scholarly journals Improvement of the SIGMA-1 Measuring Complex for Studies of Langmuir Circulations and Surface Wave Breaking in the Black Sea

2021 ◽  
Author(s):  
M. I. Pavlov ◽  
A. M. Chukharev ◽  
◽  
Keyword(s):  
Flow Velocity ◽  
Wave Breaking ◽  
Velocity Vector ◽  
Eddy Correlation ◽  
The Black Sea ◽  
Sensor Calibration ◽  
Natural Oscillations ◽  
Measuring Complex ◽  
Sigma 1 ◽  
Langmuir Circulations

The purpose of this article is to describe modernization of SIGMA-1 measuring complex. The modernization was performed to improve the quality of research of the wave breaking mechanisms and Langmuir circulations at the stationary oceanographic platform MHI. The article deals with the effects of natural oscillations of the device and changes in the housing position on the measured components of the flow velocity vector. The device natural oscillations are recorded by a position monitoring system consisting of a set of sensors: accelerometers and a magnetometer. A model study of permissible rotations and maximum tilt angles showed that in the absence of an angular velocity sensor, the uncorrected measured components of the flow velocity vector can differ significantly from the actual ones. To solve this problem, MPU-9250 module with an accelerometer, gyroscope and magnetometer was chosen; Arduino Nano was used as a microcontroller system. Based on the theory of calculating spatial angles, a program for correcting the measured components of velocity pulsations for the new module was developed in Arduino IDE programming environment. The optimal program (Magneto) for calibrating the magnetometer was selected as the most accurate and satisfying the conditions of use at the oceanographic platform. The main stages of sensor calibration are described. The flow velocity components measured in the device coordinate system are adjusted for the values of tilt angles, angular and linear velocities, the calculation is performed using the eddy correlation method. The developed system has been tested on specialized equipment in laboratory setting and has the following characteristics: within the range –30…+30° the maximum pitch error is 0.31°; the maximum roll error is 0.42°; the maximum magnetometer error is 2.09°. The achieved characteristics allow significant increase in the accuracy of measuring the velocity vector and reliability estimate of influence of various physical processes on the vertical exchange.

Effects of Surface Tension in the Near Field Wave Breaking of Ships

2008 ◽  
Author(s):  
Fabrizio Pistani ◽  
Angelo Olivieri ◽  
Emilio Campana
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Flow Velocity ◽  
Wave Breaking ◽  
Near Field ◽  
Surface Elevation ◽  
Vortical Structures ◽  
High Speeds ◽  
Resistance Curves ◽  
Surface Tension Forces

When model experiments are performed the viscous and surface tension forces are not scaled accordingly. Thus not all of the features of the flow can be satisfactorily reproduced at model scale. A comparative set of experiments for measuring the model resistance, the free surface elevation and the flow velocity in the near field, have been carried out for models of different scales for evaluating the influence of the dimensions in reproducing the complete wave breaking dynamics. The resistance curves of the models show that the scale effect is present both for low and high speeds. Comparison of the averaged surface elevation reveals that the largest model possess already some of the full scale features. The comparison of the flow velocity fields highlights substantial differences among the models in the formation of the vortical structures. The influence of these vortices on the free surface is discussed and a correlation with surface scars is proposed.

Reconstruction of the blood flow velocity vector as an additional mode of ultrasonic tomograph

2015 ◽  
Vol 23 (2) ◽  
pp. 135-142 ◽  
Author(s):  
V. A. Burov ◽  
O. V. Matveev ◽  
D. I. Zotov ◽  
O. D. Rumyantseva
Keyword(s):  
Blood Flow ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Velocity Vector ◽  
Additional Mode

“Sigma-1” Measuring Complex for the Investigation of Small-Scale Characteristics of Hydrophysical Fields in the Upper Layer of the Sea

2005 ◽  
Vol 15 (5) ◽  
pp. 311-322 ◽  
Author(s):  
A. S. Samodurov ◽  
V. Z. Dykman ◽  
V. A. Barabash ◽  
O. I. Efremov ◽  
A. G. Zubov ◽  
...  
Keyword(s):  
Small Scale ◽  
Measuring Complex ◽  
Sigma 1 ◽  
Scale Characteristics

Turbulent structure of the subsurface layer of the sea according to the data of the Sigma-1 measuring complex

2007 ◽  
Vol 17 (2) ◽  
pp. 75-87
Author(s):  
A. M. Chukharev ◽  
V. A. Barabash ◽  
A. G. Zubov ◽  
O. I. Pavlenko
Keyword(s):  
Subsurface Layer ◽  
Turbulent Structure ◽  
Measuring Complex ◽  
Sigma 1

scholarly journals Blood flow velocity vector field reconstruction from dual-beam bidirectional Doppler OCT measurements in retinal veins

2015 ◽  
Vol 6 (5) ◽  
pp. 1599 ◽  
Author(s):  
Gerold C. Aschinger ◽  
Leopold Schmetterer ◽  
Veronika Doblhoff-Dier ◽  
Rainer A. Leitgeb ◽  
Gerhard Garhöfer ◽  
...  
Keyword(s):  
Blood Flow ◽  
Vector Field ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Velocity Vector ◽  
Velocity Vector Field ◽  
Field Reconstruction ◽  
Dual Beam ◽  
Doppler Oct

scholarly journals Estimation of the Vertical Turbulent Exchange Intensity in the Main Pycnocline Layer in the Prikerchensky Area of the Black Sea Shelf

2021 ◽  
Author(s):  
D. A. Kazakov ◽  
A. S. Samodurov ◽  
◽  
Keyword(s):  
Black Sea ◽  
Measurement Data ◽  
Water Area ◽  
Turbulent Exchange ◽  
The Black Sea ◽  
Buoyancy Frequency ◽  
Turbulent Diffusion Coefficient ◽  
Shelf Slope ◽  
Sigma 1 ◽  
Deep Water Area

The paper investigates the seasonal variability of the vertical turbulent exchange coefficient in the upper stratified layer of the Black Sea. The expedition data used in this work containing information on the microstructure of physical fields were obtained in different hydrological seasons covering the northeastern part of the Black Sea in the Prikerchensky area of the shelf slope. The data were collected during cruises of r/v “Professor Vodyanitsky” in 2016–2019 using “Sigma-1” sounding complex. Based on the semi-empirical methods of assessment of vertical turbulent exchange in the deep-water area of the Black Sea, the dependence of the vertical turbulent diffusion coefficient K on the buoyancy frequency N in the studied layer was established from the flow fluctuation characteristics, with the corresponding graphs and their approximating power-law dependences K  A  N  plotting. In addition, the vertical distribution of the K coefficient with depth was analyzed. Comparative analysis of the obtained dependences with the results of the 1.5D model was carried out. The analysis of the measurement data showed that the results obtained in this work do not contradict the original model. The results can also be used to assess the vertical fluxes of heat, salt and other dissolved chemical and biological substances depending on stratification in the studied part of the Black Sea for different seasons.

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