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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, d...
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... In aerodynamic shape design of hypersonic vehicles, several geometric features such as vertical tail, ventral fin, and wing dihedral angle are associated with lateral-directional stability. Particularly, the wing dihedral angles typically have significant effect on lateral-directional stability by changing the spanwise distribution of aerodynamic force on wings, which has been numerically investigated by some researchers [24][25][26][27]. When studying the influence of wing dihedral angles on the stability of HCW configurations with double-lifting surfaces, a reasonable simplification of the geometric shape, especially the two wings, may be required. ...
... The analytical methodology based on oblique shock wave, onedimensional (Rayleigh) flow with heat addition in frictionless, constant-area combustion chamber and no fuel mass added, and Prandtl-Meyer expansion wave, with or without coupled to area ratio, has been applied to the conceptual scramjet design. [9][10][11][12][13][14][15][16] The basic analytical engineering approach is presented in any gas dynamics compressible flow textbook, such as Anderson. 17 Carneiro et al. 18 presented the design of a generic scramjet, with a mixed compression system and a constant area combustion chamber, using an engineering approach based on the main analytical theories of oblique shock wave, one-dimensional (Rayleigh) flow with heat addition and no fuel mass added, and Prandtl-Meyer expansion wave coupled to area ratio, which were applied to the compression, constant area combustion chamber, and expansion sections, respectively (Fig. 3). ...
Well-known analytical approaches are commonly adopted for the preliminary design of scramjet engines. In this context, the combustion process in the combustion chamber can be modeled by considering heat addition to the airflow at supersonic speed. The one-dimensional Rayleigh flow theory can be applied to estimate the behavior of thermodynamic properties and velocities when the combustion chamber has a constant cross-sectional area and no mass is added within the duct. However, the temperature and pressure predicted by using constant area combustion chambers are too high, implying the necessity of modifications in the cross-sectional area of the chamber to avoid thermal choking and excessive pressure gradients. In this case, the unidimensional Rayleigh theory does not fit anymore. This work proposes an analytical methodology to estimate the airflow thermodynamic properties and velocities for scramjet combustion chambers with cross sections of variable areas by using an iterative algorithm that employs the Rayleigh flow area ratio theory. The analytical results were compared with the two-dimensional computational fluid dynamics analysis using the Reynolds-averaged Navier–Stokes method for both inviscid and viscous flow and considering turbulence effects. The proposed analytical model to estimate the flow behavior in the scramjet combustion chamber predicted results in agreement with the physics of the problem and with the results obtained via numerical simulation. The analytical model cannot predict oscillations in the flow properties caused by the expansion waves and their reflections. Still, the behavior and intensity of the properties are well captured along the entire length of three combustion chambers with variable area. The proposed algorithm is also applied to determine the angle of the combustion chamber that allows guaranteeing a constant, or a quasi-constant, static pressure along the length of the combustion chamber, approaching better the ideal thermodynamic Brayton cycle. The proposed model is suitable for preliminary scramjet designs and can be used to solve other problems involving variable area ducts.
... Recently, radically new hypersonic waverider concepts integrating highly efficient air breathing engines are challenging the need for ultra long-haul flights [5,6,7]. Advances in propulsion technology and waverider design methodologies creating high lift-to-drag ratios are showing potential to solve the problems which have previously hampered progress. ...
Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics
and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper gives an overview of all work completed within
the HEXAFLY-INT project with respect to subsonic investigations. It covers a wide range of static and dynamic wind tunnel tests in the longitudinal and lateral-directional planes. The experimental investigations are complemented by in depth numerical computations which validate the experimental data. It was found that flow separation, non-linear vortex lift and subsequent bursting at high angles of attack govern the aircraft stability derivaties. This is due to the low aspect ratio, highly swept delta wings which are present on the vehicle, as well as sharp edges which give rise to high pressure gradients at moderate angles of attack.
... center of gravity). Both of these recommendations have been implemented in the design of the vehicle investigated in the follow-on project HEXAFLY EU-FP7, see [11,12]. These studies on the follow-on vehicle showed also showed a beneficial effect of engine on conditions on trimming and longitudinal stability of the vehicle [12], rendering the cases studied in the wind tunnel tests described here as "worst case" scenarios. ...
Aerodynamic stability is very important for high-speed aircraft configurations, where reaction times to disturbances can become quite short. Six-degree-of freedom measurements have been performed with a wind tunnel model of an air-breathing hypersonic vehicle. Mach numbers ranged between Mach 3.5 and Mach 8, utilizing two different wind tunnels. The angle of attack was varied between α = -3° and α = 3°, and the sideslip angle between β = 0° and β = 2°. Further on, the modular design of the model allowed for examining the influence of control surface deflections by canards, rudders and ailerons. Additional numerical calculations have been performed for certain test points. The tests gave insight into the aerodynamic properties of the configuration and helped to determine flight conditions with critical or unstable longitudinal and lateral stability, respectively. Further on, the influence on the aerodynamics of the vehicles that is caused by changes in the flow state at the engine intake was shown.
... Di Giorgio et al. [8] developed in-house code, with open-source software and research codes, which include modules for geometrical parametrization, automated data transfer between tools, automated execution of computational analysis codes, and design optimization methods, to provide an integrated optimization loop for shape design of an un-manned cruiser flying at hypersonic speed, corresponding to flight Mach number 8, at 30 km altitude (Earth's dense atmosphere), which this flight condition is similar to the Hypersonic Speed Civilian Transportation, under development by the European Space Agency within the Seventh Framework Program [9][10][11]. ...
A two-dimensional mixed compression scramjet inlet design is presented in this work. The design is based on the static temperature and Mach number at the combustion chamber inlet according to the conditions required to burn hydrogen spontaneously at supersonic speed. This method considers air as a calorically perfect gas, with no viscous effects, and shock on-lip and shock on-corner. To burn hydrogen spontaneously at supersonic speed the mixture temperature of the income airflow and hydrogen is obtained considering the zeroth and first Laws of Thermodynamics. The criterion of equal shock strength, based on the normal component of the airflow velocity approaching the incident oblique shock waves, is applied to obtain the compression ramps angles and the airflow corresponding thermodynamic properties. Therefore, the total pressure ratio across all incident oblique shock waves and total temperature at the compression section are constants. Although the present method can be applied to any scramjet with a mixed compression system for any number of ramps, cases with up to 5 ramps, flying at a hypersonic speed corresponding to Mach number 7 through the Earth's atmosphere at 30 km of geometric altitude are considered. Finally, the same optimization criteria are extended to analyze the inlet of a scramjet vehicle with 5 compression ramps, flying at speeds from Mach numbers 5 to 10, at an altitude of 30 km.
... Furthermore, a creative example is to remodel the design principle of characteristic profile curves to construct an airframe/inlet integrated waverider [26]. As the waverider has been extensively researched to this date, it is chosen for several practical hypersonic flight projects [27][28][29]. Nevertheless, some of the practical considerations proposed in Ref. [30] still needs close attention to further the application of the waverider in practice. ...
An ideal waverider has an infinite sharp leading edge, which causes difficulty for manufacture and aerothermal protection. Therefore, the leading edge of the waverider must be blunted. For this purpose, a parametric method for blunting the leading edge of the waverider is proposed here, which can fulfill the goals of setting a leading-edge blunt radius, achieving geometric continuity, and realizing the parametric design. First is the blunting procedure of the proposed method incorporating the construction of two-dimensional blunt curves and the integration of these curves on a three-dimensional waverider configuration. Second, waveriders blunted with different geometric continuities are built with corresponding computing grids generated. Numerical methods are then introduced and validated by the benchmark cases. Finally, results from these blunted configurations are presented and compared in terms of their geometric and flow characteristics. It shows that the proposed method has a better performance in the head region of the waverider and is thereby more suitable for the practical design.
... Recently, radically new hypersonic waverider concepts integrating highly efficient air breathing engines are challenging the need for ultra long-haul flights [5][6][7]. Advances in propulsion technology and waverider design methodologies creating high lift-to-drag ratios are showing potential to solve the problems which have previously hampered progress. To combat sonic boom issues, routes such as Brussels to Sydney would fly over the north pole and the pacific ocean to maximise high speed cruise. ...
... Similarly, yaw oscillations contain both sideslip and yaw motions. A summary of combined derivatives is given in Equations (1) to Equation (6). ...
Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. To date, low speed analyses of waverider shapes have been confined to static investigations, with limited work on longitudinal dynamics. No studies outlining the lateral-directional dynamic stability and aerodynamic derivatives has ever been published. This paper presents results for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider, which was subjected to forced oscillations in roll, yaw and side-to-side translations. This was achieved using unsteady Reynolds Averaged Navier Stokes simulations. Tests were conducted at a speed of 20 m/s, which correlates to a Reynolds number of approximately . The dynamic motion was at forced frequency of 1 Hz with angle amplitudes of 1 degree. The vehicle was analysed through an angle of attack range from -5 to 15 degrees in 5 degree increments. Results for the nominal centre of gravity location at 44.4% of the vehicle length show values for the dynamic derivatives within expected ranges, apart from the rolling moment due to yaw rate below approximately 2 degrees angle of attack. A similar finding for the dihedral derivative in static tests concluded that the low mounted wing with anhedral results in instabilities at low angles of attack. Investigations conducted at a centre of gravity location of 53.1% of the vehicle length, the aft static stability limit, also showed data within normal ranges. For these cases, the derivative magnitudes were lower, which indicates decreased damping compared to the nominal centre of gravity location. Some significant impact was seen on the roll damping derivative due to lowering the centre of gravity. This is from a combination of non-linear wing side force variance with angle of attack and the reduction of the moment arm, which resulted in less damping. The derivatives generally showed little sensitivity to changes in the oscillation frequency, with frequency rates ranging from 0.5 to 2 Hz tested. Overall, the results from this study highlighted the complex combinations of rate induced forces which contribute to the dynamic behaviour of the aircraft.
... Result comparisons carried out within the High-Speed Experimental Fly Vehicles-INTernational (HEXAFLY-INT) represent a further excellent evidence of CFD capabilities in supporting HSA design [49]. HEXAFLY-INT is an international project based on knowledge acquired from the previous European HSA projects, namely ATLLAS I and II [50,51] LAPCAT I and II [52,53], and HEXAFLY [54,55]. Fig. 13 shows the high-speed glider, namely Experimental Flight Test Vehicle (EFTV), with and without the Experimental Support Module (ESM), designed in the research programme [49]. ...
Current design requirements are shaping advanced and efficient supersonic or hypersonic aircraft concepts, capable of flying between distant parts of the globe within hours, and making affordable and safe access-to-space transportation. To achieve this challenge, reliable design tools, like Computational Fluid Dynamics, are strongly integrated in multidisciplinary design procedures. In this framework, the present paper deals with the importance and capabilities of Computational Fluid Dynamics investigations, especially those involved in vehicle aerodynamic and aerothermodynamic appraisal, to support and feed the design of high-speed aircraft. At first the Computational Fluid Dynamics support in various phases of design is addressed. Furthermore, an overall vision on methodologies used in a high speed flow computation is also given, addressing advantages and drawbacks of classical methodologies versus modern hybrid RANS methods ones. Then, a brief overview on either numerical schemes and tools, routinely adopted in an hypersonic simulation, is presented with reference to the multi-scale accuracy required by high supersonic/hypersonic flow regime. Finally, to provide a complete template for future numerical experiments, several Computational Fluid Dynamics activities, performed for a number of high-speed aircraft in different flow regimes, ranging from subsonic up to hypersonic speed, are reported and discussed. Computational methodology, domain discretization, and the support to design activity are provided for the CIRA USV1 and USV3, ESA-IXV, HEXAFLY-INT, a space launcher, and a Mars entry capsule. These examples show that Computational Fluid Dynamics can no longer be considered only an analysis tool, but it allows great advantages in all design stages, from conceptual up to detailed design level.
... This dihedral shape improves rolling stability as well as lateral/directional stability. The dihedral effect (Etkin and Reid, 1996) stability condition (C lβ <0) is put forward to prescribe a limit on the relationship between the dihedral angle and the lateral stability, so that as a consequence of disturbance of the angle of sideslip the airplane will roll away from the disturbance and sideslip will decrease (Pezzella et al., 2014). Computational fluid dynamics (CFD) aerodynamic data show that the dihedral stability of HIFiRE 6 changes with Mach number (Adamczak and Bolender, 2015;Favaloro et al., 2015). ...
When considering the practical engineering application of a waverider, the on-design and off-design aerodynamic characteristics of the design conditions, especially the lift-to-drag ratio and the stability, deserve attention. According to recently studies, the planform and rear sight shape of a waverider are closely related to the above aerodynamic performance. Thus, the planform leading-edge profile curve used to design the planform shape of a vehicle is applied to designing an osculating cone waverider. Two key parameters concerned in planform and rear sight shape, namely the plan view sweep angle of the leading edge and the dihedral angle of the underside are introduced to the waverider design process. Each parameter is inserted in the control curve equation. Especially, a parameterization scheme is put forward for the free adjustment of the sweep angle along the leading edge. Finally, three examples are generated for verification and investigation. After the verification process based on the inviscid flow field of one case, the influences of the sweep and dihedral angles on the lift-to-drag ratio and the lateral static stability are evaluated, and meaningful results are obtained. Based on these results, we can conclude that, considering the maximum lift-to-drag ratio, the sweep angle plays a role on the lift-to-drag ratio only at subsonic and trans/supersonic speed as a negligible effect is observed at hypersonic speeds, whereas the dihedral angle is seem to produce a relevant difference at hypersonic speeds. Considering the lateral static stability, the dihedral angles have more influence on the waverider than the sweep angles.
... Recently, radically new hypersonic waverider concepts integrating highly efficient air breathing engines are challenging the need for ultra long-haul flights [5][6][7]. Advances in propulsion technology and waverider design methodologies creating high lift-to-drag ratios are showing potential to solve the problems which have previously hampered progress. To combat sonic boom issues, routes such as Brussels to Sydney would fly over the north pole and the pacific ocean to maximise high speed cruise. ...
Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. To date, low speed analyses of waverider shapes is confined to static investigations, with no studies on the dynamic behaviour ever completed. This paper presents results from unsteady Reynolds Averaged Navier Stokes simulations modelling pitching and plunging forced oscillations of the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Tests were conducted at a speed of 20 m/s, which correlates to a Reynolds number of approximately 1.5×106. Pitching and plunging oscillations were at 1 Hz with an angle of attack amplitude of 1 degree. The vehicle was analysed through an angle of attack range from -5 to 15 degrees in 5 degree increments. Results for the HEXAFLY-INT aircraft at the nominal centre of gravity location, 44.4% of the vehicle length, show that the vehicle is positively damped for all cases tested. Static derivative predictions extracted from the dynamic data showed strong agreement with existing static CFD and wind tunnel results. Further dynamic investigations conducted at a centre of gravity location of 53.1% of the vehicle length, the aft static stability limit, also showed positive damping. For these cases, the derivative magnitudes were lower, which indicates decreased damping compared to the nominal centre of gravity location. The vehicle was generally not sensitive to changes in driving frequency, with oscillation rates ranging from 0.5 to 2 Hz tested. However, during plunging tests, the pitching moment derivative was seen to change by as much as 22%. This is attributed to changes in the leading edge vortices with AoA rate. The results from this study, along with previous work looking at the static aerodynamics, stability and control authority, show the feasibility of moving to the flight test phase, but the aircraft dynamic stability in the lateral-directional planes must first be investigated.
