Acoustic Doppler Velocity Meter Research Articles

Characteristics of Flow over Rectangular Sharp-Crested Side Weirs

In this study, water flow over rectangular sharp-crested side weirs of various heights and widths was investigated. The distribution of the three-dimensional velocity over the crest and in the vicinity of the side weir was obtained using an acoustic Doppler velocity (ADV) meter. The structure of each component of velocity was examined separately. The velocity distributions showed that longitudinal velocity peaked near the beginning of the side weir, whereas velocity in the direction of spill flow was highest at the end of the weir. The observed values of vertical velocity showed that the direction of flow near the crest was upward, but at the highest depths, the flow direction was reversed and a downward flow was generated near the water surface. Analysis of the velocity profiles indicated that the local discharge increased along the crest of the weir; local discharge also increased as the relative width of the weir decreased. Since the angle of the spilling jet (φ) plays a large role in shaping the hydraulic characteristics of a side structure, variation in this angle was investigated, and an expression for estimating φ was developed.

Effect of different meander curvatures on spatial variation of coherent turbulent flow structure inside ingoing multi-bend river meanders

In this paper, the effect of different curvatures on the spatial variation of coherent flow structure inside two physical models with both strongly curved and mild multi-bend meanders is investigated. Three dimensional flow velocities at three sequential meanders were measured using an Acoustic Doppler Velocity meter (Micro-ADV). Three dimensions of flow velocity are classified into two major classes and eight different bursting events. The contribution probability and transition probability of each zone is calculated from experimental data. The results indicated that the effect of curvature in sequential bends was important particularly for strongly curved bends. The contribution probability of the events for strongly curved meanders with relative curvature (Rc/B) of 2.6 were found to be higher than for mild curved meanders with relative curvature (Rc/B) of 4.43. The minimum contribution probability was found in external inward interaction event. In addition, analysis of bursting events showed that the highest values of transition probabilities occurred in the stable organizations for both models. The influences of different curvatures on distributions of the Reynolds shear stress, the turbulent kinetic energy, the streamwise velocity and the vertical velocity were also shown to be in good agreement with eroded bed. The above results can be useful for finding meandering patterns inside rivers and also in river training works.

고정식 표면영상유속계 (FSIV)를 이용한 실시간 하천 유량 산정

표면영상유속계(SIV)는 영상 분석 기법을 이용하여 하천의 표면유속을 측정하고, 이를 토대로 유량을 산정하는 시스템이다. 본 연구에서는 고정식 표면영상유속계(FSIV) 시스템을 달천 수전교에 설치하여 실시간으로 연속적인 유량 측정을 실시하였다. 수전교에 적용된 FSIV의 하드웨어 시스템은 영상 획득을 위한 2대의 디지털 카메라와 컴퓨터, 그리고 수위 측정을 위한 초음파 수위계로 구성된다. 이 현장 장비들에서 획득된 실시간 영상과 수위 자료는 무선인터넷을 이용하여 실시간으로 홈페이지에 전송되며, 표면영상유속분석 소프트웨어를 이용하여 유량을 산정한다. FSIV에 의한 유량산정 결과는 직상류의 괴산댐 방류량과 FSIV와 동일한 지점에 설치된 Acoustic Doppler Velocity Meter (ADVM)를 설치한 후 유속지수법으로 산정된 유량과 비교하여 검토하였다. 댐 방류량과 비교한 결과 30<TEX>$m^3/s$</TEX> 이상의 유량에서는 대부분 5~10%의 오차를 보였으며, ADVM을 이용하여 측정된 유량과 비교한 결과는 약 200<TEX>$m^3/s$</TEX> 이상의 유량에서는 오차가 약 5 % 이내로 확인되었다. FSIV의 설치 경비와 운용에 드는 비용과 인력을 감안한다면, FSIV는 실시간으로 유량을 관측할 수 있는 좋은 대안이 될 것으로 판단된다. Surface Image Velocimetry (SIV) is a recently-developed discharge measurement instrument. It uses image processing techniques to measure the water surface velocity and estimate water discharge with given cross section. The present study aims to implement a FSIV (Fixed-type Surface Image Velocimetry) at Soojeon Bridge in the Dalcheon. The hardware system consists of two digital cameras, a computer, and a pressure-type water stage gauge. The images taken with the hardware system are sent to a server computer via a wireless internet, and analyzed with a image processing software (SIV software). The estimated discharges were compared with the observed discharges through Goesan dam spillway and index velocity method using ADVM. The computed results showed a good agreement with the observed one, except for the night time. The results compared with discharges through Goesan dam spillway reached around 5~10% in the case of discharge over 30 m3/s, and the results compared with discharges through index velocity method using ADVM reached around 5% in the case of discharge over 200 <TEX>$m^3/s$</TEX>. Considering the low cost of the system and the visual inspection of the site situation with the images, the SIV would be fairly good way to measure water discharge in real time.

Velocity Contour Weighting Method. I: Algorithm Development and Laboratory Testing

An algorithm is developed for real-time estimation of the cross-sectional average velocity of a channel flow by using an upward-looking pulsed wave acoustic Doppler velocity meters (ADVM). The Velocity Contour Weighting Method (VCWM) is applicable to gradually varied flows in prismatic channels and requires little to no calibration. VCWM estimates the average velocity as a weighted average of ADVM bin velocities. Weights are based on the velocity distribution sampled by the ADVM. Collectively, the VCWM is able to adapt to a wide range of channel geometry and roughness features. Expressions for the velocity weights are developed by first applying a validated 3D computation fluid dynamics (CFD) channel flow model to a wide range of flow scenarios including differing channel geometries, discharge rates, depths, and boundary roughness. CFD simulation data are then reduced empirically with the aid of dimensional analysis to obtain the velocity weight equation. Special attention is given to the first weight accounting for near-wall velocity where the ADVM does not measure. Application of the method to a large rectangular flume shows that the VCWM predicts the average velocity with an uncertainty less than ±5% and that this uncertainty can be reduced by minimizing the buffer distance between the channel bottom and the first velocity measurement. In a companion paper, the performance of the VCWM is examined in irrigation canals with trapezoidal cross sections.

Velocity Contour Weighting Method. II: Evaluation in Trapezoidal Channels and Roughness Sensitivity

The Velocity Contour Weighting Method (VCWM) was developed in Part I to accurately estimate the cross-sectional average velocity of a prismatic channel flow using acoustic Doppler velocity meter (ADVM) measurements of centerline velocity. Here, the VCWM is validated by its successful application to 25 different concrete-lined trapezoidal channels used for irrigation water delivery. At each site, the cross-sectional distribution of velocity is measured by an acoustic Doppler velocimeter (ADV), which is moved horizontally and vertically through a sampling grid. Multiple tests at some sites led to a total of 51 sets of cross-sectional measurements. ADVM measurements are simulated by interpolating ADV measurements along a set of vertically aligned centerline coordinates typical of ADVM deployments. Subsequent application of the VCWM gives an estimate of the cross-sectional average velocity. Secondly, the velocity-area method is applied to the ADV data to directly measure the cross-sectional average velocity f...

Experimental and numerical investigations of flow through free double baffled gates

Studying the flow patterns and behaviour of double baffled gates under different flow heads is important to improve their performance, which could help in widening the range of their application. In the present study, physical and numerical investigations were conducted on the double baffled gate. A 3D Acoustic Doppler Velocity Meter (ADV) was used for laboratory measurements of the instantaneous velocity fields in the physical gate model. In parallel with this, the CFD Fluent package was adopted to carry out a sensitivity analysis for a matrix of geometric parameters of the double baffled gate. The outcomes of the laboratory and CFD numerical investigations were incorporated in a spreadsheet with the purpose of informing the design of double baffled gates under conditions of non-submergence.

OPTIMIZING METHODS TO MEASURE HYDRODYNAMICS IN COASTAL WETLANDS: EVALUATING THE USE AND POSITIONING OF ADV, ADCP AND HR-ADCP

Hydrodynamic impacts of vegetation in the intertidal zone are highly important to coastal protection. However, most studies on hydrodynamic impacts of vegetation in the intertidal zone are carried out in flumes. This results in a lack of field data for validating models that describe short-term hydrodynamic impacts of vegetation. The current research focuses on field measurements of flow patterns and waves in vegetated intertidal areas. Ample measurement devices are available to measure hydrodynamic processes in the field. Examples are: acoustic Doppler current profilers (ADCP), high resolution acoustic Doppler current profilers (HR-ADCP) and acoustic Doppler velocity meters (ADV). This study focuses on the differences in the performance of these devices, to determine which of them can be best deployed in a future fieldwork campaign in mangroves. Major points of attention in this comparison are the accuracy of the data and the potential disturbance of the measurements by the presence of vegetation. It is concluded that ADV's perform very well in vegetated intertidal areas, while (HR-)ADCP's show difficulties when deployed upward looking. Furthermore, ADV's are preferred over (HR-)ADCP's due to their ability of combining high frequent wave and current measurements and their convenient deployment.

Turbulent kinetic energy of water in a compound channel

Turbulent kinetic energy of water in a compound channel. The aim of the experimental research was the determination of water turbulent kinetic energy changes in a compound channel without and with rigid, emergent, vegetation existing on fl oodplains. Two tests for two various roughness of fl oodplains were realized. In the fi rst test the surface of the main channel bed was smooth and made of concrete whereas the fl oodplains and sloping banks were covered by cement mortar composed with terrazzo. In the second test the covering of the fl oodplains was left as in the fi rst test but additionally emergent vegetation (trees) growing on the fl oodplains were modeled by aluminium pipes. Instantaneous velocities were measured with use of a three-component acoustic Doppler velocity meter (ADV). The infl uence of trees, located on fl oodplains, on the distributions of turbulent kinetic energy in the main channel and on the fl oodplains were presented. The distributions of turbulent kinetic energy at different water depths were described by regression equations. Vertical distributions of turbulent kinetic energy on the fl oodplains and over the banks of the main channel were divided into three zones. Over the bottom of the main channel, four zones were determined, containing the middle zone of the fl ow fi eld divided into two zones of different trends.

Turbulent Flow Measurement in Vortex Settling Basin

This paper presents the findings of an experimental study on the three-dimensional turbulent flow field in vortex settling basin. An ADV (Acoustic Doppler Velocity Meter) were used to catch 3D velocity components inside the basin. Detailed measurements of time-averaged velocity components, turbulent intensity components and turbulent kinetic energy were determined at different radial sections of chamber. Also the normalized time averaged absolute velocity of 3D components in contour type exhibition were conducted and it was found that the absolute velocity generally is influenced by u component of flow. It trends from high magnitude in basin center to the constant magnitude in basin side wall. The normalized turbulent intensity of three components was investigated individually. It was found that intensity of 3D components in vicinity of central air core is higher than other regions, decreasing by moving towards basin sidewall except for the sections that influenced directly by entrance flow jet and sidewall exiting overflow. The results of turbulence kinetic energy also had the same interpretation like turbulence intensity and affected by the same boundary conditions which cover turbulence intensity of 3 velocity components overly.

Subcritical Contraction for Improved Open-Channel Flow Measurement Accuracy with an Upward-Looking ADVM

Acoustic Doppler velocity meters (ADVMs) provide an alternative to more traditional flow measurement devices and procedures such as flumes, weirs, and stage rating for irrigation and drainage canals. However, the requirements for correct calibration are extensive and complex. A three-dimensional computational fluid dynamics (CFD) model was used to design a subcritical rapidly varied flow contraction that provides a consistent linear relationship between the upward-looking ADVM sample velocity and the cross-sectional average velocity in order to improve ADVM accuracy without the need for in situ calibration. CFD simulations validated the subcritical contraction in a rectangular and trapezoidal cross section by showing errors within +1.8 and −2.2%. Physical testing of the subcritical contraction coupled with an upward-looking ADVM in a large rectangular flume provided laboratory validation with measurement errors within ±4% without calibration.

Experimental Study of the Effects of Submerged Dikes on the Energy and Momentum Coefficients in Compound Channel

This paper aims to understand the flow structure around submerged dike in the main channel and flood plain of a compound cross section. The study undertaken to develop this understanding was carried out in a laboratory flume using a submerged vane installed at a 90 degree angle to the bank. In order to study the flow structures, the flow velocity was measured using a three-dimensional Acoustic Doppler Velocity meter (micro-ADV) with data collection rate of 50 Hz. These flow velocity measurements were taken at 500 points on a regular grid. As the tests were undertaken with turbulent flow, these conditions were subcritical. Furthermore, all the tests were undertaken using a fixed bed. The results obtained showed that the momentum transfer and the kinetic energy reduced in two directions. Also the energy and momentum coefficients decreased significantly with the installation of the submerged vane inside the main channel. Finally, streamlines were found to deviate from the side walls of channel into the main channel.

Experimental Study of the Effects of Submerged Dikes on the Energy and Momentum Coefficients in Compound Channel

This paper aims to understand the flow structure around submerged dike in the main channel and flood plain of a compound cross section. The study undertaken to develop this understanding was carried out in a laboratory flume using a submerged vane installed at a 90 degree angle to the bank. In order to study the flow structures, the flow velocity was measured using a three-dimensional Acoustic Doppler Velocity meter (micro-ADV) with data collection rate of 50 Hz. These flow velocity measurements were taken at 500 points on a regular grid. As the tests were undertaken with turbulent flow, these conditions were subcritical. Furthermore, all the tests were undertaken using a fixed bed. The results obtained showed that the momentum transfer and the kinetic energy reduced in two directions. Also the energy and momentum coefficients decreased significantly with the installation of the submerged vane inside the main channel. Finally, streamlines were found to deviate from the side walls of channel into the main channel.

Field verification of bed-mounted ADV meters

The accuracy of continuous-signal acoustic Doppler velocity (ADV) meters for gauging stream flows is examined, using a case study of nine bed-mounted ‘Starflow’ meters currently installed at a range of sites in the Pontbren catchment, Wales. The accuracy of the ADV meters was tested, under a range of velocities and depths, by comparing flow estimates with those based on a standard method of measurement with an impeller meter. The accuracy of the ADV meters was found to be poor for very low flows. For higher flows, in five concrete-lined sections, accuracy was reasonable without calibration of the ADV meter (estimates were within 20% of the current-metered flow for 68% of samples) and accuracy was good after calibration (estimates were within 20% of the current-metered flow for 93% of samples). In one natural channel, the performance after calibration was similarly good, while performance was fair to poor for two other natural channels. The predictability of the calibration results, and the reasons for the poor performance, are discussed.

Quantifying flow structure in vortex chamber using fractal dimension

The flow in a vortex chamber consists of a series of vortices with a variety of different length scales. In the present study, an effort was made to scale and quantify flow structure inside the vortex chamber. To understand the structure of flow in a vortex chamber, three dimensions of flow velocity were measured using acoustic Doppler velocity meter (ADV). The velocity of the flow was measured in a fine grid from the bed to the water surface at sections 45°, 90°, 135° and 180° in the radius of the chamber. To scale the eddies of the flow, a fractal interpolation function algorithm was used to compute fractal dimension of tangential velocity, vertical velocity and Reynolds shear stress. The variation of the fractal dimension for tangential velocity, vertical velocity and Reynolds shear stress at the depth of flow and at the distance from the center of the chamber is investigated in this study. The results indicated that no significant variation for the fractal dimension of vertical velocity fluctuation and Reynolds shear stress was found for the depth in all sections. However, the fractal dimension of tangential velocity fluctuates significantly over the depth and in the distance from the center. As a result, the averaged value of fractal dimension for tangential velocity is lower than the value of fractal dimension for vertical velocity and Reynolds shear stress. The average fractal dimensions of tangential velocity are 1.63, 1.64, 1.64 and 1.63 for the sections of 45°, 90°, 135° and 180°, respectively.

Three-dimensional fractal scaling of bursting events and their transition probability near the bed of vortex chamber

Abstract The structure of flow inside the vortex chamber is complicated and fully three-dimensional particularly near the bed of the chamber. The secondary currents inside the vortex chamber play the main role in sediment extraction. In this study, fractal dimension of 3-D bursting process was used to define the turbulent coherent structure of the flow at the bed of the vortex chamber. It is very important for the entrainment of sediment particles from the bed and moving them towards the flushing orifice. The 3-D bursting process were categorized into eight different cubic zones according to sign of 3-D velocity fluctuations. The turbulent data was measured at 48 points near the bed of chamber using three-dimensional acoustic Doppler velocity meter (ADV). A fractal interpolation function (FIF) algorithm was used to simulate more than 300,000 time series data including time series of v′, u′, ω′, v′u′ and v′ω′ for each particular cubic zone. It was found that the fractal dimensions of 3-D velocity fluctuations and tangential and radial Reynolds shear stress for eight cubic zone of 3-D bursting process are very different. The fractal dimensions of Df(v′ω′) in cubic zone of 1, 2, 3, 4, 5, 6, 7 and 8 was found to be 1.639, 1.630, 1.609, 1.586, 1.636, 1.618, 1.623, and 1.641, respectively. With the application of 1st order Markov process, transition probabilities of 64 movements were found for the measured data along the radius and at the bed of the chamber. Additionally fractal dimension of the bursting events computed for eight particular stable organizations with the transition probability of the events. The mean fractal dimension of tangential velocity fluctuation u′ for eight movements was found to be 1.667, 1.704, 1.700, 1.695, 1.709, 1.693, 1.697 and 1.689, respectively.

Fractal-Markovian scaling of turbulent bursting process in open channel flow

Abstract The turbulent coherent structure of flow in open channel is a chaotic and stochastic process in nature. The coherence structure of the flow or bursting process consists of a series of eddies with a variety of different length scales and it is very important for the entrainment of sediment particles from the bed. In this study, a fractal-Markovian process is applied to the measured turbulent data in open channel. The turbulent data was measured in an experimental flume using three-dimensional acoustic Doppler velocity meter (ADV). A fractal interpolation function (FIF) algorithm was used to simulate more than 500,000 time series data of measured instantaneous velocity fluctuations and Reynolds shear stress. The fractal interpolation functions (FIF) enables to simulate and construct time series of u ′, v ′, and u ′ v ′ for any particular movement and state in the Markov process. The fractal dimension of the bursting events is calculated for 16 particular movements with the transition probability of the events based on 1st order Markov process. It was found that the average fractal dimensions of the streamwise flow velocity ( u ′) are; 1.73, 1.74, 1.71 and 1.74 with the transition probability of 60.82%, 63.77%, 59.23% and 62.09% for the 1–1, 2–2, 3–3 and 4–4 movements, respectively. It was also found that the fractal dimensions of Reynold stress u ′ v ′ for quadrants 1, 2, 3 and 4 are 1.623, 1.623, 1.625 and 1.618, respectively.

Field Measurements and Flow Modeling of Overbank Flows in River Severn, U.K.

Field measurements of velocity and turbulence have been carried out in a study reach of the River Severn (U.K.) during overbank flows. Directional current (DCM) and acoustic Doppler Velocity (ADV) meters have been used for the field measurements of velocity and turbulence particularly in the interface region between main channel and floodplain. The values of local shear velocity and roughness length for the reach under study were calculated using measured velocity data. The distributions of turbulent intensities, and the Reynolds stresses are also presented. A two-dimensional depth averaged numerical model is used to investigate how accurately the field measurements are reproduced. A fully 3D model of the river reach is also constructed using CFX and the results are presented.

人工リーフ開口部の鉛直断面流速分布に関する実験的研究

Artificial reefs have been constructed for protecting coast form erosion and for replacing detached breakwaters. The constrictions cause topographical change around them. Main sediment transport around an opening is bed load, but suspended sediment cannot be ignored. So the experiment using 3-ADV (Acoustic Doppler Velocity Meter) was carried out to measure the vertical mean velocity distribution at a center of opening.The result of experiment shows that the return flows direction was upward at onshore, and downward at an opening. The return flows turn alternately up and down. The amplitude of mean horizontal velocity was the maximum at the bottom. Closing to water surface, the amplitudes of velocity were getting to small.

Velocity and Turbulence Measurements for Two Overbank Flow Events in River Severn

Field measurements of velocity and turbulence have been carried out in a study reach of the River Severn at Lower Farm near Shrewsbury during overbank flow. Acoustic Doppler velocity meters have been used for the field measurements of velocity and turbulence, particularly in the interface region between river channel and floodplain. The values of local shear velocity and roughness length for the reach under study were calculated using measured velocity data. The distributions of turbulent intensities, and the Reynolds stresses are also presented. The variation of horizontal shear stress in the vertical direction deviates from linear for the main channel/floodplain interaction region due to the existence of a lateral shear and momentum transfer from the floodplain towards the main channel. Comparisons are made between the field data and previous experimental data from the Flood Channel Facility.

STUDY IN BOTTOM VELOCITY DISTRIBUTION AROUND OPENING OF IMPERMEABLE ARTIFICAL REEFS

Artificial reefs have been constructed for protecting coast from erosion and for replacing detached breakwaters. The construction causes topographical change around them. Bottom flow and water surface variation and others caused topographical change. So the experiment using 3-ADV (Acoustic Doppler Velocity Meter) to measure the bottom velocity profile around opening was carried out. And the topographical change by movable bed was investigated.This study shows the result of the distribution of bottom velocity around opening. The result shows that the mean velocity of flow at offshore side of reef was different from that at shore side reef. The former region has cyclic current field. And the change of topographical flux was nearly equals to the calculation results that using the Brown's theory and incident wave conditions.