Angle Velocity Research Articles

Flight dynamic modeling and stability of a small-scale side-by-side helicopter for Urban Air Mobility

This paper aims to explore the development of a flight dynamics model for a small-scale side-by-side helicopter and describe its trim and stability characteristics. The helicopter is considered a suitable candidate for Urban Air Mobility (UAM) solutions, because of its reliable design and low noise characteristics, but still very small knowledge is present on the mathematical modeling approaches and dynamic properties. A 14 degrees of freedom nonlinear mathematical model is developed and semi-analytical models are employed to account for the presence of the shrouds. An iterative trim routine is developed and applied with a suitable control mix that allows the use of classic helicopter controls. To control the vertical speed and roll rate, the paper assumes an equal collective pitch and lateral cyclic in the two rotors, while a uniform plus a differential longitudinal cyclic is adopted for pitch and yaw maneuvers. The paper discusses unique characteristics of the side-by-side configuration as obtained from the stability analysis: an unstable high-frequency mode, governed by the vertical velocity and pitch angle arises when the center of gravity (CG) of the vehicle is aligned or placed in front of the two main rotors. Similarly, both lateral phugoid and roll subsidence modes are sensitive to the CG location. The side-by-side configuration presents also a stable spiral mode which needs to be carefully designed.

The influence of surgical technique guidance and surgeon's experience on the femoral head assembly in total hip arthroplasty.

The importance of the assembly procedure on the taper connection strength is evident. However, existent surgical technique guides frequently lack comprehensive and precise instructions in this regard. The aim of our experimental study was to evaluate the influence of the surgical technique guide on the femoral head assembly procedure in surgeons with differing levels of experience in total hip arthroplasty. Twenty-eight participants, divided into four groups based on their lifetime experience in total hip arthroplasty, conducted a femoral head assembly procedure in a simulated intraoperative environment before and after reviewing the surgical technique guide. Demographic information and the number of hammer blows were documented. Hammer velocity and impaction angle were recorded using an optical motion capturing system, while the impaction force was measured using a dynamic force sensor within the impactor. We observed a high variation in the number of hammer blows, maximum force, and impaction angle. Overall, the number of hammer blows decreased significantly from 3 to 2.2 after reviewing the surgical technique guide. The only significant intragroup difference in the number of hammer blows was observed in the group with no prior experience in total hip arthroplasty. No correlation was found between individual factors (age, weight, height) or experience and the measured parameters (velocity, maximum force and angle). The present study demonstrated a high variation in the parameters of the femoral head assembly procedure. Consideration of the surgical technique guide was found to be a limited factor among participants with varying levels of experience in total hip arthroplasty. These findings underline the importance of sufficient preoperative training, to standardize the assembly procedure, including impaction force, angle, and use of instruments.

Study on the influence of collision conditions on the surface morphology of compound droplets

In this study, a three-dimensional compound droplet collision numerical model is established by using volume of fluid. The morphological evolution of compound hollow droplets affected by high-speed solid droplet was studied in detail. Parameterized analysis is conducted on the velocity VS, center distance ϕ, and diameter ζ of high-speed small droplets. Through the analysis of the compound droplets flow field, it is found that the broken mode of compound droplets is caused by the increase in Pn (dimensionless pressure) and θ (velocity angle). The results show that the surface Pn of compound droplets is positively correlated with the velocity VS of high-speed small droplets, while there is a more complex relationship with the dimensionless center distance ϕ and dimensionless diameter ζ. When the values of ϕ and ζ are appropriate, Pn can reach its maximum value. The broken mode of compound droplets can be divided into three categories: shear deformation, shear crushing, and violent crushing.

A cognitive approach to concept of visualization in problem-solving

Any ball or small stone that is thrown follows a certain path. Many of us have experienced throwing objects towards a specific goal many times. If we throw a ball to someone or against something, the ball will follow a certain path, a visualized motion. Hopefully you can imagine a motion path if you are asked to throw something towards a target some 10 meters away. Somehow we can imagine the height and path in order to get the ball (or small stone) in the basket or what we are aiming at. If we want to shoot a basketball to go into the basket, we consider elevation angle and initial velocity also. Most of us humans do that without thinking about it.

An Algorithm for the Determination of Coronal Mass Ejection Kinematic Parameters Based on Machine Learning

Coronal mass ejections (CMEs) constitute the major source of severe space weather events, with the potential to cause enormous damage to humans and spacecraft in space. It is becoming increasingly important to detect and track CMEs, since there are more and more space activities and facilities. We have developed a new algorithm to automatically derive a CME’s kinematic parameters based on machine learning. Our method consists of three steps: recognition, tracking, and the determination of parameters. First, we train a convolutional neural network to classify images from Solar and Heliospheric Observatory Large Angle Spectrometric Coronagraph observations into two categories, containing CME(s) or not. Next, we apply the principal component analysis algorithm and Otsu’s method to acquire binary-labeled CME regions. Then, we employ the track-match algorithm to track a CME’s motion in time-series images and finally determine the CME’s kinematic parameters, e.g., velocity, angular width, and central position angle. The results of four typical CME events with different morphological characteristics are presented and compared with a manual CME catalog and several automatic CME catalogs. Our algorithm shows some advantages in the recognition of CME structure and the accuracy of the kinematic parameters. This algorithm can be helpful for real-time CME warnings and predictions. In the future, this algorithm is capable of being applied to CME initialization in magnetohydrodynamic simulations to study the propagation characteristics of real CME events and to provide more efficient predictions of CMEs’ geoeffectiveness.

Tracking Algorithm Application Integrating Visual and Radar Information in Intelligent Vehicle Target Tracking

Abstract With the continuous development of various automobile technologies, the concept of intelligent automobile automatic driving has been introduced into people's lives, and it has great research value in traffic safety, traffic efficiency, and other aspects. Intelligent vehicles can accurately identify and track the target vehicle, which is one of the important preconditions for safe driving. However, a single tracking algorithm is often used in traditional intelligent vehicles with a low tracking accuracy under adverse circumstances. To solve this problem, a fusion tracking algorithm combining visual tracking and radar tracking algorithm is proposed, and intelligent vehicle target-tracking technology is constructed based on the fusion algorithm. Through the performance comparison test, it was found that the fusion algorithm proposed in the study had the highest accuracy of 93% and the highest F measure of 0.98, both of which were superior to the comparison algorithm. Then, an empirical analysis is made of the target-tracking technology proposed in the study. The results showed that the error range of yaw angle velocity of the target vehicle was −0.48 to 0.36, and the maximum root-mean-square error of lateral and longitudinal distance of the target vehicle detected by the technology was 0.03, which was superior to other tracking technologies. To sum up, the intelligent vehicle target-tracking technology proposed in the research can improve the accuracy of intelligent vehicle target tracking and provide a guarantee for the safe driving of intelligent vehicles.

Asymmetric water entry of a wedged grillage structure investigated by CFD-FEM co-simulation

When a ship sails in ocean waves the relative movement between ship and wave is very complex. Slamming of bow or stern structures usually occurs in a manner of asymmetric oblique water entry. This implies that both the deflection angle θ and velocity angle α will likely grow to a large value at the same time. In this study, the hydrodynamics problem associated with the asymmetric and oblique water impact of a three-dimensional wedge is investigated using a partitioned CFD-FEM two-way coupled numerical tool by coupling the commercial software STAR-CCM+ and Abaqus within the framework of SIMULIA co-simulation engine. The hydrodynamic problem is solved by the CFD software using overset grid technique while the structural dynamic response is solved by the FEM software. Validation of the numerical results is conducted by using existing test results of symmetric water entry of the wedge first. Then the behaviours of movements, slamming pressure and structural response of the wedge structure during asymmetric water entry by varying the deflection angle θ or the velocity angle α or both are systematically and comparatively investigated. This research shows that the present numerical simulation well predicts both the fluid and structural dynamic characteristics such as fluid cavity and structural stress concentration of asymmetric impact problems, which has potential engineering application value in the field of ship design and slamming loads evaluation.

Experimental Study on Flow Characteristics of Oil-Water Two-Phase Flow in Single-Node Cross Fracture

Single-node cross fracture is the basic unit of discrete fracture network. In this paper, the flow characteristics of oil-water two-phase flow in single-node cross fracture model are investigated by experimental method. The model was divided into sixteen groups according to different angles, the oil and water phase flow rates were changed sequentially in each group and the velocity of oil and water phase were controlled to be in the low velocity flow rate range all the time during the experiment. The fluid flow process was recorded during the experiment by using the high-speed camera and the results were analyzed in detail. Under the condition of low velocity flow, oil-water two phases were slug flow in fracture. Effects of fracture crossing angle and oil-water phase velocity on the length of water section and the ratio of water-oil section length were also considered. The peristaltic pump speed is used instead of flow rate for the discussion, and the results show that for the same cross-fracture angle model, when the water pump speed is unchanged, the length of the water section gradually decreases in the form. of a power function with the increase of the speed of the oil pump. When the oil pump speed is unchanged, as the water pump speed increases, the length of water section increases in the form. of a linear function and the length ratio of wateroil section increases in the form. of the power function. Under different speeds of oil pump and water pump, the influence of fracture crossing angle on the length of water section and the length ratio of water-oil section is different.

AUV instantaneous velocity estimation method based on azimuth and Doppler shift

Autonomous underwater vehicle (AUV), as a new underwater operation platform, has been widely used in the field of ocean engineering. AUV underwater condition monitoring is an important guarantee for the safety and effective execution of AUV operations. To meet the requirement of real-time and high-precision underwater instantaneous velocity monitoring of AUV, this paper proposed an AUV instantaneous velocity estimation method. The method takes the target azimuth and Doppler shift as the observation information. It comprehensively uses the geometric relationship among the target azimuth, heading angle, radial velocity angle, and the physical relationship between Doppler and radial velocity to construct an AUV instantaneous velocity estimation model based on distributed dual acoustic observation nodes. We derive the analytical solution of AUV speed and heading angle and analyze the influence of each observation error on the estimation precision of the algorithm. The research and practical data processing results show that the proposed method can effectively estimate the instantaneous velocity of AUV. Compared with the traditional method based on position difference, it has the advantages of high estimation precision, is not limited by frame interval, and is adaptive to many kinds of motion modes. When AUV moves in a straight line at a uniform speed, the precision of speed estimation and heading angle estimation of the algorithm proposed in the paper is 0.506 m/s and 6.146°, which is equivalent to that of the traditional method based on position difference with 50 frame intervals.

Dynamic analysis on an asymmetric spatial dumbbell-type model

The structural symmetric breaking of the spatial structure will enhance the coupling dynamic behaviors and bring new challenges for the dynamic analysis on the spatial structure inevitably. The main contribution of this paper is proposing a structure-preserving iteration method to investigate the effects of the dynamic symmetry-breaking factors on the dynamic behaviors of the rigid-flexible coupling systems. Firstly, the spatial flexible damping beam assembled with two particles on both ends is simplified as an asymmetric spatial dumbbell-type model. For this model, the coupling dynamic equations are presented based on the Hamiltonian variational principle. Then, connecting the symplectic precise integration method for the ordinary differential equations mainly controlling the plane motion of the model and the generalized multi-symplectic scheme for the partial differential equation mainly controlling the transverse vibration of the beam, a structure-preserving numerical iteration method is proposed, which provides a new way to analysis the dynamic behaviors of the coupling problems with the symmetric breaking. Finally, the effects of the absolute mass and the mass ratio of the additional particles on the orbit radius, the orbit true anomaly velocity, the attitude angle velocity of the model and the transverse vibration of the flexible beam are reproduced by using the structure-preserving numerical iteration method in the numerical simulations. Particularly, the effects of the additional particles on the attitude stability of the model and the vibration dissipation of the flexible damping beam are investigated, which gives some guidance for the attitude adjustment strategy and the vibration control method for the spatial flexible structure with the structural symmetric breaking.

Aerosol deposition and emission from a United States Pharmacopeia‐induction port when using a pressurized metered‐dose inhaler with and without a valved holding chamber

AbstractThe testing of pharmaceutical aerosols includes measuring the aerodynamic particle size distribution, which is usually performed on cascade impactors. In the next generation impactor (NGI), the aerosol dose is introduced through an induction port (IP), being separated into different aerodynamic diameter ranges by seven stages and a micro‐orifice collector. The IP plays an important role in estimating the oropharyngeal deposition fraction. While the IP retains mainly large particles, it also tends to retain particles in the respirable range. In this work, the deposition of particles in the IP of an NGI is studied, both experimentally and through computational fluid dynamic (CFD) simulations. Experimental tests are conducted both with the pressurized metered‐dose inhaler (pMDI) alone and in conjunction with a cylindrical valved holding chamber (VHC). For each case, the total mass deposition that occurs in the VHC, IP, and NGI stages is measured, as well as the mass median aerodynamic diameter of the aerosol leaving the IP. The CFD simulations show minimal variations in results regardless of the injection method due to the relatively low velocity and spray angle of the pMDI‐generated aerosol. If the flap‐valve is removed from the VHC, significant particle deposition occurs upstream or within the valve region, with downstream air recirculation contributing to small particle deposition. Based on the CFD results, a correlation is proposed to accurately predict the particle escape fraction of the IP and VHC, which allows estimation of the tannin distribution of particles collected in the NGI stages, especially those corresponding to the range of respirable particles.

Design, Modeling, and Control of a Composite Tilt-Rotor Unmanned Aerial Vehicle

Tilt-rotor unmanned aerial vehicles combine the advantages of multirotor and fixed-wing aircraft, offering features like rapid takeoff and landing, extended endurance, and wide flight conditions. This article provides a summary of the design, modeling, and control of a composite tilt-rotor. During modeling process, aerodynamic modeling was performed on the tilting and non-tilting parts based on the subcomponent modeling method, and CFD simulation analysis was conducted on the entire unmanned aerial vehicle to obtain its accurate aerodynamic characteristics. In the process of modeling the motor propeller, the reduction of motor thrust and torque due to forward flow and tilt angle velocity is thoroughly examined, which is usually ignored in most tilt UAV propeller models. In the controller design, this paper proposes a fusion ADRC control strategy suitable for vertical takeoff and landing of this type of tiltrotor. The control system framework is built using Simulink, and the control algorithm’s efficiency has been verified through simulation testing. Through the proposed control scheme, it is possible for the composite tiltrotor unmanned aerial vehicle to smoothly transition between multirotor and fixed-wing flight modes.

Tensor improve equivariant graph neural network for molecular dynamics prediction

Molecular dynamics(MD) simulations are essential for molecular structure optimization, drug-drug interactions, and other fields of drug discovery by simulating the motion of microscopic particles to calculate their macroscopic properties (e.g., energy). The main problems of the existing work are as follows: (1) Failure to fully consider the chemical bonding constraints between atoms, (2) Group equivariance can help achieve robust and accurate predictions of MD under arbitrary reference transformations and should be incorporated into the model design, (3) Tensor information such as relative position, velocity, and torsion angle can be used to enhance the prediction of molecular dynamics. And the existing methods are mainly limited to the scalar domain.In this paper, we propose a new model—tensor improve equivariant graph neural network for molecular dynamics prediction (TEGNN): (1) The model materialization of chemical bond constraints between atoms into geometric constraints. The molecule’s forward kinematic information (position and velocity) is represented by generalized coordinates. In this way, the interatomic chemical bonding constraints are implicitly and naturally encoded in the forward kinematics, (2) The equivariant information transfer is allowed in TEGNN, which significantly improves the accuracy and computational efficiency of the final prediction, (3) TEGNN introduces equivariant locally complete frames into scalar-only equivariant graph neural networks, thus allowing the projection of tensor information of a given order onto the frame. On the N-body dataset of simulated molecular systems consisting of particles, sticks, and hinges, as well as on the real dataset MD17 for molecular dynamics prediction, multiple experiments support that TEGNN is ahead of the current state-of-the-art GNN in terms of prediction accuracy, constraint satisfaction, and data efficiency.We extend the current state-of-the-art equivariant neural network model. The proposed TEGNN accommodates more tensor information and considers the chemical bonding constraints between atoms during motion, ultimately improving the performance of predicting the kinematic states of molecules.

Approach and Landing Energy Prediction Based on a Long Short-Term Memory Model

The statistical analysis of civil aircraft accidents reveals that the highest incidence of mishaps occurs during the approach and landing stages. Predominantly, these accidents are marked by abnormal energy states, leading to critical situations like stalling and heavy landings. Therefore, it is of great significance to accurately predict the aircraft energy state in the approach and landing stages to ensure a safe landing. In this study, a deep learning method based on time sequence data for the prediction of the aircraft approach and landing energy states is proposed. Firstly, by conducting an extensive overview of the existing literature, three characteristic parameters of altitude, velocity, and glide angle were selected as the indicators to characterize the energy state. Following this, a semi-physical simulation platform for a certain type of aircraft was developed. The approach and landing experiments were carried out with different throttle sizes and flap deflection under different wind speeds and wind directions. Then, a deep learning prediction model based on Long Short-Term Memory (LSTM) was established based on the experimental data to predict the energy state indicators during the approach and landing phases. Finally, the established LSTM model underwent rigorous training and testing under different strategies, and a comparative analysis was carried out. The results demonstrated that the proposed LSTM model exhibited high accuracy and a strong generalization ability in predicting energy states during the approach and landing phases. These results offer a theoretical basis for designing energy early warning systems and formulating the relevant flight control laws in the approach and landing stages.

Energy loss analysis in cavitation flow of a continuous-resistance trim

Energy loss is generated by phase transition and work done on the continuous-resistance trim (CRT) in cavitation flow. This study aims to explore an enhanced CRT design to minimize energy loss in cavitation flow. Four key parameters, specifically orifice shape, inlet velocity, aperture and tilt angle, which have been proven to impact flow in CRT, are examined using a validated numerical method to assess their effects on energy loss in cavitation flow. Furthermore, based on a parametric sensitivity study, an improved design is proposed to control cavitation and reduce energy loss. Findings indicate that changes in orifice shape notably influence the flow area and throttling effect, which are closely connected to energy loss in cavitation. A critical inlet velocity of v1/v0 = 0.5 triggers cavitation occurrence. An orthogonal design method employing L16(45) array is used to analyze the effects of apertures, resulting in the identification of a preferred group with lower energy loss. A larger tilt angle β1/β0 effectively suppresses cavitation generation and significantly decreases energy loss. Finally, an enhanced CRT design is proposed, incorporating a circular (chamfer) orifice shape, an inlet velocity of v1/v0 = 0.3, the preferred aperture group (No.1), and a tilt angle of β1/β0 = 0.66, this improved design showcases reduced energy loss compared to the original CRT design. The findings of this study have broad applications in guiding the implementation of throttling components to suppress cavitation and minimize energy loss.

Development of machine learning models for the prediction of erosion wear of hybrid composites

AbstractThis article reports on development of an adaptive framework for predicting the erosion performance of polymer composites using certain statistical and machine learning (ML) models. For this, ramie‐epoxy composites reinforced with variations (0–30 wt%) of sponge iron slag (an iron industry waste) are considered. The composites are fabricated and then subjected to high temperature solid particle erosion wear trials following Taguchi's L27 orthogonal array. The effects of different control factors on the erosion rate in an interactive environment are appraised by analysis of variance (ANOVA) which reveals the filler content as the most significant factor contributing 66.21%, followed by impact velocity (22.86%) and impingement angle (2.28%). A regression model based on the input–output parameters obtained from experimentation is constructed for prediction of erosion rate. Further, four predictive models using different machine learning algorithms are also proposed to predict the erosion rate of the composites. The feasibility and performance of each ML model is assessed using appropriate performance metrics. Among all the models, the gradient boosting machine model is found to be the most reliable model exhibiting the highest prediction accuracy and least errors.Highlights Development of novel class of composites reinforced with sponge iron slag. Database creation based on erosion wear experimentation on the composites. Data‐driven modeling for prediction of erosion rates using machine learning. Comparison of performance of different models and identifying the best one.

Evaluation of Streamline on Aerofoil with Suction Hole in Wind Tunnel

This study looks into the impact of pressure suction holes in the NACA 0012 airfoil on aerodynamic performance. The goal is to use wind tunnel tests to compute the lift and drag forces for the NACA 0012 airfoil with suction holes at various air speeds and angles of attack. The relationship between air speed, angle of attack, drag coefficient, and lift coefficient will be determined by analysing the obtained data. The goal of the research is to better understand the flow patterns and variations in streamlines of the NACA 0012 airfoil at different velocity and attack angles. The test model will use the NACA 0012 airfoil, which is recognised for its symmetrical shape. Suction holes, varying from one to four, will be installed to provide insight into the influence of pressure suction on the boundary layer and streamline behaviour of the airfoil. The study will be carried out in a low-speed wind tunnel within the Fluid Mechanics laboratory, with the streamlines visualised using a smoke generator. This study is significant because it contributes to our understanding of flow characteristics, pressure distributions, and boundary layer control in aerodynamic design. It also provides excellent exposure to wind tunnel testing procedures, aviation industry practises, and continuing airfoil design research. This study adds to the body of knowledge on optimising airfoil performance by evaluating the effect of pressure suction holes on the NACA 0012 airfoil. The findings will be useful to researchers, aerodynamic enthusiasts, and aviation experts, allowing them to further investigate the potential benefits of pressure suction techniques in improving airfoil efficiency and performance.

Cavitation Erosion Investigations of Hard Carbide and Nitride Based Novel Coatings Manufactured by Plasma Spraying

Cavitation erosion (CE) poses a significant challenge in the operation and maintenance of hydropower turbines, leading to substantial economic and operational losses. This study addresses this issue by investigating the effectiveness of plasma-sprayed coatings in mitigating CE on SS316 steel. Si3N4+TiC + VC and Cr-Ni based coatings were applied using a plasma spraying process. The research encompasses a comprehensive analysis of the coatings’ characteristics, including microhardness, surface roughness, porosity percentage, and coating thickness. Furthermore, CE tests were conducted under various conditions, considering factors such as impingement angle, stand-off distance, and jet velocity. The eroded surfaces were analyzed using scanning electron microscopy (SEM) to gain insights into the failure modes. The findings demonstrate that the Si3N4+TiC + VC and Cr-Ni based coatings significantly enhance the resistance of SS316 steel to CE.

Finite element modeling of the rotational dynamics of a single magnetic particle in a strong magnetic field and liquid medium

We have performed a comparative computational study of magnetic particle alignment in a strong magnetic field and ambient viscous fluid using the first-principles Navier–Stokes equation as well as numerical modeling using the finite element method (FEM). FEM solution has been compared with the solution of the unsteady rotations of a magnetic particle in a viscous fluid during the alignment process described with nonlocal integro-differential equations (IDEs) for torque and angular velocity. The assumption of nonlocality comes from the history term of acceleration torque with a non-Basset kernel function, which has its origin in the presence of vortices in the flow of a particle fluid environment due to its unsteady rotation and ambient fluid inertia and friction. The flow vortices of the ambient fluid are explicitly shown in the solution of the FEM model. Moreover, the solution of the time evolution of the alignment angle and angular velocity for the FEM model are in good agreement with an IDE model which we have recently developed. The obtained results are justification for interchangeability of the FEM and IDE models, which may have important consequences for large-scale simulations of magnetic microparticles.

Effect and mechanism of erosion in Pelton turbine and case studies—A review

Pelton turbines are widely used in hydropower stations located in mountainous regions, especially with water head drop of more than 2000 m. Due to the complex structure and working principle of the turbine, the flow is more complicated than reaction turbines, making the numerical simulation more difficult. The impulse action causes the occurrence of erosion phenomena in Pelton turbines, which will directly decrease the hydraulic efficiency and reduce the turbine's life. For investigating the erosion characteristics, computational fluid dynamics is widely used on variegated platforms according to their unique advantage. Thus, different platforms are introduced and compared in solving the multi-phase flow using a discrete element method or the other meshless methods. In addition, the erosion mechanism is studied and classified in different aspects such as impact angle and impact velocity. However, unlike the feasibility of numerical simulations, experimental work on the erosion mechanism is still challenging to reproduce. Furthermore, the state of experimental research is discussed by listing the various major facilities in operation and comparing their methods of experimental analysis. Case studies all over the world provide a very rich database of erosion patterns which would be highly useful in validation and verification of simulation and experimental results. Studies have shown that particle parameters, such as size, concentration, shape, velocity, and the interaction between particles and material surfaces, significantly impact the erosion of Pelton turbines. In response to this erosion, upgrading materials and implementing geometric optimization have proven to be effective strategies.