We introduced our recent works on development of rheometry utilizing ultrasonic velocity profiling (UVP) that can capture spatio-temporal velocity information even in opaque fluids. Rheological properties describing relations in stress, strain and strain rate are reflected into flow field, and analyzing flow information obtained in simple unsteady flow configurations may provide the rheological properties. We adopted cylindrical vessel with regular oscillation on the cylinder wall as the configuration, and evaluated effective Newtonian viscosity of viscous oil with dispersed small bubbles and time-dependent behavior of montmorillonite suspension that is one of thixotropic fluids to demonstrate applicability of the rheometry. We also explained novel idea of ‘flow surface’ that aims to describe rheological properties without using rheology models.
Flow measurement of spatio-temporal velocity field in a Taylor-Couette vortex flow (TVF) with a short annulus was investigated with using Ultrasonic Velocity Profiler (UVP). These methods have significant advantages over conventional methods since it can obtain the instantaneous spatio-temporal information as a function of space and time even in opaque multiphase flows like bioreactors. Boundary effects with a short annulus of TVF called Ekman boundary layer are considered generating the various modes of vortex structure. In the present study, axial mean and instantaneous component of velocity profiles in the axis direction are measured with using the UVP and its flow characteristics in higher Reynolds region with the Ekman boundary is analyzed with spectrum method. The wavy vortex flow, the modulated and the chaotic flow are visualized through the spatio-temporal velocity field. These results could be useful for investigating the chemical flow characteristics and designing the industrial chemical devices or bioreactor systems.
UVP is one of promising measurement techniques for liquid-metal flows. Lead-lithium is the liquid metal which is a promising candidate of coolant in a nuclear fusion reactor. The present article is a summary of a series of UVP experiments of lead-lithium flows, and related investigations. In addition, prospects of the UVP experiments and development are described.
We introduce the uncertainty estimation of flowrate measurement using ultrasonic Doppler velocity profiler (UVP). A fundamental uncertainty analysis for a flowrate measurement in a pipe using UVP and an evaluation of the estimated uncertainty by an actual flow calibration are described. The relative expanded uncertainty due to internal factors is estimated to be 0.34% with a coverage factor of 2. In addition, experiments are carried out in a disturbed flow. Flowrate measurement is based on a multi-path measurement using three ultrasonic transducers. To generate the disturbed flow, obstacle plates are installed upstream of the test section. The maximum difference from the reference flowrate given by the national standard calibration facility of water flowrate is over 2% when the measurement is performed at 8D downstream of the obstacle plate. At 25D downstream of the obstacle plate, the deviation is within the fundamental uncertainty level.
The ultrasonic velocity profile (UVP) method is a powerful tool for measuring velocity profiles in a pipe and it has been applied for measuring flow rate. In this paper, a velocity extension method for use with ultrasonic pulsed Doppler method is introduced to increase the maximum detectable velocity which is limited by the Nyquist sampling theorem. The measurement volume is shown to be among the important parameters that must be considered in assessing the traceability of the reflector during the pulse emission interval. Hence, a larger measurement volume is required to measure higher velocities. In order to improve the flow rate accuracy, multi-wave ultrasonic method is introduced. The velocity profiles in the near-wall region are measured using an 8-MHz sensor with a small diameter, while those far from the transducer are measured using a hollow 2-MHz sensor in the multi-wave transducer. The techniques are shown to be particularly effective for measuring higher flow rates in a large-diameter pipe.
Phased array ultrasonic velocity profiler (PAUVP) method is presented. Since UVP is applied to various kind of flows, ultrasonic transducer should be design accordingly depending on the flow configuration. Therefore, procedures to design and evaluate phased array transducer is firstly presented. Vector reconstruction technique is then described, which employs differences of Doppler frequencies analyzed in the transducer array. Measurement accuracy of PAUVP system is evaluated using horizontal pipe flow. Estimation accuracies of both angle and magnitude of velocity vector are confirmed by comparing flow direction and numerical simulation data, respectively. Finally, measurement in a water tank is demonstrated, which shows the applicability of PAUVP to visualize two-dimensional velocity vector in fluid flow.
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