 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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- Study Effects of the Floater Geometry on the Output Power of Ocean Wave
Energy Harvesters-
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Abstract: Abstract Nowadays, with increasing progress in technology and the growth of the human population, the need for energy is increasing, consequently, researchers pay more attention to renewable energies. One of these sources of energy is ocean wave energy, which has the highest energy density among other renewable energies. However, because of the low frequency of ocean waves, this source of energy gets fewer considerations in the case of vibration-based energy harvesting. In this study, heave motions of an unmoored moving floater are considered for vibration-based energy harvesting. To do so, a two-degree-of-freedom piezoelectric system is considered, and its governing equations are derived. Then, the geometry of the floater, which is used for harvesting energy from the ocean waves is studied. Finally, the effects of changing the geometry of the floater on the amount of harvested energy are studied.
PubDate: 2023-03-21
- Routing Prediction Strategy for UAV Swarm Network Using Pigeon-Inspired
Optimization-Based Neural Network-
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Abstract: Abstract A routing prediction strategy via a pigeon-inspired optimization (PIO)-based neural network (NN) is designed for UAV swarm networks with highly dynamic topology. The proposed strategy can predict the performance of the neighboring nodes as the next hop. For more precise prediction and less computational complexity, the states of the UAV swarm motion and the network are considered as the prior information, and the PIO-based NN framework is established. Based on the system model, PIO is applied to find the optimal weight matrices of the NN-based routing prediction model. The matrix of the hop count index function is calculated using this prediction model. The proposed strategy can directly determine the next hop based on the prediction results or can be combined with other routing methods to maintain a balance between the stability and the shortest path. Numerical simulations are conducted to demonstrate the effectiveness of the proposed strategy.
PubDate: 2023-03-20
- Effect of Non-isothermal Phase Change on Multiple Bubble Pulsations
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Abstract: Abstract Main reasons for the damage to submerged structures include shock waves and high-velocity jetting hits at the collapse of the cavitation bubbles, which repeatedly occur in subsequent bubble periods. Although other methods, e.g., experiments and theoretical approaches, have been conducted to gain knowledge of bubble dynamics, these approaches have difficulty in capturing microscopic phase changes and are not suitable for largely deforming motion, respectively. Therefore, numerical simulations using Navier–Stokes equations or Euler equations have been used to describe the bubble’s dynamic behaviors and detailed physical phenomena inside the bubble. Nevertheless, previous numerical simulations had limitations in expressing realistic and accurate bubble dynamics. For example, their results focused only on the first bubble period, not on multiple periods; thus, they could not obtain the information about the continuous shock loading near the structures. More noticeably, the thermal effect in multiple pulsations has never been addressed; since the pressure and temperature inside the bubble are formed near the critical point, the thermal effect has to be considered for accurate computations. Herein, the isothermal and non-isothermal phase change models are applied to observe the phase change effect and thermal effect on the bubble dynamics, respectively. Contrary to the isothermal model, which captures bubble dynamics up to the second bubble period, the non-isothermal model accurately expresses bubble dynamics up to the third bubble period, which is closely related to the thermal effect at the collapse region.
PubDate: 2023-03-16
- Multiple Arc Composition Technique for S-Duct Intake Construction Strictly
Obeying Area Rule-
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Abstract: Abstract A technique was developed to design the intake duct shape by composing multiple arcs to build duct cross-sections, which presents the capability to represent the complex shape of various S-duct intakes by automatically generating intermediate cross-sections between given control cross-sections and flexibility to adjust those cross-sections to strictly obey prescribed area rule. Every cross-section is assumed to have a bilateral symmetric shape. The one half is divided into two pieces, top and bottom, each of which this multi-arc composition technique is applied to build. To overcome the underdetermined system even with the three-arc composition scheme, geometrical parameters are grouped into two sets. One is a set of parameters determined by geometry equations and imposed constraints. The other is a set of parameters obtained by morphing the features of intake cross-sections to fill the gap between the numbers of variables and equations. The concave shape of the intake cross-section can be handled by allowing some geometrical parameters, such as arc radius and angle, to have negative values. Some rules for morphing algorithm and a driving curve in addition to area variation have to be prescribed in advance and they are chosen to change linearly in this study. Demonstrations showed the ability of the three-arc composition technique by successfully generating various S-duct intakes consisting of complex shape cross-sections and strictly obeying a prescribed area rule.
PubDate: 2023-03-13
- Cooperative Global Path Planning for Multiple Unmanned Aerial Vehicles
Based on Improved Fireworks Algorithm Using Differential Evolution
Operation-
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Abstract: Abstract Multiple unmanned aerial vehicles’ (multi-UAVs) cooperative global path planning is considered as a complexed nonlinear optimization problem. The improved hybrid fireworks algorithm with differential evolution (HDEFWA) is put forward herein to handle the problem and yield optimal flyable paths for multi-UAVs. The UAV paths are expected to be safe and short, of which the cost function is modeled according to realistic scenarios. The proposed HDEFWA can generate the extra DE-sparks through the mutation, crossover, and selection operators using the highly ranked individuals, which greatly enhances the information sharing capacity among the better individuals and thus effectively strengthen the capacity to escape from local optima. To handle the multi-UAVs cooperative planning, the whole firework population in HDEFWA is divided into a series of parallel firework groups, and the information interaction mechanism is established to calculate the cooperative cost of solutions to achieve the collision-free among UAV paths. Simulation results demonstrate that our HDEFWA can effectively settle multi-UAVs cooperative path planning with the better performance than other population-based algorithms.
PubDate: 2023-03-11
- Rotorcraft Flight Regime Recognition in Complex Maneuvers Using Adaptive
Extended Kalman Filter-
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Abstract: Abstract The retirement time of helicopter components can be extended using the health and usage monitoring system (HUMS) and revisiting the flight spectrum with enough precision through fatigue damage analysis. The recognition of flight regimes for air vehicles with complex maneuvers is a major problem in determining the experienced spectrum. The relationship between flight variables and regimes is complex and coupled during a mission profile with multiple maneuvers that needs more efficient algorithms. In this paper, a logical framework is developed to identify the complex maneuvers based on the qualitative and descriptive interpretation of each maneuver by the pilot. The regime recognition criteria are implemented in the algorithm using an adaptive extended Kalman filter with both flight instruments and control movements as the measurements. The proposed algorithm classifies the flight regimes into the standard fatigue spectrum while needing no large amount of training data and not being sensitive to pilot behavior and mission variations. The proposed regime recognition algorithm is evaluated through extensive simulation of a comprehensive dynamic model of helicopter flight. The results show the improved accuracy of the proposed method in comparison with that of previous ones, while the proposed method is easier to embed in HUMS software without exhaustive training.
PubDate: 2023-03-06
- Design and Verification of Electric Pump for Small LOX/Methane Rocket
Engine-
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Abstract: Abstract As the global market for small satellites grows, the demand for small launch vehicles rises as well. In addition, the accelerated technological development of battery and motor have drawn attention to the electric pump cycle for small launch vehicles which utilizes electric motor and battery packs to drive a pump. In this study, a practical design of an electric pump cycle for a 5400 N-class rocket engine is proposed. First, the electric pump with very low specific speed was designed due to limited rotational speed of a commercial motor for cost-effective system. Second, to determine the appropriate discharge angle for very low specific speed pump, two impellers with different discharge angle were designed and verified by numerical and experimental methods. Type A impeller with discharge angle of 10° focusses on achieving high efficiency, while type B impeller with discharge angle of 33° has general geometry. The hydraulic and suction performance of the two impellers was first compared in a cold-water performance test. The hydraulic efficiency of type A impeller was 52.53% and higher than that of type B impeller, 43.28%. Furthermore, type A impeller had higher suction performance than type B impeller; the critical cavitation number of type A impeller was more than 0.07 lower than that of type B impeller. Moreover, the operation of the electric pump under cryogenic environment was verified by performing cryogenic performance tests using liquid nitrogen as simulant.
PubDate: 2023-03-05
- A Load Balance Local LEO Satellite Network AP Selection Strategy
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Abstract: Abstract LEO satellites can serve as spatial extension of terrestrial network, introducing high-quality service through low latency and convenient access. The main challenge is the dynamicity causing by high relative speed between LEO satellites and terrestrial terminals. So how to make proper access point (AP) selection decision is a key problem. In this paper, we focus on AP selection problem, propose a local satellite AP selection strategy aiming at balancing the network load. We establish terminal coverage model and data transmission rate model for data collection and performance assessment. Results of comparative experiments show that the proposed strategy can balance the network load, lower handover frequency while maintaining well throughput expectation.
PubDate: 2023-02-28
- Study on the Micro-vibration Suppression of a MnCu Spring Isolation
Platform with Low Stiffness and High Damping-
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Abstract: Abstract Reaction wheels are the primary micro-vibration sources for microsatellites. To reduce the adverse effects of micro-vibrations, a six-degree-of-freedom (6-DOF) vibration isolation scheme with low stiffness and high damping is proposed. Through six-component force measurements, the harmonic characteristics of the micro-vibrations generated by a reaction wheel are determined. Based on an assumption of small deformation linear elasticity, a dynamic model of a convergent isolation platform is established. With high damping characteristics, helical springs made of MnCu (manganese copper) alloy are selected as the isolation element of the platform. After a modal analysis and stiffness design, the key structural parameters of the isolator are determined. According to the coupling of degrees of freedom, the transmissibility of the isolator is simulated and compared to titanium and aluminum alloys. Combined with on-ground and on-board tests, the effectiveness of the isolation platform is verified. The research shows that the 6-DOF isolation platform based on the MnCu spring realizes multidirectional low-frequency and low-magnitude micro-vibration suppression. The minimum initial isolation frequency of the designed isolator is 16.8 Hz, and the best suppression effect reaches 17.5 dB. The proposed isolator’s application successfully controls high-order harmonics and sensitive load response behaviors.
PubDate: 2023-02-24
- Weapon-Target Assignment and Firing Scheduling for Rapid Engagement with
Heterogeneous Interceptors-
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Abstract: Abstract This paper addresses engagement control of naval fleet with heterogeneous defensive weapons against approaching anti-ship missiles. A combined decision making problem that include weapon-target assignment and firing schedule is considered to decide on which defensive weapons to fire on which targets in what order, taking into account the flight time of heterogeneous defensive weapons, limitations in the launch interval, and the geometric aspects of the incoming targets. A new mixed-integer nonlinear program formulation is presented; then, a mixed-inter linear program approximation on the basis of piecewise linear approximation and McCormick relaxation is proposed for computational tractability. For further efficiency, a greedy algorithm is also presented to deal with a realistic problem. Numerical examples on several representative engagement scenarios demonstrate the validity of the proposed methodology.
PubDate: 2023-02-24
- Quantitative Stability Analysis of an Unmanned Tethered Quadrotor
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Abstract: Abstract Tethered quadrotors, unmanned aerial quadrotors connected to a fixed point via tether cables, have been widely applied in numerous aerial tasks. However, their structural parameters and external disturbances give rise to dynamic stability issues, resulting in uncontrolled autonomous flight, shaking, and vibrating. Thus, this article investigates the quantitative stability of a tethered quadrotor using the Lyapunov exponent approach. First, a mathematical model of the tethered quadrotor is developed, and its dynamic stability is quantified to verify the rationality of the designed physical prototype and enhance the aerial system’s stability. Both simulation and experimental results show that the dynamic stability during the landing phase is better than that during takeoff. Finally, optimizing the structural parameters enhances the dynamic stability, which is sensitive to cable length, wind gusts, and yaw angle.
PubDate: 2023-02-21
- Jet Characteristics of Pulsed Arc SparkJet Actuator and Performance
Improvement with Dual-Spark Pulses-
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Abstract: Abstract Performance characteristics of the jet produced by SparkJet actuator are investigated with a numerical simulation. The spark discharge is considered as a uniform heat source in energy equation modeled with a user-defined function in Fluent. The SparkJet actuator is tested with both single-spark pulse and dual-spark pulses. Validation with experiments for a single 50 mJ spark pulse shows that Joule heating factor for the heat source term is about 5%. Jet velocity increases and total impulse decreases with the distance of the spark from the exit orifice. Peak velocity and peak thrust increase with the volume of the spark discharge. Total impulse increases as the time delay between two temporally separated pulses increases. Spatially separated dual-spark pulses produce higher jet velocity as the time delay between the pulses increases. Performance testing of jets in various operating modes informs that the SparkJet actuator is more efficient and effective when spatiotemporally separated dual-spark pulses are turned on in downstroke operation with an adequate time delay between pulses.
PubDate: 2023-02-09
- Correction to: Geometric Effects of Liquid Rocket Engine Pintle Injectors
in Supercritical Combustion-
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PubDate: 2023-02-01
- Correction: Characteristics of Base Drag and Flow with Nozzle Flow
Conditions in Supersonic Flow-
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PubDate: 2023-02-01
- Correction to: Vertiport Performance Analysis for On-Demand Urban Air
Mobility Operation in Seoul Metropolitan Area-
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PubDate: 2023-02-01
- Correction to: Numerical Investigation of Wing–Multiple Propeller
Aerodynamic Interaction Using Actuator Disk Method-
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PubDate: 2023-02-01
- Study on Performance of Closed Air Circulation System Driven by Electric
Compressor-
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Abstract: Abstract Aircraft are developing towards the goal of low energy consumption and high efficiency; higher requirements are put forward for the energy utilization efficiency of the environmental control system. This paper presents a new type of closed air circulation system driven by an electric compressor, which can make more efficient use of aircraft energy. Aiming at the new environmental control system, the neural network algorithm was used to construct the system component model and then carry out the system simulation. The results showed that the average error between the simulation outputs and experimental values of the model constructed by this method was less than 4.5%, which effectively verifies the correctness of the system modeling. Compared with the traditional three-wheel system, the proposed environmental control system driven by an electric compressor can reduce the engine air intake by 64.5% and improve the cooling efficiency by 210%. The proposed new environmental control system can provide a reference for the design of the environmental control system of the next generation of aircraft.
PubDate: 2023-02-01
- Rapid Airfoil Inverse Design Method with a Deep Neural Network and
Hyperparameter Selection-
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Abstract: Abstract A deep-learning based rapid engineering design (DL-RED) algorithm is developed and presented for solving engineering inverse design problems. The algorithm generates an inverse design deep neural network (IDNN) by performing a two-stage hyperparameter selection and iteratively enhancing training database. The initial hyperparameter selection defines the configuration of IDNN that increases the accuracy of inverse design and reduces the network training time. Then database enhancement loop refines the training database by iteratively adding new samples to initial database based on results of validation. After the training database is generated the final hyperparameter selection is performed. A construction of Airfoil inverse design neural network is demonstrated in this paper. The Airfoil-IDNN generates a NACA 4-series airfoil that corresponds to target aerodynamic parameters given as an input. During the database enhancement loop the validation mean squared error has reduced to 57.37%, and totally to 96.48% after the final hyperparameter selection. The accuracy of the Airfoil-IDNN was demonstrated using two case studies. The first case study shows how accurate the network can generate an airfoil with arbitrary input parameters. The second one shows whether the IDNN can generate existing airfoils by a set of target parameters.
PubDate: 2023-02-01
- Development Trend of Liquid Hydrogen-Fueled Rocket Engines (Part 1:
Performance and Operation)-
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Abstract: Abstract SpaceX's successful development of reusable rockets and the realization of low-cost operations have significantly impacted the space industry, institutions, and companies. Price competitiveness has become a hot topic for launch vehicle development. A hydrogen-fueled rocket engine can be its solution. The developed countries are attempting to improve the performance and reliability of engines using a hydrogen-fuel. This paper summarizes the development and operation trends of hydrogen-fueled rocket engines of developed countries. It provides fundamental data for hydrogen-fueled rocket engine development, which is expected to be helpful in its future development.
PubDate: 2023-02-01
- Correction: Assessment of a High-Order High-Resolution ESWENO-P Scheme for
AVI/BVI Problems-
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PubDate: 2022-12-16
DOI: 10.1007/s42405-022-00557-1
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Hybrid journal (It can contain Open Access articles)
