scholarly journals Wind-induced internal seiches in Vossoroca reservoir, PR, Brazil

RBRH ◽  
2018 ◽  
Vol 23 (0) ◽  
Author(s):  
Rafael de Carvalho Bueno ◽  
Tobias Bernward Bleninger
Keyword(s):  
Dispersion Relation ◽  
Internal Wave ◽  
Internal Waves ◽  
Careful Analysis ◽  
Thermocline Depth ◽  
Baroclinic Mode ◽  
Large Lakes ◽  
Frequency Spectra ◽  
Vertical Movements ◽  
Internal Seiches

ABSTRACT The vertical movements caused by internal waves in lakes and reservoirs have chemical and biological consequences for these ecosystems. The vast majority of studies that investigate internal waves are conducted on large lakes. There are just few researches that investigate this phenomenon on dendritic reservoirs. The purpose of this research was to identify internal waves (baroclinic mode) in the Vossoroca reservoir by using temperature time series recorded between May to November 2012. A two-layer method was used which considered rigid upper and lower boundaries. Moreover, the potential flow theory was used for both layers since the flow within each layer was considered irrotational. From the dispersion relation, we obtained the theoretical shallow internal wave period. The power spectral density (PSD) of temperature series of thermocline depth, provided by fast Fourier transform, helped in the identification on the frequency peak. Subsequently, the theoretical period was compared with the frequency spectra. Using a careful analysis (excluding the interference of solar radiation and intensity of wind), we observed a clear peak in November due to an internal wave with period around 8 hours, which matched the theoretical calculation from the dispersion relation equation for V1H1 mode. Weak winds from southwest excited a V1H1 baroclinic mode. According to spectral analysis, after the passage of this long-basin internal seiches, we identified the formation of higher vertical internal seiche modes. In addition, we observe indications of V1H1 mode degeneration.

scholarly journals Observations of thermohaline sound-speed structure induced by internal waves and spice in the summer 2015 Canada Basin marginal ice zone

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Dominic DiMaggio ◽  
John A. Colosi ◽  
John Joseph ◽  
Annalise Pearson ◽  
Peter F. Worcester ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Internal Wave ◽  
Internal Waves ◽  
Sound Speed ◽  
Canada Basin ◽  
The Arctic ◽  
Spectral Slope ◽  
Frequency Spectra ◽  
Sound Speed Structure ◽  
Speed Fluctuations

The Arctic seas are in a period of transition as they adjust to stimuli from anthropogenic climate change. The acoustic response to this adjustment is of fundamental interest, as acoustics provide an important means for Arctic remote sensing, communication and navigation, and there are important biological implications for marine mammals and other organisms that use sound. The Canada Basin Acoustic Propagation Experiment (CANAPE) is an effort to study Arctic acoustics; this paper reports on ocean sound-speed measurements from a pilot study undertaken between 30 July and 16 August 2015. Moored and shipborne observations of temperature and salinity were made in the upper 600 m of the ocean, allowing analysis along isopycnals (surfaces of constant density) to separate sound-speed structure due to internal-wave-induced vertical displacements from those originating from density-compensated temperature and salinity variations termed spice. Frequency spectra and vertical covariance functions were used to describe the space/time scales of displacements and spice. Internal-wave frequency spectra show a spectral slope much lower than the Garrett-Munk model, with the energy level roughly 4% of the standard Garrett-Munk value. Frequency spectra of spice show a form similar to the internal-wave spectra but with a slightly steeper spectral slope, presumably due to the horizontal advection of the spice by internal-wave currents. The root mean square sound-speed fluctuations from internal waves were small with values less than 0.1 m s–1. Spicy sound-speed fluctuations were much stronger, particularly in the upper 100 m where a maximum of 0.25 m s–1 was observed. Both processes have vertical decorrelation lengths less than 100 m. The observed strong variations in vertical and horizontal sound-speed structure will have significant impacts on acoustic applications, especially in the realm of communications, navigation, and remote sensing.

An analogy between electromagnetic and internal waves

2019 ◽  
Vol 485 (4) ◽  
pp. 428-433
Author(s):  
V. G. Baydulov ◽  
P. A. Lesovskiy
Keyword(s):  
Angular Momentum ◽  
Conservation Laws ◽  
Internal Wave ◽  
Special Relativity ◽  
Internal Waves ◽  
Maxwell Equations ◽  
Wave Equations ◽  
Lagrange Function ◽  
Lorentz Transformations ◽  
Symmetry Transformations

For the symmetry group of internal-wave equations, the mechanical content of invariants and symmetry transformations is determined. The performed comparison makes it possible to construct expressions for analogs of momentum, angular momentum, energy, Lorentz transformations, and other characteristics of special relativity and electro-dynamics. The expressions for the Lagrange function are defined, and the conservation laws are derived. An analogy is drawn both in the case of the absence of sources and currents in the Maxwell equations and in their presence.

Density Wave Measurements in a Rectangular Clarifier

1983 ◽  
Vol 18 (1) ◽  
pp. 129-150 ◽  
Author(s):  
Mark K. Watson ◽  
R.R. Hudgins ◽  
P.L. Silveston
Keyword(s):  
Power Spectrum ◽  
Internal Wave ◽  
Internal Waves ◽  
Wave Motion ◽  
Wave Amplitude ◽  
Suspended Solids ◽  
Small Volume ◽  
Density Wave ◽  
Measure Concentration ◽  
Wave Measurements

Abstract Internal wave motion was studied in a laboratory rectangular, primary clarifier. A photo-extinction device was used as a turbidimeter to measure concentration fluctuations in a small volume within the clarifier as a function of time. The signal from this device was fed to a HP21MX minicomputer and the power spectrum plotted from data records lasting approximately 30 min. Results show large changes of wave amplitude as frequency increases. Two distinct regions occur: one with high amplitudes at frequencies below 0.03 Hz, the second with very small amplitudes appears for frequencies greater than 0.1 Hz. The former is associated with internal waves, the latter with flow-generated turbulence. Depth, velocity in the clarifier and inlet suspended solids influence wave amplitudes and the spectra. A variation with position or orientation of the probe was not detected. Contradictory results were found for the influence of flow contraction baffles on internal wave amplitude.

A multi-layer model for nonlinear internal wave propagation in shallow water

2012 ◽  
Vol 695 ◽  
pp. 341-365 ◽  
Author(s):  
Philip L.-F. Liu ◽  
Xiaoming Wang
Keyword(s):  
Wave Propagation ◽  
Internal Wave ◽  
Shallow Water ◽  
Internal Waves ◽  
Bottom Topography ◽  
Laboratory Data ◽  
Constant Density ◽  
Layer Model ◽  
Fluid System ◽  
Nonlinear Internal Wave

AbstractIn this paper, a multi-layer model is developed for the purpose of studying nonlinear internal wave propagation in shallow water. The methodology employed in constructing the multi-layer model is similar to that used in deriving Boussinesq-type equations for surface gravity waves. It can also be viewed as an extension of the two-layer model developed by Choi & Camassa. The multi-layer model approximates the continuous density stratification by an $N$-layer fluid system in which a constant density is assumed in each layer. This allows the model to investigate higher-mode internal waves. Furthermore, the model is capable of simulating large-amplitude internal waves up to the breaking point. However, the model is limited by the assumption that the total water depth is shallow in comparison with the wavelength of interest. Furthermore, the vertical vorticity must vanish, while the horizontal vorticity components are weak. Numerical examples for strongly nonlinear waves are compared with laboratory data and other numerical studies in a two-layer fluid system. Good agreement is observed. The generation and propagation of mode-1 and mode-2 internal waves and their interactions with bottom topography are also investigated.

A conservation law for internal gravity waves

1976 ◽  
Vol 78 (2) ◽  
pp. 209-216 ◽  
Author(s):  
Michael Milder
Keyword(s):  
Internal Wave ◽  
Group Velocity ◽  
Internal Waves ◽  
Gravity Waves ◽  
Conservation Law ◽  
Short Wavelength ◽  
Internal Gravity Waves ◽  
Volume Integral ◽  
Weak Density ◽  
Progressive Waves

The scaled vorticity Ω/N and strain ∇ ζ associated with internal waves in a weak density gradient of arbitrary depth dependence together comprise a quantity that is conserved in the usual linearized approximation. This quantity I is the volume integral of the dimensionless density DI = ½[Ω2/N2 + (∇ ζ)2]. For progressive waves the ‘kinetic’ and ‘potential’ parts are equal, and in the short-wavelength limit the density DI and flux FI are related by the ordinary group velocity: FI = DIcg. The properties of DI suggest that it may be a useful measure of local internal-wave saturation.

Water movements in lakes during summer stratification; evidence from the distribution of temperature in Windermere

1952 ◽  
Vol 236 (635) ◽  
pp. 355-398 ◽  
Keyword(s):  
Internal Waves ◽  
Mathematical Form ◽  
Historical Survey ◽  
Thermo Electric ◽  
Stratified Lakes ◽  
Natural Lakes ◽  
Complicating Factors ◽  
Internal Seiches ◽  
Theoretical Analyses ◽  
Scottish Lochs

The first part of this paper is taken up with an historical survey of the relatively few observations, some detailed and some less so, of internal seiches (internal standing waves) in lakes. After a description of the thermo-electric thermometer employed, there follow details and illustrations of the evidence, from temperature observations, for such internal waves in the northern basin of Windermere. Two main phases could be distinguished: (i) motion under wind stress leading to quasi-steady states with some or all of the isotherms tilted; (ii) internal seiche motion which developed after the wind had dropped. These observations confirm the findings of Wedderburn and his collaborators on the Scottish Lochs (1907-15). The results from Windermere are presented, not because any such confirmation is necessary, but in order to secure belated recognition of the fact that Wedderburn’s ‘ temperature seiche ’ is not an isolated phenomenon, but is an everyday feature of movement in stratified lakes subject to wind action. As this movement is an important and largely unrecognized factor in lake environment, this paper is addressed mainly to limnologists. In its latter part, results of theoretical analyses of a detailed series of observations are presented in non-mathematical form. The applicability of a theory of oscillations in a basin with three layers of differing density (set out in an appendix by M. S. Longuet-Higgins) is tested by comparing theoretical and observed deflexions of selected isotherms from their equilibrium levels, resulting from internal waves after a gale. This theory also enables horizontal components of velocity and displacement to be calculated for each layer. Complicating factors in natural lakes are enumerated, and the influence of internal waves on lake biology and sedimentation is discussed.

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