Laser Technique Follows Turbulent Flow in Three Dimensions

Physics Today ◽  
2003 ◽  
Vol 56 (3) ◽  
pp. 18-20
Author(s):  
Charles Day
Keyword(s):  
Turbulent Flow ◽  
Three Dimensions ◽  
Laser Technique

A Theory of Lubrication With Turbulent Flow and Its Application to Slider Bearings

1960 ◽  
Vol 27 (1) ◽  
pp. 1-4 ◽  
Author(s):  
L. N. Tao
Keyword(s):  
Exact Solution ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Closed Form ◽  
Governing Equation ◽  
Reynolds Equation ◽  
Three Dimensions ◽  
Slider Bearing ◽  
Numerical Example ◽  
Special Case

The governing equation of turbulent lubrication in three dimensions, equivalent to the Reynolds equation of laminar lubrication, is derived. The problem of a slider bearing with no side leakage is then analyzed. An exact solution is found in closed form. Bearing characteristics are also established. It is found that the Reynolds number is an important parameter in the problem of turbulent lubrication. Furthermore, it is shown that the laminar lubrication may be considered as the special case of the present study. A numerical example is also included.

scholarly journals Study of frequency pattern of coherent turbulent flow over ripples using image processing with implication in river restoration

2011 ◽  
Vol 8 (4) ◽  
pp. 7845-7871
Author(s):  
A. Keshavarzi ◽  
J. Ball ◽  
H. Nabavi
Keyword(s):  
Image Processing ◽  
Turbulent Flow ◽  
Flow Structure ◽  
Sampling Rate ◽  
Three Dimensions ◽  
Image Processing Technique ◽  
Frequency Pattern ◽  
Bed Form ◽  
Bursting Events ◽  
Sediment Particles

Abstract. River channel change and bed scourings are source of major environmental problem for fish and aquatic habitat. The bed form such as ripples and dunes is the result of an interaction between turbulent flow structure and sediment particles at the bed. The structure of turbulent flow over ripples is important to understand initiation of sediment entrainment and its transport. The focus of this study is the measurement and analysis of the dominant bursting events and the flow structure over ripples in the bed of a channel. Two types of ripples with sinusoidal and triangular forms were tested in this study. The velocities of flow over the ripples were measured in three dimensions using an Acoustic Doppler Velocimeter with a sampling rate of 50 Hz. These velocities were measured at different points within the flow depth from the bed and at different longitudinal positions along the flume. A CCD camera was used to capture 1500 sequential images from the bed and to monitor sediment movement at different positions along the bed. Application of image processing technique enabled us to compute the number of entrained and deposited particles over the ripples. From a quadrant decomposition of instantaneous velocity fluctuations close to the bed, it was found that bursting events downstream of the second ripple, in Quadrants 1 and 3, were dominant whereas upstream of the ripple, Quadrants 2 and 4 were dominant. More importantly consideration of these results indicates that the normalized occurrence probabilities of sweep events are in phase with the bed forms whereas those of ejection event are out of phase with the bed form. Therefore entrainment would be expected to occur upstream and deposition occurs downstream of the ripple. These expectations were confirmed by measurement of entrained and deposited sediment particles from the bed. These above information can be used in practical application for rivers where restoration is required.

scholarly journals Frequency pattern of turbulent flow and sediment entrainment over ripples using image processing

2012 ◽  
Vol 16 (1) ◽  
pp. 147-156 ◽  
Author(s):  
A. Keshavarzi ◽  
J. Ball ◽  
H. Nabavi
Keyword(s):  
Image Processing ◽  
Turbulent Flow ◽  
Flow Structure ◽  
Sampling Rate ◽  
Three Dimensions ◽  
Image Processing Technique ◽  
Bed Form ◽  
Bursting Events ◽  
Sediment Particles ◽  
Sediment Entrainment

Abstract. River channel change and bed scourings are source of major environmental problem for fish and aquatic habitat. The bed form such as ripples and dunes is the result of an interaction between turbulent flow structure and sediment particles at the bed. The structure of turbulent flow over ripples is important to understand initiation of sediment entrainment and its transport. The focus of this study is the measurement and analysis of the dominant bursting events and the flow structure over ripples in the bed of a channel. Two types of ripples with sinusoidal and triangular forms were tested in this study. The velocities of flow over the ripples were measured in three dimensions using an Acoustic Doppler Velocimeter with a sampling rate of 50 Hz. These velocities were measured at different points within the flow depth from the bed and at different longitudinal positions along the flume. A CCD camera was used to capture 1500 sequential images from the bed and to monitor sediment movement at different positions along the bed. Application of image processing technique enabled us to compute the number of entrained and deposited particles over the ripples. From a quadrant decomposition of instantaneous velocity fluctuations close to the bed, it was found that bursting events downstream of the second ripple, in Quadrants 1 and 3, were dominant whereas upstream of the ripple, Quadrants 2 and 4 were dominant. More importantly consideration of these results indicates that the normalized occurrence probabilities of sweep events along the channel are in phase with the bed forms whereas those of ejection events are out of phase with the bed form. Therefore entrainment would be expected to occur upstream and deposition occurs downstream of the ripple. These expectations were confirmed by measurement of entrained and deposited sediment particles from the bed. These above information can be used in practical application for rivers where restoration is required.

Investigation of Conduit Flow Past Corrugated Structures Using Large Eddy Simulations

2019 ◽  
Author(s):  
Sushrut Kumar ◽  
Ujjwal Suri ◽  
Paras Sachdeva ◽  
Raj Kumar Singh
Keyword(s):  
Turbulent Flow ◽  
Velocity Component ◽  
Large Eddy Simulations ◽  
Three Dimensions ◽  
Scale Model ◽  
Particle Injection ◽  
Cross Sectional ◽  
Flow Past ◽  
Subsequent Decrease ◽  
Large Eddy

Abstract The present paper studies the characteristics of a fully turbulent flow of water through a conduit by use of corrugated structures. Methodologies including rough-ribbed walls and particle injection have been utilized for turbulence attenuation in the past. Screens and corrugations are yet another effective tools for reducing turbulence. The proposed investigation focuses on the application of square and hexagonal cross-sectional corrugations which are introduced in the flow for turbulence attenuation inside rectangular conduits. Large Eddy Simulations in three dimensions were performed with OpenFOAM using a pressure-implicit solver and the standard Smagorinsky subgrid-scale model. Dampening of the spanwise velocity component and a relative increase in streamwise velocity component downstream of the corrugation was observed. The power spectral densities (PSD) of the flow upstream and downstream of the corrugation were examined and compared. A significant decrease in turbulent flow power density was observed. Furthermore, characteristics including turbulence intensity contours and isosurfaces of the Q-criterion were visualized. The results conclusively indicate a subsequent decrease in the turbulent nature of flow past corrugated structures.

High-resolution scanning electron microscopy (HRSEM) of mitochondria from various rat tissues

1988 ◽  
Vol 46 ◽  
pp. 14-15
Author(s):  
P.J. Lea ◽  
M.J. Hollenberg
Keyword(s):  
Electron Microscopy ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rat Hepatocytes ◽  
Three Dimensions ◽  
Objective Lens ◽  
Rat Tissues ◽  
Thin Sections ◽  
Reconstruction Methods ◽  
Scanning Electron

Our current understanding of mitochondrial ultrastructure has been derived primarily from thin sections using transmission electron microscopy (TEM). This information has been extrapolated into three dimensions by artist's impressions (1) or serial sectioning techniques in combination with computer processing (2). The resolution of serial reconstruction methods is limited by section thickness whereas artist's impressions have obvious disadvantages.In contrast, the new techniques of HRSEM used in this study (3) offer the opportunity to view simultaneously both the internal and external structure of mitochondria directly in three dimensions and in detail.The tridimensional ultrastructure of mitochondria from rat hepatocytes, retinal (retinal pigment epithelium), renal (proximal convoluted tubule) and adrenal cortex cells were studied by HRSEM. The specimens were prepared by aldehyde-osmium fixation in combination with freeze cleavage followed by partial extraction of cytosol with a weak solution of osmium tetroxide (4). The specimens were examined with a Hitachi S-570 scanning electron microscope, resolution better than 30 nm, where the secondary electron detector is located in the column directly above the specimen inserted within the objective lens.

Inelastic Electron Scattering from Valence Electrons in Aluminum

1976 ◽  
Vol 34 ◽  
pp. 462-463
Author(s):  
P. E. Batson ◽  
C. H. Chen ◽  
J. Silcox
Keyword(s):  
Electron Scattering ◽  
Single Scattering ◽  
Three Dimensions ◽  
Inelastic Electron ◽  
Weak Beam ◽  
Scattering Spectrum ◽  
Valence Electrons ◽  
Diffraction Patterns ◽  
Electronic Scattering

We wish to report in this paper measurements of the inelastic scattering component due to the collective excitations (plasmons) and single particlehole excitations of the valence electrons in Al. Such scattering contributes to the diffuse electronic scattering seen in electron diffraction patterns and has recently been considered of significance in weak-beam images (see Gai and Howie) . A major problem in the determination of such scattering is the proper correction for multiple scattering. We outline here a procedure which we believe suitably deals with such problems and report the observed single scattering spectrum.In principle, one can use the procedure of Misell and Jones—suitably generalized to three dimensions (qx, qy and #x2206;E)--to derive single scattering profiles. However, such a computation becomes prohibitively large if applied in a brute force fashion since the quasi-elastic scattering (and associated multiple electronic scattering) extends to much larger angles than the multiple electronic scattering on its own.

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