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Showing 1 to 20 of 34 for “"rough wall"”.
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Sound from Rough Wall Boundary Layers
Turbulent flow over a rough surface produces sound that radiates outside the near wall region. This noise source is often at a lower level than the noise created by edges and bluff body flows, but for applications with large surface area to perimeter ratios at low Mach number, this noise source can …
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Inner-outer interactions in a rough-wall turbulent boundary layer
… understanding of inner-outer interactions in rough-wall turbulent boundary layers. These interactions were recently established over smooth-wall turbulent boundary layers as modulating interactions, where the outer layer large scales amplitude and frequency modulate the near-wall small scales. …
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Mean Force Structure and Scaling of Rough-Wall Turbulent Boundary Layers
<p>The combined roughness-Reynolds number problem is explored from the perspective of ordering of terms in the mean momentum balance. Existing mean velocity and Reynolds shear stress data from zero pressure gradient, rough-wall turbulent boundary layers are used to clarify the nature of the leading …
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The Rough Wall High Reynolds Number Turbulent Boundary Layer Surface Pressure Spectrum
… have been very few studies investigating the rough wall pressure spectra under fully rough flows, which are relevant to many common engineering applications operating within this regime. This investigation uses the Virginia Tech Stability Wind Tunnel to perform experiments on a series of high …
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Experimental Investigation of Turbulent Flows at Smooth and Rough Wall-Cylinder Junctions
… the interaction between a fluid moving over a wall with an obstacle mounted on the same surface. Understanding the physics of such flows is of great interest to engineers responsible for the design of systems consisting of wall-body junctions. From aerodynamics to turbomachinery and electronics …
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The Wall Pressure Spectrum of High Reynolds Number Rough-Wall Turbulent Boundary Layers
The presence of roughness on a surface subject to high Reynolds number flows promotes the formation of a turbulent boundary layer and the generation of a fluctuating pressure field imposed on the surface. While numerous studies have investigated the wall pressure fluctuations over zero-pressure …
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Geometry-Aware Modeling of Rough-Wall Turbulence Using Reynolds-Averaged Navier-Stokes (RANS) Frameworks
Turbulent flow over rough walls is widespread in engineering systems and plays a critical role in drag prediction, energy efficiency, and transport processes in internal and external flows. Despite extensive research, the representation of roughness effects in Reynolds-Averaged Navier–Stokes (RANS) …
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An Experimental Study of Momentum and Thermal Transport in Flow Through Smooth- and Rough-Wall Microchannels
Local Nusselt number (Nu) for smooth-wall laminar flow in the range 200 ≤ Re ≤ Recr agree well with macroscale predictions in both the thermally-developing and -developed regimes With increasing roughness, while an enhancement in local Nu is noted in the thermally-developing regime, no …
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Structure of 2-D and 3-D Turbulent Boundary Layers with Sparsely Distributed Roughness Elements
… were carried out to understand and describe the rough-wall flow structure. The measurements include mean velocities, turbulence quantities (Reynolds stresses and triple products), skin friction, surface pressure and oil flow visualizations in 2-D and 3-D rough-wall flows for Reynolds numbers, …
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Open channel turbulent boundary layers and wall jets on rough surfaces
… by the turbulence structure in the near-wall region. Although many flows of practical interest occur on rough surfaces, our understanding and ability to predict rough wall turbulent flows lags far behind the corresponding technology for smooth surfaces. This provides reasonable grounds …
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Effects of Spacing and Geometry of Distributed Roughness Elements on a Two-Dimensional Turbulent Boundary Layer
… thesis is a study of the effects of distributed roughness elements on a two-dimensional turbulent boundary layer. Measurements were taken on a total of ten rough wall configurations: four involving Gaussian spikes, and six with circular cylindrical posts. Rough wall flows are particularly suited …
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Experimental Investigation of Highly Irregular Roughness Effects in Wall Turbulence
… surface is contrasted with that over the smooth wall, both within and outside the roughness sublayer, to further assess the possibility of structural modifications due to roughness. Hairpin vortex packets, commonly observed in smooth-wall turbulence, are observed often in the outer layer of the …
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The Resolution and Structure of High Reynolds Number Turbulent Boundary Layers Over Rough and Smooth Walls in Pressure Gradient
… fields of high Reynolds number, turbulent, wall boundary layers in non-equilibrium pressure gradients are experimentally investigated. Experiments in two wall configurations were performed; one with a hydrodynamically smooth test wall composed of flat aluminum panels, and the other with a …
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Amplitude modulation of velocity and wall shear stress in turbulent channel flow with hemispherical roughness
"Near-wall turbulence cycles tend to be self-sustained in low Reynolds number wall-bounded turbulent flows. However, large-scale structures that reside in the outer region of the flow grow more energetic as Reynolds number increases and impart strong ""footprints"" on the near-wall turbulence. In …
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Effects of surface roughness on the flow characteristics in a turbulent boundary layer
… boundary layers on aerodynamically smooth walls has been clarified over the last decade or so. However, the dynamics of turbulent boundary layers over rough surfaces is much less well known. Nevertheless, there are many industrial and environmental flow applications that require …
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The Effects of Pressure Gradient and Roughness on Pressure Fluctuations Beneath High Reynolds Number Boundary Layers
… turbulent boundary layers over both smooth and rough surfaces subjected to a systematically defined family of continually varying, bi-directional pressure gradient distributions are investigated in both wind tunnel experiments and steady 2D and 3D Reynolds Averaged-Navier-Stokes (RANS) …
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Wall Jet Boundary Layer Flows Over Smooth and Rough Surfaces
… pressure of a plane, turbulent, two-dimensional wall jet flow into still air over smooth and rough surfaces has been investigated in a recently constructed wall jet wind tunnel testing facility. The facility has been shown to produce a wall jet flow with Reynolds numbers based on the momentum …
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Spectral Energy Dynamics and Wavevector Resonance in a Weakly Nonlinear Chaotic Elastodynamic Billiard
… performed for an ensemble of two-dimensional rough-wall billiards. The frequency profile of the mode-coupling strength is verified.
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Fluid Dynamics and Surface Pressure Fluctuations of Two-Dimensional Turbulent Boundary Layers Over Densely Distributed Surface Roughness
… of three-dimensional densely distributed surface roughness. A 3-velocity component laser Doppler velocimeter was used to measure instantaneous velocities. These measurements permitted an independent estimate of skin friction on the surfaces using a momentum balance approach, and the validity of …
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Roughness Effects on Super Structures in Turbulent Boundary Layer Flows
This study investigates the influence of wall roughness on large-scale structures within turbulent boundary layers, using wall-parallel stereoscopic Particle Image Velocimetry (PIV) at a Reynolds number of 1.3 × 106m−1. The data was collected at a distance of = 2.8 from the wall under adverse = …
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