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

scholarly journals Mixing processes at an ice-covered river confluence

2018 ◽  
Vol 40 ◽  
pp. 05037
Author(s):  
Pascale M. Biron ◽  
Thomas Buffin-Bélanger ◽  
Nancy Martel
Keyword(s):  
Flow Structure ◽  
Coherent Structures ◽  
Three Dimensional ◽  
Ice Cover ◽  
Velocity Profiles ◽  
Medium Size ◽  
Mixing Zone ◽  
Turbulent Structures ◽  
Lateral Velocity ◽  
River Confluence

River confluences are characterized by a complex mixing zone with three-dimensional turbulent structures, which can be affected by the presence of an ice cover during the winter. The objective of this study is to characterize the flow structure in the mixing zone at a medium-size (~ 40 m) river confluence with and without an ice cover. Detailed velocity profiles were collected under the ice along the mixing plane with an Acoustic Doppler Velocimeter. For the ice-free conditions, drone imagery was used to characterize the mixing layer structures for various flow stages. Results indicate that during the ice-free conditions, very large Kelvin-Helmholtz (KH) coherent structures are visible due to turbidity differences, and occupy up to 50% of the width of the parent channel. During winter, the ice cover affects velocity profiles by moving the highest velocities towards the center of the profiles. Large turbulent structures are visible in both the streamwise and lateral velocity components. The strong correlation between these velocity components indicates that KH vortices are the dominating coherent structures in the mixing zone. A spatio-temporal conceptual model is presented to illustrate the main differences on the three-dimensional flow structure at the river confluence with and without the ice cover.

Numerical simulations and analysis of the turbulent flow field in a practical gas turbine engine combustor

2021 ◽  
pp. 095765092110632
Author(s):  
Veeraraghava R Hasti ◽  
Prithwish Kundu ◽  
Sibendu Som ◽  
Jay P Gore
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Gas Turbine ◽  
Adaptive Mesh Refinement ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Turbulent Structures ◽  
Cut Cell ◽  
Turbulent Flow Field

The turbulent flow field in a practical gas turbine combustor is very complex because of the interactions between various flows resulting from components like multiple types of swirlers, dilution holes, and liner effusion cooling holes. Numerical simulations of flows in such complex combustor configurations are challenging. The challenges result from (a) the complexities of the interfaces between multiple three-dimensional shear layers, (b) the need for proper treatment of a large number of tiny effusion holes with multiple angles, and (c) the requirements for fast turnaround times in support of engineering design optimization. Both the Reynolds averaged Navier–Stokes simulation (RANS) and the large eddy simulation (LES) for the practical combustor geometry are considered. An autonomous meshing using the cut-cell Cartesian method and adaptive mesh refinement (AMR) is demonstrated for the first time to simulate the flow in a practical combustor geometry. The numerical studies include a set of computations of flows under a prescribed pressure drop across the passage of interest and another set of computations with all passages open with a specified total flow rate at the plenum inlet and the pressure at the exit. For both sets, the results of the RANS and the LES flow computations agree with each other and with the corresponding measurements. The results from the high-resolution LES simulations are utilized to gain fundamental insights into the complex turbulent flow field by examining the profiles of the velocity, the vorticity, and the turbulent kinetic energy. The dynamics of the turbulent structures are well captured in the results of the LES simulations.

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 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.

scholarly journals Numerical Investigation of Powered Jet Effects by RANS/LES Hybrid Methods

2019 ◽  
Vol 37 (3) ◽  
pp. 565-571
Author(s):  
Zhibin Gong ◽  
Jie Li ◽  
Jixiang Shan ◽  
Heng Zhang
Keyword(s):  
Numerical Investigation ◽  
Hybrid Methods ◽  
Three Dimensional ◽  
Jet Flow ◽  
Weno Scheme ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Ambient Flow ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

For the high-precision simulation of engine jet effects, an improved delayed detached eddy simulation (IDDES) method based on the two-equation shear stress transport (SST) model is developed, and the fifth-order finite-volume weighted essentially non-oscillatory (WENO) scheme is employed to enhance accuracy of spatial discretization, and then numerical investigation of powered jet effects by RANS/LES hybrid methods is carried out. The effects of the grid distributions and the accuracy of the spatial schemes are discussed during the RANS/LES validation analysis on the fully expanded jet flow and Acoustic Reference Nozzle (ARN) jet flow. The results show that, by enlarging the grid density and improving the accuracy of the spatial schemes, the velocity distributions in the jet flow can be better predicted, the non-physical steady flow after the jet nozzle can be shortened, the instantaneous flow structures are clearer and the turbulent intensities are more accurate. Then IDDES simulation of turbofan engine jet flow is carried out. The mixing characteristics of the external fan jet flow and internal core jet flow as well as the ambient flow are obtained, and the three-dimensional turbulent structures are also given.

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