Rozprawy doktorskie na temat „Sloping beach”

The prediction of coastal groundwater movement is necessary in coastal management. However, the study in this field is still a great challenge due to the involvement of tidal-groundwater interactions and the phenomena of hydrodynamic dispersion between salt-fresh water in the coastal region. To date, numerous theories for groundwater dynamic have been made available in analytical, numerical and also experimental forms. Nevertheless, most of them are based on the zeroth-order shallow flow, i.e. Boussinesq approximation. Two main components for coastal unconfined aquifer have been completed in this Thesis: the vertical beach model and the sloping beach model. Both solutions are solved in closed-form up to higher order with shallow water parameter ([epsilon]) and tidal amplitude parameter ([alpha]). The vertical beach solution contributes to the higher-order tidal fluctuations while the sloping beach model overcomes the shortcomings in the existing solutions. From this study, higher-order components are found to be significant especially for larger value of [alpha] and [epsilon]. Other parameters such as hydraulic conductivity (K) and the thickness of aquifer (D) also affect the water table fluctuations. The new sloping solution demonstrated the significant influence of beach slope ([beta]) on the water table fluctuations. A comprehensive comparison between previous solution and the present sloping solution have been performed mathematically and numerically and the present solution has been demonstrated to provide a better prediction

The diploma thesis solves the new building of the medical facility. The building will serve as a home for people with Alzheimer's disease and other types of dementia. The facility will be equipped and equipped to provide modern nursing care that focuses on Alzheimer's clients in all stages of the disease and other types of dementia. If necessary, a nursing doctor with a nurse will be present in the facility. The nursing doctor has a separate medical office in 1st floor. In addition, a phototherapeutic beach in the 1st floor, which has a favorable influence on human psyche and helps in the treatment of Alzheimer's disease, will also serve to the clients. Furthermore, it will be possible for the clients of this facility to use the accompanying services of commuter hairdressers and pedicurists / manicurists who will use the multipurpose room (canteen) in their 2nd floor for their work. The kitchen has been designed to prepare and dispatch imported food.

Cette thèse vise à étudier expérimentalement, analytiquement et numériquement, les conséquences de variations et d'oscillations hydrodynamiques à forte variabilité temporelle en milieux poreux partiellement saturés. Les problèmes que nous étudions comportent des surfaces libres tant à l'extérieur qu'à l'intérieur des milieux poreux, celles-ci étant définies comme des isosurfaces de pression d'eau égale à la pression atmosphérique (Pwater = Patm). Les différentes études expérimentales réalisées en laboratoire sont, respectivement : une expérience d'imbibition dans une boite à sable avec effets capillaires importants; la transmission d'oscillations de la surface libre à travers un massif sableux intercalaire dans un petit canal à houle (IMFT, Toulouse); l'étude de la dynamique et de la propagation des oscillations des niveaux d'eau dans un grand canal à houle (HYDRALAB, Barcelone), partiellement recouvert d'un fond sableux incliné, avec mesures de niveaux d'eau en pleine eau et sous le sable, et mesures du fond sableux (érosion/dépôts). Pour les études théoriques, nous avons développés des solutions analytiques linéarisées. Un exemple de problème traité analytiquement est: l'équation linéarisée de Dupuit-Boussinesq (D-B) transitoire à surface libre, en hypothèse d'écoulements plans et vidange/remplissage instantané : oscillations forcées, transmission et dissipation d'ondes à travers une boite à sable rectangulaire. Nous avons aussi développé une solution de l'équation faiblement non linéaire de Dupuit- Boussinesq (D-B) pour étudier le problème d'imbibition avec variation abrupte du niveau d'eau amont (suivi temporel du front de saturation). Nous avons pu étudier les différents types de problèmes transitoires liés aux expériences citées plus haut par simulation numérique. En particulier, nous avons simulé des écoulements partiellement saturés et insaturés, en coupe verticale, à l'aide d'un code de calcul (BIGFLOW 3D) qui résoud l'équation de Richards généralisée en régime transitoire. Nous avons ainsi étudié numériquement en régime non saturé, l'expérience d'imbibition dans un sable initialement sec à frontières verticales (IMFT sandbox), puis l'expérience de propagation d'ondes dans le grand canal à houle de Barcelone (laboratoire HYDRALAB) comportant une plage de sable inclinée, avec un couplage complètement intégré entre les zones micro-poreuse (sable) et “macro-poreuse” (pleine eau). Pour analyser les résultats de cette dernière expérience et les comparer aux simulations, nous avons utilisé plusieurs méthodes de traitement et d'analyse des signaux : analyse de Fourier (spectres de fréquences) ; ondelettes discrètes multi-résolution (Daubechies) ; analyses corrélatoires simple et croisée. Ces méthodes sont combinées avec des méthodes de préfiltrage pour estimer dérives et résidus (moyennes mobiles ; ondelettes multi-résolution). Cette analyse des signaux a permis de comprendre et quantifier la propagation à travers une plage de sable. Au total, les différentes approches de modélisation mis en oeuvre, associé à des procédures de calage en situation de couplage transitoire non linéaire ont permis de reproduire globalement les phénomènes de propagation de teneur en eau et de niveau d'eau dans les différentes configurations étudiées
This thesis aims at investigating experimentally, analytically and numerically, the consequences of hydrodynamic variations and oscillations with high temporal variability in partially saturated porous media. The problems investigated in this work involve “free surfaces” both outside and inside the porous media, the free surface being defined as the “atmospheric” water pressure isosurface (Pwater = Patm). The laboratory experiments studied in this work are, respectively: Lateral imbibition in a dry sand box with significant capillary effects; Transmission of oscillations of the free surface through a vertical sand box placed in a small wave canal (IMFT, Toulouse); Dynamics of free surface oscillations and wave propagation in a large wave canal (HYDRALAB, Barcelona), partially covered with sand, with measurements of both open water and groundwater levels, and of sand topography (erosion / deposition). For theoretical studies, we have developed linearized analytical solutions. Here is a sample problem that was treated analytically in this work: The linearized equation of Dupuit-Boussinesq (DB) for transient free surface flow, assuming horizontal flow and instantaneous wetting/drainage of the unsaturated zone: forced oscillations, wave transmission and dissipation through a rectangular sandbox. We also developed a weakly nonlinear solution of the Dupuit-Boussinesq equation to study the sudden imbibition (temporal monitoring of the wetting front). We have studied the different types of transient flow problems related to the experiments cited above by numerical simulation. In particular, we have simulated unsaturated or partially saturated transient flows in vertical cross-section, using a computer code (BIGFLOW 3D) which solves a generalized version of Richards’ equation. Thus, using the Richards / BIGFLOW 3D model, we have studied numerically the experiment of unsaturated imbibition in a dry sand (IMFT sandbox), and then, with the same model, we have also studied the partially saturated wave propagation experiment in the large Barcelona wave canal (HYDRALAB laboratory), focusing on the sloping sandy beach, with coupling between the micro-porous zone (sand) and the “macro-porous” zone (open water). To interpret the results of the latter experiment and compare them to simulations, we use several methods of signal analyzis and signal processing, such as: Fourier analysis, discrete multi-resolution wavelets (Daubechies), auto and cross-correlation functions. These methods are combined with pre-filtering methods to estimate trends and residuals (moving averages; discrete wavelet analyses). This signal analyzis has allowed us to interpret and quantify water propagation phenomena through a sandy beach. To sum up, different modeling approaches, combined with model calibration procedures, were applied to transient nonlinear coupled flow problems. These approaches have allowed us to reproduce globally the water content distributions and water level propagation in the different configurations studied in this work

碩士
國立中山大學
海洋環境及工程學系
87
By linearizing the problem of the surface-waves propagating on a gentle sloping beach in two dimension, this paper has developed by a suitable perturbation expansion in the bottom slope to any order and the analytical solution has been derived to third order . Furthermore, the Eulerian form is transformed to the Lagrangian form by making use of a transform function to describe the solution. The Lagrangian form can be computerized by the numerical quadrate procedure with a personal computer program of continence. This program can easily calculate the result for the diverse surface-waves propagating on the any gentle sloping beach. When the momentary serial data of the undulate waves was calculated, it could combine into the dynamic three-dimension graph of full-time evolution by the skills of the multimedia. Finally, performs a practical experiment to inspect the theoretical and numerical result and researches the agreements between the reality and the solution. Comparing the experimental data with the solutions for the different wave steepness of the deep water on the three kinds sloping beach (1/5,1/10,1/20), the wave height proportion value is between 0.892 to 1.177,the wavelength proportion value between 0.953 to 1.163 and the wave steepness proportion value between 0.901 to 1.087. Over 95% the experiment data and solutions, the errors between them are less than 10%. Hereinbefore, These evidences can prove out the theoretical solution and numerical result, which can suffice the reality.

碩士
淡江大學
水資源及環境工程所
82
The study is done with a rectangular section of water tank with the sizes of length、width and height is 30 m、0.8 m and 0.8 m, respectively.We make waves with a piston-type wave maker.Then we use different kinds of slopes、wave heights and wave periods pass through the channel with a sandy bed. During the waves pass by,it will change the bed of the channel.We consider situations among the different wave conditions and slopes to investigate the sedimentation on this sloping sandy beach. Finally,we also discuss the effects of smooth fixed-shape bed and rough fixed-shape bed on the wave run-up.We also compared and discussed the equations,which were taken by some researcher with the results of this study.

碩士
淡江大學
水資源及環境工程所
83
This study is to develope a numerical simulation of the profile changes on sloping sandy beach due to on-offshore sediment transport under continuous wave actions. This research has discussed the topographic variation of beach, changes of sediment volume, and sediment transport rate with respect to the effects of wave characteristics and the beach slope. Wave run-up on sloping beach is simulated by the finite-amplitude shallow-water wave thoery. When the run-up reaches the maximum level, the back-wash is then simulated by the free-falling motion afterward. The concept of mass conservation is also considered. We have considered two forms of seaward boundary conditions, bore form and the small amplitude wave form. The sediment transport quantities are calculated by the Bagnold''s formula, and the local slope changes due to the sediment movement have been taken into consideration. The null point is assumed to be at the grid point next to the seaward boundary seawards. To simulate the continuous incident waves, the superposition method is adopted. Owing to the profile changes, this study considers three flow situations which are hydraulic jump, flow through humpy bed, and no flow condition. The results of back-wash simulated by the free-falling motion are fine. The outcomes of using the small amplitude wave form at the seaward boundary have better agreement compared with the experimental results. The effect of the original beach slope is another important factor to the beach profile changes.

博士
國立成功大學
水利及海洋工程學系碩博士班
97
In this paper, the hydrodynamics and turbulence for wave propagating over coarse grained sloping beach is investigated using both experimental and numerical model. The coarse grained sloping beach was placed over a 1:5 inclined bottom with two layers of spherical balls. Measurements on temporal and spatial variations of physical quantities such as wave profiles, current fields and turbulence were conducted in the wave flume. The particle image velocimetry (PIV) and digital image process (DIP) techniques are employed to detect the flow field and free surface configuration at both inside and outside regions on the sloping bed. Eleven fields of views (FOVs) were integrated to explore the entire evolutions for waves propagating from the surf zone to the swash zone. In addition, a high resolution Charge Coupled Device (CCD) Camera was used to grasp the images of wave profile. Subsequent digital image processing (DIP) techniques consisting of the image enhancement, coordinate transformation, edge detection and sub-pixel concept for higher resolution were developed to resolve the image and achieve a complete water surface evolutions. In the experimental study, the PIV and DIP techniques provide a possibility for measuring a full scale temporal and spatial variation of the wave profiles and velocity field. Furthermore, the FLOW-3D modeling based on the Navier-Stokes equations was adopted for the simulation of waves traveling over the sloping bed. The porous body model and direct three-dimensional simulations were employed for the calculation of wave profile and velocity field. Numerical results were favorably compared with experiments. The compare results show that the direct three-dimensional simulations method provides accurate predictions in the all wave propagation regions. The wave and velocity profile are resolved more completed as well as in the not only from outer to the inner porous layer, but also in the surf zone and swash zone. Experimental results show that the process of the turbulence characteristics of the maximum turbulent kinetic energy, turbulent kinetic energy dissipation rate and turbulence intensity take place in the region between the toe of breaker and surface of porous layer. Flow 3D modeling is implemented to compute wave transformation, flow velocity and turbulent. Their differences were compared for the cases of waves propagating over porous and impermeable bed. The results show that the breaker type is significantly influenced by the porous coarse grained bottom. A plunging breaker becomes a collapsing breaker due to the additional resistance and friction of discrete grains within the porous medium. The front of water bore is stopped at the breaking point and ceases to move forward. Therefore, no significant retuned flow occurs in the surf zone.

碩士
國立成功大學
水利及海洋工程學系碩博士班
96
The evolution equation for mild-slope equation model is expended to second order in bottom slope to derive a nonlinear evolution equation of mild-slope equation. The nonlinear evolution equation of mild-slope equation model is used to simulate wave transformations such as shoaling, refraction, diffraction, reflection, wave breaking and energy dissipation. In the condition of bottom slope on 1/10, 1/5 and 1/3, the proposed model can modify wave transformations under the sloping bottom by examining Yang’s (2004) theory and calculate the accurate results. The bottom slope on 1/40 and 1/10, proposed model calculate the accurate results for wave phase with Guza and Bowen’s (1976) theory.

碩士
國立臺灣海洋大學
河海工程學系
100
An experiment in hydraulic model test, this research investigate the deformation of the wave field caused by the variations on the slope bottom when regular wave passes through the submerged breakwater. In this experiment, we aim to discuss the phenomenon of refraction, diffraction, wave height change and wave transformation in wave field behind the submerged breakwater while the waves in different incident angles, wave height and periods. Then we used measurement results plotted as two-dimensional and three -dimensional charts. Therefore, the further understanding of the wave’s deformation in wave field near the submerged breakwater can be achieved. Based on experiments, it is found that the wave transformation and wave height change were found in the back of the submerged breakwater because of the refraction and diffraction. Furthermore, it indicated that the phenomenon of focus from long period wave was more significant than the one from short period wave. Beside, the regions of large wave height will change follow the incident wave direction changed.When wave passed through the submerged breakwater were found the effect of the shoaling、nonlinear wave、refraction and diffraction,then wave produce to the second mode frequency wave,and the second mode frequency wave will lead to a slight error in the Zero-up to analysis of the average wave height. Then it is compared the result of the experiment with the result of Yeh(2011) to understand the variations of the wave height around the submerged breakwater by analyzing the wave height characteristics and wave transformation of the wave passed through the submerged breakwater.

Near-bed horizontal (cross-shore) and vertical velocity measurements over a sloping natural sand beach were acquired in the Hydraulics Research & Testing Facility (HRTF) wave flume. A probe was developed to measure the velocity field close to, but at a fixed distance from the dynamic sand bed. The data were acquired using a three-component acoustic Doppler velocimeter. Optical backscatterance sensors along with a wave staff provided simultaneous suspended sediment concentration and water level data. The near-bed velocity field is examined as close as 1.5 cm above a trough and crest of a ripple under three different types of wave forcing, namely, Stokes waves, Stokes groups, and irregular waves. Although both horizontal and vertical velocity measurements were made, attention is focused primarily on the vertical velocity. The results clearly indicate that the measured near-bed vertical velocity (which was outside the wave-bottom boundary layer) is distinctly non-zero and not well predicted by linear theory. Spectral and bispectral analysis indicate that the vertical velocity responds differently depending on the location over a ripple, and that ripple induced effects on the velocity field are present as high as 4 to 8 cm above the bed (for ripples with wavelengths on the order of 8 cm and amplitudes on the order of 2 cm). At greater heights above the bed the wave-induced motion predicted by linear theory begins to adequately compare with the measurements. Co-spectra etween the near-bed vertical velocity and suspended sediment concentration suggest that the vertical velocity may play a core central role in the transport of sediment than previously thought. These observations raise questions about experiments performed in oscillatory water tunnels, that do not reproduce the vertical velocity structure induced by waves.

碩士
國立中山大學
海洋環境及工程學系研究所
103
In order to apply two-point method (Goda, 1976) on slope, the study in this thesis sets up 14 wave gages on sloping bathymetry in a wave flume, and further uses two-point method (Goda, 1976) to separate incident and reflected waves on time domain traveling on sloping bed. First of all, the experiment applies two neighbor wave gages with depth difference less than 1 cm to separate the incident and reflected waves by the two-point method (Goda, 1976) to get the incident and reflected waves. The result is almost as the same as reflected wave of horizontal bottom. Furthermore, considering the linear wave shoaling theory, this research applies the method on other wave gages with larger depth difference to get series reflection coefficients. The experimental study on the spatial L/2 divergent position also gets a good verification. This experimental investigation not only can obtains the reflection coefficient on slope but also can discuss the error of reflectance calculation following with widening variance of depth between two wave gages, and moreover to compare with former reflection coefficient calculated by numerical model. Besides, the study from discussing second harmonic waves on slope indicates that twice frequency of reflection has the phenomenon of recursion length in spatial; it shows that two-point method could account for high harmonic wave generated from non-linear phenomena.

碩士
國立中興大學
土木工程學系所
105
The evolution and detailed characteristics of the retreated flow during the run-down phase of a solitary wave propagating over 1:3 sloping bottom were investigated experimentally, using particle trajectory method of flow visualization technique and high-speed particle image velocimetry (HSPIV). A series of experiments were performed with several different fields of view, and with several incident solitary waves having wave height (H0) to water depth (h0) ratio of 0.171, 0.263 and 0.363. The velocity fields were obtained by ensemble averaging the repeated measurements. Several preliminary tests were carried out to validate and ensure the quality of the measured data. In addition, the vorticity, acceleration, and pressure gradient were obtained by the velocity profiles. The sensitivity tests for acceleration calculation were performed in order to reduce the bias of the results. Furthermore, an interesting phenomenon of the vortex structure generated from a separated boundary layer in the retreated flow during run-down motion is explored. According to the results obtained qualitatively and quantitatively by utilizing flow visualization technique and HSPIV measurements, related features of flow field and vortex structure, which were hardly discovered and depicted in the past due to the rudimentary equipment, are presented and discussed. Firstly, a striking phenomenon of flow bifurcation during run-up phase is investigated. Second, the characteristics of flow deceleration or acceleration, including the local and convective accelerations, being accompanied by the adverse or favorable pressure gradient in the retreated flow are illustrated. Furthermore, the spatial variation of the critical section where the critical flow with Froude number being equal to unity takes place is investigated. Moreover, the mechanism for the incipient flow separation, accompanied by the formation of the separated shear layer from the sloping bottom during early and first-half middle stages of run-down motion, and the variation of the pressure gradient before, during and after the incipient flow separation are explored. Besides, the evolution of the vortex structure beneath the separated shear layer, including the position and vorticity of the primary vortex core moving offshore under the high-speed meandering stream during second-half middle and late stages of run-down motion are discussed.