Frequent extreme wind events in China's coastal regions pose severe challenges to the aerodynamic performance of high-speed trains passing through tunnel portals under strong winds. To reveal the distribution patterns of bay winds at coastal high-speed railway tunnel portals and enhance the operational safety of high-speed trains, this study systematically investigates the bay wind effects and train aerodynamic responses by combining the RNG k-ε turbulence model with the sliding mesh technique. A computational fluid dynamics (CFD) prediction model, based on actual terrain and a high-speed railway tunnel section, is established to dynamically simulate the entire process of a high-speed train passing through the tunnel portal under a crosswind of 20 m/s at a train speed of 350 km/h. The model incorporates the influences of both the oblique-cut tunnel portal and the embankment topography on train aerodynamic performance, and covers twelve incoming wind direction angles (ranging from 0° to 330° at 30° intervals). Based on the research findings regarding the mountainous flow field and train aerodynamic loads, it is found that under incoming flow with wind direction angles of 90° (due west) and 270° (due east), the flow acceleration induced by the mountain slope results in the maximum average wind speed at the tunnel portal, which increases by 26.5% and 29.0% compared to the incoming wind speed, reaching 25.3 m/s and 25.8 m/s, respectively. Conversely, at wind direction angles of 120° and 150°, the terrain blocking effect is most pronounced, reducing the portal average wind speed by 56.5% and 51.5%, corresponding to values of 11.3 m/s and 10.3 m/s. When the train passes through the tunnel portal section, the aerodynamic loads fluctuate drastically, and the fluctuation amplitude of the head car is significantly higher than those of the middle and tail cars, being 1.34–4.34 times that of the middle car and 2.27–5.66 times that of the tail car. Further analysis reveals a significant positive correlation between embankment height and the fluctuation amplitude of train aerodynamic loads, which can be well described by a linear function with a coefficient of determination (R2) above 0.89. This research can provide a solid theoretical basis and engineering guidance for the route selection and wind-resistant design of high-speed railways in coastal areas.
To investigate the aerodynamic interference caused by tanker wake on helicopter during aerial refueling, a numerical simulation method for the coupled flow field of tanker and helicopter based on the Reynolds-Averaged Navier-Stokes (RANS) equations is developed. The A400M transport aircraft and UH-60A helicopter are used as research subjects to analyze the characteristics of the isolated tanker wake and the coupled helicopter/tanker flow field. Results show that the tanker wake primarily consists of rotating tip vortex, inner propeller slipstreams, fuselage wake, and horizontal tail wake, forming a highly unsteady and strong vertical velocity field behind the tanker fuselage. Notably, lateral offset maneuvers can effectively reduce the turbulence intensity of the wake. The wake-induced upwash leads to an overall increase in the rotor thrust coefficient by approximately 2.5% to 4.4%, accompanied by pronounced fluctuations compared to baseline conditions. Meanwhile, the moments of the rotor and tail rotor increase markedly. As the rotor moves laterally toward the docking position, the unsteady disturbances intensify, resulting in more significant thrust oscillations (originally “tension oscillations”). During the standard aerial refueling procedure, the helicopter can generally avoid the strong wake interference area during the traverse phase, with minimal changes observed in both the thrust coefficient amplitude and the rotor thrust distribution. However, at the docking position the influence of the wake amplifies vortex energy within the tip vortex, causing a notable enlargement of the vortex structures. Within the rotor disk region, the tip vortex tubes become increasingly deformed and broken. Furthermore, the vortex distribution between the front and rear rotor blades shows asymmetry, with the front blade vortex slightly stronger and tending to spread downward. Under the full-configuration simulation conditions, the large rotor tilt angle limits the fuselage’s effect on the surrounding flow field. Meanwhile, the presence of tail rotor vortex increases turbulence beneath and behind the fuselage. Compared to the baseline state, the rotor thrust distribution changes significantly: thrust on the forward side of the rotor blades increases sharply, and the tip vortex deformation leads to negative thrust zones appearing near the blade tips. Wake-induced turbulence generates high pressure around the helicopter nose, reducing the fore fuselage pitching moment by about 60% and causing pronounced high-frequency oscillations. This dynamic behavior can adversely affect the helicopter pitch stability during docking maneuvers. The wake decreases torques on the receiver hose by roughly 95% and 88% in the longitudinal and lateral directions (originally “structural loads”). However, the cyclically alternating torque fluctuation may accelerate fatigue damage. Simultaneously, the wake increases the vertical torque amplitude on the receiver hose by approximately 20%, which may raise the risk of oscillatory deformation along this direction.
Wind tunnel test is a crucial means for evaluating the low sonic boom characteristics of supersonic civil aircraft and validating related design prediction methods. Investigating the influence of wind tunnel background pressure (WBP) on sonic boom measurement and developing suppression techniques are essential for establishing reliable wind tunnel test methodologies for sonic boom measurement. This study focuses on the unique spatiotemporal distribution and coupling characteristics of WBP. Through theoretical analysis and experimental verification, the mechanism of its influence on sonic boom measurement is explored. The independent effects of WBP distribution in the time and spatial domains under approximate decoupling conditions are successfully revealed. A fine-control strategy for the settling chamber total pressure is proposed, which employs a composite control method combining feedforward and PID feedback to suppress temporal influences. This strategy improves the total pressure control accuracy from 0.2%～0.3% to better than 0.15%, significantly reducing the temporal non-uniformity of WBP. By integrating specific test arrangements, selecting the region with minimal fluctuations as the test section and applying spatial averaging data processing, a comprehensive strategy is formed. This effectively enhances the ability to distinguish and extract weak sonic boom signals in environments with high spatial disturbances. Applying this methodology to low sonic boom supersonic civil aircraft benchmark model tests in a 2 m supersonic wind tunnel shows that the near-field sonic boom measurement results are in good agreement with those obtained from continuous wind tunnels of similar scale internationally. The deviation of the head shock peak is less than 3%, validating the effectiveness of the proposed framework in mitigating the influence of wind tunnel background pressure on sonic boom measurement.
Mesoscale eddies play a central role in ocean dynamics and material transport, with their rotational structures exerting significant regulatory effects on water exchange and transport processes. Based on high-resolution numerical simulations combined with curvature vorticity diagnostics, this study analyzes the dynamic evolution of cyclonic and anticyclonic eddies and their influence on water exchange. The results show that eddies form stable, closed circulation structures at the surface, effectively “trapping” water masses and significantly prolonging their exposure time. Meanwhile, the distribution of exposure time exhibits strong vertical dependence, with the spatial distribution evolving from a near-circular pattern at the surface to a more concentrated and asymmetric structure in the middle and bottom layers. At the eddy periphery, central Ekman suction and enhanced mixing jointly maintain both the enclosed nature of the eddy and the exchange activity along its boundary. Curvature vorticity diagnostics reveal that while the rotational structure strongly influences the distribution of exposure time, the dynamic evolution of cyclonic and anticyclonic eddies differs markedly. The early stage of anticyclonic eddy formation is dominated by the banking term, transitioning to dominance by the stretching term during the stable phase. In contrast, cyclonic eddies enter the unstable stage earlier, with their development mainly controlled by transport term and vortex stretching.
Predicting the morphological evolution of porous media under coupled thermo-fluid-solid-chemical processes remains a common challenge in aerospace, energy, chemical engineering, and many other fields. In this study, a hybrid micro-continuum-scale numerical method is proposed. Taking the oxidation ablation of a three-dimensional carbon fiber porous material exposed to a high-temperature oxygen flow as an example, a structured grid is employed to achieve coupled simulations of fluid flow, heat transfer, chemical reactions, and dynamic morphology evolution. The result indicate that porosity determines the ablation mode of the material. For low-porosity structures, ablation is dominated by surface oxidation recession, whereas high-porosity structures also experience volumetric ablation due to deeper oxygen penetration. Quantitative analysis reveals a positive correlation between the porosity and the mass loss rate of carbon fiber porous materials. After 20 s of ablation, the mass loss rates for materials with porosities of 0.92 and 0.88 reach as high as 100% and 99.3%, respectively; in contrast, when ε = 0.85, the mass loss rate decreases significantly to approximately 74.5%. Furthermore, constrained by the diffusion limit caused by an insufficient oxygen supply, the ablation recession rate at 3000 K exhibits a nonlinear behavior over time, increasing initially and then decreasing. The proposed method is capable of accurately capturing the dynamic evolution of ablation morphology in three-dimensional space and at the pore scale, providing an effective numerical tool for evaluating the ablation resistance of porous media under extreme environments.
Surface roughness significantly affects the aerodynamic and thermal characteristics of high-speed vehicles, and reducing surface roughness is an effective approach for drag reduction and thermal protection. To maximize the drag and heat flux reduction benefits of smooth areas under the constraint of limited surface treatment area, the direct simulation Monte Carlo method was employed to simulate the transition flow regime for two typical geometries: a plate and a blunted cone with distributed smooth strips. The accommodation coefficient of the smooth surface was obtained via molecular dynamics simulations, while the completely diffuse reflection model was used to represent the conventional rough regions. In this manner, the surface characteristics corresponding to the lower and upper bounds of roughness were characterized, and spatially nonuniform accommodation-coefficient boundary conditions were established to investigate the mechanisms underlying the effects of the spatial distribution of surface roughness on the aerodynamic characteristics of the vehicle. The results show that smooth strips can induce the redevelopment of the boundary-layer flow over the vehicle surface, resulting in friction and heat-flux losses or abrupt changes in the transition regions between smooth and rough surfaces. For small regions, such as the vehicle nose and leading edge, where skin friction increases, multiple continuous or discrete smooth strips should be distributed in the central part of the local region to fully exploit the friction and heat-flux losses associated with the transition regions. For large regions, such as the vehicle body, where skin friction and heat flux decrease, the smooth strips should be arranged continuously in the downstream part of the local region when the local flow angle of attack is relatively large, thereby minimizing abrupt changes in friction and heat flux across the transition regions. Conversely, when the local flow angle of attack is relatively small, the smooth strips should be arranged continuously in the upstream part of the local region. At a strip coverage ratio of 50%, the continuous mid-region arrangement (D4) and the discrete interleaved arrangement (D7) on the flat plate exhibit comparable reductions of approximately 13%–15% in both skin friction and heat flux. For the blunted cone, the continuous rear-region arrangement (D5) yields the best performance, achieving a total drag reduction of about 12%. This study provides a theoretical basis and numerical reference for the spatial layout design of polished regions on high-speed vehicle surfaces.
Targeting the pronounced non-equilibrium characteristics of high-speed flows, this study conducted numerical simulations of typical high-speed flows based on the joint hydrodynamics–particle (JHP) method. The method employed stochastic particles to describe collisionless transport, and a competition mechanism was introduced within an integral solution framework through the coupling of the cell-averaged collision time and the global time step. This enabled a unified coupling between the macroscopic Navier–Stokes (N-S) equations and mesoscopic particle transport, allowing accurate resolution of locally strong non-equilibrium features. To validate the applicability of the method for high-speed non-equilibrium flows, three benchmark cases were selected: a one-dimensional shock structure and a high-speed flow over a circular cylinder at Mach 20, as well as a high-speed blunt-wedge flow at Mach 5. Comparisons with the unified gas-kinetic scheme (UGKS) and the unified gas-kinetic wave–particle (UGKWP) method demonstrated that the JHP method achieves high accuracy in predicting macroscopic quantities, including temperature and velocity distributions, as well as overall flow structures. Further comparisons with N-S solutions, combined with local Knudsen number analysis, revealed the spatial distribution of non-equilibrium regions within the flow field. Compared with conventional macroscopic approaches, the JHP method more accurately captures flow features in regions with strong non-equilibrium effects, such as the shock layer, near-wall region, and wake. These results indicate that non-equilibrium effects in high-speed flows exhibit pronounced spatial heterogeneity and significantly influence flow evolution. In the blunt wedge flow case, the computational time of the JHP method is approximately 37.9% of that of the reference method (IUGKS), and its memory consumption is about 2.5%, indicating that the method provides an efficient and high-fidelity approach for the simulation of hypersonic non-equilibrium flows.
In Cartesian grid methods,the non-body-fitted nature between orthogonal grids and complex solid boundaries poses a significant challenge for accurately imposing boundary conditions,which directly impacts simulation accuracy.The proposed method addresses this by locating reference points along the outward normal direction of the boundary surface,applying bilinear interpolation to obtain the flow variables at those points,and incorporating local curvature information to extrapolate physical quantities.This approach enables accurate reconstruction of flow variables in virtual cells near the boundary,particularly enhancing accuracy in regions with high curvature.Validation on multiple benchmark cases demonstrates a substantial reduction in boundary-induced errors,with errors in the L1,L2 and L∞ norms decreasing by approximately an order of magnitude.The overall method retains second-order convergence and effectively suppresses spurious entropy generation in regions of high curvature,offering a reliable and efficient boundary treatment for Cartesian-grid CFD simulations of complex geometries.
稀薄气体动力学是空气动力学的重要分支,以克努森数表征流动稀薄程度,聚焦从连续流至自由分子流全域非平衡输运、气固相互作用及多物理耦合等核心科学问题.当气体分子平均自由程与流动特征长度可比时,连续介质假设失效,经典 Navier-Stokes(N-S)方程难以准确描述流动,Boltzmann方程成为刻画稀薄气体非平衡输运的基本方程.自 1946年钱学森先生发表关于稀薄气体中高速绕流问题的开创性论文以来,稀薄气体动力学因高速飞行器再入、临近空间长时巡航、微机电系统及超低轨卫星等尖端工程需求而持续受到关注,并逐渐发展成为支撑国家空天战略装备研发的基础力学分支之一.
The immersed boundary method (IBM) is widely used for incompressible flows with complex geometric boundaries. Among its variants, the direct forcing method is computationally and programmatically straightforward and effectively captures near-wall flow behavior. However, it struggles to maintain the divergence-free condition of the velocity field in unsteady incompressible flows. To address this issue, this paper proposed a data-driven velocity reconstruction approach for the immersed boundary method (DATA-I). By improving dataset construction and training methodologies, the method captures the nonlinear relationships of near-wall velocities, thereby preserving the divergence-free property in numerical simulations of incompressible flows. To validate the effectiveness of the proposed method, numerical simulations of two-dimensional flow around a circular cylinder at Reynolds numbers ranging from 40 to 500 were conducted. Additionally, the geometric generalization capability of the data-driven model was tested using flow cases around a square cylinder and a sharp wedge. In the steady flow past a circular cylinder, the method reduced divergence errors by 44.7% to 70.4% compared to traditional interpolation approaches. For unsteady cylinder flow, the Strouhal number error was controlled within 5%. This study offers a novel solution for accurately simulating near-wall flows in incompressible fluid dynamics using the IBM.
High-speed boundary layer transition directly affects the aerodynamic force and aerodynamic design of high-speed vehicles, yet the physical mechanisms by which local wall temperature variations act upon boundary layer instability, particularly the quantitative effects of tip temperature on the nonlinear evolution of second-mode instability waves and the resulting transition location, remain insufficiently understood through systematic experiments. In this study, experiments were conducted in a Mach 6 Ludwieg tube wind tunnel using a 7° half-angle sharp cone model at zero angle of attack, with high-frequency pressure sensors, a high-speed infrared camera, and a focused laser differential interferometer employed for measurements. The experimental results indicate that when the region of tip temperature variation is located upstream of the synchronization point, cooling the cone tip (to 240 K) enhances the nonlinear interaction of the second-mode instability waves, increasing the critical layer height within the boundary layer by 25% and the maximum amplitude by 79%–88%, while delaying the transition location from 340 mm to 340–360 mm. Conversely, heating the cone tip (to 330 K) suppresses the nonlinear interaction, reducing the critical layer height by 25% and the maximum amplitude by 13%–32%, with the transition location advancing to 313–340 mm. Infrared measurements further demonstrate that tip cooling reduces the surface temperature difference at transition, whereas tip heating produces the opposite effect. This study provides quantitative data support for the thermal protection and aerodynamic design of high-speed vehicles.
Helicopter rotor noise remains a critical barrier to the wider adoption of rotary-wing aircraft. This study aims to identify and quantify the principal aerodynamic noise sources of helicopter rotors, evaluate state-of-the-art high-fidelity prediction techniques for coupled flow-acoustic fields, and develop an integrated active control framework capable of delivering robust noise reduction across multiple flight regimes. First, the research systematically examines four dominant noise mechanisms: thickness noise generated by the unsteady displacement of rotor blades, loading noise arising from time-varying aerodynamic forces, blade/vortex interaction (BVI) noise caused by shed vortices impinging on subsequent blades, and high-speed impulsive (HSI) noise associated with transonic flow on advancing blades. Each mechanism is characterized in terms of spectral content, directivity pattern, and sensitivity to rotor parameters such as advance ratio, collective pitch, and tip Mach number. Next, the evolution of prediction methodologies is reviewed, including Reynolds-averaged Navier-Stokes (RANS) solvers coupled with acoustic analogies, hybrid large-eddy simulation (LES) approaches, and fully coupled computational aeroacoustics (CAA) frameworks. The comparative strengths and limitations of these methods are highlighted, with particular attention to accuracy in capturing unsteady flow features and computational costs. Building on this foundation, the study introduces a classification of active noise control (ANC) schemes according to their deployment mode. Two principal categories are defined: (a) onboard platform-based systems, which integrate sensors and actuators directly on the rotor hub or blade surfaces, and (b) ground-assisted approaches employing fixed or mobile ground stations to generate counter-noise fields or adaptive inflow conditions. Each category is assessed regarding the noise-suppression efficiency, bandwidth of operation, power requirements, and feasibility of retrofitting onto existing airframes. To address the multi-objective nature of rotorcraft performance, an active aerodynamic noise control strategy is proposed. This approach synergizes active and passive techniques, implements adaptive multi-objective optimization, and leverages interdisciplinary integration. Specifically, adaptive trailing-edge flaps and trailing-edge serrations are combined with real-time blade pitch modulation to extend the control bandwidth, a multi-objective controller simultaneously minimizes sound pressure levels, fuel consumption, and vibratory loads, and a digital-twin environment fuses real-time flight data with machine-learning algorithms to refine control laws on-the-fly. High-fidelity numerical simulations validated by wind-tunnel experiments demonstrate that the proposed framework achieves up to 8 dB overall sound level reduction in BVI-dominated flight regimes without compromising lift or increasing power draw. Quantitative results indicate a 15 % improvement in acoustic efficiency relative to standalone passive measures and a 10 % reduction in vibratory loads. Finally, the study identifies key avenues for future research: the development of improved acoustic source models that capture nonlinear blade-vortex interactions, optimization of distributed sensor and actuator networks via information-theoretic metrics, and advancement of intelligent control algorithms capable of learning complex flow-noise correlations. Integration with big-data analytics, artificial-intelligence-driven prognostics, and novel lightweight composite materials is also recommended to facilitate real-world implementation. Collectively, these contributions furnish a comprehensive theoretical and technological roadmap for achieving full-condition low-noise helicopter flight.
Multidisciplinary design optimization is a primary approach for advanced aircraft to balance aerodynamic and stealth performance. In recent years, generative adversarial network-based design methods have been developed, yet they suffer from performance-awareness deficiency and scattered performance distribution of generated configurations. To address these issues, this paper introduces a regression model as a performance predictor into the conditional Wasserstein generative adversarial network with gradient penalty (CWGAN-GP), and proposes a generative design framework guided by performance regression, termed guided CWGAN-GP (GCWGAN-GP). This framework establishes a guidance loss based on the deviation between predicted performance and target conditions, thereby enabling performance feedback. A dual-constraint mechanism is constructed, comprising a regression-model-based performance constraint and a discriminator-based geometric constraint. Taking lift and radar cross section (RCS) as target performance metrics, a dataset is built through parametric modeling, the vortex lattice method, and the physical optics method, and aerodynamic/stealth design of a flying-wing configuration with 28-dimensional shape design variables is conducted. Results demonstrate that, through the optimization of multiple training strategies, the GCWGAN-GP framework achieves favorable convergence. Compared with the baseline CWGAN-GP model, the GCWGAN-GP model can stably generate layout schemes with clear and consistent geometric features, while achieving highly concentrated target performance and effectively balancing aerodynamic and stealth performance. The framework realizes performance-oriented data learning and high-performance shape generation, validating its feasibility and superiority in multidisciplinary design optimization of aircraft.
The aerial refueling hose is prone to lateral vibration due to external flow fields and platform maneuvering, which can develop into a whipping phenomenon in severe cases. This complex dynamic behavior, governed by the dynamic characteristics of distributed parameter systems, poses significant challenges to the boundary stabilization control of the hose system and seriously endangers the safety of the aerial docking process. This paper investigates the vibration suppression and boundary stabilization problems of a flexible aerial refueling hose subjected to aerodynamic disturbances by introducing a cleverly designed super-twisting sliding mode control framework. Based on the principle of virtual work, a set of partial differential equations and the associated boundary conditions for the flexible aerial refueling hose are established. By integrating the super-twisting algorithm with a barrier function-based disturbance observer, an innovative finite-time sliding mode controller is proposed. The stability and convergence of the closed-loop system are rigorously proven using Lyapunov theory. Numerical simulation results demonstrate that the proposed control method effectively eliminates hose vibrations. Under constant-velocity motion conditions, the root mean square value of the displacement at the hose tip (x = L) is 0.1672, representing a reduction of approximately 95.3% compared to 3.5264 achieved by an existing boundary control method. At the midpoint of the hose (x = L/2), the root mean square value of the displacement is 1.0063, which is reduced by approximately 17.3% compared to 1.2164 achieved by the proportional-integral-derivative (PID) control method and by approximately 59.5% compared to 2.4857 achieved by the existing boundary control method. Superior vibration suppression performance is thus achieved at different positions along the hose. This study provides a high-performance alternative to PID control, backstepping control, and their derivative methods for distributed parameter systems such as hose-type partial differential equation systems.
Aerodynamic characteristics in rarefied atmospheric environments are one of the key factors influencing the high-altitude aerodynamic braking of orbiters. This paper presents a numerical simulation of ground-based low-density wind tunnel test conditions using the direct simulation Monte Carlo (DSMC) method, within the context of the Martian atmosphere. A six-component micro-force balance measurement system was employed to conduct aerodynamic force tests on an orbiter model in a low-density wind tunnel, and the experimental results were compared with numerical predictions. Furthermore, taking the Martian atmospheric environment as a case study, numerical simulations were performed to analyze the flow characteristics of the orbiter configuration under various degrees of rarefaction, thereby revealing the aerodynamic behavior governing the Martian rarefied environment. The results indicate that high-altitude rarefied gas effects significantly alter the flow field structure around the orbiter. Distinct compression-expansion features are observed at different altitudes, and the flow field contours tend to exhibit a more circular distribution under the influence of rarefaction effects. Under the specified computational conditions, the freestream dynamic pressure is substantially influenced by flight altitude, leading to notable variations in the overall axial force coefficient, normal force coefficient, and side force coefficient with changing altitude (i.e., degree of rarefaction). A comparison between the numerical and experimental results demonstrates that, within the investigated conditions, the average deviations of the axial force coefficient, normal force coefficient, and pitching moment coefficient are 1.38%, 6.03%, and 12.2%, respectively, thereby validating the effectiveness of the current numerical simulation method. This study provides technical support for the aerodynamic braking design of Martian orbiters.
To parametrically assess the aerodynamic-propulsion integrated performance of air-breathing hypersonic vehicles and comprehensively elucidate the influence rules of overall vehicle parameters on their performance,this paper proposes a parametric calculation method for integrated performance grounded in thrust-drag equilibrium.This method comprehensively considers the coupling between lift-drag characteristics and engine features,thereby providing a solid basis for subsequent research.Under this research framework,with a focus on the vehicle's cruising conditions at a constant altitude and speed,an in-depth exploration is made into the effects of overall parameters such as cruising angle of attack,engine performance,and aerodynamic performance on the vehicle's integrated performance.Research results reveal that,for typical vehicle configurations,the angle of attack corresponding to the optimal lift-drag ratio of 8.1° differs from that of 6.7° corresponding to the maximum cruising specific impulse.When the vehicle's aerodynamic performance remains constant,within a certain range,installing an engine with a higher baseline specific impulse and a specific impulse that decreases as the equivalence ratio increases can endow the vehicle with more excellent integrated performance.When the engine's thrust characteristics are invariant,through optimizing the aerodynamic shape to reduce the vehicle's zero-angle-of-attack lift coefficient,lift-curve slope,zero-lift drag coefficient,and lift-induced drag coefficient,while concurrently increasing the zero-angle-of-attack baseline flow coefficient and the flow-coefficient change rate,the vehicle's integrated performance can be effectively enhanced.Through the research presented in this paper,it is expected to provide guidance for the overall parameter design of air-breathing hypersonic vehicles.
To address the insufficient research on near-surface gale fluctuation characteristics in the Qinghai-Tibet Plateau,Xizang Automous Region,China(hereafter"Xizang Plateau"),this study utilizes ultrasonic anemometer data from two stations,Langkazi and Shiquanhe.Wind samples with a 10-minute average wind speed exceeding 8 m/s are selected.Based on statistical analysis,the fluctuating wind characteristics under type B terrain conditions(wide-valley lake basin and valley terrain)in the Xizang Plateau are investigated.The results show that the average turbulence intensities in the along-wind and across-wind directions are 0.23 and 0.21,respectively,and the average gust factors are 1.52 and 0.45,respectively.The overall fluctuation intensity is lower than that in coastal typhoon areas.The along-wind turbulence intensity and gust factor are close to the recommended values of the ASCE 7-22 of the United States.The average integral length scales in the along-wind and across-wind directions are 111 m and 113 m,respectively,with the along-wind integral length scale being closer to the recommended value of the AIJ-RLB-2004.The power spectrum of along-wind fluctuating wind speed shows the highest consistency with the von Kármán spectrum.Furthermore,a modified model for the relationship between gust factor and turbulence intensity applicable to such terrain areas is proposed to investigate the evolution laws of the fluctuating wind.The results show that,within the dominant inflow direction range,turbulence intensity and gust factor significantly decrease with increasing wind speed,while the integral length scale exhibits a clear directional dependence.Overall,the fluctuating wind parameters under type B terrain conditions in the Xizang Plateau show distinct regional characteristics.The findings can serve as a reference for wind-resistant design of building structures in such regions.
Large language model agents are driving a paradigm shift in aerodynamics from experience-driven approaches toward the triple integration of data, knowledge, and physics. To address the challenges of tacit knowledge inheritance and trusted collaborative execution of complex tasks, these agents establish an enhanced intelligence closed loop through two pathways: internalization of disciplinary knowledge, which enables structured sedimentation and reuse of unstructured knowledge, and intelligent orchestration of toolchains, which ensures physical consistency and procedural reliability in multi-tool collaboration. This review systematically surveyed the research progress of large language model agents in aerodynamics, constructed a five-dimensional technical framework consisting of prompt engineering and chain-of-thought reasoning, knowledge and tool augmentation, memory enhancement and long-context mechanisms, multi-agent systems, and human-in-the-loop. It reveals a three-stage evolutionary logic from automation through refinement to deep integration, identifies key technical gaps including the lack of evaluation systems, incomplete toolchain coverage, weak interdisciplinary knowledge fusion, insufficient human-machine collaboration depth, and computational efficiency optimization, and proposes development principles centered on discipline logic-led, technology capability-supported, and engineering value closed-loop. The review further envisions future directions such as collaborative evaluation ecosystem construction, deep internalization of physical laws, and efficient reasoning mechanisms. This review aims to provide systematic theoretical anchors and practical pathways for research on aerodynamic agents, foster interdisciplinary dialogue between artificial intelligence and aerodynamics, support equipment innovation and scientific breakthroughs, and advance the construction of a new intelligent aerodynamics paradigm.
To address the challenge of predicting the effects of surface roughness on the aerodynamic characteristics and trajectory of vehicles during hypersonic reentry, this work establishes a feasible loosely coupled model integrating aerodynamics in engineering applications, aerothermal effects, dynamic ablation, and structural heat transfer, forming a coupled system with mutual interactions. Based on this model, a statistical approach is introduced to characterize the uncertainty of surface roughness, and a distributed random roughness model is developed with the statistical means and variances of different meridional planes as constraints. The model is used to represent the non-uniform surface roughness morphologies of axisymmetric spherical-cone reentry vehicles arising from manufacturing and ablation processes, and to investigate their effects on the aerodynamic and trajectory characteristics of the vehicle. The numerical results indicate that, as the regular surface roughness of the vehicle increases from 3 μm to 9 μm, the drag coefficient rises by 6.2×10−4, and the horizontal flight distance in the late reentry phase is reduced by approximately 34 meters. When randomly distributed roughness is considered, with both the mean roughness and variance set to 9 μm, the difference in horizontal flight distance relative to the 3 μm regular roughness case reaches 111 meters, which is 77 meters greater than that in the 9 μm regular roughness case. These findings provide a new perspective for aerodynamic prediction and thermal protection system design of reentry vehicles.
Although the dual-throat Ludwieg tube wind tunnel can effectively suppress fast-opening valve disturbances, the high-speed jet induced by the sharp expansion of the first Laval nozzle severely damages the spatial uniformity of the downstream flow field. To mitigate this jet effect, an aerodynamic flow conditioning scheme involving the introduction of a porous plate at the inlet of the settling chamber is proposed. Based on unsteady numerical simulations, the effects of the damping coefficient, thickness, and configuration of the porous plate on the jet structures within the settling chamber flow field—both before and after stable wind tunnel operation—are investigated. Furthermore, the distribution patterns of the Mach number and turbulent kinetic energy (TKE) at the exit of the main Laval nozzle are quantitatively evaluated. The results indicate that the jet suppression efficacy of the porous plate is highly dependent on its aerodynamic and geometric parameters. An optimal damping coefficient exists (ζ = 2.11×107); an excessively high damping coefficient can suppress the shock/expansion wave systems in the core flow region but incurs significant stagnation pressure losses and degrades the spatial uniformity of the Mach number distribution. Additionally, an optimal thickness is identified (h = 10 mm), beyond which internal micro-jet coalescence occurs within the porous plate, triggering large-scale jet structures that degrade the flow field quality. Addressing the dynamic instability induced by a single-stage thick porous plate, this paper verifies the superiority of a dual-stage flow conditioning configuration. Through the spatial truncation and multi-stage dissipation of the initial wakes, this layout successfully disrupts the low-frequency, large-scale jet structures, thereby effectively mitigating the global instability of the wind tunnel. This study clarifies the aerodynamic dissipation mechanisms of porous plates in dual-throat Ludwieg tube wind tunnels, providing valuable guidance for the design and optimization of low-disturbance flow fields in hypersonic wind tunnels.
