diplomska naloga
Tanja Tofil (Author), Dušan Žagar (Mentor), Mojca Šraj (Thesis defence commission member), Primož Banovec (Thesis defence commission member)

Abstract

Privzdigovanje delcev sedimenta z dna je proces, ki poteka zaradi različnih dejavnikov, med katerimi je tudi valovanje. Valovi lahko nastanejo zaradi vetra, tektonskih aktivnosti, privlačnosti sonca in lune, raznih gibajočih se predmetov v morju in drugih vzrokov. V diplomski nalogi smo se osredotočili na vpliv vetrnih valov na strižne napetosti pri dnu (napetosti, ki nastanejo ob stiku sedimenta in premikajočega se vodnega telesa). Da bi strižne napetosti izračunali, je potrebno poznavanje višine in periode valovanja po celotni obravnavani površini in v vsakem časovnem koraku simulacije. Ta parametra lahko dobimo z opazovanjem, meritvami ali s pomočjo matematičnih modelov. Sedimentacijski modul matematičnega modela PCFLOW3D ima vgrajene enostavne enačbe za izračun višine in periode valov (Bretschneider, 1952), a so rezultati, ki nam jih dajejo, vprašljivi. Da bi našli ustreznejšo metodo smo v diplomski nalogi naredili kratek pregled sedmih različnih empiričnih metod in enačb za račun značilne višine in periode valovanja. S pomočjo orodja MS Excel smo metode preizkusili pri različnih vhodnih podatkih (jakostih vetra, privetriščih, globinah) in rezultate primerjali med seboj ter z Darbyshire in Draper nomogrami (Koutitas, 1988). Ugotovili smo, da vse nove metode dajo približno za tretjino nižje rezultate kot Bretschneiderjeva metoda, zato je enačbe v modelu PCFLOW3D potrebno zamenjati s primernejšimi. Ker se rezultati preizkušenih metod le malo razlikujejo med seboj, bodo za določitev najprimernejše potrebne dodatne raziskave, primerjava z rezultati modela valovanja tretje generacije (SWAN) in z meritvami na boji Vida, ki jo upravlja Nacionalni inštitut za biologijo.

Keywords

gradbeništvo;diplomska dela;UNI;VOI;vetrni valovi;strižne napetosti na dnu;resuspendiranje;model PCFLOW3D;

Data

Language: Slovenian
Year of publishing:
Source: Ljubljana
Typology: 2.11 - Undergraduate Thesis
Organization: UL FGG - Faculty of Civil and Geodetic Engineering
Publisher: [T. Tofil]
UDC: 004.4:551.466(043.2)
COBISS: 6348897 Link will open in a new window
Views: 2621
Downloads: 510
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Other data

Secondary language: English
Secondary title: Influence of wind-wave parameterisation on bed shear stress
Secondary abstract: Resuspending of the sediment particles from the bottom is a process generated by different causes. One of them are waves, which can be generated by wind, tectonic activity, moon and sun attraction, different moving objects in the sea and other causes. In this work we discussed the effect of wind generated waves on the bottom shear stress (the tension created at the contact of the sediment and the moving water). To calculate the shear stress wave heights and wave periods are needed throughout the surface and in every time step. These parameters can be obtained with observations, measurements or with the help of mathematical models. Simplified wave height and period equations (Bretschneider, 1952) are already a part of the sedimentation module of the PCFLOW3D model; however, the results obtained are questionable. In order to find a better method we made a short review of seven different empirical methods for calculation of the significant wave height and period. Using the MS Excel we tested these methods on different input data (wind speed, fetch length and water depth) and compared the results with each other and with the Darbyshire and Draper nomograms (Koutitas, 1988). The results obtained by all tested methods are approximately for one third lower than the results obtained using Bretschneider’s method. Therefore the equations in the PCFLOW3D model need to be replaced. As the results of the tested methods do not differ significantly, additional research is needed: a comparison with the results of the third generation wave model (SWAN) and with measurements at the buoy Vida operated by the National institute of biology.
Secondary keywords: graduation thesis;civil engineering;wind generated waves;bottom shear stress;resuspending;PCFLOW3D model;
File type: application/pdf
Type (COBISS): Bachelor thesis/paper
Thesis comment: Univ. v Ljubljani, Fak. za gradbeništvo in geodezijo
Pages: XII, 59 str.
Type (ePrints): thesis
Title (ePrints): Influence of wind-wave parameterisation on bed shear stress
Keywords (ePrints): vetrni valovi;strižne napetosti pri dnu;resuspendiranje;model PCFLOW3D
Keywords (ePrints, secondary language): wind generated waves;bottom shear stress;resuspending;PCFLOW3D model
Abstract (ePrints): Privzdigovanje delcev sedimenta z dna je proces, ki poteka zaradi različnih dejavnikov, med katerimi je tudi valovanje. Valovi lahko nastanejo zaradi vetra, tektonskih aktivnosti, privlačnosti sonca in lune, raznih gibajočih se predmetov v morju in drugih vzrokov. V diplomski nalogi smo se osredotočili na vpliv vetrnih valov na strižne napetosti pri dnu (napetosti, ki nastanejo ob stiku sedimenta in premikajočega se vodnega telesa). Da bi strižne napetosti izračunali, je potrebno poznavanje višine in periode valovanja po celotni obravnavani površini in v vsakem časovnem koraku simulacije. Ta parametra lahko dobimo z opazovanjem, meritvami ali s pomočjo matematičnih modelov. Sedimentacijski modul matematičnega modela PCFLOW3D ima vgrajene enostavne enačbe za izračun višine in periode valov (Bretschneider, 1952), a so rezultati, ki nam jih dajejo, vprašljivi. Da bi našli ustreznejšo metodo smo v diplomski nalogi naredili kratek pregled sedmih različnih empiričnih metod in enačb za račun značilne višine in periode valovanja. S pomočjo orodja MS Excel smo metode preizkusili pri različnih vhodnih podatkih (jakostih vetra, privetriščih, globinah) in rezultate primerjali med seboj ter z Darbyshire in Draper nomogrami (Koutitas, 1988). Ugotovili smo, da vse nove metode dajo približno za tretjino nižje rezultate kot Bretschneiderjeva metoda, zato je enačbe v modelu PCFLOW3D potrebno zamenjati s primernejšimi. Ker se rezultati preizkušenih metod le malo razlikujejo med seboj, bodo za določitev najprimernejše potrebne dodatne raziskave, primerjava z rezultati modela valovanja tretje generacije (SWAN) in z meritvami na boji Vida, ki jo upravlja Nacionalni inštitut za biologijo.
Abstract (ePrints, secondary language): Resuspending of the sediment particles from the bottom is a process generated by different causes. One of them are waves, which can be generated by wind, tectonic activity, moon and sun attraction, different moving objects in the sea and other causes. In this work we discussed the effect of wind generated waves on the bottom shear stress (the tension created at the contact of the sediment and the moving water). To calculate the shear stress wave heights and wave periods are needed throughout the surface and in every time step. These parameters can be obtained with observations, measurements or with the help of mathematical models. Simplified wave height and period equations (Bretschneider, 1952) are already a part of the sedimentation module of the PCFLOW3D model; however, the results obtained are questionable. In order to find a better method we made a short review of seven different empirical methods for calculation of the significant wave height and period. Using the MS Excel we tested these methods on different input data (wind speed, fetch length and water depth) and compared the results with each other and with the Darbyshire and Draper nomograms (Koutitas, 1988). The results obtained by all tested methods are approximately for one third lower than the results obtained using Bretschneider’s method. Therefore the equations in the PCFLOW3D model need to be replaced. As the results of the tested methods do not differ significantly, additional research is needed: a comparison with the results of the third generation wave model (SWAN) and with measurements at the buoy Vida operated by the National institute of biology.
Keywords (ePrints, secondary language): wind generated waves;bottom shear stress;resuspending;PCFLOW3D model
ID: 8312906