The present work experimentally analyses the flow behaviour near the T-shaped spur dike field with no seepage, 5%, and 10% downward seepage. Experiments were aimed at analysing the channel morphology ...with different discharges. According to the results, downward seepage movement causes significant modification in the channels bed elevation and the development of scour depth. The maximum scour depth is observed at the edge of the first spur dike facing the flow. The rate of scouring also increases with the effect of seepage. Due to downward seepage, the flow distribution is shifted near the channel bed. However, near the channel boundary attained some velocity, significantly enhancing the sediment transport rate. The wake zone between the spur dikes saw very low-velocity magnitudes of positive and negative values. This reveals secondary current generation inside the loop and cross-stream circulation. With an increment of seepage percentage, the velocity, Reynold shear stress, and turbulent kinetic energy magnitude also rise close to the channel's boundary.
The present work investigates the combined effects of the upstream sediment mining pit and vegetation on the riverbank using emergent rigid vegetation beyond the toe on the flow structure and ...morphological changes due to fluvial erosion. A steep gradient of streamwise velocity and other turbulence parameters such as Reynolds shear stress (RSS), transverse RSS, and turbulent kinetic energy (TKE) at the interface of the vegetated and unvegetated part of the test segment was observed. The cross-sectional analysis showed that vegetation increased the velocity of the unvegetated main channel, and the sandpit increased even the near-bed velocity with a similar trend in its longitudinal variation at the center line of the main channel. The abrupt variation in RSS and transverse RSS at the location of the berm induces instability and erodes the berm present at the toe of the riverbank. The combination of the vegetation and sandpit led to increased TKE of the flow at the near-bed and berm locations. The morphological analysis showed complete riverbank erosion in both cases of the unvegetated riverbank, i.e., without or with an upstream pit. The installed stems of rigid vegetation on the riverbank helped decrease the fluvial erosion of the riverbank, and its profile observed minimal changes over the length of the test segment. However, the main channel erosion was amplified due to the vegetation (in no-pit case) at the beginning of the test segment, which eroded the bed of the main channel by about 67% of the bed thickness. Also, in the vegetated riverbank cases, the upstream pit caused an increase in erosion by 7.66% at the center of the main channel. The study helps establish the hypothesis of negating the effects of sediment mining on bank erosion by using the rigid vegetation on the riverbank beyond its toe location, which performed well by maintaining the riverbank profile.
ABSTRACTThe successful stabilization of riverbanks and the construction of sustainable foundations, extensive knowledge of the scour process and accurate assessment of scour depth around spur dikes ...are required. This study focuses on optimizing the spur dike shape to manage flow turbulence effectively and minimize local scour while considering the impact of downward seepage. The investigation was conducted within an experimental flume featuring a mobile bed under a clear water regime and the provision for downward seepage. The investigation concentrated on three distinct spur dike shapes (T, L, and rectangular) under different seepage velocities (VS1 and VS2) and a no-seepage condition. The current study also illustrates changes in bed morphology, temporal evolution and longitudinal profile of scour depth with and without downward seepage. The results reveal that the downward seepage intensifies the motion of sediment particles, and more seepage leads to an escalated particle detachment, resulting in deeper scour depressions. The T-shaped spur dikes exhibited the lowest scour depths compared to the other shapes, both with and without seepage. The negative impact on velocity and RSS magnitude was observed at the near channels bed where maximum scour depth was achieved. This phenomenon is closely linked to horseshoe vortices’ formation and current generation. These factors play a pivotal role in the detachment of particles from the base of the structure.
The present study demonstrates the efficacy of information entropy for the development of water quality index (WQI) for irrigation purpose and its application on Bharalu River. Water quality for ...irrigation suitability was assessed by using derived parameters such as permeability index (PI), Kelly’s ratio (KR), magnesium adsorption ratio (MgR), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), and residual sodium carbonate (RSC) using annual data from April’2008 to April’2013 and April’2016, April’2017 over a period of 8 years. Values obtained in the study varied from 1.85 to 39.35% for SSP, 0.08 to 1.37 for SAR, 31.7–60.0% for MgR, 0.0–5.45 for RSC, 0.33–2.36% for PI, an 0.01–0.52 for KR. The derived parameters values indicate that water of Bharalu River is suitable for irrigation except April’2008 and April’2011. United States Salinity Laboratory (USSL) and Wilcox diagrams were used for categorizing of water quality. USSL and Wilcox diagrams categorized the water samples as S1-C2 and S1-C3, and ‘Excellent to Good’ and ‘Good to Permissible’ respectively, which suggest River Bharalu’s irrigation suitability. Entropy weighted irrigation water quality index (EIWQI) has been proposed and applied on Bharalu River data for assessing its suitability and variability for irrigation. EIWQI was found to be less than 1 for all the years except April’2011, which showed its appropriateness for irrigation. This study can be of great help for policymakers and researchers to effectively manage water resources.
We present Python Statistical Analysis of Turbulence (P-SAT), a lightweight, Python framework that can automate the process of parsing, filtering, computation of various turbulent statistics, spectra ...computation for steady flows. P-SAT framework is capable to work with single as well as on batch inputs. The framework quickly filters the raw velocity data using various methods like velocity correlation, signal-to-noise ratio (SNR), and acceleration thresholding method in order to de-spike the velocity signal of steady flows. It is flexible enough to provide default threshold values in methods like correlation, SNR, acceleration thresholding and also provide the end user with an option to provide a user defined value. The framework generates a .csv file at the end of the execution, which contains various turbulent parameters mentioned earlier. The P-SAT framework can handle velocity time series of steady flows as well as unsteady flows. The P-SAT framework is capable to obtain mean velocities from instantaneous velocities of unsteady flows by using Fourier-component based averaging method. Since P-SAT framework is developed using Python, it can be deployed and executed across the widely used operating systems. The GitHub link for the P-SAT framework is: https://github.com/mayank265/flume.git .
Abstract
Experiments were performed to examine the variations in flow turbulence with respect to sand and gravel bed channel. The 3D instantaneous velocity of water is measured by acoustic doppler ...velocimeter (ADV) at the test section, which will provide an important data related to the flow turbulence. The parameters of turbulence measured that the vertical profiles of longitudinal velocity in flows with a sand bed channel at the vicinity of the bed surface are higher by 2–6% than flow subjected to gravel bed channel, while away from the boundary surface, it decreases by 5–10%. The variations of Reynolds shear stress increase by 35–50% with gravel bed channel, indicating higher exchange of flow energy towards the boundary and vice versa. The higher value is obtained for shear velocities by 58.5% and the von Karman's constant with gravel bed channel. The gravel bed channel influenced the turbulence intensities with higher magnitude in the streamwise and vertical direction. The present study also analysed the flow anisotropy, correlations coefficient and turbulence diffusivity and compared the results. The outcomes of the current work are beneficial for civil and hydraulic engineers, since the data of turbulence will advance the management of bed materials present in the river.
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