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The HEXAFLY-INT flight vehicle is a small-scale flight demonstrator of a supersonic passenger aircraft [8,9]. In order to determine the flight angles, Mach number and altitude for this vehicle a set of pressure sensors can be used to derive this data. In the frame of this study such a system, usually called Flush Air Data Sensing system (FADS), was designed and adapted to the constrains imposed by the vehicle shape of HEXAFLY-INT. Different theoretical, analytic and numerical approaches from local inclination method to numerical simulations were used to optimize sensor positions for the flight path of HEXAFLY-INT. Afterwards these different approaches was assessed and benchmarked against each other. In the second part of this work different algorithms are investigated to determine the flight properties for simulated inputs and where analyzed in terms of accuracy and real-time performance.

Cavitation phenomena, produced when a flow is accelerated through a restriction, are of fundamental importance because of the large pressure oscillation they induce on pipelines. This paper presents an experimental investigation of various cavitation regimes produced at the exit of an orifice and its downstream propagation and attenuation. A cylindrical and a conical orifice are investigated over a range of cavitation number σ = 0.2 - 1 , keeping the ratio between saturation pressure ( P sat ) and downstream pressure ( P dw ) at two different values ξ = P sat / P dw = 0.05 , 0.3 . The range of operating conditions allows to investigate cavitation from the inception to the cloud, the developed, and the super-cavitation regime. For each configuration, the experimental analysis includes flow rate measurements, pressure signals via fast pressure transducers, and high-speed videos. The videos are analyzed using Multiscale Proper Orthogonal Decomposition (mPOD), to extract the coherent patterns that arise during the cloud cavitation and the developed cavitation regimes. The simultaneous analysis of the high-speed video in the proximity of the orifice and the time-resolved downstream pressure signal allows highlighting the effect of the cavitation intensity on the downstream evolution of these fundamental flows.

Thermal properties of cryogenic fluids can profoundly change the nature of cavitation since the fluid pressure drop is not, anymore, the only driving parameter of this phenomenon. In this research, we have conducted experiments inducing cavitation via a cylindrical orifice using Liquid Nitrogen as working fluid and exploring cavitation regimes going from bubbly cavitation to full flashing. Among others, we performed unsteady pressure measurements to derive the speed of sound during cavitation and high-speed imaging to understand the evolution of the two-phase flow along the pipe. In our analysis, we use five dimensionless numbers to describe the flow conditions upstream and downstream of the orifice, and the type of transition taking place across the orifice. In this paper, we show that the fluid initial subcooling level T sub upstream of the orifice and the superheat level Rp of the flow downstream of the orifice are two parameters essential to take into account the metastability of the fluid. Therefore, we propose a new semi-empirical model for predicting the effect of the fluid thermal properties on cavitation. Specifically, we define a parameter T which, multiplied by the saturation pressure at the inlet temperature, allows us to estimate the pressure reached at the orifice to cavitate. ispartof: International Journal Of Heat And Mass Transfer vol:164 status: Published online

The startup represents a very critical phase during the whole operational life of solid rocket motors. This paper provides a detailed study of the effects on the ignition transient of the main design parameters of solid-propellant motors. The analysis is made with the use of a quasi-one-dimensional unsteady model of solid rocket ignition transient, extensively validated, and used in the frame of the Vega program, for ignition transient predictions, reconstructions, and analyses. Two baseline solid rocket motor configurations are selected for the parametric analysis: a big booster with a three-segment propellant grain shape, similar to Ariane 5, and a small booster/solid stage with an aft-finocyl grain shape, similar to Vega solid rocket motors. The discussion of the results is particularly addressed on the possible onset of the pressure oscillations during the startup of the two solid rocket motor configurations, pointing out the design parameters that affect them in terms of occurrence and amplitude.

A relaxation method for the steady turbulent compressible Navier-Stokes equations is developed. The flow equations are fully coupled to the turbulence equations. The method is illustrated for three different k-e models on a transitional flat plate test case. The relaxation method can be used in multigridform. A multigrid method is illustrated for one turbulence model.

Hypersonic airbreathing vehicle designs are challenging due to the complexity of airframe integration and engine cycle design able to operate over a wide Mach number range. Airframe integration needs to deal with the mutual effect of the aerodynamics on the engine performance. On the other hand, the engine performance affects the vehicle design and operation. This paper first presents the followed design methodology including a description of the different approaches used for the layout of a M=8 hypersonic cruiser vehicle. The simulation of combustion process with the Dual Mode Ramjet engine is still based upon on 1D model whereas a dedicated 3D combustor CFDanalysis assesses the reliability of the 1D combustion hypotheses. An assessment of the thrust minus drag balance is carried out on a conceptual vehicle design for different Mach numbers using three-dimensional nose-to-tail CFD simulations. Here, the loosely coupled one-dimensional code for the estimation of the Dual Mode Ramjet performance is applied as well. It could be shown that for the trajectory points investigated both lateral and axial acceleration is possible.

The development of a hypersonic transportation vehicle is presently considered as the largest challenge for any aircraft manufacturer due to its intrinsic strong multidisciplinary coupling of high-speed aerodynamics, high speed propulsion, high thermal loads and high temperature resistant materials. Yet focusing here only to those aspects related to aero(thermo)dynamics, various flow topologies can yet not be correctly or accurately modelled or predicted to ascertain the vehicle design process within a certain accuracy. Presently some European funded projects such as ATLLAS [1] and LAPCAT [2] offer the opportunity to assess the limitations of each of these flow features and their combined impact on the overall vehicle performance. Moreover, though these different individual and global inaccuracies can be addressed individually on a small scale level 0(1m), the evaluation towards a real application of 0(100m) is not longer feasible due to the lack of any existing facilities able to cope with these sizes. Hence accurate extrapolation from small scale experimental and numerical/physical models towardsmuch larger scales is not straightforward. Lift, viscous forces, induced drag and thrust need to be accurately predicted throughout the design process to result into a decent estimation of sizing (planform, capture area) and fuel consumption.

This paper documents the work performed for the implementation and validation of a satellite propulsion subsystem modeling library ESPSSv2.0 (European Space Propulsion System Simulation) within the existing tool EcosimPro and using test cases relevant for space applications. EcosimPro is a physical simulation modeling tool that is an object-oriented visual simulation tool capable of solving various kinds of dynamic systems represented by writing equations and discrete events. It can be used to study both steady states and transients. The object oriented tool, with the propulsion library allows, for example, the user to draw (and to design at the same time) the propulsion system with components of that speci¦c library with tanks, lines, ori¦ces, thrusters, and tees. The user enhances the design with components from the thermal library (heaters, thermal conductance, and radiators), from the control library (analogue/digital devices), from the electric library, etc.

A conceptual study is here presented and discusscd on the possibility to transport 200 passengers over a distance of about 7000km in a nominal point-to-point mission through the Atlantic (either London-New York or London-Rio) at a cruise Mach number of 6 and an altitude abont 30km. The aim of the study is not to design a specific airplane but to explore today's state of the art technology limits to realize such kind of concept, i.e. to identify if such a mission could succeed today. Because of the challenge the mission poses, its is being optimised with the major disciplines involved by means of Multi-Disciplinary Optimisation (MDO) tools as a way to realize an optimum integrated airframe/propulsion aircraft. The environmental impact is being analysed in terms of the resulting sonic boom. No experimental data but CFD results by means of independent assessments has been generated. The study indicates that today the available technology provides with sufficient maturity to accomplish with the mission in areas like aerodynamic and thermal resistance materials but in others like sonic boom mitigation it is required a deeper insight in the physics. Finally while the present investigation clear identify that complex designs involving large amount of variables from different disciplines could be only possible via MDO/MDA strategies, today such processes still suffer on lack of robustness of the involved tools.

Rocket propellant injection lines may be subjected to extreme situations where the fuel flow conditions might cause deviation from optimal combustion requirements. Multiphase waterhammer, for example, might influence the fuel injection conditions significantly. This paper discusses the numerical models developed to simulate the fuel flow under such extreme conditions. Multi-phase waterhammer and flash atomization models are described briefly. Validation cases are presented for each model. The validation test cases for waterhammer include the analysis of a straight pipe under single and multi-phases. The multi-phase pipe was initially filled with a non condensable gas set at a certain pressure. The initially fully separated phases posed a challenge to the modeling techniques devised previously, which were dedicated to diffuse mixtures and not to sharp interfaces between the phases. Hence assumptions were made to guarantee the numerical stability and accuracy. The influence of the grid resolution and the time step size were investigated in a sensitivity study. Finally the numerical predictions are compared with the experimental measurements for different initial pressure levels. A coupled analysis of waterhammer and atomization are presented in the last section.

The present investigations focus on the mixing and combustion enhancement capabilities of a boundary layer entering a combustion chamber. Numerical investigations for both a generic configuration and a real ramp compression intake of a full-scale vehicle with a combustion chamber height of 0.3 m were performed. The flow condition is chosen according to possible conditions in a scramjet combustion chamber with 1300-kelvin static temperature, 1-bar static pressure, and a Mach number of 3. The results of this sensitivity study show that both mixing and combustion efficiency are significantly increased due to the turbulence of the incoming boundary layer, whereas the required injector spacing to reach optimum mixing and combustion has to be increased. In addition to the classical porthole injection, an injection system with hypermixing capabilities was investigated which showed comparable sensitivities.

An analysis, both theoretical and numerical of pointwise, linewise and block-wise Gauss-Seidel relaxation methods is carried out in order to study their behaviour at various flow conditions. The Fourier analysis for scalar convection-diffusion equations is extended to the coupled set of laminar Navier-Stokes equations. The analysis is in good agreement with the numerical results. Also the influence on the convergence rate of different second order implementations is considered. The combination of multigrid, line-methods and mixed discretization enables to tackle stiff problems in a cheap and robust way.

Conditionally averaged Navier-Stokes equations are derived to describe transitional flow. The averages are taken during the fraction of time the flow is laminar or turbulent, respectively. Conditional averaging leads both for the laminar and turbulent parts to a set of equations for mass, momentum and energy. The conditioned equations differ from the original Navier-Stokes equations by the presence of source terms which are functions of the intermittency factor, γ. This factor is the extra unknown and is determined by a transport equation. The evolution of γ depends mainly on the turbulence level, pressure gradient and Reynolds-number. The turbulence is described by the classical k-ϵ model. The approach is verified against several test cases, with and without pressure gradients.Copyright © 1995 by ASME

The multigrid performance of pointwise, linewise and blockwise Gauss-Seidel relaxations for compressible laminar and turbulent Navier-Stokes equations is illustrated on two low-speed test problems: a flat plate and a backward facing step. The line method is an Alternating Symmetric Line Gauss-Seidel relaxation. In the block methods, the grid is subdivided into geometric blocks of n × n points with one point overlap. With in the blocks, the solution is obtained by a direct method or with an alternating modified incomplete lower-upper decomposition. The analysis is focused on flows typical for boundary layers, stagnation and recirculation regions. These are characterized by very small Mach numbers, high Reynolds numbers and high mesh aspect ratios.

A theoretical and numerical analysis of different implicit methods in multigrid form is carried out in order to study their behaviour at various flow conditions. The Fourier analysis for scalar convection?diffusion equations is extended to the coupled set of laminar Navier?Stokes equations. For first- and second-order discretized Navier?Stokes equations, the analysis of point, line, and block methods is in good agreement with the numerical results. The influence on the convergence rate of different second-order implementations in the multigrid method is also considered. The combination of multigrid, line-methods, and mixed discretization enables to tackle stiff problems in a cheap and robust way. The comparison is further extended to Reynolds averaged Navier?Stokes equations with the low-Reynoldsk-? equations describing the turbulence. When line and block methods are used, it is advantageous not to incorporate the turbulence equations into the multigrid cycle.

© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. As a fundamental step towards the development of a civil high-speed transport concept, the European Community (EC) co-funded HEXAFLY-INT international project (with partners from Europe, Russian Federation, Brazil and Australia), has the aim to design, manufacture and test in flight an innovative gliding hypersonic vehicle, based on the configuration developed in previous EC co-funded projects LAPCAT I, II and HEXAFLY. The flight experiment is focused on a self-controlled glider configuration characterized by high aerodynamic efficiency and equipped with several breakthrough technologies on-board, in order to provide valuable aerodynamic and aero-structural flight data to validate methods and technologies used to design the hypersonic vehicle. In this framework, this paper provides a detailed overview on research efforts carried out in assessing the aerodynamic performance of the expendable Experimental Flight Test Vehicle under development in the programme. Aerodynamic results are obtained by means of a massive number of CFD simulations of increasing level of accuracy and through an experimental test campaign carried out at TsAGI in their T-116 wind tunnel facility. ispartof: Proceedings of AIAA 2017 ispartof: 21st AIAA International Space Planes and Hypersonics Technologies Conference location:Xiamen, China date:6 Mar - 9 Mar 2017 status: published

Copyright © 2017 ASME. Over the last years, innovative concepts of civil high-speed transportation vehicles were proposed. In this framework, the Hexafly-INT project intends to test in free-flight conditions an innovative gliding vehicle with several breakthrough technologies on-board. This approach will help to gradually increase the readiness level of a consistent number of technologies suitable for hypervelocity flying systems. The vehicle design, manufacturing, assembly and verification is the main driver and challenge in this project. The prime objectives of this free-flying high-speed cruise vehicle shall aim at a conceptual design demonstrating a high aerodynamic efficiency in combination with high internal volume; controlled level flight at a cruise Mach number of 7 to 8;an optimal use of advanced high-temperature materials and structures. Present research describes the aero-thermal design process of the Experimental Flight Test Vehicle, namely EFTV. The glider aeroshape design makes maximum use of databases, expertise, technologies and materials elaborated in previously European community co-funded projects LAPCAT I & II [1][2], ATLLAS I & II [3][4] and HEXAFLY [5]. The paper presents results for both CFD and Finite Element aero-thermal analysis, performed in the most critical phase of the experimental flight leading to the selection of materials for the different components and to a suitable Thermal Protection System. ispartof: PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2017, VOL 1 vol:1 ispartof: ASME International Mechanical Engineering Congress and Exposition location:Tampa, FL date:3 Nov - 9 Nov 2017 status: published

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Over the last years, innovative concepts of civil high-speed transportation vehicles were proposed. These vehicles have a strong potential to increase the cruise range efficiency at high Mach numbers, thanks to efficient propulsion units combined with high-lifting vehicle concepts. In this framework the Hexafly-INT project has the scope to test in free-flight conditions an innovative gliding vehicle with several breakthrough technologies on-board. This work describes the aero-thermal design processes of the Hexafly-INT Experimental Flight Test Vehicle, namely EFTV. ispartof: Proceedings of SPACE 2016 ispartof: SPACE 2016 Conferences and Exposition location:Long Beach, California date:13 Sep - 16 Sep 2016 status: published

This paper deals with the aerodynamic performance analysis of the expendable Experimental Flight Test Vehicle under development in the seventh framework programme, namely HEXAFLY-INT. A mission scenario, the different flight segments and events to which the payload is exposed to are described and justified. This allowed the definition of the aerothermo-mechanical loads required to conceptually design all elements on board of the vehicle. This flying test bed is a self-controlled glider configuration that shall face a hypersonic flight starting at about Mach 8, just after the separation from the experimental support module at about 50 km altitude, up to vehicle loss. During this flight, several experiments shall be carried out. The appraisal of the vehicle aerodynamic performance is needed for Flight Mechanics and Guidance, Navigation and Control analysis. In particular, hinge line moments for the EFTV’s aileron are also addressed to design the actuation line and to select the actuator device itself. The vehicle made maximum use of databases, expertise, technologies and materials elaborated in previously European community co-funded projects ATLLAS I & II, LAPCAT I & II, and HEXAFLY.

ispartof: Proceedings of AIDAA2015 ispartof: 23rd Conference of the Italian Association of Aeronautics and Astronautics (AIDAA2015) location:Torino, Italy date:17 Nov - 19 Nov 2015 status: published

This paper deals with the design trade-off activities undertaken to provide a trim-able, a statically and dynamically stable vehicle configuration able to perform a nominal experimental scramjet-propelled flight. The flight control activities and their impacts on vehicle layout and global aerodynamic performance are also addressed. In particular, different competing aeroshapes have been investigated to assess the best one camplyant with project requirements. In this framework, trade-off results in terms of: setup and/or analysis of aero-propulsive databases; design loops for the aileron (shape, span, length); design loops for the vertical tail (shape, size, toe-angle); analysis of aerodynamic performances; analysis of longitudinal trimming conditions; sensitivity to centre of gravity position of static longitudinal stability and trimming conditions; static stability analysis (for longitudinal and lateral-directional flight) in clean and flapped configuration, static margins (pitch, roll, yaw); dynamic stability analysis with a focus on roll-yaw coupling (linearized model analysis and Dutch-Roll period evaluation); characterization of hinge-moments; and preliminary selection of flight control equipment are provided and described in detail in the paper.