scholarly journals The Analysis of Biomimetic Caudal Fin Propulsion Mechanism with CFD

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Guijie Liu ◽  
Shuikuan Liu ◽  
Yingchun Xie ◽  
Dingxin Leng ◽  
Guanghao Li
Keyword(s):  
High Efficiency ◽  
High Mobility ◽  
Caudal Fin ◽  
Propulsion Performance ◽  
Propulsion Force ◽  
St Number ◽  
Underwater Movement ◽  
The Mathematical Model ◽  
Bionic Propulsion ◽  
Bionic Underwater Robot

In nature, fish not only have extraordinary ability of underwater movement but also have high mobility and flexibility. The low energy consumption and high efficiency of fish propulsive method provide a new idea for the research of bionic underwater robot and bionic propulsive technology. In this paper, the swordfish was taken as the research object, and the mechanism of the caudal fin propulsion was preliminarily explored by analyzing the flow field structure generated by the swing of caudal fin. Subsequently, the influence of the phase difference of the heaving and pitching movement, the swing amplitude of caudal fin, and Strouhal number (St number) on the propulsion performance of fish was discussed. The results demonstrated that the fish can obtain a greater propulsion force by optimizing the motion parameters of the caudal fin in a certain range. Lastly, through the mathematical model analysis of the tail of the swordfish, the producing propulsive force principle of the caudal fin and the caudal peduncle was obtained. Hence, the proposed method provided a theoretical basis for the design of a high-efficiency bionic propulsion system.

Experimental Research on a Novel Design of Variable Area Caudal Fin

2013 ◽  
Vol 461 ◽  
pp. 206-212
Author(s):  
Bo Liu ◽  
Lei Wang ◽  
Bu Yao Chen ◽  
Feng Hua Qin ◽  
Shi Wu Zhang
Keyword(s):  
High Efficiency ◽  
Thrust Force ◽  
Lateral Force ◽  
The Novel ◽  
Kinematic Parameters ◽  
Fish Swimming ◽  
Caudal Fin ◽  
Propulsion Performance ◽  
Novel Design ◽  
Propulsive Mechanism

Caudal fin has fascinated researchers for decades for their great role in fish swimming, and researchers have developed lots of designs of caudal fin to achieve high efficiency and speed propulsion. This paper presents a novel design of variable area caudal fin. A “window” which can rotate freely is designed in the middle of the fin and it can be opened by the fluid force and closed by a simple mechanism. By closing or opening the “window”, the caudal fin can vary its area dynamically in the out-stroke and in-stroke in its motion. Four modes to control the “window” in the pitching motion is then presented, their hydrodynamic forces including thrust force, lateral force and lift force are studied. It is found out that the variable area fin model can indeed improve the propulsion performance compared with the traditional fin, and the mode of closing the “window” in the out-stroke and opening the “window” in the in-stroke can generate the largest thrust force for our model than the other modes. Moreover, experiments about various kinematic parameters with different modes are conducted, it is found out different modes behave quite different with same pitching frequency and amplitude, and its propulsive performance is highly depend on the kinematic parameters. The variable area caudal fin model casts an inspiration for the novel design of underwater propulsive mechanism and the results will be useful for the propulsion study of underwater bio-mimetic vehicles.

Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

scholarly journals High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Maria Vasilopoulou ◽  
Abd. Rashid bin Mohd Yusoff ◽  
Matyas Daboczi ◽  
Julio Conforto ◽  
Anderson Emanuel Ximim Gavim ◽  
...  
Keyword(s):  
High Efficiency ◽  
Light Emitting Diodes ◽  
High Mobility ◽  
Organic Light Emitting Diodes ◽  
Triplet Energy ◽  
Material Interface ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light ◽  
Hole Transporting

AbstractBlue organic light-emitting diodes require high triplet interlayer materials, which induce large energetic barriers at the interfaces resulting in high device voltages and reduced efficiencies. Here, we alleviate this issue by designing a low triplet energy hole transporting interlayer with high mobility, combined with an interface exciplex that confines excitons at the emissive layer/electron transporting material interface. As a result, blue thermally activated delay fluorescent organic light-emitting diodes with a below-bandgap turn-on voltage of 2.5 V and an external quantum efficiency (EQE) of 41.2% were successfully fabricated. These devices also showed suppressed efficiency roll-off maintaining an EQE of 34.8% at 1000 cd m−2. Our approach paves the way for further progress through exploring alternative device engineering approaches instead of only focusing on the demanding synthesis of organic compounds with complex structures.

Regenerative Gas Turbines With Divided Expansion

2004 ◽  
Author(s):  
Brian Elmegaard ◽  
Bjo̸rn Qvale
Keyword(s):  
Mathematical Model ◽  
Gas Turbines ◽  
High Efficiency ◽  
Limited Range ◽  
Simulation Program ◽  
Operating Parameters ◽  
Gas Generator ◽  
Extensive Simulation ◽  
Power Turbine ◽  
The Mathematical Model

Recuperated gas turbines are currently drawing an increased attention due to the recent commercialization of micro gas turbines with recuperation. This system may reach a high efficiency even for the small units of less than 100kW. In order to improve the economics of the plants, ways to improve their efficiency are always of interest. Recently, two independent studies have proposed recuperated gas turbines to be configured with the turbine expansion divided, in order to obtain higher efficiency. The idea is to operate the system with a gas generator and a power turbine, and use the gas from the gas generator part for recuperation ahead of the expansion in the power turbine. The present study is more complete than the predecessors in that the ranges of the parameters have been extended and the mathematical model is more realistic using an extensive simulation program. It is confirmed that the proposed divided expansion can be advantageous under certain circumstances. But, in order for todays micro gas turbines to be competitive, the thermodynamic efficiencies will have to be rather high. This requires that all component efficiencies including the recuperator effectiveness will have to be high. The advantages of the divided expansion manifest themselves over a rather limited range of the operating parameters, that lies outside the range required to make modern micro turbines economically competitive.

Simulation Study on Travel-Driven System of HST Loader with Matlab/Simulink

2013 ◽  
Vol 313-314 ◽  
pp. 1100-1104
Author(s):  
En Zhe Song ◽  
Chang Xi Ji ◽  
Mei Liang Yin ◽  
Jun Sun ◽  
Cheng Shun Yin
Keyword(s):  
Pid Control ◽  
Theoretical Basis ◽  
Control Algorithm ◽  
High Efficiency ◽  
Practical Significance ◽  
Matlab Simulink ◽  
Loop Control ◽  
Driven System ◽  
Close Loop Control ◽  
The Mathematical Model

This paper establishes the mathematical model of the volume speed-modulating system and simulates dynamically with Matlab/Simulink. Provide a theoretical basis for algorithm of close loop control [ of the three variables which are diesel engines, variable pump and variable motor. Use PID control algorithm, through simulation and analysis, find out the parameter optimization adjustment rule [2,, seek matching operation between three variables. Provide a theoretical basis for the study on dynamic system of full-hydraulic loaders and have very important practical significance in realizing high efficiency energy saving and reducing energy consumption.

scholarly journals High mobility organic semiconductor for constructing high efficiency carbon nitride heterojunction photocatalysts

2020 ◽  
Vol 8 (48) ◽  
pp. 17157-17161
Author(s):  
Yan Yi ◽  
Siyu Wang ◽  
Hantang Zhang ◽  
Jie Liu ◽  
Xiuqiang Lu ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Organic Semiconductor ◽  
Carbon Nitride ◽  
High Efficiency ◽  
High Mobility ◽  
Photocatalytic Performances

High-mobility organic semiconductor CuPc is used to construct CN/CuPc heterojunction photocatalysts, showing enhanced photocatalytic performances. This work proves the prospect of high-mobility organic semiconductors in photocatalysis.

Design, analysis and experiment of an eight-wheel robotic vehicle with four-swing arms

2019 ◽  
Vol 46 (5) ◽  
pp. 682-691 ◽  
Author(s):  
Miaolei He ◽  
Changji Ren ◽  
Jilin He ◽  
Kang Wu ◽  
Yuming Zhao ◽  
...  
Keyword(s):  
High Efficiency ◽  
Kinematic Model ◽  
High Mobility ◽  
Control Algorithms ◽  
Content Type ◽  
Uneven Terrain ◽  
Mechanism Control ◽  
Robotic Vehicles ◽  
Robotic Vehicle ◽  
Wheel Radius

Purpose Excellent obstacle surmounting performance is essential for the robotic vehicles in uneven terrain. However, existing robotic vehicles depend on complex mechanisms or control algorithms to surmount an obstacle. Therefore, this paper aims to propose a new simple configuration of an all-terrain robotic vehicle with eight wheels including four-swing arms. Design/methodology/approach This vehicle is driven by distributed hydraulic motors which provide high mobility. It possesses the ability to change the posture by means of cooperation of the four-swing arms. This ensures that the vehicle can adapt to complex terrain. In this paper, the bionic mechanism, control design and steering method of the vehicle are introduced. Then, the kinematic model of the center of gravity is studied. Afterward, the obstacle surmounting performance based on a static model is analyzed. Finally, the simulation based on ADAMS and the prototype experiment is carried out. Findings The experiment results demonstrate that the robotic vehicle can surmount an obstacle 2.29 times the height of the wheel radius, which verifies the feasibility of this new configuration. Therefore, this vehicle has excellent uneven terrain adaptability. Originality/value This paper proposes a new configuration of an all-terrain robotic vehicle with four-swing arms. With simple mechanism and control algorithms, the vehicle has a high efficiency of surmounting an obstacle. It can surmount a vertical obstacle 2.29 times the height of the wheel radius.

Influence of the Obliquity of Fin Ray on Propulsion Performance for Biorobotic Underwater Undulating Propulsor

2011 ◽  
Vol 52-54 ◽  
pp. 267-272 ◽  
Author(s):  
Yong Hua Zhang ◽  
Jian Hui He ◽  
Guo Qing Zhang
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Environment Friendly ◽  
Contour Maps ◽  
Propulsion Performance ◽  
Fin Ray ◽  
Propulsion Force ◽  
Computational Fluid Dynamics Cfd ◽  
Motion Performance ◽  
Cfd Method

This paper aims to understand influence of the obliquity of fin ray on its motion performance. An environment-friendly propulsion system mimicking undulating fins of stingray had been built. Investigations were presented by using three-dimensional unsteady Computational Fluid Dynamics (CFD) method. An unstructured, grid-based, unsteady Navier-Stokes solver with automatic adaptive remeshing was used to compute the unsteady flow around the fin through twenty complete cycles. The pressure distribution on fin surface was computed and integrated to provide fin forces which were decomposed into lift and thrust. Vortex contour maps of the fin with different obliquity of fin ray were displayed and compared. Finally, we draw a conclusion that the generated propulsion force of the biomimetic propulsor is gradually increase with the obliquity of the fin ray from 0 degree till a certain angle and then gradually decrease with the obliquity of the fin ray from the certain angle till 90 degree. The results provide valuable information for the optimization of robotic underwater undulating propulsor design.

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