ORCID Profile
0000-0002-7287-7659
Current Organisations
Indian Institute of Technology Delhi
,
University of Queensland
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Computational Fluid Dynamics | Interdisciplinary Engineering | Aerospace Engineering | Hypersonic Propulsion and Hypersonic Aerodynamics | Plasma Physics; Fusion Plasmas; Electrical Discharges | Turbulent Flows | Fluidisation and Fluid Mechanics | Aerospace engineering | Computational methods in fluid flow heat and mass transfer (incl. computational fluid dynamics) | Turbulent flows | Power and Energy Systems Engineering (excl. Renewable Power) | Approximation Theory and Asymptotic Methods | Acoustics and Noise Control (excl. Architectural Acoustics) | Hypersonic propulsion and hypersonic aerothermodynamics
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in Engineering | Space Transport | Expanding Knowledge in the Physical Sciences | Emerging Defence Technologies | Energy Transformation not elsewhere classified | Atmospheric Processes and Dynamics | Aerospace Equipment |
Related Links
Publications
Flow Field Manipulation via Fuel Injectors in Scramjets
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-03-2017
DOI: 10.2514/6.2017-2389
Characterization of a Spark Ignition System for Flameholding Cavities
Publisher: American Institute of Aeronautics and Astronautics
Date: 13-06-2014
DOI: 10.2514/6.2014-2242
Investigation of Combustion Mode Control in a Mach 8 Shape-Transitioning Scramjet
Publisher: American Institute of Aeronautics and Astronautics
Date: 15-09-2018
DOI: 10.2514/6.2018-5380
The Richtmyer–Meshkov instability in magnetohydrodynamics
Publisher: AIP Publishing
Date: 08-2009
DOI: 10.1063/1.3194303
Abstract: In ideal magnetohydrodynamics (MHD), the Richtmyer–Meshkov instability can be suppressed by the presence of a magnetic field. The interface still undergoes some growth, but this is bounded for a finite magnetic field. A model for this flow has been developed by considering the stability of an impulsively accelerated, sinusoidally perturbed density interface in the presence of a magnetic field that is parallel to the acceleration. This was accomplished by analytically solving the linearized initial value problem in the framework of ideal incompressible MHD. To assess the performance of the model, its predictions are compared to results obtained from numerical simulation of impulse driven linearized, shock driven linearized, and nonlinear compressible MHD for a variety of cases. It is shown that the analytical linear model collapses the data from the simulations well. The predicted interface behavior well approximates that seen in compressible linearized simulations when the shock strength, magnetic field strength, and perturbation litude are small. For such cases, the agreement with interface behavior that occurs in nonlinear simulations is also reasonable. The effects of increasing shock strength, magnetic field strength, and perturbation litude on both the flow and the performance of the model are investigated. This results in a detailed exposition of the features and behavior of the MHD Richtmyer–Meshkov flow. For strong shocks, large initial perturbation litudes, and strong magnetic fields, the linear model may give a rough estimate of the interface behavior, but it is not quantitatively accurate. In all cases examined the accuracy of the model is quantified and the flow physics underlying any discrepancies is examined.
Converging cylindrical magnetohydrodynamic shock collapse onto a power-law-varying line current
Publisher: Cambridge University Press (CUP)
Date: 16-03-2016
DOI: 10.1017/JFM.2016.138
Abstract: We investigate the convergence behaviour of a cylindrical, fast magnetohydrodynamic (MHD) shock wave in a neutrally ionized gas collapsing onto an axial line current that generates a power law in time, azimuthal magnetic field. The analysis is done within the framework of a modified version of ideal MHD for an inviscid, non-dissipative, neutrally ionized compressible gas. The time variation of the magnetic field is tuned such that it approaches zero at the instant that the shock reaches the axis. This configuration is motivated by the desire to produce a finite magnetic field at finite shock radius but a singular gas pressure and temperature at the instant of shock impact. Our main focus is on the variation with shock radius $r$ , as $r\\rightarrow 0$ , of the shock Mach number $M(r)$ and pressure behind the shock $p(r)$ as a function of the magnetic field power-law exponent ${\\it\\mu}\\geqslant 0$ , where ${\\it\\mu}=0$ gives a constant-in-time line current. The flow problem is first formulated using an extension of geometrical shock dynamics (GSD) into the time domain to take account of the time-varying conditions ahead of the converging shock, coupled with appropriate shock-jump conditions for a fast, symmetric MHD shock. This provides a pair of ordinary differential equations describing both $M(r)$ and the time evolution on the shock, as a function of $r$ , constrained by a collapse condition required to achieve tuned shock convergence. Asymptotic, analytical results for $M(r)$ and $p(r)$ are obtained over a range of ${\\it\\mu}$ for general ${\\it\\gamma}$ , and for both small and large $r$ . In addition, numerical solutions of the GSD equations are performed over a large range of $r$ , for selected parameters using ${\\it\\gamma}=5/3$ . The accuracy of the GSD model is verified for some cases using direct numerical solution of the full, radially symmetric MHD equations using a shock-capturing method. For the GSD solutions, it is found that the physical character of the shock convergence to the axis is a strong function of ${\\it\\mu}$ . For $0\\leqslant {\\it\\mu} /13$ , $M$ and $p$ both approach unity at shock impact $r=0$ owing to the dominance of the strong magnetic field over the lifying effects of geometrical convergence. When ${\\it\\mu}\\geqslant 0.816$ (for ${\\it\\gamma}=5/3$ ), geometrical convergence is dominant and the shock behaves similarly to a converging gas dynamic shock with singular $M(r)$ and $p(r)$ , $r\\rightarrow 0$ . For $4/13 {\\it\\mu}\\leqslant 0.816$ three distinct regions of $M(r)$ variation are identified. For each of these $p(r)$ is singular at the axis.
Stability of an Impulsively Accelerated Density Interface in Magnetohydrodynamics
Publisher: American Physical Society (APS)
Date: 14-09-2005
The Richtmyer–Meshkov instability of thermal, isotope and species interfaces in a five-moment multi-fluid plasma
Publisher: Cambridge University Press (CUP)
Date: 03-11-2022
DOI: 10.1017/JFM.2022.847
Abstract: The Richtmyer–Meshkov instability (RMI) results from the impulsive acceleration of a density interface where either it or the acceleration is perturbed. Density interfaces may arise due to a change in gas species, isotope, temperature or a combination of these. We computationally investigate the effect of interface type on the plasma RMI, which is relevant for a range of applications, including inertial confinement fusion. We simulate the evolution of single-mode perturbed thermal, species and isotope interfaces in an ideal ion–electron plasma using the multi-fluid plasma (MFP) model. We find that, in the MFP model, the evolution of different types of interface differs significantly, in contrast to single-fluid models where they behave similarly if the Atwood number is matched. The thermal and species interfaces produce the most severe response to shock acceleration, experiencing the secondary instabilities and enhanced primary mode growth. The isotope interface evolution is restrained in comparison with the former cases, resembling the response predicted by single-fluid models. The determining factor in the severity of the MFP RMI is the density ratio across the initial interface in the electron fluid, which is unity for an isotope interface. We observe that, as the density ratio across the electron interface decreases, so do the magnitudes of the self-generated fields and consequently the severity of the growth lification. Generally, the evolution of the RMI with different types of interface becomes more similar as the level of coupling between the ion and electron fluids is increased, characterised by reducing the plasma non-dimensional skin depth.
Simulation of Laser-Induced-Plasma Ignition in a Hypersonic Crossflow
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-07-2015
DOI: 10.2514/6.2015-3622
The sound generated by a square cylinder with a splitter plate at low Reynolds number
Publisher: Elsevier BV
Date: 07-2011
Effects of Oxygen Enrichment on Supersonic Combustion in a Mach 10 Scramjet
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2021
DOI: 10.2514/1.J059748
Effects of seed magnetic fields on magnetohydrodynamic implosion structure and dynamics
Publisher: AIP Publishing
Date: 12-2014
DOI: 10.1063/1.4902432
Abstract: The effects of various seed magnetic fields on the dynamics of cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Here, we present a fundamental investigation of this problem utilizing cylindrical and spherical Riemann problems under three seed field configurations to initialize the implosions. The resulting flows are simulated numerically, revealing rich flow structures, including multiple families of magnetohydrodynamic shocks and rarefactions that interact non-linearly. We fully characterize these flow structures, examine their axi- and spherisymmetry-breaking behaviour, and provide data on asymmetry evolution for different field strengths and driving pressures for each seed field configuration. We find that out of the configurations investigated, a seed field for which the implosion centre is a saddle point in at least one plane exhibits the least degree of asymmetry during implosion.
Magnetohydrodynamic Richtmyer–Meshkov instability under an arbitrarily oriented magnetic field
Publisher: AIP Publishing
Date: 06-2020
DOI: 10.1063/1.5142042
Abstract: The effect of an initially uniform magnetic field of arbitrary orientation on the Richtmyer–Meshkov instability in Hall-magnetohydrodynamics (MHD) and ideal MHD is considered. Attention is restricted to the case where the initial density interface has a single-mode sinusoidal perturbation in litude and is accelerated by a shock traveling perpendicular to the interface. An incompressible Hall-MHD model for this flow is developed by solving the relevant impulse-driven linearized initial value problem. The ideal MHD theory is naturally obtained by taking the limit of vanishing ion skin depth. It is shown that the out-of-plane magnetic field component normal to both the impulse and the interface perturbation does not affect the evolution of the flow. For all field orientations other than strictly out-of-plane, the growth of interface perturbations is suppressed. However, the suppression is most effective for near tangential fields but becomes less effective with increasing ion skin depth and Larmor radius. The modeled suppression mechanism is transport of vorticity along magnetic field lines via Alfvén fronts in ideal MHD, and via a dispersive wave system in Hall-MHD. Oscillation of the interface growth rate is caused by a continuous phase change of the induced velocities at the interface due to vorticity transport parallel to the perturbation direction in ideal MHD, while it can also result from interfacial vorticity production associated with the ion cyclotron effect in Hall-MHD with a finite Larmor radius. The limiting flow behavior of a large ion-skin-depth is explored. To assess the accuracy and appropriateness of the incompressible model, its ideal MHD predictions are compared to the results of the corresponding shock-driven nonlinear compressible simulations.
Hypersonic viscous drag reduction via multiporthole injector arrays
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2013
DOI: 10.2514/1.B34782
Simulation of Laser-Induced Plasma Ignition in a Hypersonic Crossflow
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 08-2018
DOI: 10.2514/1.J055821
Magnetohydrodynamic shock refraction at an inclined density interface
Publisher: AIP Publishing
Date: 03-2022
DOI: 10.1063/5.0078545
Abstract: Shock wave refraction at a sharp density interface is a classical problem in hydrodynamics. Presently, we investigate the strongly planar refraction of a magnetohydrodynamic (MHD) shock wave at an inclined density interface. A magnetic field is applied that is initially oriented either perpendicular or parallel to the motion of incident shock. We explore flow structure by varying the magnitude of the magnetic field governed by the non-dimensional parameter β∈(0.5,106) and the inclination angle of density interface α∈(0.30,1.52). The regular MHD shock refraction process results in a pair of outer fast shocks (reflected and transmitted) and a set of inner nonlinear magneto-sonic waves. By varying magnetic field (strength and direction) and inclination interface angle, the latter waves can be slow shocks, slow expansion fans, intermediate shocks, or slow-mode compound waves. For a chosen incident shock strength and density ratio, the MHD shock refraction transitions from regular (all nonlinear waves meeting at a single point) into irregular when the inclined density interface angle is less than a critical value. Irregular refraction patterns are not amenable to an analytical solution, and hence, we have obtained irregular refraction solutions by numerical simulations. Since the MHD shock refraction is self-similar, we further explore by converting the initial value problem into a boundary value problem (BVP) by a self-similar coordinate transformation. The self-similar solution to the BVP is numerically solved using an iterative method and implemented using the p4est adaptive mesh framework. The simulation shows that a Mach stem occurs in an irregular MHD shock refraction, and the flow structure can be an MHD equivalent to a single Mach reflection irregular refraction and convex-forwards irregular refraction that occur in hydrodynamic case. For Mach number M = 2, both analytical and numerical results show that perpendicular magnetics fields suppress the regular to irregular transition compared to the corresponding hydrodynamic case. As Mach number decreased, it is possible that strong perpendicular magnetics promote the regular to irregular transition, while moderate perpendicular magnetics suppress this transition compared to the corresponding hydrodynamic case.
Managing the dark side of digitalization in the future of work: A fuzzy TISM approach
Publisher: Elsevier BV
Date: 10-2022
Convergent, functionally independent signaling by mu and delta opioid receptors in hippocampal parvalbumin interneurons
Publisher: Cold Spring Harbor Laboratory
Date: 24-04-2021
DOI: 10.1101/2021.04.23.441199
Abstract: Functional interactions between G protein-coupled receptors are poised to enhance neuronal sensitivity to neuromodulators and therapeutic drugs. Mu and Delta opioid receptors (MORs and DORs) can interact when overexpressed in the same cells, but whether co-expression of endogenous MORs and DORs in neurons leads to functional interactions is unclear. Here, we show that both MORs and DORs inhibit parvalbumin-expressing basket cells (PV-BCs) in hippoc al CA1 through partially occlusive signaling pathways that terminate on somato-dendritic potassium channels and presynaptic calcium channels. Using photoactivatable opioid neuropeptides, we find that DORs dominate the response to enkephalin in terms of both ligand-sensitivity and kinetics, which may be due to relatively low expression levels of MOR. Opioid-activated potassium channels do not show heterologous desensitization, indicating that MORs and DORs signal independently. In a direct test for heteromeric functional interactions, the DOR antagonist TIPP-Psi does not alter the kinetics or potency of either the potassium channel or synaptic responses to photorelease of the MOR agonist DAMGO. Thus, despite largely redundant and convergent signaling, MORs and DORs do not functionally interact in PV-BCs. These findings imply that crosstalk between MORs and DORs, either in the form of physical interactions or synergistic intracellular signaling, is not a preordained outcome of co-expression in neurons.
On the magnetohydrodynamic limits of the ideal two-fluid plasma equations
Publisher: AIP Publishing
Date: 12-2018
DOI: 10.1063/1.5067387
Abstract: The two-fluid plasma equations describing a magnetized plasma, originating from truncating moments of the Vlasov-Boltzmann equation, are increasingly used to describe an ion-electron plasma whose transport phenomena occur on a time scale slower and a length scale longer than those of particle collisions. A similar treatment under more stringent constraints gives the single-fluid magnetohydrodynamic (MHD) equations for low-frequency macroscopic processes. Since both stem from kinetic theory, the two-fluid plasma and MHD equations are necessarily related to each other. Such a connection is often established via ad hoc physical reasoning without a firm analytical foundation. Here, we perform a sequence of formal expansions for the dimensionless ideal two-fluid plasma equations with respect to limiting values of the speed-of-light c, the ion-to-electron mass ratio M, and the plasma skin depth dS. Several different closed systems of equations result, including separate systems for each limit applied in isolation and those resulting from limits applied in combination, which correspond to the well-known Hall-MHD and single-fluid ideal MHD equations. In particular, it is shown that while the zeroth-order description corresponding to the c→∞ limit, with M and dS fixed, is strictly charge neutral, it nonetheless uniquely determines the perturbation charge non-neutrality at the first order. Furthermore, the additional M→∞ limit is found to be not required to obtain the single-fluid MHD equations despite being essential for the Hall-MHD system. The hierarchy of systems presented demonstrates how plasmas can be appropriately modeled in situations where only one of the limits applies, which lie in the parameter space in between where the two-fluid plasma and Hall-MHD models are appropriate.
Hypersonic inlet for a laser powered propulsion system
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3657023
Experimental Design of a Cavity Flameholder in a Mach 8 Shape-Transitioning Scramjet
Publisher: American Institute of Aeronautics and Astronautics
Date: 13-06-2014
DOI: 10.2514/6.2014-2953
Aeolian tones generated by a square cylinder with a detached flat plate
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 02-2013
DOI: 10.2514/1.J051378
Spontaneous singularity formation in converging cylindrical shock waves
Publisher: American Physical Society (APS)
Date: 23-07-2018
Numerical investigation of the heat and mass transfer analogy in rarefied gas flows
Publisher: Elsevier BV
Date: 06-2015
Ignition Experiments of Hydrocarbons in a Mach 8 Shape-Transitioning Scramjet Engine
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2016
DOI: 10.2514/1.B36099
Investigation of Combustion Mode Control in a Mach 8 Shape-Transitioning Scramjet
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 07-2019
DOI: 10.2514/1.J057999
Improving Scramjet Performance Through Flow Field Manipulation
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2018
DOI: 10.2514/1.B36772
Influence of common modeling choices for high-speed transverse jet-interaction simulations
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2013
DOI: 10.2514/1.B34750
Tailored Fuel Injection for Performance Enhancement in a Mach 12 Scramjet Engine
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-07-2015
DOI: 10.2514/6.2015-3614
Hybrid Reynolds-Averaged and Large-Eddy Simulation of Mixing in an Axisymmetric Scramjet
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-09-2012
DOI: 10.2514/6.2012-5902
The effect of collisions on the multi-fluid plasma Richtmyer–Meshkov instability
Publisher: AIP Publishing
Date: 02-2023
DOI: 10.1063/5.0132461
Abstract: The Richtmyer–Meshkov instability (RMI) results from the impulsive acceleration of a density interface where the RMI itself or the acceleration is perturbed. The RMI is ubiquitous in shock environments and may arise due to an interface of fluid species, isotopes, temperature, or more. The plasma RMI can be significantly influenced by electromagnetic effects and can be modeled more accurately by a multi-fluid plasma (MFP) model rather than conventional magnetohydrodynamics, though with increased computational expense. MFP modeling of the plasma RMI has revealed many phenomena but has only been completed within the ideal regime. Modeling the effects of elastic collisions is vital for understanding the behavior of the instability in a dense plasma. The Braginskii transport coefficients provide theoretically based relations modeling thermal equilibration, inter-species drag, viscous momentum- and energy-transfers, and thermal conductivity. Our numerical simulations of the MFP RMI with these relations show that the key changes from the ideal case are (1) reduction of relative motion between the ion and electron fluids (consequently affecting the self-generated electromagnetic fields), (2) introduction of anisotropy in momentum and energy via transport coefficients, and (3) d ing of high frequency electromagnetic waves and plasma waves. Under the conditions studied, the net effect is a reduction in the MFP RMI litude width and the growth rate to levels approaching the neutral fluid instability, as well as a reduction in large scale perturbations along the ion fluid density interface, a positive for inertial confinement fusion efforts. There are, however, two important caveats: small-scale density interface perturbations remain, and the conditions simulated are a few relevant points in a large parameter space that requires further investigation.
The state of the art of innovation management: insights from a retrospective review of theEuropean Journal of Innovation Management
Publisher: Emerald
Date: 22-09-2022
DOI: 10.1108/EJIM-07-2022-0361
Abstract: Innovation goes beyond creation, concentrating on enhancement, which is essential for advancement. Since 1998, the European Journal of Innovation Management ( EJIM ) has been a leading forum dedicated to thought leadership and research on the advances in innovation management. Given that EJIM has run over two decades, the time is now opportune to reflect on the journal's contributions to innovation management. Thus, this paper aims to retrospectively review the productivity, impact and knowledge of innovation management research in EJIM . This paper adopts a bibliometric methodology to engage in a retrospective review of EJIM . The bibliographic data of 757 papers published in EJIM from 1998 to 2021 were retrieved from Scopus and analyzed using performance analysis and science mapping techniques. The productivity (publication) and impact (citation) of innovation management research curated by EJIM have grown prolifically over time. Though EJIM operates with a European title, the journal receives and publishes contributions worldwide (e.g. Asia, Europe, North America, South America and Oceania). Noteworthily, the knowledge of innovation management research in EJIM can be ided into four categories: basic themes (general), which comprise innovation, open innovation, new product development and product and process innovation motor themes (well-developed), which consist of organizational culture and innovation and leadership and creativity niche themes (very specialized), which include dynamic capabilities and business model innovation and emerging or declining themes (weakly developed or marginalized), which is made up of research and development (R& D) and green innovation. This paper offers a seminal retrospection of EJIM and the journal's productivity, impact and contribution to innovation management.
Singularity formation on perturbed planar shock waves
Publisher: Cambridge University Press (CUP)
Date: 08-05-2018
DOI: 10.1017/JFM.2018.263
Abstract: We present an analysis that predicts the time to development of a singularity in the shape profile of a spatially periodic perturbed, planar shock wave for ideal gas dynamics. Beginning with a formulation in complex coordinates of Whitham’s approximate model geometrical shock dynamics (GSD), we apply a spectral treatment to derive the asymptotic form for the leading-order behaviour of the shock Fourier coefficients for large mode numbers and time. This is shown to determine a critical time at which the coefficients begin to decay, with respect to mode number, at an algebraic rate with an exponent of $-5/2$ , indicating loss of analyticity and the formation of a singularity in the shock geometry. The critical time is found to be inversely proportional to a representative measure of perturbation litude $\\unicode[STIX]{x1D716}$ with an explicit analytic form for the constant of proportionality in terms of gas and shock parameters. To leading order, the time to singularity formation is dependent only on the first Fourier mode. Comparison with results of numerical solutions to the full GSD equations shows that the predicted critical time somewhat underestimates the time for shock–shock (triple-point) formation, where the latter is obtained by post-processing the numerical GSD results using an edge-detection algorithm. Aspects of the analysis suggest that the appearance of loss of analyticity in the shock surface may be a precursor to the first appearance of shock–shocks, which may account for part of the discrepancy. The frequency of oscillation of the shock perturbation is accurately predicted. In addition, the analysis is extended to the evolution of a perturbed planar, fast magnetohydrodynamic shock for the case when the external magnetic field is aligned parallel to the unperturbed shock. It is found that, for a strong shock, the presence of the magnetic field produces only a higher-order correction to the GSD equations with the result that the time to loss of analyticity is the same as for the gas-dynamic flow. Limitations and improvements for the analysis are discussed, as are comparisons with the analogous appearance of singularity formation in vortex-sheet evolution in an incompressible inviscid fluid.
Magnetohydrodynamic implosion symmetry and suppression of Richtmyer-Meshkov instability in an octahedrally symmetric field
Publisher: American Physical Society (APS)
Date: 26-01-2017
Blast Wave-Induced Mixing in a Laser Ignited Hypersonic Flow
Publisher: ASME International
Date: 20-12-2019
DOI: 10.1115/1.4038397
Abstract: A laser ignition system suitable for a hypersonic scramjet engine is considered. Wall-modeled large eddy simulation (LES) is used to study a scramjet-like geometry with a single hydrogen injector on the inlet, at a Mach 8 flight condition with a total enthalpy of 2.5 MJ. Detailed chemical kinetics and high fidelity turbulence modeling are used. The laser forms a kernel of high temperature plasma inside the fuel plume that briefly ignites the flow and leads to massive disruption of the flow structures around the jet, due to the expanding plasma kernel driving a blast wave that collides with the surrounding flow. The blast wave produces vorticity as it passes through the fuel–air interface, but comparably less than that produced by the jetting of the hot gas affected by the laser as it expands outward into the crossflow. The remnant of the plasma rolls up into a powerful vortex ring and noticeably increases the fuel plume area and the volume of well mixed reactants present in the simulation. These results indicate that the laser ignition system does more than just supply the energy to ignite the flow it also substantially alters the flow structure and the mixing process.
High Mach Number Operation of Accelerator Scramjet Engine
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2023
DOI: 10.2514/1.A35511
Abstract: Accelerating scramjet engines could efficiently propel the second stage of an access to space system. A scramjet engine designed to accelerate from Mach 5 to 10 requires geometric features to assist performance at either end of the trajectory, which negatively affects the performance at the opposite end. This work discusses the necessity of these features and their implications on performance. A fueling configuration for the high Mach number operation of an accelerator scramjet is introduced. This injection scheme was designed for a ground test model, at small scale. The high Mach number performance of the engine is categorized at on- and off-design conditions. Its extension to a full-scale engine was also investigated. The full-scale engine generates thrust at Mach 10, despite a reduced area-ratio nozzle. Across all conditions simulated, the engine and fueling scheme has robust performance, although it required a reduction of inlet fueling at scale.
Performance of high mach number scramjets - Tunnel vs flight
Publisher: Elsevier BV
Date: 05-2018
Solving the discrete S-model kinetic equations with arbitrary order polynomial approximations
Publisher: Elsevier BV
Date: 02-2014
Revised model coefficients for vibrational relaxation in a nitrogen–oxygen gas mixture
Publisher: Springer Science and Business Media LLC
Date: 04-08-2012
Computational Investigation of Thermal Nonequilibrium Effects in Scramjet Geometries
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2013
DOI: 10.2514/1.B34722
On the role of Riemann solvers in Discontinuous Galerkin methods for magnetohydrodynamics
Publisher: Elsevier BV
Date: 02-2010
Characterization of Supersonic Turbulent Combustion in a Mach-10 Scramjet Combustor
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2020
DOI: 10.2514/1.J058671
The transverse field Richtmyer-Meshkov instability in magnetohydrodynamics
Publisher: AIP Publishing
Date: 2014
DOI: 10.1063/1.4851255
Abstract: The magnetohydrodynamic Richtmyer-Meshkov instability is investigated for the case where the initial magnetic field is unperturbed and aligned with the mean interface location. For this initial condition, the magnetic field lines penetrate the perturbed density interface, forbidding a tangential velocity jump and therefore the presence of a vortex sheet. Through simulation, we find that the vorticity distribution present on the interface immediately after the shock acceleration breaks up into waves traveling parallel and anti-parallel to the magnetic field, which transport the vorticity. The interference of these waves as they propagate causes the perturbation litude of the interface to oscillate in time. This interface behavior is accurately predicted over a broad range of parameters by an incompressible linearized model derived presently by solving the corresponding impulse driven, linearized initial value problem. Our use of an equilibrium initial condition results in interface motion produced solely by the impulsive acceleration. Nonlinear compressible simulations are used to investigate the behavior of the transverse field magnetohydrodynamic Richtmyer-Meshkov instability, and the performance of the incompressible model, over a range of shock strengths, magnetic field strengths, perturbation litudes and Atwood numbers.
Converging cylindrical shocks in ideal magnetohydrodynamics
Publisher: AIP Publishing
Date: 09-2014
DOI: 10.1063/1.4894743
Abstract: We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale \\documentclass[12pt]{minimal}\\begin{document}$R=\\sqrt{\\mu _0 _0}\\,I/(2\\,\\pi )$\\end{document}R=μ0 0I/(2π) where I is the current, μ0 is the permeability, and p0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The erging magnetic field then slows the shock Mach number growth producing a maximum followed by monotonic reduction towards magnetosonic conditions, even as the shock accelerates toward the axis. A parameter space of initial shock Mach number at a given radius is explored and the implications of the present results for inertial confinement fusion are discussed.
Convergent, functionally independent signaling by mu and delta opioid receptors in hippocampal parvalbumin interneurons
Publisher: eLife Sciences Publications, Ltd
Date: 17-11-2021
DOI: 10.7554/ELIFE.69746
Abstract: Functional interactions between G protein-coupled receptors are poised to enhance neuronal sensitivity to neuromodulators and therapeutic drugs. Mu and delta opioid receptors (MORs and DORs) can interact when overexpressed in the same cells, but whether co-expression of endogenous MORs and DORs in neurons leads to functional interactions is unclear. Here, in mice, we show that both MORs and DORs inhibit parvalbumin-expressing basket cells (PV-BCs) in hippoc al CA1 through partially occlusive signaling pathways that terminate on somato-dendritic potassium channels and presynaptic calcium channels. Using photoactivatable opioid neuropeptides, we find that DORs dominate the response to enkephalin in terms of both ligand sensitivity and kinetics, which may be due to relatively low expression levels of MOR. Opioid-activated potassium channels do not show heterologous desensitization, indicating that MORs and DORs signal independently. In a direct test for heteromeric functional interactions, the DOR antagonist TIPP-Psi does not alter the kinetics or potency of either the potassium channel or synaptic responses to photorelease of the MOR agonist [ d -Ala 2 , NMe-Phe 4 , Gly-ol 5 ]enkephalin (DAMGO). Thus, aside from largely redundant and convergent signaling, MORs and DORs do not functionally interact in PV-BCs in a way that impacts somato-dendritic potassium currents or synaptic transmission. These findings imply that cross-talk between MORs and DORs, either in the form of physical interactions or synergistic intracellular signaling, is not a preordained outcome of co-expression in neurons.
Fundamental Scramjet Combustion Experiments Using Hydrocarbon Fuel
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2019
DOI: 10.2514/1.B37472
Numerical investigation of curved channel Knudsen pump performance
Publisher: Elsevier BV
Date: 09-2014
Behavior of Multiple-Jet Interactions in a Hypersonic Boundary Layer
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2015
DOI: 10.2514/1.B35298
Richtmyer-Meshkov instability of an imploding flow with a two-fluid plasma model
Publisher: American Physical Society (APS)
Date: 20-11-2020
Special Section on the 15th International Workshop on the Physics of Compressible Turbulent Mixing
Publisher: ASME International
Date: 20-12-2017
DOI: 10.1115/1.4038402
Effects of Hydrogen Fuel Injection in a Mach 12 Scramjet Inlet
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 10-2015
DOI: 10.2514/1.J053819
Supersonic combustion of hydrocarbons in a shape-transitioning hypersonic engine
Publisher: Elsevier BV
Date: 2017
The Effect of Wall and Fuel Temperature in a Mach 6 Scramjet Engine
Publisher: The University of Queensland
Date: 2020
DOI: 10.14264/7760714
Supersonic Boundary-Layer Combustion via Multiporthole Injector Arrays
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 12-0010
DOI: 10.2514/1.J053817
LES Simulation of Sound Generated by a Cylinder Wake and its Interaction with Shock Waves
Publisher: The University of Queensland
Date: 2020
DOI: 10.14264/9760DBE
Fundamental Scramjet Combustion Experiments using Hydrocarbon Fuel
Publisher: American Institute of Aeronautics and Astronautics
Date: 15-09-2018
DOI: 10.2514/6.2018-5201
Measurements and analysis of hypersonic tripped boundary layer turbulence
Publisher: Springer Science and Business Media LLC
Date: 14-07-2021
The Richtmyer-Meshkov instability of a double-layer interface in convergent geometry with magnetohydrodynamics
Publisher: AIP Publishing
Date: 13-04-2018
DOI: 10.1016/J.MRE.2018.01.003
Abstract: The interaction between a converging cylindrical shock and double density interfaces in the presence of a saddle magnetic field is numerically investigated within the framework of ideal magnetohydrodynamics. Three fluids of differing densities are initially separated by the two perturbed cylindrical interfaces. The initial incident converging shock is generated from a Riemann problem upstream of the first interface. The effect of the magnetic field on the instabilities is studied through varying the field strength. It shows that the Richtmyer-Meshkov and Rayleigh-Taylor instabilities are mitigated by the field, however, the extent of the suppression varies on the interface which leads to non-axisymmetric growth of the perturbations. The degree of asymmetry of the interfacial growth rate is increased when the seed field strength is increased.
The magnetised Richtmyer–Meshkov instability in two-fluid plasmas
Publisher: Cambridge University Press (CUP)
Date: 30-09-2020
DOI: 10.1017/JFM.2020.661
Low Reynolds number flow over a square cylinder with a splitter plate
Publisher: AIP Publishing
Date: 03-2011
DOI: 10.1063/1.3563619
Abstract: Flows over a square cylinder of side length D with and without a splitter plate are numerically investigated at a Reynolds number of 150. The length of the splitter plate is varied systematically from L=0.5D to L=6D so the sensitivity of the flow structure to the inclusion of the splitter plate can be inspected. It is found that the splitter plate introduces a strong hydrodynamic interaction to the near wake of the cylinder and the length of the plate affects significantly the flow structure. The behavior of the flow can be grouped into three regimes. For short plate lengths (0≲L≲D), the free shear layers are convected further downstream before rolling up when the plate length is increased. For intermediate plate lengths (1.25D≲L≲4.75D), a secondary vortex is clearly visible around the trailing edge of the splitter plate and the shear layers begin to roll up closer to the trailing edge. For long plate lengths (L≳5D), a regime is observed in which the free shear layers reattach to the splitter plate. The study also proposes the minimum wake half-width as the length scale for a possible universal Strouhal number, which is found to be valid for 0≤L≤4D.
Regular shock refraction at an oblique planar density interface in magnetohydrodynamics
Publisher: Cambridge University Press (CUP)
Date: 2005
Low Reynolds number flow over a square cylinder with a detached flat plate
Publisher: Elsevier BV
Date: 08-2012
Impulse-driven Richtmyer-Meshkov instability in Hall-magnetohydrodynamics
Publisher: American Physical Society (APS)
Date: 11-10-2019
Correction: Fundamental Scramjet Combustion Experiments Using Hydrocarbon Fuel
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2020
DOI: 10.2514/1.B37472.C1
Simulations of Mixing in an Inlet-Fueled Axisymmetric Scramjet
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 12-2013
DOI: 10.2514/1.J052480
Comparison of ethylene combustion mechanisms for the simulation of a supersonic combustion experiment
Publisher: Elsevier BV
Date: 12-2021
Hypersonic Turbulent Boundary-Layer Fuel Injection and Combustion: Skin-Friction Reduction Mechanisms
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2013
DOI: 10.2514/1.J052041
Richtmyer–Meshkov instability of a thermal interface in a two-fluid plasma
Publisher: Cambridge University Press (CUP)
Date: 03-11-2017
DOI: 10.1017/JFM.2017.693
Abstract: We computationally investigate the Richtmyer–Meshkov instability of a density interface with a single-mode perturbation in a two-fluid, ion–electron plasma with no initial magnetic field. Self-generated magnetic fields arise subsequently. We study the case where the density jump across the initial interface is due to a thermal discontinuity, and select plasma parameters for which two-fluid plasma effects are expected to be significant in order to elucidate how they alter the instability. The instability is driven via a Riemann problem generated precursor electron shock that impacts the density interface ahead of the ion shock. The resultant charge separation and motion generates electromagnetic fields that cause the electron shock to degenerate and periodically accelerate the electron and ion interfaces, driving Rayleigh–Taylor instability. This generates small-scale structures and substantially increases interfacial growth over the hydrodynamic case.
Thermofluidic compression effects to achieve combustion in a low-compression scramjet engine
Publisher: Springer Science and Business Media LLC
Date: 02-12-2017
Noise Generated in a Scramjet Combustor
Publisher: American Institute of Aeronautics and Astronautics
Date: 19-01-2023
DOI: 10.2514/6.2023-0314
Tailored Fuel Injection for Performance Enhancement in a Mach 12 Scramjet Engine
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2019
DOI: 10.2514/1.B36794
Enhanced Supersonic Combustion Targeting Combustor Length Reduction in a Mach 12 Scramjet
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 10-2018
DOI: 10.2514/1.J057417
Geometrical shock dynamics for magnetohydrodynamic fast shocks
Publisher: Cambridge University Press (CUP)
Date: 12-12-2016
DOI: 10.1017/JFM.2016.767
Abstract: We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as $\\unicode[STIX]{x1D716}^{-1}$ , where $\\unicode[STIX]{x1D716}$ is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. ( Phys. Fluids , vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock.
Numerical Simulation of Compressible Magnetohydrodynamic Plasma Flow in a Curcuit Breaker
Publisher: American Institute of Physics
Date: 2008
DOI: 10.1063/1.2990896
Numerical investigation into the performance of alternative Knudsen pump designs
Publisher: Elsevier BV
Date: 02-2016
Evolution of a shock generated by an impulsively accelerated, sinusoidal piston
Publisher: Cambridge University Press (CUP)
Date: 26-11-2021
DOI: 10.1017/JFM.2020.775
Magnetohydrodynamic Drag Force Measurements in an Expansion Tube
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-2018
DOI: 10.2514/6.2018-3755
Characteristics of Cascaded Fuel Injectors Within an Accelerating Scramjet Combustor
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 12-2016
DOI: 10.2514/1.J054815
Linear simulations of the cylindrical Richtmyer-Meshkov instability in magnetohydrodynamics
Publisher: AIP Publishing
Date: 03-2016
DOI: 10.1063/1.4943162
Abstract: Numerical simulations and analysis indicate that the Richtmyer-Meshkov instability (RMI) is suppressed in ideal magnetohydrodynamics (MHD) in Cartesian slab geometry. Motivated by the presence of hydrodynamic instabilities in inertial confinement fusion and suppression by means of a magnetic field, we investigate the RMI via linear MHD simulations in cylindrical geometry. The physical setup is that of a Chisnell-type converging shock interacting with a density interface with either axial or azimuthal (2D) perturbations. The linear stability is examined in the context of an initial value problem (with a time-varying base state) wherein the linearized ideal MHD equations are solved with an upwind numerical method. Linear simulations in the absence of a magnetic field indicate that RMI growth rate during the early time period is similar to that observed in Cartesian geometry. However, this RMI phase is short-lived and followed by a Rayleigh-Taylor instability phase with an accompanied exponential increase in the perturbation litude. We examine several strengths of the magnetic field (characterized by β=2pBr2) and observe a significant suppression of the instability for β ≤ 4. The suppression of the instability is attributed to the transport of vorticity away from the interface by Alfvén fronts.
Measurements of Free stream Density Fluctuations in the T4 Stalker Tube
Publisher: American Institute of Aeronautics and Astronautics
Date: 27-05-2023
DOI: 10.2514/6.2023-3031
Effects of magnetic fields on magnetohydrodynamic cylindrical and spherical Richtmyer-Meshkov instability
Publisher: AIP Publishing
Date: 10-2015
DOI: 10.1063/1.4932110
Abstract: The effects of seed magnetic fields on the Richtmyer-Meshkov instability driven by converging cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Two different seed field configurations at various strengths are applied over a cylindrical or spherical density interface which has a single-dominant-mode perturbation. The shocks that excite the instability are generated with appropriate Riemann problems in a numerical formulation and the effect of the seed field on the growth rate and symmetry of the perturbations on the density interface is examined. We find reduced perturbation growth for both field configurations and all tested strengths. The extent of growth suppression increases with seed field strength but varies with the angle of the field to interface. The seed field configuration does not significantly affect extent of suppression of the instability, allowing it to be chosen to minimize its effect on implosion distortion. However, stronger seed fields are required in three dimensions to suppress the instability effectively.
Comparison of discrete BGK-Shakhov system with DSMC
Publisher: AIP
Date: 2012
DOI: 10.1063/1.4769540
Rarefied, superorbital flows in an expansion tube
Publisher: Emerald
Date: 06-2004
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California Institute Of Technology
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