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Direct Numerical Simulations of Wave...

Patil, Akshay Laxman,

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Direct Numerical Simulations of Wave-Current Interactions Over Bumpy Walls /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Direct Numerical Simulations of Wave-Current Interactions Over Bumpy Walls // Akshay Laxman Patil.
Author:	Patil, Akshay Laxman,
Description:	1 electronic resource (167 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
Subject:	Sediments. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30462689
ISBN:	9798379658281

Direct Numerical Simulations of Wave-Current Interactions Over Bumpy Walls /
Patil, Akshay Laxman,

Direct Numerical Simulations of Wave-Current Interactions Over Bumpy Walls /Akshay Laxman Patil. - 1 electronic resource (167 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Turbulence in estuarine bottom boundary layers influences a variety of biological and anthropogenic activities by driving the hydrodynamics and morphodynamic response of large-scale coastal ocean systems. Thus, a detailed understanding of these boundary layers enables accurate, long-term prediction of the fate of nutrients, pollutants, sediments, and other relevant quantities within estuarine environments. Typically, estuaries are driven by the mean turbulent currents and oscillatory wave motion that interact over naturally rough bottom boundaries. These wave-current interactions often occur non-linearly resulting in complex mean flow responses across the water column.A direct forcing immersed boundary method was implemented in a second-order accurate, staggered finite-difference code enabling the modeling of rough-wall channel flows. Through the definition of the Corey shape factor (Co), the effect of roughness shape characterisation on the mean flow drag was validated to show that the mean flow drag increases with decreasing Co. Using a wide range of full- and minimal-span channel flow simulations with varying Co and friction Reynolds number (Re∗), direct solutions of the governing equations were used to provide insights into the mean flow drag increase.Having established a consistent way to estimate the mean flow drag as a function of the Corey shape factor, the dynamics of current-dominated, wave-current boundary layers over hydraulically smooth walls was studied using direct numerical simulations.For the flat wall, wave-current boundary layer, the mean flow drag did not exhibit any substantial change when compared to the canonical flat wall channel flow. However, the bumpy wall, wave-current boundary layer showed elevated mean flow drag when compared to the canonical flat and bumpy wall channels. Using a turbulent kinetic energy (TKE) and Reynolds stress budget analysis, it was found that there was a decrease in the net TKE production to dissipation rate ratio as a result of the increased TKE dissipation rate. It was also observed that the pressure-strain rate correlations that scramble the TKE across the three diagonal components were comparatively enhanced for the bumpy wall, wave-current case. Consequently, unlike the flat wall, wave-current case, the bumpy wall, wave-current boundary layer exhibits increased mean flow drag.Finally, using direct numerical simulations of a wave-dominated, wave-current boundary layer over rough walls, it was shown that the simple eddy-viscosity-based drag model proposed by Grant and Madsen (1979), which is meant for the wavedominated regime, applies because the near-wall flow is three-component-like and isotropic. Additionally, it was observed that the turbulence in the boundary layer responds quickly to the imposed wave-driven mean shear, thus validating the assumption in the eddy-viscosity type models that the turbulence and mean wave-driven shear are in phase. Collectively, these observations validate the use of simple drag models of wave-current boundary layers in large-scale coastal ocean models in the wave-dominated regime. Further work is needed to develop parameterisations for the bottom drag in current-dominated boundary layers.

English

ISBN: 9798379658281Subjects--Topical Terms:

3566210
Sediments.

Direct Numerical Simulations of Wave-Current Interactions Over Bumpy Walls /
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245 1 0 $a Direct Numerical Simulations of Wave-Current Interactions Over Bumpy Walls / $c Akshay Laxman Patil.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2023
300 $a 1 electronic resource (167 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
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500 $a Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
500 $a Advisors: Gorle, Catherine; Monismith, Stephen Gene; Fringer, Oliver Committee members: Bent, Stacey F.
502 $b Ph.D. $c Stanford University $d 2023.
520 $a Turbulence in estuarine bottom boundary layers influences a variety of biological and anthropogenic activities by driving the hydrodynamics and morphodynamic response of large-scale coastal ocean systems. Thus, a detailed understanding of these boundary layers enables accurate, long-term prediction of the fate of nutrients, pollutants, sediments, and other relevant quantities within estuarine environments. Typically, estuaries are driven by the mean turbulent currents and oscillatory wave motion that interact over naturally rough bottom boundaries. These wave-current interactions often occur non-linearly resulting in complex mean flow responses across the water column.A direct forcing immersed boundary method was implemented in a second-order accurate, staggered finite-difference code enabling the modeling of rough-wall channel flows. Through the definition of the Corey shape factor (Co), the effect of roughness shape characterisation on the mean flow drag was validated to show that the mean flow drag increases with decreasing Co. Using a wide range of full- and minimal-span channel flow simulations with varying Co and friction Reynolds number (Re∗), direct solutions of the governing equations were used to provide insights into the mean flow drag increase.Having established a consistent way to estimate the mean flow drag as a function of the Corey shape factor, the dynamics of current-dominated, wave-current boundary layers over hydraulically smooth walls was studied using direct numerical simulations.For the flat wall, wave-current boundary layer, the mean flow drag did not exhibit any substantial change when compared to the canonical flat wall channel flow. However, the bumpy wall, wave-current boundary layer showed elevated mean flow drag when compared to the canonical flat and bumpy wall channels. Using a turbulent kinetic energy (TKE) and Reynolds stress budget analysis, it was found that there was a decrease in the net TKE production to dissipation rate ratio as a result of the increased TKE dissipation rate. It was also observed that the pressure-strain rate correlations that scramble the TKE across the three diagonal components were comparatively enhanced for the bumpy wall, wave-current case. Consequently, unlike the flat wall, wave-current case, the bumpy wall, wave-current boundary layer exhibits increased mean flow drag.Finally, using direct numerical simulations of a wave-dominated, wave-current boundary layer over rough walls, it was shown that the simple eddy-viscosity-based drag model proposed by Grant and Madsen (1979), which is meant for the wavedominated regime, applies because the near-wall flow is three-component-like and isotropic. Additionally, it was observed that the turbulence in the boundary layer responds quickly to the imposed wave-driven mean shear, thus validating the assumption in the eddy-viscosity type models that the turbulence and mean wave-driven shear are in phase. Collectively, these observations validate the use of simple drag models of wave-current boundary layers in large-scale coastal ocean models in the wave-dominated regime. Further work is needed to develop parameterisations for the bottom drag in current-dominated boundary layers.
546 $a English
590 $a School code: 0212
650 4 $a Sediments. $3 3566210
650 4 $a Anisotropy. $3 596747
650 4 $a Energy. $3 876794
650 4 $a Viscosity. $3 1050706
650 4 $a Ocean currents. $3 519681
650 4 $a Flow velocity. $3 3564851
650 4 $a Reynolds number. $3 3681436
650 4 $a Boundary conditions. $3 3560411
650 4 $a Estuaries. $3 546065
650 4 $a Fluid mechanics. $3 528155
650 4 $a Mathematics. $3 515831
650 4 $a Mechanics. $3 525881
690 $a 0791
690 $a 0204
690 $a 0405
690 $a 0346
710 2 $a Stanford University. $e degree granting institution. $3 3765820
720 1 $a Gorle, Catherine $e degree supervisor.
720 1 $a Monismith, Stephen Gene $e degree supervisor.
720 1 $a Fringer, Oliver $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 84-12B.
790 $a 0212
791 $a Ph.D.
792 $a 2023
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30462689