scholarly journals RIGHTING OF CHINESE MITTEN CRABS (ERIOCHEIR SINENSIS) AND THEIR MODELS

2016 ◽  
Vol 7 ◽  
pp. 53
Author(s):  
Tobias Riphaus ◽  
Florian Hoffmann ◽  
Susanna Labisch
Keyword(s):  
High Speed ◽  
Particle Image ◽  
Numerical Models ◽  
Rotational Velocity ◽  
Underwater Vehicles ◽  
Eriocheir Sinensis ◽  
Unmanned Underwater Vehicles ◽  
Starting Position ◽  
Image Velocimetry ◽  
Mitten Crabs

The usage of unmanned underwater vehicles for marine tasks is continuously growing and bioinspired stabilizing systems shall help them to gain and keep a stable position during work. Therefore the righting maneuver of E. sinensis has been studied. These crabs are able to perform a 180°-rotation with an angular velocity of 4.30 s<sup>−1</sup> when falling underwater from a supine starting position. High-speed particle image velocimetry has shown, that propulsive forces with a peak of 0.021 ± 0.001 N were produced by the hind legs to initiate and stop the rotation. In a numerical multibody simulation a constant force of 0.009 N acting for 0.2 s leads to the same rotation. In order to prove this mechanism, it was implemented into a robotic system. Its mean density of 1.15 g/cm<sup>3</sup> deviates not more than 4% from the biological and numerical models. It can complete a 180°-turn within 1.03 ± 0.12 s with a rotational velocity of up to 4.25 s<sup>−1</sup>.

An experimental and numerical study of the resonant flow between a hull and a wall

2021 ◽  
Vol 930 ◽  
Author(s):  
I.A. Milne ◽  
O. Kimmoun ◽  
J.M.R. Graham ◽  
B. Molin
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Numerical Study ◽  
Numerical Models ◽  
Vertical Wall ◽  
Liquefied Natural Gas ◽  
Narrow Gap ◽  
Image Velocimetry ◽  
High Degree ◽  
Wave Induced

The wave-induced resonant flow in a narrow gap between a stationary hull and a vertical wall is studied experimentally and numerically. Vortex shedding from the sharp bilge edge of the hull gives rise to a quadratically damped free surface response in the gap, where the damping coefficient is approximately independent of wave steepness and frequency. Particle image velocimetry and direct numerical simulations were used to characterise the shedding dynamics and explore the influence of discretisation in the measurements and computations. Secondary separation was identified as a particular feature which occurred at the hull bilge in these gap flows. This can result in the generation of a system with multiple vortical regions and asymmetries between the inflow and outflow. The shedding dynamics was found to exhibit a high degree of invariance to the amplitude in the gap and the spanwise position of the barge. The new measurements and the evaluation of numerical models of varying fidelity can assist in informing offshore operations such as the side by side offloading from floating liquefied natural gas facilities.

scholarly journals Aerodynamics of manoeuvring flight in brown long-eared bats ( Plecotus auritus )

2018 ◽  
Vol 15 (148) ◽  
pp. 20180441 ◽  
Author(s):  
Per Henningsson ◽  
Lasse Jakobsen ◽  
Anders Hedenström
Keyword(s):  
Particle Image Velocimetry ◽  
Wind Tunnel ◽  
High Speed ◽  
Particle Image ◽  
Future Studies ◽  
Image Velocimetry ◽  
Mechanistic Basis

In this study, we explicitly examine the aerodynamics of manoeuvring flight in animals. We studied brown long-eared bats flying in a wind tunnel while performing basic sideways manoeuvres. We used particle image velocimetry in combination with high-speed filming to link aerodynamics and kinematics to understand the mechanistic basis of manoeuvres. We predicted that the bats would primarily use the downstroke to generate the asymmetries for the manoeuvre since it has been shown previously that the majority of forces are generated during this phase of the wingbeat. We found instead that the bats more often used the upstroke than they used the downstroke for this. We also found that the bats used both drag/thrust-based and lift-based asymmetries to perform the manoeuvre and that they even frequently switch between these within the course of a manoeuvre. We conclude that the bats used three main modes: lift asymmetries during downstroke, thrust/drag asymmetries during downstroke and thrust/drag asymmetries during upstroke. For future studies, we hypothesize that lift asymmetries are used for fast turns and thrust/drag for slow turns and that the choice between up- and downstroke depends on the timing of when the bat needs to generate asymmetries.

scholarly journals Dual-camera system for high-speed imaging in particle image velocimetry

2012 ◽  
Vol 15 (3) ◽  
pp. 193-195 ◽  
Author(s):  
K. Hashimoto ◽  
A. Hori ◽  
T. Hara ◽  
S. Onogi ◽  
H. Mouri
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
High Speed Imaging ◽  
Camera System ◽  
Image Velocimetry

Unveiling the Flow Behavior Inside GDI Engine Cylinder Using High-Speed Time-Resolved Particle Image Velocimetry and CFD Simulation

2021 ◽  
Author(s):  
Mohammed El Adawy ◽  
Morgan Heikal ◽  
bin Abd. Aziz Abd. Rashid
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
Cfd Simulation ◽  
Injection Pressure ◽  
Valve Lift ◽  
Fuel Spray ◽  
Time Resolved ◽  
Image Velocimetry ◽  
Spray Plume

Abstract RICARDO-VECTIS CFD simulation of the in-cylinder air flow was first validated with those of the experimental results from high-speed particle image velocimetry (PIV) measurements taking cognisant of the mid-cylinder tumble plane. Furthermore, high-speed fuel spray measurements were carried out simultaneously with the intake-generated tumble motion at high valve lift using high-speed time-resolved PIV to chronicle the spatial and time-based development of air/fuel mixture. The effect of injection pressure(32.5 and 35.0 MPa) and pressure variation across the air intake valves(150, 300 and 450 mmH2O) on the interaction process were investigated at valve lift 10 mm where the tumble vortex was fully developed and filled the whole cylinder under steady-state conditions. The PIV results illustrated that the intake generated-tumble motion had a substantial impact on the fuel spray distortion and dispersion inside the cylinder. During the onset of the injection process the tumble motion diverted the spray plume slightly towards the exhaust side before it followed completely the tumble vortex. The fuel spray plume required 7.2 ms, 6.2 ms and 5.9 ms to totally follow the in-cylinder air motion for pressure differences 150, 300 and 450 mmH2O, respectively. Despite, the spray momentum was the same for the same injection pressure, the magnitude of kinetic energy was different for different cases of pressure differences and subsequently the in-cylinder motion strength.

Comparative Evaluation of Single/Twin Round and Elliptic Jets Using Particle Image Velocimetry

2018 ◽  
Author(s):  
Seyed Sobhan Aleyasin ◽  
Mark Francis Tachie
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
Joint Probability ◽  
Strength Analysis ◽  
Round Jets ◽  
Image Velocimetry ◽  
Velocity Decay ◽  
Swirling Strength ◽  
Single Jet

Twin round and elliptic jets with nozzle spacing of S/d = 2.8 are investigated and the results are compared with those obtained from single jets. The measurements were performed at Re = 10000 using particle image velocimetry. The results show that the twin elliptic jets merge and combine faster than the round jets. However, the twin elliptic jets have lower spreading than their corresponding single jet but in the round jets it is opposite. The vortical structures obtained using swirling strength analysis are more intense in the elliptic jets compared with the round jets; consistent with their higher spreading. In the shear layers, the velocity skewness is considerably positive due to the diffusion of high-speed jet fluid towards the ambient. On the other hand, the streamwise skewness on the centerline is negative because of the entrainment of low-speed ambient fluid; resulting in centerline velocity decay. In addition, the joint and weighted joint probability density functions are used to understand the dominant events which contribute into the mixing of the jets with their surrounding fluid.

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