Faculty Publications
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Item Conceptual model for the safe withdrawal of freshwater from coastal aquifers(2009) Mahesha, A.The effect of subsurface barrier on the motion of the saltwater-freshwater interface in coastal aquifers is analyzed for wide ranging freshwater pumping scenarios. A Galerkin finite-element model considering sharp interface approach is used for this purpose. A semi-pervious subsurface barrier extending up to impervious bottom of the aquifer is considered at certain distance inland, parallel to the seacoast. The effect of barrier is analyzed in checking the advancement of the saltwater-freshwater interface under different scenarios of freshwater withdrawals at seaward and landward locations of the barrier and compared with nonbarrier conditions. The results indicated that barrier is able to check the advancement of the intrusion significantly and in certain cases, the progress is completely stalled for withdrawals on the landward side. Also, marked variations in the interface profile are observed as compared to no barrier condition, especially, for the seaward freshwater developments. From the model, nearest possible locations from the seacoast have been worked out for the safe withdrawal of freshwater where their effects are negligible on the saltwater advancement. © 2009 ASCE.Item Stability of horizontal oil well - A Jointed Rock model approach(2011) Anantharamu, A.; Singh, T.N.; Venkat Reddy, D.Advancement in technology has paved different ways for the extraction of oil. Drilling of wells, production and injection of fluids results in the alteration of pre-existing stress field in a reservoir. The current study is undertaken to analyze the stability of horizontal oil wells with the change in radius of the well, Poisson's ratio, saturation density, permeability and also to find stress distribution around horizontal oil wells drilled in different reservoir conditions, stress distribution before and after production and also to assess the effect of stress distribution on the stability. The knowledge of stress distribution and its redistribution with change in reservoir conditions can help in selecting well locations and orientations for maximum sweep in reservoirs. Displacement of the particles gives the direction of fracture propagation. As the particle size increases, fracture propagation increases. The stability analysis has been done using Jointed Rock method of Numerical Modeling. Numerical models are mathematical models that use numerical time-stepping procedure to obtain the models behavior over time. The results of the model are shown to agree qualitatively with field observations. The extent of stress distribution is dependent on radius of the well, pore pressure in the reservoir, fracture density of the reservoir and drilling direction. Horizontal wells drilled in highly fractured reservoirs will be less stable. In case of anisotropy, since the stability is very less we must reduce the radius of the well in order to increase the FOS and hence the stability. © 2011 CAFET-INNOVA TECHNICAL SOCIETY.Item Effect of width of gallery of highwall mining on stability of highwall: A numerical modelling approach(Inderscience Enterprises Ltd., 2014) Ram Chandar, K.R.; Kumar, B.G.Owing to continuous increased demand for coal, along with existing mining methods, some novel methods are being looked for. Highwall mining is such a method where considerable quantity of coal blocked in the highwall can be extracted to a great extent. The major challenge in highwall mining is roof control along with the stability of highwall. This method was introduced in one of the opencast coal mines first time in India. A systematic study was taken up using numerical modelling approach to assess the influence of width of gallery of highwall on stability of highwall based on field investigations. The width of gallery was taken as 3.5, 4.25 and 5.0 m. It was found that the stress and strain was more in case of 5.0 m wide gallery compared with 3.5 m wide gallery and the stress and strain values were more at the end point of galleries compared with the starting points of the galleries. The factor of safety values were decreased as the width of gallery increased from 3.5 m to 5.0 m. © 2014 Inderscience Enterprises Ltd.Item Numerical simulation of progressive fracture propagation in petroleum reservoir rock strata using finite element modeling(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Goyal, R.; Singh, K.; Reddyy, D.V.Reservoir perforation allows for interfacing of the pay-zone and the production casing in the petroleum wellbore. Perforations are key interface for fluid movement in completion and they are extremely important for effective design and itis to beensured that well has appropriate number and size of perforation. For directing formation petroleu mfluid from subsurface zone, cased well must be perforated. Perforationis created by implementing controlled detonation of steel casing, cement casing and surrounding rock using specially design edand manufactured shaped charges. Perforating shockwaves and high impact pressureshattertherockto breakdown and propagate crack through it. Numerical model of acuboidal rock sample is createdto decide the preferred fracture plane. Under balance forces have also been taken in account to calculate Von-misesstress. Simulations are performed in order tostudy the behavior of compound stress during chargede to nation of rock and casing fracture. Crack propagation in different directions and principal planes has been found out. Usingthese results, location ofchargesoncasingcanbe defined to propagate fracture indesired locations. This report presents numerical analysis of fracture propagation during charged detonation using finite element methods (FEM).. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.Item The effect of initial momentum flux on the circular hydraulic jump(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2015) Vishwanath, K.P.; Dasgupta, R.; Govindarajan, R.; Sreenivas, K.R.Earlier studies on the circular hydraulic jump have shown that the radial position of the hydraulic jump depends on the flow rate, gravity, and fluid viscosity. In this study, results from numerical simulations and experiments on circular hydraulic jumps are presented and through analysis, it is shown that the momentum flux is an additional controlling parameter in determining the jump location. Apart from the jump location, the variation of the film thickness with flow parameters is also obtained from experiments and numerical simulations. By including the dependence of the momentum flux and dissipation in the film along with other controlling parameters, the data on jump radius obtained from experiments and simulation (including the present study) covering a wide range of parameters reported in the literature can be collapsed on to a single curve. © © 2015 by ASME.Item Classification of Stability of Highwall During Highwall Mining: A Statistical Adaptive Learning Approach(Kluwer Academic Publishers, 2015) Ram Chandar, K.; Hegde, C.; Yellishetty, M.; Gowtham Kumar, B.The depleting coal deposits day by day required the introduction of novel methods of mining like highwall mining. Highwall mining is a method of extraction of coal blocked in the highwall. The method involves considerable challenges in the area of roof control and most importantly the stability of the highwall itself. Highwall mining has gained considerable importance all over the world, owing to the fact that the coal otherwise would not be extracted forever. This paper aims to assess the influence of varying conditions which can affect the stability of the highwall during highwall mining. The effect of gallery length, width of pillar and number of galleries are systematically studied through field investigations where a highwall mining was adopted first time in India. Initially, assessment was carried out using a numerical modelling approach and then the stability of the highwall is classified using multilinear regression, logistic regression and naive Bayes classifier. This will provide a mechanism to predict the stability of the highwall in future cases of similar conditions. The classification is done using statistical adaptive learning methods and a comparison of the methods is done. © 2014, Springer International Publishing Switzerland.Item Nearshore waves and longshore sediment transport along Rameshwaram island off the east coast of India(Society of Naval Architects of Korea jnaoe@jnaoe.org, 2015) Gowthaman, R.; Sanil Kumar, V.; Dwarakish, G.S.; Shanas, P.R.; Jena, B.K.; Singh, J.Wave-induced Longshore Sediment Transport (LST) play an important role in the dynamics of the Dhanushkodi sandspit located southeast of Rameshwaram. The LST along the Dhanushkodi coast is studied based on data collected simultaneously in Gulf of Mannar (GoM) and Palk Bay (PB) using directional waverider buoys. The numerical model REF/DIF1 was used to calculate the nearshore waves and the LST rate was estimated using three different formulae. The model validation was done based on the measured nearshore waves using InterOcean S4DW. Numerical model LITPACK was also used for simulating non-cohesive sediment transport and the LITLINE module was used to study the shoreline evolution over 5 years. Low net annual LST along PB (~ 0.01×106 m3) compared to the GoM region (0.3×106 m3) were due to the weak waves. Accretion in the region led to growth of the Dhanushkodi sandspit by 65 m during the period 2010-2015. © SNAK, 2015.Item Effects of the Reynolds number on two-dimensional dielectrophoretic motions of a pair of particles under a uniform electric field(Korean Society of Mechanical Engineers, 2016) Kang, S.; Mannoor, M.; Maniyeri, R.This paper presents two-dimensional direct numerical simulations to explore the effect of the Reynolds number on the Dielectrophoretic (DEP) motion of a pair of freely suspended particles in an unbounded viscous fluid under an external uniform electric field. Accordingly, the electric potential is obtained by solving the Maxwell’s equation with a great sudden change in the electric conductivity at the particle-fluid interface and then the Maxwell stress tensor is integrated to determine the DEP force exerted on each particle. The fluid flow and particle movement, on the other hand, are predicted by solving the continuity and Navier-Stokes equations together with the kinetic equations. Numerical simulations are carried out using a finite volume approach, composed of a sharp interface method for the electric potential and a direct-forcing immersed-boundary method for the fluid flow. Through the simulations, it is found that both particles with the same sign of the conductivity revolve and eventually align themselves in a line with the electric field. With different signs, to the contrary, they revolve in the reverse way and eventually become lined up at a right angle with the electric field. The DEP motion also depends significantly on the Reynolds number defined based on the external electric field for all the combinations of the conductivity signs. When the Reynolds number is approximately below Recr ? 0.1, the DEP motion becomes independent of the Reynolds number and thus can be exactly predicted by the no-inertia solver that neglects all the inertial and convective effects. With increasing Reynolds number above the critical number, on the other hand, the particles trace larger trajectories and thus take longer time during their revolution to the eventual in-line alignment. © 2016, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.Item Response of Strata and Buildings to Blast Induced Vibrations in the Presence and Absence of a Tunnel(Springer International Publishing, 2016) Rebello, N.E.; Shivashankar, R.; Sastry, V.R.Blast induced vibrations form an inevitable and major part of modern day construction. The changes that happen to the strata or buildings surrounding the blast are evident in a fraction of a second. Effect of damage is more pronounced in the absence/presence of the tunnel. The vibration produced due to blast may be induced due to a deep underground explosion, a surface explosion or even an in-tunnel explosion. In this study the above three situations are numerically modeled by a Distinct Element software 3DEC (3.0). Soil properties are varied representing soft and stiff strata. Further, three velocity time histories of 2, 45 and 85 Hz are used as an input in the model and are applied at three different boundaries of the model. Results of the analysis reveal that the response of building in softer strata and lower frequencies led to greater magnification of velocities and displacements compared to response of buildings in stiff strata. Presence of the tunnel led to reduction of peak velocity (PV’s) and displacements at the building top due to damping effect. PV’s at the top floor were greater than the PV’s at the bottom floor and there was an upliftment of the soil mass at the ground level. However, the upliftment in the presence of the building was lower than the upliftment in the absence of the building. Stress in the tunnel lining increased in the presence of the building, however percentage reduction of stress depends on the number of building stories. © 2016, Springer International Publishing Switzerland.Item Tuned liquid dampers for multi-storey structure: numerical simulation using a partitioned FSI algorithm and experimental validation(Springer India sanjiv.goswami@springer.co.in, 2017) Eswaran, M.; Sathyanath, S.; Niraj, P.; Reddy, G.R.; Ramesh, M.R.Wind-induced and earthquake-induced vibrations of structures such as super-tall towers and bridges can be efficaciously controlled by tuned liquid dampers (TLDs). This work presents a numerical simulation procedure to study the performance of TLDs–structure system through sigma (?)-transformation-based fluid–structure coupled solver. For this, a ‘C’-based computational code has been developed. The structural equations, which are coupled with the fluid equations in order to achieve the transfer of sloshing forces to structure for damping, are solved by the fourth-order Runge–Kutta method, while the fluid equations are solved using finite-difference-based sigma-transformed algorithm. Different iterative and error schemes are used to optimize the code for larger convergence rate and higher accuracy. For validation, a few experiments are conducted with a three-storey structure using TLDs arrangement. The present numerical results of response of TLD-installed structures match well with the experimental results. The minimum displacement of structure is observed when the resonance condition of the coupled system is achieved through proper tuning of TLDs. Since real-time excitations are random in nature, the performance study of TLDs under random excitation has also been carried out in which the Bretschneider spectrum is used to generate the random input wave. © 2017, Indian Academy of Sciences.