Aerospace Systems最新文献

Composite lattice anisogrid adapters are highly favored in space rocketry design, serving as crucial interface structures between rocket stages or between the payload and its supporting structure. Their unique structural configuration allows them to withstand significant weight loads without succumbing to buckling. However, optimizing their design parameters could further enhance their strength and efficiency. Particularly, reinforcing the lower hoop ribs in a conical lattice adapter can substantially enhance its strength under axial compressive loads, thus preventing buckling. In this study, we begin by presenting a finite-element model of a lattice adapter featuring helical ribs that follow geodesic paths. To validate the model's accuracy, experimental prototypes and finite-element models from previous research are utilized. Subsequently, a neural network model is trained using the dataset generated from finite-element analysis results. This neural network model aims to predict, explore, and optimize the impact of lower hoop ribs' thicknesses on the critical axial buckling load of the adapter. The analysis ultimately confirms that an adapter designed with optimized ribs demonstrates a remarkable 51% increase in load capacity before buckling compared to an adapter designed with uniform ribs. This underscores the significance of optimizing design parameters for enhancing structural performance in space rocketry applications.

Graphical Abstract

Controlled flight into terrain accidents pose a significant threat to aviation safety, emphasizing the need for effective automatic ground collision avoidance system (Auto GCAS). However, the diversity and complexity of missions present considerable challenges to aircraft collision avoidance control. This paper proposes an approach for trajectory prediction based on the model predictive control (MPC) technique. Different from previous methods that rely on predefined fixed trajectories, the proposed approach incorporates constraints of aircraft state and actual terrain to generate an optimal trajectory. The safety and effectiveness of the method are demonstrated through integrating the trajectory prediction algorithm into the Auto GCAS system. The simulation results show that the MPC-based Auto GCAS can achieve optimal collision avoidance outcomes aligned with the aircraft's performance and mission needs.

The aircraft wing is a complex structure consisting of many joined components. Because of the inevitable variability of the component shapes, different deviations may occur in the joining process including unreduced gaps between parts which can negatively affect the quality of further assembly. When developing the assembly process, the influence of these variations can be taken into account by considering the initial gap between the parts. For the variation analysis of the aircraft assembly process, a large set of random initial gaps between the parts is needed. To get this set without initial gap measurements it is proposed to use the method of modeling the initial gap based on the mode shape decomposition. The initial gap is represented as a sum of orthonormal mode shapes with random coefficients. This paper describes the method for estimating parameters and generating initial gap samples for such cases without initial gap measurements. The application of this method is illustrated for the wing assembly process. The effectiveness of the initial gap modeling based on residual gap measurements is studied and the application of this initial gap model for fastening pattern optimization is performed.

Synthetic jets (SJs) are becoming increasingly popular in aerospace engineering due to their potential applications in flow mixing enhancement, boundary layer control, and thermal load reduction. These pulsating jets involve the periodic motion of fluid in and out of a cavity through an orifice generated by a vibrating diaphragm at the cavity base. SJs are unique because they comprise working fluid and do not require an external fluid source, setting them apart from conventional flow control techniques. Although the net mass flux is zero in a complete cycle, there is a finite net momentum flux due to the imbalanced flow conditions across the orifice, and hence SJs are also known as Zero Net Mass Flux (ZNMF) jets. Numerous experimental and numerical studies have evaluated the efficacy of SJs in controlling the flow and heat transfer characteristics under various conditions, including quiescent and cross-flow situations. This review provides a comprehensive overview of the progress in synthetic jet applications in the last 40 years, specifically focusing on their potential use in flow control, heat transfer, and related applications in aerospace engineering. The strengths and limitations of SJs are discussed, and critical areas are identified for future research and development, including further optimization and refinement of these unique jets.

Mode composition beamforming (MCB) is a frequency-domain rotating beamforming method for rotating acoustic source localization. Compared with other rotating beamforming methods, MCB has both wide applicability and high computational efficiency. The expression for MCB in literature is however not suitable for the application of deconvolution algorithms, which limits further improvements of dynamic range and spatial resolution of MCB. In this work, application of deconvolution algorithms to MCB is investigated. Firstly, the expression of MCB is transformed into a matrix form. Then the deconvolution algorithms of MCB, including DAMAS and CLEAN-SC, are derived based on the matrix form of MCB. Nextly the deconvolution algorithms of MCB are verified through a benchmark simulation case. Lastly deconvolution algorithms of MCB are applied in a phased array measurement for the rotor of an unmanned aerial vehicle to improve the dynamic range and spatial resolution of rotating source localization.

During flight, dragonfly wings can be thought of as an extreme light-weight airfoil. Many of the flight properties of tiny dragonfly wings are also shared by micro aerial vehicles (MAVs), which are nowadays finding widespread use in military and other commercial applications. It is observed that dragonflies have distinct cross-sectional corrugation that function to produce different local-aerodynamic characteristics. Along the wing’s longitudinal axis, there are significant variations in corrugation profile which adapts to different flight condition accordingly. Dragonflies fly in the extremely low-Reynolds-number zone, showcasing their outstanding flying characteristics even in turbulent conditions. The current study focuses on understanding the effect of free-stream turbulence on three distinct 2D corrugation profile located at 0.3, 0.5, 0.7 relative to wing span length during dragonfly’s gliding phase. The corrugation pattern required for computational analysis was designed in CATIA and imported to the commercially available CFD software ANSYS. The computational study is conducted on 2D, static non-flapping three corrugated profile at 10,000 Reynolds number subject to turbulence intensity of 0.5%, 1–10% at various angle of attack. This study examines the aerodynamic performance of each corrugation profile. The current numerical analysis shows that at a positive angle of attack, the increase in the lift coefficient remains largely unaffected by the corrugated pattern on the wing’s suction area. Virtual airfoils are created by rotating vortices that are trapped in profile valleys of corrugation patterns.

This paper presents an image-feature-aware (IFA) planner for quadrotors, which integrates image feature tracking into its path-planning framework. The IFA-planner aims to improve the visual localization performance of quadrotors in multifarious environments where feature points may be sparse or diverse. Unlike traditional methods that decouple visual localization and path planning, the IFA-planner adaptively identifies and tracks feature-rich spatial units, called anchors, along a feasible path. The anchors provide additional feature points to the visual localization module, especially in scenarios with sparse or uneven features, thus enhancing localization robustness. Via clustering-based method, the anchor selection can handle different feature point distributions without manual tuning. Moreover, a detachment prediction mechanism is incorporated to convert the selected anchors into yaw constraints and update them according to the quadrotor’s predicted state. This mechanism ensures the environmental adaptability of the anchors and avoids sudden feature changes. The effectiveness of the IFA-planner is demonstrated in simulation experiments. The source code has been released at https://github.com/ximuzi2023/IFA-planner.

Essential qualities which a drone can effortlessly accomplish for every task include performance, safety, accessibility, and adaptability because of its efficiency. For different reasons, the efficiency of the drone is affected by an extensive number of parameters. Thus, a focus on improving drone’s efficiency has been proposed in this study. Usually, operational speed affects efficiency. Propellers have the potential to regulate operating speed. The propeller is an essential component of the drone's operation, and experts are always looking for new ways to improve its performance through novel studies. Multiple studies have been conducted and the findings indicate that employing leading-edge (LE) tubercles on propellers produces superior outcomes. For this computational study, the re-normalization group (RNG) equations with a k − ℇ turbulence model have been solved, using the Ansys Fluent solver. The range of RPM was 2000–8000, while the flow velocity ranged from 0.1 to 0.6 J (advance ratio). Calculations showed that the propeller with serrations had a significant improvement in thrust, power, thrust coefficient and power coefficient values. The outcomes were contrasted with the computational results from the available literature. Aerodynamic and overall performance trends showed a good degree of consistency, suggesting that tubercle propellers will be superior to baseline propellers in terms of efficiency.

Microburst is a common low-level wind shear weather, and it seriously threatens the safety of civil aviation flights. It is characterized by suddenness, short duration, small scale and large intensity, which leads to difficulties in accurately obtaining real data, in real-time assessing the degree of harm. In this paper, based on the characteristics of microburst, according to computational fluid dynamics, taking into account the changes of temperature and pressure with height, establish a three-dimensional wind field simulation model, and verify the validity of the model by experimental data. Using the F-factor, construct the quantitative model of each position in the wind shear region, and analyze the danger degree of the micro downwash storm flow. Investigate the influence of inlet velocity, inlet height and inlet diameter on the hazard radius, and the simulation results show that the hazard radius increases logistically with the decrease of altitude, and when the inlet velocity increases by 5 m/s or the inlet height increases by 80 m, the hazard radius increases by about 10% on average. The method of this paper can provide a new way to quantitatively analyze the wind field characteristics of micro downburst storms.

Acoustic impedance model of slits plays a crucial role in addressing noise reduction challenges in aircraft engines. To gain further insights into the sound absorption mechanisms of slits and to develop acoustic impedance model, this study investigates the bias flow effect on the acoustic impedance of compressor blade tip slit. The evolution of the blade tip leakage flow is calculated by the combination of two-dimensional discrete vortex model and one-dimensional acoustic propagation model. In this manner, the bias flow effects on the acoustic characteristics of the blade tip slits, such as slit impedance and sound absorption coefficient, are investigated. The model is validated through the experiment of bias flow effect on a circular orifice. It is further extended to calculate the flow field response of slits with different blade height and different aspect ratios. The results show that the acoustic impedance of equal area slits aligns closer with circular orifice experimental results than the acoustic impedance of equal width slits. Larger hub to shroud distances causes less influence on the blade slits of the same width. Increasing hub to shroud distance reduces the Ma of the maximum absorption coefficient. As aspect ratio increases, the acoustic reactance component corresponding to the acoustic mass of the slit decreases. Increasing the hub to shroud distance and increasing the aspect ratio of blade chord length to slit width can both improve the sound absorption under feasible conditions.