scholarly journals HIGHLY-RESOLVED NUMERICAL AND LABORATORY ANALYSIS FOR NONBREAKING SOLITARY WAVE SWASH OVER A STEEP SLOPE

2018 ◽  
pp. 36
Author(s):  
Pablo Higuera ◽  
Philip L.-F. Liu ◽  
Cheng Lin ◽  
Wei-Ying Wong ◽  
Ming-Jer Kao
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Solitary Wave ◽  
Hydraulic Jump ◽  
Laboratory Experiments ◽  
Vortex Formation ◽  
Steep Slope ◽  
Bottom Shear Stress ◽  
Flow Features ◽  
Produce Flow

In this paper we study the swash processes generated by a nonbreaking solitary wave running up and down a steep slope (1:3). We use experimental data to study flow features and velocities inside the boundary layer, and numerical modelling to investigate variables not measured during the laboratory experiments, such as pressures and bottom shear stress. We focus on the mechanisms that produce flow separation and vortex formation. Particularly, we study a system of vortices generated under a hydraulic jump during the rundown phase, which was first observed by Matsunaga & Honji (1980).

Laboratory-scale swash flows generated by a non-breaking solitary wave on a steep slope

2018 ◽  
Vol 847 ◽  
pp. 186-227 ◽  
Author(s):  
P. Higuera ◽  
P. L.-F. Liu ◽  
C. Lin ◽  
W.-Y. Wong ◽  
M.-J. Kao
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Solitary Wave ◽  
Numerical Simulations ◽  
Hydraulic Jump ◽  
High Speed ◽  
Laboratory Experiments ◽  
Numerical Solutions ◽  
Steep Slope ◽  
Bottom Shear Stress

The main goal of this paper is to provide insights into swash flow dynamics, generated by a non-breaking solitary wave on a steep slope. Both laboratory experiments and numerical simulations are conducted to investigate the details of runup and rundown processes. Special attention is given to the evolution of the bottom boundary layer over the slope in terms of flow separation, vortex formation and the development of a hydraulic jump during the rundown phase. Laboratory experiments were performed to measure the flow velocity fields by means of high-speed particle image velocimetry (HSPIV). Detailed pathline patterns of the swash flows and free-surface profiles were also visualized. Highly resolved computational fluid dynamics (CFD) simulations were carried out. Numerical results are compared with laboratory measurements with a focus on the velocities inside the boundary layer. The overall agreement is excellent during the initial stage of the runup process. However, discrepancies in the model/data comparison grow as time advances because the numerical model does not simulate the shoreline dynamics accurately. Introducing small temporal and spatial shifts in the comparison yields adequate agreement during the entire rundown process. Highly resolved numerical solutions are used to study physical variables that are not measured in laboratory experiments (e.g. pressure field and bottom shear stress). It is shown that the main mechanism for vortex shedding is correlated with the large pressure gradient along the slope as the rundown flow transitions from supercritical to subcritical, under the developing hydraulic jump. Furthermore, the bottom shear stress analysis indicates that the largest values occur at the shoreline and that the relatively large bottom shear stress also takes place within the supercritical flow region, being associated with the backwash vortex system rather than the plunging wave. It is clearly demonstrated that the combination of laboratory observations and numerical simulations have indeed provided significant insights into the swash flow processes.

Study on Flow Fields of Boundary-Layer Separation and Hydraulic Jump during Rundown Motion of Shoaling Solitary Wave

2015 ◽  
Vol 09 (05) ◽  
pp. 1540002 ◽  
Author(s):  
Chang Lin ◽  
Ming-Jer Kao ◽  
Guang-Wei Tzeng ◽  
Wei-Ying Wong ◽  
James Yang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Solitary Wave ◽  
Shear Layer ◽  
Flow Separation ◽  
Hydraulic Jump ◽  
High Speed ◽  
Flow Fields ◽  
Main Stream ◽  
Separated Shear Layer

The characteristics of flow fields for a complete evolution of the non-breaking solitary wave, having a wave-height to water-depth ratio of 0.363 and propagating over a 1:5 sloping bottom, are investigated experimentally. This study mainly focuses on the occurrences of both flow separation on the boundary layer under an adverse pressure gradient and subsequent hydraulic jump with the abrupt rising of free surface during rundown motion of the shoaling wave, together with emphasis on the evolution of vortex structures underlying the separated shear layer and hydraulic jump. A flow visualization technique with particle trajectory method and a high-speed particle image velocimetry (HSPIV) system with a high-speed digital camera were used. Based on the instantaneous flow images visualized and/or the ensemble-averaged velocity fields measured, the following interesting features, which are unknown up-to-date, are presented and discussed in this study: (1) Flow bifurcation occurring on both offshore and onshore sides of the explicit demarcation curve and the stagnation point during runup motion; (2) The dependence of the diffuser-like flow field, being changed from the supercritical flow in the shallower region to the subcritical flow in the deeper counterpart, on the Froude number during the early and middle stages of rundown motion; (3) The positions and times for the occurrences of the incipient flow separation and the sudden rising of free surface of the hydraulic jump; (4) The associated movement and evolution of vortex structures under the separated shear layer, the hydraulic jump and/or the high-speed external main stream of the retreated flow; and (5) The entrainment of air bubbles from the free surface into the external main stream of the retreated flow.

Oxygen Transfer through Air Entrainment over Stepped Weir

2015 ◽  
Vol 744-746 ◽  
pp. 2297-2300
Author(s):  
Jin Hong Kim
Keyword(s):  
Water Treatment ◽  
Oxygen Transfer ◽  
Hydraulic Jump ◽  
Laboratory Experiments ◽  
Air Entrainment ◽  
Air Pocket ◽  
Oxygen Transfer Efficiency ◽  
Flow Features ◽  
Inception Point ◽  
Free Falling

Oxygen transfer through the air entrainment over the stepped weir by the flow types was presented through the laboratory experiments. In the nappe flow, dominant flow features included an enclosed air pocket, a free-falling nappe impact and subsequent hydraulic jump on the downstream step. Most air was entrained through a free-falling nappe impact and a hydraulic jump. In the skimming flow, air entrainment occurs from the step edges. Downstream of the inception point, the flow is highly aerated at each and every step with very significant splashing. The average values of the oxygen transfer efficiency in the region of the nappe flow and of the skimming flow are about 0.40 and 0.28, respectively. The stepped type of the weir was found to be efficient for water treatment associated with substantial air entrainment.

Spontaneous breaking of reflexional symmetry in real quasi-two-dimensional turbulence: stochastic travelling waves and helical solitons in atmosphere and laboratory

1993 ◽  
Vol 441 (1911) ◽  
pp. 147-155 ◽  
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Laboratory Experiments ◽  
Travelling Waves ◽  
Qualitative Difference ◽  
Three Dimensional ◽  
Spontaneous Breaking ◽  
Two Dimensional ◽  
Boundary Layer Turbulence ◽  
The Difference

The theme of this note is the qualitative difference between strictly two-dimensional (2D) and quasi-two-dimensional (Q2D) turbulence in spite of the ‘smallness’ of the difference in their geometry. It is argued that the Q2D régime arises as a result of a spontaneous breaking of reflexional symmetry, which in turn is a consequence of the instability of 2D turbulence to three-dimensional helical travelling waves and solitons (through super-critical and sub-critical bifurcations). The difference between 2D and Q2D turbulence, which is primarily of a topological nature (related to helicity and super helicity) is manifested in different spectral and diffusive properties. The arguments are supported by a large number of experimental data from laboratory experiments (stably stratified, rotating, magnetohydrodynamic and boundary layer turbulence) and from observations in the stratosphere.

scholarly journals Assessment of BSL kω Turbulence Model for Predicting Flow Characteristics in a Solitary Wave Motion

2021 ◽  
Vol 930 (1) ◽  
pp. 012004
Author(s):  
B Winarta ◽  
A A N Satria Damarnegara ◽  
N N Atukimat ◽  
P T Juwono ◽  
E Suhartanto ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Solitary Wave ◽  
Wave Motion ◽  
Flow Characteristics ◽  
Deep Understanding ◽  
Bottom Shear Stress ◽  
Generation System ◽  
Transport Calculation ◽  
Closed Conduit

Abstract A deep understanding of boundary layer characteristics under wave motion, especially bottom shear stress on the seabed, is critical in sediment transport calculation and modeling. In this present study, boundary layer characteristics under solitary wave motion over the smooth bed are investigated through the Baseline (BSL) kω model. It will also consider the result of a laboratory experiment performed in a closed conduit generation system. The conclusion said that the BSL kω model can replicate well on horizontal and vertical velocity distribution at Reynolds number (Re) = 2.25 x 105. In addition, a turbulent spike which was occurred during decelerating phases of oscillatory motion can be predicted well also by the BSL kω model at Reynolds number (Re) = 6.06 x 105.

scholarly journals Large Eddy Simulation of Microvortex Generators in a Turbulent Boundary Layer

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Andrew P. Heffron ◽  
John J. Williams ◽  
Eldad J. Avital
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Separation Bubble ◽  
Vortex Formation ◽  
Leading Edge ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features ◽  
Challenging Environment

Abstract This study investigates the flow physics on microvortex generators (MVGs) in order to improve their performance in turbulent boundary layers (TBLs). TBLs can be a challenging environment for MVGs because of the streamwise length of the generated vortex and the increased parasitic drag of the MVGs. Large eddy simulation (LES) is used to properly resolve the turbulent boundary layer of a flat-plate with a zero-pressure gradient and MVG vane. Three different vane-types are investigated (e423-Mod, triangular, and rectangular vanes) and are studied in a single vane configuration. Important flow features such as a separation bubble on the leading edge of the rectangular vanes which introduced unsteadiness into the vortex formation and degraded the MVG's efficiency was observed. The e423-Mod and triangular vanes were observed to be more aerodynamically efficient. The triangular vane was found to be the most efficient when evaluated immediately downstream of the vane. However, the vortex from the triangular vane decayed very rapidly due to it being formed very close to the wall which degraded its efficiency further downstream. The e423-Mod vane avoided this problem but its drag was very high relative to the strength of the generated vortex and its vortex experienced a brief period of rapid decay immediately downstream decreasing its efficiency. Further downstream, the vortex of the rectangular vane at 16 deg became the most efficient through a combination of low vane drag and low vortex decay in the TBL, demonstrating the need to consider a range of issues when designing an MVG.

scholarly journals Modelling time efficiency of cobot-supported kit preparation

2019 ◽  
Vol 106 (5-6) ◽  
pp. 2227-2241 ◽  
Author(s):  
Patrik Fager ◽  
Martina Calzavara ◽  
Fabio Sgarbossa
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Cycle Time ◽  
Laboratory Experiments ◽  
Spare Parts ◽  
Batch Preparation ◽  
Assembly Quality ◽  
Numerical Example ◽  
Business To Business ◽  
Support Time

AbstractKitting – meaning to supply assembly with components in presorted kits – is widely seen as beneficial for assembly quality and efficiency when there is a multitude of component variants. However, the process by which kits are prepared – the kit preparation – is labour-intensive, and kit errors are problematic at assembly processes. The use of robotics to support kit preparation has received some attention by researchers, but literature is lacking with respect to how collaborative robots – cobots – can support kit preparation activities. The purpose of this paper is to identify the potential of a cobot to support time-efficient batch preparation of kits. To address the purpose, the paper presents a mathematical model for estimation of the cycle time associated with cobot-supported kit preparation. The model is applied in a numerical example with experimental data from laboratory experiments, and cobot-supported kit preparation is compared with manual kit preparation. The findings suggest that cobot-supported kit preparation is beneficial with diverse kits and smaller components quantities per SKU (Stock Keeping Unit) and provides less variability of the outcome, when compared to manual kit preparation. The paper reveals several insights about cobot-supported kit preparation that can be valuable for both academics and practitioners. The model developed can be used by practitioners to assess the potential of cobots to support kit-batch preparation in association with assembly, spare parts, repair and maintenance, or business to business industry.

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