In this article a number of whole-field blood velocity measurement techniques are concisely reviewed. We primarily focus on optical measurement techniques for in vivo applications, such as laser Doppler velocimetry (including time varying speckle), laser speckle contrast imaging and particle image velocimetry (including particle tracking). We also briefly describe nuclear magnetic resonance and ultrasound particle image velocimetry, two techniques that do not rely on optical access, but that are of importance to in vivo whole-field blood velocity measurement. Typical applications for whole-field methods are perfusion monitoring, the investigation of instantaneous blood flow patterns, the derivation of endothelial shear stress distributions from velocity fields, and the measurement of blood volume flow rates. These applications require individual treatment in terms of spatial and temporal resolution and number of measured velocity components. The requirements further differ for the investigation of macro-, meso-, and microscale blood flows. In this review we describe and classify those requirements and present techniques that satisfy them.

/pdf/in-vivo-whole-field-blood-velocity-measurement-techniques-1ize1xa74f.pdf

In vivo whole-field blood velocity measurement techniques

This work concerns the analysis of non-stationary signals using Recurrence Plot Analysis concept. Non-stationary signals are present in real-life phenomena such as underwater mammal’s vocalizations, human speech, ultrasonic monitoring, detection of electrical discharges, transients, wireless communications, etc. This is why a large number of approaches for non-stationary signal analysis are developed such as wavelet analysis, higher order statistics, or quadratic time-frequency analysis. Following the context, the methods defined around the concept of Recurrence Plot Analysis (RPA) constitute an interesting way of analyzing non-stationary signals and, particularly, the transient ones. Starting from the phase space and the recurrence matrix, new approaches [the angular distance, recurrence-based autocorrelation function (ACF), average-magnitude difference function (AMDF) and time-distributed recurrence (TDR)] are introduced in order to extract information about the non-stationary signals, specific to different applications. Comparisons with existing analysis methods are presented, proving the interest and the potential of the RPA-based approaches.

Recent Advances in Non-stationary Signal Processing Based on the Concept of Recurrence Plot Analysis

Vortex flowmeters are commonly employed in technical applications and are obtainable in a variety of commercially available types. However their robustness and accuracy can easily be impaired by environmental conditions, such as inflow disturbances and/or pulsating conditions. Various post-processing techniques of the vortex signal have been used, but all of these methods are so far targeted on obtaining an improved estimate of the time-averaged bulk velocity. Here, on the other hand, we propose, based on wavelet analysis, a straightforward way to utilize the signal from a vortex shedder to extract the time-resolved and thereby the phase-averaged velocity under pulsatile flow conditions. The method was verified with hot-wire and laser Doppler velocimetry measurements.

http://iopscience.iop.org/article/10.1088/0957-0233/21/12/123001/pdf

Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis

Numerical and Experimental Research on Modular Oscillating Fin

We have designed, built, calibrated, and tested new anemometer and turbine flow meter devices to measure fluid velocity at high- and low-temperature focused and diffuse discharge sites at oceanic spreading centers. The devices perform at ocean floor depths and black smoker temperatures, and can be used to measure flow rates ranging over two orders of magnitude. Flow velocity is determined from the rotation rate of the rotor blades or paddle assembly. These devices have an open bearing design that eliminates clogging by particles or chemical precipitates as the fluid passes by the rotors. The devices are compact and lightweight enough for deployment from either an occupied or remotely operated submersible. The measured flow rates can be used in conjunction with vent temperature or geochemical measurements to obtain heat outputs or geochemical fluxes from both vent chimneys and diffuse flow regions. The devices have been tested on 30 Alvin dives on the Juan de Fuca Ridge and 3 Jason dives on the East Pacific Rise (EPR). We report 102 new measurements over a wide range of discharge temperatures (5° – 363°C), velocities (2 – 199 cm/s), and depths (1517 – 2511 m). These include the first advective heat output measurements at the High Rise vent field and the first direct fluid flow measurement at Middle Valley. Our data suggest that black smoker heat output at the Main Endeavor vent field may have declined since 1994 and that after the 2005–2006 eruption, the high=temperature advective flow at the EPR 9°50′N field may have become more channelized, predominately discharging through the Bio 9 structure. We also report first direct advective measurements in the Lau Basin and at the EPR 9°39.5′N with flow meters that predated devices described in this work and were used in the process of their development. We discuss potential error sources and how they may affect the accuracy of measurements by our and other devices. In particular, we use the turbulent plume theory to evaluate the effect of entrainment of ambient seawater.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015JB012245

Measuring fluid flow and heat output in seafloor hydrothermal environments

Fully Developed Turbulent Pipe Flow. - Decay of Disturbances in Turbulent Pipe Flow. - Optimal Characteristic Parameters for the Disturbances in Turbulent Pipe Flow. - Measurement of Velocity and Turbulence Downstream of Flow Conditioners. - Signal processing of Complex Modulated Ultrasonic Signals. - Vortex-Shedding Flow Metering Using Ultrasound. - Ultrasonic Gas-Flow Measurement Using Correlation Methods. - Ultrasound Cross-Correlation Flow Meter: Analysis by System Theory and Influence of Turbulence. - Effect of Area Changes in Swirling Flow. - Errors of Turbine Meters due to Swirl. - Investigation of Unsteady Three-Dimensional Flow Fields in a Turbine Flow Meter. - How to Design a New Flow Meter from Scratch. - Effects of Disturbed Inflow on Vortex Shedding from a Bluff Body. - Correction of the Reading of a Flow Meter in Pipe Flow Disturbed by Installation Effects. - How to Correct the Error Shift of an Ultrasonic Flow Meter Downstream of Installations.

Ernst von Lavante

Papers

Fluid mechanics of flow metering