Modelling of three-dimensional flexural oscillations of an ice cover induced by a moving load

1991 ◽  
Vol 2 (4) ◽  
pp. 257-262
Author(s):  
A. E. Bukatov ◽  
V. V. Zharkov
Keyword(s):  
Moving Load ◽  
Three Dimensional ◽  
Ice Cover

scholarly journals Reconstruction of the Glacial Ice Covers of Greenland and the Canadian Arctic Islands by Three-Dimensional, Perfectly Plastic Ice-Sheet Modelling

1984 ◽  
Vol 5 ◽  
pp. 115-121 ◽  
Author(s):  
N. Reeh
Keyword(s):  
Flow Pattern ◽  
Bottom Topography ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Ice Cover ◽  
Glacial Ice ◽  
North West ◽  
Ice Caps ◽  
Perfectly Plastic

A three-dimensional perfectly plastic ice-sheet model, developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice-margin positions, is applied to the reconstruction of the glacial ice covers of Greenland and the Canadian Arctic islands. In the northern regions, two different reconstructions have been performed with ice margins along the present 600 and 200 m sea-depth contours, respectively. In central Greenland, the ice margin is considered to be at the outermost ice-margin deposits on the coastal shelf to the west, and at the present 200 m sea-depth contour to the east.The main conclusions to be drawn from the reconstructions are: (1). The flow pattern of the glacial ice cover of Greenland shows a great resemblance to the present one, the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today. (2). The main ice divide of the ice sheet covering the Canadian Arctic islands (the Innuitian ice sheet) was located over the highlands of eastern Ellesmere Island with local domes positioned over the present ice caps, indicating that even the deep ice of Wisconsin age in these ice caps is of local origin. This is also the case for the Devon Island ice cap. (3). Even in the not very likely case of a rather extensive glacial ice cover in north-west Greenland, the ice-flow pattern upstream of the Camp Century deep drill site would not have changed radically compared to the present flow pattern. Thus it is concluded that even advanced ice margins in late-Wisconsin time could at most have resulted in an elevation of the deposition site of the late-Wisconsin ice at Camp Century 600 m higher than at present. The consequences of this conclusion are discussed.

A New Three-Dimensional Moving Timoshenko Beam Element for Moving Load Problem Analysis

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Yan Xu ◽  
Weidong Zhu ◽  
Wei Fan ◽  
Caijing Yang ◽  
Weihua Zhang
Keyword(s):  
Dynamic Analysis ◽  
Coordinate System ◽  
Timoshenko Beam ◽  
Moving Load ◽  
Three Dimensional ◽  
Beam Element ◽  
Superposition Method ◽  
Reference Coordinate System ◽  
Current Formulation ◽  
Timoshenko Beam Element

Abstract A new three-dimensional moving Timoshenko beam element is developed for dynamic analysis of a moving load problem with a very long beam structure. The beam has small deformations and rotations, and bending, shear, and torsional deformations of the beam are considered. Since the dynamic responses of the beam are concentrated on a small region around the moving load and most of the long beam is at rest, owing to the damping effect, the beam is truncated with a finite length. A control volume that is attached to the moving load is introduced, which encloses the truncated beam, and a reference coordinate system is established on the left end of the truncated beam. The arbitrary Lagrangian–Euler method is used to describe the relationship of the position of a particle on the beam between the reference coordinate system and the global coordinate system. The truncated beam is spatially discretized using the current beam elements. Governing equations of a moving element are derived using Lagrange’s equations. While the whole beam needs to be discretized in the finite element method or modeled in the modal superposition method (MSM), only the truncated beam is discretized in the current formulation, which greatly reduces degrees-of-freedom and increases the efficiency. Furthermore, the efficiency of the present beam element is independent of the moving load speed, and the critical or supercritical speed range of the moving load can be analyzed through the present method. After the validation of the current formulation, a dynamic analysis of three-dimensional train–track interaction with a non-ballasted track is conducted. Results are in excellent agreement with those from the commercial software simpack where the MSM is used, and the calculation time of the current formulation is one-third of that of simpack. The current beam element is accurate and more efficient than the MSM for moving load problems of long three-dimensional beams. The derivation of the current beam element is straightforward, and the beam element can be easily extended for various other moving load problems.

Three‐dimensional turbulent structures at a medium‐sized confluence with and without an ice cover

2019 ◽  
Vol 44 (15) ◽  
pp. 3042-3056 ◽  
Author(s):  
Pascale M. Biron ◽  
Thomas Buffin‐Bélanger ◽  
Nancy Martel
Keyword(s):  
Three Dimensional ◽  
Ice Cover ◽  
Turbulent Structures

Three dimensional solution of thick rectangular simply supported plates under a moving load

Meccanica ◽  
2017 ◽  
Vol 52 (15) ◽  
pp. 3675-3692 ◽  
Author(s):  
Parvaneh Nateghi Babagi ◽  
Bahram Navayi Neya ◽  
Mehdi Dehestani
Keyword(s):  
Moving Load ◽  
Three Dimensional ◽  
Dimensional Solution ◽  
Simply Supported

scholarly journals INFLUENCE OF FRICTION IN THE ARMORED FACE CONVEYOR CHAIN ON DYNAMICS AND ENERGY EFFICIENCY

2021 ◽  
pp. 15-20
Author(s):  
Alexander Osichev ◽  
Andrii Tkachenko
Keyword(s):  
Energy Efficiency ◽  
Electric Drive ◽  
Dimensional Space ◽  
Moving Load ◽  
Three Dimensional ◽  
Viscous Friction ◽  
Spatial Form ◽  
Time Dynamic ◽  
Resonance Frequencies ◽  
Dimensional Space Time

The range of values ​​of the coefficient of resistance to movement of the chain of typical longwall armored face conveyors and the coefficient of inner viscous friction in the chain, both immersed in the moving load and during the idle run of the conveyor, is estimated. The computer model of the conveyor is built as a multi-mass elastic-viscous stretched closed chain without sag with the number of masses n = 200 and one induction drive motor located in the head of the conveyor. Using the constructed model, three-dimensional space-time dynamic characteristics of speeds and forces in the chain of the CP72 longwall armored face conveyor are obtained. Start up to rated speed v≈1 m / s and the working process is simulated with an unloaded conveyor. The spatial form of frictional self-oscillations in the model with distributed parameters is shown. The resonance frequencies and amplitudes of oscillations of the efforts in the circuit and the length of the corresponding spatial waves have been determined. It was found that at the first and second resonance frequencies, self-oscillations are not excited, since the damping effect of the electric drive is quite pronounced in this frequency band. The direct connection of vibration amplitudes with the energy efficiency of the conveyor electric drive is indicated.

scholarly journals Reconstruction of the Glacial Ice Covers of Greenland and the Canadian Arctic Islands by Three-Dimensional, Perfectly Plastic Ice-Sheet Modelling

1984 ◽  
Vol 5 ◽  
pp. 115-121 ◽  
Author(s):  
N. Reeh
Keyword(s):  
Flow Pattern ◽  
Bottom Topography ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Ice Cover ◽  
Glacial Ice ◽  
North West ◽  
Ice Caps ◽  
Perfectly Plastic

A three-dimensional perfectly plastic ice-sheet model, developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice-margin positions, is applied to the reconstruction of the glacial ice covers of Greenland and the Canadian Arctic islands. In the northern regions, two different reconstructions have been performed with ice margins along the present 600 and 200 m sea-depth contours, respectively. In central Greenland, the ice margin is considered to be at the outermost ice-margin deposits on the coastal shelf to the west, and at the present 200 m sea-depth contour to the east.The main conclusions to be drawn from the reconstructions are: (1). The flow pattern of the glacial ice cover of Greenland shows a great resemblance to the present one, the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today. (2). The main ice divide of the ice sheet covering the Canadian Arctic islands (the Innuitian ice sheet) was located over the highlands of eastern Ellesmere Island with local domes positioned over the present ice caps, indicating that even the deep ice of Wisconsin age in these ice caps is of local origin. This is also the case for the Devon Island ice cap. (3). Even in the not very likely case of a rather extensive glacial ice cover in north-west Greenland, the ice-flow pattern upstream of the Camp Century deep drill site would not have changed radically compared to the present flow pattern. Thus it is concluded that even advanced ice margins in late-Wisconsin time could at most have resulted in an elevation of the deposition site of the late-Wisconsin ice at Camp Century 600 m higher than at present. The consequences of this conclusion are discussed.

scholarly journals Bending-gravity waves in the sea with an ice cover from moving disturbances

2021 ◽  
pp. 157-161
Author(s):  
Ж.В. Маленко ◽  
А.А. Ярошенко
Keyword(s):  
Gravitational Waves ◽  
Gravity Waves ◽  
Elastic Waves ◽  
Isotropic Plate ◽  
Pure Water ◽  
Three Dimensional ◽  
Ice Cover ◽  
Ship Waves ◽  
Plate Vibrations ◽  
The Waves

В статье проводятся исследования колебаний плавающего ледяного покрова под действием движущихся возмущений. В основу колебаний плавающего ледяного покрова положены линеаризованные уравнения гидромеханики и линейная классическая теория колебаний пластин. Ледяной покров рассматривается как тонкая упругая изотропная пластинка. Анализируются образующиеся при этом трехмерные изгибно-гравитационные волны. Показано, что при движении источника возмущений со скоростью 0<v<v0 изгибно-гравитационные волны не образуются, а наблюдается статический прогиб. Здесь v0 – минимальное значение фазовой скорости. При скорости движения v0<v<v1 образуется одна система изгибно-гравитационных волн. Эти волны распространяются как впереди, так и за источником возмущений. Волны, бегущие впереди источника, обусловлены упругими и массовыми силами пластинки. Волны, распространяющиеся за источником, имеют характер гравитационной волны для чистой воды. При v1<v<(gH)1/2 образуется три системы волн. Упругие волны распространяются впереди источника. Две другие волны распространяются за источником и носят характер поперечной и продольной корабельных волн. При v>(gH)1/2 образуются впереди источника упругие волны, а за источником продольные корабельные волны. Исследовано влияние скорости перемещения нагрузки на амплитуды образующихся волн. The article studies the fluctuations of the floating ice cover under the action of moving perturbations. The vibrations of the floating ice cover are based on the linearized equations of hydro-mechanics and the linear classical theory of plate vibrations. The ice sheet is considered as a thin elastic isotropic plate. The resulting three-dimensional bending-gravity waves are analyzed. It is shown that when the source of disturbances moves at a speed of 0<v<v0, bending-gravitational waves are not formed, but a static deflection is observed. Here v0is the minimum value of the phase velocity. At the speed of motion v0<v<v1, a single system of bending-gravitational waves is formed. These waves propagate both ahead and behind the source of the disturbances. The waves traveling ahead of the source are caused by the elastic and mass forces of the plate. The waves propagating behind the source have the character of a gravitational wave for pure water. At v1<v<(gH)1/2, three wave systems are formed. Elastic waves propagate ahead of the source. The other two waves propagate behind the source and have the character of transverse and longitudinal ship waves. At v>(gH)1/2, elastic waves are formed in front of the source, and longitudinal ship waves are formed behind the source. The influence of the load displacement velocity on the amplitudes of the generated waves is investigated.

Three-dimensional numerical simulation of local scour in the vicinity of circular side-by-side bridge piers with ice cover

2020 ◽  
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui ◽  
Yongsheng Wu ◽  
Natalie Linklater
Keyword(s):  
Laboratory Experiments ◽  
Transport Model ◽  
Numerical Models ◽  
Three Dimensional ◽  
Ice Cover ◽  
Local Scour ◽  
Bridge Piers ◽  
Accurate Estimation ◽  
Scour Depth ◽  
Cold Regions

Local scour around piers is one of the primary causes of collapse of bridges that cross rivers. The most severe scouring occurs in cold regions where ice cover significantly changes the velocity profile. Having an accurate estimation of the maximum scour depth around bridge piers, especially in cold regions, is necessary for a safer design of piers. In this study, 3-D numerical models are compared to laboratory experiments to examine the process of local scour around bridge piers with and without smooth and rough ice cover. By using the equation of Meyer-Peter Müller, the sediment transport model is validated to approximate the transport of the sediment particles. Numerical results showed good agreements with experimental observations where the maximum scour depth and Turbulent Kinetic Energy (TKE) around bridge piers were the highest under rough ice cover conditions.

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