scholarly journals A complex-valued first integral of Navier-Stokes equations: Unsteady Couette flow in a corrugated channel system

2017 ◽  
Vol 58 (4) ◽  
pp. 043102 ◽  
Author(s):  
F. Marner ◽  
P. H. Gaskell ◽  
M. Scholle
Keyword(s):  
Couette Flow ◽  
Stokes Equations ◽  
First Integral ◽  
Navier Stokes ◽  
Channel System ◽  
Navier Stokes Equations ◽  
Corrugated Channel ◽  
Unsteady Couette Flow ◽  
Complex Valued

scholarly journals A doubly localized equilibrium solution of plane Couette flow

2014 ◽  
Vol 750 ◽  
Author(s):  
E. Brand ◽  
J. F. Gibson
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
Equilibrium Solution ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Edge States ◽  
Plane Couette Flow ◽  
Turbulent Spot ◽  
Navier Stokes Equations ◽  
Exponential Decay Rate

AbstractWe present an equilibrium solution of plane Couette flow that is exponentially localized in both the spanwise and streamwise directions. The solution is similar in size and structure to previously computed turbulent spots and localized, chaotically wandering edge states of plane Couette flow. A linear analysis of dominant terms in the Navier–Stokes equations shows how the exponential decay rate and the wall-normal overhang profile of the streamwise tails are governed by the Reynolds number and the dominant spanwise wavenumber. Perturbations of the solution along its leading eigenfunctions cause rapid disruption of the interior roll-streak structure and formation of a turbulent spot, whose growth or decay depends on the Reynolds number and the choice of perturbation.

scholarly journals Doubly localized states in plane Couette flow

2014 ◽  
Vol 758 ◽  
pp. 1-4 ◽  
Author(s):  
Bruno Eckhardt
Keyword(s):  
Couette Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Linear Instability ◽  
Localized States ◽  
Transition To Turbulence ◽  
Navier Stokes ◽  
Plane Couette Flow ◽  
Navier Stokes Equation ◽  
Navier Stokes Equations

AbstractMuch of our understanding of the transition to turbulence in flows without a linear instability came with the discovery and characterization of fully three-dimensional solutions to the Navier–Stokes equation. The first examples in plane Couette flow were periodic in both spanwise and streamwise directions, and could explain the transitions in small domains only. The presence of localized turbulent spots in larger domains, the spatiotemporal decoherence on larger scales and the ability to trigger turbulence with pointwise perturbations require solutions that are localized in both directions, like the one presented by Brand & Gibson (J. Fluid Mech., vol. 750, 2014, R3). They describe a steady solution of the Navier–Stokes equations and characterize in unprecedented detail, including an analytic computation of its localization properties. The study opens up new ways to describe localized turbulent patches.

scholarly journals Analytic and Numerical Solutions of Couette Flow Problem: A Comparative Study

2017 ◽  
Vol 12 (1) ◽  
pp. 105-113
Author(s):  
Dhak Bahadur Thapa ◽  
Kedar Nath Uprety
Keyword(s):  
Differential Equation ◽  
Couette Flow ◽  
Numerical Solutions ◽  
Flow Problem ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Parabolic Partial Differential Equation ◽  
Navier Stokes Equations ◽  
One Dimensional ◽  
Nicolson Scheme

In this work, an incompressible viscous Couette flow is derived by simplifying the Navier-Stokes equations and the resulting one dimensional linear parabolic partial differential equation is solved numerically employing a second order finit difference Crank-Nicolson scheme. The numerical solution and the exact solution are presented graphically.Journal of the Institute of Engineering, 2016, 12(1): 105-113

Numerical experiments on time-dependent rotational Couette flow

1973 ◽  
Vol 59 (1) ◽  
pp. 77-95 ◽  
Author(s):  
D. C. S. Liu ◽  
C. F. Chen
Keyword(s):  
Couette Flow ◽  
Numerical Experiments ◽  
Stokes Equations ◽  
Axial Direction ◽  
Navier Stokes ◽  
Simultaneous Occurrence ◽  
Navier Stokes Equations ◽  
Finite Difference Approximations ◽  
Critical Wavelength ◽  
Explicit Finite Difference

The flow induced by impulsively starting the inner cylinder in a Couette flow apparatus is investigated by using a nonlinear analysis. Explicit finite-difference approximations are used to solve the Navier–Stokes equations for axisymmetric flows. Random small perturbations are distributed initially and periodic boundary conditions are applied in the axial direction over a length which, in general, is chosen to be the critical wavelength observed experimentally. Simultaneous occurrence of Taylor vortices is obtained at supercritical Reynolds numbers. The development of streamlines, perturbation velocity components and the kinetic energy of the perturbations is examined in detail. Many salient features of the physical flow are observed in the numerical experiments.

scholarly journals A streamwise constant model of turbulence in plane Couette flow

2010 ◽  
Vol 665 ◽  
pp. 99-119 ◽  
Author(s):  
D. F. GAYME ◽  
B. J. McKEON ◽  
A. PAPACHRISTODOULOU ◽  
B. BAMIEH ◽  
J. C. DOYLE
Keyword(s):  
Couette Flow ◽  
Small Amplitude ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Turbulent Shear ◽  
Theoretic Approach ◽  
Plane Couette Flow ◽  
Navier Stokes Equations ◽  
Turbulent Plane ◽  
3C Model

Streamwise and quasi-streamwise elongated structures have been shown to play a significant role in turbulent shear flows. We model the mean behaviour of fully turbulent plane Couette flow using a streamwise constant projection of the Navier–Stokes equations. This results in a two-dimensional three-velocity-component (2D/3C) model. We first use a steady-state version of the model to demonstrate that its nonlinear coupling provides the mathematical mechanism that shapes the turbulent velocity profile. Simulations of the 2D/3C model under small-amplitude Gaussian forcing of the cross-stream components are compared to direct numerical simulation (DNS) data. The results indicate that a streamwise constant projection of the Navier–Stokes equations captures salient features of fully turbulent plane Couette flow at low Reynolds numbers. A systems-theoretic approach is used to demonstrate the presence of large input–output amplification through the forced 2D/3C model. It is this amplification coupled with the appropriate nonlinearity that enables the 2D/3C model to generate turbulent behaviour under the small-amplitude forcing employed in this study.

scholarly journals On the self-sustained nature of large-scale motions in turbulent Couette flow

2015 ◽  
Vol 782 ◽  
pp. 515-540 ◽  
Author(s):  
Subhandu Rawat ◽  
Carlo Cossu ◽  
Yongyun Hwang ◽  
François Rincon
Keyword(s):  
Couette Flow ◽  
Turbulent Flows ◽  
Large Scale ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Buffer Layers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Steady Solutions ◽  
Smagorinsky Constant

Large-scale motions in wall-bounded turbulent flows are frequently interpreted as resulting from an aggregation process of smaller-scale structures. Here, we explore the alternative possibility that such large-scale motions are themselves self-sustained and do not draw their energy from smaller-scale turbulent motions activated in buffer layers. To this end, it is first shown that large-scale motions in turbulent Couette flow at $Re=2150$ self-sustain, even when active processes at smaller scales are artificially quenched by increasing the Smagorinsky constant $C_{s}$ in large-eddy simulations (LES). These results are in agreement with earlier results on pressure-driven turbulent channel flows. We further investigate the nature of the large-scale coherent motions by computing upper- and lower-branch nonlinear steady solutions of the filtered (LES) equations with a Newton–Krylov solver, and find that they are connected by a saddle–node bifurcation at large values of $C_{s}$. Upper-branch solutions for the filtered large-scale motions are computed for Reynolds numbers up to $Re=2187$ using specific paths in the $Re{-}C_{s}$ parameter plane and compared to large-scale coherent motions. Continuation to $C_{s}=0$ reveals that these large-scale steady solutions of the filtered equations are connected to the Nagata–Clever–Busse–Waleffe branch of steady solutions of the Navier–Stokes equations. In contrast, we find it impossible to connect the latter to buffer-layer motions through a continuation to higher Reynolds numbers in minimal flow units.

scholarly journals Exact Solution of 3D Navier–Stokes Equations

2020 ◽  
pp. 306-313
Author(s):  
Alexander V. Koptev
Keyword(s):  
Exact Solution ◽  
Fluid Flow ◽  
Incompressible Fluid ◽  
Exact Solutions ◽  
Stokes Equations ◽  
First Integral ◽  
Navier Stokes ◽  
Incompressible Fluid Flow ◽  
Navier Stokes Equations ◽  
Particular Solutions

Procedure for constructing exact solutions of 3D Navier–Stokes equations for an incompressible fluid flow is proposed. It is based on the relations representing the previously obtained first integral of the Navier–Stokes equations. A primary generator of particular solutions is proposed. It is used to obtain new classes of exact solutions

A first integral of Navier–Stokes equations and its applications

2010 ◽  
Vol 467 (2125) ◽  
pp. 127-143 ◽  
Author(s):  
Markus Scholle ◽  
André Haas ◽  
Philip H. Gaskell
Keyword(s):  
Stokes Equations ◽  
Scalar Potential ◽  
First Integral ◽  
Inviscid Flow ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Bernoulli’S Equation ◽  
Two Dimensional Flow ◽  
Laminar Shear Flow

Although it is well known that Bernoulli's equation is obtained as the first integral of Euler's equations in the absence of vorticity and that in the case of non-vanishing vorticity a first integral of them can be found using the Clebsch transformation for inviscid flow, generalization of the procedure for viscous flow has remained elusive. Accordingly, in this paper, a first integral of the Navier–Stokes equations for steady flow is constructed. In the case of a two-dimensional flow, this is made possible by formulating the governing equations in terms of complex variables and introducing a new scalar potential. Associated boundary conditions are considered, and an extension of the theory to three dimensions is proposed. The capabilities of the new approach are demonstrated by calculating a Reynolds number correction to the laminar shear flow generated in the narrow gap between a flat moving and a stationary wavy wall, as is often encountered in lubrication problems. It highlights the first integral as a suitable tool for the development of new analytical and numerical methods in fluid dynamics.

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