scholarly journals MOVABLE-BED MODEL STUDIES OF PERCHED BEACH CONCEPT

1972 ◽  
Vol 1 (13) ◽  
pp. 60
Author(s):  
C.B. Chatham
Keyword(s):  
Three Dimensional ◽  
Normal Wave ◽  
Beach Erosion ◽  
Model Studies ◽  
Model Study ◽  
Wide Range ◽  
Final Design ◽  
Storm Wave ◽  
Wave Conditions ◽  
Movable Bed

Hydraulic model studies were conducted to aid in ascertaining the technical feasibility and optimum design factors of the perched beach concept. Among these were two-dimensional, movable-bed studies to determine an estimate of the amount of sand which would be lost seaward over the submerged toe structure by normal and storm wave action, the optimum elevation of the submerged toe structure, and the length of a stone blanket required to reduce seaward migration of sand to a minimum. The model beach was subjected to test waves until equilibrium was reached for a wide range of wave conditions for both the existing beach and the perched beach. Test results indicate that (a) little or no beachfill material will be lost seaward of the toe structure for normal wave conditions but the larger storm waves may cause erosion of the perched beach, (b) the installation of a stone blanket shoreward of the toe structure will reduce the amount of beach erosion, (c) if the beach fill is extended a sufficient distance seaward, the toe structure serves no useful purpose, and (d) a three-dimensional movable-bed model study is feasible and is necessary to determine the final design features of a perched beach.

scholarly journals APPLICABILITY OF SUB-SAND SYSTEM TO BEACH EROSION CONTROL

1986 ◽  
Vol 1 (20) ◽  
pp. 92 ◽  
Author(s):  
Yoshiaki Kawata ◽  
Yoshito Tsuchiya
Keyword(s):  
Normal Wave ◽  
Erosion Control ◽  
Beach Erosion ◽  
Beach Profile ◽  
Sand Filter ◽  
Beach Sediment ◽  
Filter System ◽  
Fluid Boundary ◽  
Wave Conditions ◽  
Control Work

We performed experiments in the laboratory under controlled conditions in order to determine the applicability of a sub-sand filter system to the beach erosion control work. The filter system is used to control a flow condition at the sediment-fluid boundary. In the foreshore, it increases the inflowing velocity into the beach and thus results in increasing the threshold of beach sediment movement. The sub-sand filter system accelerates accretion of much beach sediment in the foreshore through the development of a berm under normal wave conditions. When wave conditions change from normal to stormy , it is also applicable to stabilize the beach profile, and thus decrease loss of beach sediment from the foreshore to the offshore.

scholarly journals NUMERICAL STUDY OF NEARSHORE HYDRODYNAMICS UNDER STORM WAVE CONDITIONS IN HUJEONG BEACH, EAST COAST OF KOREA

2018 ◽  
pp. 67
Author(s):  
Yeon S. Chang ◽  
Jong Dae Do ◽  
Kyungmo Ahn ◽  
Jae-Youll Jin
Keyword(s):  
Numerical Model ◽  
East Coast ◽  
Surf Zone ◽  
Numerical Study ◽  
Navier Stokes ◽  
Model Study ◽  
Suspended Sediment Concentrations ◽  
Storm Wave ◽  
Wave Conditions ◽  
The Republic

In this study, we present the results of numerical model study to simulate the hydrodynamic conditions observed in Hujeong Beach in the east coast of the Republic of Kore from December, 2016 to January, 2017 during which several extratropical cyclones hit the area causing extreme wave conditions. Three acoustic instrumentation systems were moored from the coast to a location outside the surf zone where the water depth was ~8m to measure waves, currents and suspended sediment concentrations. For the numerical model, we employed the CADMAS-SURF Raynolds-Averaged Navier-Stokes (RANS) model to generate the wave conditions over the region of the field experiment.

scholarly journals A Simple Nozzle-Diffuser Duct Used as a Kuroshio Energy Harvester

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1552
Author(s):  
Po-Hung Yeh ◽  
Shang-Yu Tsai ◽  
Wei-Ren Chen ◽  
Shing-Nan Wu ◽  
Meng-Chang Hsieh ◽  
...  
Keyword(s):  
Energy Demand ◽  
Energy Harvester ◽  
Normal Wave ◽  
Sea Surface ◽  
Ocean Current ◽  
Ansys Fluent ◽  
Wave Condition ◽  
Storm Wave ◽  
Wave Conditions ◽  
The Kuroshio

In response to the increasing energy demand in Taiwan and the global trend of renewable energy development, Kuroshio energy is a potential energy source. How to extract this invaluable natural resource has then become an intriguing and important question in engineering practices. This study reported the results of a feasibility study for a nozzle-diffuser duct (NDD) as the Kuroshio currents energy harvester. The computational fluid dynamics (CFD) software ANSYS Fluent was employed to calculate the drag and added mass coefficients of the duct anchored to the seabed. Those coefficients were further imported into Orcaflex to simulate the motion of the duct under normal and storm wave conditions. Results showed that the duct was stable 25 m below the sea surface under normal wave conditions. When the wave condition changed to storm waves, the duct needed to dive into at least 90 m below the sea surface to regain its stability and obtain high power take-off (PTO). An optimal design nozzle-diffuser-duct was reported, and a PTO peak of 15 kW was expectable in the Kuroshio currents. Once a suitable offshore platform can be developed with sixty-six NDDs, a Megawatt Kuroshio ocean current power generation system is feasible in the near future.

The Role of CFD in Turbomachinery Design

2001 ◽  
Author(s):  
Hsin-Hua Tsuei
Keyword(s):  
Critical Role ◽  
Three Dimensional ◽  
Design Procedure ◽  
Iteration Process ◽  
Navier Stokes ◽  
Convergence Error ◽  
Design Iteration ◽  
Wide Range ◽  
Final Design ◽  
Turbomachinery Design

Abstract The use of three-dimensional, Navier-Stokes CFD as a practical tool for turbomachinery design is discussed. For a CFD based design procedure to be practical and efficient, the design engineer is required to make a number of important decisions e.g. the minimum level of physics that is required to be simulated which will impact the design outcome, the appropriate level of grid resolution that will be necessary to model this physics. With judicious decisions for these issues, we illustrate that CFD can be integrated effectively into a design iteration process for problems ranging from single blade row design to multiple stage analysis. A wide range of test cases are presented using the pbCFD code which is built upon Dawes’ BTOB3D code. The examples presented here include a range of centrifugal and axial turbomachines. In most cases, solutions are obtained in the order of 10 minutes on a 1GHz Pentium processor with mass convergence error being within 1 percent. Good comparison is shown with data for the final design illustrating the critical role that CFD can play in the design process.

Model Study of Waves Generated by Convection with Direct Validation via Satellite

2010 ◽  
Vol 67 (5) ◽  
pp. 1617-1631 ◽  
Author(s):  
Alison W. Grimsdell ◽  
M. Joan Alexander ◽  
Peter T. May ◽  
Lars Hoffmann
Keyword(s):  
Gravity Waves ◽  
Three Dimensional ◽  
Early Morning ◽  
Wave Pattern ◽  
Global Scale ◽  
Major Effect ◽  
Small Scale ◽  
Model Studies ◽  
Model Study ◽  
Cloud Resolving Model

Abstract Atmospheric gravity waves have a major effect on atmospheric circulation, structure, and stability on a global scale. Gravity waves can be generated by convection, but in many cases it is difficult to link convection directly to a specific wave event. In this research, the authors examine an event on 12 January 2003 when convective waves were clearly generated by a period of extremely intense rainfall in the region of Darwin, Australia, during the early morning. The waves were observed by the Atmospheric Infrared Sounder (AIRS) instrument on board the Aqua satellite, and a dry version of a nonlinear, three-dimensional mesoscale cloud-resolving model is used to generate a comparable wave field. The model is forced by a spatially and temporally varying heating field obtained from a scanning radar located north of Darwin at Gunn Point. With typical cloud-resolving model studies it is generally not possible to compare the model results feature-for-feature with observations since although the model precipitation and small-scale heating may be similar to observations, they will occur at different locations and times. In this case the comparison is possible since the model is forced by the observed heating pattern. It is shown that the model output wave pattern corresponds well to the wave pattern observed by the AIRS instrument at the time of the AIRS overpass.

scholarly journals Evaluating the Structure from Motion Technique for Measurement of Bed Morphology in Physical Model Studies

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 998
Author(s):  
Sanat Kumar Karmacharya ◽  
Nils Ruther ◽  
Ujjwal Shrestha ◽  
Meg Bahadur Bishwakarma
Keyword(s):  
Physical Model ◽  
Structure From Motion ◽  
Point Cloud ◽  
Three Dimensional ◽  
Time Frame ◽  
Model Studies ◽  
Model Study ◽  
Skilled Personnel ◽  
Dense Point ◽  
Point Data

The selection of instrumentation for data acquisition in physical model studies depends on type and resolution of data to be recorded, time frame of the model study, available instrumentation alternatives, availability of skilled personnel and overall budget of the model study. The available instrumentation for recording bed levels or three-dimensional information on geometry of a physical model range from simple manual gauges to sophisticated laser or acoustic sensors. In this study, Structure from Motion (SfM) technique was applied, on three physical model studies of different scales and study objectives, as a cheap, quicker, easy to use and satisfactorily precise alternative for recording 3D point data in form of colour coded dense point cloud representing the model geometry especially the river bed levels in the model. The accuracy of 3D point cloud generated with SfM technique were also assessed by comparing with data obtained from manual measurement using conventional surveying technique in the models and the results were found to be very promising.

scholarly journals RECREATIONAL SURFING ON HAWAIIAN REEFS

1972 ◽  
Vol 1 (13) ◽  
pp. 147 ◽  
Author(s):  
James R. Walker ◽  
Robert Q. Palmer ◽  
Joseph K. Kukea
Keyword(s):  
Coastal Zone ◽  
Three Dimensional ◽  
Hydraulic Model ◽  
Small Scale ◽  
Ocean Bottom ◽  
Model Studies ◽  
Model Study

Recreational surfing has been studied in Hawaii to develop criteria for the preservation, enhancement and design of surf sites. The criteria will aid in planning compatible uses of the coastal zone. Surfing characteristics and wave transformations were studied in the field and related to ocean bottom features at prime surf sites. A small scale, three dimensional, hydraulic model study was conducted to determine the effect that a given bottom feature had upon the surfing wave. A concept of a multiple-purpose surfing shoal to be compatible with several varied interests in the coastal zone was hypothesized from field, analytic, and model studies.

scholarly journals Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 458
Author(s):  
Drew C. Baird ◽  
Benjamin Abban ◽  
S. Michael Scurlock ◽  
Steven B. Abt ◽  
Christopher I. Thornton
Keyword(s):  
Numerical Modeling ◽  
Physical Model ◽  
Numerical Models ◽  
Hydraulic Performance ◽  
Physical Models ◽  
Protection Measures ◽  
Design Engineers ◽  
Model Study ◽  
Study Results ◽  
Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

scholarly journals Upper Jurassic Bedded Limestones and Early Diagenetic Dolomitized Limestones in the Light of Mineralogical, Geochemical and Sedimentological Studies; Kraków Area, Poland

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 462
Author(s):  
Marcin Krajewski ◽  
Piotr Olchowy
Keyword(s):  
Clay Minerals ◽  
Normal Wave ◽  
Upper Jurassic ◽  
Reef Facies ◽  
Sedimentary Environments ◽  
Storm Wave ◽  
Microscopic Studies ◽  
Silica Alumina ◽  
Characteristic Features ◽  
Facies Types

This paper describes and analyzes the Upper Jurassic (Lower Kimmeridgian) succession exposed in the Zakrzówek Horst, located in the Kraków area. Three distinguished facies types FT 1-FT 3 comprise several limestone varieties: sponge-microbial, pelitic-bioclastic, and partly dolomitized detrital-bioclastic. Their sedimentary environments varied from relatively deeper, attaining storm-wave base, to more shallower, probably close to normal-wave base. Characteristic features of limestones are changes in contents of CaCO3 and insoluble residuum as well as porosity values in vertical transitional zones between facies types. The investigated facies types differ in sediment porosity dependent on development of limestones and its susceptibility to mechanical compaction during the early diagenesis. The studied limestones show high CaCO3 contents and minor insoluble residuum contents comprising quartz, chalcedony and clay minerals. No distinct variability occurs in contents of magnesium, silica, alumina and iron accumulated in clay minerals, iron oxides and oxyhydroxides, as well as in the amounts of amorphous silica. Early diagenetic dolomites, which occur locally within the limestones, were unrelated to fracture systems as possible pathways responsible for transfer of solutions rich in Mg2+ ions. The possible source of Mg2+ ions might have been the pore solutions, which migrated from compacted basinal bedded facies towards reef facies or the grain-supported bedded facies developed in the adjacent areas. Microscopic studies revealed dedolomitization at the surfaces and in the inner parts of dolomite crystals. In many cases, dolomite crystals were replaced by calcite forming pseudomorphs.

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