Gravity wave patterns in the wake of a sphere in a stratified fluid

1991 ◽  
pp. 489-503 ◽  
Author(s):  
J. M. Chomaz ◽  
P. Bonneton ◽  
A. Butet ◽  
E. J. Hopfinger ◽  
M. Perrier
Keyword(s):  
Gravity Wave ◽  
Stratified Fluid ◽  
Wave Patterns

On the calculation of wave patterns

1972 ◽  
Vol 53 (4) ◽  
pp. 637-645 ◽  
Author(s):  
C. Hunter
Keyword(s):  
Gravity Waves ◽  
Stratified Fluid ◽  
Circular Path ◽  
Straight Line ◽  
Wave Patterns ◽  
Single Process ◽  
The Waves

The calculation of the pattern of waves produced by a point disturbance in a steady field which may be non-uniform can be performed straightforwardly by a single process of integration along the characteristic rays. For illustration, the method is applied to gravity waves produced by a source moving either in a straight line or in a circular path, to the symmetrical waves produced by a source in an expanding sheet and to the waves resulting from an instantaneous disturbance in :I stratified fluid.

Velocity distribution around a sphere descending in a linearly stratified fluid

2017 ◽  
Vol 826 ◽  
pp. 759-780 ◽  
Author(s):  
Shinya Okino ◽  
Shinsaku Akiyama ◽  
Hideshi Hanazaki
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
High Speed ◽  
Particle Image ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Stratified Fluid ◽  
Velocity Variation ◽  
Image Velocimetry ◽  
Wave Patterns

The flow around a sphere descending at constant speed in a salt-stratified fluid is observed by particle image velocimetry. A unique characteristic of this flow is the appearance of a thin and high-speed rear jet whose maximum velocity can reach more than five times the sphere velocity. In this study we have investigated how the velocity distributions, especially those in the jet and in the boundary layer of the sphere, vary when the Froude number $Fr(=W^{\ast }/N^{\ast }a^{\ast })$ or the Reynolds number $Re(=W^{\ast }(2a^{\ast })/\unicode[STIX]{x1D708}^{\ast })$ ($W^{\ast }$: vertical velocity of the sphere, $N^{\ast }$: Brunt–Väisälä frequency, $a^{\ast }$: radius of the sphere, $\unicode[STIX]{x1D708}^{\ast }$: kinematic viscosity of the fluid) is changed. The results show that the radius of the jet and the thickness of the boundary layer are comparable, and they decrease for smaller Froude numbers and larger Reynolds numbers. Both of them are estimated at moderate Reynolds numbers by the primitive length scale of the stratified fluid ($l_{\unicode[STIX]{x1D708}}^{\ast }=\sqrt{\unicode[STIX]{x1D708}^{\ast }/N^{\ast }}$), or in non-dimensional form by $l_{\unicode[STIX]{x1D708}}^{\ast }/2a^{\ast }=(Fr/2Re)^{1/2}$. The overall velocity distribution in the lee of the sphere is measured to identify the internal wave patterns and their effect on the velocity variation along the jet. Corresponding numerical simulation results using the axisymmetry assumption are in agreement with the experimental results.

Spatial and temporal analysis of high-frequency internal gravity wave signatures in brightness temperature satellite images

2021 ◽  
Author(s):  
Robert Vicari
Keyword(s):  
Water Vapor ◽  
Brightness Temperature ◽  
Gravity Wave ◽  
Gravity Waves ◽  
High Frequency ◽  
Satellite Images ◽  
Internal Gravity Wave ◽  
Internal Gravity Waves ◽  
Small Scale ◽  
Wave Patterns

<p>Highly idealized model studies suggest that convectively generated internal gravity waves in the troposphere with horizontal wavelengths on the order of a few kilometers may affect the lifetime, spacing, and depth of clouds and convection. To answer whether such a convection-wave coupling occurs in the real atmosphere, one needs to find corresponding events in observations. In general, the study of high-frequency internal gravity wave-related phenomena in the troposphere is a challenging task because they are usually small-scale and intermittent. To overcome case-by-case studies, it is desirable to have an automatic method to analyze as much data as possible and provide enough independent and diverse evidence.<br>Here, we focus on brightness temperature satellite images, in particular so-called satellite water vapor channels. These channels measure the radiation at wavelengths corresponding to the energy emitted by water vapor and provide cloud-independent observations of internal gravity waves, in contrast to visible and other infrared satellite channels where one relies on the wave impacts on clouds. In addition, since these water vapor channels are sensitive to certain vertical layers in the troposphere, combining the images also reveals some vertical structure of the observed waves.<br>We propose an algorithm based on local Fourier analyses to extract information about high-frequency wave patterns in given brightness temperature images. This method allows automatic detection and analysis of many wave patterns in a given domain at once, resulting in a climatology that provides an initial observational basis for further research. Using data from the instrument ABI on board the satellite GOES-16 during the field campaign EUREC<sup>4</sup>A, we demonstrate the capabilities and limitations of the method. Furthermore, we present the respective climatology of the detected waves and discuss approaches based on this to address the initial question.</p>

scholarly journals Propagation directions of gravity wave patterns observed in OH CCD images during the SEEK Campaign

1998 ◽  
Vol 25 (11) ◽  
pp. 1793-1796 ◽  
Author(s):  
Takuji Nakamura ◽  
Toshitaka Tsuda ◽  
Hirohisa Miyagawa ◽  
Yoshihito Matsushita ◽  
Hiroshi Fukunishi ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Wave Patterns

scholarly journals Decoupling of Balanced and Unbalanced Motions and Inertia–Gravity Wave Emission: Small versus Large Rossby Numbers

2008 ◽  
Vol 65 (11) ◽  
pp. 3528-3542 ◽  
Author(s):  
Vladimir Zeitlin
Keyword(s):  
Gravity Wave ◽  
Stratified Fluid ◽  
Geostrophic Adjustment ◽  
Inertial Instability ◽  
Wave Emission ◽  
Symmetric Instability

Abstract This paper provides a brief review of recent results on decoupling of fast [inertia–gravity wave (IGW)] and slow (vortex) motions at small Rossby numbers obtained in the framework of the geostrophic adjustment of localized perturbations. Special attention is paid to the IGW emission and its interpretation in the context of “spontaneous imbalance.” Several mechanisms that lead to spontaneous IGW emission and, thus, to violations of fast–slow splitting at large Rossby numbers are reviewed: Lighthill radiation, symmetric/inertial instability, and ageostrophic shear (Rossby–Kelvin) instability. New results on the saturation of symmetric instability and on the existence of Rossby–Kelvin instability in continuously stratified fluid are presented.

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