the simulation indicates that the heat flux peak shifts from the stagnation point to the transitional zone and its peak value is increased by 50%.

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Direct numerical simulation of a hypersonic transitional boundary layer at suborbital enthalpies

Abstract: Abstract

Cited by 39 publications

References 71 publications

Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers

Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers

Numerical strategy to perform direct numerical simulations of hypersonic shock/boundary-layer interaction in chemical nonequilibrium

A High-Order Hybrid Numerical Scheme for Hypersonic Flow Over A Blunt Body

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