Nearfield of parametric transmission with finite-amplitude primary beams: Comparison between theoretical and experimental results

2000 ◽  
Author(s):  
Jacques Marchal
Keyword(s):  
Finite Amplitude ◽  
Experimental Results

The evolution of a localized vortex disturbance in external shear flows. Part 1. Theoretical considerations and preliminary experimental results

1995 ◽  
Vol 289 ◽  
pp. 159-177 ◽  
Author(s):  
Vladimir Levinski ◽  
Jacob Cohen
Keyword(s):  
Boundary Layers ◽  
Shear Flows ◽  
Flow Direction ◽  
Linear Equations ◽  
Three Dimensional ◽  
Finite Amplitude ◽  
Experimental Results ◽  
Instability Criterion ◽  
Hairpin Vortices ◽  
Plane Normal

The evolution of a finite-amplitude three-dimensional localized disturbance embedded in external shear flows is addressed. Using the fluid impulse integral as a characteristic of such a disturbance, the Euler vorticity equation is integrated analytically, and a system of linear equations describing the temporal evolution of the three components of the fluid impulse is obtained. Analysis of this system of equations shows that inviscid plane parallel flows as well as high Reynolds number two-dimensional boundary layers are always unstable to small localized disturbances, a typical dimension of which is much smaller than a dimensional length scale corresponding to an O(1) change of the external velocity. Since the integral character of the fluid impulse is insensitive to the details of the flow, universal properties are obtained. The analysis predicts that the growing vortex disturbance will be inclined at 45° to the external flow direction, in a plane normal to the transverse axis. This prediction agrees with previous experimental observations concerning the growth of hairpin vortices in laminar and turbulent boundary layers. In order to demonstrate the potential of this approach, it is applied to Taylor-Couette flow, which has additional dynamical effects owing to rotation. Accordingly, a new instability criterion associated with three-dimensional localized disturbances is found. The validity of this criterion is supported by our experimental results.

Dynamical Modeling of Deepwater-Type Cylindrical Tuned Liquid Damper With a Submerged Net

1999 ◽  
Vol 122 (1) ◽  
pp. 96-104 ◽  
Author(s):  
Shigehiko Kaneko ◽  
Yasuo Mizota
Keyword(s):  
Wave Theory ◽  
Finite Amplitude ◽  
Hydrodynamic Forces ◽  
Experimental Results ◽  
Shaking Table ◽  
Cylindrical Tank ◽  
Tuned Liquid Damper ◽  
Amplitude Wave ◽  
Modeling Methodology ◽  
Liquid Depth

An analytical model for describing the effectiveness of a deepwater-type cylindrical tuned liquid damper (TLD) with a submerged net for suppressing horizontal vibration of structures is first proposed. In this study, we performed calculations to estimate the effectiveness of a deepwater-type cylindrical TLD based on a proposed dynamical model and compared with experimental results obtained by shaking table experiments and free oscillation tests. In particular, the effect of hydraulic resistance produced by a submerged net and the liquid depth ratio (the ratio of the liquid depth to the diameter of the cylindrical tank) are examined intensively. In the analysis, employing finite amplitude wave theory and Galerkin method in the case of cylindrical tank, we obtained hydrodynamic forces and the free surface elevations. Then, combining the hydrodynamic forces with the equation of motion of the structure, damped transient responses were calculated. The calculated results thus obtained were compared with the experimental results, by which the validity of the modeling methodology was confirmed. [S0094-9930(00)00101-3]

The horizontal scale of rotating convection in the geostrophic regime

1997 ◽  
Vol 333 ◽  
pp. 85-95 ◽  
Author(s):  
SATOSHI SAKAI
Keyword(s):  
Rayleigh Number ◽  
Thermal Boundary Layer ◽  
Laboratory Experiments ◽  
Ekman Layer ◽  
Finite Amplitude ◽  
Experimental Results ◽  
Working Fluid ◽  
Horizontal Scale ◽  
Rigid Boundary ◽  
Rotating Convection

The horizontal scale of rotating convection with rigid boundary conditions is studied. The range of Rayleigh number concerned is moderate, i.e. large enough to induce a finite-amplitude convection but small enough so that the geostrophic processes are significant.On considering an experimental law of the Nusselt number and some constraints of elemental geostrophic processes, the horizontal scale of the convection can be estimated. This estimation strongly depends on the ratio between the thicknesses of the Ekman layer and the thermal boundary layer, and does not depend monotonically on the Rayleigh number. This dependency is compatible with the experimental results of Rossby (1969).The estimated horizontal scale was checked by laboratory experiments. The horizontal temperature distribution was visualized by thermal liquid-crystal capsules dispersed in the working fluid. The horizontal scale was measured by counting vortices. The experimental results agree fairly well with the estimated scale.

scholarly journals WAVE SHOALING CALCULATED FROM COKELET'S THEORY

1980 ◽  
Vol 1 (17) ◽  
pp. 6
Author(s):  
T. Sakai ◽  
J.A. Battjes
Keyword(s):  
Experimental Data ◽  
Linear Theory ◽  
Wave Height ◽  
Gravity Waves ◽  
Finite Amplitude ◽  
Experimental Results ◽  
Two Dimensional ◽  
Amplitude Wave ◽  
Non Linear ◽  
Wave Shoaling

Cokelet's numerical non-linear theory for progressive, periodic gravity waves is applied to the two-dimensional shoaling of finite amplitude waves on a beach up to breaking. The shoaling curves so obtained are compared with existing shoaling curves calculated from different finite amplitude wave theories, and with existing experimental data. It was found that the shoaling curves calculated from Cokelet's theory predict higher wave height ratios than other curves. The agreement between the present curves and the experimental results is good except near the breakpoint, where the wave height of the present curves is larger than the experimental wave height.

Diagnostics of Gold Laser Plasmas

1988 ◽  
Vol 102 ◽  
pp. 357-360
Author(s):  
J.C. Gauthier ◽  
J.P. Geindre ◽  
P. Monier ◽  
C. Chenais-Popovics ◽  
N. Tragin ◽  
...  
Keyword(s):  
Experimental Results ◽  
Pure Gold ◽  
Electronic Temperature ◽  
X Ray ◽  
Laser Plasmas ◽  
Collisional Radiative Model ◽  
Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

A new dissociation mode for dislocations in silicon

1978 ◽  
Vol 36 (1) ◽  
pp. 346-347
Author(s):  
A. Ourmazd ◽  
G.R. Booker ◽  
C.J. Humphreys
Keyword(s):  
Detailed Examination ◽  
Experimental Results ◽  
Dislocation Network ◽  
Weak Beam ◽  
Phosphorus Doped

A (111) phosphorus-doped Si specimen, thinned to give a TEM foil of thickness ∼ 150nm, contained a dislocation network lying on the (111) plane. The dislocation lines were along the three <211> directions and their total Burgers vectors,ḇt, were of the type , each dislocation being of edge character. TEM examination under proper weak-beam conditions seemed initially to show the standard contrast behaviour for such dislocations, indicating some dislocation segments were undissociated (contrast A), while other segments were dissociated to give two Shockley partials separated by approximately 6nm (contrast B) . A more detailed examination, however, revealed that some segments exhibited a third and anomalous contrast behaviour (contrast C), interpreted here as being due to a new dissociation not previously reported. Experimental results obtained for a dislocation along [211] with for the six <220> type reflections using (g,5g) weak-beam conditions are summarised in the table below, together with the relevant values.

Multislice calculations of RHEED patterns from vicinal Si (001)

1993 ◽  
Vol 51 ◽  
pp. 1000-1001
Author(s):  
Scott Lordi
Keyword(s):  
Misorientation Angle ◽  
Incident Angle ◽  
Incident Beam ◽  
Experimental Results ◽  
Bragg Condition ◽  
Vicinal Surfaces ◽  
Kinematic Theory ◽  
Step Edges

Vicinal Si (001) surfaces are interesting because they are good substrates for the growth of III-V semiconductors. Spots in RHEED patterns from vicinal surfaces are split due to scattering from ordered step arrays and this splitting can be used to determine the misorientation angle, using kinematic arguments. Kinematic theory is generally regarded to be inadequate for the calculation of RHEED intensities; however, only a few dynamical RHEED simulations have been attempted for vicinal surfaces. The multislice formulation of Cowley and Moodie with a recently developed edge patching method was used to calculate RHEED patterns from vicinal Si (001) surfaces. The calculated patterns are qualitatively similar to published experimental results and the positions of the split spots quantitatively agree with kinematic calculations.RHEED patterns were calculated for unreconstructed (bulk terminated) Si (001) surfaces misoriented towards [110] ,with an energy of 15 keV, at an incident angle of 36.63 mrad ([004] bragg condition), and a beam azimuth of [110] (perpendicular to the step edges) and the incident beam pointed down the step staircase.

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