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.

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In vivo whole-field blood velocity measurement techniques

This paper is devoted to the Karman vortex shedding flowmeter?its physical fundamentals, research, design, optimization and applications. The flowmeter is currently in a stage of rapid development. Many valuable discoveries concerning the applied Karman vortex street phenomenon have been made. In this paper, various aspects of the problems concerning the vortex meter are described. Fundamental problems and their solutions are presented based on a description of the principles of operation. The most important methods of investigating the phenomena that appear in the vortex meter are described: measured signal analysis, flow field investigations using a hot-wire anemometer, flow visualization supported by image processing and numerical modelling. The most powerful achievements in these fields are also described.

https://iopscience.iop.org/article/10.1088/0957-0233/16/3/R01/pdf

The vortex flowmeter: various methods of investigating phenomena

This paper highlights various aspects of design of a vortex flowmeter. Vortex shedding and vortex flowmeters are known from decades. However, the vortex shedding phenomenon is not understood clearly as applicable to vortex flowmeter. In the recent past large body of literature is reported on the performance of vortex flowmeter. This report comprehensively summarizes all the improvements which help the designer to build a vortex flowmeter. The paper systematically explains various aspects related to development of a vortex flowmeter with peculiarities associated with its design.

Review on vortex flowmeter—Designer perspective

Two-dimensional ultrasonic anemometer using the directivity angle of an ultrasonic sensor

Comparison of pressure and ultrasound measurements in vortex flow meters

Vortex shedding flowmeters and ultrasound detection: signal processing and influence of bluff body geometry

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.

Fluid mechanics of flow metering

Interaction between Vortices and Ultrasonic Waves in Vortex Shedding Flowmeters

Optimization of acoustic signals in a vortex-shedding flowmeter using numerical simulation

The coincidence of vortices generated by a bluff body in a gaseous flow, which is well-known as the Karman vortex street, with an ultrasonic beam crossing these vortices raises many questions concerning physics and signal processing. Usually the vortices are detected by pressure sensors in the pipe wall or inside the bluff body. Using ultrasound for vortex detection is a powerful advantageous alternative combination. The ultrasonic beam is modulated by the velocity components of the vortices and varying fluid density. The kind of modulation depends on the structure of the vortices that are influenced by the bluff-body geometry and size. Measurements and simulations show that conventional triangular bluff bodies with the large size used for pressure measurements are unsuitable for ultrasonic measurements because of the lack of knowledge about secondary vortices. They can be avoided by turning the bluff body so as to face the tip to the inflow. As ultrasound is very sensitive to the smallest influences, the bluff-body size can be reduced considerably. Even the shape can be adapted. The best results are obtained with a 3-mm threaded rod as the bluff body in a pipe of 100mm diameter. Pressure losses behind such small bluff bodies can be neglected. Independent of the bluff-bodies shapes and sizes vortex meters are sensitive to disturbed profiles and pulsation.

V. Hans

Papers

Vortex shedding flowmeters and ultrasound detection: signal processing and influence of bluff body geometry

Fluid mechanics of flow metering

Interaction between Vortices and Ultrasonic Waves in Vortex Shedding Flowmeters

Optimization of acoustic signals in a vortex-shedding flowmeter using numerical simulation

Vortex-Shedding Flow Metering Using Ultrasound