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.

Study of Self-Propelled Pufferfish Driven by Multiple Fins: A Comparison Between Rigid and Deformable Fins

2017 ◽  
Author(s):  
Ruoxin Li ◽  
Qing Xiao ◽  
Lijun Li ◽  
Hao Liu
Keyword(s):  
Underlying Mechanism ◽  
Operating Conditions ◽  
The Self ◽  
Fish Swimming ◽  
Propulsion Efficiency ◽  
Live Fish ◽  
Body Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Multi Body ◽  
Better Than

In this work, we numerically studied the steady swimming of a pufferfish driven by the undulating motion of its dorsal, anal and caudal fins. The simulations are based on experimentally measured kinematics. To model the self-propelled fish swimming, a Computational Fluid Dynamics (CFD) tool was coupled with a Multi-Body-Dynamics (MBD) technique. It is widely accepted that deformable/flexible or undulating fins are better than rigid fins in terms of propulsion efficiency. To elucidate the underlying mechanism, we established an undulating fins model based on the kinematics of live fish, and conducted a simulation under the same operating conditions as rigid fins. The results presented here agree with this view by showing that the contribution of undulating fins to propulsion efficiency is significantly larger than that of rigid fins.

Prediction of Resistance and Self-Propulsion Characteristics of a Full-Scale Naval Ship by CFD-Based GEOSIM Method

2020 ◽  
pp. 1-16 ◽  
Author(s):  
Cihad Delen ◽  
Ugur Can ◽  
Sakir Bal
Keyword(s):  
Degrees Of Freedom ◽  
Full Scale ◽  
The Self ◽  
Body Motion ◽  
Ship Motions ◽  
Naval Research ◽  
Propulsion Performance ◽  
Office Of Naval Research ◽  
Naval Ship ◽  
Computational Fluid Dynamics Cfd

Resistance and self-propulsion characteristics of a naval ship at full scale have been investigated by using Telfer’s GEOmetrically SIMilar (GEOSIM) method based on the computational fluid dynamics (CFD) approach. For this purpose, first, the resistance forces of the Office of Naval Research Tumblehome (ONRT) hull have been computed at different three model scales by using the overset mesh technique. The full-scale resistance and nominal wake fraction of the ONRT hull have been estimated by using Telfer’s GEOSIM method. Resistance and nominal wake fraction have then been compared with those of CFD at full scale. Later, the self-propulsion characteristics of the ONRT hull have been examined using Telfer’s GEOSIM method based on the CFD approach. Self-propulsion factors at the full-scale hull have been predicted by using the SST k-ω turbulence model to involve 2-degrees of freedom ship motions (heave and pitch). Rotational motion of the propeller has also been simulated by using the rigid body motion technique. The results calculated by Telfer’s GEOSIM method and the 1978 International Towing Tank Conference (ITTC) extrapolation technique have been compared with each other and discussed with those of the CFD approach at full scale. It was found that the full-scale results (both resistance and self-propulsion factors) predicted by Telfer’s GEOSIM method are closer to those of the CFD approach than those of the 1978 ITTC technique. It can be noted that Telfer’s GEOSIM method is fast, robust, and reliable and can be used as an alternative to the 1978 ITTC method for predicting the self-propulsion performance of a full-scale ship.

A Fast Sea-Keeping Simulation Method for Heavy-Lift Operations Based on Multi-Body System Dynamics

2014 ◽  
Author(s):  
Hannes Hatecke ◽  
Stefan Krüger ◽  
Jakob Christiansen ◽  
Hendrik Vorhölter
Keyword(s):  
Degrees Of Freedom ◽  
Simulation Method ◽  
Suspended Load ◽  
Body System ◽  
Lagrange Equations ◽  
Six Degrees Of Freedom ◽  
Time Motion ◽  
Heavy Lift ◽  
Freely Suspended ◽  
Multi Body

This paper presents a fast numerical method to analyze heavy-lift operations of ships in short crested waves. For this purpose, a sea-keeping simulation method for the coupled motions of a heavy-lift vessel and a freely suspended load is developed. The method considers the motions of the ship in six degrees-of-freedom and the suspended load as a point mass. The coupling of the multi-rigid-body system of the ship and the suspended load is considered by solving the equation of roll motion together with the Euler-Lagrange equations of the load. This approach allows the simulation of several hours of real time motion in short crested waves within only a few seconds. Consequently, the method is particularly suitable when very long or numerous sea-keeping simulations or statistical results are required. Moreover, the method is applied to evaluate the sea-keeping capabilities of a heavy-lift vessel during a lifting operation conducted offshore in 2013.

scholarly journals COMPARISON OF STANDARD k-epsilon AND SST k-omega TURBULENCE MODEL FOR BREASTSHOT WATERWHEEL SIMULATION

2020 ◽  
Vol 7 (2) ◽  
pp. 039-044
Author(s):  
Dendy Adanta ◽  
I. M. Rizwanul Fattah ◽  
Nura Musa Muhammad
Keyword(s):  
Turbulence Model ◽  
Degrees Of Freedom ◽  
Physical Phenomenon ◽  
Geometry Optimization ◽  
Turbulence Models ◽  
Turbulent Model ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Physical Phenomena ◽  
Omega Model

Currently, Computational Fluid Dynamics (CFD) was utilized to predict the performance, geometry optimization or physical phenomena of a breastshot waterwheel. The CFD method requires the turbulent model to predict the turbulent flow. However, until now there is special attention on the effective turbulent model used in the analysis of breastshot waterwheel. This study is to identify the suitable turbulence model for a breatshot waterwheel. The two turbulence models investigated are: standard k-epsilon model and shear stress transport (SST) k-omega. Pressure based and one degrees of freedom (one-DoF) feature was used in this case with  75 Nm, 150 Nm, 225 Nm and 300 Nm as preloads. Based on the results, the standard k-epsilon model gave similar result with the SST k-omega model. Therefore, the simulation for breastshot waterwheel will be efficient if using the standard k-epsilon model because it requires lower computational power than the SST k-omega model. However, to study about physical phenomenon, the SST k-omega model is recommend.

scholarly journals Advanced computational fluid dynamics (CFD)–multi-body simulation (MBS) coupling to assess low-frequency emissions from wind turbines

2018 ◽  
Vol 3 (2) ◽  
pp. 713-728 ◽  
Author(s):  
Levin Klein ◽  
Jonas Gude ◽  
Florian Wenz ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Degrees Of Freedom ◽  
Structural Model ◽  
Low Frequency ◽  
Cfd Model ◽  
Computational Fluid Dynamics Cfd ◽  
Multi Body

Abstract. The low-frequency emissions from a generic 5 MW wind turbine are investigated numerically. In order to regard airborne noise and structure-borne noise simultaneously, a process chain is developed. It considers fluid–structure coupling (FSC) of a computational fluid dynamics (CFD) solver and a multi-body simulations (MBSs) solver as well as a Ffowcs-Williams–Hawkings (FW-H) acoustic solver. The approach is applied to a generic 5 MW turbine to get more insight into the sources and mechanisms of low-frequency emissions from wind turbines. For this purpose simulations with increasing complexity in terms of considered components in the CFD model, degrees of freedom in the structural model and inflow in the CFD model are conducted. Consistent with the literature, it is found that aeroacoustic low-frequency emission is dominated by the blade-passing frequency harmonics. In the spectra of the tower base loads, which excite seismic emission, the structural eigenfrequencies become more prominent with increasing complexity of the model. The main source of low-frequency aeroacoustic emissions is the blade–tower interaction, and the contribution of the tower as an acoustic emitter is stronger than the contribution of the rotor. Aerodynamic tower loads also significantly contribute to the external excitation acting on the structure of the wind turbine.

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.

Dynamic Performance of High-Speed Electric Multiple Unit within Multi-Body System Simulation

2019 ◽  
Vol 12 (4) ◽  
pp. 339-349
Author(s):  
Junguo Wang ◽  
Daoping Gong ◽  
Rui Sun ◽  
Yongxiang Zhao
Keyword(s):  
High Speed ◽  
Rapid Development ◽  
Dynamic Performance ◽  
Body System ◽  
High Speed Railway ◽  
Evaluation Indexes ◽  
Actual Operation ◽  
Multiple Unit ◽  
The Stability ◽  
Multi Body

Background: With the rapid development of the high-speed railway, the dynamic performance such as running stability and safety of the high-speed train is increasingly important. This paper focuses on the dynamic performance of high-speed Electric Multiple Unit (EMU), especially the dynamic characteristics of the bogie frame and car body. Various patents have been discussed in this article. Objective: To develop the Multi-Body System (MBS) model of EMU, verify whether the dynamic performance meets the actual operation requirements, and provide some useful information for dynamics and structural design of the proposed EMU. Methods: According to the technical characteristics of a typical EMU, a MBS model is established via SIMPACK, and the measured data of China high-speed railway is taken as the excitation of track random irregularity. To test the dynamic performance of the EMU, including the stability and safety, some evaluation indexes such as wheel-axle lateral forces, wheel-axle lateral vertical forces, derailment coefficients and wheel unloading rates are also calculated and analyzed in detail. Results: The MBS model of EMU has better dynamic performance especially curving performance, and some evaluation indexes of the stability and safety have also reached China’s high-speed railway standards. Conclusion: The effectiveness of the proposed MBS model is verified, and the dynamic performance of the MBS model can meet the design requirements of high-speed EMU.

scholarly journals Design, Fabrication, and Testing of a Novel 3D 3-Fingered Electrothermal Microgripper with Multiple Degrees of Freedom

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 444
Author(s):  
Guoning Si ◽  
Liangying Sun ◽  
Zhuo Zhang ◽  
Xuping Zhang
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Polyimide Film ◽  
Zebrafish Embryos ◽  
Multiple Degrees Of Freedom ◽  
Electrothermal Actuator ◽  
3D Space ◽  
Pick And Place

This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space.

scholarly journals Impact of Increased Travel Speed of a Transportation Set on the Dynamic Parameters of a Mine Suspended Monorail

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1528
Author(s):  
Kamil Szewerda ◽  
Jarosław Tokarczyk ◽  
Andrzej Wieczorek
Keyword(s):  
Computational Model ◽  
Travel Speed ◽  
Body System ◽  
Emergency Braking ◽  
System Method ◽  
Underground Coal Mines ◽  
Program Environment ◽  
Underground Transportation ◽  
Multi Body ◽  
Transportation Routes

The method of increasing the efficiency of using one of the most common means of auxiliary transport in underground coal mines—suspended monorails—is presented. Increase of velocity is one of the key parameters to improve the efficiency and economical effect related with the underground auxiliary transport. On the other hand, increasing the velocity results in bigger value of force acting on the suspended monorail route and its suspensions. The most important issue during increasing the velocity is ensuring the required safety for the passengers and not overloading the infrastructure. In order to analyze how increasing velocity influences the level of loads of the route suspension and the steel arch loads, the computational model of suspended monorail was developed. The computational model included both the physical part (embedded in the program environment based on the Multi-Body System method) and the components of the monorail control system. Two independent software environments were cooperating with each other through the so-called co-simulation. This model was validated on the base of results obtained on the test stand. Then, the numerical simulations of emergency braking with different values of velocity were conducted, which was not possible with the use of physical objects. The presented study can be used by the suspended monorail’s producers during the designing process, and leads to increase the safety on underground transportation routes.

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