Biorobotic insights into neuromechanical coordination of undulatory swimming

2021 ◽  
Vol 6 (57) ◽  
pp. eabk0620
Author(s):  
Eric D. Tytell ◽  
John H. Long
Keyword(s):  
Hydrodynamic Pressure ◽  
Undulatory Swimming

Skin sensors on an eel-like robot couple external hydrodynamic pressure with internal neural patterns for robust swimming.

Large-amplitude undulatory fish swimming: fluid mechanics coupled to internal mechanics

1999 ◽  
Vol 202 (23) ◽  
pp. 3431-3438 ◽  
Author(s):  
T.J. Pedley ◽  
S.J. Hill
Keyword(s):  
Vortex Ring ◽  
Large Amplitude ◽  
Muscle Activation ◽  
Bending Moment ◽  
Hydrodynamic Pressure ◽  
Moment Equation ◽  
Panel Method ◽  
The Body ◽  
Undulatory Swimming ◽  
Body Theory

The load against which the swimming muscles contract, during the undulatory swimming of a fish, is composed principally of hydrodynamic pressure forces and body inertia. In the past this has been analysed, through an equation for bending moments, for small-amplitude swimming, using Lighthill's elongated-body theory and a ‘vortex-ring panel method’, respectively, to compute the hydrodynamic forces. Those models are outlined in this review, and a summary is given of recent work on large-amplitude swimming that has (a) extended the bending moment equation to large amplitude, which involves the introduction of a new (though probably usually small) term, and (b) developed a large-amplitude vortex-ring panel method. The latter requires computation of the wake, which rolls up into concentrated vortex rings and filaments, and has a significant effect on the pressure on the body. Application is principally made to the saithe (Pollachius virens). The calculations confirm that the wave of muscle activation travels down the fish much more rapidly than the wave of bending.

scholarly journals Emergence of robust self-organized undulatory swimming based on local hydrodynamic force sensing

2021 ◽  
Vol 6 (57) ◽  
pp. eabf6354
Author(s):  
Robin Thandiackal ◽  
Kamilo Melo ◽  
Laura Paez ◽  
Johann Herault ◽  
Takeshi Kano ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Pattern Generators ◽  
Hydrodynamic Pressure ◽  
Modular Robots ◽  
Local Pressure ◽  
Ideal Behavior ◽  
Self Organized ◽  
Essential Components ◽  
Pattern Generators ◽  
Undulatory Swimming

Undulatory swimming represents an ideal behavior to investigate locomotion control and the role of the underlying central and peripheral components in the spinal cord. Many vertebrate swimmers have central pattern generators and local pressure-sensitive receptors that provide information about the surrounding fluid. However, it remains difficult to study experimentally how these sensors influence motor commands in these animals. Here, using a specifically designed robot that captures the essential components of the animal neuromechanical system and using simulations, we tested the hypothesis that sensed hydrodynamic pressure forces can entrain body actuation through local feedback loops. We found evidence that this peripheral mechanism leads to self-organized undulatory swimming by providing intersegmental coordination and body oscillations. Swimming can be redundantly induced by central mechanisms, and we show that, therefore, a combination of both central and peripheral mechanisms offers a higher robustness against neural disruptions than any of them alone, which potentially explains how some vertebrates retain locomotor capabilities after spinal cord lesions. These results broaden our understanding of animal locomotion and expand our knowledge for the design of robust and modular robots that physically interact with the environment.

scholarly journals Role of body stiffness in undulatory swimming: Insights from robotic and computational models

2016 ◽  
Vol 1 (7) ◽  
Author(s):  
Eric D. Tytell ◽  
Megan C. Leftwich ◽  
Chia-Yu Hsu ◽  
Boyce E. Griffith ◽  
Avis H. Cohen ◽  
...  
Keyword(s):  
Computational Models ◽  
Undulatory Swimming

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

scholarly journals Fast laser surface texturing of spherical samples to improve the frictional performance of elasto-hydrodynamic lubricated contacts

Friction ◽  
2021 ◽  
Author(s):  
G. Boidi ◽  
P. G. Grützmacher ◽  
A. Kadiric ◽  
F. J. Profito ◽  
I. F. Machado ◽  
...  
Keyword(s):  
Surface Texturing ◽  
Hydrodynamic Pressure ◽  
Friction Reduction ◽  
Laser Surface Texturing ◽  
Textured Surfaces ◽  
Engineering Applications ◽  
Lubricated Contacts ◽  
Fluid Uptake ◽  
Direct Laser ◽  
Frictional Performance

AbstractTextured surfaces offer the potential to promote friction and wear reduction by increasing the hydrodynamic pressure, fluid uptake, or acting as oil or debris reservoirs. However, texturing techniques often require additional manufacturing steps and costs, thus frequently being not economically feasible for real engineering applications. This experimental study aims at applying a fast laser texturing technique on curved surfaces for obtaining superior tribological performances. A femtosecond pulsed laser (Ti:Sapphire) and direct laser interference patterning (with a solid-state Nd:YAG laser) were used for manufacturing dimple and groove patterns on curved steel surfaces (ball samples). Tribological tests were carried out under elasto-hydrodynamic lubricated contact conditions varying slide-roll ratio using a ball-on-disk configuration. Furthermore, a specific interferometry technique for rough surfaces was used to measure the film thickness of smooth and textured surfaces. Smooth steel samples were used to obtain data for the reference surface. The results showed that dimples promoted friction reduction (up to 20%) compared to the reference smooth specimens, whereas grooves generally caused less beneficial or detrimental effects. In addition, dimples promoted the formation of full film lubrication conditions at lower speeds. This study demonstrates how fast texturing techniques could potentially be used for improving the tribological performance of bearings as well as other mechanical components utilised in several engineering applications.

Research on hydrodynamic pressure field causing by ship moving in mixed flow

2017 ◽  
Vol 136 ◽  
pp. 314-321
Author(s):  
Hui Deng ◽  
Zhi-hong Zhang ◽  
Ju-bin Liu ◽  
Chong Wang
Keyword(s):  
Pressure Field ◽  
Hydrodynamic Pressure ◽  
Mixed Flow

PSEUDOSTATIC DESIGN FACTORS FOR STABILITY OF WATERFRONT-RETAINING WALL DURING EARTHQUAKE

2010 ◽  
Vol 04 (04) ◽  
pp. 387-400 ◽  
Author(s):  
DEEPANKAR CHOUDHURY ◽  
SYED MOHD AHMAD
Keyword(s):  
Retaining Wall ◽  
Pressure Ratio ◽  
Free Water ◽  
Hydrodynamic Pressure ◽  
Wall Friction ◽  
Sliding Stability ◽  
The Stability ◽  
Seismic Forces ◽  
Design Factors ◽  
Similar Kind

The paper presents a methodology for seismic design of rigid watferfront-retaining wall and proposes simple design factors for the sliding stability under seismic condition. Conventional pseudostatic approach has been used for the calculation of the seismic forces, while for the calculation of the hydrodynamic pressure, Westergaard's approach has been used. In addition, the hydrodynamic force has been considered from both the upstream and downstream sides of the waterfront-retaining wall under free water condition of the backfill. Simplified expression for the calculation of the equivalent weight of the wall which would be needed to maintain sliding stability is presented. It has been observed that the presence of water both on the upstream and downstream sides of the wall has serious destabilizing effect on the stability of the wall. It is noticed that as the height of the water inside the backfill increased from 0.00 to a height equal to the height of the wall itself, i.e., the backfill is fully submerged, the weight of the wall needed for the later case is around 3 times more than what would be needed for the former case. Similar observations were also made by varying other parameters like the horizontal and vertical seismic acceleration coefficients, height of the water on the upstream side of the wall, and soil and wall friction angles. The pore pressure ratio and the inclination of the ground, however, did not have significant effect on the results. Due to nonavailability of the results of similar kind in literature, an exact comparison for the present results could not be made. Only partial comparison of the present results is made with an already existing methodology for the dry backfill case only, in which no presence of water has been considered on the other side of the wall. This comparison shows a good agreement with the present results. The proposed pseudostatic design factors for the case of wet backfill with the presence of water on both sides of the wall are claimed to be unique.

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