scholarly journals Oblique impact of a smooth body on a thin layer of inviscid liquid

2013 ◽  
Vol 469 (2151) ◽  
pp. 20120615 ◽  
Author(s):  
T. I. Khabakhpasheva ◽  
A. A. Korobkin
Keyword(s):  
Body Surface ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Hydrodynamic Pressure ◽  
Oblique Impact ◽  
The Body ◽  
Second Stage ◽  
Smooth Body ◽  
Vertical Displacements ◽  
The Impact

The two-dimensional motion of a rigid body with a smooth surface is studied during its oblique impact on a liquid layer. The problem is coupled: the three degrees of freedom of the moving body are determined together with the liquid flow and the hydrodynamic pressure along the wetted part of the body surface. The impact process is divided into two temporal stages. During the first stage, the wetted region expands at a high speed with jetting flows at both ends of the wetted region. In the second stage, the free surface of the liquid is allowed to separate from the body surface. The position of the separation point is determined with the help of the Brillouin–Villat condition. Calculations are performed for elliptic cylinders of different masses and with different orientations and speeds before the impact. The horizontal and vertical displacements of the body, as well as its angle of rotation and corresponding speeds are investigated. The model developed remains valid until the body either touches the bottom of the liquid or rebounds from the liquid.

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.

Benchmarking the efficiencies of Indonesia’s municipal water utilities using Stackelberg data envelopment analysis

2015 ◽  
Vol 22 (4) ◽  
pp. 588-609 ◽  
Author(s):  
Andreas Wibowo ◽  
Hans Wilhelm Alfen
Keyword(s):  
Data Envelopment Analysis ◽  
The Body ◽  
Water Utilities ◽  
Data Envelopment ◽  
Two Stage ◽  
Restrictive Assumption ◽  
Content Type ◽  
Second Stage ◽  
Municipal Water ◽  
The Impact

Purpose – The purpose of this paper is to present a yardstick efficiency comparison of 269 Indonesian municipal water utilities (MWUs) and measures the impact of exogenous environmental variables on efficiency scores. Design/methodology/approach – Two-stage Stackelberg leader-follower data envelopment analysis (DEA) and artificial neural networks (ANN) were employed. Findings – Given that serviceability was treated as the leader and profitability as the follower, the first and second stage DEA scores were 55 and 32 percent (0 percent = totally inefficient, 100 percent = perfectly efficient), respectively. This indicates sizeable opportunities for improvement, with 39 percent of the total sample facing serious problems in both first- and second-stage efficiencies. When profitability instead leads serviceability, this results in more decreased efficiency. The size of the population served was the most important exogenous environmental variable affecting DEA efficiency scores in both the first and second stages. Research limitations/implications – The present study was limited by the overly restrictive assumption that all MWUs operate at a constant-return-to-scale. Practical implications – These research findings will enable better management of the MWUs in question, allowing their current level of performance to be objectively compared with that of their peers, both in terms of scale and area of operation. These findings will also help the government prioritize assistance measures for MWUs that are suffering from acute performance gaps, and to devise a strategic national plan to revitalize Indonesia’s water sector. Originality/value – This paper enriches the body of knowledge by filling in knowledge gaps relating to benchmarking in Indonesia’s water industry, as well as in the application of ensemble two-stage DEA and ANN, which are still rare in the literature.

Theoretical Study of the Water Entry of a Body in Waves: Application to Safety of Occupants in Free-Fall Lifeboats

2009 ◽  
Author(s):  
Thomas Sauder ◽  
Se´bastien Fouques
Keyword(s):  
Water Waves ◽  
Degrees Of Freedom ◽  
Mass Matrix ◽  
Free Fall ◽  
Theoretical Method ◽  
Emergency Evacuation ◽  
Momentum Conservation ◽  
The Body ◽  
Water Impact ◽  
The Impact

The safety of occupants in free-fall lifeboats (FFL) during water impact is addressed. The first part of the paper describes a theoretical method developed to predict the trajectory in six degrees of freedom of a body entering water waves. Slamming forces and moments are computed, based on momentum conservation, long wave approximation and a von Karman type of approach. The added mass matrix of the body is evaluated for impact conditions by a boundary element method. The second part of the paper focuses on the application of the method to free-fall lifeboats, which are used for emergency evacuation of oil platforms or ships. Acceleration loads on FFL occupants during water impact are dependent on numerous parameters, especially the hull shape, the mass distribution, the wave heading relative to the lifeboat, and the impact point on the wave surface. Assessing operational limits of FFL by means of model tests only has therefore been costly and time consuming. This issue is addressed here by applying the theoretical method described in the first part. The model has been validated for FFL through extensive model testing in calm water and regular waves, and statistical estimates of acceleration levels for lifeboat occupants, as well as acceleration time series were obtained that can be used as inputs to numerical human response models.

Kinematic Analysis of a Five-Legged Mobile Robot

2010 ◽  
Author(s):  
Muhammed R. Pac ◽  
Dan O. Popa
Keyword(s):  
Kinematic Analysis ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Parallel Robots ◽  
The Body ◽  
Legged Robots ◽  
Upper Body ◽  
Design Changes ◽  
Robot Performance ◽  
The Impact

Legged robots are more maneuverable, and can negotiate rough terrain much better than conventional locomotion using wheels. However, since the kinematic or dynamic analysis of such robots involves closed chains, it is typically more difficult to investigate the impact of design changes, such as the number, or the design of its legs, to robot performance. Most legged robots consist of 4 legs (quadrupeds) or 6 legs (hexapods). This paper discusses the kinematic analysis of an unconventional, symmetrical 5-legged robot with 2-DOF (Degrees Of Freedom) universal joints in each leg. The analysis was carried out in order to predict the mobility of the upper body platform, and investigate the number of robot actuators needed for mobility. The product of exponentials formulation with respect to the local coordinate frames is used to describe the twists of the joints. The analysis is based on the idea that the robot body platform along with the legs can be considered instantaneously as a parallel robot manipulating the ground. Hence, the analysis can be done using the Jacobian formulation of parallel robots. Simulation results confirm the mobility analysis that the robot can have at most 3-DOF for the body and that these freedoms are coupled rotations and translations in 3D space also with a dependence on the configuration of the robot.

scholarly journals Composition of Multiple D.O.F. Robot Control System Using a Parallel Processing Microcomputer

1990 ◽  
Vol 2 (3) ◽  
pp. 189-193
Author(s):  
Shigeki Sugano ◽  
Keyword(s):  
Control System ◽  
Parallel Processing ◽  
Software Design ◽  
High Speed ◽  
Robot Control ◽  
Degrees Of Freedom ◽  
The Body ◽  
Concurrent System ◽  
Parallel Connection ◽  
Multiple Degrees Of Freedom

In this paper, a method of composition for a multimicroprocessor robotic systems and a concrete example of a mobile anthropomorphic manipulator are discussed. There are many methods to compose multimicroprocessor systems for robots and complex mechatronic units. It is most advantageous for multiple degrees of freedom robots to introduce a concurrent system employing microcomputers designed on the premise of parallel connection, as it is easy to realize high speed and efficiency. In addition, hardware and software design as well as related debugging is very easy. A mobile anthropomorphic manipulator (WAM-9) with 7 d.o.f. in the arm, 16 d.o.f. in the hand and 3 d.o.f. in the body has been developed aimed at improving the robot dexterity. The control system of WAM-9 employs a 32-bit ""Transputer"" parallel processing microcomputer. This system includes about 20 transputers and is modeled after the human central nervous system.

scholarly journals Propagation of a Plastic Wave in Snow

1977 ◽  
Vol 19 (81) ◽  
pp. 175-183 ◽  
Author(s):  
Gorow Wakahama ◽  
Atsushi Sato
Keyword(s):  
Water Content ◽  
Wave Velocity ◽  
High Speed ◽  
Free Water ◽  
The Body ◽  
High Rate ◽  
Plastic Wave ◽  
Free Water Content ◽  
Moving Body ◽  
The Impact

AbstractWhen snow is pushed very fast by a moving body a plastic wave is generated at the head of the body. If the velocity of the moving body becomes close to that of the plastic wave, the snow may exert a great resistive force against the body as predicted by Yosida. It is, therefore, very important to study the dynamic behaviour of snow at a high rate of deformation, such as takes place when a snow plough is used on the highway, a train runs on a railroad covered with snow, or an avalanche occurs. Hence, this study is concerned with the safety and maintenance of winter traffic and transportation, and also with the generation and propagation of an avalanche. In order to clarify the detailed processes of the deformation of snow at high rates, laboratory experiments were made by compressing snow at high speed. The propagation of a plastic wave through snow was observed by using a high-speed camera and a pressure-detecting device. Analyses of the data obtained gave the velocity of the plastic wave for various kinds of snow whose density ranged from 0.17 to 0.46 Mg m-3and free-water content from o to 17%, whereby studies were made into the dependences on the density and free-water content of the velocity of the plastic wave. When the impact velocity was 4.3 ± 0.2 m s-1, the wave velocity ranged from 5 m s-1for a new snow to 12 m s-1for a fine-grained, well-settled snow. The plastic-wave velocity in wet snow was, in general, smaller than that in dry snow of the same density. Changes in density and structure of snow associated with the passage of a plastic wave were studied and discussed. The pressure at the wave front was measured; values of 0.1-0.3 bar were obtained, these are of the same order as the value estimated from theoretical formulae. The plastic-wave velocity was also observed for a confined snow, which showed a larger velocity and plastic strain than an unconfined snow.

scholarly journals Propagation of a Plastic Wave in Snow

1977 ◽  
Vol 19 (81) ◽  
pp. 175-183 ◽  
Author(s):  
Gorow Wakahama ◽  
Atsushi Sato
Keyword(s):  
Water Content ◽  
Wave Velocity ◽  
High Speed ◽  
Free Water ◽  
The Body ◽  
High Rate ◽  
Plastic Wave ◽  
Free Water Content ◽  
Moving Body ◽  
The Impact

AbstractWhen snow is pushed very fast by a moving body a plastic wave is generated at the head of the body. If the velocity of the moving body becomes close to that of the plastic wave, the snow may exert a great resistive force against the body as predicted by Yosida. It is, therefore, very important to study the dynamic behaviour of snow at a high rate of deformation, such as takes place when a snow plough is used on the highway, a train runs on a railroad covered with snow, or an avalanche occurs. Hence, this study is concerned with the safety and maintenance of winter traffic and transportation, and also with the generation and propagation of an avalanche. In order to clarify the detailed processes of the deformation of snow at high rates, laboratory experiments were made by compressing snow at high speed. The propagation of a plastic wave through snow was observed by using a high-speed camera and a pressure-detecting device. Analyses of the data obtained gave the velocity of the plastic wave for various kinds of snow whose density ranged from 0.17 to 0.46 Mg m-3 and free-water content from o to 17%, whereby studies were made into the dependences on the density and free-water content of the velocity of the plastic wave. When the impact velocity was 4.3 ± 0.2 m s-1, the wave velocity ranged from 5 m s-1 for a new snow to 12 m s-1 for a fine-grained, well-settled snow. The plastic-wave velocity in wet snow was, in general, smaller than that in dry snow of the same density. Changes in density and structure of snow associated with the passage of a plastic wave were studied and discussed. The pressure at the wave front was measured; values of 0.1-0.3 bar were obtained, these are of the same order as the value estimated from theoretical formulae. The plastic-wave velocity was also observed for a confined snow, which showed a larger velocity and plastic strain than an unconfined snow.

scholarly journals The impact of pelvic lateral rotation on hindlimb kinematics and stride length in the red-legged running frog, Kassina maculata

2019 ◽  
Vol 6 (5) ◽  
pp. 190060 ◽  
Author(s):  
Amber J. Collings ◽  
Laura B. Porro ◽  
Cameron Hill ◽  
Christopher T. Richards
Keyword(s):  
High Speed ◽  
Stride Length ◽  
Reference Frames ◽  
Comparative Anatomy ◽  
Three Dimensional ◽  
Video Data ◽  
The Body ◽  
Kinematic Models ◽  
Lateral Rotation ◽  
The Impact

Some frog species, such as Kassina maculata (red-legged running frog), use an asynchronous walking/running gait as their primary locomotor mode. Prior comparative anatomy work has suggested that lateral rotation of the pelvis improves walking performance by increasing hindlimb stride length; however, this hypothesis has never been tested. Using non-invasive methods, experimental high-speed video data collected from eight animals were used to create two three-dimensional kinematic models. These models, each fixed to alternative local anatomical reference frames, were used to investigate the hypothesis that lateral rotation of the mobile ilio-sacral joint in the anuran pelvis plays a propulsive role in walking locomotion by increasing hindlimb stride length. All frogs used a walking gait (duty factor greater than 0.5) despite travelling over a range of speeds (0.04–0.23 m s −1 ). The hindlimb joint motions throughout a single stride were temporally synchronized with lateral rotation of the pelvis. The pelvis itself, on average, underwent an angular excursion of 12.71° (±4.39°) with respect to the body midline during lateral rotation. However, comparison between our two kinematic models demonstrated that lateral rotation of the pelvis only increases the cranio-caudal excursion of the hindlimb modestly. Thus, we propose that pelvic lateral rotation is not a stride length augmenting mechanism in K. maculata .

A study on the frontal oblique collision-induced derailment mechanism in subway vehicles

2019 ◽  
Vol 234 (6) ◽  
pp. 584-595
Author(s):  
Shuguang Yao ◽  
Huifen Zhu ◽  
Mingyang Liu ◽  
Zhixiang Li ◽  
Ping Xu ◽  
...  
Keyword(s):  
Lateral Displacement ◽  
Element Model ◽  
Vertical Displacement ◽  
Rigid Wall ◽  
Impact Angle ◽  
Oblique Impact ◽  
Oblique Collision ◽  
Impact Speed ◽  
Vertical Displacements ◽  
The Impact

Oblique collisions can more easily lead to train derailment and cause heavy casualties. In this paper, a fine finite-element model of a subway head vehicle–rigid wall frontal oblique collision was established and validated by a single wheelset derailment simulation. Furthermore, the derailment mechanisms and patterns under an oblique impact angle of 6.34°–40° and at an impact speed of 8–40 km/h were studied via simulation. The results indicated that three types of derailment, such as roll-over derailment, climb/roll-over derailment and wheel-lift derailment, have occurred. When the impact speed was set to 25 km/h, a climb/roll-over derailment occurred under the impact angle of greater than 40°; a roll-over derailment occurred under the impact angle of 20°–40°; and the vehicle would not derail when the impact angle was less than 15°. When the impact angle was 6.34°, the vehicle was in danger of wheel-lift derailment with the largest wheel vertical displacement of 26.83 mm and lateral displacement of 12.52 mm under the impact speed of 40 km/h, but it was safe with the largest displacement of no more than 18 mm and lateral displacement of 8.39 mm if the impact speed was less than 40 km/h. It is shown that the derailment patterns are more sensitive to the impact angle. Therefore, both the lateral and vertical displacements should be considered when studying the oblique collision-induced derailment mechanisms and patterns.

scholarly journals Investigation of the psychophysiological response of passengers of fast trains with the different comfort level

2021 ◽  
Vol 100 (4) ◽  
pp. 318-326
Author(s):  
Evgeniy Yu. Bersenev ◽  
Vladimir I. Dubinin ◽  
Vyacheslav M. Ermakov ◽  
Anna I. Kirpicheva
Keyword(s):  
High Speed ◽  
The Body ◽  
Comfort Level ◽  
Movement Speed ◽  
Rolling Stock ◽  
Technical Data ◽  
Normative Documents ◽  
Staff Members ◽  
High Speed Trains ◽  
The Impact

Introduction. To create a regulatory framework, including harmonized with European normative documents in terms of assessing passengers’ comfort, the standard of the enterprise STO RZD “Services in railway transport was developed. Rules for assessing the level of comfort of passengers on trains.” The objective of the study is to compare the indices of the comfort level of passengers, determined by the values of the accelerations acting on them, with the psychological sensations and physiological changes in the body arising in this case, depending on the rolling stock and the state of the track. Material and methods. The experiment using ECG monitoring devices was carried out in four groups of eleven people, six men and five women aged 30-55 years. Additionally, in each group, a psychological survey of 11 more passengers was carried out. All of them were staff members of the Russian Railways divisions. Results. When traveling on high-speed trains “Lastochka” and “Sapsan,” the respondents more often note drowsiness and an exhausted state’s progression. At the end of the trip, they often emphasize stiffness, discomfort, numbness, and numbness of the leg muscles, probably associated with an extended stay in a forced position in the absence of specific freedom movements. In the “lying” position, a person experiences less fatigue, which, according to the sensations, hardly differs from the conditions of a trip in a “sitting” position during short journeys. Regulatory changes in the cardiovascular system are manifested with the combined influence of uncanceled accelerations (the impact of centrifugal forces) and movement speed changes. Conclusion. Carrying out a questionnaire survey and physiological measurements of the dynamics of heart rate fluctuations on the investigated sections of the routes in combination with the obtained technical data on the nature of mobile rail vehicles’ movement confirm the absence of critical discomfort for passengers when traveling on passenger and high-speed trains. The calculated values of the average and constant comfort levels are consistent and do not require correction of the corresponding scales’ values.

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