scholarly journals Investigation of flow structures involved in sound generation by two- and three-dimensional cavity flows

2011 ◽  
Vol 48 (1) ◽  
pp. 54-67 ◽  
Author(s):  
Philippe Druault ◽  
Xavier Gloerfelt ◽  
Thomas Mervant
Keyword(s):  
Three Dimensional ◽  
Flow Structures ◽  
Cavity Flows ◽  
Sound Generation

Three-dimensional instabilities over a rectangular open cavity: from linear stability analysis to experimentation

2014 ◽  
Vol 748 ◽  
pp. 189-220 ◽  
Author(s):  
J. de Vicente ◽  
J. Basley ◽  
F. Meseguer-Garrido ◽  
J. Soria ◽  
V. Theofilis
Keyword(s):  
Three Dimensional ◽  
Reynolds Numbers ◽  
Linear Analysis ◽  
Main Flow ◽  
Open Cavity ◽  
Flow Structures ◽  
Cavity Flows ◽  
Final State ◽  
Wave Properties ◽  
Final Expression

AbstractThree-dimensional instabilities arising in open cavity flows are responsible for complex broad-banded dynamics. Existing studies either focus on theoretical properties of ideal simplified flows or observe the final state of experimental flows. This paper aims to establish a connection between the onset of the centrifugal instabilities and their final expression within the fully saturated flow. To that end, a linear three-dimensional modal instability analysis of steady two-dimensional states developing in an open cavity of aspect ratio $L/D=2$ (length over depth) is conducted. This analysis is performed together with an experimental study in the same geometry adding spanwise endwalls. Two different Reynolds numbers are investigated through spectral analyses and modal decomposition. The physics of the flow is thoroughly described exploiting the strengths of each methodology. The main flow structures are identified and salient space and time scales are characterised. Results indicate that the structures obtained from linear analysis are mainly consistent with the fully saturated experimental flow. The analysis also brings to light the selection and alteration of certain wave properties, which could be caused by nonlinearities or the change of spanwise boundary conditions.

scholarly journals Experimental Study on Coherent Structures by Particles Suspended in Half-Zone Thermocapillary Liquid Bridges: Review

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 105
Author(s):  
Ichiro Ueno
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Wave Number ◽  
Flow Structures ◽  
Liquid Bridges ◽  
Thermocapillary Effect ◽  
Particle Accumulation ◽  
Azimuthal Wave Number ◽  
Experimental Approaches ◽  
Particle Behaviour

Coherent structures by the particles suspended in the half-zone thermocapillary liquid bridges via experimental approaches are introduced. General knowledge on the particle accumulation structures (PAS) is described, and then the spatial–temporal behaviours of the particles forming the PAS are illustrated with the results of the two- and three-dimensional particle tracking. Variations of the coherent structures as functions of the intensity of the thermocapillary effect and the particle size are introduced by focusing on the PAS of the azimuthal wave number m=3. Correlation between the particle behaviour and the ordered flow structures known as the Kolmogorov–Arnold—Moser tori is discussed. Recent works on the PAS of m=1 are briefly introduced.

Large‐Eddy Simulation of Three‐Dimensional Flow Structures Over Wave‐generated Ripples

2021 ◽  
Author(s):  
Chuang Jin ◽  
Giovanni Coco ◽  
Rafael O. Tinoco ◽  
Pallav Ranjan ◽  
Jorge San Juan ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Three Dimensional ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Eddy Simulation ◽  
Large Eddy

Flow Structures in the Tip Region for a Transonic Compressor Rotor

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Juan Du ◽  
Feng Lin ◽  
Jingyi Chen ◽  
Chaoqun Nie ◽  
Christoph Biela
Keyword(s):  
Numerical Simulations ◽  
Reference Frame ◽  
Three Dimensional ◽  
Flow Structures ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Tip Leakage Flows

Numerical simulations are carried out to investigate flow structures in the tip region for an axial transonic rotor, with careful comparisons with the experimental results. The calculated performance curve and two-dimensional (2D) flow structures observed at casing, such as the shock wave, the expansion wave around the leading edge, and the tip leakage flow at peak efficiency and near-stall points, are all captured by simulation results, which agree with the experimental data well. An in-depth analysis of three-dimensional flow structures reveals three features: (1) there exists an interface between the incoming main flow and the tip leakage flow, (2) in this rotor the tip leakage flows along the blade chord can be divided into at least two parts according to the blade loading distribution, and (3) each part plays a different role on the stall inception mechanism in the leakage flow dominated region. A model of three-dimensional flow structures of tip leakage flow is thus proposed accordingly. In the second half of this paper, the unsteady features of the tip leakage flows, which emerge at the operating points close to stall, are presented and validated with experiment observations. The numerical results in the rotor relative reference frame are first converted to the casing absolute reference frame before compared with the measurements in experiments. It is found that the main frequency components of simulation at absolute reference frame match well with those measured in the experiments. The mechanism of the unsteadiness and its significance to stability enhancement design are then discussed based on the details of the flow field obtained through numerical simulations.

Swirl Flow Investigations on the Enhancement of Heat Transfer Processes in Cyclone Cooling Ducts

2012 ◽  
Author(s):  
Florian Wassermann ◽  
Sven Grundmann ◽  
Michael Kloss ◽  
Heinz-Peter Schiffer
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Complex Structure ◽  
Three Dimensional ◽  
Swirl Flow ◽  
Flow Structures ◽  
Stable Complex ◽  
Reynolds Analogy ◽  
Transfer Processes ◽  
Cooling Ducts

Cyclone cooling is a promising method to enhance heat-transfer processes in future internal turbine-blade leading-edge cooling-ducts. The basic component of such cooling channels is the swirl generator, which induces a swirling movement of the coolant. The angular momentum generates stable, complex and three-dimensional flow structures of helical shape with alternating axial flow directions. Full three-dimensional and three-component velocity measurements using magnetic resonance velocimetry (3D3C-MRV) were conducted, with the aim to understand the complex structure of pipe flows with strong swirl. In order to mimic the effect of different installation concepts of the cyclone-cooling ducts an idealized bend-duct swirl-tube configuration with variable exit orifices has been investigated. Pronounced helical flow structures and distinct velocity zones could be found in this swirl flow. One substantial result is the identification of stationary helix-shaped streaks of high axial velocity in the direct vicinity of the wall. These findings are in good agreement with mass-transfer measurements that also show helix-shaped structures with increased mass transfer at the inner surface of the tube. According to the Reynolds analogy between heat and mass transfer, augmented heat-transfer processes in these areas are to be expected.

The eruptive regime of mass-transfer-driven Rayleigh–Marangoni convection

2016 ◽  
Vol 791 ◽  
Author(s):  
Thomas Köllner ◽  
Karin Schwarzenberger ◽  
Kerstin Eckert ◽  
Thomas Boeck
Keyword(s):  
Concentration Distribution ◽  
Marangoni Convection ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Boussinesq Equations ◽  
Navier Stokes ◽  
Flow Structures ◽  
Rayleigh Convection ◽  
Marangoni Effects ◽  
Validation Experiments

The transfer of an alcohol, 2-propanol, from an aqueous to an organic phase causes convection due to density differences (Rayleigh convection) and interfacial tension gradients (Marangoni convection). The coupling of the two types of convection leads to short-lived flow structures called eruptions, which were reported in several previous experimental studies. To unravel the mechanism underlying these patterns, three-dimensional direct numerical simulations and corresponding validation experiments were carried out and compared with each other. In the simulations, the Navier–Stokes–Boussinesq equations were solved with a plane interface that couples the two layers including solutal Marangoni effects. Our simulations show excellent agreement with the experimentally observed patterns. On this basis, the origin of the eruptions is explained by a two-step process in which Rayleigh convection continuously produces a concentration distribution that triggers an opposing Marangoni flow.

Effects of Inclination Angle of Ribs on the Flow Behavior in Rectangular Ducts

2004 ◽  
Vol 126 (4) ◽  
pp. 692-699 ◽  
Author(s):  
Xiufang Gao ◽  
Bengt Sunde´n
Keyword(s):  
Velocity Component ◽  
Flow Direction ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Streamwise Velocity ◽  
Flow Structures ◽  
Local Flow ◽  
Flow Motion ◽  
Streamwise Velocity Component

The flow behavior in rib-roughened ducts is influenced by the inclination of ribs and the effect is investigated in the present study by Particle Image Velocimetry (PIV). The local flow structures between two adjacent ribs were measured. The Reynolds number was fixed at 5800. The flow field description was based on the PIV results in planes both parallel and perpendicular to the ribbed walls at various locations. The rib angle to the main flow direction was varied as 30 deg, 45 deg, 60 deg and 90 deg. The ribs induce three dimensional flow fields. The flow separation and reattachment between adjacent ribs are clearly observed. In addition, the inclined ribs are found to alter the spanwise distribution of the streamwise velocity component. The streamwise velocity component has its highest values at the upstream end of the ribs, and decreases continuously to its lowest values at the downstream end. Strong secondary flow motion occurs over the entire duct cross section for the inclined ribs. The flow structures between two consecutive ribs show that the fluid flows along the ribs from one end of the ribs to the other end, and then turns back at the transverse center. Downwash and upwash flows are observed at the upstream end and downstream end of the ribs, respectively.

The evolution of the initial flow structures of a highly under-expanded circular jet

2019 ◽  
Vol 871 ◽  
pp. 305-331 ◽  
Author(s):  
Huan-Hao Zhang ◽  
Nadine Aubry ◽  
Zhi-Hua Chen ◽  
Wei-Tao Wu ◽  
Sha Sha
Keyword(s):  
Vortex Ring ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Structures ◽  
Secondary Vortex ◽  
Shock Cell ◽  
Initial Flow ◽  
Turbulence Transition ◽  
Circular Jets ◽  
Generation Mechanisms

The three-dimensional flow characteristics of the compressible vortex ring generated by under-expanded circular jets with two typical pressure ratios, i.e. $n=1.4$ (moderate) and 4.0 (high), are investigated numerically with the use of large-eddy simulations. Our results illustrate that these two pressure ratios correspond to different shock structures (shock cell and Mach disc, respectively) within the jet. These two typical types of flow structures and characteristics are discussed and validated with experiments, and the different generation mechanisms of the secondary vortex rings are compared. Moreover, detailed information about the evolution of the secondary vortex ring, primary vortex ring and turbulence transition features, including the radial and azimuthal modes, is investigated. The geometric features and mixing effects of the jets are also explored.

Sign in / Sign up

Export Citation Format

Share Document