acoustic doppler velocimeter
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2021 ◽  
Vol 8 ◽  
Author(s):  
Bing Liu ◽  
Yining Chen ◽  
Tinglu Cai ◽  
Yan Li ◽  
Li Sun

Waves, currents, and related sediment transport are important factors driving the development of saltmarshes. Separating the effects of waves and currents accurately from simple field observations is a technical challenge in shallow water environments with limited inundation such as saltmarshes. In this paper, the estimation method of both wave and current information was studied mainly through the data obtained by a solely used field ADV (Acoustic Doppler Velocimeter, Vector). Phase and pressure inversion wave methods were both used to estimate wave parameters, which were then compared to synchronous observation by wave loggers at the front of a saltmarsh. Our results show that ADV is able to achieve simultaneous observations of tidal currents and waves independently. The pressure inversion wave method (r2 ∼ 0.996) is more effective than the phase method (r2 ∼ 0.876) in estimating wave energy when comparing with wave logger results. However, the former is more restricted by submergence depth and duration in field, while the latter provides cut-off frequencies for the pressure inversion wave method. Both methods can be combined to best estimate wave parameters from field ADV data. Further, hydrodynamic observation on a Scirpus mariqueter patch at the front of a saltmarsh was used as an application to indicate the importance of obtaining both wave and current information from field data. The patch was found to mainly reduce the advection of tidal currents, but it slightly increases wave energy. Therefore, it is necessary to consider the different effects of plants on tidal currents and waves simultaneously in field observations. This study confirms that ADV and associated analysis can detect waves and currents at reliable accuracy at the marsh edge, which is vital in assessing the long-term resilience of marshes to sea level rise and increased storm severity.


Author(s):  
Priyanka Gautam ◽  
T I Eldho ◽  
B. S. Mazumder ◽  
M. R. Behera

This study investigates the turbulent flow characteristics around a complex pier (CP) with elliptical pile cap, for understanding the mechanics of flow responsible for current-induced scour. The velocity data are recorded using an acoustic Doppler velocimeter (ADV) for a Reynolds number of 67,745. This study gives mean velocities in horizontal and vertical planes, Reynolds stresses, turbulent kinetic energy, and spectral analysis around the CP, which are not addressed earlier. The streamwise spectra with vortex-shedding frequencies and corresponding Strouhal numbers are focused on three distinct regions generated by CP. The elliptical pile-cap shields the downward flow at the upstream of the column, and the upward-moving wakes at the downstream of the CP, responsible for the sediment entrainment around a pier. On comparison, the effect of perturbed flow around the CP is considerably less than that of the simple pier (SP), resulting in less scour around the CP with identical flow situations.


2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Maoyi Luo ◽  
Faxing Zhang ◽  
Zhaoming Song ◽  
Liyuan Zhang

This study aimed to determine the split ratio, flow-field structure, and effect of different shaped channels to sudden pollution accidents in a generalized complex canal system of a wetland park, both experimentally and numerically. The three-dimensional instantaneous velocities at a typical section of each channel in the generalized model were measured experimentally using an acoustic Doppler velocimeter. The results showed that the split ratio calculation formula of three parallel channels could be derived under the condition of considering the frictional head and the local head losses. The water depth, velocities, and pollutant diffusion were widely influenced by changes in the cross-sectional shape and channel plane shape. The pollutants were trapped by stable vortices and transverse circulation due to shear force and secondary flow, thus delaying the diffusion of pollutants. The research results reported herein can help provide technical support for the normal operation of complex canal systems.


2020 ◽  
Vol 8 (9) ◽  
pp. 655
Author(s):  
Chunyi Zhong ◽  
Fang Yin ◽  
Junbo Zhang ◽  
Shuo Zhang ◽  
Rong Wan ◽  
...  

In the process of pond culture, the usage of an aeration device can increase dissolved oxygen density and form a decent circulation which facilitates the collection of sludge. Acoustic Doppler Velocimeter (ADV) has been widely used to monitor the flow velocity, however, factors such as bubbles and suspended particles can affect the correlation coefficient and signal-to-noise ratio of ADV, which leads to the existence of outliers in velocity data. This study constructs the three-dimensional rousseeuw phase-space (3DRPS) method by optimizing the phase space threshold method and robust estimation method through two-step filtering and three-dimensional simultaneous measurement, where the outliers close to the real value can be detected more accurately and the iterative process can be reduced more effectively. The results show that the detection rate of the optimized 3DRPS method is approximately 99%. It is a promising method that effectively improves the accuracy of outlier detection and greatly reduces the phenomenon of over processing.


Author(s):  
B Nyantekyi-Kwakye

The mean flow, turbulence characteristics, and dynamics of large-scale vortices are investigated for an offset jet issuing from different nozzle expansion ratios using a four-receiver acoustic Doppler velocimeter. The jet was discharged from sharp-edged rectangular nozzles with expansion ratios of 0.24, 0.49, 0.75, and 1.00 at Reynolds number of 5.3 × 104. The decay rate of the maximum mean velocity decreased with increasing expansion ratio due to suppressed lateral entrainment of ambient fluid. The acoustic Doppler velocimeter proved capable of providing high-quality data to investigate the energy spectrum and turbulent structures embedded in the flow. Large-scale vortices dominated the recirculation region compared to the reattachment and developing regions of the jet. Increasing the expansion ratio resulted in larger order of magnitude of the vortices within the recirculation region. The turbulent structures stretched in the lateral direction in regions where smaller-sized structures existed in the streamwise direction and vice versa.


This experimental study shows the velocity and turbulence field at vicinity of cylindrical pier with scour hole under clear water condition. The three dimensional velocity data were obtained at 5 cm, 10 cm, 20 cm and 30 cm from the pier with use of Acoustic Doppler Velocimeter at 360 degrees around the pier with 30-degree interval. The flow behaviour were extensively analyzed with the help of time averaged normalized velocity, Turbulent intensity, Turbulent kinetic energy and Reynolds shear stress plots. The study shows the flow behaviour at inside the scour hole, at scour hole ring and outside the scour hole which gives the elusive view of flow at vicinity of pier. An upstream side pier, the flow behaviour almost follows the similar trend but behind a cylinder the flow is asymmetry due to wake vortex and vortex shedding found at the wake region. This study offers an ample cognizance of flow structure at vicinity of circular pier, which is essential in order to design an effective scour control structures like rip-rap, W weir, vanes, slot and etc.,


2020 ◽  
Vol 897 ◽  
pp. 173-178
Author(s):  
Asim Kuila ◽  
Subhasish Das ◽  
Asis Mazumdar

. The flow pattern on the combined effect of a horizontal cylinder and a vertical plate is observed and analysed in this experimental study. The experiment was conducted with a 4 cm outer diameter cylinder arranged horizontally across flow above 2 cm from the bed and a vertical plate of 5 cm placed 9 cm downstream from cylinder surface reference as tilting flume bed surface. The water depth was maintained at 17 cm through a constant discharge of 35 lps in a re-circulating flume. Acoustic Doppler Velocimeter (ADV) was used to store the velocity fluctuation of velocity components and further used as a pictorial frame to understand the turbulence and the turbulent kinetic energy around the cylinder, plate and in between the cylinder - vertical plate. From the pictorial contour diagrams drawn, the velocity vector represents the flow feature over the cylinder and it is found that a horseshoe vortex, developed upstream of the plate, does effect on turbulent kinetic energy formed in between cylinder and vertical plate. The observation and obtained results from present study is compared with a 5 cm horizontal cylinder above 2 cm from the bed and a plate situated on 5.5 cm from cylinder curvature towards downstream.


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