scholarly journals Mechanical models of sandfish locomotion reveal principles of high performance subsurface sand-swimming

2011 ◽  
Vol 8 (62) ◽  
pp. 1332-1345 ◽  
Author(s):  
Ryan D. Maladen ◽  
Yang Ding ◽  
Paul B. Umbanhowar ◽  
Adam Kamor ◽  
Daniel I. Goldman
Keyword(s):  
High Speed ◽  
High Performance ◽  
Granular Media ◽  
The Body ◽  
Physical Models ◽  
Particle Simulation ◽  
Sinusoidal Wave ◽  
Drag Forces ◽  
Single Period ◽  
Discrete Particle Simulation

We integrate biological experiment, empirical theory, numerical simulation and a physical model to reveal principles of undulatory locomotion in granular media. High-speed X-ray imaging of the sandfish lizard, Scincus scincus , in 3 mm glass particles shows that it swims within the medium without using its limbs by propagating a single-period travelling sinusoidal wave down its body, resulting in a wave efficiency, η , the ratio of its average forward speed to the wave speed, of approximately 0.5. A resistive force theory (RFT) that balances granular thrust and drag forces along the body predicts η close to the observed value. We test this prediction against two other more detailed modelling approaches: a numerical model of the sandfish coupled to a discrete particle simulation of the granular medium, and an undulatory robot that swims within granular media. Using these models and analytical solutions of the RFT, we vary the ratio of undulation amplitude to wavelength ( A / λ ) and demonstrate an optimal condition for sand-swimming, which for a given A results from the competition between η and λ . The RFT, in agreement with the simulated and physical models, predicts that for a single-period sinusoidal wave, maximal speed occurs for A / λ ≈ 0.2, the same kinematics used by the sandfish.

Larval locomotion of the lancelet

1997 ◽  
Vol 200 (11) ◽  
pp. 1661-1680 ◽  
Author(s):  
M Stokes
Keyword(s):  
Fluid Flow ◽  
High Speed ◽  
Developmental Stages ◽  
Large Degree ◽  
The Body ◽  
Sinusoidal Wave ◽  
Branchiostoma Floridae ◽  
Early Developmental Stages ◽  
Order Of Magnitude ◽  
Early Developmental

The ontogeny of locomotion in the Florida lancelet (Branchiostoma floridae) is described for the early developmental stages through to metamorphosis. Recently hatched larvae swam at speeds up to 1 mm s-1 using their epidermal cilia; this speed decreased to approximately 0.2 mm s-1 by 60 h after fertilization. Changes in cilia-powered fluid flow could be related to changes in the distribution and density of the epidermal cilia during development. Cilia-powered hovering was the dominant behaviour until metamorphosis. The amount of energy expended by ciliating larvae ranged from 10(-9) to 10(-11) W depending upon the age of the larvae and the model used for estimating the power output. The majority of the energy expended was in the ciliary sublayer next to the body. The first muscular movements were seen in larvae 16 h old. These simple flexions increased in complexity during the first 72 h until a complete undulatory (approximately sinusoidal) wave was propagated down the body in the adult manner. The frequency of undulatory beating increased to approximately 10 Hz during the first 48 h, and the larval head showed a large degree of yaw. Lancelet larvae were also capable of high-speed undulations 5­10 times faster than regular swimming motions. In contrast to ciliating larvae, the energy expended during undulation was at least an order of magnitude greater (10(-8) to 10(-6) W) and radiated beyond the ciliary sublayer.

Controlling subterranean forces enables a fast, steerable, burrowing soft robot

2021 ◽  
Vol 6 (55) ◽  
pp. eabe2922
Author(s):  
Nicholas D. Naclerio ◽  
Andras Karsai ◽  
Mason Murray-Cooper ◽  
Yasemin Ozkan-Aydin ◽  
Enes Aydin ◽  
...  
Keyword(s):  
Granular Media ◽  
The Body ◽  
Nonlinear Dependence ◽  
Soft Robot ◽  
Flow Angle ◽  
Drag Forces ◽  
Tip Extension ◽  
Order Of Magnitude ◽  
Lift And Drag ◽  
And Control

Robotic navigation on land, through air, and in water is well researched; numerous robots have successfully demonstrated motion in these environments. However, one frontier for robotic locomotion remains largely unexplored—below ground. Subterranean navigation is simply hard to do, in part because the interaction forces of underground motion are higher than in air or water by orders of magnitude and because we lack for these interactions a robust fundamental physics understanding. We present and test three hypotheses, derived from biological observation and the physics of granular intrusion, and use the results to inform the design of our burrowing robot. These results reveal that (i) tip extension reduces total drag by an amount equal to the skin drag of the body, (ii) granular aeration via tip-based airflow reduces drag with a nonlinear dependence on depth and flow angle, and (iii) variation of the angle of the tip-based flow has a nonmonotonic effect on lift in granular media. Informed by these results, we realize a steerable, root-like soft robot that controls subterranean lift and drag forces to burrow faster than previous approaches by over an order of magnitude and does so through real sand. We also demonstrate that the robot can modulate its pullout force by an order of magnitude and control its direction of motion in both the horizontal and vertical planes to navigate around subterranean obstacles. Our results advance the understanding and capabilities of robotic subterranean locomotion.

The Vertical Forces Introduced by Wind on the Active Pantograph from Bodywork of Locomotive LE 060 EA of 5100 kW

2015 ◽  
Vol 809-810 ◽  
pp. 1115-1120 ◽  
Author(s):  
Sorin Arsene
Keyword(s):  
Comparative Analysis ◽  
Power Supply ◽  
High Speed ◽  
High Performance ◽  
The Body ◽  
Vehicle Body ◽  
Aerodynamic Forces ◽  
Railway Vehicles ◽  
Railway Traction ◽  
Electric Railway

Gusts of wind with high speed can adversely affect the operation of the electric railway vehicles. These vehicles are able to move and to obtain a high performance, as long as the power supply is ensured. The variation of the vertical forces for maintaining contact between pantograph and catenary may cause interruption of the power supply of the electric railway traction vehicles. The placement of the capture equipment on the vehicle body determines appearance of aerodynamic forces acting on it. To see which are the vertical forces introduced by wind on active capture equipment, used at locomotives LE 060 EA of 5100 kW, we considered the EP3 type of pantograph as model. This was modelled at scale 1:1 taking into account the placement on the body of the locomotive. For the simulation of wind we considered three point values of its speed (10 m/s, 20 m/s, 30 m/s) and angle of eight values that are within the range of 0 deg – 180 deg. With the results of the simulation we have done a comparative analysis on the additional vertical forces introduced by wind for the cases analyzed.

scholarly journals Numerical Analysis of Aerodynamic Characteristics of a of High-Speed Car With Movable Bodywork Elements

2015 ◽  
Vol 62 (4) ◽  
pp. 451-476 ◽  
Author(s):  
Tomasz Janson ◽  
Janusz Piechna
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Transient Flow ◽  
Aerodynamic Drag ◽  
Position Angle ◽  
Aerodynamic Characteristics ◽  
The Body ◽  
Ansys Fluent ◽  
Drag Forces ◽  
And Performance

Abstract This paper presents the results of numerical analysis of aerodynamic characteristics of a sports car equipped with movable aerodynamic elements. The effects of size, shape, position, angle of inclination of the moving flaps on the aerodynamic downforce and aerodynamic drag forces acting on the vehicle were investigated. The calculations were performed with the help of the ANSYS-Fluent CFD software. The transient flow of incompressible fluid around the car body with moving flaps, with modeled turbulence (model Spalart-Allmaras or SAS), was simulated. The paper presents examples of effective flap configuration, and the example of configuration which does not generate aerodynamic downforce. One compares the change in the forces generated at different angles of flap opening, pressure distribution, and visualization of streamlines around the body. There are shown the physical reasons for the observed abnormal characteristics of some flap configurations. The results of calculations are presented in the form of pressure contours, pathlines, and force changes in the function of the angle of flap rotation. There is also presented estimated practical suitability of particular flap configurations for controlling the high-speed car stability and performance.

Computational and Experimental Approach to Understanding Legged Mobility in Micro Ground Vehicles

2014 ◽  
Author(s):  
Rudranarayan Mukherjee ◽  
Scott Moreland ◽  
Isaac Kim ◽  
Nikhil Lele ◽  
Stephen Goodwin ◽  
...  
Keyword(s):  
High Speed ◽  
High Performance ◽  
Granular Media ◽  
Necessary Condition ◽  
High Fidelity ◽  
Natural Environments ◽  
Ground Vehicles ◽  
Tactile Sensors ◽  
High Speed Imaging ◽  
Vehicle Mobility

The army has a vision for using autonomous micro ground vehicles (MGV) for soldier support in the last 100 meters of operations in urban and natural environments. These MGVs are expected to typically fit in a human palm and weigh in the order of 30–50 grams. Robust mobility is a necessary condition to ensure operations. Given the severe challenge of size, weight and power (SWAP) of the MGVs, significant uncertainties currently remain in quantifying micro ground vehicle mobility. In this paper we describe a research methodology and representative results for understanding legged MGV mobility in different types of terrain. Our methodology is based on a synergy of novel experimental setup and high-fidelity computational methods. We report the use of a novel “single-leg” test rig that uses tactile sensors to measure ground interaction loads. We also report the use of high speed imaging and use of particle image velocimetry to understand soil deformation during legged interactions with terrain. Finally, we report on the use of multibody dynamics and High Performance Computing (HPC) based granular media simulations. This conference paper emphases more on the overall approach based on synergistic use of high fidelity modeling and experimental methods supported by representative results rather than presenting a detailed analyses of the results.

scholarly journals SIZE LIMITS IN ESCAPE LOCOMOTION OF CARRIDEAN SHRIMP

1989 ◽  
Vol 143 (1) ◽  
pp. 245-265 ◽  
Author(s):  
THOMAS L. DANIEL ◽  
EDGAR MEYHÖFER
Keyword(s):  
High Speed ◽  
Relative Length ◽  
The Body ◽  
Drag Forces ◽  
Aquatic Locomotion ◽  
Angular Momenta ◽  
Theoretical Approaches ◽  
Tail Flip ◽  
Size Limits ◽  
Thrust Forces

Escape locomotion of the common dock shrimp, Pandalus danae Stimpson, is the result of a rapid flexion of the abdomen that lasts approximately 30 ms. The hydrodynamic forces that result from this motion lead to body accelerations in excess of 100ms−2 and body rotations of about 75°. We examined the mechanics and kinematics of this mode of locomotion with both experimental and theoretical approaches. Using a system of differential equations that rely on conservation of both linear and angular momenta, we develop predictions for body movements, thrust forces and muscle stresses associated with escape locomotion. The predicted movements of the body agree to within 10 % with data from high-speed ciné-photography for body translations and rotations. The thrust from rapid tail flexion is dominated by accelerational forces and by the force required to squeeze fluid out of the gap created by the cephalothorax and the abdomen at the end of tail flexion. This squeeze force overwhelms any propulsive drag forces that arise from the tail-flip. Using the theoretical analysis, we identify two additional features about unsteady, rotational aquatic locomotion. First, as either the relative length of the propulsive appendage increases or the absolute body size increases, rotational motions become disproportionately greater than translational motions, and escape performance decays. Second, if muscle stresses developed during escape cannot exceed the maximum isometric stress, there is a unique body length (6 cm) that maximizes the distance travelled during the escape event.

scholarly journals Pausing after clap reduces power required to fling wings apart at low Reynolds number

2020 ◽  
Author(s):  
Vishwa T. Kasoju ◽  
Arvind Santhanakrishnan
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
High Speed ◽  
Lift Coefficient ◽  
Pause Duration ◽  
Physical Models ◽  
Power Coefficient ◽  
Average Force ◽  
Drag Forces ◽  
Lift And Drag

AbstractThe smallest flying insects such as thrips (body length < 2 mm) are challenged with needing to move in air at chord-based Reynolds number (Rec) on the order of 10. Pronounced viscous dissipation at such low Rec requires considerable energetic expenditure for tiny insects to stay aloft. Free-flying thrips flap their densely bristled wings at large stroke amplitudes, bringing both wings in close proximity of each other at the end of upstroke (‘clap’) and moving their wings apart at the start of downstroke (‘fling’). From high-speed videos of free-flying thrips, we observed that their forewings remain clapped for approximately 10% of the wingbeat cycle before start of fling. We sought to examine if there are aerodynamic advantages associated with pausing wing motion after clap and before fling at Rec=10. A dynamically scaled robotic clap-and-fling platform was used to measure lift and drag forces generated by physical models of non-bristled (solid) and bristled wing pairs for pause times ranging between 0% to 41% of the cycle. In both solid and bristled wings, varying pause time showed no effect on average force coefficients generated within each half-stroke. This was supported by nearly identical time-variation of circulation of the leading and trailing edge vortices for different pause times. At smaller pause times, bristled wings showed larger reduction of cycle-averaged drag coefficient as compared to that of solid wings. For a given wing design (solid or bristled), the ratio of cycle-averaged lift coefficient to cycle-averaged drag coefficient was unchanged across different pause times. We observed 13.5% drop in cycle-averaged power coefficient and 3% drop in cycle-averaged lift coefficient when moving from 0% pause to 9% pause duration. Our results suggest that pausing at the end of clap can be beneficial for reducing the power required to fling, with a small reduction in lift.

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

PHAX-SCAN: Functional integration of a Scanning Electron Microscope and an energy-dispersive x-ray analyser

1989 ◽  
Vol 47 ◽  
pp. 56-57
Author(s):  
Marc H. Peeters ◽  
Max T. Otten
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
Functional Integration ◽  
Energy Dispersive ◽  
X Rays ◽  
X Ray ◽  
High Speed Analysis ◽  
Scanning Electron

Over the past decades, the combination of energy-dispersive analysis of X-rays and scanning electron microscopy has proved to be a powerful tool for fast and reliable elemental characterization of a large variety of specimens. The technique has evolved rapidly from a purely qualitative characterization method to a reliable quantitative way of analysis. In the last 5 years, an increasing need for automation is observed, whereby energy-dispersive analysers control the beam and stage movement of the scanning electron microscope in order to collect digital X-ray images and perform unattended point analysis over multiple locations.The Philips High-speed Analysis of X-rays system (PHAX-Scan) makes use of the high performance dual-processor structure of the EDAX PV9900 analyser and the databus structure of the Philips series 500 scanning electron microscope to provide a highly automated, user-friendly and extremely fast microanalysis system. The software that runs on the hardware described above was specifically designed to provide the ultimate attainable speed on the system.

The bright future of digital imaging in scanning electron microscopy

1993 ◽  
Vol 51 ◽  
pp. 768-769
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Digital Imaging ◽  
High Speed ◽  
High Performance ◽  
Mass Storage ◽  
Analog To Digital ◽  
Central Processing ◽  
Digital Imaging Technology ◽  
Scanning Electron

One of the major advancements applied to scanning electron microscopy (SEM) during the past 10 years has been the development and application of digital imaging technology. Advancements in technology, notably the availability of less expensive, high-density memory chips and the development of high speed analog-to-digital converters, mass storage and high performance central processing units have fostered this revolution. Today, most modern SEM instruments have digital electronics as a standard feature. These instruments, generally have 8 bit or 256 gray levels with, at least, 512 × 512 pixel density operating at TV rate. In addition, current slow-scan commercial frame-grabber cards, directly applicable to the SEM, can have upwards of 12-14 bit lateral resolution permitting image acquisition at 4096 × 4096 resolution or greater. The two major categories of SEM systems to which digital technology have been applied are:In the analog SEM system the scan generator is normally operated in an analog manner and the image is displayed in an analog or "slow scan" mode.

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