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ISSN 2096-1642

Selected ArticlesMore+

Issue on Theory and Application of Advanced Engines
Dynamic Response Characteristics of Oblique Detonation Waves in Non-Uniform Inflows
TENG Hong-hui, NIU Shu-zhen, YANG Peng-fei, ZHOU Lin, WANG Kuan-liang
2023, 8(5): 1-9.   doi: 10.19527/j.cnki.2096-1642.1033
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Abstract:
In propulsion systems based on oblique detonation waves (ODWs), the airflow compressed by the inlet still has a very high velocity and the complete mixing of fuel and airflow is unattainable, which thus has a huge effect on wave systems of oblique detonations. In this paper, the ODWs in non-uniform inflows were considered as the object. By means of the evolutions of wave angles and displacement distances of wave front, the disturbance characteristics of ODWs were studied using the Euler equations coupled with the hydrogen-air detailed reaction model. The equivalence ratio was chosen as the representation variable of nonuniformity, and a disturbance region with a varying height was introduced into the incoming flow. The symbol φA was defined as the disturbance amplitude and the equivalence ratio distribution in the disturbance region was modeled using the sinusoidal function. It is found that with the decrease of φA, the wave angle decreases and the wave front moves downstream, the opposite trend is observed when the equivalence ratio increases. When φA is negative and small enough, a novel phenomenon characterized by the abrupt change of wave angle can be observed. Further analyses show that this phenomenon is due to ODW re-initiation under the influence of non-uniform equivalent ratio. When φA is posi-tive and large enough, the ODW angle of the disturbance region is in a non-equilibrium state. A larger equivalence ratio gradient results in a higher value than the theoretical wave front angle, while a smaller equivalent ratio gradient has a lower value than the theoretical one. Quantitative analyses of wave front positions show that the displacement distance of the wave front with φA is nonlinear when φA is positive, and linear when φA is negative. Meanwhile, the displacement distance is linear with the height of the disturbance region.
Issue on Flow Stability and Transition
Progress on Prediction Models for Crossflow Instabilities Dominated Transition Based on Local Variables
XU Jia-kuan, DUAN Yi, YANG Jia-sheng, QIAO Lei, LIU Jian-xin, BAI Jun-qiang
2023, 8(3): 19-34.   doi: 10.19527/j.cnki.2096-1642.1012
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Abstract:
Boundary layer transition prediction has always been a hot and difficult research topic in the field of fluid mechanics. Among them, the crossflow induced transition plays a crucial role in the transition phenomenon on the surface of the aircraft, which is affected by the freestream disturbance, wall surface roughness, wall pressure gradient, local sweep angle, crossflow characteristic Reynolds number, Mach number, wall curvature and temperature. All those factors make the prediction of the cross-flow transition very complicated and difficult. In recent years, many research institutions have proposed various prediction methods for this problem, which are basically divided into two categories: one is to establish the critical transition Reynolds number criterion, and to determine whether transition occurs; the other type is the modeled linear stability theory, which calculates the cross-flow disturbance amplification factor and compares it with the transition threshold to determine whether transition occurs. Several typical prediction models of crossflow dominated transition based on local variables of low-speed boundary layer and high-speed boundary will be systematically reviewed and summarized, and the future research directions will be prospected.
Research Paper
Reliability of the eN Method Applied to Hypersonic Blunt Cone Boundary Layers for Transition Prediction
YANG Xiao-nan, SU Cai-hong
2023, 8(2): 44-55.   doi: 10.19527/j.cnki.2096-1642.0987
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Abstract:
The eN method predicts transition based on the level of the linear amplitude amplification of the disturbances in the boundary layer. Boundary layers over cones at Mach 6 were investigated with different nose bluntness and under different wall temperature conditions. Combined with direct numerical simulation (DNS) and parabolized stability equations (PSE), from the viewpoint whether the eN method is able to accurately describe the amplification of the disturbances in the above boundary layers, its reliability for transition prediction was interrogated. Results show that in the cases of small bluntness or high wall temperature, the disturbances undergo the intermodal exchange from the first mode to the second mode when travelling downstream in the boundary layer, so that the eN method based on linear stability theory becomes less reliable. Under the same wall temperature condition, as the nose bluntness increases, the eN method is more reliable. For the same nose bluntness, as the wall temperature decreases, the eN method is more reliable. Since linear stability theory always underestimates the amplification of the disturbances when there is an intermodal exchange, for the given transition criterion NT, which could be calibrated by a certain case, as the bluntness decreases or the wall temperature increases to some extent, the eN method tends to produce a further downstream transition location than reality. To recalibrate the transition criterion, the smaller the nose bluntness or the higher the wall temperature, the larger the modification of NT factor.
Flow Characteristics of Dual Throat Thrust Vectoring Nozzles
HE Jingyu, YANG Zhichen, LIANG Wenxin, OU Ping, DONG Jingang
 doi: 10.19527/j.cnki.2096-1642.1101
14 0
Abstract:
The investigation was conducted to investigate the flow characteristics on the dual throat thrust vectoring nozzle. Based on a simplified aircraft afterbody model, the numerical calculation and the wind tunnel test were carried out to study the effect of the integrated design of aircraft afterbody on the flow characteristics. The impact of the main flow/vectoring jet flow interaction on the aircraft afterbody was further investigated. The results indicate that, the difference between the upside and downside wall pressures is the main reason for the generation of thrust vectoring, and this difference is created by the separated turbulent flows in the cavity. The wall pressure difference increases with the enhancement of the secondary injection flow rate. Then the thrust vector angle of nozzle increases. The thrust vector angle reach the peak value 16.6° with- out outflow at the conditions that the primary NPR=4.0 and the secondary NPRs=4.8. While the peak thrust vector angle is 11.2° with outflow Ma=0.4. The dominant frequency of noise created from the nozzle cowl is within 900 Hz. The peak noise is located at the cowl configuration which changes sharply. The variation of the vectoring jet angle has no effect on the peak noise frequency, but only affects the amplitude below 1 000 Hz on the downside of nozzle cowl, and the influence of the maximum frequency spectrum amplitude is 2 dB.
Numerical Simulation of Flow and Aerodynamic Heating of a Thermal-Protection Ring of Plate/Rudder Shaft
DOU Yibin, CHEN Junming, SHI Xiao, LIU Luguang, LU Yunchao, LI Zongyang, ZHAO Ruyi
 doi: 10.19527/j.cnki.2096-1642.1109
11 0
Abstract:
Influenced by the local angle of attack of the air rudder, a complex separation and reattachment flow will form at the position of the full-motion rudder shaft thermal-protection ring during a hypersonic flight, accompanied by severe aerodynamic heating loads, which is the weak link in the thermal protection design of the air rudder. Taking the flat plate/air rudder shaft thermal-protection ring as the research object, the numerical calculation method was used to study the influence rule of different rudder deflection angles and geometric parameters of the thermal-protection ring's annular gap on the flow and aerodynamic heating. The numerical calculation was based on the unstructured hybird gird finite volume method. The calculation results and analysis show that the rudder deflection has the greatest effect on the heat flux distribution in the thermal-protection ring. Under the condition of rudder deflection, a reattached flow and high flux region will form at the chamfer of the thermal-protection ring. The area of the high flux region and the flux peak are proportional to the rudder deflection angle. When the rudder deflection angle equals 0°, the airflow at the Z=0 mm cross-section of the annular gap will flow upward into the gap at the bottom of the rudder surface. When the rudder deflection angle is greater than 0°, the incoming flow in the gap at the bottom of the rudder surface will form a vortex in front of the chamfer of the thermal-protection ring, and at the same time the airflow on the flat plate enters the annular gap downward and forms a vortex in the direction of the gap depth. When the rudder deflection angle and the gap width are fixed, the gap depth mainly affects the heat flux at the chamfer of the thermal-protection ring and the annular gap windward side. As the gap depth increases, the flow structure at the Z=0 mm cross-section of the annular gap develps from 2 vortices to 3 vortices. When the rudder deflection angle and the gap depth are fixed, the gap width mainly affects the heat flux at the annular gap windward side. As the gap width increases, the vortex at the Z=0 mm cross-section of the annular gap develops more fully, and the flow structure in the depth direction develops from 3 vortices to 2 main vortices and 2 small vortices at the bottom of the annual gap.
Numerical Simulation of Finite-Rate Catalytic Model Based on ReaxFF-MD
SONG Jiahao, MO Fan, GAO Zhenxun
 doi: 10.19527/j.cnki.2096-1642.1110
10 0
Abstract:
At present, when CFD method is used to predict surface heat flux, it is generally assumed that the wall condition is full-catalytic wall or non-catalytic wall. Heat flux prediction can be greatly affected by different wall catalytic conditions, and a more reasonable numerical solution can be obtained by using finite-rate catalytic model. However, due to the nonlinear, nonequilibrium, and multiscale characteristics of the catalytic recombination process of high-enthalpy chemical reaction flows on material surfaces, it is extremely difficult to accurately describe the finite-rate catalytic model. In this paper, a finite-rate catalytic model describing the interaction of O and N atoms with SiO2 surface was constructed by ReaxFFmolecular dynamics method based on the theory and simulation at the microscale. The reentry flow fields of space shuttle orbiter under different catalytic conditions were calculated and compared. The results show that the predicted heat flux of the finite-rate catalytic model agrees well with the flight test data of STS-3 in the altitude range of 70.1 km to 57.8 km, and the model has a certain degree of accuracy.
Numerical Study on Factors Affecting the Storage Tank Performance of an Iodine-ion Thruster
CHEN Mingshi, WANG Xian
 doi: 10.19527/j.cnki.2096-1642.1097
29 3
Abstract:
Iodine-ion thrusters are mainly used for attitude control and position maintenance of small satellites. They rely on the sublimation and ionization of iodine to generate thrust. The heating methods and structural parameters of the iodine feeding systems have a significant impact on their own working performance. The dynamic grid method was applied to simulate the sublimation phase-transition process of the iodine in the storage tank to study the effects of heating methods and ratios of diameter to height on the performance of storage tank of an iodine-ion thruster. The results indicate that the contact heating method shows the best performance considering the mass flow rate, flow stability, and preheating time among the three heating methods, such as external heating, radiant heating, and contact heating. Besides, the ratio of diameter to height of a storage tank has almost no effect on the change of flow rate for the contact heating method. The flow stability is good. A lower ratio of diameter to height is better for the iodine-ion thruster designed for high thrust. The mass flow rate at the ratio of 0.2 increased by 9.0% compared to the ratio of 1.4. While a larger ratio of diameter to height is better for the iodine-ion thruster designed for high speed of response. The preheating time at the ratio of 0.2 increased by 80% compared to the ratio of 1.4.
Summary and Prospect of Data-Driven Aerothermal Modeling Prediction Methods
WANG Ze, SONG Shufang, WANG Xu, ZHANG Weiwei
 doi: 10.19527/j.cnki.2096-1642.1068
57 17
Abstract:
The accurate prediction of aerothermal loads is the basis to guide hypersonic vehicle design. Under the back- ground that classical aerothermal prediction methods are more and more difficult to meet the demand of efficient and accurate aerothermal prediction in engineering, data-driven aerothermal modeling prediction methods have gradually become a new paradigm of aerothermal prediction in recent years. Firstly, the relationship between the data-driven aerothermal modeling prediction method and the classical aerothermal prediction method was described. Then, from the modeling idea, the data-driven aerothermal modeling prediction methods were summarized into three categories:The dimensionality reduction modeling method of feature space, pointwise modeling method and physical information embedding modeling method were introduced and analyzed in detail. It is found that the data-driven aerothermal modeling prediction method is not only more accurate than the engineering algorithm, but also can effectively reduce the workload of test measurement and numerical calculation when combined with the sampling method, and the model given is more efficient and concise. Finally, the develop- ment trend of data-driven aerothermal modeling prediction methods was prospected. It is pointed out that the deep combination of data-driven technology and classical aerothermal prediction methods, aerothermal physical information embedding modeling methods and aerothermal prediction big models will be the key points of future research.
Efficient Flow Field Reconstruction Based on Ensemble Transform Kalman Filter
GUO Yuxin, HUANG Jun, ZHAO Qingyu, JI Jingjing, HUANG Yongan
 doi: 10.19527/j.cnki.2096-1642.1090
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Abstract:
Accurate estimation of turbulence field is of great importance in aerospace, and existing means of obtaining turbulence field is inadequate in terms of resolution or accuracy. Experimental measurements are accurate but often have a limited number of observation points, and numerical computations can obtain full-field data but the accuracy is difficult to guarantee. The data assimilation method integrates experimental observation and numerical simulation, which is an effective tool for flow field reconstruction. This paper explored the effectiveness of data assimilation method based on ensemble transform Kalman filter(ETKF) in spatial flow field reconstruction, and also discussed the reconstruction accuracy and computational efficiency of different iterative updates, namely ETKF-M and ETKF-D, which update state variables based on turbulence model and flow field data respectively. Using the ONERA M6 airfoil as a numerical example, the algorithm was experimented by combining the pressure measurement data from 271 pressure holes on the airfoil surface from the wind tunnel test. The results show that different iterative updates of ETKF method can effectively modify the prediction of the turbulence model, and the ETKF-D improves the computational efficiency by 83% compared with the ETKF-M. In addition, two groups of 1/4 experimental observation points at different locations were selected for assimilation experiments, and results with different accuracies were obtained. It indicates that the accuracy of reconstruction is closely related to the location and number of assimilated observation points.
Accuracy of MUSCL and WENO Schemes On Non-Uniform Structured Meshes
LIU Jun, LIU Yu
 doi: 10.19527/j.cnki.2096-1642.1079
30 7
Abstract:
The difference schemes constructed on the basis of one-dimensional uniform grids must be extended to non-uniform or curvilinear grids in practical applications, and the coordinate transformation process introduces geometry-induced errors. The accuracy of the difference schemes is evaluated by the accuracy test, in which the convergence solution error varies with the grid refinement. In this paper, the first-order upwind scheme, the second-order MUSCL scheme and the fifth-order WENO scheme were used to calculate the uniform free flow problem with constant flow parameters on a two-dimensional cylindrical coordinate uniform grid system, and the slope of the convergence curve was compared according to the ac- curacy test method, and it was found that the grid convergence accuracy of the first-order upwind scheme was second order, and the grid convergence accuracy of the fifth-order WENO scheme was less than first order. Theoretical analysis shows that this accuracy test method is not equivalent to the definition of difference scheme accuracy, and the data used cannot reflect the inherent defects of the difference scheme. Therefore, it cannot be used as a criterion for evaluating the accuracy of the difference scheme. Many studies of WENO schemes often simulate benchmarks such as the double Mach reflection problem and the two-dimensional Riemann problem, and use whether the contact discontinuity develops into an unstable vortex structure as a characteristic of the algorithm with high accuracy, which can be theoretically proved to be a non-physical phenomenon, so it is not appropriate to use whether a vortex structure appears as an argument for the algorithm's high accuracy.
Scale Interactions of Turbulent Boundary Layer Flows Under Local Dynamic Wall Disturbance
ZHANG Yu, TANG Zhan-qi, CUI Xiao-tong, JIANG Nan
 doi: 10.19527/j.cnki.2096-1642.1099
19 2
Abstract:
This paper analysed the relationships between various scales by considering the condition of the upstream flow fields. The feasibility of flow control for drag reduction through intermittent energy input from active drag reduction systems was discussed. In the experiment, a piezoelectric oscillator was used to impose local disturbances on a turbulent boundary layer. Flow field information was collected using fixed probes upstream of the piezoelectric oscillator and moving probes downstream (moving along the wall-normal direction). Correlation analyses were performed on velocity signals of different scales both upstream and downstream of the piezoelectric oscillator to determine their spatiotemporal relationships. Distur- bance signals and their higher-order harmonics were identified through the pre-multiplied energy spectrum, and different signal scales were categorized. The interactions between large scales and disturbance scales, as well as between disturbance scales and small scales, were particularly discussed under large-scale high-speed/low-speed inflow backgrounds. It is ob- served that the large-scale high-speed background modulates the disturbance signals. Under both large-scale high-speed and low-speed inflow backgrounds, there exists a fixed phase correspondence between the disturbance signals and small-scale signals, which remains unaffected by the inflow background. It is explicitly stated that when actively controlling the flow field intermittently using a piezoelectric oscillator, it is advisable to operate under a large-scale high-speed inflow back- ground.
Cover and contents of Vol.9 No.2
2024, 9(2): .  
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Heat Transfer Characteristics of Gap Flows in Shock-Wave Interference Region of Hypersonic Vehicles
LI Zongyang, DOU Yibin, REN Zhiyi, LU Yunchao, CHEN Junming
2024, 9(2): 1-8.   doi: 10.19527/j.cnki.2096-1642.1100
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Effects of Mach Number and Wall Temperature on HyTRV Boundary Layer Transition
ZHANG Luxing, WANG Guangxue, DU Lei, YU Fayuan, ZHANG Huaibao
2024, 9(2): 9-20.   doi: 10.19527/j.cnki.2096-1642.1098
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Rotating Detonation Combustion Characteristics of Kerosene-Fueled Wide-Area Scramjets
SHU Chen, GU Futao, CHEN Bin, YAN Chenglong, TONG Yiheng, LIN Wei
2024, 9(2): 21-32.   doi: 10.19527/j.cnki.2096-1642.1082
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A Simplified Neural Network Model for Compressible Two-Gas Flows
LIU Ziyan, XU Liang, LIU Yaofeng
2024, 9(2): 33-42.   doi: 10.19527/j.cnki.2096-1642.1089
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Aerodynamic Modeling and Path Optimization of Wing Docking Process for Fixed-Wing UAVs
CHEN Yiwei, LIU Haojie, HUANG Rui, GAO Xiumin
2024, 9(2): 43-53.   doi: 10.19527/j.cnki.2096-1642.1084
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Wing Design and Adaptive Optimization of a Compound Drone
ZHANG Wei, TAN Meng, LIU Yafeng, NIE Yongbin, LUAN Yue
2024, 9(2): 54-65.   doi: 10.19527/j.cnki.2096-1642.1091
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Effect of Wavy Wall on the Stability of Conical Hypersonic Boundary Layer at Small Angle of Attack
ZHANG Chengjian, GUI Yuteng, LI Xueliang, CHENG Jiangyi, WU Jie
2024, 9(2): 66-80.   doi: 10.19527/j.cnki.2096-1642.1078
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