Green Water on a Fixed Model in a Large Wave Basin: Flow Velocity, Void Fraction, and Impact Pressure Distributions

2017 ◽  
Author(s):  
Wei-Liang Chuang ◽  
Kuang-An Chang ◽  
Richard Mercier
Keyword(s):  
Flow Velocity ◽  
Void Fraction ◽  
Vertical Wall ◽  
Pressure Sensors ◽  
Impact Pressure ◽  
Green Water ◽  
Breaking Wave ◽  
Large Wave ◽  
Wave Basin ◽  
The Impact

Green water impact due to extreme waves impinging on a fixed, rectangular shaped model structure was investigated experimentally. The experiment was carried out in the large wave basin of the Offshore Technology Research Center at Texas A&M University. In the study, two wave conditions were considered: a plunging breaking wave impinging on the frontal vertical wall (referred as wall impingement) and a breaking wave directly impinging on the deck surface (referred as deck impingement). The aerated flow velocity was measured by employing the bubble image velocimetry (BIV) technique with high speed cameras. The pressure distribution on the deck surface was measured by four differential pressure sensors. The fiber optic reflectometer (FOR) technique was employed to measure the void fraction in front of each pressure sensor end face. The flow velocity, void fraction, and impact pressure, were synchronized and simultaneously measured. Comparisons between an earlier study by Ryu et al. (2007) and the present study were performed to examine the scale effect. Results between Song et al. (2015) and the present results were also compared to investigate the influence of structure geometry on green water flow and impact pressure. To examine the role of air bubbles during the impact, the velocity, pressure, and void fraction were correlated. Correlation between the peak pressure and the aeration level shows a negative trend before the wave impingement but a positive linear relationship after the impingement.

Impact Pressure, Void Fraction, and Green Water Velocity due to Plunging Breaking Wave Impingement on a 2D Tension-Leg Structure

2016 ◽  
Author(s):  
Wei-Liang Chuang ◽  
Kuang-An Chang ◽  
Richard Mercier
Keyword(s):  
Void Fraction ◽  
Bubbly Flow ◽  
Vertical Wall ◽  
Pressure Sensors ◽  
Density Variation ◽  
Impact Pressure ◽  
Green Water ◽  
Breaking Wave ◽  
Peak Pressures ◽  
The Impact

Violent impacts due to plunging waves impinging on a 2D tension-leg model structure were experimentally investigated in a laboratory. In the experiment, velocities, pressures, and void fraction were simultaneously measured and the relationship among them was examined. The nonintrusive bubble image velocimetry technique was employed to quantify the instantaneous bubbly flow velocities and structure motion. Pressures on the structure vertical wall above the still water level were measured by four differential pressure sensors. Additionally, four fiber optic reflectometer probes were used to measure the void fraction coincidently with the pressure sensors. With repeated simultaneous, coincident velocity, pressure and void fraction measurements, temporal evolution of the ensemble-averaged velocities, pressures, and void fraction were demonstrated and correlated. Relationship between the peak pressures and their rise time was examined and summarized in dimensionless form. Impact coefficients that relate the impact pressure with flow kinetic energy were obtained from the ensemble-averaged measurements. Finally, the impact coefficients with and without the consideration of the fluid density variation due to bubbles were examined and compared.

Relation Between Flow Velocity and Impact Pressure in a Green Water Flow

2013 ◽  
Author(s):  
Kusalika Ariyarathne ◽  
Kuang-An Chang ◽  
Richard Mercier
Keyword(s):  
Kinetic Energy ◽  
Void Fraction ◽  
Pressure Rise ◽  
Impact Pressure ◽  
Breaking Wave ◽  
Wave Condition ◽  
Wall Impingement ◽  
Impact Coefficient ◽  
The Impact ◽  
Mean Kinetic Energy

Impact pressure due to plunging breaking waves impinging on a simplified model structure was investigated in the laboratory based on two breaking wave conditions: the wall impingement wave condition and the deck impingement wave condition. Pressure, void fraction, and velocities were measured at various locations on the deck surface. Impact pressure was correlated with the mean kinetic energy calculated based on the measured mean velocities and void fraction to obtain the impact coefficient. For the wall impingement wave condition, the relationship between impact pressure and mean kinetic energy is linear with the impact coefficient close to unity. For the deck impingement wave condition, the above relationship does not show good correlation, whereas the impact coefficient was found to be a function of the rate of pressure rise.

Surface velocity and impact pressure of green water flow on a fixed model structure in a large wave basin

2015 ◽  
Vol 104 ◽  
pp. 40-51 ◽  
Author(s):  
Youn Kyung Song ◽  
Kuang-An Chang ◽  
Kusalika Ariyarathne ◽  
Richard Mercier
Keyword(s):  
Water Flow ◽  
Impact Pressure ◽  
Green Water ◽  
Surface Velocity ◽  
Model Structure ◽  
Large Wave ◽  
Wave Basin ◽  
Fixed Model

Velocity, Pressure, and Dam-Break Similarity of Green Water Flow on a 3D Structure

2011 ◽  
Author(s):  
Kuang-An Chang ◽  
Kusalika Ariyarathne ◽  
Richard Mercier
Keyword(s):  
Vertical Wall ◽  
Three Dimensional ◽  
Dam Break ◽  
Green Water ◽  
Breaking Wave ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Wave Condition ◽  
Wall Impingement ◽  
The Impact

Flow dynamics of green water due to plunging breaking waves interacting with a simplified, three-dimensional model structure was investigated in laboratory. Two breaking wave conditions were tested: one with waves impinging and breaking on the vertical wall of the model at the still water level (referred as wall impingement) and the other with waves impinging and breaking on the horizontal deck surface (referred as deck impingement). The bubble image velocimetry (BIV) technique was used to measure the flow velocity. Measurements were taken on a vertical plane located at the center of the deck surface and a horizontal plane located slightly above the deck surface. The applicability of dam-break theory on green water velocity prediction for the three-dimensional model was also investigated. Furthermore, pressure measurements were performed at several locations above the horizontal deck surface for the wall impingement wave condition. Predictions of maximum impact pressure based on the measured pressure and flow velocities were investigated using the impact coefficient approach that links pressure with kinetic energy.

Green Water Flow on a Fixed Model Structure in a Large Wave Basin Under Random Waves

2018 ◽  
Author(s):  
Wei-Liang Chuang ◽  
Kuang-An Chang ◽  
Richard Mercier
Keyword(s):  
Velocity Distribution ◽  
Flow Behavior ◽  
Green Water ◽  
Wave Crest ◽  
Breaking Wave ◽  
Model Structure ◽  
Random Waves ◽  
Large Wave ◽  
Geometry Model ◽  
Wave Basin

Green water generated by random waves on a fixed, simplified geometry model structure was measured in a large wave basin. The velocity field of the flow that is aerated and highly turbulent was quantified using the bubble image velocimetry (BIV) technique. BIV utilizes shadow textures created by air-water interfaces as tracers in backlit images recorded by a high speed camera. The tracers in consecutive images are then cross-correlated to obtain the corresponding two-dimensional velocities. Random waves were generated by the JONSWAP spectrum with a significant wave height close to the freeboard. An image-based triggering method was employed to detect the green water events and trigger image acquisition. A total of 179 green water events were collected and categorized into three different types, based on the flow behavior. That includes the collapse of overtopping wave, fall of bulk water, and breaking wave crest. Statistical distributions of maximum green water velocities under random waves were developed, while the lognormal distribution was found as the best fit. By modeling the green water as a dam break flow, the Ritter solution was found to be able to capture the horizontal velocity distribution for the random green water events. A prediction equation for the green water velocity distribution under random waves was also obtained.

Spectral Analysis of Irregular Wave Impact on the Structure in Splash Zone

2002 ◽  
Author(s):  
Bing Ren ◽  
Yongxue Wang
Keyword(s):  
Spectral Analysis ◽  
Wave Height ◽  
Incident Wave ◽  
Impact Pressure ◽  
Splash Zone ◽  
Spectral Moment ◽  
Wave Impact ◽  
Large Wave ◽  
Irregular Wave ◽  
The Impact

The spectral analysis from experimental data of irregular wave impact on the structures with large dimension in the splash zone is presented. The experiments were conducted in the large wave-current tank in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. In the experiment, the target spectrum is JONSWAP spectrum, the significant wave height H1/3 is in the range from 0.1m to 0.3m, and the peak period of spectrum Tp in the range from 1.0s to 2.0s. The ratio of s/H1/3, which refers to the clearance of the subface of the structure above still water level (s) to the incident wave height, is between −0.1 and 0.4. The spectral analysis results of the irregular wave impact pressure on the subface of the structure under various case studies are presented. The distribution of spectral moment of the impact pressure on the structure along the subface is given. And the influence of different incident wave parameters and relative clearance s/H1/3 on the average spectral moment of impact pressure are discussed.

scholarly journals VERTICAL SEA WALL CREST MODIFICATIONS FOR OVERTOPPING

2018 ◽  
pp. 71
Author(s):  
Dogan Kisacik ◽  
Gulizar Ozyurt Tarakcioglu ◽  
Cuneyt Baykal ◽  
Gokhan Kaboglu
Keyword(s):  
Urban Areas ◽  
Vertical Wall ◽  
Breaking Wave ◽  
Limited Information ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Wave Basin ◽  
First Results ◽  
Set Up ◽  
Sea Wall

Crest modifications such as a storm wall, parapet or a bullnose are widely used to reduce the wave overtopping over coastal structures where spatial and visual demands restrict the crest heights, especially in urban areas. Although reduction factors of these modifications have been studied for sloped structures in EurOtop Manual (2016), there is limited information regarding the vertical structures. This paper presents the experimental set-up and first results of wave overtopping tests for a vertical wall with several different super structure types: a) seaward storm wall, b) sloping promenade, c) landward storm wall, d) stilling wave basin (SWB), e) seaward storm wall with parapet, f) landward storm wall on the horizontal promenade with parapet, g) landward storm wall with parapet, h) stilling wave basin (SWB) with parapet, under breaking wave conditions. The SWB is made up of a seaward storm wall (may be a double shifted rows) , a sloping promenade (basin) and a landward storm wall. The seaward storm wall is partially permeable to allow the evacuation of the water in the basin.

Effects of Obstacle’s Curvature on Shock Waves in Gravity-Driven Experimental Flows Impacting a Circular Cylinder or a Wall

2020 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Dieter Rickenmann
Keyword(s):  
Shock Wave ◽  
Circular Cylinder ◽  
Pressure Sensors ◽  
Granular Flows ◽  
Impact Pressure ◽  
Small Scale ◽  
Cylinder Surface ◽  
Seismic Signals ◽  
Dynamic Impact ◽  
The Impact

<p>Geophysical granular flows such as rock and snow avalanches, flow-like landslides, debris flows, and pyroclastic flows are driven by gravity and often impact on engineering structures located in gullies and slopes as they flow down, generating dynamic impact pressures and causing a major threat to infrastructures. It is necessary to understand the physical mechanism of such granular flows impacting obstacles to improve the design of protective structures and the hazard assessment related to such structures. In this study, the small-scale laboratory experiments were performed to investigate the dynamic impact caused by granular flow around a circular cylinder with variable radius of curvatures and the dynamic impact against a flat wall. Pressure sensors were used to measure the impact pressure of granular flows at both the upstream cylinder surface and at the bottom of the channel. Accelerometers were mounted on the underside of channel to record the seismic signals generated by the granular flows before and during the impact with the obstacle. Flow velocities and flow depths were determined by using high-precision cameras. The results show that a bow shock wave is generated upstream of the cylinder, causing dynamic pressures on both the obstacle and the bottom of the channel. The dimensionless standoff distance of the granular shock wave decreases nonlinearly or almost exponentially with increasing Froude number (Fr) in the range of 5.5 to 11.0. The dimensionless pinch-off distance and dimensionless run-up height grow linearly with increasing Fr, and they were significantly influenced by the radius of curvature of the structure at the stagnation point (RCSSP). The dimensionless impact pressure on the structure surface is sensitive to the RCSSP, while the differences decrease as Fr increases; Seismic signals generated at the underside of the channel and at the top of the cylinder were also recorded to assist in analyzing the effects of RCSSP.</p>

Spatial and temporal variability of snow avalanche impact pressure and its importance for structural design

2020 ◽  
Author(s):  
Betty Sovilla ◽  
Michael Kyburz ◽  
Camille Ligneau ◽  
Jan-Thomas Fischer ◽  
Mark Schaer
Keyword(s):  
Structural Design ◽  
Temporal Variability ◽  
Pressure Sensors ◽  
Flow Regimes ◽  
Test Site ◽  
Impact Pressure ◽  
Snow Avalanche ◽  
Small Cells ◽  
Hazard Mapping ◽  
The Impact

<p>Measurements of snow avalanche impact pressures are performed at the Vallée de la Sionne test site since winter 1999. In these years of operation, we recorded the impact pressure of around 60 avalanches characterized by different flow regimes and dimensions.</p><p>Pressure measurements were performed, simultaneously, on three different structures which are spatially distributed with a maximum distance of 30 m, in the run-out zone of the Vallée de la Sionne test site. The structure widths range from 0.25 to 1 m. On these structures pressure sensors ranging from small cells with 0.10 to 0.25 m in diameter to large pressure plates with area of 1m<sup>2 </sup>are mounted at different heights.</p><p>A systematic analysis of all 60 avalanche data sets shows that the pressure measured at the different obstacles varies considerably, even within the same avalanche, both in space and time. Part of these differences can be attributed to different drag coefficients and dependence on obstacle size, but a large part of these differences can only be explained by the spatial variability of the flow properties and the temporal variability of the physical processes governing the interaction of the avalanche and the structures.</p><p>In this contribution we show how spatial and temporal impact pressure variabilities correlate to avalanche dimension and flow regimes and we discuss the implication of such variations for structural design and hazard mapping.</p>

Sign in / Sign up

Export Citation Format

Share Document