A. Chpoun

Université d'Évry-Val-d'Essonne · Laboratoire LMEE - Laboratoire de Mécanique et Energétique d’Evry

The present paper focuses on the impact of transverse injection on DBN behavior during its ascent and descent in the atmosphere. The influence of the secondary injection settling chamber (cavity) volume is discussed. The positive influence of the cavity volume on the DBN behavior during transition phases has been exposed, and its effects during ret...

Experiments on an axisymmetric dual-bell nozzle were performed at EDITH nozzle test facility of CNRS in Orl´eans, France. The main purpose of the study was to explore the possibility of controlling the flow regime transition by a secondary fluidic injection in the dual bell nozzle. The main focus of the present paper is to investigate the impact of...

The effect of rotational nonequilibrium on the macroscopic parameters of the flow behind a normal shock wave in oxygen gas flow has been examined. The electron thermal equilibrium was taken into account where the electron temperature was equal to the vibrational temperature according to Park’s assumption. Therefore, only the effect of rotational no...

In this study, the effect of rotational nonequilibrium on the macroscopic parameters of the flow behind a normal shock wave in oxygen and nitrogen gas flow has been examined. Comparison between three chemical kinetic models including Park89, Park93, and Dunn-Kang was used to describe the chemical nonequilibrium. The obtained results show the signif...

In this study, the effects of different thermo-chemical models on the macroscopic parameters of the flow behind a strong shock wave have been examined. The effect of the geometric average temperature proposed by Park and the effect of the electronic energy are also presented, and two CVD vibration-dissociation coupling models including those of Par...

The aim of this study is to optimize sensor networks for fast deployment in order to reconstruct an unknown source of intentional or accidental release in local urban topography. In such emergency circumstances, only the meteorological conditions are available in real time and the network deployed must be efficient enough regardless of a source's p...

In this study, a one-dimensional post-normal shock solver in hypersonic ionized air flow was developed to study the effect of the physical-chemical phenomena that occur at high temperature. To simulate this case, the upstream air flow is considered with 2 species (21% of O 2 and 79% of N 2 ). Behind the shock wave, the Park’s chemical kinetics mode...

The aim of this research is to optimize a methodology used in eco-design, that so-called Life Cycle Assessment (LCA), in order to increase its representativeness when evaluating systems. This optimization consists of introducing temporal factors in the environmental impact assessment. This process is called Dynamic Life Cycle Assessment (DLCA). It...

Method for controlling regime mode transition in multi-stage particularly dual-bell nozzles with integrated fluidic thrust vectoring properties

Dual-bell axisymmetric propulsive nozzle, as the most prominent altitude compensating nozzle concept has been investigated for transition modes and effects. Experimental and numerical investigations show that dual-bell nozzle can be very effective for desired large envelope launcher stage trajectories. Transition regimes are studied in the high alt...

In the aeronautical and aerospace industries, the flow configurations where an incident oblique shock wave impinges upon a boundary layer are very common. The supersonic flow around an aircraft, in a rocket nozzle or in a supersonic inlet are some examples among others.

In the aeronautical and aerospace industries, the flow configurations where an incident oblique shock have impinges upon a boundary layer are very common. Under certain circumstances (High Mach number, large shock angle ...), the interaction between the incident shock wave and the boundary layer may create an unsteady separation bubble. This separa...

The aim of this paper is to present a new aeroelastic stability model taking into account the viscous effects for a supersonic nozzle flow in overexpanded regimes. This model is inspired from the Pekkari model which was developed initially for perfect fluid flow. The new model called the “modified Pekkari model” (MPM) considers a more realistic wal...

The transverse injection in a supersonic cross-flow is problematic which can be encountered in several aerodynamic applications such as fuel injection in scramjet combustor, missile control, drag reduction, and thrust vector control. In recent years, an extended analytical, numerical, and experimental work has been carried out by the authors [1, 2]...

The aim of this study is to develop a new approach for the aeroelastic stability analysis of a flexible overexpanded rocket nozzle using numerical fluid–structure coupling via the transpiration method. The method consists of a weak coupling between two numerical codes; one is dedicated to the computational structural dynamics (CSD) and the other to...

In the context of industrial risk management, occurring at urban scales, decision-making processes remain subject to various sources of uncertainty and required accurate and realistic models to simulate atmospheric pollutant diffusion both in forward and inverse modelling. In the frame of this work, the three-dimensional (3-D) computational fluid d...

In the context of industrial risk management, occurring at urban scales, decision-making processes remain subject to various sources of uncertainty and required accurate and realistic models to simulate atmospheric pollutant diffusion both in forward and inverse modelling. In the frame of this work, the three-dimensional (3-D) computational fluid d...

Secondary transverse injection into the divergent section of an axisymmetric convergent–divergent propulsive nozzle is investigated for the fluidic thrust vectoring effects. Coupled experimental and numerical cold-flow investigation on the number of cases and aspects was conducted in the framework of a French microsatellite launcher program. Five e...

Au cours des ces dernières années, il y a eu des efforts concertés pour développer des microdrones MAV (Micro-Air-Vehicles) en raison de leurs nombreux domaines d’application et aussi vu leur faible coût de production par rapport aux drones. Sachant que ce type d’avions souffre beaucoup de la limitation de la marge de fonctionnement à cause de leur...

Interactions between shock waves and boundary layers (SWBLI) are encountered in many industrial applications dealing with supersonic flows (aircraft design, rocket nozzles...). If the shock is strong enough, those interactions may cause the boundary layer separation yielding dynamic loads, increased heat fluxes and pressure fluctuations. Even if th...

The aim of this study is to develop a new approach for the aeroelastic stability analysis of a flexible over-expanded rocket nozzle using numerical fluid-structure coupling via the transpiration method. The method consists of a weak coupling between two numerical codes; one is dedicated to the Computational Structural Dynamics (CSD) and the other t...

The transverse injection in a supersonic cross-flow is a problematic which can be encountered in several aerodynamic applications such as fuel injection in scramjet combustor, missile control, drag reduction and thrust vector control. In recent years, an extended analytical, numerical and experimental work has been carried out by the authors [1,2]...

The aim and the originality of our study reside in the development of new models of aeroelastic stability called the "Modified Pekkari Model" (MPM). Inspired by the initial Pekkari model dedicated to perfect fluid flows using a simplified wall pressure distribution (Fig.1a), the new models are able to implement more complex pressure distributions a...

The aim and the originality of our study reside in the development of new models of aeroelastic stability called the "Modified Pekkari Model" (MPM). Inspired by the initial Pekkari model dedicated to perfect fluid flows using a simplified wall pressure distribution (Fig.1a), the new models are able to implement more complex pressure distributions a...

The aim of this paper is to present and compare two different approaches for aeroelastic stability analysis of a flexible over-expanded rocket nozzle. The first approach is based on the aeroelastic stability models developed in a previous work, while the second uses the numerical fluid–structure coupling via the transpiration method. The aeroelasti...

The cross injection in a supersonic flow is an issue encountered in several aerodynamic applications such as fuel injection in scramjet combustor, missile control, drag reduction and thrust vector control. In a recent work, an analytical model has been presented to calculate the fluidic thrust vectoring performance for a supersonic axisymmetric noz...

The aim of this paper is to present a newaeroelastic stability model taking into account the viscous effects for a supersonic nozzle flow in overexpanded regimes. This model is inspired by the Pekkari model which was developed initially for perfect fluid flow. The new model called the “Modified Pekkari Model” (MPM) considers a more realistic wall p...

Reignition phenomena occurring in a supersonic nozzle flow may present a crucial safety issue for rocket propulsion systems. These phenomena concern mainly rocket engines which use H2 gas (GH2) in the film cooling device, particularly when the nozzle operates under over expanded flow conditions at sea level or at low altitudes. Consequently, the in...

At very high altitudes, the atmosphere becomes so rarefied that it no longer behaves like a continuous medium when an object is flying in it. As illustrated in Fig.1, during re-entry, space vehicles experience rarefied flows in the high-altitude part of their trajectory.

Transverse secondary gas injection into the supersonic flow of an axisymmetric convergent–divergent nozzle is investigated to describe the effects of the fluidic thrust vectoring within the framework of a small satellite launcher. Cold-flow dry-air experiments are performed in a supersonic wind tunnel using two identical supersonic conical nozzles...

The flow in a planar overexpanded nozzle with a slope discontinuity is studied numerically by means of two- (2D) and three-dimensional (3D) Reynolds-averaged Navier–Stokes simulations and is compared to experimental results. The nozzle pressure ratios (NPR) vary from 1.6 to 10. A good agreement is found between experimental and numerical results an...

The aim of the present study is to analyze the aeroelastic stability of a supersonic nozzle in over-expanded conditions, by using an aeroelastic stability model. To reach this objective, a research software written in Fortran, has been developed for 2D and 3D nozzle configurations. The obtained results are compared and validated for the 2D and 3D c...

The transverse gas injection into the main supersonic flow of an axisymmetric convergent-divergent (C-D) propulsive nozzle is investigated for the fluidic thrust vectoring (FTV) possibilities as the segment part of the CNES “Perseus” project. Truncated ideal contour and conical C-D nozzles with different position and angle of the secondary circular...

Possibilities of the fluidic thrust vector control of a supersonic rocket nozzle have been investigated in the framework of the CNES program Perseus for small satellite launcher. Cold flow experiments are performed in the hypersonic wind tunnel EDITH on several nozzle types and configurations. The complex three dimensional flow field generated by t...

Effects of the primary and secondary inlet gases properties on the fluidically vectorized axisymmetric supersonic nozzle performances have been investigated following previous cold flow analysis in the framework of the CNES Perseus program. Sonic injection of different gases into the dry air supersonic flow of convergent-divergent axisymmetric nozz...

Transverse gas injection into a divergent section of a convergent-divergent rocket nozzle have been investigated for thrust vectoring effects as the segment part of the CNES "Perseus" program. Cold flow experiments on conical and truncated ideal nozzles have been conducted in the hypersonic windtunnel EDITH. These experiments are compared and compl...

As a part of an aerodynamics Ecole Polytechnique project, separation modes which occur in supersonic nozzles at overexpanded regimes are numerically investigated and compared with known effects. Different shock generation and reflections in different nozzle types are observed and their impact on the two main separation modes, namely Free and Restri...

An engineering-type analysis is proposed and used to investigate the performances of thrust vectoring by fluidic injection in the divergent of a supersonic axisymmetrical convergent-divergent nozzle. This method includes several approaches which consist mainly of a fluidic obstacle height evaluation and the prediction of the separation line that re...

The flowfield resulting from the transverse gas injection into the supersonic cross-flow is the problematic of many aerospace applications ranging from the scram-jet fuel injection to the reaction jets and fluidic thrust vectoring(FTV). The prominent case of FTV by the use of the secondary injection represents promisingly attractive and effective w...

During ascent in low altitudes, space launchers experience high nozzle exit pressure leading to flow separation in the divergent. Two flow separation regimes have been identified: free shock separation (FFS) and restricted shock separation (RSS) regimes [1]. The transition between these two regimes with potential asymmetry of the flow could lead to...

A numerical investigation of low-Reynolds number flows with thermal effect around the MAV airfoils using various turbulence models, including an algebraic Baldwin-Lomax model, Spalart-Allmaras one equation, and two equation (k-ω and SST-k-ω) turbulence models, is presented. First, the thermal effect on the aerodynamic efficiency is studied for flow...

A Numerical and modeling study has been accomplished to investigate the effects of a secondary injection in an axisymmetrical,convergent-divergent nozzle for fluidic thrust vectoring purpose. The annular secondary gas injection in the axisymmetrical nozzle causes complex effects (boundary layer separation, shock wave interaction,…). The present pap...

A method based on a Enter code is used to study waveriders generated from the flowfield around cones or axisymmetric power-law blunt bodies. In the cone case, the results are compared with those given by the Taylor-Maccoll system and inviscid hypersonic small-disturbance theory. This last theory shows its limits at a Mach number of 5, for cone angl...

Waveriders are supersonic or hypersonic lifting configurations which are generated from a known flowfield, preventing leakage from the high-pressure undersurface to the uppersurface, and allowing high lift-to-drag ratios. A method based on an Euler code is used to study waveriders generated from the flow field around axisymmetric bodies. In the cas...

Waveriders are supersonic or hypersonic lifting configurations which are generated by an inverse method (from a known flowfield) such that a shock wave is attached along its entire leading edge, preventing leakage from the high-pressure undersurface to the uppersurface, allowing high lift-to-drag ratios. A method based on a Euler code is used to st...

The present work contributes to define the domain of validity of two continuum approaches, based on Navier–Stokes (NS) and quasi gas-dynamic (QGD) equations, respectively. Results obtained using each method are compared with those obtained using a direct simulation Monte Carlo (DSMC) method considered as a reference. QGD equations differ from NS on...

Results of numerical and analytical investigations of inviscid steady supersonic flows in corners formed by intersecting wedges are presented. Despite the great number of papers dealing with such flows, many features of the formation of complex systems of spatially interacting shock waves in corner configurations have not been adequately studied. S...

Experimental investigations and numerical simulations have been performed to study the transition between steady regular and Mach reflections induced by flow Mach number variation. The experiments have been carried out in the supersonic wind tunnel SIGMA 4B, at the Institut Arotechnique (IAT) in St Cyr L'Ecole, France. Symmetric and asymmetric arra...

This chapter provides an overview of supersonic and hypersonic wind tunnels. Wind tunnels are used for simulating aerospace systems flight conditions in the laboratory. In principle, these facilities include a gas supplying system (source), a nozzle that transforms the gas from reservoir conditions to test conditions, the test section, and finally...

The interaction of two conical shock waves, one converging and straight and the other diverging and curvilinear, in an axisymmetric flow was investigated both experimentally and numerically. A double-loop hysteresis was discovered in the course of the experimental investigation. The double-loop hysteresis consisted of a major one, associated wi...

The reflection of asymmetric shock waves in steady flows is studied both theoretically and experimentally. While the analytical model was two-dimensional, three-dimensional edge effects influenced the experiments. In addition to regular and Mach reflection wave configurations, an inverse-Mach reflection wave configuration, which has been observe...

An experimental study of the interaction of two oblique conical shocks was carried out in the hypersonic wind tunnel of the CNRS at Meudon, France. The flow Mach number was 4.96 under steady conditions. The experiments show the classical regular and Mach interactions and reveal for the first time a new type of interaction which implies an incident...

An experimental work on the influence of downstream flow expansion process on Mach stem height has been carried out in steady hypersonic flows. The results showed clearly for the first time that the Mach stem height does not depend on the extent of expansion fan. These results contradict recent analytical findings from which a strong influence of d...

An experimental study of the interaction of two oblique conical shocks was carried out in the hypersonic wind tunnel of the CNRS at Meudon, France. The pow Mach number was 4.96 under steady conditions. The experiments show the classical regular and Mach interactions and reveal for the first time a new type of interaction which implies an incident w...

Two simultaneous numerical investigations, using different codes, were conducted. The numerical method, in the first study, was the LCPFCT algorithm, which is a one-dimensional flux corrected transport algorithm, for solving generalized continuity equations, with fourth-order phase accuracy and minimum residual diffusion. A computer code based on a...

Experimental investigations have been carried out to characterize the aerodynamic behavior of a re-entry body, based on the Apollo shape, at rarefied and hypersonic flow conditions. The present experiments have been conducted at a Mach number close to 20 and at rarefaction levels covering the near-continuum and transitional flow regimes. Measured a...

An experimental study of the interaction of two oblique shocks has been carried out in the hypersonic wind tunnel of CNRS at Meudon, France. The flow Mach number was 4.96 in a steady flow. The results show the first clear evidence of the hysteresis phenomenon in the transition from the regular to the Mach interaction wave configurations. In the dua...

An experimental study of the interaction of two oblique shocks has been carried out in the hypersonic wind tunnel of CNRS at Meudon, France. The flow Mach number was 4.96 in a steady flow. The results show the first clear evidence of the hysteresis phenomenon in the transition from the regular to the Mach interaction wave configurations. In the dua...

The reflection of shock waves over straight reflecting surfaces in steady flows was investigated experimentally using the hypersonic wind tunnel of Laboratoire d'aerothermique du CNRS at Meudon in France. The results for M(o) = 4.96 contradict the state of the art regarding the regular double left right arrow Mach reflection transition in steady fl...

The reflection of shock waves over straight reflecting surfaces in steady flows was investigated experimentally using the hypersonic wind tunnel of Laboratoire d'aerothermique du CNRS at Meudon in France. The results for M(o) = 4.96 contradict the state of the art regarding the regular double left right arrow Mach reflection transition in steady fl...

Numerical calculations based on the Navier-Stokes equations are carried out to investigate the reflection of shock waves over straight reflecting surfaces in steady flows. The results for a flow Mach number of M0=4.96 confirm the recent experimental findings of Chpoun et al. (1995) concerning the transition from regular to Mach reflection. Numerica...