scholarly journals Application of an Entropic Method Coupled with STIV for Discharge Measurement in Actual Rivers

2021 ◽  
Vol 945 (1) ◽  
pp. 012036
Author(s):  
Yoshiro Omori ◽  
Ichiro Fujita ◽  
Ken Watanabe
Keyword(s):  
Velocity Distribution ◽  
Flow Velocity ◽  
River Flow ◽  
Measurement Techniques ◽  
Vertical Direction ◽  
Acoustic Doppler Current Profiler ◽  
Surface Flow ◽  
Surface Velocity ◽  
Cross Sectional ◽  
Current Profiler

Abstract In recent years, due to the frequent occurrence of floods that exceed the facility maintenance level due to climate change, non-contact flood flow measurement techniques have been paid attention and actually some measurements have been conducted by applying them instead of the conventional float method. The space-time image velocimetry (STIV) which can measure the surface flow velocity distribution from video images is one of such techniques. In order to calculate the river flow from the surface velocity distribution, it is necessary to determine an appropriate surface velocity coefficient, which is the ratio of the average depth velocity to the surface velocity. However, at present, empirical default value has been still used in practice. In this study, the cross-sectional velocity distribution was calculated using an entropic method by utilizing the surface velocity distribution measured by STIV and compared with Acoustic Doppler Current Profiler (ADCP) observation. It was confirmed that the introduction of the velocity dip system express the flow velocity distribution in the vertical direction, where the velocity dip occurs due to the influence of vegetation.

scholarly journals Monitoring of Yangtze River Discharge at Datong Hydrometric Station Using Acoustic Tomography Technology

2021 ◽  
Vol 9 ◽  
Author(s):  
Ze-Nan Zhu ◽  
Xiao-Hua Zhu ◽  
Chuanzheng Zhang ◽  
Minmo Chen ◽  
Hua Zheng ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Yangtze River ◽  
Acoustic Doppler Current Profiler ◽  
Acoustic Tomography ◽  
The Yangtze River ◽  
Cross Sectional ◽  
Extreme Flood ◽  
Current Profiler ◽  
The Mean ◽  
Hydrometric Station

To continuously monitor the discharge of the Yangtze River, two coastal acoustic tomography (CAT) systems with synchronized transmission were deployed at the Datong hydrometric station of the Yangtze River from July 2018 to January 2021. To accurately estimate the discharge of the Yangtze River, the cross-sectional averaged flow velocity and area data were estimated by establishing two empirical relationships: one between the range-averaged flow velocity measured by acoustic Doppler current profiler (ADCP) and the reciprocal travel time difference measured by CAT, and the other between the ADCP-measured cross-sectional area and the water-surface elevation (stage). Compared with the discharges directly measured by ADCP, our estimation had the root mean square error of 946 m3/s, accounting for 2.5% of the mean discharge. The discharges varied from 10,981 to 81,807 m3/s over the 2.5-years observational period, with a mean of 30,708 m3/s. The annual mean discharge was 29,163 and 34,763 m3/s in 2019 and 2020, respectively. Our monitoring successfully covered two complete flood processes, with a peak discharge of 69,744 (July 17, 2019) and 81,807 m3/s (July 13, 2020). Our study provides an innovative method to achieve accuracy and real-time monitoring of river discharges even during extreme flood events.

scholarly journals Inovasi Dan Desain Turbin Hidrokinetik Darrieus Berdasarkan Bentuk Distribusi Kecepatan Aliran

2020 ◽  
Vol 9 (1) ◽  
pp. 32-43
Author(s):  
Citra Sari Wardani ◽  
Dwi Anung Nindito ◽  
Allan Restu Jaya
Keyword(s):  
Velocity Distribution ◽  
Flow Velocity ◽  
Lift Force ◽  
Vertical Direction ◽  
Performance Comparison ◽  
Cross Sectional ◽  
Straight Line ◽  
Torque Values ◽  
Turbine Design ◽  
Spinning Top

Darrieus turbine use blades with a hydrofoil shape, so the rotational ability is influenced by lift force. This caused the initial rotation capability to be very low when compared to the drag turbine type. The flow velocity distribution in the vertical direction indicates a small cross-sectional speed of flow approaching the base of the flow channel, then rising towards the surface. Darrieus Spinning Top turbine is the result of innovation and design based on the concept of flow velocity distribution. Darrieus Spinning Top turbine’s blade shapes are circular-arc and straight-line, adjusting flow velocity distribution of 0.2H, 0.6H and 0.8H from the top of the turbine. In this study, a performance comparison was conducted between Darrieus turbine and Spinning Top Darrieus. Darrieus turbines produce RPM and torque values of 54.59 – 67.90 and 0.014 – 0.029 Nm, respectively. Darrieus Spinning Top turbines produce RPM values and torque of 69.24 – 82.02 and 0.012 – 0.020 Nm respectively. RPM improvements in Darrieus Spinning Top turbine design increase the influence of lift force (increased λ value). This results in a high lap rate, but requires a high self starting to perform the turbine rotation cycle.

scholarly journals Sea-ice growth and water-mass modification in the Mertz Glacier polynya, East Antarctica, during winter

2001 ◽  
Vol 33 ◽  
pp. 399-406 ◽  
Author(s):  
N. L. Bindoff ◽  
G. D. Williams ◽  
I. Allison
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Fresh Water ◽  
Acoustic Doppler Current Profiler ◽  
Water Masses ◽  
Surface Velocity ◽  
Return Flow ◽  
Shelf Water ◽  
Ice Growth ◽  
Current Profiler

AbstractIn July-September 1999, an extensive oceanographic survey (87 conductivity-, temperature-and depth-measuring stations) was conducted in the Mertz Glacier polynya over the Adélie Depression off the Antarctic coast between 145° and 150° E. We identify and describe four key water masses in this polynya: highly modified circumpolar deep water (HMCDW), winter water (WW), ice-shelf water (ISW) and high-salinity shelf water (HSSW). Combining surface velocity data (from an acoustic Doppler current-profiler) with three hydrographic sections, we found the HMCDW to be flowing westward along the shelf break (0.7 Sv), the WW and HSSW flowing eastwards underneath Mertz Glacier (2.0 Sv) and that there was a westward return flow of ISW against the continent (1.2 Sv). Using a simple box model for the exchanges of heat and fresh water between the principal water masses, we find that the polynya was primarily a latent-heat polynya with 95% of the total heat flux caused by sea-ice formation. This heat flux results from a fresh-water-equivalent sea-ice growth rate of 4.9−7.7 cm d−1 and a mass exchange between HMCDW and WW of 1.45 Sv The inferred ocean heat flux is 8−14 W m−2 and compares well with other indirect estimates.

scholarly journals Discharge Estimation Using Tsallis and Shannon Entropy Theory in Natural Channels

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1786
Author(s):  
Jitendra Kumar Vyas ◽  
Muthiah Perumal ◽  
Tommaso Moramarco
Keyword(s):  
Flow Velocity ◽  
Surface Flow ◽  
Tsallis Entropy ◽  
Accurate Estimation ◽  
Mean Flow ◽  
Flow Area ◽  
Cross Sectional ◽  
The Cross ◽  
Discharge Estimation ◽  
Mean Flow Velocity

Streamflow measurements during high floods is a challenge for which the World Meteorological Organization fosters the development of innovative technologies for achieving an accurate estimation of the discharge. The use of non-contact sensors for monitoring surface flow velocities is of interest to turn these observed values into a cross-sectional mean flow velocity, and subsequently, into discharge if bathymetry is given. In this context, several techniques are available for the estimation of mean flow velocity, starting from observed surface velocities. Among them, the entropy-based methodology for river discharge assessment is often applied by leveraging the theoretical entropic principles of Shannon and Tsallis, both of which link the maximum flow velocity measured at a vertical of the flow area, named the y-axis, and the cross-sectional mean flow velocity at a river site. This study investigates the performance of the two different entropic approaches in estimating the mean flow velocity, starting from the maximum surface flow velocity sampled at the y-axis. A velocity dataset consisting of 70 events of measurements collected at two gauged stations with different geometric and hydraulic characteristics on the Po and Tiber Rivers in Italy was used for the analysis. The comparative evaluation of the velocity distribution observed at the y-axis of all 70 events of measurement was closely reproduced using both the Shannon and Tsallis entropy approaches. Accurate values in terms of the cross-sectional mean flow velocity and discharge were obtained with average errors not exceeding 10%, demonstrating that the Shannon and Tsallis entropy concepts were equally efficient for discharge estimation in any flow conditions.

Remote sensing flow velocity of debris-covered glaciers using Landsat 8 data

2015 ◽  
Vol 40 (2) ◽  
pp. 305-321 ◽  
Author(s):  
Lydia Sam ◽  
Anshuman Bhardwaj ◽  
Shaktiman Singh ◽  
Rajesh Kumar
Keyword(s):  
Remote Sensing ◽  
Flow Velocity ◽  
Accuracy Assessment ◽  
Geographical Area ◽  
Surface Flow ◽  
Velocity Estimation ◽  
Surface Velocity ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Glacier Velocity

Changes in ice velocity of a glacier regulate its mass balance and dynamics. The estimation of glacier flow velocity is therefore an important aspect of temporal glacier monitoring. The utilisation of conventional ground-based techniques for detecting glacier surface flow velocity in the rugged and alpine Himalayan terrain is extremely difficult. Remote sensing-based techniques can provide such observations on a regular basis for a large geographical area. Obtaining freely available high quality remote sensing data for the Himalayan regions is challenging. In the present work, we adopted a differential band composite approach, for the first time, in order to estimate glacier surface velocity for non-debris and supraglacial debris covered areas of a glacier, separately. We employed various bandwidths of the Landsat 8 data for velocity estimation using the COSI-Corr (co-registration of optically sensed images and correlation) tool. We performed the accuracy assessment with respect to field measurements for two glaciers in the Indian Himalaya. The panchromatic band worked best for non-debris parts of the glaciers while band 6 (SWIR – short wave infrared) performed best in case of debris cover. We correlated six temporal Landsat 8 scenes in order to ensure the performance of the proposed algorithm on monthly as well as yearly timescales. We identified sources of error and generated a final velocity map along with the flow lines. Over- and underestimates of the yearly glacier velocity were found to be more in the case of slow moving areas with annual displacements less than 5 m. Landsat 8 has great capabilities for such velocity estimation work for a large geographic extent because of its global coverage, improved spectral and radiometric resolutions, free availability and considerable revisit time.

Hydromorphological monitoring of individual river reaches with UAV-data – image-based measurement of bathymetry and flow velocity

2021 ◽  
Author(s):  
Anette Eltner ◽  
László Bertalan ◽  
Eliisa Lotsari
Keyword(s):  
Flow Velocity ◽  
Acoustic Doppler Current Profiler ◽  
Surface Flow ◽  
Ease Of Use ◽  
Morphological Data ◽  
Measurement Tool ◽  
River Channels ◽  
Spatiotemporal Resolution ◽  
Morphodynamic Modelling ◽  
Flow Velocities

<p>Unmanned Aerial Vehicles (UAV) have become a commonly used measurement tool in geomorphology due to their affordable cost, flexibility, and ease of use. They are regularly used in fluvial geomorphology, among other fields, because the high spatiotemporal resolution of UAV data makes it possible to assess the continuum rather than relying on single samples.</p><p>In this study, UAV data are used to hydro-morphologically describe three different river reaches of lengths between 150 and 1000 m. Specifically, the surface flow velocity and bathymetry of the rivers were reconstructed. The flow velocities were calculated using the Particle Tracking Velocimetry (PTV) method applied to UAV video sequences. In addition, UAV-based imagery was acquired to perform 3D reconstruction above and below the water surface using SfM (Structure from Motion) photogrammetry, taking into account refraction effects as well as frame processing to increase the visibility of underwater features. Reference data for flow velocities were generated at selected positions using current meters as well as ADCP (Acoustic Doppler Current Profiler) readings. The image-based calculated bathymetry was compared with RTK-GNSS sampling depth measurements and also ADCP data.</p><p>The developed workflow enables rapid and regular measurement of hydrological and morphological data of river channels. This ultimately enables multi-temporal assessment and significantly improves hydro-morphodynamic modelling, in particular their calibration.</p>

Flow and Stratification in a Bedrock Confined Estuary

2021 ◽  
Author(s):  
Amanda Wild ◽  
Eva Kwoll
Keyword(s):  
River Estuary ◽  
Acoustic Doppler Current Profiler ◽  
Limited Information ◽  
Cross Sectional ◽  
Current Profiler ◽  
Hydrodynamic Processes ◽  
Ongoing Development ◽  
Skeena River ◽  
The Impact ◽  
Temperature Depth

<p>This research describes the impact of the bedrock island structure on the circulation and stratification of a macrotidal, partially mixed estuary in northwestern Canada (the Skeena River Estuary). Due to ongoing development in this formerly remote region, pressures have increased within the Skeena River Estuary over the past decade. However, there is still limited understanding of the estuary's morphodynamics due to its deviation from a 'typical' estuarine morphology. Located along an emergent, fjordal coastline, the Skeena Estuary River drains into a basin confined by bedrock and interrupted by multiple, irregular bedrock islands. Observations suggest that a subaqueous delta, associated facies, and the surface plume are split between several bedrock passages with limited information on the governing hydrodynamic processes. To overcome this, Acoustic Doppler current profiler cross-sectional transects and conductivity, temperature, depth, and turbidity profiles were taken in the nearshore (under 40 m) at locations across the estuary over two different (by ~1000 m<sup>3</sup>s<sup>-1</sup>) river stages. Over multiple dates with various river inflows, the tidal ratio to river inflow produces varied stratification patterns at a given site. During one point in time and river stage, bedrock passages are disproportionally exposed to marine and fluvial inflows, creating spatially diverse stratification patterns across the estuary. Stratification and passage morphology interactions determine the characteristics of tidal slack transitions, with horizontal and vertical separation occurring during well-mixed conditions and stratified conditions, respectively.</p>

Wind effect on image-based river surface velocity measurements

2020 ◽  
Author(s):  
Salvador Peña-Haro ◽  
Beat Lüthi ◽  
Robert Lukes ◽  
Maxence Carrel
Keyword(s):  
River Flow ◽  
Surface Flow ◽  
Surface Velocity ◽  
Low Flow ◽  
Wind Effect ◽  
Rhine River ◽  
Average Wind Speed ◽  
Flow Measurements ◽  
Average Wind ◽  
Flow Velocities

<p>Image-based methods for measuring surface flow velocities in rivers have several advantages, one of them being that the sensor (camera) is not in contact with the water and its mounting position is very flexible hence there is no need of expensive structures to mount it. Additionally, it is possible to measure the whole river width. On the other hand, environmental factors, like wind, can affect the surface velocity and the have an impact on the accuracy of the measurements.</p><p><span>Herein we present an analysis of the wind effect on </span><span>the image based surface velocity at </span><span>Rhine river</span><span>, at the border between Switzerland and Austria. At this location the river width is of approximately 100 meters under low flow conditions, while the width of its floodplain is of about 200 m. </span><span>A</span><span>n</span> <span>ATMOS 22 ultrasonic anemometer </span><span>was installed </span><span>at the site to measure the wind </span><span>intensity</span><span> as well as </span><span>its</span><span> direction. </span></p><p><span>A time series of flow velocities and wind </span><span>from May to October 2019 </span><span>was analyzed. During this period, the </span><span>average disch</span><span>a</span><span>rge </span><span>was </span><span>320 m</span><sup><span>3</span></sup><span>/s and the average </span><span>flow </span><span>velocity 1.7 m/s. While the average wind velocity was of </span><span>2</span><span>.</span><span>3</span><span>m/s which roughly follows the same direction of the river flow.</span></p><p>A rating curve following a power law function was fitted to the image based surface flow measurements. It was found that for maximum wind speeds of 10 m/s, blowing in the opposite direction of the river flow, there was a deviation of 8%. For the average wind speed of 2.3m/s, the deviation was found to be 3%.</p>

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