Lifting Body Research Articles

Investigation of the process of the stabilization of the rigid body carrier of the rotational axis of the pendulum autobalancer

The paper investigates the conditional stability of the basic steady motions of the spatial model of an isolated system, consisting of a rotating lifting body, a particle, creating its static unbalance and two identical mathematical pendulums, mounted on a longitudinal axis of the lifting body and moving in the plane of the static unbalance, the relative motion of which is hindered by the viscous resistance forces. It is found that in the case where unbalance is present and pendulums can correct it with a certain margin, there is one basic motion. In the absence of unbalance, there is a one-parameter family of basic motions. In the case of maximum unbalance, which can be corrected by pendulums, there is one basic motion, but it generates a pseudo family of basic motions. Also, it is revealed that some basic motions, if isolated, or a family or a pseudo family of basic motions is conditionally asymptotically stable. In the absence of unbalance, the presence of a single zero root of the characteristic equation does not affect the stability of a one-parameter family of basic motions and is responsible for the transition from one steady motion of a family to another. In the case of maximum unbalance, the presence of a single zero root of the characteristic equation does not affect the stability of the basic motion and is responsible for the transition from one steady motion of a pseudo family to another. Transition processes are oscillatory-damped.

Aerodynamic Boundary Element Method for Bluff Bodies with Wind Tunnel Data Correlation

Boundary Element Method (BEM) is a widely used technique for the aerodynamic analysis of lifting bodies, due to the good compromise between fidelity and computational costs. This is especially true in rotorcraft applications, where the effects of the rotor wake play a crucial role in the evaluation of aerodynamic loads, and CFD solvers suffer for dissipation problems. However, potential formulations are unable to simulate many phenomena, like stall or separation around non-aerodynamic (bluff) bodies. This limits they application to the aerodynamic analysis of complete aircraft/rotorcraft configurations, where massive separations might arise downstream of the fuselage. In this paper, several potential-flow, BEM methodologies are proposed, with the objective of overcoming these limitations, at the cost of receiving information concerning the position of separation point and/or the value of pressure in the separated-flow region. Numerical results concerning the assessment of the proposed BEM techniques are presented: these consist in comparisons with data available in the literature for simple-geometry bodies, and with measurements obtained by experimental tests performed in a semi-open wind tunnel facility on a light-weight helicopter fuselage.

External turbulence-induced axial flow and instability in a vortex

External turbulence-induced axial flow in an incompressible, normal-mode stable Lamb–Oseen (two-dimensional) vortex column is studied via direct numerical simulations of the Navier–Stokes equations. Azimuthally oriented vorticity filaments, formed from external turbulence, advect radially towards or away from the vortex axis (depending on the filament’s swirl direction), resulting in a net induced axial flow in the vortex core; axial flow increases with increasing vortex Reynolds number ($Re=$ vortex circulation/viscosity). This contrasts the viscous mechanism for axial flow generation downstream of a lifting body, wherein an axial pressure gradient is produced by viscous diffusion of the swirl (Batchelor, J. Fluid Mech., vol. 20, 1964, pp. 645–658). Analysis of the self-induced motion of an arbitrarily curved external filament shows that any non-axisymmetric filament undergoes radial advection. We then studied the evolution of a vortex column starting with an imposed optimal transient growth perturbation. For a range of Re values, axial flow develops and initially grows as (time)$^{5/2}$ before decreasing after two turnover times; for $Re=10\,000$ – the highest computationally achievable – axial flow at late times becomes sufficiently strong to induce vortex instability. Contrary to a prior claim of a parent–offspring mechanism at the outer edge of the core, vorticity tilting within the core by axial flow is the underlying mechanism producing energy growth. Thus, external perturbations in practical flows (at $Re\sim 10^{7}$) produce destabilizing axial flow, possibly leading to the sought-after vortex breakup.

The design and realisation of the IXV Mission Analysis and Flight Mechanics

The Intermediate eXperimental Vehicle (IXV) is a suborbital re-entry demonstrator successfully launched in February 2015 focusing on the in-flight demonstration of a lifting body system with active aerodynamic control surfaces. This paper presents an overview of the Mission Analysis and Flight Mechanics of the IXV vehicle, which comprises computation of the End-to-End (launch to splashdown) design trajectories, characterisation of the Entry Corridor, assessment of the Mission Performances through Monte Carlo campaigns, contribution to the aerodynamic database, analysis of the Visibility and link budget from Ground Stations and GPS, support to safety analyses (off nominal footprints), specification of the Centre of Gravity box, selection of the Angle of Attack trim line to be flown and characterisation of the Flying Qualities performances. An initial analysis and comparison with the raw flight data obtained during the flight will be discussed and first lessons learned derived.

衝撃風洞によるリフティングボディ形状模型の空力特性評価

衝撃風洞によるリフティングボディ形状模型の空力特性評価

Совершенствование системы на пассивной безопасности легкового автомобиля при фронтальном столкновении с грузовым транспортным средством

At emergency brake application before collision a car clearance decreases considerably, a car front side comes lower and actually does not participate in blow energy absorption. A car “dives under” a lorry and al-most all blow energy falls to the roof and windshield posts which do not figure on the perception of such a load that often results in fatal consequences.
 To reduce weight of consequences after such a collision there was developed a design for a passive car safety. The device consists of a ring pneumatic cylinder which is situated round a front shock strut next the upper bearing of a shock absorber and connected with a squib. It is intended for lifting and car body fixation along the height before a collision with a lorry. There are two such devices installed in a motor car, with one for each front wheel. It is not difficult to make this device there is no need in essential changes in the car design. It can be installed in any car with front posts of the type «macferson».
 The offered device is integrated in the general system of a car passive safety and at unavoidable head collision with a lorry is activated by means of a squib explosion.
 Key words: life-saving device, car, head-on collision, lorry.

Experimental analysis of the oscillations of a mechanical system with self-synchronized inertial vibration exciters

This article describes the results of experimental studies of oscillations in a classical singlemass oscillation system on a spring suspension with two unbalanced mass vibration generators in a wide range of excitation frequencies. The testing technique is described, and the results are analyzed in detail. It is shown that there is an effect of self-oscillatory adaptive self-synchronization of imbalances for changes in the oscillation modes of the lifting body, depending on the excitation frequency in the mechanical system.

Experimental research on a hypersonic configuration with blunt forebody edges

A design method, for hypersonic forebody configuration with blunt edges, was developed by lift body and waverider. Experimental study was conducted. It was showed that the difference of pressure coefficient, at centre-line and side-line on forebody precompression surface, was between 2.5% and 16.7% within the Mach number 5 to 7 and attack angle 0 to 12. These differences were slightly bigger than those of non-blunt-edges forebody. However, experimental data also show that the present configuration can achieve the closed shockwave, and can also realize the automatic overflow of boundary layer on forebody pre-compression surface. It is also observed that the present forebody gets a good aerodynamic performance at high Mach numbers. But with increasing attack angle, the advantage was weakened gradually. And, at the degree of side-slip exceeding 8, the side-line pressure is higher than that of center-line, which indicates that the forebody boundary layer does not achiev automatically overflowing to side surface.

Performance enhancement of a Lorentz force velocimeter using a buoyancy-compensated magnet system

Lorentz force velocimetry (LFV) is a highly feasible method for measuring flow rate in a pipe or a duct. This method has been established for liquid metal flows but also for electrolytes such as saltwater. A decrease in electrical conductivity of the medium causes a decrease of the Lorentz force which needs to be resolved, affecting the accuracy of the measurement. We use an electrical force compensation (EFC) balance for the determination of the tiny force signals in a test channel filled with electrolyte solution. It is used in a 90°-rotated orientation with a magnet system hanging vertically on its load bar. The thin coupling elements of its parallel guiding system limit the mass of the magnets to 1 kg. To overcome this restriction, which limits the magnetic flux density and hence the Lorentz forces, a weight force compensation mechanism is developed. Therefore, different methods such as air bearing are conceivable, but for the elimination of additional horizontal force components which would disturb the force signal, only compensation by lift force provided by buoyancy is reasonable. We present a swimming body setup that will allow larger magnet systems than before, because a large amount of the weight force will be compensated by this lift force. Thus the implementation of this concept has to be made with respect to hydrodynamical and mechanical stability. This is necessary to avoid overturning of the swimming body setup and to prevent inelastic deformation. Additionally, the issue will be presented and discussed whether thermal convection around the lifting body diminishes the signal-to-noise ratio (SNR) significantly or not.

Pitch Control Design for Tandem Lifting Body Catamaran by Aft Lifting Body Actuation

We design an adaptive controller to stabilize the pitch of the tandem lifting body catamaran with actuation of the aft lifting body for the case where the hydrodynamic and other parameters are not known a priori. We consider two scenarios: 1) we assume the pitch and the pitch rate to be available for feedback and 2) we use only the pitch rate and the pitch acceleration in the adaptive control design. Our designs are based on three steps: 1) parametrization of the unknown sinusoidal wave disturbance as the output of a known feedback system with an unknown output vector that depends on unknown disturbance parameters; 2) design of an adaptive disturbance observer for the wave disturbance; and 3) design of an adaptive controller. We demonstrate the effect of our control designs in simulations, using a time-domain seakeeping code, named AEGIR.

Preliminary Integrated Design of Hypersonic Vehicle Configurations Including Inward-Turning Inlets

AbstractA design method employed for preliminary integration of a hypersonic vehicle airframe configuration with its propulsion flow path is described. This method is primarily based on the integration of the variable cross section inward-turning inlet and the airframe. Three typical configurations include lifting body, sim-waverider, and semi-axisymmetric cone. Rectangular-to-circular, erose-to-circular, and sector-to-circular shape transition Busemann inlets are designed to integrate these three vehicle bodies, respectively. The results of numerical simulations show that the aerodynamic performance of these configurations, coupled with the propulsion flow path, inherits the characteristics of their original airframe shapes, such as the high lift/drag ratio of sim-waverider and the low-drag performance of semi-axisymmetric cone configuration. The computed results also demonstrate that the inward-turning inlets integrate smoothly with their respective vehicle airframes and that the design method is viable.

Aerodynamic performance analysis of a non-planar C-wing using CFD

The aircraft is the second fastest means of transport. One of the most important necessities of an aircraft is the air flow over the wings to produce lift. Wing is a structure attached to the fuselage of the aircraft. Lift is an aerodynamic force which is counteracted by drag. In air transport, the cost of operation per each person/unit is higher than in the other transport because of lower passenger/load carrying capacity. One of the best ways to reduce the cost among such factors is increasing the capacity of the airplane. And this can be increased by weight carrying or lifting capacity of the airplane. Lift is controlled by the free stream flow over the wing body (main lifting body) and speed of the flow that produce drag. Most aircraft are monoplanes having one-wing structure for providing lift. Biplanes (two wings) or triplanes (three wings) were popular in the past. Due to inefficiency of the biplane and triplane (used in past days), monoplanes are in present use. To increase the efficiency of the monoplane configuration, ‘C-wing’ configuration is presented in this article. The aim is to prove, at all angles of attack, the C-wing will produce higher (L/D) ratio than straight wing for the same wetted surface area. The work undertaken here is to study the aerodynamic performance of a non-planar C-wing. This project concentrates on comparison between straight wing and C-wing with regard to characteristics like drag, stall.

Aerodynamic forcing characteristics of dry cable galloping at critical Reynolds numbers

This article attempts to highlight characteristics of the aerodynamic forcing on a rigid circular cylinder experiencing dry galloping vibrations. Observations from a series of wind tunnel tests are studied comparatively with the literature on rain–wind cable vibrations and on flow past inclined lifting bodies such as missiles, for drawing similarities. Unsteadiness and spatial variation of the flow, both previously undermined, are significant during the large cylinder motions recorded. Thus, they are here suspected to play a role in triggering unstable behaviour. Instabilities were restricted to specific ranges of cable-wind angles and Reynolds numbers. The transitional features identified refute the view of simple bursting separation bubbles that rhythmically produce lift and suggest that there is a multitude of paths for energetically feeding dry galloping. Finally explanations are provided and a mechanism incorporating unstable features is proposed for future modelling.

Two Dimensional Motion of an Oscillating Airfoil in a Fluctuating on Coming Stream at Supersonic Speed

The aerodynamic characteristics of a lifting body are studied for the case of a non uniform oncoming stream at supersonic speed past a thin oscillating airfoil at a small angle of attack. The two motions are assumed independent of each other and the coupled motion is analyzed using the theory of small disturbances. Analytic solution of the linearized problem is then obtained by applying Laplace transformation to it.

Hypersonic lifting body aerodynamic shape optimization based on the multiobjective evolutionary algorithm based on decomposition

In this work, a volume and longitudinal stability-constrained multiobjective aerodynamic shape optimization is conducted. The aerodynamic shapes of lifting bodies are parameterized by using class function/shape function transformation parameterization method for maximum design flexibility. Hypersonic aerodynamic objectives and constraints are analyzed by solving the Reynolds-averaged Navier–Stokes equations in conjunction with a two-equation turbulence model. The Kriging technique is adopted to construct surrogate models aiming at reducing the computational cost. A two-stage method of infill sampling combined with multiobjective optimization is proposed to improve the performance of the surrogate models. Multiobjective evolutionary algorithm based on decomposition (MOEA/D) combined with penalty function method is employed to handle the multiobjective optimization problem with nonlinear constraints. The optimization results reveal that the two-stage method based on surrogates can reduce the computational cost significantly, and the accuracy of the surrogates around the Pareto front is sufficient. The two objectives are competing such that a set of Pareto optimal solutions are obtained, which are the best tradeoffs among the objectives. The unconstrained multiobjective optimization problem is also investigated with MOEA/D and nondominated sorting genetic algorithm II (NSGA-II) respectively to make a further comparison. The results show that the Pareto sets based on MOEA/D are more excellent and distribute more evenly than that obtained by NSGA-II. The computational efficiency of MOEA/D is about six times faster than that of NSGA-II. Lastly, aerodynamic characters of typical shape of Pareto front are analyzed under different flight conditions, and the results reveal favorable robustness of this shape.

Ecological aspect of launch vehicles development by criterion of minimal cost

One of the topical problems in modern aerospace engineering is accordance between ecological requirements and performance of the vehicle. On the other hand, problem of economical efficiency leads to change of the main criterion of designing to the minimization of costs (instead of maximal performance). According to modern trends of “low-cost” vehicles, different concepts of the future cost-effective launch vehicles are considered. It is necessary to validate these concepts according to requirements of ecological safety for the purpose of detection of the dominant launch vehicle configuration. Typical configurations of the future 'low-cost' launch vehicle are presented by 6 conceptual groups (Koelle, 2001). Conceptual group 1 (CG1) is presented by the Ballistic “Single stage to orbit” (SSTO) reusable vehicle. All vehicles which use classical rocketry scheme of the propulsion trajectory are called “Ballistic” i.e. the ballistic vehicle is lifted to orbit under the impact of rocket engines thrust. CG1-vehicle is able to reach the low earth orbit (LEO) without stage separation reducing the number of required rocket engines. Technological feasibility of SSTO concepts is proven by numerous studies (Koelle, 2001). CG2 representatives are ballistic “Two stages to orbit” (TSTO) reusable vehicles. The difference between CG1 and CG2 consists in application of vacuum rocket engines in the second stage and, consequently, stage separation. CG2 are the most mass-effective vehicles. CG3 is presented by the winged SSTO vehicles with rocket propulsion by “Lifting body” aerodynamic scheme. Ascensional force is provided by the aerodynamic shape of the vehicle’s structure at high speeds. Winged TSTO vehicles with rocket propulsion and parallel or tandem staging form the CG4. The winged configuration provides wide landing capability for both stages. CG5 is presented by winged TSTO vehicles with airbreathing propulsion in the first stage and rocket-propelled second stage. Airbreathing jet engines provide high reusability ratio comparing with other concepts as well as the widest landing capability. Aerospace Plane with scramjet-rocket propulsion forms CG6. The vehicle is able to reach near-cosmic speed in rarefied layers of the atmosphere and then accelerate with rocket engines. The most ecologically important resemblance of represented concepts is reusability. This reduces space debris formation (due to lack of waste hardware). Reusable launch vehicles can also be used to return the spent satellites. Structural differences between the concepts form 3 criterions of comparison by ecological impact: 1) propellant toxicity; 2) safety of surface facilities (vehicle damage inside the atmosphere); 3) probability of space debris formation (vehicle damage outside the atmosphere). Comparison of the concepts by these criterions allows substantiating the most ecologically acceptable direction of research. Results of the comparison demonstrate that the most ecologically acceptable low-cost launch vehicle configuration is: Ballistic SSTO or TSTO reusable launch vehicle with “LOX+LH2” propellant. The results can be explained by following way: combustion products of the propellant “liquid oxygen + liquid hydrogen” are absolutely safe for environment. It also provides maximal performance of rocket engine (due to the highest specific impulse). Ballistic ascent scheme allows using relatively simple technologies and provides high reliability level. In combination with minimal time of atmospheric flight this provides high level of safety for surface facilities. These results may be used for substantiation of dominant research direction.

Inviscid Circulatory-Pressure Field Derived from the Incompressible Navier–Stokes Equations

The static-pressure field in the steady and incompressible Navier–Stokes momentum equation is decomposed into circulatory (inviscid) and dissipative (viscous) partial-pressure fields. It is shown analytically that the circulatory-pressure integral over the surface of a lifting body of thickness recovers the lift generating Kutta–Joukowski theorem in the far field, and results in Maskell’s formula for the vortex-induced drag plus an additional pressure-loss term that tends to zero for an infinitely thin wake. A Poisson equation for the circulatory-pressure field is implemented as a transport equation into the FLUENT 13 solver. Numerical examples include a circular cylinder at , the S809 airfoil at , and the ONERA M6 wing at . It is shown that the circulatory-pressure field does indeed behave as an inviscid pressure field of a fully viscous solution, and provides insight into the nature of pressure drag and its contributions to local form and vortex-induced drag.

Feasibility of Guided Entry for a Crewed Lifting Body Without Angle-of-Attack Control

The feasibility of flying a crewed lifting body, such as the HL-20, during entry from low Earth orbit without the steady-state body flap deflections required for angle-of-attack control was evaluated. This entry strategy mitigates the severity of the aerothermal environment on the vehicle’s body flaps and reserves control power for transient steering maneuvers. A real-time numeric predictor–corrector entry guidance algorithm was developed to accommodate the range of vehicle trim angle-of-attack profiles possible in the absence of angle-of-attack control. Results show that it is feasible to steer the vehicle from low Earth orbit to a desired target with real-time guidance while satisfying a reasonable suite of trajectory constraints, including limits on peak heat rate, peak sensed deceleration, and integrated heat load. Uncertainty analyses confirm this result and show that the vehicle maintains significant performance robustness to expected day-of-flight uncertainties. Additionally, parametric scans over mission design parameters of interest indicate that a high level of flexibility is available for the low-Earth-orbit return mission. Together, these results indicate that the proposed entry strategy is feasible: Crewed lifting bodies may be effectively flown without steady-state body flap deflections.

2船並走時の舵と船体の流体力学的干渉に及ぼす浅水影響

Ship is under way side by side in close proximity to the other ship in the case of meeting/overtaking in a narrow waterway or ship to ship transfer operation. Since it is required to understand the hydrodynamic force characteristics for safe navigation, a lot of studies on them have been done so far. However there have been few studies on the hull to rudder interactions between two ships alongside except for the previous study by authors. This study is a continuous work and the shallow water effect on them is discussed. Captive model tests were conducted in shallow water, i.e. the depth/draft ratio 1.2 and 1.5, with variations in the lateral clearance between hulls, hull drift angle and rudder angle. The authors found, for example, when a ship steered, the lift interaction force acted not only on the self-ship but also on the other ship moving side by side in close proximity. It turned in the opposite direction and its acting point was also shifted with decrease of water depth. The experimental results were compared with the numerical analysis based on a nonlinear lifting body theory and it was able to capture the tendency of the shallow water effect on those hydrodynamic force characteristics.

Cost Analysis of a Hybrid Airship Vehicle for Cargo Delivery

Cargo transportation is a very serious business and cost of delivering a pound of cargo for a mile keeps rising every day. Today, there are two options exist; fast but expensive aircraft and slow but inexpensive sea freight. A Hybrid Air Vehicle (HAV) was designed to solve this problem by combining the aerodynamic lift advantages from a lifting body shape and the effectiveness of lighter than air from buoyancy. These combined lifting capabilities gave the HAV enough lifting force to carry additional cargo compared to aircraft and its propeller engine gave it the ability to travel relatively fast compared to sea freight. The cost of transporting a pound of cargo a mile using proposed HAV is $ 0.00022/lb-mile as compared to $0.00043/lb-mile for C-5 Galaxy which translates to nearly 48% saving. The HAV cost 1000% more than sea freight but it is 647% faster.