Ultrasonic Velocity Profiler Research Articles

Experimental Investigation of the Partial Vegetation Effect on the Flood Wave Propagation Resulted from Dam Failure in Urkmez Residential Area by means of Distorted Physical Model

The purpose of this study is to investigate the effect of partial vegetation on the wave propagation resulted from sudden dam failure in a residential area. Temporal variations of water depths and flood wave propagation velocities were determined and compared with those obtained from the experiments performed without vegetation. The experiments were performed on the distorted physical model of Urkmez Dam and its downstream region. The distorted physical model with horizontal scale of 1/150 and vertical scale of 1/30 contains the dam reservoir, the dam body, the residential area of Urkmez coastal town until the sea and the partial vegetation. In the model, the reservoir has an active volume of 11.222 m3, the dam body has a length of 2.84 m and a height of 1.07 m, and the downstream area is nearly 200 m2. Water depths were measured by e+ WATER L level sensors placed at various locations of the downstream region. Velocities were measured by ultrasonic velocity profilers (UVP) located near the level sensors. Flood wave propagation was recorded by the high definition digital camera. Experimental findings obtained from the physical model were converted to the prototype values, in nature. The changes in water depths and elapsed times, also the changes in velocities and their occurrence times were determined for different zones of the downstream area in the presence of vegetation. The experimental results revealed that in such a dam failure, the flood arrives at the sea in 6 s in the absence of vegetation, while in 10 s in the presence of vegetation. These values correspond to 2.74 min and 4.57 min, respectively in the prototype. The existence of vegetation resulted in decrease in flood propagation velocities mainly in the dense residential area, as expected. It was observed that the maximum water depths were increased at the left bank and decreased at the right bank, except at level sensor S6 which is very close to the creek. It was observed that the maximum depth averaged velocities were decreased in the sparse and dense residential areas. The existence of the vegetation changed considerably the local velocities during rising and recession stages of the water depth. It was found that the order of magnitude of the prototype velocities was high and such velocities can cause serious damage mainly in the buildings close to the dam body. Because the presence of vegetation caused a decrease in flood propagation velocities in the sparse and dense residential areas, it would reduce the damages on the buildings in these areas.

Effect of Baffle Clearance on Scale Deposition in an Agitated Vessel.

The material deposition in a mixing tank agitated by the MAXBLEND impeller in a turbulent state was quantified and compared between cases with and without baffle clearance. Magnesium hydroxide formed from the chemical reaction between calcium hydroxide and magnesium chloride was used as a model of scale formation. Flow velocity in the tank was investigated by employing computational fluid dynamics simulation and experimentally validated by an ultrasonic velocity profiler method. Results showed that the amount of scale decreased with the increase in the rotational speed of the impeller due to the erosion effect on the tank wall. In the case without baffle clearance, the smaller weight of the scale was deposited on the front of the baffle plate due to the flow impingement, which enhanced the removal of the scale deposition. However, the lower-velocity magnitude behind the baffles resulted in an enhancement in the formation of scale. Installation of baffle clearance caused a contraction flow in between the tank wall and baffles, and consequently, the higher flow velocity reduced the amount and thickness of the scale. Measurement of the torque showed that the baffle clearance did not affect the power consumption, so the installation of baffle clearance can be a promising approach to reduce scale deposition in terms of saving operational costs and increasing process efficiency and safety.

Simultaneous Measurement of Two-Phase Flow Parameters for Drift-Flux Model

The drift-flux model is widely used in study, calculation and design of two-phase flow. It is a highly efficient model that requires little computation resources. In the model, accurate calculation of the distribution parameter C0 and the drift velocity Vgj is a critically important factor. The calculation requires simultaneously measured data of phase velocity and void fraction distributions or profiles. By using currently widely used methods for two-phase flow measurement, satisfying the requirement is highly difficult. This paper presents novel results of simultaneous measurement of the phase velocity and void fraction profiles in a vertical round tube of 50 mm inner diameter. A combination measurement method has been developed. It comprises the multiwave Ultrasonic Velocity Profile (multiwave UVP) method and the Wire Mesh Tomography (WMT). Based on the measured data, C0 and Vgj have been calculated. They have been compared with those of the published experimental data and correlations. Analyses of the measured data have been carried out. For the first time, the analysis results reveal the variation of C0 and Vgj in the measured flow conditions. More importantly, the data obtained are also useful for the development and validation of the computational codes for two-phase flow.

Ultrasonic velocity profiler applied to explore viscosity\u2013pressure fields and their coupling in inelastic shear-thinning vortex streets

A method for simultaneous estimation of viscosity and pressure fields in inelastic shear-thinning fluids is developed by means of ultrasound velocity profiling technique (UVP). In the method, equation of continuity, rheological model and pressure Poisson equation are incorporated as data processing sequences for measured velocity distributions. The proposed method is applied to study the vortex street structure formed behind a circular cylinder, which shows viscosity–pressure coupling due to shear-thinning property of fluid. For demonstration, aqueous solution of CMC (carboxy methyl cellulose) of weight concentration of 0.1% is chosen as the working fluid with shear-thinning property. An alternating staggered pattern of low-pressure spots is successfully reconstructed for zero-shear-based Reynolds number, Re = 50–300. We have found that increasing Re resulted in decrease in vortex shedding Strouhal number because of vortex sustainability supported by shear-thinning property.Graphical abstract

Turbulence Characteristics of the Flexible Circular Cylinder Agitator

A flexible protruding surface was employed as the flow disturbance to promote turbulence at the area of interest. An ultrasonic velocity profiler, UVP technique, was used to study the mean and fluctuating flow properties in the near wake of the rigid and flexible protruding surface in a water tunnel. The polymer based, ethylene-vinyl acetate (EVA) with an aspect ratio of AR = 10, 12, 14, 16 was used as the flexible circular cylinder, and submerged in a flow at Re = 4000, 6000 and 8000. The motion of the cylinder altered the fluid flow significantly. As a means to quantify turbulence, the wakes regions and production terms were analyzed. In general, the flexible cylinders show better capability in augmenting the turbulence than the rigid cylinder. The results show that the turbulence production term generated by the flexible cylinder is higher than that of rigid cylinder. The localized maximum shear production values have increased significantly from 131%, 203% and 94% against their rigid counterparts of AR = 16 at the Re = 4000, 6000 and 8000, respectively. The performance of turbulence enhancement depends heavily on the motion of the cylinder. The findings suggest that the turbulence enhancement was due to the oscillation of the flexible cylinder. The results have concluded that the flexible cylinder is a better turbulence generator than the rigid cylinder, thus improving the mixing of fluid through augmented turbulent flow.

Experimental Investigation on Effects of Elastic Agitator to Turbulence Enhancement

The conventional method to promote mass, momentum and energy transport between fluid particles is to introduce a disturbance to the flow. An ultrasonic velocity profiler, UVP experiment was used to study the mean and fluctuating flow properties in the near wake of the rigid and flexible protruding surface in a water tunnel under the Reynolds number of 4000, 6000 and 8000. In the current study, circular finite cylinders (cantilevers) with various aspect ratios (AR = 10, 12, 14 and 16) and materials were used as the geometry of the rigid and protruding surface. The motion of the cylinder alters the fluid flow significantly. The increment of the wake region (~10 larger in the flexible cylinder compared to the rigid case, for AR = 16) is due to the weakening of the influence of downwash caused by the stream-wise deflection of the flexible cylinder. As a mean to quantify turbulence, the turbulent intensity, Ti, was studied. In general, the flexible cylinders show better capability in augmenting the turbulence than the rigid cylinder. The stream-wise turbulent intensity for AR = 16 and Re = 8000 can be as high as 97 for the flexible cylinder compared to only 26 for the rigid case. The normalized amplitude response graph, which records the cross-flow oscillation of the flexible cylinder was also analyzed. Under the same Reynolds number, the turbulence enhancement increases with the structural velocity. An organized oscillating motion is in favor of a higher performance of turbulence enhancement. © 2020 All Rights Reserved

Development of Measurement System for Flow and Shape Using Array Ultrasonic Sensors

In Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the fuel debris formed in the Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) at Unit 1 - 3. To accelerate and decide further decommissioning steps of the FDNPP, it is crucial to obtain realistic information of the debris and localize contaminated water leakage from PCV. Due to high radiation and dark environment inside the PCV, investigating instruments and techniques should necessarily to meet specification of radiation resistance, waterproofness, dust resistance and so on. This study focuses on development of ultrasonic measurement system using a couple of sectorial array sensors to localize contaminated water leakage and visualize shape of object that repre- senting fuel debris, simultaneously. In this study, Total Focusing Method (TFM) and Ultrasonic Velocity Profiler (UVP) methods are considered to visualize object shape and flow pattern around it, respectively. To demonstrate applicability and reliability of developed measurement system with sectorial array sensors, a mock-up experiment result of simulated water leakage and fuel debris shape were discussed in this paper.

Evaluation of the effect of the concentration of seeding particles on spike-excitation doppler UVP measurement

In the study of fluid flows, one of the important parameters is the spatial-temporal velocity distribution. Experimental measurement of the parameter is required for the development and validation of various models in this field. Techniques for the measurement of flow velocity at single points have been in operation with great success for many years. However, there are situations where the measured data at one point is obviously not enough to understand structures in, e.g., turbulent/transient flows. One of the well-established and powerful methods for measuring velocity distribution is the UVP - Ultrasonic Velocity Profile method that enables measurements of the instantaneous velocity profile along a measurement line, i.e. the sound path. The new application of spike excitation along with the Doppler signal processing to the UVP method has recently been successfully tested. Regarding this new method, factors influencing the measurement result require further careful investigations. This study addresses, to some extent, the effect of the seeding-particle concentration on the results of spike-excitation UVP measurements. For the investigation, experimental measurements of water pipe flow have been carefully executed for a wide range of the particle concentration. The dependence of the measured data on the particle concentration is evaluated and reported. The result of this study suggests an appropriate range of the seeding-particle concentration in setting up spike-excitation UVP measurements.

Experimental Investigation of the Flow Field in the Vicinity of an Oscillating Wave Surge Converter

The main objective of this paper is to characterize the flow field on the front face of an oscillating wave surge converter (OWSC) under a regular wave. For this purpose, the longitudinal and vertical velocity components were measured using an Ultrasonic Velocity Profiler (UVP). In order to explain the main trends of the OWSC’s dynamics, the experimental data were firstly compared with the analytical results of potential theory. A large discrepancy was observed between experimental and analytical results, caused by the nonlinear behavior of wave-OWSC interaction that determine the turbulent field and the boundary layer. The experimental velocity field shows a strong ascendant flow generated by the mass transfer over the flap (overtopping) and flow rotation generated by the beginning of the flap deceleration and acceleration. These features (overtopping and flow rotation) have an important role on the power capture of OWSC and, therefore, analytical results are not accurate to describe the complex hydrodynamics of OWSC.

De-aliasing of ultrasonic velocity profiler on bubbly flow beyond the Nyquist limit

De-aliasing of ultrasonic velocity profiler on bubbly flow beyond the Nyquist limit

Applicability Evaluation of In-line Rheometer based on Ultrasonic Velocity Profile Measurements

Applicability Evaluation of In-line Rheometer based on Ultrasonic Velocity Profile Measurements

Experimental and Numerical Investigation of Swirling Flow on Triple Elbow Pipe Layout

The secondary flow downstream of a triple elbow layout was studied experimentally and numerically to visualize the flow behavior under swirling inlet flow conditions. The inlet swirling condition was generated by a swirl generator, consisting of a rotary pipe and honeycomb assembly. The experiments were carried out in turbulent water flow condition at Reynolds number Re = 1 × 104 and inlet swirl intensity S = 1. Ultrasonic measurements were taken at four locations downstream of the third elbow. The two-dimensional velocity field of the flow field was measured using the phased array ultrasonic velocity profiler technique to evaluate the flow field with separation. Furthermore, a numerical simulation was performed and its results were compared with the experimental data. The numerical result was obtained by solving three-dimensional, Reynolds-averaged Navier-Stokes equations with the renormalization group k-ε turbulence model. The experimental results confirmed that the swirling flow condition modified the size of the separation region downstream of the third elbow. A qualitative comparison between the experimental and CFD simulation results of the averaged velocity field downstream of the third elbow showed similar tendency on reverse flow.

Development of Portable Ultrasonic Velocity Profiler and Performance Evaluation

Development of Portable Ultrasonic Velocity Profiler and Performance Evaluation

Flume Experiments on the Oscillating Wall Jet Induced by the Swing Oblique Impingement Jet

The flow characteristics of oscillating wall jets induced by swinging an oblique impingement jet in a rectangular flume is experimentally investigated. By using ultrasonic Doppler velocity profiler (UDVP), the phase-dependent velocity profiles, the phase-varying turbulence fluctuations, and the decay of the velocity along the downstream surface of the oscillating wall jets are observed in a two-dimensional plane. Results show that the mean velocity profile of the oscillating wall jet in the near-bed region generally follows the Weibull distribution, similar to the steady wall jet. Greater fluctuation magnitudes are produced by the oscillating wall jet at the low-speed provocation and high-speed suppression phases than that at the accelerating and decelerating phases. The velocity fluctuations increase with the increasing oscillating frequency. Both the oscillation offset and amplitude of the oscillating wall jet decay continuously with the spreading distance. The decay rate of oscillation offset along the downstream wall of the oscillating wall jet is higher than the velocity decay rate of steady wall jet, and slightly increases with the increment of the oscillating frequency. The oscillating amplitude decays exponentially with the downstream distance.

Cloud structuring of microbubbles ascending along a vertical wall

To elucidate the motion of spatiotemporally developing flow structures driven by densely concentrated microbubbles, we experimentally investigated the distribution and motion of microbubbles rising along a vertical plane wall. We performed optical measurements and an ultrasonic velocity profiling to determine the distribution and motion of microbubbles. We found that the microbubbles form clouds (fluid blobs containing rich microbubbles) with a three-dimensional structure, the spatial patterns of which become more periodic in the streamwise direction than in the spanwise direction. In addition, owing to the coalescence of neighboring microbubble clouds caused by the hydrodynamic interaction between them, the separation length of the buoyant force distribution of microbubbles increases with increasing the distance from the bottom of the tank. According to the Reynolds number of the microbubbles cloud presented here, we conclude that the unsteady motion of microbubble clouds can be analogously modeled as an interacting motion of moving bodies in flow.

Extension of Measurable Velocity Limit in Ultrasonic Velocity Profiler for Leakage Investigation

Extension of Measurable Velocity Limit in Ultrasonic Velocity Profiler for Leakage Investigation

Extended Short-Time Fourier Transform for Ultrasonic Velocity Profiler on Two-Phase Bubbly Flow Using a Single Resonant Frequency

This study introduces a measurement technique for simultaneous phase-separated velocity in two-phase bubbly flow. The non-invasive technique, based on an Ultrasonic Velocity Profiler (UVP), is used in order to obtain an instantaneous, separate velocity profile for both liquid and bubble. The aim of this paper is to measure each phase velocity at the same time and position it using only a single resonant frequency. To achieve this aim, extended signal processing of the Short-Time Fourier Transform (STFT) is proposed, combining with amplitude classification to analyze Doppler signal influenced from the bubbly flow. The use of developed algorithms allows the instantaneous separation of liquid and bubble velocity profiles. In this work, the developed technique is used to measure the velocity profile of bubbly flow in the vertical pipe, demonstrating the classification of liquid and bubble velocity. To confirm the accuracy of each velocity profile phase, the Particle Image Velocimetry (PIV) method is used for comparison. The results clarify that the proposed method is in good agreement with the PIV measurement. Finally, the effect of void fraction against velocity measurement of both phases was demonstrated.

Dredging Material High Efficiency Transport Technology Test by Using the Electro Magnetic Field and Development of the Technical Design Manual

As the research about increasing the efficiency of dredging soil transport, the technology ,which reduce the friction between pipe wall and fluid in the pipe and disturbed generating pipe blockage, has been developed. So for the purpose of applying this technology to real construction site, main test has been tried at the real scale test in field. As a test result, this paper will show 30% flow efficiency increasing by permitted electro magnetic force to the pipe. And test result was evaluated as a ultra sonic velocity profiler. To propose the design technique and the execution manual of the high efficiency dredging material transport technic, this research have confirmed flow status changing depending on a soil material kind under electro-magnetic field and analyze the effect of electro-magnetic field which affects to each dredged soil material transportation. For achieving this research, EMF(Electro-Magnetic Field) generator is installed on the dredger(20,000HP) and through monitored flow status , dredging soil flow rate and sampled material specification is confirmed. Also dredger operating condition is measured and dredger power for soil transportation, hydraulic gradient and flow rate are compared, as transportation efficiency is calculated by this parameter, it is possible to check transportation efficiency improvement depending on each dredged soil material under electro-magnetic field. To verify the technique of dredged soil transfer using electromagnetic field, which is the core technique of the high efficiency dredged soil transfer, and the technique of expert system for pipeline transfer and the flow state. This could lead to a verification of transfer efficiency according to the characteristics of the dredged soil (sand, clay, silt) and the transfer distance (5km, 10km, 15km), which is planned to be used for a technology development of pump power reduction and long-distance transfer applying the high efficiency dredged soil transfer technology.

Internal Structure of a Self‐Accelerating Turbidity Current

AbstractA self‐accelerating current is a particle‐driven gravity flow moving on a sloping bed whose velocity surges in the downstream direction as a result of increasing suspended sediment concentration entrained from the bed. This concept although introduced decades ago has proved elusive to be measured, but it is critical to explain the increasing evidence that turbidity currents are arguably the leading process for conveying sediments down the continental slope and beyond. It implies that both flow velocity and suspended concentration increase due to a feedback loop up to the point where some external condition restrains the process. The higher the velocity is, the larger the grain size and sediment concentration that can be kept in suspension; conversely, the denser the flow is, the faster it moves downslope. This work documents laboratory experiments of plunging (hyperpycnal) turbidity currents composed of noncohesive particles ranging from 20 to 200 μm with a specific density of 1.5. The experiments were performed in a 15‐m‐long flume with a bottom slope of 5%. Self‐acceleration of the front and body of the flow was achieved during the experiments and documented using both video recordings and ultrasonic velocity profilers (UVP). The UVP backscatter signal was calibrated with physical samples and used for estimating suspended sediment concentration profiles. The plunging mechanism played a lead role during the experiments by purging the flow from suspended material beyond its capacity and from coarse grains beyond its competence. Self‐acceleration was observed in some of the performed tests. Acceleration of the current front was clearly recorded with the video cameras, while the UVP recordings captured acceleration within the current body along the flume. The measured depth‐averaged velocity in the current body was higher than the velocity of the current front, thus indicating an internal circulation pattern that shapes the current front and head. Our experiments indicate that a supercritical flow regime is a necessary but not a sufficient condition for the occurrence of a self‐accelerating turbidity current. Whether the current self‐accelerates or not on a certain sloping bottom seems to be determined by flow discharge, concentration, size of suspended material, and availability of entrainable sediment at the bed. Deposits formed during the experiments showed that turbidites generated by self‐accelerating currents presented both less pronounced thinning and fining downstream rates than those generated by decelerating or depositional currents. This signature may be used in the sedimentary record to discern the turbidite forming flow.

Comprehensive pulsed electric field (PEF) system analysis for microalgae processing

Pulsed electric field (PEF) is an emerging nonthermal technique with promising applications in microalgae biorefinery concepts. In this work, the flow field in continuous PEF processing and its influencing factors were analyzed and energy input distributions in PEF treatment chambers were investigated. The results were obtained using an interdisciplinary approach that combined multiphysics simulations with ultrasonic Doppler velocity profiling (UVP) and rheological measurements of Arthrospira platensis suspensions as a case study for applications in the biobased industry. UVP enabled non-invasive validation of multiphysics simulations. A. platensis suspensions follow a non-Newtonian, shear-thinning behavior, and measurement data could be fitted with rheological functions, which were used as an input for fluid dynamics simulations. Within the present work, a comprehensive system characterization was achieved that will facilitate research in the field of PEF processing.