Search results for "Channel flow"

Turbulence structure and coherent motion in a straight laboratory flume

2012

Evolution of coherent turbulent structures and relation with bed-forms formation in a straight flume

2008

The present paper describes some results of experimental work carried out in a rectilinear flume to investigate the interactions between flow turbulence and sediment motion. The analysis is conducted through the comparison between the periodicity of turbulent structures evolving along the channel and the wavelength of bed forms (alternate bars) forming on the bed. The occurrence of turbulent events (inward interaction, ejection, sweep and burst) has been verified through the conditioned quadrant analysis. The quantitative information about the spatial and temporal scale of the events has been obtained through the space-time correlations of the conditioned data. The analysis essentially high…

Turbulent Flow Structures For Different Roughness Conditions of Channel Walls: Results of experimental

2012

Experimental investigation of the evolution of secondary motion in a large amplitude meandering flume

2008

The development of secondary motion along open-channel bends strongly affects the bed deformation and the channel plane evolution. Recent experimental results obtained at the apex section of a large amplitude meandering flume have confirmed that besides the main central circulation cell a second counter-rotating cell develops near the free surface of the outer bank. In the light of such results, in this work the attention is devoted to the analysis of the evolution of the observed secondary motion along whole bend. The analysis is conducted on the basis of flow velocity data collected in five transversal sections along half wave-length of the same large amplitude meandering flume.

Unsteady turbulence in plane channel flow

2011

Abstract Direct numerical simulations were conducted for oscillating flow with zero time mean (reciprocating flow) in a plane channel subject to a harmonic forcing term of varying amplitude and frequency. The results confirmed the existence of four flow regimes (laminar, “disturbed laminar”, intermittently turbulent, and fully turbulent) depending on the above parameters. The flow behaviour was found to depend on the complex interplay of mean and turbulence quantities, as described by the closed loop formed by the streamwise Reynolds-averaged momentum equation in conjunction with the exact transport equations for the turbulent (Reynolds) stresses. A crucial role in this loop appeared to be …

Discussion of "preliminary Study of Surface Hydraulic Jumps" by S. Ahmed, Y. Ye, H. Liu, and N. Rajaratnam

2020

In this paper the results of Preliminary Study of Surface Hydraulic Jumps” by S. Ahmed, Y. Ye, H. Liu, and N. Rajaratnam are discussed

LES of the flow around two cylinders in tandem

2008

The flow around an arrangement of two-in-tandem cylinders exhibits a remarkably\ud complex behaviour that is of interest for many engineering problems, such as environmental\ud flows or structural design. In the present paper, a Large Eddy Simulation using a staggered\ud Cartesian grid has been performed for the flow around two-in-tandem cylinders of diameter\ud D=20mm and height H=50mm submerged in an open channel with height h=60 mm. The two\ud axes have a streamwise spacing of 2D. The Reynolds number is 1500, based on the cylinder\ud diameter and the free-stream velocity u�. The results obtained show that no vortex shedding\ud occurs in the gap between the two cylinders where the separat…

Numerical Study of Forced MHD Convection Flow and Temperature Around Periodically Placed Cylinders

2016

In this paper we consider 2D stationary boundary value problems for the system of magnetohydrodynamic (MHD) equations and the heat transfer equation. The viscous electrically conducting incompressible liquid moves between infinite cylinders with square or round sections placed periodically. We also consider similar 2D MHD channel flow with periodically placed obstacles on the channel walls. We analyse the 2D forced and free MHD convection flow and temperature around cylinders and obstacles in homogeneous external magnetic field. The cylinders, obstacles and walls of the channel with constant temperature are heated. The distributions of electromagnetic fields, forces, velocity and temperatur…

Particle-Laden Turbulent Channel Flow with Wall-Roughness

2015

Turbulent flows transporting a dispersed-phase are found in many environmental applications and engineering devices. Particle-laden flows are characterized by several peculiar phenomenologies such as preferential particle concentration and turbulence modulation of the carrier-phase due to the presence of the inertial particles [1].

Role of secondary circulation on bank erosion in a large amplitude meandering laboratory channel

2009

This paper reports peculiar results of experimental investigation on the evolution of flow secondary circulation motion along a meander wave. The experiments have been conducted in a large amplitude meandering laboratory channel for two values of the width-to-depth ratio. Attention is focalised on how secondary motion affects the bank shear stress distribution, influencing the bank stability. The analysis essentially highlights that, especially for small width-to-depth ratio, as the channel curvature increases besides the classical central-region secondary circulation cell a counter-rotating circulation cell forms in the outer-bank region. Such counterrotating circulation cell allows to obt…