Mesh deformation is a main method to implement the computational mesh deformation with a moving boundary in computational aeroelasticity. First, an investigation of the status of the current advances in the researches on mesh deformation is presented in this paper, and some common mesh deformation approaches in recent years are reviewed in detail, which are spring analogy method, elastic solid method, transfinite interpolation method, Delaunay graph method, radial basis function method and temperature analogy method. Besides, based on the established models, the existing methods can be classified into physical model method, mathematical interpolation method and hybrid approach. A brief introduction of each method is made on theoretical method and research advance. The main emphasis is on the difference among the three methods of advantages and disadvantages as well as properties including deformation capability, deformation quality and efficiency. As an important aspect in computational aeroelasticity, the calculation data transformation between flow field boundary and structure boundary is summarized as well. At last, the present problems of mesh deformation which are frequently encountered in computational aeroelasticity are discussed, and in order to meet the needs of projects, possible prospects in future mesh deformation investigations are also proposed.

With the Shenzhou spacecraft entering into the stage of maturity, it is of necessity to launch the research and development of a new-generation multi-purpose manned spacecraft. In this paper, we firstly generalize the technological characteristics, the design concept and the status quo of the foreign new-generation manned spacecraft. Based on this, we summarize their technological trend, i.e., multi-task adaption, cost reduction, bluntbody aerodynamic configuration, high safety reliability and new lightweight materials. Then, we primarily analyze the task requirements of China's new-generation manned spacecraft, including low earth orbit flight mission, as well as manned flights to the Moon, the asteroid and the Mars. We basically set the parameters of the overall performance. Finally, we sort out the technological approaches of it and propose two design schemes, which could provide some reference for the research of China's new-generation manned spacecraft.

For the two-stage weighted least squares (TSWLS) technique of passive source localization using time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements, which has the problem that the root mean square error (RMSE) and localization bias is large as the measurement noise increases. Based on analyzing the factor influencing the performances of the TSWLS firstly and then improves the TSWLS via Taylor-series (TS) expansion technique. The first stage of the new algorithm is the same as the one of TSWLS. At the second stage of the new algorithm, the localization error of the first stage is identified through utilizing the first-order Taylor-series expansion. Through updating the first-stage localization error, the final localization output is obtained. Theoretical performance analysis shows that the proposed estimator can attain the Cramer-Rao lower bound (CRLB) accuracy. Computer simulations are used to contrast the new technique with the TSWLS algorithm, the iterative maximum likelihood method based on TS and the constrained total least squares (CTLS) algorithm in terms of their localization RMSE and the localization bias. The new algorithm whose complexity is almost the same as TSWLS, the RMSE and localization bias are lower than TSWLS, TS and CTLS algorithm.

Trajectory tracking control system is used for decoupling the control unmanned helicopter, which is a nonlinear system with multi-input/multi-output and strong coupling effects. In order to avoid the dependence on accuracy of unmanned helicopter physical parameters measurement and identification and to reduce external disturbance impact, a multi-loop controller based on linear active disturbance rejection control (LADRC) is proposed. At first, the flight dynamics model is built for unmanned helicopter X-Cell. The atmospheric disturbance model, which contains wind shear, turbulence and gust model, is also set up for accurate simulation of real flight environment. Secondly, X-Cell is trimmed for verifying the accuracy of dynamic model and trim algorithm. A set of calculation values is selected as the initial state and input of the subsequent simulation. Then attitude, velocity and position control loop are built based on the first-order and second-order LADRC controllers which are selected according to system order. Combined with the time-scale separation principle, the whole trajectory control system is constructed from inner loop to outer loop. After that, the stability of the system is analyzed. The characteristic roots show that the whole system becomes stable with the trajectory controller. Finally, flight simulation experiments under various disturbance conditions are performed. The results show that the established control system can achieve a good climbing figure-eight trajectory tracking. Compared with controller based on proportion integration differentiation(PID), the controller based on LADRC has better robustness and capability of anti-disturbance.

To solve the inefficient problem of reliability-based multidisciplinary design optimization (RBMDO), which is caused by the nested optimization process and repeated iterations of multidisciplinary analysis and reliability analysis, a new method integrating Bi-level integrated system collaborative optimization (BLISCO) and improved performance measure approach (iPMA) is proposed. Firstly, with the sequential idea, the whole process is decoupled and the repeatedly reliability analysis of overall reliability model is avoided. Then, an efficient and suitable BLISCO strategy for dealing with the multidisciplinary design optimization (MDO) of complex engineering system is adopted, which abandons the consistency constraints of collaborative optimization as well as the complex analysis and approximate modeling problems of Bi-level integration system synthesis. Thirdly, the performance measure approach (PMA) is improved by updating angle strategy to evaluate the reliability, which can reduce a great number of multidisciplinary reliability analysis. Finally, a shock absorber design example of landing gear has been implemented to verify the efficiency of the proposed method. The results show that the efficiency of the proposed method has been improved by 30.93% and 19.97% respectively compared to the other two methods. Therefore, it is valuable in engineering design and optimization.

The flexibility method and modal approach are usually used in structural analysis in the static aeroelastic research. Compared to the flexibility method which is mature but brings higher computational cost for the solution,the modal approach has the advantage of significant reduction in the dimension of the problem,high efficiency and convenient for verification. However, there are no principles for the selection of modes and one must have enough engineering experience to fully utilize the modal approach in practice. To provide modal approach with its own quantitative criteria in practice, this paper first proposes the idea of modal influence coefficient to evaluate the effect of modal selection on modal approach of aeroelastic analysis. In order to validate the rationality and validity of the modal influence coefficient, the paper carrys out control efficiency and aeroelastic correction analysis for a typical aircraft. The results show that the modal influence coefficient can accurately evaluate the effect of modal selection on static aeroelastic analysis, thus providing some helpful reference in practice.

In order to investigate the influence of fiber surface state on the microstructure and phase composition of C/C-SiC composites, the surface composition of carbon fibers is modified by heat treatment, and then the fibers with different surface compositions are used to fabricate the C/C-SiC composites via liquid silicon infiltration technique. The surface composition of carbon fibers is measured by XPS (X-ray photoelectron spectroscopy). Results reveal that the oxygen content on the surface of carbon fibers decreases with increasing the treatment temperature. The low oxygen content led to small numbers of oxygen-containing functional groups, resulting in small pore size and a high porosity in C/C perform. After infiltrating the liquid silicon into C/C preform, the morphologies of C/C-SiC composites are observed by scanning electron microscopy(SEM). It is found that the microstructure and phase composition of C/C-SiC composites are quite dependent on the surface composition of carbon fibers. With decreasing the oxygen content on the carbon fiber surface, the SiC content in matrix increased, but the residual Si is reduced. Particularly, in the case of fibers with low oxygen content on the surface, there is almost no residual Si in matrix, and the composites presented a more homogeneous distribution of SiC matrix. Based on the results mentioned above, it can be seen that the microstructure and phase composition of C/C-SiC composites are controlled by the size and distribution of pores, which is closely associated with the surface state of carbon fibers. For the C/C preform with large pore size, during the liquid silicon infiltration, the formation of SiC is dominated by the solution-precipitation reaction and the interface-limited diffusion reaction mechanisms. In the case of C/C preform with small pore size, the formation of SiC is mainly controlled by solution-precipitation reaction mechanism.

The blade fatigue failure is a common aeroelastic problem of axial compressor. The phenomenon accompanied with blade vibration is abnormal acoustic field generation in compressor duct. The frequency of sound field generated by non-synchronously vibrating rotor blades is unequal not only to the compressor rotational frequency, but also to the blade passing frequency that is identical with sound generated by stator and rotor interaction. Meanwhile the frequency cannot be explained by typical Doppler shift phenomenon. In this paper, a theoretical model based on the three-dimensional lifting surface theory has been built to demonstrate the frequency and circumferential modal characteristics of the sound generated by rotor blades vibration. The developed model illuminates the fact that the sound frequency and circumferential mode depend a lot on the inter-blade phase angle. The experiment results verify the relationship between sound generation and blades vibration given by the model.

Surface treatment on titanium sheets by NaTESi anodization at constant voltage is conducted to improve the bonding properties of TA2/polyetheretherketone (PEEK) in TA2/C_f/PEEK laminates. The effects of technical parameters (such as voltage, time and temperature) on the single lap joint shear strength and the surface roughness of TiO₂ film are investigated by an orthogonal test. It demonstrates that the most important factor affecting the bonding properties is time. Longer anodization times resuted in lower surface roughness, which contributed to inferior bonding properties. Properties of the TA2 laminate are investigated by XRD and SEM, and the results show that the optimized process which is favorable for the increase of the bonding strength is as follows: anodizing voltage 10 V, anodizing temperature 35℃ and anodizing time 10 min. The surface roughness treated by this method is 1.34 μm and the nano-particles morphology appeares, which the size of the particles is about 100-200 nm. The single lap joint shear strength with these parameters could reach 19 MPa. The resistance to delamination between the titanium sheet and PEEK in this optimized process is measured in a double cantilever beam test. The average energy release rate of the TA2/PEEK interface which was prepared by the method of NaTESi anodization is 188.1 J/m², which showes an increase of 103.1% compared with the untreated ones. The results indicate that the anodizing process markedly enhance the delamination resistance of TA2/PEEK bonding interface.

In this paper, B-spline basis function is implemented in class and shape transformation (CST) parameterization method in place of the traditional Bezier polynomials to enhance the local ability of control and accuracy to represent an airfoil shape. To guarantee the requirements on geometric smoothing performance and proper orthogonal decomposition (POD) reconstruction accuracy in airfoil design optimization process, the local fairing method for multi-resolution airfoil is proposed based on the wavelet decomposition technique, expanding the design space. A surrogate model based on POD method and γ-Re_θt transition predicting model is adopted to achieve fast and accurate prediction of aerodynamic forces and transition. The computed results of flow around airfoils show that the combined surrogate model is an effective method in design optimization of natural laminar airfoil. A complete aerodynamic design optimization system for natural laminar airfoil is constructed by integrating genetic algorithm, the improved CST parameterization method with wavelet decomposition fairing, POD surrogate model and γ-Re_θt transition model. The system is used for the design optimization of low-speed and transonic airfoils, achieving an increase in lift-drag ratio of 47.42% and 45.85%, respectively, which validates the efficiency of the design optimization system proposed in this paper.

The existing feature point extraction methods usually cost a lot of CPU time when they are applied to large size aerial images. For the purpose of fast extraction of feature points in these large size aerial images, a novel method is developed. Usually these aerial images have not only large sizes but also wide ranges of shooting. They usually have different feature point performances on different scales and the distributions of spectra are uniform in the frequency domain. In this paper, the scales of the feature points are kept by employing the Laplacian pyramid, and a specified non-uniform N-dimensional directional filter bank is applied to decompose the pyramid images. The scales and the directions of the images are extracted. Then the local extreme points are extracted as a candidate feature points set. Finally, the candidate feature points in different directions are merged by a specified merge-strategy. Thus, we obtain the final feature points set and the directions of the feature point described by the direction filter bank. Experimental results are presented that demonstrate the proposed method is efficient for large size aerial images while meeting the match rate and precision rate requirements.

Air-breathing hypersonic vehicle is highly integrated making its design challenging. All vehicle parts and functions interact including aerodynamics, propulsion, control, structure, tank and thermal protection, especially for airframe and scramjet engine coupling. The lower wall of the aircraft forebody and afterbody is either compression part of the engine inlet or expansion part of the engine nozzle and it produces lift and pitching moment as well as thrust. The strong coupling of the airframe and engine has direct influence to the thrust, lift, drag, pitching moment, aerodynamic heating, airframe cooling, stability and control characteristics of the vehicle. The research developments of airframe-propulsion integration technology are introduced and the related works of China Aerodynamics Research & Development Center (CARDC) are emphasized. These works included osculating curved cone waverider inlet design, double shockwave axissymetric flow field-based inward turning inlet design, airframe-propulsion integrated vehicle tests in pulsed combustion heated hypersonic high-temperature wind tunnels and hypersonic large-scale parallel numerical simulation platform (AHL3D). The related fundamental researches of hypersonic shock-boundary layer interaction, compressible turbulent transition of flow separation mechanism and its control, scramjet combustion study on flow mechanism and other related basic issues are introduced. The urgent need of efficient high-precision calculation method is emphasized.

Conjugate heat transfer simulation is used to conduct investigations aiming at obtaining the cooling performance of the internal cooling structures of a certain turbine rotor blade in this paper. Effects of three different airflow allocation methods on the cooling effect of the blade are analyzed under the condition of the same total airflow. Subsequently, the cooling structure with the best cooling performance is chosen to discuss the influence of rotational speed on total inlet pressure and overall cooling effectiveness. The results show that Model B produces more reasonable airflow allocation, obtaining more uniform temperature distribution and higher overall cooling effectiveness. The cooling airflow deflects due to the existence of Coriolis force and centrifugal buoyancy force. The stagnation line located at the blade leading edge is forced to shift from pressure side to suction side with the increase of rotational speed and the film discharges are also changed with the rotational speed. The increasing rotational speed leads to an improvement on pressure surface cooling effectiveness and inversely a decrement on suction surface cooling effectiveness.

Flow instability is a great challenge in turbomachinery, and rotating stall is one major type of flow instability in compression system of aero-engine. In the present paper a rotating stall inception model based on a general eigenvalue theory of flow stability is developed with an emphasis on flow instability onset in axial transonic compressors. After solving the established eigenvalue equation using the spectral method and the singular value decomposition (SVD) method, the onset point of flow instability is determined by the imaginary part of the resultant eigenvalue. The significant effect of flow compressibility on the stall onset point calculation for a transonic rotor is studied by comparing the prediction results for a high speed single rotor at both high and low rotational speeds. The capacity of the present model to predict the stall inception point is assessed against the experimental data of a transonic single stage compressor. It is verified that this model is capable of predicting the mass flow at the stall onset point of a multi-stage transonic compressor flow with reasonable accuracy without numerous empirical data, and it is sustainable in terms of computation cost for industrial application.

This paper presents some analytic expressions associated with those well-known skin-friction formulas for turbulent shear flows. Two methods were developed for this aim. The first one is an approximated analytic solution for the same super-algebraic equation; And the second one is a method of iteration and its convergence has been proven. The skin-friction formula of D.B.Spalding has also been improved in the present work.

Appearance-based hand pose estimation which relies on computer vision techniques is adopted to realize natural interaction in a semi-virtual reality cockpit. To cope with the low efficiency and high memory consumption in large capacity and high-dimension feature indexing, an improved locality sensitive Hashing (LSH) method is proposed in this paper which combines the multi-probe principle with the nearest-neighbor table. Moreover, a forecast model which predicts indexing performance and a parameter optimization method are used to achieve better indexing performance. Experimental results show that the forecast model is appropriate for practical indexing performances and the time consumption is reduced by 41.9% at the cost of a slight recall rate drop. In summary, the application of the improved LSH to hand pose estimations able to upgrade virtual hand visualization and hand posture reconstruction in a semi-virtual reality cockpit.

Numerical simulation study is conducted of the heat transfer of cryogenic methane flowing inside a rectangular engine cooling channel under supercritical pressure with consideration of the coupled thermal conduction in the solid channel region. The effects of wall heat fluxes and cooling channel geometries on the fluid flow and heat transfer processes under supercritical pressure are carefully examined. Variations of the fluid velocity, channel wall temperature, wall heat flux, and Nusselt number are obtained and discussed. Results indicate that with consideration of the conjugate heat transfer in both the solid and fluid regions, a fraction of the heat flux imposed on the top channel surface is transferred into the cryogenic methane through the side walls. As the imposed wall heat flux increases, more heat can be thermally conducted into the side channel walls. Decreasing the cooling channel height/width aspect ratio leads to enhanced heat transfer, but the pressure loss also increases significantly. Therefore, the combined effects of the channel aspect ratio on both heat transfer and pressure loss has to be taken into consideration to obtain an optimum cooling channel design. The thermal performance parameter can be used as a reference in this regard. The modified Jackson & Hall coefficient is applicable to heat transfer prediction under supercritical pressure with acceptable accuracy under all tested conditions in this paper.

A general generation method is presented for the 3 D multiply blocked structure grid of a complex configuration flying body.The structure grids can be generated by decomposing the domain into any number of contiguous blocks,and each physics region can be considered to have been transformed to a rectangular computational region on which the curvilinear coordinates are the independent variables.Thus the generated grid is not too skew or unregular.Effect of control functions on grid generation is discussed.The given examples showed that the method may deal with arbitrary complex 3 D domains with the multi blocked structure technique.

Mode localization is often an unexpected dynamic phenomenon in weakly-coupled symmetric structures, and it arises from small imperfections (less than 5%) which perturb the symmetry of a structure. Such imperfections typically result from random manufacturing or assembly imprecision. Mode localization prediction is an important issue in T-tail structure design because drastic localized vibration phenomena may occur during the ground vibration test of a T-tail aircraft. Mode localization is dependent not only on parameter mistuning, but also on coupling degree. In this article the definition of mode localization is improved according to the peak amplitude ratio. The coupling degree is defined according to the effect of the stiffness of the horizontal stabilizer and fin on the modal frequencies of the T-tail structure. The mode localization and frequency loci veering phenomena for a T-tail structure is then studied and the effects of mistuned mass, mistuned stiffness and the location of mistuning on the mode localization of the horizontal stabilizer are investigated. Numerical simulation results for a T-tail structure model indicate that mode localization is most likely to occur in a T-tail structure consisting of weakly coupled substructures—a horizontal stabilizer and a fin. Moreover, when mode localization occurs, the first two bending vibration modes in the T-tail structure are prone to localization, and only one of the two modal frequencies is changed by parameter mistuning to induce frequency loci veering. The simulation also demonstrates that if mass or stiffness mistuning occurs to a horizontal stabilizer, the amplitude of the bigger mass side or smaller stiffness side is greater than that of the peer side. The study suggests that mode localization design is easy to achieve in T-tail structures by introducing mass mistuning on the tip of the horizontal stabilizer or stiffness mistuning on the root of the horizontal stabilizer.

A real-time and accurate health condition prediction for an inertial platform is essential for cost-effective and timely maintenance planning and scheduling. Due to the fact that the true health condition of the inertial platform cannot be observed directly, it is assumed that the observations of characteristic parameters are available from monitoring, and the characteristic parameters correlate with health condition of the inertial platform. In this article, a health condition prediction system for the inertial platform is established based on belief rule base (BRB), where the characteristic parameters of the inertial platform are used as the inputs of BRB system and the health condition of platform as the output consequence. To overcome the drawbacks of current parameter optimization algorithms for BRB and satisfy real-time prediction, a parameter estimation algorithm is investigated for online updating BRB prediction system based on the expectation maximization (EM) algorithm. When the new input-output information of system operation is available, the model parameter can be updated online. Real-time health condition prediction for the inertial platform system is validated using the established model and the algorithm under investigation. The experimental results show that the proposed method can implement online parameter estimation of health condition prediction for the inertial platform effectively. In addition, compared with offline parameter optimization method, the proposed method can generate better results in terms of prediction accuracy and operating time, and thus has great potential in engineering practice.

To deal with the path planning problems of irregularly shaped objects in complex environment, a genetic collision avoidance algorithm with kinematics constraint is developed. This algorithm is then applied to the path planning operations on carrier-based aircraft scheduling on carrier flight deck. Moreover, it can be extended to solve other path planning cases under such constraints. For the problems resulting from these objects, which are characterized by complex shape and the bending radius constraint while moving in complicated obstacle situations, the technique proposed is proved to be effective. Based on the traditional genetic path planning algorithm, a three-dimensional position and orientation coding method, a three-stage path decoding method and an approach specific to the collision detection and distance calculation of a track bounding box are presented. Also, a penalty term and a gene repairing strategy are brought into the genetic process to seek the optimum. Finally, simulated verifications are conducted using VC++ platform to obtain the optimal paths. The results show that the optimal collision avoidance paths in complex obstacle environment are achieved utilizing the proposed algorithm, with the pre-set bending radius constraints satisfied. It is indicated that the design yields effective solutions to the collision avoidance path planning problems correlated with this kind of objects.

Recent years have witnessed extensive discussions on the change of warfare forms and the development of post-4th generation fighters against the background of great power competition and batches of 4th generation fighters entering service. This paper reviews the origin of fighter generation classification and the driving elements behind each generational leap, outlining the evolution of Observe, Orient, Decision, Act (OODA) loops for air combat and proposing the essence of OODA 3.0. After a summary of the supportive and progressive relations among mechanization, informatization and intelligentization, it explores the dialectical relationship among autonomy and manned/unmanned, as well as that among platform, system of systems, and distributed operation, followed finally by a discussion of an agile and efficient development approach of future fighters.

Over the past two decades, surrogate modeling has received much attention from the researchers in the area of aerospace science and engineering due to its capability of greatly improving the efficiency of design optimization when high-fidelity numerical analysis is employed. Design optimization via surrogate models is intensively researched and eventually leads to a new type of optimization algorithm which is called surrogate-based optimization (SBO). Among the available surrogate models, such as polynomial response surface model, radial-basis functions, artificial neutral network, support-vector regression, multivariate interpolation or regression, and polynomial chaos expansion, Kriging model is the most representative surrogate model which has great potential in engineering design and optimization. In the context of aircraft design, this paper reviews the theory, algorithm and recent progress for researches on the Kriging surrogate model. First, the fundamental theory and algorithm of Kriging model are briefly reviewed and the experience about how to improve the robustness and efficiency is presented. Second, three major breakthroughs of Kriging model in recent years are reviewed, including gradient-enhanced Kriging, CoKriging and hierarchical Kriging. Third, the optimization mechanism and framework of surrogate-based optimization using Kriging model are discussed. In the meanwhile, the concept of infill-sampling criterion and sub optimization is presented. Five infill-sampling criteria as well as the dedicated constraint handling methods are described. Furthermore, the newly developed local EI (expected improvement) method and termination criteria for SBO are introduced. Fourth, a number of test cases including benchmark optimization problems as well as aerodynamic and multidisciplinary design optimization problems are given to demonstrate the excellent performance and great potential of the surrogate-based optimization using Kriging model. At last, the key challenges as well as future directions about the theory, algorithm and applications are discussed.

In single channel SAR, the echo from a slow moving target is confused with ground clutter in time、space and frequency domains. If the information about fixed clutter in SAR image can be used to suppress the background clutter, the detection of moving target will be easy. The fractional Fourier transform is a linear operator, and will not be influenced by cross terms. The FrFT is a way to concentrate the energy of the echo from a ground moving target. In two symmetry fractional Fourier domains with two inverse rotation angles of every SAR image tangential line, the static clutter’s spectrums are same, while the moving target’s are different. The absolute value subtracting of the two signals can be expected to have superior moving target detection performance. The experiment result proveds the validity of this method.

This article establishes a general numerical scheme which incorporates the accurate transport and thermodynamic property calculations of a fluid under supercritical pressures based on a modified corresponding-state method and the fundamental thermodynamic relationships with the Soave-Redlich-Kwong (SRK) equation of state. A comprehensive numerical investigation of the turbulent convective heat transfer with n-heptane, a typical hydrocarbon fuel, under supercritical pressures is systematically conducted. This heat transfer phenomenon is closely related to engine cooling technique in rocket and hypersonic propulsion systems. The effect of the supercritical pressure on fluid flows and heat transfer phenomena is examined in detail. Variations of the Nusselt number are elucidated and compared with those obtained from the available empirical formulae. Numerical results indicate that under supercritical pressures, the Nusselt number decreases with decreasing pressure, and that turbulent heat transfer becomes weakened and slightly oscillated near the critical region.

The prediction of residual life (RL) is the key of the predictive maintenance for engineering equipment. Accurate and real-time prediction can provide more effective decision support to the subsequent maintenance schedule and avoid the failure effectively. In engineering practice, the performance index reflecting the degradation process of the equipment is generally not observed directly. To tackle the residual life problem under hidden degradation, a prediction method based on semi-stochastic and expectation maximization (EM) algorithm is proposed in this paper. First, the residual life is taken as the hidden state and the prediction model is constructed by building the stochastic relationship between the residual life and monitoring data. Secondly, based on the monitoring data up to the current time, a collaborative method by the extended Kalman filter (EKF) and expectation maximization algorithm is presented to achieve a real-time estimation and updating of the residual life distribution and unknown model parameters. Finally, the proposed method is validated by the application to the inertial measurement unit (IMU) and the results indicate that the method can improve the accuracy and reduce the uncertainty of the estimated residual life.

Euler/RANS-based CFD methods have been rapidly developed and widely used in aeronautics since the 1980s, making remarkable achievements and playing an important role in aircraft development and aerodynamic research. This article reviews the achievements of CFD in military and civil aeronautics in the past four decades and analyzes its shortcomings, particularly the problem in separation flow simulation due to the turbulence modeling. The development of aeronautics CFD is discussed from the perspectives of turbulence models and numerical schemes. Finally, a brief conclusion and suggestions on future development are presented.

In this paper investigate the alignment problem of a stationary based strapdown inertial navigation system . In order to improve the aligning accuracy and shorten the aligning time, a Gauss-Hermite filter (GHF) is adopted in the alignment model based on large azimuth misalignment angles. The nonlinear Gauss integration of multi-variables to the mean and covariance computation in the GHF is addressed. Since large azimuth misalignment angles will introduce the nonlinearity in the alignment error equations, this paper employs linear state transformation approach to obtain the analytic solution of the linear state vector in the underlying equations. The integration of multi-variables is thus converted to the integration of a single-variable. Hence the so called "dimension problem" in the application of GHF to alignment is solved without loss of accuracy. The proposed method is applied to a SINS, and it shows that the aligning accuracy of path angle is improved by 16% and the aligning time is reduced by 75% compared with extended Kalman filter (EKF) and unscented Kalman filter (UKF).

Based on uniform circular arrays (UCAs), a high-precision estimation of 2D direction angle for multiple sources is proposed. First, exploiting information of source in 2D space-time domain forms the space-time rotational matrix, so that the multiple sources are separated. Second, based on a direct array manifold in UCA, the azimuth and elevation are estimated by Least Squares (LS). Finally, the removal method of cyclic ambiguity is presented. Numerical results show that the advantages of estimator are high precision and robustness to amplitude and phase error of sensor gain.

The erosion wear resistance is one of the most important properties of abradable seal coating. The erosion wear behaviour and mechanism of several kinds of middle temperature abradable seal coatings were investigated by a CMS 100 self made vacuum sand erosion machine. The results show that the relationship between the erosion weight loss and the erosion time is linear, the coatings hold a maximum erosion rate at 60° impact angle, and the relation between the erosion rate and the impact speed is an exponential function. The speed exponent increases with the increase of the impact angle. At 90° impact, the abrasive particles impinging on the coating surface produce indents and extrude lips, then the lips are work hardened and fall off; and flattened metal phase grains are impinged repeatedly, loosen and exfoliate. At 30° impact, the micro cutting, plowing and tunneling via pores and non metal phase are involved. The model of the erosion mechanism is advanced on the basis of the above mentioned erosion behaviour.

The combustion characteristics of single boron particle in forced convective flow in ramjet engines are investigated systemically. A physical and mathematical model is proposed taking into consideration the gas flow around the particle, the gas diffusion and the surface finite reaction dynamics. The two-dimensional axi-symmetric Navier-Stokes equations with species reactions are solved using the finite volume technique. And the numerical simulation method is validated. Then influencing factors such as the free stream velocity, particle radius, the ambient oxygen mass fraction and the ambient pressure on the combustion characteristics of single boron particle are studied by numerical simulations. And the effect mechanism for each factor is analyzed in detail. The numerical prediction results show that in forced convective flow, both the mass rate and the mass flux of the buring boron particle increase with the increase in the free stream velocity, the particle radius, the ambient oxygen mass fraction and the ambient pressure. A comprehensive analysis of the results is conducted and it is found that the mass flux of the buring boron increases with the stream Reynolds number. Then the mass flux of the buring boron particle in the static atmosphere is modified based on abundant numerical results to describe the combustion characteristics of the boron particle in forced convective flow.

Friction drag is the major part of the total drag of a transport, so reducing it is essential for improving the performance and reducing the cost of a transport. Since laminar friction drag is much less than the turbulent one, one of the important measures for reducing it is to increase the laminar flow extent, and if possible, to realize a fully laminar flow. For that, three types of laminar flow control technology, i.e., natural laminar flow, fully laminar flow and hybrid laminar flow controls, are formed. In the present paper, drag reducing analysis, the concepts, methods, potential benefits and design methods of laminar flow control technology, and operational maintenance of a laminar flow aircraft (including protection of insect contamination and ice accumulation) are systematically described; Summary of researches of laminar flow control technology during 1930-2000 is briefly introduced and the progress in this field is shown by using examples of X-21A slotted suction flight tests, simulated airlines flight tests of Jetstar HLFC leading edge systems and Boeing 757 HLFC flight tests, and future research is also pointed out.

In the analysis of the development cost of an aircraft there are usually only small samples with a large number of cost drive factors. In view of this fact and considering the advantages of hierarchical partial least squares regression (Hi-PLS) in building a regressive model in the condition of a large number of variables, an application of Hi-PLS to aircraft development cost prediction is proposed using the development cost prediction of a fighter plane fuselage as an example. After the cost drive factors of the fighter plane fuselage development cost are grouped, Hi-PLS is applied to the regress of the grouped cost drive factors, and a fuselage development cost prediction model is established. The calculated results in the example show that Hi-PLS model can reflect satisfactorily the correlation between fuselage development cost and performance parameters of a military aircraft.

A CFD study on the reduction of aerodynamic heating on the nose of a reentry vehicle by an opposing jet thermal protection system is conducted, by means of which the flow field parameters, reattachment point position, surface pressure distribution and heat flux distribution are obtained. The physical mechanism of the reduction of heat flux is analyzed. The opposing jet interacts with the freestream to form a Mach disk which enables the freestream to flow to the edges rather than interact with the surface to produce aerodynamic heating. In addition, the jet flows back to form a cool recirculation region, which reduces the difference in temperature between the surface and the nearby gas, and thus reduces the heat flux. The larger the total pressure ratio, the lower is the aerodynamic heating. To study the effect of the intensity of the opposing jet more appropriately, a new parameter RPA is defined by combining the flux and the total pressure ratio. The study shows that the same shock wave position, reattachment point position, peak heat flux position and total heat load can be obtained with the same RPA with different fluxes and total pressure ratios, which means the new ratio parameter may account for the intensity of the opposing jet and be used to analyze its influence on the flow field and total heat load at the nose of a reentry vehicle.

This paper describes a flow visualization experiment over the leeside of a slender tapered wing with a leading edge sweepback angle of 65° and a biconvex section. By using laser vapor screen, schlieren and oil flow techniques, the test was carried out at Mach numbers of 1.10, 1.53, 2.53, 3.01 and 4.01 for angles of attack from 5° through 25°. And photos of flow off body and on lee surface have been taken. The vapor screen photos show seven distinct types of flow developed over the delta region of the wing. These types of flow are displayed in a plane of Mach number and angle of attack normal to the leading edge. In the region of the side edge there are side vortices formed and in the region of the trailing edge trailing vortices shed. The variations of both the bow shock positions at different Mach numbers and the positions of separating lines induced by shock waves with Mach numbers and angles of attack are obtained based upon the schlieren plus the vapor screen photos in the sections. The oil flow visualization shows clearly primary reattachment, secondary separation, secondary reattachment lines and side edge vortices on the lee surface. The results of this test are in good agreement with experiments and numerical simulations of others.

The theory of multiple input-output frequency response functions estimation is studied based on the finite Fourier transform. Several possible input signal types are discussed. Of them, the deterministic signal excitation is a new technique which is adrantageous over the currently prevailing random exci tation in test time, the amount of data required to be sampled and reduced and the estimation accuracy. Moreover, the hardware requirement is simpler and it is possible to run with a dual-channel FFT analyser only.In light of the theory, a software package for 6 input-multiple output FRF estimation has been developed, running in the PDP11/23 mini computer system with 64K bytes memory. The operator is prompted to select one from 4 excitation types, （ 1 ）. deterministic, （ 2 ）. periodic random, （ 3 ）. burst random, and（ 4 ）. continuous random excitation. The package was used for real structures such as a free-free beam and a helecopter tail rotor. The results show that the deterministic excitation technique was the best.

On the basis of N(S-S 0) m=C , according to the maximum likelihood principle, the formulas of P S N curves are presented which were determined by the single spot method, the single spot group method and the group method.The comparative test was made, and the test data are analyzed and treated. It was found that the P S N curves determined by these three methods were approximate.By means of the single spot method,many specimens may be saved, so the single spot method may be used to determine the P S N curves of the structure components.

Cannibalization policy is an effective approach to improve support effectiveness. Under the current support condition, it can make equipment availability reach the upper limit. This paper establishs respectively availability models of a non-cannibalization system, a cannibalization system and a partial cannibalization system under the mode of multi-echelon maintenance supply in accordance with the characteristics of cannibalization combined with multi-echelon technique for recoverable item control(METRIC) theory. The analysis flow and method of support effectiveness are studied. In a given example, The initial spare parts inventory project is obtained under which the equipment availability is analyzed with different cannibalization policies. VMETRIC simulation is used to test the results, and the verification shows that there is high consistency between the two results, which proves the validity of the model.