scholarly journals Six-DOF CFD Simulations of Underwater Vehicle Operating Underwater Turning Maneuvers

2021 ◽  
Vol 9 (12) ◽  
pp. 1451
Author(s):  
Kunyu Han ◽  
Xide Cheng ◽  
Zuyuan Liu ◽  
Chenran Huang ◽  
Haichao Chang ◽  
...  
Keyword(s):  
Great Influence ◽  
Underwater Vehicle ◽  
The Body ◽  
Body Motion ◽  
Thrust Distribution ◽  
Turning Motion ◽  
Computational Fluid Dynamics Cfd ◽  
Six Dof ◽  
Cfd Method ◽  
Multi Body

Maneuverability, which is closely related to operational performance and safety, is one of the important hydrodynamic properties of an underwater vehicle (UV), and its accurate prediction is essential for preliminary design. The purpose of this study is to analyze the turning ability of a UV while rising or submerging; the computational fluid dynamics (CFD) method was used to numerically predict the six-DOF self-propelled maneuvers of submarine model BB2, including steady turning maneuvers and space spiral maneuvers. In this study, the overset mesh method was used to deal with multi-body motion, the body force method was used to describe the thrust distribution of the propeller at the model scale, and the numerical prediction also included the dynamic deflection of the control planes, where the command was issued by the autopilot. Then, this study used the published model test results of the tank to verify the effectiveness of the CFD prediction of steady turning maneuvers, and the prediction of space spiral maneuvers was carried out on this basis. The numerical results show that the turning motion has a great influence on the depth and pitch attitude of the submarine, and a “stern heavier” phenomenon occurs to a submarine after steering. The underwater turning of a submarine can not only reduce the speed to brake but also limit the dangerous depth. The conclusion is of certain reference significance for submarine emergency maneuvers.

Nordic walking multibody analysis and experimental identification

2020 ◽  
pp. 175433712091926
Author(s):  
Caterina Russo ◽  
Francesco Mocera ◽  
Aurelio Somà
Keyword(s):  
Reaction Force ◽  
Standard Technique ◽  
The Body ◽  
Body Motion ◽  
Body Segment ◽  
Nordic Walking ◽  
Cycle Frequency ◽  
Experimental Identification ◽  
Body Model ◽  
Multi Body

The widespread diffusion of Nordic walking as a trending sport discipline has increased the need for a tool to study the movement, both at the beginner and professional level. This article presents a methodology for the analysis of the body motion during Nordic walking. The main goal was to design a numerical tool able to replicate human body behaviour when performing this sport. With this approach, it is possible to study several biomechanical aspects, like the kinematics of each body segment, estimating loads applied to the joints for given tasks. Results can be used to compare the user movements with a standard technique implemented in the virtual environment. In fact, using a specific monitoring device developed in previous works, different parameters like the pole angle, arms cycle frequency and synchronization, as well as the pushing force applied to the ground, can be measured during the activity. This acquisition system can be used to save data to be compared with results from the standard numerical model, evaluating the user performance. In this work, numerical results were compared and discussed with measurements from the aforementioned device in terms of pole force and pole angle. The ground reaction force obtained with the multi-body model during Nordic walking was then compared with results from the literature.

scholarly journals Aerodynamics of Cycling Skinsuits Focused on the Surface Shape of the Arms

2021 ◽  
Vol 11 (5) ◽  
pp. 2200
Author(s):  
Sungchan Hong ◽  
Takeshi Asai
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Experiment ◽  
The Body ◽  
Surface Shape ◽  
Air Resistance ◽  
Computational Fluid Dynamics Cfd ◽  
Race Conditions ◽  
Cfd Method ◽  
Fabric Surface ◽  
Full Body

In cycling, air resistance corresponds to 90% of the resistance on the bicycle and cyclist and 70% of this is applied to the body of the cyclist. Despite research on postures that could reduce air resistance, few studies have been conducted on full-body cycling suits. As the aerodynamics of the surface shape of clothing fabric are still unclear, the airflow around cyclists and air resistance were examined using a computational fluid dynamics (CFD) method and wind tunnel experiment. Specifically, in this study, we focused on how different surface shapes of cycling suit fabrics affect air resistance. CFD results indicate that air resistance during a race was high at the head, arms and legs of the cyclist. In the wind tunnel experiment, a cylinder model resembling the arms was used to compare the aerodynamic forces of various fabrics and the results showed that air resistance changed according to the fabric surface shape. Moreover, by changing the fabric shape of the arms of the cycling suits, reduction of air resistance by up to 8% is achievable. These results suggest that offering the most appropriate suit type to each cyclist, considering race conditions, can contribute to further improvement in their performance.

scholarly journals Estimation of car air resistance by CFD method

2014 ◽  
Vol 36 (3) ◽  
pp. 235-244 ◽  
Author(s):  
Phan Anh Tuan ◽  
Vu Duy Quang
Keyword(s):  
Fluid Dynamics ◽  
Surface Area ◽  
Rolling Resistance ◽  
The Body ◽  
Ansys Fluent ◽  
Car Body ◽  
Air Resistance ◽  
Implicit Solver ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

Total car resistance is including rolling resistance and air resistance. Rolling resistance comes from car tires when it rolls over the roads with car weight. Air resistance comes from the body when it moves in the air with car body surface area. The air resistance of a car depends upon its shape. The bigger the surface area of a car body, the more air molecules the car will hit and so the larger the air resistance. This paper will mention to estimation of car air resistance by computational fluid dynamics (CFD) method. A 3D car body has used for simulation in ANSYS FLUENT CFD software. The k-\(\varepsilon\) turbulence model and segregated implicit solver was used to perform computation in this study.

An Exploration of a PASSIVE Articulated Fish-Like System

2013 ◽  
Author(s):  
Jianxin Hu ◽  
Qing Xiao ◽  
Vinh Tan Nguyen
Keyword(s):  
Degrees Of Freedom ◽  
Muscle Force ◽  
The Self ◽  
Body System ◽  
Multiple Degrees Of Freedom ◽  
Propulsion Mechanism ◽  
Articulated Model ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Multi Body

This study is aimed to investigate the bio-mimetic swimmer propulsion mechanism with the use of its internal muscle force. A simplified articulated model, with multiple rigid segments connected by the joints (imitating the muscle force), is adopted to represent the real swimmer body. To modeling the problem, a Computational Fluid Dynamics (CFD) method is coupled with the system dynamic equations. Some preliminary results obtained showed that the numerical methods developed are able to predict the self-propelled articulated multi-body system with multiple degrees of freedom.

scholarly journals Numerical and Experimental Investigation of Oil-Guiding Splash Lubrication in Light Helicopter’s Reducers

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 345
Author(s):  
Mei Yin ◽  
Xi Chen ◽  
Yu Dai ◽  
Duan Yang ◽  
Lanjin Xu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Investigation ◽  
Great Influence ◽  
Test Rig ◽  
Specific Test ◽  
Rotating Speed ◽  
Lubrication Performance ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Oil Jet

Limited by the space and weight of the reducer, it is difficult to use traditional oil-jet lubrication and splash lubrication for a light helicopter, so an oil-guiding splash lubrication method is adopted as a research object in this paper. Firstly, the lubrication performance of the oil-guiding cylinder in the main reducer under different rotating speeds, oil levels, and flight attitudes is investigated based on the computational fluid dynamics (CFD) method. Then, a specific test rig is developed, and lubrication tests are carried out to verify the feasibility and correctness of the simulation. These results show that oil level, rotating speed, and flight attitude have a great influence on splash lubrication performance.

Chaos in body–vortex interactions

2010 ◽  
Vol 466 (2119) ◽  
pp. 1871-1891 ◽  
Author(s):  
Johan Roenby ◽  
Hassan Aref
Keyword(s):  
Body Shape ◽  
Mass Density ◽  
Relative Equilibrium ◽  
Large Body ◽  
Point Vortex ◽  
Cylindrical Body ◽  
The Body ◽  
Body Motion ◽  
Single Vortex ◽  
Vortex Interactions

The model of body–vortex interactions, where the fluid flow is planar, ideal and unbounded, and the vortex is a point vortex, is studied. The body may have a constant circulation around it. The governing equations for the general case of a freely moving body of arbitrary shape and mass density and an arbitrary number of point vortices are presented. The case of a body and a single vortex is then investigated numerically in detail. In this paper, the body is a homogeneous, elliptical cylinder. For large body–vortex separations, the system behaves much like a vortex pair regardless of body shape. The case of a circle is integrable. As the body is made slightly elliptic, a chaotic region grows from an unstable relative equilibrium of the circle-vortex case. The case of a cylindrical body of any shape moving in fluid otherwise at rest is also integrable. A second transition to chaos arises from the limit between rocking and tumbling motion of the body known in this case. In both instances, the chaos may be detected both in the body motion and in the vortex motion. The effect of increasing body mass at a fixed body shape is to damp the chaos.

scholarly journals Self-rechargeable cardiac pacemaker system with triboelectric nanogenerators

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hanjun Ryu ◽  
Hyun-moon Park ◽  
Moo-Kang Kim ◽  
Bosung Kim ◽  
Hyoun Seok Myoung ◽  
...  
Keyword(s):  
Medical Devices ◽  
Mechanical Energy ◽  
Cardiac Pacemaker ◽  
Operation Time ◽  
Lithium Ion ◽  
The Body ◽  
Body Motion ◽  
Triboelectric Nanogenerator ◽  
Implantable Medical Devices ◽  
Energy Harvesters

AbstractSelf-powered implantable devices have the potential to extend device operation time inside the body and reduce the necessity for high-risk repeated surgery. Without the technological innovation of in vivo energy harvesters driven by biomechanical energy, energy harvesters are insufficient and inconvenient to power titanium-packaged implantable medical devices. Here, we report on a commercial coin battery-sized high-performance inertia-driven triboelectric nanogenerator (I-TENG) based on body motion and gravity. We demonstrate that the enclosed five-stacked I-TENG converts mechanical energy into electricity at 4.9 μW/cm3 (root-mean-square output). In a preclinical test, we show that the device successfully harvests energy using real-time output voltage data monitored via Bluetooth and demonstrate the ability to charge a lithium-ion battery. Furthermore, we successfully integrate a cardiac pacemaker with the I-TENG, and confirm the ventricle pacing and sensing operation mode of the self-rechargeable cardiac pacemaker system. This proof-of-concept device may lead to the development of new self-rechargeable implantable medical devices.

Analysis of Hydrodynamic Characteristics in the Process of Autonomous Underwater Vehicle Docking

2015 ◽  
Author(s):  
Xiaoxu Du ◽  
Huan Wang
Keyword(s):  
Drag Coefficient ◽  
Autonomous Underwater Vehicle ◽  
Simple Algorithm ◽  
Underwater Vehicle ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Successful Operation ◽  
Underwater Docking ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

The successful operation of an Autonomous Underwater Vehicle (AUV) requires the capability to return to a dock. A number of underwater docking technologies have been proposed and tested in the past. The docking allows the AUV to recharge its batteries, download data and upload new instructions, which is helpful to improve the working time and efficiency. During the underwater docking process, unsteady hydrodynamic interference occurs between the docking device and an AUV. To ensure a successful docking, it is very important that the underwater docking hydrodynamics of AUV is understood. In this paper, numerical simulations based on the computational fluid dynamics (CFD) solutions were carried out for a 1.85m long AUV with maximum 0.2 m in diameter during the docking process. The two-dimensional AUV model without fin and rudder was used in the simulation. The mathematical model based on the Reynolds-averaged Navier-Stokes (RANS) equations was established. The finite volume method (FVM) and the dynamic structured mesh technique were used. SIMPLE algorithm and the k-ε turbulence model in the Descartes coordinates were also adopted. The hydrodynamics characteristics of different docking states were analyzed, such as the different docking velocity, the docking device including baffle or not. The drag coefficients of AUV in the process of docking were computed for various docking conditions, i.e., the AUV moving into the docking in the speed of 1m/s, 2m/s, 5m/s. The results indicate that the drag coefficient increases slowly in the process of AUV getting close to the docking device. When the AUV moves into the docking device, the drag coefficient increases rapidly. Then the drag coefficient decreases rapidly. The drag coefficient decreases with the increase of velocity when AUV enters the docking device. It was also found that the drag coefficient can be effectively reduced by dislodging the baffle of docking device.

A Parametric Study of Low-Frequency Damping of Mooring System

2014 ◽  
Author(s):  
Minglu Chen ◽  
Shan Huang ◽  
Nigel Baltrop ◽  
Ji Chunyan ◽  
Liangbi Li
Keyword(s):  
Low Frequency ◽  
Structure Design ◽  
The Body ◽  
Body Motion ◽  
Mooring Line ◽  
Offshore Structure ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
Line System ◽  
Irregular Wave

Mooring line damping plays an important role to the body motion of moored floating platforms. Meanwhile, it can also make contributions to optimize the mooring line system. Accurate assessment of mooring line damping is thus an essential issue for offshore structure design. However, it is difficult to determine the mooring line damping based on theoretical methods. This study considers the parameters which have impact on mooring-induced damping. In the paper, applying Morison formula to calculate the drag and initial force on the mooring line, its dynamic response is computed in the time domain. The energy dissipation of the mooring line due to the viscosity was used to calculate mooring-induced damping. A mooring line is performed with low-frequency oscillation only, the low-frequency oscillation superimposed with regular and irregular wave-frequency motions. In addition, the influences of current velocity, mooring line pretension and different water depths are taken into account.

An anti-crystallization design of selective catalytic reduction nozzle holder

2021 ◽  
pp. 095440702097084
Author(s):  
Dewen Liu ◽  
Kai Lu ◽  
Shusen Liu ◽  
Yan Wu ◽  
Shuzhan Bai
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Injection System ◽  
Test Results ◽  
Verification Methods ◽  
Crystallization Risk ◽  
Protective Cover ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Good Agreement

From the aspect of reducing the risk of crystallization on nozzle surface, a new design of nozzle protective cover was to solve the problem in selective catalytic reduction (SCR) urea injection system. The simulation calculation and experimental verification methods were used to compare different schemes. The results show that reducing the height of nozzle holder can reduce the vortex currents near nozzle surface and effectively reduce the risk of crystallization on the nozzle surface. It is proposed to install a protective cover in the nozzle holder under the scheme of reducing the height of nozzle holder, which can further eliminate the vortex. Simulation and test results demonstrate good agreement under the rated running condition. The scheme of adding a protective cover in the nozzle holder shows the least crystallization risk by computational fluid dynamics (CFD) method. The crystallization cycle test shows that, after the height of nozzle holder is reduced, the risk of crystallization on the nozzle surface is reduced correspondingly. The addition of a protective cover in the nozzle holder solves the problem of crystallization on the nozzle surface, which provides a new method for anti-crystallization design.

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