Influence of horizontal eddy viscosity and bottom friction coefficients on morphodynamic evaluations

2021 ◽  
Author(s):  
N. Saichenthur ◽  
K. Murali ◽  
V. Sundar
Keyword(s):  
Eddy Viscosity ◽  
Bottom Friction ◽  
Friction Coefficients

Note on wind drift in a channel in the presence of tidal currents

1953 ◽  
Vol 219 (1139) ◽  
pp. 426-446 ◽  
Keyword(s):  
Steady State ◽  
Drift Velocity ◽  
Wind Stress ◽  
Eddy Viscosity ◽  
Tidal Currents ◽  
Bottom Friction ◽  
Convergent Channel ◽  
Tidal Period ◽  
Uniform Channel ◽  
Wind Currents

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.

scholarly journals Application of Surface Spline Interpolation in Inversion of Bottom Friction Coefficients

2017 ◽  
Vol 34 (9) ◽  
pp. 2021-2028 ◽  
Author(s):  
Zheng Guo ◽  
Haidong Pan ◽  
Wei Fan ◽  
Xianqing Lv
Keyword(s):  
Bohai Sea ◽  
Spline Interpolation ◽  
Linear Interpolation ◽  
Bottom Friction ◽  
New Method ◽  
Practical Application ◽  
Friction Coefficients ◽  
Tidal Model ◽  
Surface Spline ◽  
Nonlinear Distribution

AbstractA new method for the inversion of bottom friction coefficients (BFCs) in a two-dimensional tidal model is proposed in this study. In this method, the field of BFCs is constructed by interpolating values at independent points using a surface spline. The surface spline interpolation has an advantage: that the constructed surface is smoother than the surface constructed by the traditionally used linear interpolation, which has unrealistic extrema. The method is validated in twin experiments where the prescribed nonlinear distribution of BFCs are better inverted with the surface spline interpolation. In practical experiments, the BFCs are inverted and the M2 tide in the Bohai Sea is simulated by assimilating the TOPEX/Poseidon (T/P) data. The small errors between the simulation results and the observations, as well as the accurate cotidal charts, demonstrate the feasibility of the new method in practical application.

scholarly journals CONSIDERATION ON FRICTION COEFFICIENT FOR SEA BOTTOM

1976 ◽  
Vol 1 (15) ◽  
pp. 33
Author(s):  
Toru Sawaragi ◽  
Koichiro Iwata ◽  
Masayoshi Kubo
Keyword(s):  
Friction Coefficient ◽  
Bottom Friction ◽  
Friction Coefficients ◽  
Sand Ripple ◽  
Effective Factor ◽  
Wave Deformation ◽  
Sea Bottom ◽  
Progressive Waves ◽  
New Formula ◽  
Movable Bed

A bottom friction is an effective factor which will prove the deformation of progressive waves in shallow water, and many investigators have obtained the friction coefficients from field observations. However, they have not considered the effect of turbulent loss due to sand ripple at a sea bottom. The authors, first of all, study on the friction coefficient for artificial fixed ripple by using the boundary layer theory of rough turbulence, and a new formula on the friction coefficient is proposed. The proposed friction coefficients are compared with Zhukovets' experimental results which were performed on a movable bed, and it is found that the theoretical friction coefficients for artificial fixed ripple have to be modified in order to apply for the natural beach. Lastly, the wave deformation due to the bottom friction on the movable bed is calculated by the modified friction coefficient and the effect of bottom friction on the wave deformation is discussed.

scholarly journals HURRICANE IKE (2008) NEARSHORE WAVES: SIMULATIONS AND MEASUREMENTS

2011 ◽  
Vol 1 (32) ◽  
pp. 31
Author(s):  
Christopher J. Bender ◽  
Jane M. Smith ◽  
Andrew Kennedy
Keyword(s):  
Gulf Coast ◽  
Open Water ◽  
Bottom Friction ◽  
Hurricane Ike ◽  
Friction Coefficients ◽  
Wave Data ◽  
Level Data ◽  
Water Level Data ◽  
Extensive Damage ◽  
Good Agreement

Hurricane Ike (2008) caused extensive damage and many deaths across portions of the Caribbean and along the coasts of Texas and Louisiana. After reaching peak intensity over the open waters of the Atlantic Ocean, Hurricane Ike, with its associated storm surge, then caused extensive damage across parts of the northwestern Gulf Coast when it made landfall in the late hours of September 12th along the upper Texas coast at the upper end of Category 2 intensity. An extensive instrumentation effort allowed the collection of both nearshore and inland wave and water level data as Hurricane Ike passed by the Louisiana and Texas coasts. This paper presents the results of a validation effort for the STWAVE model and the bottom friction coefficients applied in the model with comparisons to the Hurricane Ike measured wave data. STWAVE model results indicate good agreement with the measured nearshore wave data for an open water Manning ‘n’ bottom friction coefficient equal to 0.03 s/m0.33. STWAVE model results indicate good agreement with the measured inshore wave data with Manning ‘n’ bottom friction coefficients equal to values derived from land classification data and applied in the ADCIRC model.

scholarly journals Estimation of Bottom Friction Coefficients Based on an Isopycnic-Coordinate Internal Tidal Model with Adjoint Method

2013 ◽  
Vol 2013 ◽  
pp. 1-11
Author(s):  
Yanqiu Gao ◽  
Anzhou Cao ◽  
Haibo Chen ◽  
Xianqing Lv
Keyword(s):  
Adjoint Method ◽  
Bottom Friction ◽  
Conical Surface ◽  
Friction Coefficients ◽  
Tidal Model ◽  
Good Ability ◽  
Point Scheme ◽  
Group 3 ◽  
Group 2 ◽  
Spatially Varying

Based on an isopycnic-coordinate internal tidal model with the adjoint method, three groups of ideal experiments are carried out in order to investigate the estimation of spatially varying bottom friction coefficients (BFCs). In group 1, five values of distance between independent points (DIP) are used to invert the BFCs with the distribution of conical surface. Results show that the BFCs can be inverted successfully with independent point scheme and the strategy with a DIP of 50′ can yield the best results. In group 2, five values of interpolation radius (IR) are used to invert the BFCs with the distribution of conical surface. Results show that the strategy with an IR of 1.9 times of DIP can yield the best results. Based on the results of the first two groups, group 3 adopts the optimal DIP and IR to estimate 4 kinds of spatially varying BFCs. The results indicate that the isopycnic-coordinate internal tidal model with the adjoint method has a good ability to estimate the spatially varying BFCs; the inversion results of the BFCs with the distribution of revolution paraboloid are better than those with the distribution of conical surface.

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

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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