Large Scale Experimental Wave Impact on Walls in the Québec Coastal Physics Laboratory

2015 ◽  
Author(s):  
Jannette B. Frandsen ◽  
Francis Bérubé
Keyword(s):  
Large Scale ◽  
Peak Pressure ◽  
Vertical Wall ◽  
Test Series ◽  
Vertical Force ◽  
Wave Impact ◽  
Physics Laboratory ◽  
Air Pocket ◽  
Jet Velocity ◽  
Plunging Breaker

The present tests are conducted in the new Québec Coastal Physics Laboratory, Canada. The flume has a depth and a width of 5 m and is 120 m long. This paper presents large scale experiments of water wave impact on a vertical wall following wave runup on a mixed sand-gravel-cobble beach. This present study is concerned with advancing knowledge on rapidly varying pressure magnitude and distributions on different types of sea/river/harbor walls. Protection against extreme events and subsequent coastal erosion is a key theme of application. Herein is presented preliminary test series which has focus on forces on vertical walls. Specifically, 27 pressure sensors are mounted on the vertical wall with a total test area of 1.2 m wide and 2.4 m high and is a stiffened aluminum plate. The outer regions of the wall are made of steel to span the entire width of the tank. The wall is designed to behave as a rigid plate. The geometric model to full scale is about 1:4. The incoming waves evolve on a flat bed to climb the final 25 m on a beach with slope with constant slope of 1:10. A small regular wave train forms the basis for investigations of force patterns on the wall. Herein, our preliminary findings reported are based on selected 6 test series (18 impacts out of 150 impacts). In general, wall pressures greater than 1 MPa and 10 m run-up are easily developed even with moderate amplitude waves at the inlet. We will discuss some details of the underlying mechanism of various types of breaking and impact on the wall. The peak pressure identified on the wall with the mixed gravel beach surface was 1.23 million N/m2 occurring in 0.2 milli seconds. It was cuased by a plunging breaker with a relatively large air pocket (∼0.11 m2). It was further identified that the maximum pressure on the wall does not necessarily give the maximum jet velocity (equivalent to vertical force considered in design of on parapets). They are independent quantities in these very random rapid processes. The maximum jet velocity was in the order of 35 m/s but could higher on a different beach surface. Further, it was found that the maximum waves are not necessarily the most critical ones as the waves break and therefore dissipates its energy before reaching the wall. A plunging breaker with a relatively large airpocket with a crest tip located at the top part of the wall resulted in max. peak wall pressure. One impact case caused a near simultaneous double peak pressure generated by a plunging breaker with two relatively small airpockets (0.003 m2 and 0.01 m2). This was the impact case responsible for the max. vertical jet velocity. We further found that the max. peak water pressure of the plunging breakers had a similar order of magnitude as the max. pressure within an air pocket.

Experimental Observations and Numerical Simulations of Wave Impact Forces on Recurved Parapets Mounted Above a Vertical Wall

2009 ◽  
Author(s):  
David Newborn ◽  
Nels Sultan ◽  
Pierre Beynet ◽  
Tim Maddux ◽  
Sungwon Shin ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Simulations ◽  
Shear Force ◽  
Experimental Testing ◽  
Vertical Wall ◽  
Experimental Tests ◽  
Vertical Force ◽  
Base Shear ◽  
Wave Impact ◽  
Overturning Moment

Large-scale hydraulic model tests and detail numerical model investigations were conducted on recurved wave deflecting structures to aid in the design of wave overtopping mitigation for vertical walls in shallow water. The incident wave and storm surge conditions were characteristic return period events for an offshore island on the North Slope of Alaska. During large storm events, despite depth-limited wave heights, a proposed vertical wall extension was susceptible to wave overtopping, which could potentially cause damage to equipment. Numeric calculations were conducted prior to the experimental tests and were used to establish the relative effectiveness of several recurved parapet concepts. The numerical simulations utilized the COrnell BReaking waves and Structures (COBRAS) fluid modeling program, which is a Volume-of-Fluid (VOF) model based on Reynolds Averaged Navier-Stokes equations [1] [2]. The experimental testing was conducted in the Large Wave Flume (LWF) at Oregon State University, O.H. Hinsdale Wave Research Laboratory. The experimental test directly measured the base shear force, vertical force, and overturning moment applied to the recurved parapets due to wave forcing. Wave impact pressure on the parapet and water particle velocities seaward of the wall were also measured. Results from the experimental testing include probability of exceedance curves for the base shear force, vertical force, and overturning moment for each storm condition. Qualitative comparisons between the experimental tests and the COBRAS simulations show that the numerical model provides realistic flow on and over the parapet.

2D Numerical Viscous Predictions of Wave Impact Effects on an Idealized Seawall Rooted in Large Scale Experiments (1:4)

2015 ◽  
Author(s):  
Olivier G. Tremblay ◽  
Jannette Frandsen
Keyword(s):  
Large Scale ◽  
Model Performance ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Cfd Model ◽  
Wave Impact ◽  
Air Pocket ◽  
Vibrational Characteristics ◽  
Storm Wave ◽  
Underlying Processes

This study aims to investigate the free-surface flow involved in a wave impact and the vibrational characteristics of an idealized seawall to achieve an improved insight in the design of seawalls and coastal infrastructures subjected to moderate and storm wave conditions. This type of structure can be subjected to frequently occurring as well as high impact wave loadings. In addition to the structural concerns, it is also important to evaluate the importance of the coupling between both fluid and structure motion. In the various steps to design proper wall deflector (wave guide) and to predict pressures and forces following a wave impact, we first present a comparison between numerical results from a CFD model and experimental recordings conducted in a large scale flume in the new Quebec Coastal Physics Laboratory, Canada. A CFD model performance is tested to investigate the more fundamental mechanisms of the underlying processes and to assess real conditions around seawalls to facilitate design process. The preliminary results are based on the assumption of treating the fluid-structure interaction physics as decoupled processes and the wall as a rigid plate. Modal analysis performed on the structure indicates that this approach is adequate, since loadings are of short duration (less than 1 ms) compared to the wall natural frequencies. A maximum local wall pressure of 3.5 MPa has been obtained from an air-pocket impact which generates an instantaneous horizontal force of 4.3×106 N/m.

scholarly journals An Analytical Approach for the Two-Dimensional Plunging Breaking Wave Impact on a Vertical Wall with Air Entrapment

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 58
Author(s):  
Theodosis D. Tsaousis ◽  
Ioannis K. Chatjigeorgiou
Keyword(s):  
Free Surface ◽  
Velocity Potential ◽  
Mixed Boundary ◽  
Dimensional Space ◽  
Vertical Wall ◽  
Breaking Wave ◽  
Linear Potential ◽  
Two Dimensional ◽  
Wave Impact ◽  
Air Pocket

This study investigates an idealized formulation of the two-dimensional impact of a breaking wave on a vertical impermeable wall. An overturning-like wave is assumed, which is close to the concept of a plunging breaker. It is assumed that during the collision an air pocket is entrapped between the wave and the wall. The air pocket width is assumed to be negligible and the compression effects are omitted. The problem is considered in the two-dimensional space (2D) using linear potential theory along with the small-time approximation. We use a perturbation method to cope with the linearized free-surface kinematic and dynamic boundary conditions. We impose the complete mixed boundary value problem (bvp) and we solve for the leading order of the velocity potential. The problem derived involves dual trigonometrical series and is treated analytically. The main assumption made is that, within the air pocket, the pressure is zero. Results are presented for the velocity potential on the wall, the velocity, and the free-surface elevation.

scholarly journals Wave Impact Loads on Vertical Seawalls: Effects of the Geometrical Properties of Recurve Retrofitting

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2849
Author(s):  
Shudi Dong ◽  
Md Salauddin ◽  
Soroush Abolfathi ◽  
Jonathan Pearson
Keyword(s):  
Impact Force ◽  
Vertical Wall ◽  
Impact Loads ◽  
Geometrical Shape ◽  
Wave Loading ◽  
Wave Impact ◽  
Static Loads ◽  
Geometrical Properties ◽  
Overhang Length ◽  
Overturning Moment

This study investigates the variation of wave impact loads with the geometrical configurations of recurve retrofits mounted on the crest of a vertical seawall. Physical model tests were undertaken in a wave flume at the University of Warwick to investigate the effects of the geometrical properties of recurve on the pressure distribution, overall force, and overturning moment at the seawall, subject to both impulsive and non-impulsive waves. Additionally, the wave impact and quasi-static loads on the recurve portion of the retrofitted seawalls are investigated to understand the role of retrofitting on the structural integrity of the vertical seawall. Detailed analysis of laboratory measurements is conducted to understand the effects of overhang length and height of the recurve wall on the wave loading. It is found that the increase in both recurve height and overhang length lead to the increase of horizontal impact force at an average ratio of 1.15 and 1.1 times larger the reference case of a plain vertical wall for the tested configurations. The results also show that the geometrical shape changes in recurve retrofits, increasing the overturning moment enacted by the wave impact force. A relatively significant increase in wave loading (both impact and quasi-static loads) are observed for the higher recurve retrofits, while changes in the overturning moment are limited for the retrofits with longer overhang length. The data generated from the physical modelling measurements presented in this study will be particularly helpful for a range of relevant stakeholders, including coastal engineers, infrastructure designers, and the local authorities in coastal regions. The results of this study can also enable scientists to design and develop robust decision support tools to evaluate the performance of vertical seawalls with recurve retrofitting.

scholarly journals Impact pressure on an orifice plate by a rising water column driven by an air pocket in a vertical riser

2020 ◽  
Vol 81 (5) ◽  
pp. 1029-1038 ◽  
Author(s):  
Yu Qian ◽  
David Z. Zhu
Keyword(s):  
Water Column ◽  
Peak Pressure ◽  
Current Model ◽  
Strong Relationship ◽  
Water Hammer ◽  
Orifice Plate ◽  
Minor Effect ◽  
Initial Water ◽  
Air Pocket ◽  
Riser Height

Abstract Occurrences of storm geyser events have attracted significant attention in recent years. Previous studies suggest that using an orifice plate can reduce the intensity of a geyser event but may induce a water-hammer type of pressure on the orifice plate. This study was conducted to explore the factors that influence the pressure transients when an orifice plate was installed in a vertical riser. A novel model was developed to simulated the movement of a rising water column driven by an air pocket in a vertical riser with an orifice plate on the top. Water-hammer type of pressure occurs when the water column reaches the orifice plate. The current model accurately simulates the dynamics of the water column considering its mass loss due to the flow along the wall of the riser (film flow) and the existence of the orifice plate. It was found that the initial water column length and the driving pressure, as well as the riser material, have a strong relationship with the peak pressure. The riser diameter and riser height have minor effect on the peak pressure. The water-hammer induced peak pressure reaches the maximum when the orifice opening is around 0.2 times the diameter of the vertical riser.

scholarly journals Development of Pant-Type Harness with Fabric Air-Pocket for Pain Relief

2019 ◽  
Vol 9 (9) ◽  
pp. 1921
Author(s):  
Dongwoo Nam ◽  
Miyeon Kwon ◽  
Juhea Kim ◽  
Bummo Ahn
Keyword(s):  
Contact Area ◽  
Peak Pressure ◽  
Applied Pressure ◽  
The Body ◽  
Area Measurement ◽  
Medical Applications ◽  
Air Pocket ◽  
Long Time ◽  
Developed Pressure ◽  
Air Pockets

Harnesses can be used in various applications, such as entertainment, rescue operations, and medical applications. Because users are supported on the harness for a long time, they should feel comfortable wearing the harnesses. However, existing commercial harnesses are uncomfortable to wear and cause continuous serious pain. Therefore, in this study, a new pant-type harness with a fabric air pocket to reduce the applied pressure on the body, especially in the groin, is proposed. Keeping this in mind, we have designed and developed the pant-type harness. In addition, we performed pressure and contact area measurement experiments using the harness developed, pressure sensor, and a human mannequin. Peak and mean pressures and contact areas near the groin and waist were measured in the experiments. From the results, when air is injected in the air pockets, the peak pressure and contact area near the waist increased, and the peak pressure near the groin decreased. This means that the pressure applied on the human mannequin near the groin reduces because of the increased contact area near the waist, which is achieved by multi-layered air pockets. In this study, we proposed the optimal design of a novel pant-type harness that can address the limitations of existing harnesses. The proposed harness can be used for a prolonged time in applications, such as virtual reality entertainment, rescue operations, and rehabilitation.

Illustration of the WPS Benefit Through Batman Test Series: Tests on Large Specimens Under WPS Loading Configurations

2008 ◽  
Author(s):  
S. Chapuliot ◽  
L. Ferry ◽  
T. Yuritzinn ◽  
D. Moinereau ◽  
A. Dahl ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Ferritic Steel ◽  
Large Scale ◽  
Tensile Load ◽  
Test Series ◽  
Global Approach ◽  
Local Approach ◽  
Steel Bars ◽  
Failure Loads ◽  
Series Of Experiments

A study combining modelling and a series of experiments on large specimens submitted to a thermal shock or isothermal cooling has been performed in CEA-Saclay in order to show the WPS benefit on large scale specimen. The test series, named BATMAN, was made on 18MND5 ferritic steel bars, containing a short or large fatigue pre-crack. For the two performed tests (fast thermal shock creating a gradient across the thickness of the bar or for the gradual uniform cooling), the effect of “Warm Pre-Stressing” was confirmed. In both cases, no propagation was observed during the thermal transient. Fracture occurred under low temperature conditions, at the end of the test when the tensile load was increased. The failure loads then recorded were substantially higher than during pre-stressing. To illustrate the benefit of the WPS effect, numerical interpretations were performed using either global approach or local approach criteria. The capability of models to predict the WPS effect was clearly shown.

scholarly journals The role of Stewartson and Ekman layers in turbulent rotating Rayleigh–Bénard convection

2011 ◽  
Vol 688 ◽  
pp. 422-442 ◽  
Author(s):  
Rudie P. J. Kunnen ◽  
Richard J. A. M. Stevens ◽  
Jim Overkamp ◽  
Chao Sun ◽  
GertJan F. van Heijst ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Wall Temperature ◽  
Large Scale ◽  
Vertical Wall ◽  
Vertical Axis ◽  
Dominant Feature ◽  
A Cell ◽  
Vertically Aligned ◽  
Boundary Layer Dynamics ◽  
Rayleigh Benard

AbstractWhen the classical Rayleigh–Bénard (RB) system is rotated about its vertical axis roughly three regimes can be identified. In regime I (weak rotation) the large-scale circulation (LSC) is the dominant feature of the flow. In regime II (moderate rotation) the LSC is replaced by vertically aligned vortices. Regime III (strong rotation) is characterized by suppression of the vertical velocity fluctuations. Using results from experiments and direct numerical simulations of RB convection for a cell with a diameter-to-height aspect ratio equal to one at $\mathit{Ra}\ensuremath{\sim} 1{0}^{8} \text{{\ndash}} 1{0}^{9} $ ($\mathit{Pr}= 4\text{{\ndash}} 6$) and $0\lesssim 1/ \mathit{Ro}\lesssim 25$ we identified the characteristics of the azimuthal temperature profiles at the sidewall in the different regimes. In regime I the azimuthal wall temperature profile shows a cosine shape and a vertical temperature gradient due to plumes that travel with the LSC close to the sidewall. In regimes II and III this cosine profile disappears, but the vertical wall temperature gradient is still observed. It turns out that the vertical wall temperature gradient in regimes II and III has a different origin than that observed in regime I. It is caused by boundary layer dynamics characteristic for rotating flows, which drives a secondary flow that transports hot fluid up the sidewall in the lower part of the container and cold fluid downwards along the sidewall in the top part.

Large Scale Experimental Storm Impact on Nourished Beach Using Cobble-Gravel-Sand Mix

2015 ◽  
Author(s):  
Jannette B. Frandsen ◽  
Régis Xhardé ◽  
Francis Bérubé ◽  
Olivier Gauvin Tremblay
Keyword(s):  
Grain Size ◽  
Large Scale ◽  
Tidal Range ◽  
Initial Slope ◽  
Coastal Protection ◽  
Quebec City ◽  
Beach Profile ◽  
Wave Impact ◽  
Sediment Grain Size ◽  
Sand Mixture

We have investigated beach stability against storm waves. The studies are done in relation to eroded beaches. We are testing a cobble-sand-gravel mixture as a means of using a soft method for coastal protection on nourished beaches. A physical model of an existing beach was built at scale 1:3. The cobble/sand grain size is in 1:3 scale while the gravel is 1:1.5 scale. The large scale experimental flume tests have been set-up in the new outdoor 120 m long flume in Québec city, Canada. The tests were conducted over two test seasons (2013–14). While we in the first test season studied impact on the beach due to incoming regular plunging breakers, the last season contained tests with incoming irregular plunging breakers on the beach with/without tidal variation. Herein, we primarily report on the wave impact due to irregular plunging breakers on constant and tidal varying water depths. The wave-tide interactions were conducted with a tidal range of 1 m in relation to beaches with steep beach slopes (1:10, 1:5, 1:1). The model inlet significant wave height was 1.1–1.5 m corresponding to equivalent prototype waves in the range of max. wave heights of 6–8.5 m with dominant periods of 12 s in water depth of about 15 m and tidal range of 3 m. In general, the Equilibrium Beach Profile (EBP) was reached after exposure to about 10,000 plunging breakers or the equivalent of five storms assuming each lasting 3 hours. A cobble berm was formed rapidly on the top of the beach, protecting the backshore against wave action and flooding while finer sediment was transported “offshore”. Beach width reduction was observed when the initial slope of the beach fill material exceeded the equilibrium beach slope. Sediment grain size sorting along the beach profile is discussed and compared to existing beach models, and EBP was compared to several EBP equations. From a coastal management perspective, in terms of durability, the mixed cobble-sand-gravel material is showing promise as a material to use for coastal protection. It is highly absorbent and the beach tends to maintain its shape over long time when exposed to several storms. However, storm surges in the combination with high tides can results in excessive run-up and potential flood risks. The stabilized beach typically had slopes of 1:7–1:9 independent of the initial slope. We found that irregular seas result in a less pronounced trough in the beach profile in the swash zone than incoming regular plunging breakers. The tidal interaction was further advantageous, naturally shifting the material back and forth. However, other materials and other sensitivity studies are necessary in order to provide firm conclusions about the usage of the cobble-gravel-sand mixture for coastal protection.

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