Adaptive obstacle climbing and hydrodynamic performance analyses of the amphibious robot with wheels and flexible undulating fins

2022 ◽  
pp. 095440622110590
Author(s):  
Qian Yin ◽  
Minghai Xia ◽  
Zirong Luo ◽  
Jianzhong Shang
Keyword(s):  
Swimming Performance ◽  
Industrial Applications ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Experimental Measurements ◽  
Underwater Propulsion ◽  
Performance Analyses ◽  
The Difference ◽  
Amphibious Robot ◽  
Undulating Fin

In this paper, an amphibious robot with flexible undulating fins and self-adaptive climbing wheels are proposed for satisfying the needs of industrial applications. The structure of the climbing mechanism and undulating fin are firstly designed. Then, the adaptive obstacle climbing and the hydrodynamic characteristics are investigated through numerical simulations by using the Adams and Fluent, respectively. Finally, the experimental measurements of the land walking and underwater propulsion are studied. The numerical results illustrate that the amphibious robot could climb the vertical obstacle adaptively. In the underwater marching pattern, the underwater velocity could reach 1 m/s. In the rotating and yawing patterns, the angular velocity increases to the certain value while the rotating angle keeps increasing. The robot moves forward and turns around with the difference frequency of the undulating fins. The underwater propulsion and land-walking experiments show good swimming performance and the obstacle crossing ability of the amphibious robot, respectively, which verify the numerical simulation.

scholarly journals Experimental research and floating gait planning of crablike robot

2020 ◽  
Vol 12 (2) ◽  
pp. 168781402090485
Author(s):  
Hai-Long Wang ◽  
Xing-Ya Yan ◽  
Gang Wang ◽  
Qi-Feng Zhang ◽  
Qi-Yan Tian ◽  
...  
Keyword(s):  
Water Resistance ◽  
Swimming Performance ◽  
Hydrodynamic Performance ◽  
Portunus Trituberculatus ◽  
Swimming Velocity ◽  
Force Analysis ◽  
Gait Planning ◽  
Propulsion Mechanism ◽  
Underwater Propulsion ◽  
Structure Scheme

In order to improve the swimming performance of a paddle-propelled crablike robot, the sequence and parameters of swimming gait are planned according to the bionic swimming mechanism. Based on the bionic prototype of Portunus trituberculatus, the structure scheme of a leg–paddle hybrid driven robot is proposed with the functions of walking on land, crawling on seabed, and swimming underwater. By analyzing the underwater propulsion mechanism of single paddle and hydrodynamic performance of double paddles cooperatively propulsion, four direct swimming gaits are planned and the corresponding attitude changes are theoretically analyzed. Then, the numerical simulation and direct swimming experiments are carried out to verify the effectiveness of proposed gaits and correctness of force analysis. In alternate swimming gait of lift-based mode, the robot swims forward in a rolling attitude, with an advantage of the minimum water resistance and the optimum swimming velocity and efficiency. The influence of flapping frequency and relative phases of paddles on the swimming velocity shows the trend of raise first and then fall.

Study of pumping effect in flow-through electrolysers

1983 ◽  
Vol 48 (8) ◽  
pp. 2232-2248 ◽  
Author(s):  
Ivo Roušar ◽  
Michal Provazník ◽  
Pavel Stuhl
Keyword(s):  
Natural Convection ◽  
Balance Equation ◽  
Volume Fraction ◽  
Industrial Applications ◽  
Pumping Effect ◽  
Flow Through ◽  
The Mean ◽  
The Difference

In electrolysers with recirculation, where a gas is evolved, the pumping of electrolyte from a lower to a higher level can be effected by natural convection due to the difference between the densities of the inlet electrolyte and the gaseous emulsion at the outlet. An accurate balance equation for calculation of the rate of flow of the pumped liquid is derived. An equation for the calculation of the mean volume fraction of bubbles in the space between the electrodes is proposed and verified experimentally on a pilot electrolyser. Two examples of industrial applications are presented.

Hydrodynamic characteristics of vertical and quadrant face pile supported breakwater under oblique waves

2021 ◽  
pp. 147509022110313
Author(s):  
T J Jemi Jeya ◽  
V Sriram ◽  
V Sundar
Keyword(s):  
Experimental Study ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Scattering Parameter ◽  
Oblique Waves ◽  
Test Conditions ◽  
Relative Water ◽  
Identical Test ◽  
Run Up ◽  
Water Depths

This paper presents the results from a comprehensive experimental study on the Quadrant Face Pile Supported Breakwater (QPSB) in two different water depths exposed to three different oblique wave attacks. The results are compared with that for a Vertical face Pile Supported Breakwater (VPSB) for identical test conditions. The paper compares the reflection coefficient, transmission coefficient, energy loss coefficient, non-dimensional pressure, and non-dimensional run-up as a function of the relative water depth and scattering parameter. The results obtained for QPSB are validated with existing results. The salient observations show that QPSB experiences better hydrodynamic performance characteristics than the VPSB under oblique waves.

Remaining useful life estimation based on the joint use of an observer and a hidden Markov model

2021 ◽  
pp. 1748006X2110443
Author(s):  
Toufik Aggab ◽  
Pascal Vrignat ◽  
Manuel Avila ◽  
Frédéric Kratz
Keyword(s):  
Markov Models ◽  
Hidden Markov ◽  
Practical Interest ◽  
Markov Property ◽  
Rolling Bearing ◽  
Industrial Applications ◽  
Remaining Useful Life ◽  
Discrete Observations ◽  
Useful Life ◽  
The Difference

We propose an approach for failure prognosis based on the estimation of the Remaining Useful Life (RUL) of a system in a situation in which monitoring signals providing information about its degradation evolution are not measured and no operating model of the system is available. These conditions are of practical interest for industrial applications such as mechanical (e.g. rolling bearing) or electrical (e.g. wind turbine) devices or equipment-critical components (e.g. batteries) in which the addition of sensors to the system is not feasible (e.g. space limitations for sensors, cost, etc.). The approach is based on an estimation of the system degradation using residual generation (where the difference between the system and the observer outputs is processed) and Hidden Markov Models with discrete observations. The prediction of the system RUL is given by the Markov property concerning the mean time before absorption. The approach comprises two phases: a training phase to model the degradation behavior and an “on-line” use phase to estimate the remaining life of the system. Two case studies were conducted for RUL prediction to verify the effectiveness of the proposed approach.

Numerical Simulations of Particle-Laden Flow Based on Given Friction Reynolds Number and Mean Reynolds Number Respectively

2014 ◽  
Author(s):  
Zhenzhong Li ◽  
Jinjia Wei ◽  
Bo Yu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Wide Spectrum ◽  
Natural World ◽  
Industrial Applications ◽  
Particle Parameters ◽  
The Mean ◽  
The Difference ◽  
Particle Laden Flow

Multiphase flow with particles covers a wide spectrum of flow conditions in natural world and industrial applications. The experiments and the direct numerical simulation have become the most popular means to study the dilute particle-laden flow in the last two decades. In the experimental study, the mean Reynolds number is often adjusted to the value of single-phase flow for each set of particle conditions. However, the friction Reynolds number usually keeps invariable in the direct numerical simulation of the particle-laden flows for convenience. In this study the effect of the difference between given mean Reynolds number and friction Reynolds number was investigated. Two simulations were performed for each set of particle parameters, and the mean Reynolds number and friction Reynolds number were kept invariant respectively. From the results it can be found that the turbulence intensity and the dimensionless velocities are larger when keeping the friction Reynolds constant. And the results calculated from the cases of keeping the mean Reynolds number invariable agree with the experiment results better. In addition, the particle distribution along the wall-normal coordinate was found to be unchanged between two simulation conditions. As a suggestion, keeping the same mean Reynolds number in the direct numerical simulation of particle-laden flow is more appropriate.

scholarly journals Beta alanine supplementation effects on metabolic contribution and swimming performance

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Matheus Silva Norberto ◽  
Ricardo Augusto Barbieri ◽  
Danilo Rodrigues Bertucci ◽  
Ronaldo Bucken Gobbi ◽  
Eduardo Zapaterra Campos ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Energy Demand ◽  
Swimming Performance ◽  
Controlled Study ◽  
Double Blind ◽  
Repeated Measures Anova ◽  
Beta Alanine ◽  
Before And After ◽  
The Difference ◽  
And Performance

Abstract Background Investigations of β-alanine supplementation shows effects on metabolic (aerobic and anaerobic) participation and performance on swimming by a possible blood acidosis buffering. Considering this background, the objective of the present study was to analyze the effects of β-alanine supplementation on metabolic contribution and performance during 400-m swim. Methods Thirteen competitive swimmers underwent a 6-week, double-blind placebo-controlled study, ingesting 4.8 g.day− 1 of β-alanine or placebo. Before and after the supplementation period, the total anaerobic contribution (TAn) and 30-s all-out tethered swimming effort (30TS) were assessed. Anaerobic alactic (AnAl) and lactic energy (AnLa) was assumed as the fast component of excess post-exercise oxygen consumption and net blood lactate accumulation during exercise (∆[La−]), respectively. Aerobic contribution (Aer) was determined by the difference between total energy demand and TAn. In addition to conventional statistical analysis (Repeated measures ANOVA; p > 0.05), a Bayesian repeated measures ANOVA was used to evidence the effect probability (BFincl). Results No differences and effects were found between groups, indicating no supplementation effects. Repeated measures ANOVA, with confirmation of effect, was indicate reduce in ∆Lactate (p: 0.001; BFincl: 25.02); absolute AnLa (p: 0.002; BFincl: 12.61), fatigue index (p > 0.001; BFincl: 63.25) and total anaerobic participation (p: 0.008; BFincl: 4.89). Conclusions Thus, the results demonstrated that all changes presented were evidenced as a result of exposure to the training period and β-alanine supplementation doesn’t affect metabolic contribution and performance during 400-m freestyle.

scholarly journals Numerical Investigation on the Water Entry of Several Different Bow-Flared Sections

2020 ◽  
Vol 10 (22) ◽  
pp. 7952
Author(s):  
Qiang Wang ◽  
Boran Zhang ◽  
Pengyao Yu ◽  
Guangzhao Li ◽  
Zhijiang Yuan
Keyword(s):  
Stokes Equations ◽  
Water Entry ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Surface Evolution ◽  
Mesh Method ◽  
The Difference ◽  
Dynamics Method

The bow-flared section may be simplified in the prediction of slamming loads and whipping responses of ships. However, the difference of hydrodynamic characteristics between the water entry of the simplified sections and that of the original section has not been well documented. In this study, the water entry of several different bow-flared sections was numerically investigated using the computational fluid dynamics method based on Reynolds-averaged Navier–Stokes equations. The motion of the grid around the section was realized using the overset mesh method. Reasonable grid size and time step were determined through convergence studies. The application of the numerical method in the water entry of bow-flared sections was validated by comparing the present predictions with previous numerical and experimental results. Through a comparative study on the water entry of one original section and three simplified sections, the influences of simplification of the bow-flared section on hydrodynamic characteristics, free surface evolution, pressure field, and impact force were investigated and are discussed here.

Tunnelling in and The Microstructure of Granular Superconductors

1995 ◽  
Vol 411 ◽  
Author(s):  
D. S. McLachlan ◽  
R. Rosenbaum
Keyword(s):  
Critical Field ◽  
Volume Fraction ◽  
Upper Critical Field ◽  
Weak Links ◽  
Experimental Measurements ◽  
Quasi Particle ◽  
Random Composites ◽  
Granular Superconductors ◽  
The Difference ◽  
Particle Nature

ABSTRACTThe microstructure of granular superconductors are discussed and the difference between granular and random composites is noted. The model where a granular (and a random) superconductor, close to the percolation threshold, is considered to be made up of large granular clusters, linked by tunnelling junctions or weak links, is introduced. This model is illustrated using recent experimental measurements on nanostructured granular Aℓ–Ge. The measurements clearly show that the coupling junctions between clusters can,depending on the volume fraction of superconductor, be of either a Josephson or quasi–particle nature, or a combination of both. The differences between a granular and adirty superconductor and the upper critical field of granular superconductors is then discussed and it is shown that the diameter of the grains can be estimated from the upper critical field. Random Aℓ–Ge, which has a rather different microstructure, is also discussed.

Breaking the Myth That Relay Swimming Is Faster Than Individual Swimming

2016 ◽  
Vol 11 (3) ◽  
pp. 410-413 ◽  
Author(s):  
Sabrina Skorski ◽  
Naroa Etxebarria ◽  
Kevin G. Thompson
Keyword(s):  
Olympic Games ◽  
Swimming Performance ◽  
Individual Performance ◽  
Link Type ◽  
The Difference ◽  
Performance Times ◽  
Race Performance ◽  
Split Time ◽  
Relay Race

Purpose:To investigate if swimming performance is better in a relay race than in the corresponding individual race.Methods:The authors analyzed 166 elite male swimmers from 15 nations in the same competition (downloaded from www.swimrankings.net). Of 778 observed races, 144 were Olympic Games performances (2000, 2004, 2012), with the remaining 634 performed in national or international competitions. The races were 100-m (n = 436) and 200-m (n = 342) freestyle events. Relay performance times for the 2nd–4th swimmers were adjusted (+ 0.73 s) to allow for the “flying start.”Results:Without any adjustment, mean individual relay performances were significantly faster for the first 50 m and overall time in the 100-m events. Furthermore, the first 100 m of the 200-m relay was significantly faster (P > .001). During relays, swimmers competing in 1st position did not show any difference compared with their corresponding individual performance (P > .16). However, swimmers competing in 2nd–4th relay-team positions demonstrated significantly faster times in the 100-m (P < .001) and first half of the 200-m relays than in their individual events (P < .001, ES: 0.28–1.77). However, when finishing times for 2nd–4th relay team positions were adjusted for the flying start no differences were detected between relay and individual race performance for any event or split time (P > .17).Conclusion:Highly trained swimmers do not swim (or turn) faster in relay events than in their individual races. Relay exchange times account for the difference observed in individual vs relay performance.

Characteristics of OWC Type WEC Dampers Installed on a Very Large Floating Structure

2020 ◽  
Author(s):  
Tomoki Ikoma ◽  
Shoichiro Furuya ◽  
Yasuhiro Aida ◽  
Koichi Masuda ◽  
Hiroaki Eto
Keyword(s):  
Wave Energy ◽  
Sea Water ◽  
Prediction Method ◽  
Hydrodynamic Performance ◽  
Floating Body ◽  
Hydrodynamic Characteristics ◽  
Linear Potential ◽  
Floating Structure ◽  
Combined System ◽  
Floating System

Abstract Oscillating water column (OWC) type wave energy converters (WECs) have been researched and developed. OWC WECs are relatively friendly to maintain them in operation because all of mechanical units are set above a sea water surface. In addition, a feature of an OWC device is similar to an air dumper system. Thus, it should be possible not only to harvest wave energy but also to reduce motion of a floating system at the same time. As well as WEC system should be used with other ocean renewable energies as a combined system. This paper describes hydrodynamic characteristics of OWC devices and wave fields around them of multi-OWC devices equipped large floating structures. For this research, the linear potential theory based in-house programme code was applied to calculate hydrodynamic performance of OWC regions and elastic motion behaviours of the structures. Besides, calculation results were compared with some experimental results of characteristics of OWC devices on reference papers published. Then we proved validity of the calculation method. We have quantitatively summarized how much the reduction effect can be seen according to the aircushion placement and the number of aircushions on the floating body. the paper investigated arrangement of OWC devices on the floating structure with several variations. Using the prediction method, effects of arrangement of OWC devices on the performances are investigated.

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