Laboratory observations of bedforms under directional irregular waves

1993 ◽  
Vol 20 (4) ◽  
pp. 550-563 ◽  
Author(s):  
D. H. Willis ◽  
M. H. Davies ◽  
G. R. Mogridge
Keyword(s):  
Key Words ◽  
Incident Wave ◽  
Water Waves ◽  
Laboratory Tests ◽  
Large Scale ◽  
Research Council ◽  
National Research Council ◽  
Irregular Waves ◽  
Two Dimensional ◽  
The Waves

Large-scale laboratory tests of the evolution of bedforms in sand beds, under directional irregular waves, carried out at the National Research Council Canada, are described. Preliminary observations indicate that the directionality of the waves is not an important factor; bedforms remained largely two-dimensional under all but transitional conditions. Incident wave height and period, probably combined as a wave orbital amplitude near the bed, seems to be the most important factor in determining bedform dimensions, followed by the D50 sand size on the bed. Sand gradation may be unimportant. Key words: seabed, sand, water waves, bedforms, morphology, roughness.

scholarly journals Field verification of a new asphalt compactor, AMIR

1991 ◽  
Vol 18 (3) ◽  
pp. 465-471 ◽  
Author(s):  
Otto J. Svec ◽  
A. O. Abd El Halim
Keyword(s):  
Key Words ◽  
Laboratory Testing ◽  
Research Council ◽  
Joint Venture ◽  
National Research Council ◽  
Field Trials ◽  
Full Scale ◽  
Field Verification ◽  
Asphalt Mix

A prototype of a new asphalt compactor termed "asphalt multi-integrated roller (AMIR)" was built as a joint venture between the National Research Council of Canada (NRC) and a Canadian manufacturer, Lovat Tunnel Equipment, Inc. The purpose of this project was to prove this new compaction concept in a full-scale environment. This paper describes one of the field trials carried out on the campus of the NRC and reports the results quantifying the quality of the AMIR compaction. Key words: compactor, asphalt mix, field trials, laboratory testing.

scholarly journals MACH-REFLECTION AS A DIFFRACTION PROBLEM

1976 ◽  
Vol 1 (15) ◽  
pp. 45 ◽  
Author(s):  
Udo Berger ◽  
Soren Kohlhase
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Water Waves ◽  
Gas Dynamics ◽  
Mach Reflection ◽  
Diffraction Problem ◽  
Vertical Wall ◽  
Oblique Wave ◽  
Wave Heights ◽  
The Waves

As under oblique wave approach water waves are reflected by a vertical wall, a wave branching effect (stem) develops normal to the reflecting wall. The waves progressing along the wall will steep up. The wave heights increase up to more than twice the incident wave height. The £jtudy has pointed out that this effect, which is usually called MACH-REFLECTION, is not to be taken as an analogy to gas dynamics, but should be interpreted as a diffraction problem.

EL “AUDIBLE SILENCIO” DURANTE EL FRANQUISMO: ARTÍCULOS CIENTÍFICOS Y TÉCNICOS PUBLICADOS EN REVISTAS Y LENGUAS EXTRANJERAS POR INVESTIGADORES DEL CSIC (1939-1964)

2020 ◽  
pp. 227-246
Author(s):  
Fernando García Naharro
Keyword(s):  
Key Words ◽  
Research Council ◽  
National Research Council ◽  
Active Role ◽  
Applied Science ◽  
Scientific Journals ◽  
Scientific Publications ◽  
Scientific Impact

Resumen Este artículo analiza la repercusión científica internacional de los investigadores de España durante el franquismo. Para ello, trabajando con las memorias del Consejo Superior de Investigaciones Científicas (CSIC) y del Patronato “Juan de la Cierva” de Investigaciones Técnicas, se recogen los nombres y perfiles de aquellos investigadores publicando en revistas científicas extranjeras durante el periodo de los llamados “XXV Años de Paz”. Además, con una selectiva exposición de argumentos, el artículo presenta una explicación al papel activo que jugaron las publicaciones científicas en conformar y sustentar la retórica oficial de la internacionalización científica durante el franquismo. Abstract This paper examines the international scientific impact of researchers working in Spain under Franco´s dictatorship. Working with the memoires of the Spanish National Research Council (CSIC) and its Institutes on Applied Science, I recall the names and profiles of those researchers publishing in foreign scientific journals during the so-called “XXV Años de Paz” period. Moreover, with a selective exposition of arguments, I intend to provide a clear and consistent explanation of how scientific publications played an active role in supporting and shaping the Official rhetoric of scientific internationalization during Franco. Palabras claves: Consejo Superior de Investigaciones Científicas (CSIC), Ciencia, Franquismo, Revistas científicas, Investigadores. Key words: Spanish National Research Council (CSIC), Science, Franco´s dictatorship, Scientific journals, Researchers.

TRANSFORMATION ET AJUSTEMENT DES COORDONNEES D’UNE BANDE PAR CALCUL ELECTRONIQUE

1961 ◽  
Vol 15 (10) ◽  
pp. 574-580 ◽  
Author(s):  
G. H. Schut
Keyword(s):  
Research Council ◽  
Three Dimensional ◽  
National Research Council ◽  
Control Points ◽  
Two Dimensional ◽  
Ground Control Points ◽  
Mechanical Methods ◽  
Electronic Computers ◽  
Operating Instructions ◽  
Second Degree

Strip triangulation is carried out for the purpose of increasing by photogrammetric means the number of available ground control points. The triangulation must be followed by a transformation which brings the points from the strip-coordinate system to the required geodetic system. The transformation includes an adjustment when redundant points are used to increase the accuracy of the positioning and when systematic errors must be corrected for in the strip triangulation. Numerical methods of transformation and adjustment have an inherently greater accuracy. If electronic computers are used, they are also more economical than comparable graphical or mechanical methods. The following programs have been coded for the IBM-650 by the Photogrammetric Section of the National Research Council of Canada: (a) a program for three-dimensional linear conformai transformation, employing formulas (1a) and (1b), (b) a program for two-dimensional conformai transformation of horizontal coordinates, employing either the linear formulas (8) or the formulas of the second degree (10), (c) a program for two-dimensional conformai transformation of the third degree with the possibility of conversion to the fourth and fifth degree, (d) a program for transformation of horizontal coordinates of a block of overlapping strips by second-degree conformai transformations, and (e) a program for the last-mentioned transformation by third-degree conformai transformations. These programs and operating instructions can be made available for serious applicants from the National Research Council.

Two-dimensional periodic waves in shallow water

1989 ◽  
Vol 209 ◽  
pp. 567-589 ◽  
Author(s):  
Joe Hammack ◽  
Norman Scheffner ◽  
Harvey Segur
Keyword(s):  
Shallow Water ◽  
Water Waves ◽  
Two Dimensional ◽  
Reasonable Accuracy ◽  
Kp Equation ◽  
Petviashvili Equation ◽  
Stable Manner ◽  
Genus 2 ◽  
Surface Patterns ◽  
The Waves

Experimental data are presented that demonstrate the existence of a family of gravitational water waves that propagate practically without change of form on the surface of shallow water of uniform depth. The surface patterns of these waves are genuinely two-dimensional and fully periodic, i.e. they are periodic in two spatial directions and in time. The amplitudes of these waves need not be small; their form persists even up to breaking. The waves are easy to generate experimentally, and they are observed to propagate in a stable manner, even when perturbed significantly. The measured waves are described with reasonable accuracy by a family of exact solutions of the Kadomtsev-Petviashvili equation (KP solutions of genus 2) over the entire parameter range of the experiments, including waves well outside the putative range of validity of the KP equation. These genus-2 solutions of the KP equation may be viewed as two-dimensional generalizations of cnoidal waves.

On averaged equations for finite-amplitude water waves

1979 ◽  
Vol 94 (3) ◽  
pp. 401-407 ◽  
Author(s):  
M. Stiassnie ◽  
D. H. Peregrine
Keyword(s):  
Water Waves ◽  
Large Scale ◽  
Finite Amplitude ◽  
Conservation Equation ◽  
Wave Action ◽  
Background Current ◽  
Irrotational Flow ◽  
Flow Equations ◽  
Averaged Equations ◽  
The Waves

The wave-action conservation equation for water waves is always derived from a Lagrangian for irrotational flow. This is quite satisfactory if the whole flow-field (i.e. waves and background current) is irrotational, but is inadequate for a background current with a large-scale (vertical) vorticity, even if the flow has negligible vorticity on the local scale of a few wavelengths. A wave-action conservation equation is derived for this case and equations governing the flow and the waves are given in a simple form closely parallel to the irrotational flow equations.

scholarly journals Asymptotic Shallow Models Arising in Magnetohydrodynamics

Water Waves ◽  
2021 ◽  
Author(s):  
Diego Alonso-Orán
Keyword(s):  
Free Boundary ◽  
Water Waves ◽  
Large Scale ◽  
Three Dimensional ◽  
Magnetic Pressure ◽  
Two Dimensional ◽  
Magnetohydrodynamic Equations ◽  
Astrophysical Plasma ◽  
Asymptotic Models ◽  
Boundary Plasma

AbstractIn this paper, we derive new shallow asymptotic models for the free boundary plasma-vacuum problem governed by the magnetohydrodynamic equations which are vital when describing large-scale processes in flows of astrophysical plasma. More precisely, we present the magnetic analogue of the 2D Green–Naghdi equations for water waves under a weak magnetic pressure assumption in the presence of weakly sheared vorticity and magnetic currents. Our method is inspired by ideas for hydrodynamic flows developed in Castro and Lannes (2014) to reduce the three-dimensional dynamics of the vorticity and current to a finite cascade of two dimensional equations which can be closed at the precision of the model.

Diffraction of water waves by a submerged vertical plate

1970 ◽  
Vol 40 (3) ◽  
pp. 433-451 ◽  
Author(s):  
D. V. Evans
Keyword(s):  
Free Surface ◽  
Boundary Value Problem ◽  
Incident Wave ◽  
Water Waves ◽  
Vertical Plate ◽  
Velocity Potential ◽  
Wave Train ◽  
Plane Waves ◽  
Two Dimensional ◽  
Special Case

A thin vertical plate makes small, simple harmonic rolling oscillations beneath the surface of an incompressible, irrotational liquid. The plate is assumed to be so wide that the resulting equations may be regarded as two-dimensional. In addition, a train of plane waves of frequency equal to the frequency of oscillation of the plate, is normally incident on the plate. The resulting linearized boundary-value problem is solved in closed form for the velocity potential everywhere in the fluid and on the plate. Expressions are derived for the first- and second-order forces and moments on the plate, and for the wave amplitudes at a large distance either side of the plate. Numerical results are obtained for the case of the plate held fixed in an incident wave-train. It is shown how these results, in the special case when the plate intersects the free surface, agree, with one exception, with results obtained by Ursell (1947) and Haskind (1959) for this problem.

Water waves in a deep square basin

1995 ◽  
Vol 302 ◽  
pp. 65-90 ◽  
Author(s):  
Peter J. Bryant ◽  
Michael Stiassnie
Keyword(s):  
Deep Water ◽  
Water Waves ◽  
Three Dimensional ◽  
Standing Waves ◽  
Two Dimensional ◽  
Initial State ◽  
Dimensional Properties ◽  
Periodic Standing Waves ◽  
The Waves ◽  
Small Disturbances

The form and evolution of three-dimensional standing waves in deep water are calculated analytically from Zakharov's equation and computationally from the full nonlinear bounddary value problem. The water is contained in a basin with a square cross-cection, when three-dimensional properties to pairs of sides are the same. It is found that non-periodic standing waves commonly follow forms of cyclic recurrence over times. The two-dimensional Stokes type of periodic standing waves (dominated by the fundamental harmonic) are shown to be unstable to three dimensional disturbances, but over long times the waves return cyclically close to their initial state. In contrast, the three-dimensional Stokes type of periodic standing waves are found to be stabel to small disturbances. New two-dimensional periodic standing waves with amplitude maxima at other than the fundamental harmonic have been investigated recently (Bryant & Stiassnie 1994). The equivalent three-dimensional standing waves are described here. The new two-dimensional periodic standing waves, like the two-dimensional Stokes standing waves, are found to be unstable to three-dimensional disturbances, and to exhibit cyclic recurrence over long times. Only some of the new three-dimensional periodic standing waves are found to be stable to small disturbances.

Vertical-Mode and Cloud Decomposition of Large-Scale Convectively Coupled Gravity Waves in a Two-Dimensional Cloud-Resolving Model

2007 ◽  
Vol 64 (4) ◽  
pp. 1210-1229 ◽  
Author(s):  
Stefan N. Tulich ◽  
David A. Randall ◽  
Brian E. Mapes
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Deep Convection ◽  
Radiative Cooling ◽  
Convective Heating ◽  
Two Dimensional ◽  
Mean Flow ◽  
Vertical Mode ◽  
Cloud Resolving Model ◽  
The Waves

Abstract This paper describes an analysis of large-scale [O(1000 km)] convectively coupled gravity waves simulated using a two-dimensional cloud-resolving model. The waves develop spontaneously under uniform radiative cooling and approximately zero-mean-flow conditions, with wavenumber 2 of the domain appearing most prominently and right-moving components dominating over left-moving components for random reasons. The analysis discretizes the model output in two ways. First, a vertical-mode transform projects profiles of winds, temperature, and heating onto the vertical modes of the model’s base-state atmosphere. Second, a cloud-partitioning algorithm sorts sufficiently cloudy grid columns into three categories: shallow convective, deep convective, and stratiform anvil. Results show that much of the tilted structures of the waves can be captured by just two main vertical spectral “bands,” each consisting of a pair of vertical modes. The “slow” modes have propagation speeds of 16 and 18 m s−1 (and roughly a full-wavelength vertical structure through the troposphere), while the “fast” modes have speeds of 35 and 45 m s−1 (and roughly a half-wavelength structure). Deep convection anomalies in the waves are more or less in phase with the low-level cold temperature anomalies of the slow modes and in quadrature with those of the fast modes. Owing to the characteristic life cycle of deep convective cloud systems, shallow convective heating peaks ∼2 h prior to maximum deep convective heating, while stratiform heating peaks ∼3 h after. The onset of deep convection in the waves is preceded by a gradual deepening of shallow convection lasting a period of many hours. Results of this study are in broad agreement with simple two-mode models of unstable large-scale wave growth, under the name “stratiform instability.” Differences here are that 1) the key dynamical modes have speeds in the range 16–18 m s−1, rather than 23–25 m s−1 (owing to a shallower depth of imposed radiative cooling), and 2) deep convective heating, as well as stratiform heating, is essential for the generation and maintenance of the slow modes.

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