Browsing by Author "Hsu, TW"

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A turbulence model of wave-induced sheet flow
(2003-12-01)
Hsu, TW
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Chang, HK
;
Hsieh, CM
;
土木工程學系
;
Department of Civil Engineering
This paper present a turbulence model that describes the sediment concentration and turbulent boundary layer of a wave-induced sheet flow. The simultaneous interactions between oscillatory, turbulent flow, and suspended sediment are included. The model specifies the equivalent roughness as a function of the Shields parameter, which is variable with time and is more physically realistic over a mobile flat bed. A wave friction factor, which differs from the conventional rough wall law, is obtained from the velocity gradient. A comparison of the turbulent boundary layer and sediment concentration for different equivalent roughness is given. The present model is shown to provide more accurate estimates than those using an equivalent roughness. Numerical results also show that the presence of suspended sediment retards mean velocity profile and decrease corresponding turbulence dynamic quantities.
A two-point method for estimating wave reflection over a sloping beach
(2003-10-01)
Chang, HK
;
Hsu, TW
;
土木工程學系
;
Department of Civil Engineering
This work presents a frequency-domain method for estimating incident and reflected waves when normally incident waves' propagating over a sloping beach in a wave flume is considered. Linear wave shoaling is applied to determine changes of the wave amplitude and phase due to variations of the bathymetry. The wave reflection coefficient is estimated using wave heights measured at two fixed wave gauges with a distance. The present model demonstrates a high capacity of estimating reflection and shoaling coefficients from synthetic wave-amplitude data. Sensitivity tests for the present model due to measurement errors of wave amplitudes and distance of two probes can more accurately predict the reflection coefficients. The measurement error of wave amplitude affects more significantly than measurement error of distance of two probes on calculating reflection coefficient of waves over a sloping bed. (C) 2003 Elsevier Science Ltd. All rights reserved.
Bragg reflection of waves by different shapes of artificial bars
(2002)
Hsu, TW
;
Chang, HK
;
Tsai, LH
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土木工程學系
;
Department of Civil Engineering
Experiments are performed in a wave flume to demonstrate the Bragg reflection of linear gravity waves by artificial bars. Three different artificial bars with rectangular, triangular and rectified cosinoidal shapes are placed discretely on the seabed for measurement of the Bragg reflection. A series of experimental conditions including the number of bars, the periodic bar spacing, the water depth and various wave conditions are tested. Key parameters influencing the Bragg resonances are investigated. The experimental data are compared with the values from both theoretical and numerical models. Some key parameters have proved to be effective in describing the primary resonances. Predictive equations of the characteristics for the Bragg reflection are proposed in this paper.
Wave reflection over a sloping beach
(2001)
Chang, HK
;
Hsu, TW
;
Liou, JC
;
交大名義發表
;
National Chiao Tung University
A frequency domain method for separating Incident and reflected waves is proposed to account for normally incident waves propagating over a sloping beach in a wave flumes Linear wave shoaling is applied to determine changes of the wave amplitude and phase due to variations of the bathymetry. The wave reflection coefficient is estimated from wave heights measured by two fixed wave gauges with a separated distance. The method is applicable to both monochromatic and random waves. Brief comparisons between theories and the proposed model are made for waves propagating over a sloping seabed.