Papers by Rajkumar Raikar
Book Publisher International (a part of SCIENCEDOMAIN International), Jul 8, 2021
Book Publisher International (a part of SCIENCEDOMAIN International), May 14, 2022
In this case study, Daily Rainfall Data (1984-2019) of SambraRaingauge station in North Karnataka... more In this case study, Daily Rainfall Data (1984-2019) of SambraRaingauge station in North Karnataka is used. An attempt was made to fit various probability distribution functions to the datasets of 1 day and 2 to 5 consecutive days annual maximum rainfall. The goodness of fit of probability distribution functions were tested by comparing the Chi-square (χ 2) values. No single probability distribution was adequate to describe the entire datasets. Various trendlines were also fitted to the rainfall datasets mentioned above; the best fit was decided based on the value of coefficient of determination R 2 , no single trendline equation was able to describe the entire datasets. The magnitudes of 1 day as well as 2 to 5 consecutive days annual maximum rainfall corresponding to 2 to 100 years return period were estimated best fit distribution function, it was found that even though Normal distribution function had low Chi-square value comparatively, it cannot be used overall for estimation of rainfall values of different return periods for all the datasets. Rainfall was also estimated by best fit trendline equation i.e.polynomial 3 rd order, for all the datasets corresponding to 2 to 100 years return period. It was observed the rainfall values predicted for 100 years return period for 1 to 5 consecutive days maximum rainfall were extremely high and unrealistic with respect to climate conditions of Sambra region. Chi-square test (χ 2) was conducted between observed rainfall and predicted rainfall by different trendline equations to ascertain the bestfit as determined by R 2 , it was not able to establish the same results as determined by coefficient of determination.
Book Publisher International (a part of SCIENCEDOMAIN International), Jun 21, 2022
Journal of Marine Science and Technology, Aug 1, 2013
This paper presents the use of genetic programming (GP) as a tool to predict pier scour depths ba... more This paper presents the use of genetic programming (GP) as a tool to predict pier scour depths based on clear-water conditions of laboratory measurements by past researchers. Four main dimensionless parameterspier width, approaching flow depth, threshold flow velocity, and channel open-ratio are considered for predicting the scour depth. The performance of the GP equation is verified by comparing the results with those obtained by empirical equations. It is found that the scour depth at bridge piers can be efficiently predicted using the GP model. The advantage of the GP model is confirmed by comparing the GP results of scour depths with the largescale model studies and field data.
The occurrence of heavy metals in the environment, which are known to be toxic and non-biodegrada... more The occurrence of heavy metals in the environment, which are known to be toxic and non-biodegradable, has become a serious issue. As the conventional methods of removal of heavy metals are expensive, the use of alternative treatment methodologies has become the subject of importance. This paper presents the results of an experimental study undertaken to evaluate the potential of utilizing natural adsorbents to remove chromium from the aqueous solutions through adsorption process. The natural adsorbents used in the study are orange peel, tamarind shell (oxalic acid and HCl treated) and tridax procumbens. The synthetic wastewater is used in this study. The efficiency of the activated carbon of the biomaterials for Chromium VI (Cr (VI)) removal was evaluated by varying the contact time, quantity of adsorbent and concentration of Cr (VI) in synthetic solution. It is found that the maximum removal efficiency of 92.86% of Cr (VI) in achieved by using orange peel adsorbent, 98% removal eff...
Journal of Marine Science and Technology, 2014
This paper presents the theoretical equations for the impact characteristics of free over-fall (I... more This paper presents the theoretical equations for the impact characteristics of free over-fall (ICFOF) in the pool zone with sloping upstream bed. The various impact characteristics considered are the brink depth, the impact position and impact angle, the tail water depth and the depth of water pool. In order to overcome the complexity in determining the ICFOF, they were expressed in dimensionless forms as functions of upstream bed slope (UBS), upstream Froude number and Drop number. The multiple regression analysis was used to obtain the empirical expressions for the ICFOF using the laboratory experimental results. It was found that the dimensionless brink depth decreases with an increase in upstream Froude number and UBS. With the increase in both the Drop number and UBS, the dimensionless impact position increases, while the impact angle decreases. On the other hand, the dimensional tail water depth and the dimensional depth of water pool vary directly with the Drop number and in...
International Journal of Applied Science and Engineering Research, 2012
In general concrete is a brittle material having low tensile strength and is prone to cracking. T... more In general concrete is a brittle material having low tensile strength and is prone to cracking. The increase in compressive strength of High Strength Concrete (HSC) not only increases brittleness but also reduces the ductility of the concrete. The introduction of steel or polymeric fibers in HSC improves the ductility. In this context, the paper presents the results of the experimental study on the strength parameters of Steel Fiber Reinforced HSC such as compressive strength, split tensile strength and flexural strength. The HSC used M60 grade with steel fibers added by volume in the range of 0 to 2.5% with an increment of 0.25%. The length of fibers was 25 mm to 80 mm. The experimental results were used to develop Artificial Neural Network (ANN) model for the prediction of strength parameters. It was observed that the ANN model with 2-16-3 architecture trained with Levenberg-Marquardt rule resulted into satisfactory performance for the prediction of strength parameters. Further regression models were also developed based on the experimental data. It was found that all the three strength parameters increase with an increase in percentage of steel fibers. However, the compressive strength increases with increase in fiber length from 25 mm to 50 mm and then decreases when the fiber length becomes 80 mm, while the split tensile strength increases with increase fiber length. On the other hand, flexural strength shows mixed trend.
Journal of Remote Sensing & GIS, Jan 2, 2018
Usage of groundwater for domestic and industrial purposes poses a main intimidation to the rapidl... more Usage of groundwater for domestic and industrial purposes poses a main intimidation to the rapidly depleting groundwater resources of India. The present work emphasizes the viability of remote sensing and geographic information system (GIS) applications in groundwater studies, especially in the identification of groundwater potential zones in Bangalore urban and rural districts, Karnataka, India, using composite suitability index (CSI) method. The CSI technique is used to determine the weights of different themes and their modules for recognizing the groundwater prospective zone. Each class or unit of every thematic layer was assigned a knowledge based ranking, depending on its significance. Then all thematic layers were overlaid through overlay process/method in Arc GIS environment. Five categories of groundwater potential zones, namely, good, good-moderate, moderate, moderate-poor and poor were identified and delineated. The obtained ground water potential zone map will be used to furtherance the urban and rural water supply plan in the Bangalore urban and rural areas. Keywords: Groundwater potential identification, composite suitability index, GIS and remote sensing Cite this Article Revathy SS, Suresh Babu S, Raikar RV. Composite Suitability Index (CSI) Method for Ground Water Potential Identification: A Case Study for Bangalore Urban and Rural District, Karnataka. Journal of Remote Sensing & GIS. 2017; 8(3): 8–16p.
Journal of Marine Science and Technology, Jun 1, 2018
An optic-based method that utilizes the particle-laden images captured during high-speed particle... more An optic-based method that utilizes the particle-laden images captured during high-speed particle image velocimetry (HSPIV) measurements is presented, aiming to explore the probabilistic mean characteristics of the free surface profiles and velocity fields of a free jet with high-frequency random fluctuations over a chute. The technique based on the gray-level gradients in the smoothed gray level distribution of the contrast-enhanced images is used to determine the probabilistic mean features of the free jet, right beneath and above which the water-air interfaces have I%/(100 I)% intermittent appearance of air/water phase and (100 I)% /I % fitful show-up of water/air phase. Further, the cross-correlation calculation for HSPIV measurements is employed to obtain the instantaneous and probabilistic mean velocity fields of the free jet. A target experiment of the free jet having a mean water-depth of 2.76 cm and a Froude number of 3.92 over a 17 chute model is performed in a re-circulating water channel to demonstrate the application of this method. The entire process for obtaining the probabilistic mean positions of the free surface profiles is elucidated step-by step. The lower/upper part of the free surface changing from the height at which the possibility of intermittent appearance of water phase is 3% /97%, via the counterpart for 50% /50%, to that for 97% / 3% is identified precisely. In addition, the probabilistic mean velocity field is further categorized into the conditionally and overall time-averaged ones. Each streamwise velocity profile in the conditionally time-averaged velocity field is fairly uniform. However, the counterpart in the overall time-averaged velocity field evidently shows the non-uniform feature with prominent velocity gradient in the lower/upper part between the height at which the possibility of intermittent appearance of water phase is 3% /97% and the counterpart is 97% /3%.
Journal of Marine Science and Technology, Dec 1, 2015
Experimental results on the flow characteristics of bottom boundary layer induced by a solitary w... more Experimental results on the flow characteristics of bottom boundary layer induced by a solitary wave propagating over a horizontal bottom are presented. Particle-trajectory flow visualization technique and high-speed particle image velocimetry (HSPIV) were used to elucidate detailed velocity fields underneath solitary waves with the ratios of wave height to water depth from 0.130 to 0.386. The results show that the velocity profiles can be classified into two classes with respect to the passage of the solitary wave-crest at the measuring section: the pre-passing and post-passing phases. For the pre-passing phase, the velocity distributions can be deduced to a unique similarity profile with the use of unsteady free stream velocity and time-dependent boundary layer thickness as the characteristic velocity and length scales. On the other hand, the similarity profile for the flow reversal, acting like an unsteady wall jet, is obtained from the velocity distributions during the post-passing phase. The velocity deficit between the unsteady free stream velocity and the maximum negative velocity as well as the (time-dependent) thickness of reversal flow were identified as the characteristic velocity and length scales, respectively.
AIP Advances, Nov 1, 2020
This study presents experimental data on the hydrodynamic features of a nonlinear solitary wave o... more This study presents experimental data on the hydrodynamic features of a nonlinear solitary wave of height H0 = 2.9 cm propagating over a horizontal bed in otherwise still water depth h0 = 8.0 cm. High-speed particle image velocimetry is used to quantify the local and convective particle accelerations and pressure gradients under the solitary wave. It is found that the magnitudes of the horizontal and vertical particle local accelerations are invariably larger than their convective counterparts, highlighting the important contribution of local acceleration to the pressure gradient in a solitary wave. The dimensionless pressure gradient in the horizontal direction is favorable, zero, and adverse for time before, at, and after the wave crest passes the section of interest. The dimensionless adverse pressure gradient exhibits a maximum for the dimensionless time T[=t(g/h0)1/2, where g is the gravitational acceleration and t is the time with respect to the crest passing the section] = 1.39, at which the dimensionless local acceleration has a negative maximum. Subsequently, flow reversal takes place above the bed surface. The relationship is elucidated between flow reversal at the bed surface and the evolution of the adverse pressure gradient in the near-bed zone, where uniform horizontal/free stream velocity exists.
Fluid Structure Interaction VII, 2013
The velocity-field characteristics of time-dependent horseshoe vortex flow at the juncture of an ... more The velocity-field characteristics of time-dependent horseshoe vortex flow at the juncture of an upright square cylinder and a base plate, which is subjected to an unsteady dam-break flow, were investigated experimentally. Flow visualization techniques and high-speed particle image velocimetry (HSPIV) were used to explore both qualitatively and quantitatively the unsteady feature of the flow field of horseshoe vortex structure at the juncture of square cylinder and base plate, respectively. The characteristics of the evolutionary horseshoe vortex system were analyzed, including the position of primary vortex core, down-flow velocity profile and the circulation of primary horseshoe vortex. The results show that air bubble entrains into the vortex centre in front of the model only in the cases with model-width varying from 3.0 cm to 5.0 cm. When the model width increases, the bubble entraining to the vortex centre occurs earlier. The results also show that the down-flow velocity profiles are highly affected by the vortex structures. The relationship between flow characteristics and the time duration after the gate is open is obtained by using regression analysis. The similarity of the position of the down-flow is presented with dimensionless length and dimensionless velocity as length and velocity scales, respectively.
Flow Measurement and Instrumentation, 2016
This paper emphasizes on the application of soft computing tools such as artificial neural networ... more This paper emphasizes on the application of soft computing tools such as artificial neural network (ANN) and genetic algorithm (GA) in the prediction of scour depth within channel contractions. The experimental data of earlier investigators are used in developing the models and ANN and GA Toolboxes of MATLAB software are utilized for the purpose. The multilayered perceptron (MLP) neural networks with feed-forward back-propagation training algorithms were designed to predict the scour depth. The mean squared error and correlation coefficient are used to check the performance of networks. It is found that the ANN architecture 4-16-1 having trained with Levenberg-Marquardt 'trainlm' function had best performance having mean squared error of 0.001 and correlation coefficient of 0.998. In addition, the suitability of 'trainlm' method over other training methods is also discussed. The scour depths predicted by ANN model were compared with those computed by the two analytical models (with and without sidewall correction for contracted zone) and an empirical model proposed by Dey and Raikar [1]. In addition, heuristic search technique called genetic algorithm is used to develop the predictor for maximum scour depth within channel contraction. The population size for GA was 500 members with total generations of 1000, crossover fraction of 0.8 and Gaussian operator for mutation. It is promising to observe that the GA model predicts the maximum scour depth equally well as that of empirical model of Dey and Raikar [1]. Hence, both ANN and GA models can be satisfactorily used to predict the scour depth within channel contractions.
Processes, 2021
This study presents, experimentally, similarity and Froude number similitude (FNS) in the dimensi... more This study presents, experimentally, similarity and Froude number similitude (FNS) in the dimensionless features of two solitary waves propagating over a horizontal bed, using two wave gauges and a high-speed particle image velocimetry (HSPIV). The two waves have distinct wave heights H0 (2.9 and 5.8 cm) and still water depths h0 (8.0 and 16.0 cm) but identical H0/h0 (0.363). Together with the geometric features of free surface elevation and wavelength, the kinematic characteristics of horizontal and vertical velocities, as well as wave celerity, are elucidated. Illustration of the hydrodynamic features of local and convective accelerations are also made in this study. Both similarity and FNS hold true for the dimensionless free surface elevation (FSE), wavelength and celerity, horizontal and vertical velocities, and local and convective accelerations in the horizontal and vertical directions. The similarities and FNSs indicate that gravity dominates and governs the wave kinematics ...
The characteristics of water flow field around an air pocket stuck to the inner top-wall of a hor... more The characteristics of water flow field around an air pocket stuck to the inner top-wall of a horizontal pipe, with approaching flows having fully developed turbulent boundary layer situation, are ...
Processes, 2021
This study presents, experimentally, similarity and Froude number similitude (FNS) in the dimensi... more This study presents, experimentally, similarity and Froude number similitude (FNS) in the dimensionless features of two solitary waves propagating over a horizontal bed, using two wave gauges and a high-speed particle image velocimetry (HSPIV). The two waves have distinct wave heights H0 (2.9 and 5.8 cm) and still water depths h0 (8.0 and 16.0 cm) but identical H0/h0 (0.363). Together with the geometric features of free surface elevation and wavelength, the kinematic characteristics of horizontal and vertical velocities, as well as wave celerity, are elucidated. Illustration of the hydrodynamic features of local and convective accelerations are also made in this study. Both similarity and FNS hold true for the dimensionless free surface elevation (FSE), wavelength and celerity, horizontal and vertical velocities, and local and convective accelerations in the horizontal and vertical directions. The similarities and FNSs indicate that gravity dominates and governs the wave kinematics ...
The characteristics of water flow field around an air pocket stuck to the inner top-wall of a hor... more The characteristics of water flow field around an air pocket stuck to the inner top-wall of a horizontal pipe, with approaching flows having fully developed turbulent boundary layer situation, are ...
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Papers by Rajkumar Raikar