Effects Of Aerodynamic Heating Research Articles

A real-time infrared radiation imaging simulation method of aircraft skin with aerodynamic heating effect

Real-time infrared radiation simulation technology can provide effective support for rapid design and evaluation of a system which integrates infrared imaging technology. Considering the aerodynamic heating effect, this paper presents a real-time infrared radiation characteristic simulation method of aircraft skin based on the panel element method, which can help to assess the infrared radiation impacts of different environment factors and materials. A 3-D model of an aircraft was established and its surface was divided into different parts and panel element meshes to attach material properties. For each mesh, its heat exchange equation is solved so as to obtain the whole skin’s temperature and infrared radiation distribution. The simulation results reveal the influence of different factors on the skin surface radiation, including environmental radiation, aerodynamic heating and material properties. And the credibility and efficiency of the proposed aerodynamic heating simulation method were confirmed by comparing to the CFD simulation results.

Performances of a small hypersonic airplane (HyPlane)

In the present work a preliminary performance study regarding a small hypersonic airplane named HyPlane is presented. It is designed for point-to-point medium range hypersonic trip, within the “urgent business travel” market segment. The vehicle is also consistent with long duration suborbital space tourism missions, in the frame of the Space Renaissance (SR) Italia Space Tourism Program. The design of such a hypersonic airplane is based on the concept of integrating available technologies developed for aeronautical and space atmospheric re-entry systems.The vehicle, characterized by high aerodynamic efficiency and low wing loading and powered by Turbine Based Combined Cycle (TBCC) engines plus a throtteable Rocket, is able to produce a reduced sonic boom and to perform Horizontal Takeoff and Horizontal Landing (HTHL) on runways.Aerodynamic and propulsive performances for the different flight regimes encountered during the missions are studied. Aerodynamic heating effects are analyzed, in order to identify suitable structures and materials design to sustain the hypersonic flight conditions. Different flight paths are also investigated, including hypersonic cruise and suborbital parabolic trajectories, which provide Space tourists with the opportunity of long duration missions, offering short and repeated periods of low-gravity, in the high stratosphere where a large view of the Earth is ensured.

Nonlinear Response of a Compressible Boundary Layer to Free-stream Vortical Disturbances

The nonlinear response of a compressible boundary layer to unsteady free-stream vortical fluctuations of the convected-gust type is investigated. The amplitude of the disturbances is strong enough for nonlinear interactions to be induced within the boundary layer. Attention is focused on the induced low-frequency streamwise-stretched components of the boundary-layer disturbances, known as streaks or Klebanoff modes, which may become unstable and break down to fully developed turbulence. The streaks are described using the mathematical framework of the so-called boundary-region equations, i.e. the asymptotic limit of the Navier-Stokes equations for low-frequency disturbance, developed by Leib et al.1 and extended by Ricco & Wu 2 and Ricco et al.3 to linear perturbations in compressible boundary layers, and nonlinear disturbances in incompressible boundary layers, respectively. In the present work, compressibility is taken into account through aerodynamic heating effects due to the mean-flow velocity being comparable with the speed of sound. Both velocity and thermal (temperature) streaks are generated as well as are a new mean flow and fluctuations of higher frequencies. Nonlinearity attenuates the fluctuations of the streamwise velocity and a similar stabilizing effect is observed on the temperature.This represents the preliminary study which is necessary to carry out the secondary instability analysis on the new unsteady compressible three-dimensional flow generated by the nonlinear interactions.

Dynamic interaction of heat transfer, air flow and disc vibration of disc drives — Theoretical development and numerical analysis

Steady state air flow, heat transfer and thermoelastic dynamics in the multi-field coupling system of a rotating flexible disc in an enclosure filled with air are investigated within a large speed range. The system represents rotating discs in hard disc drives and optical disc drives. With Navier–Stokes and continuity equations and an improved penalty finite element method, air velocities and pressure induced by disc rotation in the enclosure are obtained. Temperature distribution of the rotating disc, driving shaft, enclosure and air flow is determined under the external heat sources from the shaft-driving motor and the circuit board inside the enclosure, the internal heat source from aerodynamic heating due to viscous dissipation of fluid, the heat convection in air flow, and the free convection heat loss at the enclosure׳s outside surfaces. Natural frequencies of the rotating disc are solved under the stresses induced by the disc temperature distribution and centrifugal force. Effects of heat convection and aerodynamic heating induced by disc rotation on system heat balance and dynamic characteristics of the rotating disc are investigated. The method presented is helpful to design of hard/optical disc drives and many other applications that involve rotating discs in fluids and with heat transfer.

Uncertainty Propagation in Integrated Airframe–Propulsion System Analysis for Hypersonic Vehicles

Air-breathing hypersonic vehicles are based on an airframe-integrated scramjet engine. The elongated forebody that serves as the inlet of the engine is subject to harsh aerothermodynamic loading, which causes it to deform. Unpredicted deformations may produce unstart, combustor chocking, or structural failure due to increased loads. An uncertainty quantification framework is used to propagate the effects of aerothermoelastic deformations on the performance of the scramjet engine. A loosely coupled airframe-integrated scramjet engine is considered. The aerothermoelastic deformations calculated for an assumed trajectory and angle of attack are transferred to a scramjet engine analysis. Uncertainty associated with deformation prediction is propagated through the engine performance analysis. The effects of aerodynamic heating and aerothermoelastic deformations at the cowl of the inlet are the most significant. The cowl deformation is the main contributor to the sensitivity of the propulsion system performance to aerothermoelastic effects.

Transient thermal and pressurization performance of LO2 tank during helium pressurization combined with outside aerodynamic heating

A computational fluid dynamic (CFD) model, which can simultaneously account for the heat exchanges inside the tank and outside aerodynamic heating, is constructed to investigate the transient thermal and pressurization performance of cryogenic tank during discharge. Besides the fluid and tank wall regions, the foam region is also considered as the computational domain. Reference enthalpy method is used to account for the outside aerodynamic heating effect. The predictive ability of the CFD model is evaluated on the basis of the comparisons between its results and experimental data and a good agreement is obtained. Then the model is used to predict a pressurized discharge event, and the thermal and pressurization behaviors are obtained and analyzed. The results show that outside aerodynamic heating cannot penetrate the foam layer to facilitate the pressurization performance. Conversely, a certain proportion of energy might be transferred from heated tank wall to foam layer, which exert a negative effect on the pressurization behaviors. The aerodynamic heating effect may not be accounted for in the CFD simulation of a foam-insulated tank, if the thermal performance at outer surface of the tank is not particularly concerned. Generally, this paper supplies an effective way to predict pressurization performance and expresses valid results of the thermal performance inside and outside the cryogenic tank during discharge. It is also stated that the CFD model has a better accuracy in predicting pressurization characteristics.

AEROTHERMOELASTIC MODEL OF PANEL FLUTTER WITH CONSIDERATION OF THE HISTORY EFFECTS OF AERODYNAMIC HEATING

An improved aerothermoelastic flutter model of an infinitely long isotropic panel is proposed to investigate the complex dynamic behaviors of panel structures in supersonic flow. Considering the history effects of aerodynamic heating, a new model suitable for numerical computation of the temperature distribution in the panel is presented and proved mathematically. Then, the internal force and moment in the panel induced by thermal stress are accurately introduced into the existing panel flutter model. Finally, some numerical analyses based on the Galerkin procedure are presented, in combination with the presented aerothermoelastic model which is based on von Karman large deflection plate theory. From the numerical results, it is found that the effects of the aerodynamic heating and its history are significant and complicated, since they can induce, intensify, or change the oscillation behaviors of the panel. Furthermore, a rich variety of nonlinear dynamic behaviors, such as instabilities and chaos in the panel flutter model, are captured and analyzed, by bifurcation analysis and the maximum Lyapunov exponent in nonlinear dynamics. As a conclusion, it can be drawn that the model presented could be used to study the aerothermoelastic dynamics accurately and feasibly.

AEROTHERMOELASTIC RESPONSE OF HYPERSONIC 2-D LIFTING SURFACE

The expressions of unsteady gust loads are derived based on the piston theory in this paper. The aerothermoelastic response of hypersonic two degree-of-freedom airfoil is analyzed. The calculation of the unsteady aerodynamic lift and moment are given based on third-order piston theory. Also considered is the loss of torsional stiffness that may be incurred by lifting surface subject to axial stresses induced by aerodynamic heating. The aerodynamic heating effects are estimated based on the adiabatic wall temperature due to high speed airstreams. The effect of horizontal gust loads on aeroelastic response system is compared with vertical gust loads. Then the relationship between the pitching displacement amplitude and the gust velocity is analyzed. Numerical results show that horizontal gust has little effect on the stabilization system, while the vertical gust has a significant effect on the aeroelastic system. The acceleration of airfoil which is generated due to the vertical gust can cause the system to become vibrating for a long time. The results also show that pitching displacement amplitude of the aeroelastic response is in the direct proportion to the gust velocity, the proportion is about 3.8 × 10-4.

Comparison of liquid impingement results from whirling arm and water-jet rain erosion test facilities

► Correlation of whirling arm and water-jet erosion test rigs. ► Use of roughness measurements as a method to compare high velocity liquid impact tests. ► Development of a laboratory scale whirling arm rain erosion test rig. ► Inspection of eroded surfaces by scanning electron, confocal and optical microscopy. A laboratory-scale Whirling Arm Rain Erosion test Rig (WARER) has been designed, developed and commissioned at the University of Limerick. The facility is capable of impact speeds of 178 ms −1 and a rainfall rate of 25.4 mm h −1 . Circular samples of 27 mm diameter (nominal) and a maximum thickness of 2 mm can be accommodated. The facility was developed to test the resistance of leading edge aircraft materials to the repeated impact of rain droplets in flight. A challenging feature of the design was to enclose the whirling arm within a chamber so that it could be operated in an open-plan laboratory. A design problem that arose was the effect of aerodynamic heating of the air within the chamber. This led to a warming of the water and consequently a change in the droplet formation, which in turn caused problems relating to the repeatability of the tests. A cooling system was thus incorporated to keep the temperature of the water droplets below the established threshold of 20 °C. Calibration testing has been undertaken by conducting back-on-back testing of samples with a previously developed water-jet facility at EADS IW, Munich. This Pulsating Jet Erosion Test rig (PJET) is capable of 225 ms −1 droplet speed. Multiple impacts are produced on the sample at numerous locations, each location having an increased number of impacts. The impact frequency is equivalent of 25 mm h −1 rain fall. Clad aluminium alloy (AA2024-T3) was used with the soft AA1230 clad layer being removed during testing. Post impact evaluations were carried out using Confocal Laser Scanning Microscopy (CLSM) and surface roughness measurements. A cumulative erosion-time curve was produced from the WARER samples.

Non-linear aerothermoelastic modeling and behavior of a double-wedge lifting surface

The design of the re-entry space vehicles and high-speed aircraft structures requires special attention to the non-linear thermoelastic and aerodynamic instabilities. The thermal effects are important since temperature environment influences significantly the static and dynamic behaviors of flight structures in supersonic/hypersonic regimes. The dynamic behavior of a double-wedge lifting surface with combined freeplay and cubic stiffening structural nonlinearities in both plunging and pitching degrees-of-freedom (DOF) operating in supersonic/hypersonic flight speed regimes has been analyzed. In addition a third order piston theory aerodynamics (PTA) is used to evaluate the non-linear unsteady aerodynamic loads applied to the wing section. Loss of torsional stiffness that may be incurred by lifting surfaces subjected to axial stresses induced by aerodynamic heating is also considered. The aerodynamic heating effect is estimated based on the adiabatic wall temperature due to high speed airstreams. It is demonstrated that serious losses of torsional stiffness may occur in such lifting surfaces; the influence of various parameters such as flight condition, thickness ratio, freeplays and pitching stiffness nonlinearity are discussed.

Comparison of Response Surface and Kriging Surrogates in Aerodynamic Design Optimization of Hypersonic Spiked Blunt Bodies

The high fidelity numerical simulation codes used in aerodynamic design and optimization applications show a number of drawbacks. Of these, the high computational cost, memory and time demands associated with complicated designs. Metamodels or surrogates provide a much cheaper alternative for these codes. The use of spikes in the design of hypersonic vehicles yields a considerable reduction in drag and aerodynamic heating effects. In this work, surrogates are used in the context of design optimization of a spiked blunt body in hypersonic flow conditions. Four different surrogate models including quadratic response surface and kriging were constructed based on the values of drag and heating responses. The evolutionary genetic algorithm is applied to find the optimum design based on each of the surrogates. The structure of the various models was investigated and the main differences were addressed. For the cases investigated in this work, kriging surrogate based on exponential correlation produced a relatively better prediction of new points in thedesign space and, consequently, better optimized design.

Active Aerothermoelastic Control of Hypersonic Double-wedge Lifting Surface

Designing re-entry space vehicles and high-speed aircraft requires special attention to the nonlinear thermoelastic and aerodynamic instability of their structural components. The thermal effects are important since temperature environment brings dramatic influences on the static and dynamic behaviors of flight structures in supersonic/hypersonic regimes and is likely to cause instability, catastrophic failure and oscillations resulting in structural failure due to fatigue. In order to understand the dynamic behaviors of these “hot” structures, a double-wedge lifting surface with combining freeplay and cubic structural nonlinearities in both plunging and pitching degrees-of-freedom operating in supersonic/hypersonic flight speed regimes has been analyzed. A third order piston theory aerodynamic is used to estimate the applied nonlinear unsteady aerodynamic loads. Also considered is the loss of torsional stiffness that may be incurred by lifting surfaces subject to axial stresses induced by aerodynamic heating. The aerodynamic heating effects are estimated based on the adiabatic wall temperature due to high speed airstreams. As a recently emerging technology, the active aerothermoelastic control is aimed at providing solutions to a large number of problems involving the aeronautical/aerospace flight vehicle structures. To prevent such damaging phenomena from occurring, an application of linear and nonlinear active control methods on both flutter boundary and post-flutter behavior has been fulfilled. In this paper, modeling issues as well as numerical simulation have been presented and pertinent conclusions outlined. It is evidenced that a serious loss of torsional stiffness may induce the dynamic instability; however active control can be used to expand the flutter boundary and convert unstable limit cycle oscillations (LCO) into the stable LCO and/or to shift the transition between these two states toward higher flight Mach numbers.

Sulzer Corp, Switzerland

A laboratory-scale Whirling Arm Rain Erosion test Rig (WARER) has been designed, developed and commissioned at the University of Limerick. The facility is capable of impact speeds of 178 ms−1 and a rainfall rate of 25.4 mm h−1. Circular samples of 27 mm diameter (nominal) and a maximum thickness of 2 mm can be accommodated. The facility was developed to test the resistance of leading edge aircraft materials to the repeated impact of rain droplets in flight. A challenging feature of the design was to enclose the whirling arm within a chamber so that it could be operated in an open-plan laboratory. A design problem that arose was the effect of aerodynamic heating of the air within the chamber. This led to a warming of the water and consequently a change in the droplet formation, which in turn caused problems relating to the repeatability of the tests. A cooling system was thus incorporated to keep the temperature of the water droplets below the established threshold of 20 °C. Calibration testing has been undertaken by conducting back-on-back testing of samples with a previously developed water-jet facility at EADS IW, Munich. This Pulsating Jet Erosion Test rig (PJET) is capable of 225 ms−1 droplet speed. Multiple impacts are produced on the sample at numerous locations, each location having an increased number of impacts. The impact frequency is equivalent of 25 mm h−1 rain fall. Clad aluminium alloy (AA2024-T3) was used with the soft AA1230 clad layer being removed during testing. Post impact evaluations were carried out using Confocal Laser Scanning Microscopy (CLSM) and surface roughness measurements. A cumulative erosion-time curve was produced from the WARER samples.

Coupled Thermal Model for Nonlinear Panel Flutter

A nonlinear formulation is developed that accounts for high-Mach-number, viscous flow over the external surface of an isotropic elastic panel. The formulation is unique in that the panel compressive stress is calculated as a result of fluid/structure thermal coupling. Two distinct heat transfer mechanisms are investigated. One is due to fluid viscosity, and the second is due to local flow over the panel. Here, in contrast with classical panel flutter studies, the in-plane load and dynamic pressure parameters are not wholly independent parameters. The equation of motion is based on von Karman large deflection plate theory and includes a geometric nonlinearity. Using Galerkin's s method, the resulting system of equations is solved by direct numerical integration. However, the parameter space representing the in-plane load is extensive, and therefore, numerical integration alone is not a feasible analysis method. As a supplement, the system of equations is analysed with a pseudoarclength continuation method. In this way, a new periodic regime is uncovered. However, the attractor becomes unstable as a result of additional heating. The results indicate that aerodynamic heating is the dominant heat transfer mechanism. For the conditions studied, the dynamic system is dominated by a stable fixed-point attractor. The aerothermoelastic panel flutter model formulated here is qualitatively similar to the classical model when the in-plane load is due to aerodynamic heating effects only.

Nonlinear flutter of orthotropic composite panel under aerodynamic heating

The problem of nonlinear aerothermoelasticity of isotropic and specially orthotropic panels in supersonic airflow is examined. The Reissner functional is used with Hamilton's principle to derive the governing equations of motion, the constitutive relations, and the natural boundary conditions. The work done by aerodynamic forces is represented by using the «piston» theory for two-dimensional lifting surfaces. The aerodynamic heating effect is estimated on the basis of the adiabatic wall temperature due to the high-speed airstream. Galerkin's method is then applied

Computer simulation of absolute and contrast infrared signatures from missile noses

A computer simulation was performed to obtain an estimate of the infrared radiant intensity and radiative contrast produced by missile noses. The temperature distribution on the nose was computed by taking into account the effects of aerodynamic and solar heating, sky irradiance, and radiative cooling. The corresponding absolute and contrast signatures were obtained by considering the influence of both atmosphere (self-emission and absorption) and target geometry (distance, aspect, and elevation angles) for six target classes, including cruise missiles, tactical ballistic missiles, and air-to-air and surface-to-surface missiles. Both radiant intensity and radiative contrast were computed as a function of missile altitude or missile distance for all targets. A comparison of radiative quantities in the 3- to 5-μm and 8- to 12-μm bands shows that usually the spectral region that gives the strongest signal is not the one that gives the highest contrast.

Effect of aerodynamic heating on deformation of composite cylindrical panels in a gas flow

In this paper, motions of composite cylindrical panels in a gas flow are considered. It is shown that the main factor contributing to large static deformations is a nonuniform aerodynamic heating, while aerodynamic pressure is of secondary importance, at high Mach number. It was found that the main factor resulting in the increase of deformations is the nonuniform distribution of temperature along the curved edges. Deformations decrease rapidly in shallower panels. Nonuniformly heated panels become unstable at the values of axial compressive load, which are much smaller than the static buckling value calculated in the absence of heating. The condition of panel flutter of nonuniformly heated composite panels in a gas flow is also formulated.

Computer modeling of infrared head-on emission from missile noses

A computer model that takes into account the effect of aerodynamic and solar heating, sky irradiation, and radiative cooling on infrared emission from missile noses is presented. The heat transfer equation was solved with numerical techniques both in the steady-state (constant speed and altitude flight of cruise missiles) and in the nonstationary regime (quickly variable speed and altitude of short to medium range ballistic missiles) to give the temperature distribution on the skin surface. The corresponding head-on absolute infrared emission in the 3 to 5 pm and 8 to 12 jim spectral bands was computed as a function of time of flight and missile altitude. Results show a strong dependence of temperature and radiant intensity distributions on thermal and geometrical properties of the skin material, on the character of the aerodynamic flow (laminar or turbulent boundary layer), and on the physical characteristics of the atmosphere. By varying these parameters into reasonable ranges, infrared emissions spanning over more than an order of magnitude were obtained. The comparison with data corresponding to a skin uniformly kept at the boundary layer effective temperature showed that huge overestimates of the infrared emission can be found when the target is flying at high speed and high altitude. By computing the ratio of the in-band total radiant intensity in the 3 to 5 p.m and 8 to 12 p.m spectral regions, the relative merits of these regions for the detection of a given target are given as a function of missile altitude.

Numerical solution of the entrainment equation

An equation describing the change in body shape as a result of intense mass entrainment from the surface under the effect of convective aerodynamic heating under the simplest assumptions (dependence of the pressure on only the local slope of the surface, the method of local similarity to compute the heat fluxes) is considered. Mathematical questions originating during its numerical solution are investigated. The instability of explicit schemes is proved in the neighborhood of the stagnation point. A stable explicit-implicit scheme, suitable for a through computation of unsmooth solutions, is proposed.

Nonlinear re-entry motion of a towed wire

Wires towed behind re-entry vehicles fail in tension due to the combined effects of aerodynamic drag and heating. Such wires experience a damped periodic motion that is essentially two-dimensional. Since both aerodynamic forces and heating are proportional to deflection, it is necessary to determine the decay of the periodic motion to analyze the survival of such a wire. In this paper the principle of virtual work is used to define the large deflection planar motion of a thin, straight, uniform cross-section elastic wire. The wire is assumed to have one end fixed and the other end free and to be subjected to time-varying deflection dependent aerodynamic forces distributed along its length. Two methods of treating the free end boundary conditions are investigated, and both methods are found to provide a good correlation of laboratory measurements of free vibration. Using these methods it is found that over the altitude range from 1000 to 350 kft, some wires of interest are predicted to remain essentially straight, so that their predicted motion can be accurately approximated by the predictions for a wire of infinite stiffness.