Transient Aerodynamic Heating Research Articles

Numerical Method for Predicting Transient Aerodynamic Heating in Hemispherical Domes

In this research, a streamlined numerical approach designed for the quick estimation of temperature profiles across the finite thickness of a hemispherical dome subjected to aerodynamic heating is introduced. Hemispherical domes, with their advantageous aerodynamic, structural, and optical properties, are frequently utilized in the front sections of objects traveling at supersonic velocities, including missiles or vehicles. The proposed method relies on one-dimensional analyses of fluid dynamics and flow characteristics to approximate the local heat flux across the exterior surface of the dome. By calculating these local heat flux values, it is also possible to predict the temperature variations within the thickness of the dome by employing the finite difference technique, to solve the heat conduction equation in spherical coordinates. This process is iterated over successive time intervals, to simulate the entire flight duration. Unlike traditional Computational Fluid Dynamics (CFD) simulations, the proposed strategy offers the benefits of significantly lower computational time and resource demands. The primary objective of this work is to provide an efficient numerical tool for evaluating aerodynamic heating impact and temperature gradients on hemispherical domes under specific conditions. The effectiveness of the proposed method will be validated by comparing the temperature profiles derived for a standard flight scenario against those obtained from 2-D axisymmetric transient CFD simulations performed using ANSYS-Fluent 2022 R2.

Thermal modal analysis of hypersonic composite wing on transient aerodynamic heating

Considering the influence of thermal stress and material property variations, this study employs the Navier–Stokes equations and Fourier heat conduction law to establish a semi-implicit time-domain numerical analysis method for hypersonic aerothermal-structural coupling. Study the temporal variation pattern of different regions of the composite material wing under aerodynamic heating. Using the obtained transient temperature field of the wing, the thermal modal of the wing at different time points is calculated using the finite element method. Additionally, it conducts an analysis and discussion on the factors influencing the thermal modal. Composites can be effectively utilized as thermal protection materials for aircraft. During the aerodynamic heating process, the leading edge temperature reaches thermal equilibrium first, followed by the trailing edge, and the belly plate experiences a slower thermal response. Temperature rise significantly affects higher-order modes, with the change in material properties during the early stages of heating being the dominant factor. This leads to a faster decrease in natural frequency. As heat conduction progresses, the influencing factors of thermal stresses gradually increase, and the natural frequency decreases slowly or even rises.

Transient Aerodynamic Heating Effects on Aeroelastic Dynamic Response of Curved Fiber-Reinforced Composite Panel in Supersonic Airflow

The nonlinear aero-thermo-elastic behaviors of the curved-fiber composite panel are studied accounting for transient aerodynamic heating effects with two-way coupling method. The Von Karman assumption is utilized to depict the large deflection of the composite panel and the supersonic aerodynamic load is incorporated through first-order piston theory, respectively. The aerothermal and aeroelastic models are coupled with each other by performing the iterative procedure in the time domain. The aerodynamic heating heat flux is obtained by the Eckert reference temperature method, the transient temperature field is solved by the finite difference method, and the aeroelastic dynamic response is solved by the combination of the Newmark method and Newton–Raphson method. The accuracy and validity of the established model are justified by comparing the present solutions with the present numerical results in published literature. Then, the influences of the key parameters such as the transient temperature field, coupling step, heat transfer coefficient, shock wave, initial disturbance force and fiber configurations on aerothermoelastic responses of the composite panel respectively are discussed in detail.

Measuring 3D shape and deformation in the presence of extremely strong ambient light and thermal radiation with a single time-gated camera.

Monochromatic light-illuminated active-imaging stereo-digital image correlation (stereo-DIC) has been extensively used for measuring the surface deformation of materials and structures at elevated temperatures. Despite the improvements in the image acquisition techniques or devices, it is still challenging to measure the 3D deformation of materials and structures in the presence of strong, time-varying ambient light and thermal radiation. In this study, we present what we believe to be a novel dual-filtering single-camera stereo-DIC technique for full-field 3D high-temperature deformation measurement, even in the case of extremely intense ambient light and thermal radiation. In contrast to conventional active-imaging stereo-DIC that only suppresses the thermal radiations in the spectral domain, the proposed technique utilized a dual-filtering strategy (i.e., narrow bandpass optical filtering and ultrashort exposing) to suppress the strong ambient light and thermal radiation in both time and spectral domains. Besides, a four-mirror adapter is adopted to realize 3D shape and deformation measurement using a compact single time-gated camera. Experimental verifications, including assessments with laboratory experiments and validations on real thermal deformation tests under transient aerodynamic heating and direct ohmic heating, convincingly demonstrated that the proposed single-camera dual-filtering stereo-DIC method can achieve accurate 3D shape, motion and deformation measurement, even with strong light and thermal radiation from the quartz lamps and the heated sample.

Adaptive modal identification of honeycomb thin-walled composite structures with pit defects under thermal modal testing using variational mode decomposition technique based on digital image correlation

The active imaging blue light high-speed three-dimensional digital image correlation (3D-DIC) system was combined with a transient aerodynamic heating system and random pulse excitation technology to establish a high-frequency thermal vibration optical test system capable of multi-temperature zone testing at 900 °C to accurately obtain the thermal modal parameters of thin-walled structures. The full-field temperature distribution of a novel honeycomb thin-walled composite structure (HTWCS) with pit defects under non-uniform temperature was accurately simulated through reinforcement learning. The first six modal frequencies of honeycomb thin-walled composite structure with pit defects at room temperature increased compared with the non-destructive honeycomb thin-walled composite structure, and the third and fourth modal shapes interchanged. An adaptive modal parameter identification method for full-field three-dimensional vibration measurements under high-temperature environments was developed by combining the successive multivariate variational mode decomposition (VMD) with the modal superposition method. This method can effectively identify close modes. The area ratio-based approach was used to evaluate the damping of the measured response. The finite element model (FEM) of the HTWCS with pit defects at different temperatures was updated using a multi-state step-by-step model updating method and the temperature-dependent material properties were established. The results showed that the introduction of a damping ratio improved the accuracy of the updated FEM of HTWCS with pit defects. The proposed technique is anticipated to provide an effective method for high-frequency thermal vibration optical measurement and modal identification of thin-walled structures under multi-temperature regions.

Time-gated active imaging digital image correlation for deformation measurement at high temperatures

We proposed a novel time-gated active imaging digital image correlation (DIC) method based on bandpass filtering and gated single-photon imaging techniques for high-temperature deformation measurement. The proposed method uses a powerful pulsed laser for illumination and then records the reflected pulsed laser light using a gated single-photon camera with an ultrashort exposure time. As a result, the received radiation light from the heated object and the ambient light can be significantly reduced to a negligible level compared with the illumination light intensity from the pulsed laser. Experiments including the varying ambient light test and thermal deformation measurement of a Ni-based alloy at around 700 °C verified the performance of the proposed method. It is observed that the established time-gated active imaging DIC system is dramatically superior to existing blue-light DIC and ultraviolet-DIC (UV-DIC) systems in preserving the image quality at high temperatures, thus showing promising application prospects in extremely challenging scenarios, such as ultra-high-temperature material testing, or thermomechanical testing of hypersonic materials and structures subjected to transient aerodynamic heating simulated by quartz lamps or an arc-heated wind tunnel.

High-temperature deformation measurement of the heated front surface of hypersonic aircraft component at 1200 °C using digital image correlation

The outside surface of a hypersonic aircraft flying in the atmosphere is in an extremely harsh high-temperature environment due to severe aerodynamic heating. It is important and difficult to measure the deformation of the heated front surfaces of aircraft components in high-temperature aerobic environments in transient aerodynamic heating experimental simulation system for high-speed aircraft. In this paper, an experimental system of strain measurement for the heated front surfaces of hypersonic aircraft components was established. The strain distribution of the front surface at temperatures up to 1200 °C in an aerobic environment was successfully obtained in combination with a digital image correlation method. The processing results of speckle images of heated front surfaces of two different materials show that the measurement results for Al2O3 ceramics have a high goodness of fit with the “strain-temperature” relationship derived based on Hillman's “thermal expansion coefficient-temperature” relationship. The experimental results of the nickel-based superalloy (1Cr18Ni9Ti) conform well with existing data, which verified the credibility and effectiveness of the proposed experimental method. The optical measurement system developed for measuring strain on the heated front surfaces of components in a 1200 °C high-temperature environment provides an important means for thermal strength analysis as well as for the safety and reliability design of the heated components of hypersonic aircraft.

Ultraviolet 3D digital image correlation applied for deformation measurement in thermal testing with infrared quartz lamps

In thermal-structural testing of hypersonic materials and structures, deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging. This work describes a novel front-surface high-temperature deformation measurement technique, which adopts ultraviolet 3D digital image correlation (UV 3D-DIC) to observe and measure the high-temperature deformation fields on front surfaces directly heated by quartz lamps. Compared with existing blue light DIC techniques, the established UV 3D-DIC, which combines UV CCD camera, active UV illumination and bandpass filter imaging, can effectively suppress the strong disturbing light emitted by the quartz lamps and the heated sample itself during heating process. Two experiments were carried out to verify the robustness and accuracy of the developed technique: (1) direct observation of front surfaces of a hypersonic thermal structure sample heated from room temperature to 1050 °C, and (2) front-surface thermal stain and coefficient of thermal expansion (CTE) measurement of an Inconel 718 sample up to 800 °C. The well matched strain and CTE results with literature data show that UV 3D-DIC system is an effective technique for front-surface deformation measurement and has great potential in characterizing deformation response of hypersonic materials and structures subjected to transient aerodynamic heating.

Experimental Investigation of Thermal Modal Characteristics for a Ship’s Foundation under 300°C

How to further reduce vibration and noise is a major challenge for modern ship design. High‐temperature environment will significantly influence the mechanical properties (such as elastic modulus and stiffness) of the ship’s foundation. These properties will have a serious impact on the inherent vibration characteristics of the foundation. In this paper, a simplified foundation is taken as the research object, and a thermal‐vibration joint test system is developed for investigating the thermal modal characteristics of the foundation under different temperatures. The joint test system consists of a transient aerodynamic heating environment simulation system and a vibration excitation and acquisition system. Finite element method (FEM) is used to analyze the distribution of thermal fields. The influence of the ceramic rods and the different ambient temperatures on the modal characteristics of the foundation is studied. The results indicate that the effect of ceramic rods on the modal characteristic of the foundation is negligible. The results also show that the greater the vibration response amplitude is as the temperature increases and the first‐order natural frequency does not change, the smaller the second‐order natural frequency and the damping ratio will become smaller. The variation of natural frequency and damping ratio of the foundation under different temperature conditions can provide a reliable experimental basis for the design of the vibration and noise reduction of the ship’s foundation in the thermal‐vibration environment.

On the response of coaxial surface thermocouples for transient aerodynamic heating measurements

Surface thermocouples are widely used in transient aerodynamic heating measurements, but their response often exhibits uncertainty and unpredictability, resulting in poor accuracy of measurement. To address this issue and provide reference information on their fabrication, the response of coaxial surface thermocouples was investigated numerically and experimentally. From the numerical simulations, it was observed that the heat blocking effect of the insulation layer can change the response of a thermocouple which strongly depends on the structure of the junction at short test times. Nevertheless, with increasing time, the response tends to be independent of the junction and be consistent with the prediction of the commonly used one-dimensional heat conduction model. Owing to the difficulty in controlling the junction, these observations not only account for the uncertainty and unpredictability of the response, but also suggest that for ensuring accurate measurements, a sufficiently long test time is necessary. The simulation also shows that the response of a thermocouple is insensitive to the properties of the insulation layer and that the duration of an uncertain response decreases dramatically with the thickness of the layer. To improve the performance of a surface thermocouple, additional effort should be directed at reducing the thickness of the insulation layer rather than enhancing its thermal properties. The shock tube experiments confirmed the achieved numerical results, and demonstrated a practical calibration technique for heat transfer gauges.

Thermo-mechanical response of superalloy honeycomb sandwich panels subjected to non-steady thermal loading

This paper investigates heat-shielding performance and 3D thermal deformation behavior of two superalloy honeycomb-core sandwich panels in time-varying thermal environment by using a self-developed transient aerodynamic heating simulation system and a novel active imaging stereo-digital image correlation (stereo-DIC) technique. To facilitate deformation measurement of large objects using stereo-DIC, a simple but practical technique is adopted for fabricating high-temperature speckle patterns on large measuring areas. The results indicate that the sandwich panels provide good thermal shielding performance under 900°C with the thermal insulation effect stabilizing at around 30%. The measured high-temperature deformation fields of the test sandwich panels reveal that an in-plane homogeneous thermal expansion occurs as expected, while the out-of-plane deformation shows evident axisymmetric distributions with the maximum deflections dependent on the temperature differences between the back and front facets. The results provide a foundational understanding on the thermal–mechanical characteristics of superalloy honeycomb-core sandwich panels, which is essential to the structural design of a superalloy honeycomb sandwich thermal protection system.

3D thermal deformation measurement of superalloy honeycomb panels in time-varying thermal radiation environment

Superalloy honeycomb panels with the advantages of light weight,high strength and excellent heat-shielding properties have been widely used in the field of aeronautics and astronautics. Deformation measurement of superalloy honeycomb panels due to transient thermal loading is essential for the design of heatshielding structures. Firstly,a self-developed infrared radiation transient aerodynamic heating simulation system was used to simulate conditions similar to transient aerodynamics service conditions and a novel active imaging three-dimensional digital image correlation( 3D-DIC) method was used to measure 3D thermal deformation of a superalloy honeycomb panel sample with a size of 210 mm × 210 mm at different times in time-varying thermal radiation environment. Secondly,to ensure the reliability of measurement by using 3D-DIC,a new technique for making large-area high-temperature speckle pattern on a test sample was proposed. The hightemperature speckle pattern stayed stable throughout the experiment and could be used as an effective carrier of thermal deformation. Finally,the largest warping displacement was also calculated by Hoff's equivalent stiffness theory. Study results indicate that in-plane thermal expansion is homogeneous when the panel is heated one-side by radiation heating,while the out-plane displacements show evident axisymmetric warp deformation with the largest warping displacement of approximate 1. 6 mm at a temperature of 900℃. The experimental results agree well with theoretical predictions made by Hoff's equivalent stiffness theory.

Insulation Performance of Heat-Resistant Material for High-Speed Aircraft Under Thermal Environments

Lightweight insulation materials are widely used to thermally protect high-speed aircraft, such as missiles. Thermal conductivity is an important parameter used to evaluate the efficiency of a material’s thermal insulation performance. Since thermal conductivities provided from material handbooks or manufacturers are discrete data for different temperature ranges, there is a deviation between those and actual parameters in terms of continuous nonlinear variations. Therefore, this study measures the thermal conductivities of lightweight thermal insulation materials at high temperatures, and the relationship between the thermal conductivity and temperature is obtained. A finite element model of the thermal insulation materials is also established and applied to numerically calculate the thermal insulation properties for high-temperature ceramic fiber insulation materials using the experimentally obtained nonlinear relationship between thermal conductivity and temperature. Additionally, a transient aerodynamic heating experiment simulation system is used to thermally test the same materials; the calculated and experimental results for the same materials are compared, which exhibit good consistency that demonstrates that accurate results can be obtained from the numerical computation using the relationship established from the experimentally measured conductivity and temperature.

High-speed and accurate non-linear calibration of temperature sensors for transient aerodynamic heating experiments

Transient aerodynamic heating experiments with high-speed aircraft require temperature sensors that can carry out rapid and accurate electromotive force (EMF)–temperature conversions. A fast, high-precision non-linear EMF–temperature conversion method is proposed. In this method, the temperature values to be converted were pre-positioned using a non-linear mathematical model. Then, they were accurately positioned using an efficient binary search algorithm with a small scope. Thus, this method has rapid conversion speed and high calibration precision. This conversion precision is enhanced by one order of magnitude over that of the normal reference table, and the conversion time is 1% of that of the traditional piecewise linearization method. This method was employed in a transient aerodynamic heating experimental simulation system with high-speed aircraft. The experiment results show that, in the case of a high change rate of temperature and heat flux, accurate dynamic tracking can still be realized, and the experimental simulation results agree well with the pre-set environment. The developed temperature sensor calibration method is necessary for high-speed and high-precision aerodynamic heating experiments with hypersonic aircraft.

Mullite fiber sealing pad with favorable high-temperature rebound resilience fabricated through colloidal processing

Mullite fiber sealing pad composed of chopped fibers and aqueous silica binder, having near-isotropic structure, was fabricated by a combination of vacuum filtration and colloidal processing. The fibers were randomly distributed, overlapping and interlocking to produce the matrix and pure SiO2 binder composed of a glass-ceramic structure firmly bonded fiber laps. A microwave micro-zone heater was adopted to simulate transient aerodynamic heating process and 8-cycle loading–unloading test was conducted at 800°C. The samples were sintered at 1300°C with different silica sol concentrations (10.3–20.9wt%). Mullite fiber pads exhibited high rebound resilience (80.9–87.6%), high compression (24–18%) and moderate Young′s modulus (0.97–3.24MPa), making it to be a promising high-temperature seal material.

Rapid High-Precision Non-Linear Calibration for Temperature Sensors in Transient Aerodynamic Heating Simulation Systems

In order to accurately simulate the transient aerodynamic heating conditions experienced by aircraft when flying at high speeds, rapid and highly precise non-linear dynamic control of the heating process in aerodynamic simulation experiments must be conducted using a transient heat flux control system. This process involves carrying out ‘thermoelectric potential - temperature (E-T)’ conversion of sensors. Here a fast and high-precision ‘E-T’ sensor conversion method for the transient aerodynamic heating control systems of high-speed aircraft is proposed. The developed method has the advantages of easy calculation, rapid conversion speed and high calibration precision, and can thus be employed for fast non-linear dynamic control of rapidly-changing temperature fields in the aerodynamic heating process of high-speed aircraft.

Research on Control of Heat Flux Environment Simulation for High-Speed Aircraft

The characteristics of the transient heating control process of aerodynamic simulation experiments are complicated, transient, highly nonlinear, and strongly coupled, which make it difficult or impossible to develop a mathematical model. By using the fuzzy control method, many good qualities (such as robustness, high adaptability to changing parameters, and a short transition process time) can be obtained. Based on the fuzzy control method, a transient aerodynamic heating simulation control system for missiles was established. It was demonstrated that quick dynamic control of the aerodynamic simulation heating process according to the transient and continual change in heat flow on the surface of high-speed aircrafts can be completed by using this control system.

Fast and High Precision Thermoelectric Potential – Temperature Conversion Method for Aerodynamic Heating Control Systems

A fast and high-precision ‘thermoelectric potential - temperature (E-T)’ sensor conversion method for the transient aerodynamic heating control systems of high-speed aircraft is proposed. The developed method has the advantages of easy calculation, rapid conversion speed and high calibration precision, and can thus be employed for fast non-linear dynamic control of rapidly-changing temperature fields in the aerodynamic heating process of high-speed aircraft.

Experimental research on the ultimate strength of hard aluminium alloy 2017 subjected to short-time radioactive heating

Alloy 2017 (Al–Cu–Mg) is a hard aluminium alloy strengthened by heat treatment. Because of its higher strength, finer weldability and ductility, hard aluminium alloy 2017 has been widely used in the field of aeronautics and astronautics. However, the ultimate strength and other characteristic mechanical parameters of aluminium alloy 2017 in a transient heating environment are still unclear, as these key mechanical parameters are lacking in the existing strength design handbook. The experimental characterisation of these critical parameters of aluminium alloy 2017 is undoubtedly meaningful for reliably estimating life span of and improving safety in designing high-speed flight vehicles. In this paper, the high-temperature ultimate strength, loading time and other mechanical properties of hard aluminium alloy 2017 under different transient heating temperatures and loading conditions are investigated by combining a transient aerodynamic heating simulation system and a material testing machine. The experimental results reveal that the ultimate strength and loading capability of aluminium alloy 2017 subjected to transient thermal heating are much higher than those tested in a long-time stable high-temperature environment. The research of this work not only provides a substantial basis for the loading capability improvement and optimal design of aerospace materials and structures subject to transient heating but also presents a new research direction with a practical application value.

Proper Orthogonal Decomposition for Reduced-Order Thermal Solution in Hypersonic Aerothermoelastic Simulations

The ability to perform full-order aerothermoelastic simulations of hypersonic vehicles is hindered by the strong coupling exhibited between the aerodynamics, heat transfer, and structural dynamic response in the hypersonic ight regime. As a result of these interactions, alternative techniques are necessary to obtain computationally tractable systems of governing equations and their solutions. This work addresses the use of proper orthogonal decomposition for reduced-order solution of the heat transfer problem within a hypersonic modeling framework. The specic challenge of handling time-dependent boundary conditions due to transient aerodynamic heating is discussed. An overview of the proper orthogonal decomposition is given and two methods for solution of the reduced system of ordinary dierential equations are outlined. The methodology is applied to a representative hypersonic vehicle control surface model for two cases in which the time-history of the thermal load vector is known a priori: one in which the boundary conditions are time-independent and another in which they are time-varying. Results demonstrate the ability of the reduced-order solution to approximate the full-order solution with reasonable accuracy. Finally, a time-marching hypersonic aerothermoelastic framework is described in which proper orthogonal decomposition is used for the transient thermal solution.