Parameter Identification of Bottom Friction and Eddy Viscosity of Tidal Flow in Tokyo Bay

In waters such as those surrounding the British Isles, wind currents appear as perturbations superimposed on the tidal currents. In treating this problem, it is assumed that the drift velocity is small compared with the amplitude of the tidal current. In this case, if the instantaneous value of the bottom friction is proportional to the square of the instantaneous velocity, the non-periodic component of friction, averaged over a tidal period, is linearly proportional to the drift velocity. It is assumed that the water is homogeneous and that, above a skin-friction layer close to the bottom, the eddy viscosity is constant with depth. In the steady state, the drift current due to a given wind stress is reduced in the presence of tidal currents. Steady-state solutions, involving the elevation of the surface as well as the currents, are given for a channel of uniform width and depth, a uniformly convergent channel and a non-uniform channel. Numerical calculations, based on the most probable estimates of wind stress, eddy viscosity and bottom friction available at present, are given for several particular cases. A discussion is given of their application to drift currents and surface gradients in the English Channel, a region in which it is proposed to carry out a programme of observations in the near future.

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Tilted drifting jets over a zonally sloped topography: effects of vanishing eddy viscosity

Journal of Fluid Mechanics ◽

10.1017/jfm.2019.579 ◽

2019 ◽

Vol 876 ◽

pp. 939-961

Author(s):

Hemant Khatri ◽

Pavel Berloff

Keyword(s):

Flow Field ◽

Large Scale ◽

Eddy Viscosity ◽

Bottom Topography ◽

Principal Component ◽

Bottom Friction ◽

Nonlinear Interactions ◽

Multiple Jets ◽

Spatio Temporal ◽

Friction Parameters

Oceanic multiple jets are seen to possess spatio-temporal variability imposed by varying bottom topography resulting in jets that can drift and merge. The dynamics of multiple jets over a topographic zonal slope is studied in a two-layer quasi-geostrophic model. The jets tilt from the zonal direction and drift meridionally. In addition to the tilted jets, other large-scale spatial patterns are observed, which are extracted using the principal component analysis. The variances of these patterns are strongly influenced by the values of eddy viscosity and bottom friction parameters. The contribution of the tilted jets to the full flow field decreases with decreasing friction and viscosity parameters, and purely zonal large-scale modes, propagating in the meridional direction, populate the flow field. Linear stability analysis and two-dimensional kinetic-energy spectrum analysis suggest that the zonal modes gain energy from ambient eddies as well as from the tilted jets through nonlinear interactions. However, viscous dissipation and bottom friction tend to suppress the nonlinear interactions, which results in the inhibition of the upscale energy transfer from eddies to the zonal modes. These simulations suggest that, in the presence of topography, alternating jet patterns may be sustained through interactions among various large-scale modes. This is different from the classical zonal jet formation arguments, in which direct eddy forcing maintains the jets.

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The nonlinear effects of the eddy viscosity and the bottom friction on the Lagrangian residual velocity in a narrow model bay

Ocean Dynamics ◽

10.1007/s10236-017-1076-x ◽

2017 ◽

Vol 67 (9) ◽

pp. 1105-1118 ◽

Cited By ~ 5

Author(s):

Fangjing Deng ◽

Wensheng Jiang ◽

Shizuo Feng

Keyword(s):

Eddy Viscosity ◽

Nonlinear Effects ◽

Bottom Friction ◽

Residual Velocity ◽

Lagrangian Residual Velocity

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Production of asari (Manila) clams, Ruditapes philippinarum, during the period of harvest decrease in the 2000s in the Banzu tidal area, Tokyo Bay

Aquatic Living Resources ◽

10.1051/alr/2020016 ◽

2020 ◽

Vol 33 ◽

pp. 14

Author(s):

Mitsuharu Toba ◽

Jun Kakino ◽

Kazuo Tada ◽

Yutaka Kobayashi ◽

Hideharu Tsuchie

Keyword(s):

Field Investigation ◽

Ruditapes Philippinarum ◽

Management Style ◽

Seed Stock ◽

Tokyo Bay ◽

Yearly Variation ◽

Culture Area ◽

Stock Biomass ◽

Tidal Area ◽

High Level

In Tokyo Bay, the harvestable quantity of asari (Manila) clams Ruditapes philippinarum has been decreasing since the late 1990s. We conducted a field investigation on clam density in the Banzu culture area from April 1988 to December 2014 and collected records spanning January 1986 to September 2017 from relevant fisheries cooperative associations to clarify the relationship between the temporal variation in stock abundance and the production activities of fishermen. The yearly variation in clam abundance over the study period was marked by larger decreases in the numbers of larger clams. A large quantity of juvenile clams, beyond the biological productivity of the culture area, may have been introduced as seed stock in the late 1980s despite the high level of harvestable stock. The declines in harvested quantity began in the late 1990s and may have been caused by decreases in harvestable stock despite the continuous addition of seed stock clams. The harvested quantity is likely to be significantly dependent upon the wild clam population, even within the culture area, as the harvestable quantity was not correlated with the quantity of seed stock introduced during the study period. These declines in harvested quantity may have resulted from a decreasing number of operating harvesters due to the low level of harvestable stock and consequently reduced profitability. Two findings were emphasized. A certain management style, based on predictions of the contributions of wild and introduced clams to future stock biomass, is essential for economically-feasible culturing. In areas with less harvestable stock, actions should be taken to maintain the incomes of harvesters while avoiding overexploitation, even if the total harvest quantity decreases.

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Tidal Flow: A Fast and Teachable Maximum Flow Algorithm

OLYMPIADS IN INFORMATICS ◽

10.15388/ioi.2018.03 ◽

2018 ◽

Vol 12 ◽

pp. 25-41

Author(s):

Matthew C. FONTAINE

Keyword(s):

Computer Science ◽

Tidal Flow ◽

Maximum Flow ◽

Efficient Algorithms ◽

Science Students ◽

Flow Algorithm ◽

Maximum Flows

Among the most interesting problems in competitive programming involve maximum flows. However, efficient algorithms for solving these problems are often difficult for students to understand at an intuitive level. One reason for this difficulty may be a lack of suitable metaphors relating these algorithms to concepts that the students already understand. This paper introduces a novel maximum flow algorithm, Tidal Flow, that is designed to be intuitive to undergraduate andpre-university computer science students.

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