Experimental Studies of External Hygrocysts

1980 ◽  
Vol 102 (2) ◽  
pp. 226-230 ◽  
Author(s):  
J. P. Kovac ◽  
R. T. Balmer
Keyword(s):  
Steady State ◽  
Velocity Field ◽  
Film Thickness ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Rotating Cylinder ◽  
Surface Velocity ◽  
Data Sets ◽  
Centrifugal Acceleration ◽  
Average Film Thickness

The three-dimensional banding phenomenon that occurs on the outside of single horizontal rotating cylinders covered with a liquid film was experimentally studied. Over 400 data sets from a variety of cylinders and liquids produced an emperical correlation between the number of bands formed and the rotational Reynolds, Weber, and Froude numbers. The average film thickness on the top of the rotating cylinder was found to be independent of the physical properties of the liquid and the centrifugal acceleration of the cylinder. The surface velocity measured in the crown of the bands was found to be nearly the same as that predicted by the steady state unbanded velocity field solution of Moffatt.

The quest for a three-dimensional theory of ship-wave interactions

1991 ◽  
Vol 334 (1634) ◽  
pp. 213-227 ◽  
Keyword(s):  
Steady State ◽  
Velocity Field ◽  
Water Waves ◽  
Three Dimensional ◽  
Integral Equation Method ◽  
Analytic Solutions ◽  
Boundary Integral ◽  
Ship Motions ◽  
Strip Theory ◽  
Forward Translation

The radiation and diffraction of water waves by ships can be analysed in classical terms from potential theory. The linearized formulation is well studied, but robust numerical implementations have been achieved only in cases where the vessel is stationary or oscillating about a fixed mean position. Slender-body approximations have been used to rationalize and extend the strip theory of ship motions, providing analytic solutions and guidance in the development of more general numerical methods. The governing equations are reviewed, with emphasis on the interactions between the steady-state velocity field due to the ship’s forward translation and the perturbations due to its unsteady motions in waves. Recent computations based on the boundary-integral-equation method are described, and encouraging results are noted. There is growing evidence that the influence of the steady-state velocity field is important, and the degree of completeness required to account for the steady field depends on the fullness of the ship. Benchmark computations are needed to test theories and computer programs without the uncertainty inherent in experimental comparisons.

Three-dimensionality in the wake of a rapidly rotating cylinder in uniform flow

2013 ◽  
Vol 730 ◽  
pp. 379-391 ◽  
Author(s):  
A. Rao ◽  
J. S. Leontini ◽  
M. C. Thompson ◽  
K. Hourigan
Keyword(s):  
Steady State ◽  
Rotation Rate ◽  
Free Stream ◽  
Three Dimensional ◽  
Rotating Cylinder ◽  
Marginal Stability ◽  
Cylinder Surface ◽  
Rotation Rates ◽  
Centrifugal Instability ◽  
The Stability

AbstractThe flow around an isolated cylinder spinning at high rotation rates in free stream is investigated. The existence of two steady two-dimensional states is confirmed, as is the existence of a secondary mode of vortex shedding. The stability of the two steady states to three-dimensional perturbations is established using linear stability analysis. At lower rotation rates on the first steady state, two three-dimensional modes are confirmed, and their structure and curves of marginal stability as a function of rotation rate and Reynolds number are determined. One mode (named mode $E$) appears consistent with a hyperbolic instability in the wake, while the second (named mode $F$) appears to be a centrifugal instability of the flow very close to the cylinder surface. At higher rotation rates on the second steady state, a single three-dimensional mode due to centrifugal instability (named mode ${F}^{\prime } $) is found. This mode becomes increasingly difficult to excite as the rotation rate is increased.

Comparative thermal stress analysis of gasketed and non-gasketed flange joints for safe operating conditions

2009 ◽  
Vol 223 (3) ◽  
pp. 167-178 ◽  
Author(s):  
M Abid ◽  
M Iqbal ◽  
B Ullah
Keyword(s):  
Steady State ◽  
Internal Pressure ◽  
Thermal Loading ◽  
Complex Analysis ◽  
Load Capacity ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Element Analysis ◽  
Safe Operating

The performance of a flanged joint is characterized mainly by its ‘strength’ and ‘sealing capability’. A number of analytical and experimental studies have been conducted to study these characteristics under only internal pressure loading. However, with the advent of new technological trends for high temperature and high-pressure applications, an increased demand for more complex analysis is recognized. The effect of steady-state thermal loading is a well-recognized problem and makes the analysis more complex. To investigate joint strength and sealing capability under combined internal pressure and different steady-state thermal loadings, a comparative three-dimensional non-linear finite-element analysis of gasketed and non-gasketed flange joints is carried out and their behaviour is discussed. To determine the safe operating conditions or actual joint load capacity, both the flange joints are further analysed for different internal pressures and temperatures.

Flow Characteristics of a Three Dimensional Bluff Body With a Single Rotating Cylinder

2012 ◽  
Author(s):  
James R. Bell ◽  
David Burton ◽  
Damien McArthur ◽  
John Sheridan
Keyword(s):  
Bluff Body ◽  
Aerodynamic Drag ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Rotating Cylinder ◽  
The Body ◽  
Surface Velocity ◽  
Cylinder Surface ◽  
Low Velocity ◽  
Freestream Velocity

This work investigated the application of a rotating cylinder to the upper leeward edge of a three dimensional bluff body in ground proximity. Aerodynamic drag measurements, base pressure contours and wake velocity profiles were obtained in a closed jet wind tunnel for Reynolds Numbers in the range of approximately 220,000 to 660,000. The cylinder of diameter 0.1H was mounted on the upper edge of the leeward face of the body. The ratio of cylinder surface velocity to freestream velocity was varied from 0 to 2.0. A computational model of the geometry was developed and results are presented for various velocity ratios and cylinder diameters. The results of this work demonstrated that, even at low velocity ratios, the cylinder rotation has a large effect on the flow structures in the body wake region. A large downwash is observed that creates two large counter-rotating vortices and a resultant significant increase in drag. The aerodynamic drag changes are presented as a function of velocity ratio and are shown to be Reynolds Number insensitive over the range tested. Aerodynamic drag was shown to increase with increasing velocity ratio over the velocity ratio range 0.25 to 2.0.

scholarly journals Three-dimensional surface velocities of Storstrømmen glacier, Greenland, derived from radar interferometry and ice-sounding radar measurements

2003 ◽  
Vol 49 (165) ◽  
pp. 201-209 ◽  
Author(s):  
Niels Reeh ◽  
Johan Jacob Mohr ◽  
Søren Nørvang Madsen ◽  
Hans Oerter ◽  
Niels S. Gundestrup
Keyword(s):  
Steady State ◽  
Vertical Velocity ◽  
Three Dimensional ◽  
Greenland Ice Sheet ◽  
Mass Conservation ◽  
Ablation Rate ◽  
Radar Interferometry ◽  
Surface Velocity ◽  
Outlet Glacier ◽  
Dimensional Surface

AbstractNon-steady-state vertical velocities of up to 5 m a−1 exceed the vertical surface-parallel flow (SPF) components over much of the ablation area of Storstrømmen, a large outlet glacier from the East Greenland ice sheet. Neglecting a contribution to the vertical velocity of this magnitude results in substantial errors (up to 20%) also on the south–north component of horizontal velocities derived by satellite synthetic aperture radar interferometry (InSAR) measurements. In many glacier environments, the steady-state vertical velocity component required to balance the annual ablation rate is 5–10 m a−1 or more. This indicates that the SPF assumption may be problematic also for glaciers in steady state. Here we derive the three-dimensional surface velocity distribution of Storstrømmen by using the principle of mass conservation (MC) to combine InSAR measurements from ascending and descending satellite tracks with airborne ice-sounding radar measurement of ice thickness. The results are compared to InSAR velocities previously derived by using the SPF assumption, and to velocities obtained by in situ global positioning system (GPS) measurements. The velocities derived by using the MC principle are in better agreement with the GPS velocities than the previously calculated velocities derived with the SPF assumption.

Three-dimensional data-domain full traveltime inversion using a practical workflow of early arrival selection

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. U77-U86
Author(s):  
Lu Liu ◽  
Xudong Duan ◽  
Yi Luo
Keyword(s):  
Optimization Problem ◽  
Three Dimensional ◽  
Velocity Model ◽  
Surface Velocity ◽  
Data Sets ◽  
Near Surface ◽  
Arrival Times ◽  
Traveltime Inversion ◽  
Early Arrival ◽  
Crosscorrelation Function

A new method of data-domain full traveltime inversion (FTI) is proposed to estimate the near-surface velocity model using early arrivals in seismic shot gathers. Data-domain FTI is capable of generating a background velocity model from which the predicted early arrivals can kinematically match the observed ones. Such a match is measured and quantified in terms of the crosscorrelation function between the computed and observed traces. Our method aims to find an optimal estimated velocity model that minimizes the crosscorrelation computed from the selected early arrivals. The early arrivals are isolated via a sequence of operations, including the [Formula: see text]-[Formula: see text] scan, autopicking, multidomain quality control, and guide interpolation. Because windows, rather than exact arrival times, are constructed, the difficulties encountered while picking precise arrivals are reduced. In addition, the gradient of data-domain FTI is derived based on an amplitude-constrained optimization problem, which makes the gradient essentially different from that derived with the Born approximation in which no constraint is used. The constraint requires the inversion to honor traveltime information only, and it thus ignores any amplitude changes caused by velocity variations. This method is validated using 3D synthetic as well as field data sets. The results show that data-domain FTI, combined with the early arrival selection workflow, is able to generate reasonable background velocities that kinematically match the predicted early arrivals with the observed ones, and the associated depth-domain images are clearly improved.

Computer-aided methods for 3-D visualization of serial sections and thick biological specimens

1992 ◽  
Vol 50 (2) ◽  
pp. 1060-1061
Author(s):  
Mark Ellisman ◽  
Maryann Martone ◽  
Gabriel Soto ◽  
Eleizer Masliah ◽  
David Hessler ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Three Dimensional ◽  
Neuritic Plaque ◽  
Dimensional Structure ◽  
Data Sets ◽  
Molecular Physiology ◽  
Research Activities ◽  
Computer Aided ◽  
Dimensional Reconstruction

Structurally-oriented biologists examine cells, tissues, organelles and macromolecules in order to gain insight into cellular and molecular physiology by relating structure to function. The understanding of these structures can be greatly enhanced by the use of techniques for the visualization and quantitative analysis of three-dimensional structure. Three projects from current research activities will be presented in order to illustrate both the present capabilities of computer aided techniques as well as their limitations and future possibilities.The first project concerns the three-dimensional reconstruction of the neuritic plaques found in the brains of patients with Alzheimer's disease. We have developed a software package “Synu” for investigation of 3D data sets which has been used in conjunction with laser confocal light microscopy to study the structure of the neuritic plaque. Tissue sections of autopsy samples from patients with Alzheimer's disease were double-labeled for tau, a cytoskeletal marker for abnormal neurites, and synaptophysin, a marker of presynaptic terminals.

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