Shan-Hwei Ou - Academia.edu (original) (raw)

Papers by Shan-Hwei Ou

Research paper thumbnail of Investigations of Wave Overtopping Over Vertical Seawalls by Typhoon Herb (1996) on Northeastern Coast of Taiwan

(In 4 Volumes, with CD-ROM), 2009

Research paper thumbnail of Beach Profile Characteristics Due to the Inclined Waves

Coastal Engineering 1988, 1989

The result of a theoretical approach shows that the beach profile characteristics is governed by ... more The result of a theoretical approach shows that the beach profile characteristics is governed by a modified Iribarren number which includes the effects among the factors of initial beach slope, wave angle and wave steepness. A series of experiments are conducted in a three-dimensional movable bed model on the conditions of two different initial beach slopes, two incident wave angles as well as several erosive wave steepnesses. The relative importance of each factor involved in the parameter is discussed. It is shown that the modified Iribarren number is effective in the analysis, of beach profile characteristics under the action of inclined waves. The empirical relationships between beach profile changes and the modified Iribarren number are proposed on the basis of experimental results.

Research paper thumbnail of Wave Field Behind the Permeable Detached Breakwater

Coastal Engineering 1988, 1989

Based on the concept of linear superposition, the model for combined wave refraction and diffract... more Based on the concept of linear superposition, the model for combined wave refraction and diffraction developed by Liu et al. is extended to the situation of permeable detached breakwaters in a slowly varying water depth. Two cases are investigated which include a semi-infinite permeable breakwater and a single permeable breakwater. Laboratory results with a particular transmission coefficient in a wave basin are used to compare with the theoretical results. Fair agreements are found.

Research paper thumbnail of WWM Extended to Account for Wave Diffraction on a Current Over a Rapidly Varying Topography

Volume 4: Ocean Engineering; Offshore Renewable Energy, 2008

The WWM (wind wave model) is extended to describe wave refraction-diffraction for wind waves prop... more The WWM (wind wave model) is extended to describe wave refraction-diffraction for wind waves propagating over a rapidly varying seabed in the presence of current. The wave diffraction effect is introduced into the wave action balance equation through the correction of wavenumber and propagation velocities using a diffraction corrected parameter. The formulation is based on the mild-slope equation for wave refraction-diffraction with current effect for a rapidly varying sea bottom. The WWM was used for the numerical implementation based on a finite element scheme. The present model was tested for wave diffraction in a number of different cases, namely from an elliptical shoal on a wave tank, from a cylinder in the presence of a current and from a detached breakwater build on a sloping beach. The comparison of predictions with other numerical models and experiments show that the validity of the model for describing wave propagating over a rapidly varying bottom with current effect is satisfactory. The implementation of this phase-decoupled refraction-diffraction approximation in WWM shows capability of the present model can be used in most practical engineering situations.

Research paper thumbnail of Wave-Induced Vortices around a Submerged Breakwater by FLDV and PIV

Coastal Engineering 2000, 2001

In this paper, a series of experiments were conducted to study the wave-induced vortex behavior a... more In this paper, a series of experiments were conducted to study the wave-induced vortex behavior around a submerged obstacle by applying FLDV (Fiber Laser Doppler Velocimetry) and PIV (Particle Image Velocimetry) techniques. The evolution of vortex generation and shedding in a wave cycle had been clearly visualized in the process of PIV. More precise message about a flow field around a submerged breakwater was measured by FLDV and vorticity and vortex energy were further calculated from the flow field.

Research paper thumbnail of Experimental and Numerical Studies on Wave Transformation Over Artificial Reefs

Coastal Engineering Proceedings, 2011

A laboratory measurement on the flow field, turbulence and wave energy of spilling breakers over ... more A laboratory measurement on the flow field, turbulence and wave energy of spilling breakers over artificial reefs is presented. Instantaneous velocity fields of propagating breaking waves on artificial reefs were measured using Particle Image Velocimeter (PIV) and Bubble Image Velocimeter (BIV). Variations of water surface elevation were observed by using Charge Coupled Device (CCD) cameras with horizontal posture. The experimental results showed that the initial bubble velocity in the aerated region is faster than phase speed with a factor of 1.26. The velocity profiles are identical to the shallow water theory. It is found that a low flow velocity exists due to an opposite but equal onshore and offshore velocity. Significant turbulent kinetic energy and turbulent Reynolds stress are produced by breaking waves in the front of aerated region, then move offshore and decay. The calculated total energy dissipation rate was compared to that based on a bore approximation.

Research paper thumbnail of Applying Piv Measurements on Flow Field of Waves Propagating Over a Single Submerged Porous Elastic Breakwater

Coastal Engineering Proceedings, 2012

The objective of the present study is to investigate the flow field for waves propagating over a ... more The objective of the present study is to investigate the flow field for waves propagating over a submerged poro-elastic breakwater. Particle Image Velocimetry (PIV) measurements were performed in wave conditions with breakwaters made of different materials. The experimental results were compared for various rigid and impermeable, elastic and impermeable, as well as poro-elastic cases. Measurements of wave reflection and transmission induced by soft and permeable submerged breakwaters are both carried out. The results show that the oscillatory motion of elastic submerged breakwater can induce extra reflective waves and result in a larger reflection coefficient. Positive (counterclockwise) and negative (clockwise) vortices are generated due to corner separation and pressure gradients. The negative vortex obtained in a poro-elastic breakwater is generated by the surface friction at the top of the structure. Because of the permeability, it is found that the negative vortex at the upstre...

Research paper thumbnail of Experimental Study on Regular Wave-Induced Scour and Settlement of a Submerged Obstacle Upon a Fluidized Sandbed

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 1, 2010

Bed scouring and structure settlement due to interactions of regular waves and a submerged rectan... more Bed scouring and structure settlement due to interactions of regular waves and a submerged rectangular obstacle in the shallow water regions upon a fluidized fine sandy bed are experimentally investigated. Both impervious and pervious structures are installed on the test soil bed and synchronous measurements of water surface, bed surface, suspended sediment concentration and pore pressures are carried out at locations upstream and downstream. The measurements illustrate that interactions between waves and structures have relatively mild affects on the bed scouring in an unfluidized response. The interactions become more intense in the fluidized responses with significant wave decay over and increasing suspended sediments near above the fluidized beds oscillating with similar period to the loading waves. Meanwhile, the submerged structure starts to settle into the fluidized bed and significant scouring occurs. The interactions are typically greater in a RF test than in a NRF test. Mo...

Research paper thumbnail of Application of the Eemd Method to Investigate Pore Pressure Build-Ups in a Wave-Fluidized Sandbed

Coastal Engineering 2008, 2009

Research paper thumbnail of Wave reflection and vortex evolution in Bragg scattering in real fluids

Ocean Engineering, 2014

ABSTRACT The vortex generation and dissipation accompanying Bragg scattering of water waves propa... more ABSTRACT The vortex generation and dissipation accompanying Bragg scattering of water waves propagating over a series of submerged rectangular breakwaters are investigated both numerically and experimentally. The present model, which takes effects of non-linearity, viscosity and turbulence into consideration, is applied to simulate the entire vortex evolution process as water waves pass over a series of artificial rectangular bars. Particle image velocimetry is used to measure the velocity field in the vicinity of the bars. The numerical model is validated via a comparison with measured water surface elevations and velocity fields; the results show good agreement. The mechanism of vortex evolution and its influence on the interaction of water waves with submerged structures for cases with and without resonance are studied. The corresponding wave reflection coefficients for both cases are calculated and compared with experimental data and solutions based on linear wave theory. Examination of the turbulence properties shows that the turbulent intensity decreases on the weather side but increases on the lee side under the Bragg scattering conditions.

Research paper thumbnail of An application of Boussinesq equations to Bragg reflection of irregular waves

Ocean Engineering, 2007

A numerical model based on the second-order fully nonlinear Boussinesq equations of Wei et al. [1... more A numerical model based on the second-order fully nonlinear Boussinesq equations of Wei et al. [1995. Journal of Waterway, Port, Coastal and Ocean Engineering 121 (5), 251-263] is developed to simulate the Bragg reflection of both regular and irregular surface waves scattered by submerged bars. Particularly for incident regular waves, the computed results are observed to agree very well with the existing experimental data as presented by Davies and Heathershaw [1984. Journal of Fluid Mechanics 144, 419-446] and Kirby and Anton [1990. Proceedings of the 22nd International Conference on Coastal Engineering, ASCE, New York, pp. 757-768). In the case of incident irregular waves, the simulated results reveal that the distribution of Bragg reflection from irregular waves becomes more flat than that of regular waves. Due to lack of experimental data, the numerical results for incident irregular waves are compared with those of the evolution equation of the mild-slope equation [Hsu et al., 2002 Proceedings of the 24th Ocean Engineering Conference in Taiwan, pp. 70-77 (in Chinese)]. In addition, several parameters such as the number of bars, the relative height of bars and the spacing of bars affecting Bragg reflection are also discussed.

Research paper thumbnail of Experimental investigations on developments of velocity field near above a sandy bed during regular wave-induced fluidized responses

Ocean Engineering, 2011

Regular waves were applied in a laboratory flume to investigate the evolutions of the velocity fi... more Regular waves were applied in a laboratory flume to investigate the evolutions of the velocity fields near above a fine sandy bed (d50=0.073mm) during fluidized responses. Measurements of 2D velocity components and suspended sediment concentration (SSC) at 1cm above the bed in addition to water surface displacements and sub-soil pore pressures were carried out with an acoustic Doppler velocimeter and

Research paper thumbnail of On the mass transport of water waves in a turbulent boundary layer

Ocean Engineering, 1994

ABSTRACT

Research paper thumbnail of Transformation of Progressive Waves Propagating Obliquely on Gentle Slope

Journal of Waterway, Port, Coastal, and Ocean Engineering, 2004

This paper reports the results of a new mathematical derivation for the transformation of a progr... more This paper reports the results of a new mathematical derivation for the transformation of a progressive wave propagating obliquely on a gentle slope. On the basis of the conservation principle of wave motion and in a wave-ray coordinate system, an explicit expression for the velocity potential of the wave field is derived as a function of the bottom slope ␣ perturbed to a second order in an Eulerian coordinate system. Wave profile is then obtained in the Lagrangian system. Together, these enable the description of the features of wave shoaling and refraction in the direction of wave propagation from deep to shallow water, particularly, the process of successive deformation of a wave profile.

Research paper thumbnail of Review of Countermeasures against Beach Erosion on the Taiwanese Coast

Coastal Management, 2008

ABSTRACT Beach erosion is one of the most significant coastal preservation problems in the world.... more ABSTRACT Beach erosion is one of the most significant coastal preservation problems in the world. This study first briefly addresses the influences of human activity on beach erosion. The seriousness of beach erosion in Taiwan has received considerable attention since the 1960s, following rapid population growth and economic development in the coastal areas. Hard solutions of stabilized structures against beach erosion in Taiwan at that time are reviewed based on their effectiveness in protecting property and their ability to produce a landscape that harmonizes with the adjacent coastal environment. Soft coastal defense solutions implemented recently in coastal regions in Taiwan are introduced and their benefits are discussed. This study concludes that various methods designed to prevent wave- and current-induced beach erosion should be based on analyses of nearshore hydrodynamics, sediment transport, coastal processes, and physiographic features of beaches.

Research paper thumbnail of Wave refraction–diffraction effect in the wind wave model WWM

Coastal Engineering, 2011

Based on the extended mild-slope equation, the wind wave model (WWM; Hsu et al., 2005) is modifie... more Based on the extended mild-slope equation, the wind wave model (WWM; Hsu et al., 2005) is modified to account for wave refraction, diffraction and reflection for wind waves propagating over a rapidly varying seabed in the presence of current. The combined effect of the higher-order bottom effect terms is incorporated into the wave action balance equation through the correction of

Research paper thumbnail of On the prediction of beach changes by a new 2-D empirical eigenfunction model

Coastal Engineering, 1994

A new two-dimensional (2-D) empirical eigenfunction model is developed for the prediction of beac... more A new two-dimensional (2-D) empirical eigenfunction model is developed for the prediction of beach changes due to cross-shore and longshore sediment transports. Beach profile data, measured every two months along six segmented detached breakwaters, were analyzed to generate spatial and temporal orthogonal eigenfunctions. The temporal eigenfunctions are predicted through the use of the Markov process and a linear regression method as a time series to forecast changes in the sea bottom. This model simplifies the complex representation of eigenfunctions presented by Hsu et al. (1986), and takes advantage of this simplication to reduce artificial errors and save computer time for further applications. The predictability of the proposed model is examined through field observations as well as predictions of existing empirical eigenfunction models. The result shows that this 2-D empirical eigenfunction model is efficient and advisable for the prediction of the variability of beach changes around coastal structures.

Research paper thumbnail of A three-point method for estimating wave reflection of obliquely incident waves over a sloping bottom

Coastal Engineering, 2008

A three-point method for estimating wave reflection is proposed to account for monochromatic obli... more A three-point method for estimating wave reflection is proposed to account for monochromatic oblique incident waves propagating over a sloping beach. The amplitudes of reflected wave and incident wave are separated using wave amplitudes measured at three fixed wave gauges with a distance. The applicability of the theory is verified by comparing the simulated results with the available theoretical, numerical and experimental results for the estimation of wave reflection. The sensitivity is also tested to provide a more accurate prediction of the reflection coefficient.

Research paper thumbnail of Wave setup and setdown generated by obliquely incident waves

Coastal Engineering, 2006

An analytical theory is developed for the wave setup and setdown induced by obliquely incident wa... more An analytical theory is developed for the wave setup and setdown induced by obliquely incident waves on an impermeable swell-built beach profile. The wave setup and setdown are found to decrease as wave obliquity increases. The incorporation of wave obliquity in wave setup and setdown formulation offers the physical reality in engineering applications. The general solutions presented in this paper

Research paper thumbnail of Researches on the Deformation of Wave Spectra in Intermediate Water Area by Calculation

Coastal Engineering 1972, 1972

In order to devise more rational approach to predicat the wave features in intermediate water are... more In order to devise more rational approach to predicat the wave features in intermediate water area, energy spectra in deep water area are to be changed to histograms, and every stripe of the histogram is to represent an elementary small amplitude wave. The deformation of such elementary waves over intermediate water area can be calculated theoretically by energy flux equation. Spectra in intermediate area can be worked out by summing up the wave energies deformed by shoaling, bottom friction and refraction. Calculation are carried out by computer. The peak of spectra will never change when it propagates from deep water to intermediate water area if the bottom contours are parallel to the shore line. Tangible process for using this approach to practical engineering problems is pending investigation.

Research paper thumbnail of Investigations of Wave Overtopping Over Vertical Seawalls by Typhoon Herb (1996) on Northeastern Coast of Taiwan

(In 4 Volumes, with CD-ROM), 2009

Research paper thumbnail of Beach Profile Characteristics Due to the Inclined Waves

Coastal Engineering 1988, 1989

The result of a theoretical approach shows that the beach profile characteristics is governed by ... more The result of a theoretical approach shows that the beach profile characteristics is governed by a modified Iribarren number which includes the effects among the factors of initial beach slope, wave angle and wave steepness. A series of experiments are conducted in a three-dimensional movable bed model on the conditions of two different initial beach slopes, two incident wave angles as well as several erosive wave steepnesses. The relative importance of each factor involved in the parameter is discussed. It is shown that the modified Iribarren number is effective in the analysis, of beach profile characteristics under the action of inclined waves. The empirical relationships between beach profile changes and the modified Iribarren number are proposed on the basis of experimental results.

Research paper thumbnail of Wave Field Behind the Permeable Detached Breakwater

Coastal Engineering 1988, 1989

Based on the concept of linear superposition, the model for combined wave refraction and diffract... more Based on the concept of linear superposition, the model for combined wave refraction and diffraction developed by Liu et al. is extended to the situation of permeable detached breakwaters in a slowly varying water depth. Two cases are investigated which include a semi-infinite permeable breakwater and a single permeable breakwater. Laboratory results with a particular transmission coefficient in a wave basin are used to compare with the theoretical results. Fair agreements are found.

Research paper thumbnail of WWM Extended to Account for Wave Diffraction on a Current Over a Rapidly Varying Topography

Volume 4: Ocean Engineering; Offshore Renewable Energy, 2008

The WWM (wind wave model) is extended to describe wave refraction-diffraction for wind waves prop... more The WWM (wind wave model) is extended to describe wave refraction-diffraction for wind waves propagating over a rapidly varying seabed in the presence of current. The wave diffraction effect is introduced into the wave action balance equation through the correction of wavenumber and propagation velocities using a diffraction corrected parameter. The formulation is based on the mild-slope equation for wave refraction-diffraction with current effect for a rapidly varying sea bottom. The WWM was used for the numerical implementation based on a finite element scheme. The present model was tested for wave diffraction in a number of different cases, namely from an elliptical shoal on a wave tank, from a cylinder in the presence of a current and from a detached breakwater build on a sloping beach. The comparison of predictions with other numerical models and experiments show that the validity of the model for describing wave propagating over a rapidly varying bottom with current effect is satisfactory. The implementation of this phase-decoupled refraction-diffraction approximation in WWM shows capability of the present model can be used in most practical engineering situations.

Research paper thumbnail of Wave-Induced Vortices around a Submerged Breakwater by FLDV and PIV

Coastal Engineering 2000, 2001

In this paper, a series of experiments were conducted to study the wave-induced vortex behavior a... more In this paper, a series of experiments were conducted to study the wave-induced vortex behavior around a submerged obstacle by applying FLDV (Fiber Laser Doppler Velocimetry) and PIV (Particle Image Velocimetry) techniques. The evolution of vortex generation and shedding in a wave cycle had been clearly visualized in the process of PIV. More precise message about a flow field around a submerged breakwater was measured by FLDV and vorticity and vortex energy were further calculated from the flow field.

Research paper thumbnail of Experimental and Numerical Studies on Wave Transformation Over Artificial Reefs

Coastal Engineering Proceedings, 2011

A laboratory measurement on the flow field, turbulence and wave energy of spilling breakers over ... more A laboratory measurement on the flow field, turbulence and wave energy of spilling breakers over artificial reefs is presented. Instantaneous velocity fields of propagating breaking waves on artificial reefs were measured using Particle Image Velocimeter (PIV) and Bubble Image Velocimeter (BIV). Variations of water surface elevation were observed by using Charge Coupled Device (CCD) cameras with horizontal posture. The experimental results showed that the initial bubble velocity in the aerated region is faster than phase speed with a factor of 1.26. The velocity profiles are identical to the shallow water theory. It is found that a low flow velocity exists due to an opposite but equal onshore and offshore velocity. Significant turbulent kinetic energy and turbulent Reynolds stress are produced by breaking waves in the front of aerated region, then move offshore and decay. The calculated total energy dissipation rate was compared to that based on a bore approximation.

Research paper thumbnail of Applying Piv Measurements on Flow Field of Waves Propagating Over a Single Submerged Porous Elastic Breakwater

Coastal Engineering Proceedings, 2012

The objective of the present study is to investigate the flow field for waves propagating over a ... more The objective of the present study is to investigate the flow field for waves propagating over a submerged poro-elastic breakwater. Particle Image Velocimetry (PIV) measurements were performed in wave conditions with breakwaters made of different materials. The experimental results were compared for various rigid and impermeable, elastic and impermeable, as well as poro-elastic cases. Measurements of wave reflection and transmission induced by soft and permeable submerged breakwaters are both carried out. The results show that the oscillatory motion of elastic submerged breakwater can induce extra reflective waves and result in a larger reflection coefficient. Positive (counterclockwise) and negative (clockwise) vortices are generated due to corner separation and pressure gradients. The negative vortex obtained in a poro-elastic breakwater is generated by the surface friction at the top of the structure. Because of the permeability, it is found that the negative vortex at the upstre...

Research paper thumbnail of Experimental Study on Regular Wave-Induced Scour and Settlement of a Submerged Obstacle Upon a Fluidized Sandbed

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 1, 2010

Bed scouring and structure settlement due to interactions of regular waves and a submerged rectan... more Bed scouring and structure settlement due to interactions of regular waves and a submerged rectangular obstacle in the shallow water regions upon a fluidized fine sandy bed are experimentally investigated. Both impervious and pervious structures are installed on the test soil bed and synchronous measurements of water surface, bed surface, suspended sediment concentration and pore pressures are carried out at locations upstream and downstream. The measurements illustrate that interactions between waves and structures have relatively mild affects on the bed scouring in an unfluidized response. The interactions become more intense in the fluidized responses with significant wave decay over and increasing suspended sediments near above the fluidized beds oscillating with similar period to the loading waves. Meanwhile, the submerged structure starts to settle into the fluidized bed and significant scouring occurs. The interactions are typically greater in a RF test than in a NRF test. Mo...

Research paper thumbnail of Application of the Eemd Method to Investigate Pore Pressure Build-Ups in a Wave-Fluidized Sandbed

Coastal Engineering 2008, 2009

Research paper thumbnail of Wave reflection and vortex evolution in Bragg scattering in real fluids

Ocean Engineering, 2014

ABSTRACT The vortex generation and dissipation accompanying Bragg scattering of water waves propa... more ABSTRACT The vortex generation and dissipation accompanying Bragg scattering of water waves propagating over a series of submerged rectangular breakwaters are investigated both numerically and experimentally. The present model, which takes effects of non-linearity, viscosity and turbulence into consideration, is applied to simulate the entire vortex evolution process as water waves pass over a series of artificial rectangular bars. Particle image velocimetry is used to measure the velocity field in the vicinity of the bars. The numerical model is validated via a comparison with measured water surface elevations and velocity fields; the results show good agreement. The mechanism of vortex evolution and its influence on the interaction of water waves with submerged structures for cases with and without resonance are studied. The corresponding wave reflection coefficients for both cases are calculated and compared with experimental data and solutions based on linear wave theory. Examination of the turbulence properties shows that the turbulent intensity decreases on the weather side but increases on the lee side under the Bragg scattering conditions.

Research paper thumbnail of An application of Boussinesq equations to Bragg reflection of irregular waves

Ocean Engineering, 2007

A numerical model based on the second-order fully nonlinear Boussinesq equations of Wei et al. [1... more A numerical model based on the second-order fully nonlinear Boussinesq equations of Wei et al. [1995. Journal of Waterway, Port, Coastal and Ocean Engineering 121 (5), 251-263] is developed to simulate the Bragg reflection of both regular and irregular surface waves scattered by submerged bars. Particularly for incident regular waves, the computed results are observed to agree very well with the existing experimental data as presented by Davies and Heathershaw [1984. Journal of Fluid Mechanics 144, 419-446] and Kirby and Anton [1990. Proceedings of the 22nd International Conference on Coastal Engineering, ASCE, New York, pp. 757-768). In the case of incident irregular waves, the simulated results reveal that the distribution of Bragg reflection from irregular waves becomes more flat than that of regular waves. Due to lack of experimental data, the numerical results for incident irregular waves are compared with those of the evolution equation of the mild-slope equation [Hsu et al., 2002 Proceedings of the 24th Ocean Engineering Conference in Taiwan, pp. 70-77 (in Chinese)]. In addition, several parameters such as the number of bars, the relative height of bars and the spacing of bars affecting Bragg reflection are also discussed.

Research paper thumbnail of Experimental investigations on developments of velocity field near above a sandy bed during regular wave-induced fluidized responses

Ocean Engineering, 2011

Regular waves were applied in a laboratory flume to investigate the evolutions of the velocity fi... more Regular waves were applied in a laboratory flume to investigate the evolutions of the velocity fields near above a fine sandy bed (d50=0.073mm) during fluidized responses. Measurements of 2D velocity components and suspended sediment concentration (SSC) at 1cm above the bed in addition to water surface displacements and sub-soil pore pressures were carried out with an acoustic Doppler velocimeter and

Research paper thumbnail of On the mass transport of water waves in a turbulent boundary layer

Ocean Engineering, 1994

ABSTRACT

Research paper thumbnail of Transformation of Progressive Waves Propagating Obliquely on Gentle Slope

Journal of Waterway, Port, Coastal, and Ocean Engineering, 2004

This paper reports the results of a new mathematical derivation for the transformation of a progr... more This paper reports the results of a new mathematical derivation for the transformation of a progressive wave propagating obliquely on a gentle slope. On the basis of the conservation principle of wave motion and in a wave-ray coordinate system, an explicit expression for the velocity potential of the wave field is derived as a function of the bottom slope ␣ perturbed to a second order in an Eulerian coordinate system. Wave profile is then obtained in the Lagrangian system. Together, these enable the description of the features of wave shoaling and refraction in the direction of wave propagation from deep to shallow water, particularly, the process of successive deformation of a wave profile.

Research paper thumbnail of Review of Countermeasures against Beach Erosion on the Taiwanese Coast

Coastal Management, 2008

ABSTRACT Beach erosion is one of the most significant coastal preservation problems in the world.... more ABSTRACT Beach erosion is one of the most significant coastal preservation problems in the world. This study first briefly addresses the influences of human activity on beach erosion. The seriousness of beach erosion in Taiwan has received considerable attention since the 1960s, following rapid population growth and economic development in the coastal areas. Hard solutions of stabilized structures against beach erosion in Taiwan at that time are reviewed based on their effectiveness in protecting property and their ability to produce a landscape that harmonizes with the adjacent coastal environment. Soft coastal defense solutions implemented recently in coastal regions in Taiwan are introduced and their benefits are discussed. This study concludes that various methods designed to prevent wave- and current-induced beach erosion should be based on analyses of nearshore hydrodynamics, sediment transport, coastal processes, and physiographic features of beaches.

Research paper thumbnail of Wave refraction–diffraction effect in the wind wave model WWM

Coastal Engineering, 2011

Based on the extended mild-slope equation, the wind wave model (WWM; Hsu et al., 2005) is modifie... more Based on the extended mild-slope equation, the wind wave model (WWM; Hsu et al., 2005) is modified to account for wave refraction, diffraction and reflection for wind waves propagating over a rapidly varying seabed in the presence of current. The combined effect of the higher-order bottom effect terms is incorporated into the wave action balance equation through the correction of

Research paper thumbnail of On the prediction of beach changes by a new 2-D empirical eigenfunction model

Coastal Engineering, 1994

A new two-dimensional (2-D) empirical eigenfunction model is developed for the prediction of beac... more A new two-dimensional (2-D) empirical eigenfunction model is developed for the prediction of beach changes due to cross-shore and longshore sediment transports. Beach profile data, measured every two months along six segmented detached breakwaters, were analyzed to generate spatial and temporal orthogonal eigenfunctions. The temporal eigenfunctions are predicted through the use of the Markov process and a linear regression method as a time series to forecast changes in the sea bottom. This model simplifies the complex representation of eigenfunctions presented by Hsu et al. (1986), and takes advantage of this simplication to reduce artificial errors and save computer time for further applications. The predictability of the proposed model is examined through field observations as well as predictions of existing empirical eigenfunction models. The result shows that this 2-D empirical eigenfunction model is efficient and advisable for the prediction of the variability of beach changes around coastal structures.

Research paper thumbnail of A three-point method for estimating wave reflection of obliquely incident waves over a sloping bottom

Coastal Engineering, 2008

A three-point method for estimating wave reflection is proposed to account for monochromatic obli... more A three-point method for estimating wave reflection is proposed to account for monochromatic oblique incident waves propagating over a sloping beach. The amplitudes of reflected wave and incident wave are separated using wave amplitudes measured at three fixed wave gauges with a distance. The applicability of the theory is verified by comparing the simulated results with the available theoretical, numerical and experimental results for the estimation of wave reflection. The sensitivity is also tested to provide a more accurate prediction of the reflection coefficient.

Research paper thumbnail of Wave setup and setdown generated by obliquely incident waves

Coastal Engineering, 2006

An analytical theory is developed for the wave setup and setdown induced by obliquely incident wa... more An analytical theory is developed for the wave setup and setdown induced by obliquely incident waves on an impermeable swell-built beach profile. The wave setup and setdown are found to decrease as wave obliquity increases. The incorporation of wave obliquity in wave setup and setdown formulation offers the physical reality in engineering applications. The general solutions presented in this paper

Research paper thumbnail of Researches on the Deformation of Wave Spectra in Intermediate Water Area by Calculation

Coastal Engineering 1972, 1972

In order to devise more rational approach to predicat the wave features in intermediate water are... more In order to devise more rational approach to predicat the wave features in intermediate water area, energy spectra in deep water area are to be changed to histograms, and every stripe of the histogram is to represent an elementary small amplitude wave. The deformation of such elementary waves over intermediate water area can be calculated theoretically by energy flux equation. Spectra in intermediate area can be worked out by summing up the wave energies deformed by shoaling, bottom friction and refraction. Calculation are carried out by computer. The peak of spectra will never change when it propagates from deep water to intermediate water area if the bottom contours are parallel to the shore line. Tangible process for using this approach to practical engineering problems is pending investigation.