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Standing edge waves on a pocket beachCulley, Sara K. 21 March 1986 (has links)
Graduation date: 1986
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Estimating ocean wave directional spectra from measurements of water particle motion by a surface buoy acoustic ranging systemBenevides, Francis Leo January 1990 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 121-125) / Microfiche. / xv, 125 leaves, bound ill. 29 cm
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Three applications of wave measurements in coastal engineeringMcGehee, David D. 17 July 1997 (has links)
Graduation date: 1998 / The figures in the original have a moray pattern. Best scan available.
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Beach foreshore response to long-period waves in the swash-zoneHowd, Peter A. 10 February 1984 (has links)
A field experiment designed to test the hypothesis
that infragravity and lower frequency waves influence the
patterns of erosion and deposition on the beach foreshore
has been carried out. The data show coherent fluctuations
in the foreshore sediment level which can be related to low
frequency wave motions. The fluctuations have heights of
up to 6 cm with typical time scales of 8 to 10 minutes.
They can be characterized in two ways: by the progression
of the fluctuations up the foreshore slope (landward), and
by the decrease in the RNS height of the fluctuations as
they progress landward. The velocity of migration also
changes as the fluctuations progress landward. Analysis of
runup time series obtained by time-lapse photography concurrent
with the sediment level measurements reveals long-period
waves of undetermined origin at frequencies and
phases which strongly suggest that the waves force the
original perturbation in sediment level.
In order to better understand the characteristics of
these sediment level fluctuations, a numerical model of
sediment transport on the foreshore has been developed.
Gradients in sediment transport define erosional and depositional
areas on the foreshore. Runup velocities were
modeled and the results were used in the sediment transport
model. The model predicts that any perturbation in foreshore
elevation will progress landward while decreasing in
amplitude and in velocity, thereby matching the field
observations. Relationships between beach slope and the
profile response clarified by this model are used to explain
the initial formation of the perturbations of sediment
level. / Graduation date: 1984
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The measurement of nearshore bathymetry on intermediate and dissipative beachesC��t��, Jessica Magee 22 January 1999 (has links)
In 1996, Beach et al. first proposed the idea of mounting an echo-sounder on a
Waverunner to measure nearshore beach profiles. This thesis discusses the Coastal Profiling
System, an extension of the original work, which has been utilized to measure nearshore
bathymetry at selected sites along the coasts of North Carolina, Oregon, and Washington.
Position of the Coastal Profiling System is accurately measured five times per second using a
differential global positioning system (DGPS), while depth below the hull is measured by an
acoustic echo-sounder. Surveys can be conducted in waves up to 3 m and in depths of 1-15 m.
The effects of waves, tides, and set-up are eliminated by the co-collection of position and depth
data.
In October 1997, extensive testing of the system took place at the SandyDuck '97 field
experiment in Duck, NC. Nearshore bathymetric surveys were taken simultaneously by the
Coastal Research Amphibious Buggy (CRAB) and the Coastal Profiling System (CPS).
Comparison of the CPS with CRAB measurements interpolated to the same locations showed a
mean bias of 4.6 cm too shallow in the vertical and standard deviations about the bias of 5.5 cm.
The largest differences occur over the steeply sloping flanks of sand bars. The bias statistic, of
central interest to these tests, is confused by the potential of boat tilt and by possible errors in the
CRAB data itself.
In July & August 1998, the system was tested as a tool for long-term coastal monitoring
by the Southwest Washington Coastal Erosion Study in a regional morphology monitoring
program (Ruggiero et al., 1997). A 2-3 km section in approximately the center of each of the four sub-cells of the Columbia River littoral cell, and an anomalous fifth site, was surveyed to map the morphology of each region. Alongshore-averaged profiles were decomposed into underlying AX[superscript m] profiles and deviations from this equilibrium profile. The mean of the exponents was close to 2/3 with m=0.70, but ranged between sites from 0.56 to 0.79. Shape parameters between 0.027 and 0.038 were estimated. Nearshore slopes (0-1 km cross-shore) were calculated from the exponential profile in the dissipative range with a minimum of 0.0067 and a maximum of 0.0089. However, no correlation was seen between the shape parameters and the 1 km nearshore slopes.
An analysis of the deviations of the alongshore-averaged profiles from the equilibrium profile provided an objective method to determine sand bar positions from zero-down-crossings. Each site was characterized by a minimum of two sand bars in 2-6.5 m (NAVD 88) depths with heights of 0.2-2 m, lengths of 164-949 m and volumes of 48-534 m��/m. An additional bar in the swash zone between the +1 m elevation and 1 m depth contour was resolved in some cross-shore profiles. The crest of the bar largest in height was located at 3-4.5 NAVD 88 m at four of the five sites suggesting the profiles vary on similar cross-shore length scales amongst the sub-cells.
A series of surveys in April, June, and October 1998 at the northern most site in Ocean City, WA demonstrated onshore bar migration and seaward accretion of the foreshore. This seasonal response was further quantified between August and October at Fort Canby. Three nearshore profiles surveyed by Willard Bascom et al. (1954) in the 1940s were reoccupied to compare the shape of the morphology 50 years ago to present. These profiles demonstrate accretion of approximately 2 m elevation gains in the nearshore and 26-165 m of shoreline change.
Although the Coastal Profiling System is a highly accurate, mobile and efficient method to obtain nearshore profiles, several improvements have been suggested. Future modifications to the system should include an increase in the precision of the echo-sounder measurements, higher sampling rates, and improvement of the user interface. Additional components may include an onboard navigation system, a thermister to measure temperature and salinity, and a motion sensor to measure roll and pitch of the vehicle. / Graduation date: 1999
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Wave Ship Interaction in Transforming SeasUnknown Date (has links)
In near-shore transforming seas, as waves approach the shoreline, wave shoaling
and sometimes wave breaking take place due to the decreasing water depth. When
a ship advances through the transforming seas, the ship body and waves interact with
each other substantially and can lead to unknown motions of the ship hull. The physical
process of how the wave transforms in the surf zone and how the vehicle actually
behaves when it passes through the transforming seas is a complicated issue that
triggers considerable research interest.
The goal of my research is to characterize the dynamics of a high-speed surface
ship model in transforming seas through a parametric numerical study of the shipwave
interactions. In this study, the vehicle of interest is a surface effect ship (SES)
and we aim to contribute to developing a methodology for simulating the transforming
wave environment, including wave breaking, and its interactions with the SES.
The thesis work uses a commercial software package ANSYS Fluent to generate
numerical waves and model the interface between water and air using the volume
of fluid (VoF) method. A ship motion solver and the dynamic mesh are used to
enable the modeled ship to perform three degree-of-freedom (DoF) motion and the
near-region of the ship hull to deform as well as re-mesh. Non-conformal meshes with hybrid compositions of different cell types and various grid sizes are used in the
simulations for different purposes. Five user-defined functions (UDFs) are dynamically
linked with the flow solver to incorporates ship/grid motions, wave damping
and output of the numerical results. A series of steps were taken sequentially: 1)
validation for ship motions including simulation of a static Wigley hull under steady
flows to compare against previous experimental results by other researchers, and the
comparison between the static SES model under steady flows and the moving SES
model advancing in the calm water; 2) study of the ship with 3 DoF advancing in
calm water of both constant depth and varying depth; 3) validation for numerical
waves, including predictions of numerically progressive waves in both a regular tank
and a tank with a sloped fringing reef to compare with theoretical and experimental
results, respectively; 4) investigation of the transforming characteristics of the wave
traveling over the sloped fringing reef, which mimics the near-shore wave environment
and a study of the dynamics of the SES through transforming waves.
We find that the flow solver used in this study reliably models the wave profiles
along the ship hull. The comparison between a static SES in a current and a moving
SES in calm water at the same Froude number shows that although the velocity fields
around the vehicle are significantly different, the wave profiles inside and outside the
rigid cushion of the vehicle are similar and the resistance force experienced by the
vehicle in the two scenarios agree well over time. We conducted five numerical simulations
of the vehicle traveling from shallow water to deep water across the transition
zone for different Froude numbers. From the results, we find that as the Froude number
increases, the wave resistance force on the vehicle becomes larger in both shallow
water and deep water. In addition, the overall mean resistance force experienced by
the vehicle over the whole trip increases with the Froude number. Statistical analysis
of the wave motions suggests that the energy flux decreases dramatically in the
onshore direction as the waves break. The more severe the wave-breaking process, the greater the decrease in energy flux. Both the increase of Froude number and the
wave steepness apparently increase the resistance force on the vehicle in the shallow
water.
This thesis work captures the impact of the transforming characteristics of
the waves and closely replicates the behavior of how waves interact with a ship in
transforming seas through numerical modeling and simulation. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
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Simulation of coastal processes in a circular wave basinKatzev, David H. 14 January 1992 (has links)
The circular wave basin provides a means of physically modeling the nearshore
without the typical problems associated with end walls. Three different coastal
processes were examined to demonstrate the use of a spiral wavemaker in a circular
wave basin. These were longshore currents, shear waves, and groin circulation. A
beach was designed and constructed to concentrate breaking in a narrow region and
minimize wave reflection. Currents in the longshore direction were generated by both
the motion of the wavemaker and oblique wave approach. Two methods for measuring
nearshore currents were employed. First, a 3-D acoustic current meter was positioned
at various locations in the cross shore and the local radial and tangential velocities
were recorded. Second, a video camera was placed approximately 8 meters above the
wave basin to record the motion of a ball in the nearshore. The video tape was
digitized by an image processor and the motion of the ball was determined.
Measurements of nearshore circulation in the circular wave basin were used to
investigate longshore currents, shear waves, and groin circulation. Average measured
longshore current profiles in the cross shore were compared with numerical model
predictions. An analysis of the existence of shear waves in the circular wave basin
was performed by calculating longshore and cross shore current spectra. Particular
attention was focused on the low frequency end of the spectra where shear waves are
most energetic. Model groins were placed in the circular wave basin and measured
currents were compared to predicted circulation patterns. All three applications
indicated that the circular wave basin is a useful device for simulating coastal processes
in a laboratory environment. / Graduation date: 1992
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Estimation of wave phase speed and nearshore bathymetry using video techniquesStockdon, Hilary F. 15 August 1997 (has links)
Graduation date: 1998
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Directional wavenumber characteristics of short sea wavesSuoja, Nicole Marie January 2000 (has links)
Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 2000. / Includes bibliographical references (leaves 134-141). / by Nicole Marie Suoja. / Ph.D.
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Characterizing long wave agitation in the port of Ngqura using a Boussinesq wave modelStuart, Duncan Charles Alistair 12 1900 (has links)
Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The port of Ngqura is situated on the east coast of South Africa. Since its first operational winter
excessive vessel motions have interrupted container shipping operations and lead to mooring line
failure. A major component contributing to the excessive motions is the presence of seiching in the
port, resonating long waves. This study investigates the long wave generation, penetration into the
port and subsequent resonance in the vicinity of the problem berths.
An extensive literature review identified two predominant types of long waves along the coast of
South Africa. Long waves with periods over 12 min generated by resonant air-water coupling and
then shorter long waves between 30 s and 6 min attributed to bound long wave energy and broadly
speaking, surf beat. A review of the state of the art long wave modelling techniques was included
and contributed to the methodology in this study.
Analysis of simultaneous measurements from the outside and inside of the port confirmed the
generating mechanism of the long waves to be storm systems also responsible for generating short
waves. Long waves outside the port were found to be on average 8% of the height of the short
waves. On average 90% of the long wave height outside the port penetrated the port. The
measurements further identified distinct resonating periods of the long wave energy inside the port.
Calibrated Boussinesq wave models allowed for identification of how long waves penetrated the port
and subsequently resonated. Both surface elevation measurements and white noise spectra were
used as inputs. The penetration mechanisms were attributed to direct diffraction around the main
breakwater as well as reflection off the beach south of the port leading to refraction and reflection
off the lee side of the main breakwater. Tests with both free and bound long waves proved that at
least for some period intervals the long wave energy was indeed bound to short waves. The excessive vessel motions are attributed to berths positioned in line with nodes created by the
resonating long waves; nodes are characterized by strong horizontal currents which can induce surge
motions in vessels. Various long waves between the period intervals of 45 s to 125 s resonate in the
port to generate nodes at the berths of interest.
In conclusion, the port of Ngqura is susceptible to a range of long wave periods resulting in
significant basin oscillations which present nodes at mooring places. As a result of the analyses in this
study the mechanisms of interaction between the port, port basins and the long waves penetrating
into the port directly, or via the surf zone as surf beats, have been modelled, documented and better
understood. This provides the potential for better prediction of severe long wave events and for the
investigation of feasible mitigation measures to prevent damage to moored ships in the port. / AFRIKAANSE OPSOMMING: Die Ngqura hawe is aan die ooskus van Suid-Afrika geleë. Sedert die hawe se eerste operasionele
winterseisoen, het oormatige skeepsbewegings operasies van behoueringskepe onderbreek en gelei
tot faling van vasmeertoue. Die teenwoordigheid van langgolf resonansie is ‘n groot bydraende
faktor tot die oormatige skeepsbewegings. Hierdie studie ondersoek die opwekking, penetrasie en
gevolglike resonansie van langgolwe in die areas aangrensend tot die problematiese kaaie.
‘n Uitgebreide literatuurstudie het twee tipes langgolwe aan die Suid-Afrikaanse kus geïdentifiseer,
naamlik langgolwe met periodes langer as 12 minute wat deur resonante lug-water koppeling
opgewek word en korter langgolwe met periodes tussen 30 s en 6 min wat aan gebonde
langgolfenergie of, meer algemeen, surf beat toegeskryf word. Verder is ‘n studie rakende die
jongste langgolfmodelleringstegnieke ook uitgevoer waaruit die metodiek van hierdie studie bepaal
is.
‘n Analise van gelyktydige opmetings binne en buite die hawe het bevestig dat kortgolwe wat deur
stormsisteme gegenereer word, die opwekkingsmeganisme van lang golwe is. Daar is bevind dat
langgolwe buite die hawe gemiddeld 8% so hoog soos kort golwe is. ‘n Gemiddeld van 90% van die
langgolfhoogte het die hawe penetreer. Die opmetings het ook verder duidelike resonansieperiodes
van langgolfenergie binne die hawe aangedui.
Gekalibreerde Boussinsq-golfmodelle is gebruik om te indentifiseer hoe langgolwe die hawe
binnedring en gevolglik resoneer. Beide oppervlakmetings en wit geraas spektra is as invoerwaardes
vir die model gebruik. Die penetrasiemeganismes is toegeskryf aan diffraksie rondom die hoof
hawemuur asook refleksie vanaf die strand, suid van die hawe, wat lei tot refraksie en refleksie teen
die lykant van die hoof hawemuur. Toetse met vry langgolwe het bewys dat die langgolfenergie, vir
ten minste sommige periode intervalle, aan die kort golwe vebonde is.
Die oormatige skeepsbewegings is toegeskryf aan die kaaie wat in lyn met nodes van die
langgolfresonansie geposisioneer is. Nodes word gekarakteriseer deur sterk horisontale strome wat
surge bewegings in skepe kan veroorsaak. Verskeie langgolwe met periode intervalle tussen 45 s tot
125 s resoneer in die hawe en vorm nodes by die kaaie van belang. Ten slotte, die Ngqura hawe is vatbaar vir ‘n reeks langgolfperiodes wat ossilasies in die bekkens van
die hawe veroorsaak en nodes naby kaaie vorm. As gevolg van die analises in hierdie studie is die
meganismes van interaksie tussen die hawe, sy bekkens en langgolwe wat die hawe direk of via die
brandersone binnedring gemodelleer, gedokumenteer en beter verstaan. Hierdeur is die potensiaal vir beter voorspelling van ernstige langgolftoestande verhoog en is dit moontlik gemaak om
lewensvatbare oplossings vir skade aan vasgemeerde skepe te ondersoek.
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