scholarly journals Numerical Simulation and Analysis of Fish-Like Robots Swarm

2019 ◽  
Vol 9 (8) ◽  
pp. 1652 ◽  
Author(s):  
Shuman Li ◽  
Chao Li ◽  
Liyang Xu ◽  
Wenjing Yang ◽  
Xucan Chen
Keyword(s):  
Numerical Simulation ◽  
Power Loss ◽  
Underwater Robot ◽  
Close Spacing ◽  
Swimming Efficiency ◽  
Important Branch

Artificial fish-like robot is an important branch of underwater robot research. At present, most of fish-like robot research focuses on single robot mechanism behavior, some research pays attention to the influence of the hydro-environment on robot crowds but does not reach a unified conclusion on the efficiency of fish-like robots swarm. In this work, the fish-like robots swarm is studied by numerical simulation. Four different formations, including the tandem, the phalanx, the diamond, and the rectangle are conducted by changing the spacing between fishes. The results show that at close spacing, the fish in the back can obtain a large wake from the front fish, but suffers large lateral power loss from the lateral fish. On the contrary, when the spacing is large, both the wake and pressure caused by the front and side fishes become small. In terms of the average swimming efficiency of fish swarms, we find that when the fish spacing is less than 1.25 L (L is the length of the fish body), the tandem swarm is the best choice. When the spacing is 1.25 L , the tandem, diamond and rectangle swarms have similar efficiency. When the spacing is larger than 1.25 L , the rectangle swarm is more efficient than other formations. The findings will provide significant guidance for the control of fish-like robots swarm.

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.

The Effect of Misalignment on Power Loss in Ball Bearings

2008 ◽  
Author(s):  
Ioan Damian ◽  
Ion Oancea ◽  
Spiridon Cretu
Keyword(s):  
Numerical Simulation ◽  
Experimental Study ◽  
Dynamic Model ◽  
Power Loss ◽  
Static Model ◽  
Static Equilibrium ◽  
Experimental Measurements ◽  
Ball Bearings ◽  
Centrifugal Forces ◽  
Fluid Drag

A vectorial method has been developed to solve the quasi-static equilibrium in angular contact ball bearings. In the quai-static model the effects induced by the centrifugal forces, gyroscopic moments and misalignments between bearing’s rings were considered. The lubricant parameters, traction forces and fluid drag action on balls and raceways were further included in a quasi-dynamic model. An experimental study has been further carried out to validate the quasi-dynamic model when a certain degree of misalignment exists between the inner and outer rings of the bearing. Both numerical simulation and experimental measurements emphasized the major contribution of the rings misalignment upon the bearing power loss.

scholarly journals Numerical Simulation of a Slipper Model with Multi-Lands and Grooves for Hydraulic Piston Pumps and Motors in Mixed Lubrication

Lubricants ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 55
Author(s):  
Toshiharu Kazama
Keyword(s):  
Numerical Simulation ◽  
Contact Pressure ◽  
Power Loss ◽  
Numerical Solutions ◽  
Friction Torque ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Axial Piston Pumps ◽  
Wide Range ◽  
Axial Piston

A theoretical model of a slipper with multi-lands and multi-grooves for swashplate type axial piston pumps and motors was established, including surface interactions. Further, a numerical simulation was conducted under an unsteady state and mixed lubrication conditions. Four model configurations were considered: A slipper with a single main land; a slipper with inner and main lands and a groove; a slipper with outer and main lands and a groove; and a slipper with inner, main, and outer lands with two grooves. Numerical solutions were obtained across a wide range of operating conditions in terms of center clearance, pad attitude, contact pressure, flow rate, friction torque, power loss, and stiffness. The motion and characteristics were differentiated into two groups: Slippers with a single-land and an annex inner-land; and slippers with an annex outer-land and a triple-land. The single-land and annex inner-land slippers exhibited smaller pad swing, whereas the triple-land and annex outer-land slippers reduced contact pressure and power loss.

scholarly journals Optimal Design of Computational Fluid Dynamics: Numerical Calculation and Simulation Analysis of Windage Power Losses in the Aviation

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1999
Author(s):  
Yuzhong Zhang ◽  
Linlin Li ◽  
Ziqiang Zhao
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Turbulence Model ◽  
Power Loss ◽  
Simulation Analysis ◽  
Gear Tooth ◽  
Tooth Surface ◽  
Phase Flow ◽  
Gear Pair

Based on the theory of computational fluid dynamics (CFD), with the help of the Fluent software and the powerful parallel computing capability of the super cloud computer, the single-phase flow transient simulation calculation of the windage power loss of the engagement spiral bevel gear pair (SBGP) was performed. The two-equation SST k-ω turbulence model based on the assumption of eddy viscosity was adopted, which was improved from the standard k-ε model combined with the Wilcox k-ω model. The SST k-ω turbulence model inherited the respective advantages of the Wilcox k-ω model in the near-wall region and the k-ε model in the free shear layer and could more accurately describe the resistance and separation effect of the gear tooth surface on the airflow. The simulation analyzed the airflow characteristics around SBGP and the mechanism of the windshield to reduce the windage loss of the gear. It also studied the influence of the windshield clearance and opening size on the windage power loss. Then the orthogonal experimental analysis method was adopted to perform numerical simulation analysis. The windage torque was studied under different clearance values between the windshield and the gear tooth surface, as well as the large end and the small end. The variance analysis was performed on the numerical simulation data. The results showed that when the windshield clearance value was 1 mm and the engagement opening was 30°, the windage torque was the smallest, and the effect of reducing the windage power loss was the best. According to the changes in the pressure, velocity, and turbulent kinetic energy cloud diagram of the flow field in the reducer during multi-group simulation tests, the local optimal windshield configuration was obtained, which provided a method for further research on the multi-objective optimization of the windshield and the windage loss of the gear pair under the oil–gas two-phase flow and also provided a reference for the practical engineering application of the windshield.

scholarly journals Torque and Power Loss in a Cylindrical Fluid-Lubricated Bearing/Rotor System

1996 ◽  
Author(s):  
Paul Goldman ◽  
Alex Petchenev ◽  
Donald E. Bently ◽  
Agnes Muszynska
Keyword(s):  
Numerical Simulation ◽  
Power Loss ◽  
Rotor System ◽  
High Eccentricity ◽  
Fluid Forces ◽  
Fluid Resistance ◽  
Resistance Torque ◽  
High Fluid ◽  
Torque Values ◽  
Analytical Expressions

The paper contains the study of the lubricant fluid forces applied to the journal in a cylindrical, externally-pressurized bearing. The analytical expressions take into account the appearance of fluid cavitation at high eccentricity level. The obtained expressions for fluid forces and torque are used for numerical simulation of a simple, one-mode rotor system. The system exhibits typical fluid whirl/whip instability which results in high fluid resistance torque values. The latter is considered as one of the causes of turbomachinery efficiency deterioration due to fluid-induced instabilities. This paper is a continuation of the study undertaken by Bently et al. (1985), Muszynska (1986), and Petchenev et al. (1995).

Water uptake by substituted amylose tablets: experimentation and numerical simulation

2009 ◽  
Vol 00 (00) ◽  
pp. 090904073309027-8
Author(s):  
H.W. Wang ◽  
S. Kyriacos ◽  
L. Cartilier
Keyword(s):  
Numerical Simulation ◽  
Water Uptake
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