Two-dimensional distribution of streamwise velocity in open channel flow using maximum entropy principle: Incorporation of additional constraints based on conservation laws

2020 ◽  
Vol 361 ◽  
pp. 112738 ◽  
Author(s):  
Manotosh Kumbhakar ◽  
Koeli Ghoshal ◽  
Vijay P. Singh
Keyword(s):  
Conservation Laws ◽  
Channel Flow ◽  
Open Channel ◽  
Maximum Entropy Principle ◽  
Open Channel Flow ◽  
Streamwise Velocity ◽  
Two Dimensional ◽  
Entropy Principle ◽  
Dimensional Distribution ◽  
Additional Constraints

Transverse Distribution of the Streamwise Velocity for the Open-channel Flow With Floating Vegetated Islands

2021 ◽  
Author(s):  
Xuecheng Fu ◽  
Feifei Wang ◽  
Mengyang Liu ◽  
Wenxin Huai
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Flow Characteristics ◽  
Open Channel Flow ◽  
Streamwise Velocity ◽  
Transport Efficiency ◽  
Transverse Distribution ◽  
Floating Vegetation ◽  
Shear Turbulence ◽  
Field Disturbance

Abstract Floating vegetation islands (FVIs) have been widely utilized in various river ecological restoration projects due to their ability to purify pollutants. FVIs float at the surface of shallow pools with their roots unanchored in the sediment. Biofilm formed by roots under islands filters nutrients and particles in the water flowing through it. Flow field disturbance will occur and transverse distribution of flow velocity will change due to the existence of FVIs. Transport efficiency of suspended solids, nutrients, and pollutants will also be altered. A modified analytical model that considers effects of boundary friction, drag force of vegetation, transverse shear turbulence, and secondary flow is established to predict transverse variation of depth-averaged streamwise velocity for the open-channel flow with FVIs using Shiono and Knight method. The simulation results with suitable boundary conditions successfully predicted lateral profile of the depth-averaged streamwise velocity compared with the experimental results of symmetrical and unsymmetrical arrangements of FVIs. Hence, the presented model can provide guidance for investigating flow characteristics of rivers with FVIs.

Lagrangian approach to time-dependent laminar dispersion in rectangular conduits. Part 1. Two-dimensional flows

1988 ◽  
Vol 190 ◽  
pp. 201-215 ◽  
Author(s):  
Shimon Haber ◽  
Roberto Mauri
Keyword(s):  
Channel Flow ◽  
Poiseuille Flow ◽  
Open Channel ◽  
Molecular Diffusion ◽  
Dispersion Coefficient ◽  
Brownian Particle ◽  
Open Channel Flow ◽  
Taylor Dispersion ◽  
Time Dependent ◽  
Two Dimensional

Time-dependent mean velocities and dispersion coefficients are evaluated for a general two-dimensional laminar flow. A Lagrangian method is adopted by which a Brownian particle is traced in an artificially restructured velocity field. Asymptotic expressions for short, medium and long periods of time are obtained for Couette flow, plane Poiseuille flow and open-channel flow over an inclined flat surface. A new formula is suggested by which the Taylor dispersion coefficient can be evaluated from purely kinematical considerations. Within an error of less than one percent, over the entire time domain and for various flow fields, a very simple analytical expression is derived for the time-dependent dispersion coefficient \[ \tilde{D}(\tau) = D + D^T\left(1-\frac{1-{\rm e}^{-\alpha\tau}}{a\tau}\right), \] where D is the molecular diffusion coefficient, DT denotes the Taylor dispersion coefficient, τ stands for the non-dimensional time π2Dt/Y/, Y is the distance between walls and a = (N + 1)2 is an integer which is determined by the number of symmetry planes N that the flow field possesses. For Couette and open-channel flow there are no planes of symmetry and a = 1; for Poiseuille flow there is one plane of symmetry and a = 4.

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