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This paper presents an experimental assessment of a blended fatigue‐extreme controller for load control employing trailing edge flaps on a lab‐scale wind turbine. The controller blends between a repetitive model predictive controller that targets fatigue loads and a dedicated extreme load controller, which consists of a simple on‐off load control strategy. The Fatigue controller uses the flapwise blade root bending moments of the three blades as input sensors. The Extreme controller additionally uses on‐blade angle of attack and velocity measurements as well as acceleration measurements to detect extreme events and to allow for a fast reaction. The experiments are conducted on the Berlin Research Turbine within the large wind tunnel of the TU Berlin. In order to reproduce test cases with deterministic extreme wind conditions that follow industry standards, the wind tunnel was redesigned. The analyzed test cases are extreme direction change, extreme coherent gust, extreme operating gust and extreme coherent gust with direction change. The test cases are analyzed by on‐blade angle of attack and velocity measurements. The load control performance of the Blended controller is compared to the pure fatigue oriented and the pure extreme load controller. The Blended controller achieves a maximum flapwise blade root bending moment reduction of 23%, which is comparable to the reduction achieved by the Extreme controller.

The use of passive heat transfer enhancement strategies to improve heat transfer performance in heat exchanger has received a lot of attention. In this paper, passive heat transfer enhancement methods utilizing vortex generation in the flow field have been discussed in detail. Three classic techniques for improving passive heat transfer in heat exchangers have been identified in the literature: boundary layer deformation, swirl formation, and flow destabilization. The longitudinal vortices generated by vortex generators have been found to reduce the wake region behind tubes, thus increasing turbulence strength and flow mixing. This review takes into account the effect of geometrical variations of vortex generators on thermo-fluid performance. Delta winglet vortex generators outperform rectangle-winglet vortex generators in terms of heat transfer performance. However, using hole-type rectangular winglets has shown promising results with more than 16% enhancement in thermo-fluid performance. Among several winglet angles examined by various researchers, the attack angle in the range of 30°–45° has resulted in optimum performance. Some variations of rectangular winglets such as wavy winglets have been reported to enhance the overall thermo-fluid performance by 8–16%. This paper provides insight into different experimental and numerical techniques for the enhancement of thermo-fluid performance of cross-flow heat exchangers. This review article can be very helpful to industrial and academic researchers working in the area of compact and efficient heat exchanger design with enhanced thermo-fluid performance.

A high-speed train with wings (HSTW) is a new type of train that enhances aerodynamic lift by adding wings, effectively reducing gravity, to reduce the wear and tear of wheels and rails. This study, based on the RNG k−ε turbulence model and employing a sliding grid method, investigates the aerodynamic effects of HSTWs with different angles of attack when passing through tunnels. The precision of numerical simulation method is validated by data obtained through a moving model test. The results show that the lift of the HSTW increases upon entering the tunnel, with an average lift in the tunnel of 33.3% greater than that in the open air. The angle of attack is reduced from 12.5° to 7.5° when the train enters the tunnel, which can better reduce the lift fluctuations and concurrently also reduce the peak-to-peak pressure on the surface of the train and the tunnel, which is conducive to the train passing through the tunnel smoothly; hence, the angle of attack for the HSTW when passing through a tunnel is adjusted 7.5°. Furthermore, a comparison between the high-speed trains with and without wings demonstrates that the frontal pressure of the trains increases due to the blockage effect caused by the wings, while the rear of the trains experiences decreased pressure, which is primarily influenced by the wing wake. The outcomes of this study provide technical support for HSTWs passing smoothly through tunnels.

The airfoil DU91‐W2‐150 was investigated in the Low Speed Low Turbulence Tunnel at the Delft University of Technology to study unsteady aerodynamics. This experimental study tested the airfoil under a wide range of angles of attack (AoA) from 0° to 310° at three Reynolds numbers (Re $$ \\mathit{\\operatorname{Re}} $$ ) from 2×105 $$ 2\\times 1{0}^5 $$to 8×105 $$ 8\\times 1{0}^5 $$ . Pressure on the airfoil surface was measured and particle image velocimetry (PIV) measurements were conducted to capture the flow field in the wake. By examining the force coefficient and comparing the wake contours, it shows that an upwind concave surface provides a higher load compared to a convex surface upwind case, highlighting the critical role of surface shape in aerodynamics. When comparing separation at specific locations along the chord for all three Re $$ \\mathit{\\operatorname{Re}} $$values, it is observed that as Re $$ \\mathit{\\operatorname{Re}} $$increases, separation tends to occur at lower AoA, both for positive stall and negative stall. The examination of the aerodynamic force variation indicates that, during reverse flow, fluctuations are more pronounced compared to forward flow. This is owing to separation occurring at the aerodynamic leading edge (geometric trailing edge) in reverse flow. In terms of vortex shedding frequency, the study found a nearly constant normalized Strouhal number (St $$ St $$ ) of 0.16 across various Re $$ \\mathit{\\operatorname{Re}} $$and AoA values in fully separated regions, indicating a consistent pattern under these conditions. However, a slight increase in St $$ St $$ , between 0.16 and 0.20, was observed for AoA values exceeding 180°, possibly due to the convex curvature of the airfoil in the upwind direction. In conclusion, this research not only corroborates previous findings for small AoA values but also adds new data on the aerodynamic behavior of the DU91‐W2‐150 airfoil under large AoA values, offering various perspectives on the effects of surface curvature, Re $$ \\mathit{\\operatorname{Re}} $$ , and flow conditions on key aerodynamic parameters.

The box girder bridge is typical and widely used for the long-span bridge. Strong wind with a large effective attack angle often affects the long span, responsible for frequent flow field changes. Therefore, the best-suited structural changes which can be achieved to mitigate the wind effect on the long-span bridge are the primary efforts of this investigation. Further, the main objective of this investigation is a detailed parametric study by Incompressible Computational fluid dynamic simulation to mitigate the aerodynamic effect on long-span bridges. In more detail, the shape of the deck, the effective angle of attack on single and double decks, the gap between parallel decks, the crash barrier modification, the wind barrier, the fairing angle of the bridge deck, and its material property are the key parameter considered here for this wind effect analysis. The solution shows the improvement in the aerodynamic resistance of a long-span box girder bridge of trapezoidal cross-section at a large effective attack angle with proper faring angle, gaps and wind barrier material. Moreover, the flow passes through the gap, and the upwind box efficiently extracts more energy from this flow field than the downwind box.

Existing path planning methods have limitations such as random solutions, lack of sharing initial and terminal waypoints, and rare consideration of avoidance between multipaths in 3D. This paper presents a 3D multipath planning method for guided vehicles by employing an improved A  ∗ algorithm based on multiple avoidance tactics and terminal attack angles, which searches for a unique solution in restricted waypoint quantities under real‐time conditions and solves four major problems. Intelligent optimization algorithms have the characteristics of random multiple solutions, whereas Classical A  ∗ approaches show time consumption, insufficient smoothness, unsettable terminal attack direction, and collisions between multiple paths. To address these limitations, a terminal attack course orientation is achieved by solving the base unit vector, an engineering practical and implicit approach of node extension is built by extending the horizontal and vertical margin vectors, new tactics for terrain and threat zone avoidance are developed by filtering subnodes below the Earth’s surface with bilinear interpolation, and a detection tactic based on point‐in‐polygon checking is used to realize horizontal route avoidance with a better effect. The criteria used to measure multipath planning effectiveness include path length, path smoothness, avoidance capability, terminal attack angle settablity, and search time. Simulation results in two attack situations, three different degrees of freedom modes and 10 real‐world scenarios demonstrate that the improved A  ∗ search algorithm has higher efficiency and better performance than classical algorithms. The 3D multipath planning method shortened the search time by 91.4%, reduced the number of path nodes by 96.9% for Mode 1, improved the direction smoothness by 100% for Mode 3, and improved the pitch smoothness by 99.6% for Mode 2. The research not only provides practical tools for antisurface target operations and simulations but also offers new perspectives and methodological references for researchers in related fields.

The issue of uncertain roll angle and large angle of attack during the initial stage of launch has a significant impact on the initial attitude and control of canard‐controlled missiles. In this study, canard‐controlled missiles are employed to study the influence of multivortex structure present in the head under different roll angles at high angles of attack. The turbulence model was verified and used for simulation. The evolution of the multivortex structures behind the canard and their impact on the flow field and lateral force was investigated. The results show that the multivortex structure at the head forms a flow field structure dominated by two main vortices through vortices merging. When the geometry is symmetric, the symmetric vortices maintain a long symmetry region on the flow field, and the “X” shape shows higher flow field stability than the “+” shape. The asymmetric geometric structure produces two asymmetric main vortices, causing alternating steady separation and shedding of downstream vortices. This leads to alternating pressure fluctuations on the surface of the body, which are reflected in the lateral force through the integration of the pressure along the lateral direction. In contrast to the alternating shedding of separation vortices observed in a wingless configuration due to natural asymmetry, the asymmetrical main vortices induced by the asymmetry of canard cause alternant vortex shedding to occur earlier. With the increase of the angle of attack, the pressure difference of the head gradually dominated the lateral force, resulting in a drastic decrease in the lateral force coefficient.

This study presents a combined experimental and numerical investigation into the evolution of projectile attitude during oblique penetration into thin concrete targets at non-zero angles of attack. An oblique penetration test system was developed based on a cannon platform, incorporating a planar mirror reflection technique and high-speed imaging to capture the projectile’s spatial orientation. A set of equations was derived to relate the projectile’s three-dimensional attitude angles to its two-dimensional and mirror-reflected projections. The system demonstrated the ability to generate controlled initial angles of attack and accurately measure the projectile’s attitude, with measurement errors primarily within 2° and a maximum error of approximately 5°. Numerical simulations were conducted using the RHT strength model to replicate the experimental process. The simulation results showed good agreement with experimental data, with residual velocity errors less than 5% and attitude angle deviations below 15%. The validated model was further employed to study the effects of initial velocity, impact angle of attack, and target thickness on the evolution of projectile attitude. The findings reveal that, within a velocity range of 550–1000 m/s, the post-perforation attitude angle is negatively correlated with projectile velocity, though the variation remains under 15%. Increasing the target thickness from 90 mm to 240 mm significantly raises the post-perforation attitude angle and angle of attack by more than 70% and 20%, respectively. Under varying initial attitude angles, the final attitude angle increases with the initial value, with the maximum growth rate occurring around 15°, after which the rate gradually decreases. The angle of attack evolution during penetration can be divided into four stages: (1) crater formation, (2) plugging penetration, (3) breakthrough plugging, and (4) post-exit. These results offer valuable insights into projectile dynamics under complex impact conditions and provide theoretical support for the design of protective structures.

The increasing demand for energy in daily life and the finite nature of fossil fuel reserves have driven researchers worldwide to explore renewable energy sources such as wind energy. To optimize the performance and minimize energy losses in vertical wind turbines, parameters such as the airfoil's angle of attack, as well as the horizontal and vertical distances between the cylinder and the airfoil, must be adjusted to maximize aerodynamic efficiency and minimize entropy generation. Additionally, parameters such as the turbulent kinetic energy and Kolmogorov length scale are pivotal in engineering design. Each section of a wind turbine blade can be modeled as an airfoil, while the internal part of the main shaft is considered cylindrical. Therefore, this study aims to investigate the influences of NACA 0012 airfoil's attack angle and its positioning, that is, longitudinal and vertical placements of the cylinder relative to the airfoil, on the aerodynamic efficiency of the airfoil and entropy generation rate due to turbulent and viscous dissipations in turbulent regime. The findings indicate that the volumetric entropy generation at a 20 ° angle of attack is 364.2%, 302.35%, 147.78%, and 41.51% higher than at 0 °, 5 °, 10 °, and 15 °, respectively. The aerodynamic efficiency at a horizontal distance of 60 mm is 4.76%, 5.86%, and 8.95% higher than at distances of 120, 180, and 240 mm, respectively. The maximum turbulent kinetic energy at a vertical distance of −50 mm is 9.5%, 11.36%, and 12.5% higher than at distances of −25, +50, and +25 mm, respectively. The increasing demand for energy in daily life and the finite nature of fossil fuel reserves have driven researchers worldwide to explore renewable energy sources such as wind energy. To optimize the performance and minimize energy losses in vertical wind turbines, parameters such as the airfoil's angle of attack, as well as the horizontal and vertical distances between the cylinder and the airfoil, must be adjusted to maximize aerodynamic efficiency and minimize entropy generation. Additionally, parameters such as the turbulent kinetic energy and Kolmogorov length scale are pivotal in engineering design. Each section of a wind turbine blade can be modeled as an airfoil, while the internal part of the main shaft is considered cylindrical. Therefore, this study aims to investigate the influences of NACA 0012 airfoil's attack angle and its positioning, i.e., longitudinal and vertical placements of the cylinder relative to the airfoil, on the aerodynamic efficiency of the airfoil and entropy generation rate due to turbulent and viscous dissipations in turbulent regime. The findings indicate that the volumetric entropy generation at a 20° angle of attack is 364.2%, 302.35%, 147.78%, and 41.51% higher than at 0°, 5°, 10°, and 15°, respectively. The aerodynamic efficiency at a horizontal distance of 60 mm is 4.76%, 5.86%, and 8.95% higher than at distances of 120 mm, 180 mm, and 240 mm, respectively. The maximum turbulent kinetic energy at a vertical distance of ‐ 50 mm is 9.5%, 11.36%, and 12.5% higher than at distances of ‐25, +50, and +25 mm, respectively.

This study investigates the longitudinal flight control problem of air-breathing hypersonic vehicles subject to the asymmetric angle of attack (AoA) constraint. With the help of introduced tangent errors, the proposed control becomes low complexity in both structure and expression, especially for the non-adaptive control algorithm in the altitude loop. The asymmetric AoA constraint, which is more practical in comparison with the previously considered symmetric AoA constraint, is well accommodated. Output tracking errors are regulated into small residual sets within the designated convergence time. Uncertain aerodynamic coefficients, structural flexibilities and scramjet input saturation are synthetically handled, making the proposed control competent for a real hypersonic flight mission.