scholarly journals On the evolution and form of coherent flow structures over a gravel bed: Insights from whole flow field visualization and measurement

2016 ◽  
Vol 121 (8) ◽  
pp. 1472-1493 ◽  
Author(s):  
R. J. Hardy ◽  
J. L. Best ◽  
D. R. Parsons ◽  
T. I. Marjoribanks
Keyword(s):  
Flow Field ◽  
Flow Structures ◽  
Gravel Bed ◽  
Coherent Flow Structures

Coherent flow structures in shallow gravel-bed rivers

Shallow Flows ◽  
2004 ◽  
pp. 259-266
Author(s):  
C Keylock ◽  
R Hardy ◽  
D Parsons ◽  
R Ferguson ◽  
S Lane
Keyword(s):  
Flow Structures ◽  
Gravel Bed ◽  
Coherent Flow Structures ◽  
Gravel Bed Rivers

Characterization of Coherent Flow Structures in a Swirl-Stabilized Spray Combustor

2021 ◽  
Author(s):  
Nicholas Rock ◽  
Scott D. Stouffer ◽  
Tyler H. Hendershott ◽  
Edwin Corporan ◽  
Paul Wrzesinski
Keyword(s):  
Flow Structures ◽  
Coherent Flow Structures

scholarly journals Design-Assisted of Pitching Aerofoils through Enhanced Identification of Coherent Flow Structures

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 11 ◽  
Author(s):  
Filippo Avanzi ◽  
Francesco De Vanna ◽  
Yin Ruan ◽  
Ernesto Benini
Keyword(s):  
Pressure Field ◽  
Navier Stokes ◽  
Flow Structures ◽  
Coupled Modes ◽  
Spectral Reconstruction ◽  
Sst Turbulence Model ◽  
Coherent Flow Structures ◽  
Highly Correlated ◽  
Naca 0012 ◽  
Proper Orthogonal

This study discusses a general framework to identify the unsteady features of a flow past an oscillating aerofoil in deep dynamic stall conditions. In particular, the work aims at demonstrating the advantages for the design process of the Spectral Proper Orthogonal Decomposition in accurately producing reliable reduced models of CFD systems and comparing this technique with standard snapshot-based models. Reynolds-Averaged Navier-Stokes system of equations, coupled with k−ω SST turbulence model, is used to produce the dataset, the latter consisting of a two-dimensional NACA 0012 aerofoil in the pitching motion. Modal analysis is performed on both velocity and pressure fields showing that, for vectored values, a proper tuning of the filtering process allows for better results compared to snapshot formulations and extract highly correlated coherent flow structures otherwise undetected. Wider filters, in particular, produce enhanced coherence without affecting the typical frequency response of the coupled modes. Conversely, the pressure field decomposition is drastically affected by the windowing properties. In conclusion, the low-order spectral reconstruction of the pressure field allows for an excellent prediction of aerodynamic loads. Moreover, the analysis shows that snapshot-based models better perform on the CFD values during the pitching cycle, while spectral-based methods better fit the loads’ fluctuations.

Unsteady Aerodynamics of an Aeroengine Double Swirler Lean Premixing Prevaporizing Burner

2004 ◽  
Vol 128 (1) ◽  
pp. 29-39 ◽  
Author(s):  
Edward Canepa ◽  
Pasquale Di Martino ◽  
Piergiorgio Formosa ◽  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Flow Field ◽  
Reynolds Stress ◽  
Large Scale ◽  
Unsteady Aerodynamics ◽  
Scale Model ◽  
Flow Structures ◽  
Laser Doppler Velocimeter ◽  
Formation Mechanisms ◽  
Meridional Plane ◽  
Stress Components

Lean premixing prevaporizing (LPP) burners represent a promising solution for low-emission combustion in aeroengines. Since lean premixed combustion suffers from pressure and heat release fluctuations that can be triggered by unsteady large-scale flow structures, a deep knowledge of flow structures formation mechanisms in complex swirling flows is a necessary step in suppressing combustion instabilities. The present paper describes a detailed investigation of the unsteady aerodynamics of a large-scale model of a double swirler aeroengine LPP burner at isothermal conditions. A three-dimensional (3D) laser Doppler velocimeter and an ensemble-averaging technique have been employed to obtain a detailed time-resolved description of the periodically perturbed flow field at the mixing duct exit and associated Reynolds stress and vorticity distributions. Results show a swirling annular jet with an extended region of reverse flow near to the axis. The flow is dominated by a strong periodic perturbation, which occurs in all the three components of velocity. Radial velocity fluctuations cause important periodic displacement of the jet and the inner separated region in the meridional plane. The flow, as expected, is highly turbulent. The periodic stress components have the same order of magnitude of the Reynolds stress components. As a consequence the flow-mixing process is highly enhanced. Turbulence acts on a large spectrum of fluctuation frequencies, whereas the large-scale motion influences the whole flow field in an ordered way that can be dangerous for stability in reactive conditions.

scholarly journals EFFECT OF GALLERIES ON THE WIND FLOW STRUCTURE AND POLLUTANT TRANSPORT WITHIN STREET CANYONS WITH OR WITHOUT FACADE ROUGHNESS ELEMENTS (BALCONIES)

2020 ◽  
Vol 7 (12) ◽  
pp. 45-59
Author(s):  
V. A. Karkoulias ◽  
P. E. Marazioti ◽  
D. P. Georgiou ◽  
E. A. Maraziotis
Keyword(s):  
Flow Field ◽  
Concentration Distribution ◽  
Cfd Simulation ◽  
Field Structure ◽  
Flow Structures ◽  
Street Canyons ◽  
Ansys Fluent ◽  
Roughness Elements ◽  
Computational Fluid Dynamics Cfd ◽  
The Vertical Distribution

This paper investigates how the structure of the flow field and the vertical distribution of the pollutant concentration near the wall facades of street canyons are affected by the presence of some elements such as street level galleries. Numerical results are presented for various gallery geometries in combination with facade roughness elements (balconies) for a canyon of an aspect ratio equal to h/w=2.33. The results were obtained by a Computational Fluid Dynamics (CFD) simulation employing the ANSYS-FLUENT suite that incorporated the k-e turbulent (RNG) model. The simulation generated several flow structures inside the canyon (mainly vortices), whose characteristic properties (e.g. number, strength and size) are discussed in terms of the effect of the galleries on the flow field structure and the roughness generated by the building façade balconies. The results indicate a significant influence on both the flow field structure and the mass concentration distribution of the polluting particles.

Magnetohydrodynamic effects on flow structures and heat transfer over two cylinders wrapped with a porous layer in side

2016 ◽  
Vol 26 (5) ◽  
pp. 1416-1432 ◽  
Author(s):  
Saman Rashidi ◽  
Javad Abolfazli Esfahani ◽  
Mohammad Sadegh Valipour ◽  
Masoud Bovand ◽  
Ioan Pop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Flow Field ◽  
Porous Layer ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Flow Structures ◽  
Content Type ◽  
The Magnetic Field

Purpose – The analysis of the flow field and heat transfer around a tube row or tube banks wrapped with porous layer have many related engineering applications. Examples include the reactor safety analysis, combustion, compact heat exchangers, solar power collectors, high-performance insulation for buildings and many another applications. The purpose of this paper is to perform a numerical study on flows passing through two circular cylinders in side-by-side arrangement wrapped with a porous layer under the influence of a magnetic field. The authors focus the attention to the effects of magnetic field, Darcy number and pitch ratio on the mechanism of convection heat transfer and flow structures. Design/methodology/approach – The Darcy-Brinkman-Forchheimer model for simulating the flow in porous medium along with the Maxwell equations for providing the coupling between the flow field and the magnetic field have been used. Equations with the relevant boundary conditions are numerically solved using a finite volume approach. In this study, Stuart and Darcy numbers are varied within the range of 0 < N < 3 and 1e-6 < Da < 1e-2, respectively, and Reynolds and Prandtl numbers are equal to Re=100 and Pr=0.71, respectively. Findings – The results show that the drag coefficient decreases for N < 0.6 and increases for N > 0.6. Also, the effect of magnetic field is negligible in the gap between two cylinders because the magnetic field for two cylinders counteracts each other in these regions. Originality/value – To the authors knowledge, in the open literature, flow passing over two circular cylinders in side-by-side arrangement wrapped with a porous layer has been rarely investigated especially under the influence of a magnetic field.

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