Institutional Digital Repository (Indian Institute of Technology Kharagpu)

Chaudhuri, Debasis

Integration of Seismic Fractures into a Geocellular Model: From Seismic to Simulation

Rupesh

Delineation of Geotechnical Properties of Subsurface Structures from Quasi-3d ERT Measurements

Vishwakarma, Abhilash

Detection, Localization and Classification of Certain Rail Track Defects from Axle-Box Acceleration Measurements

Singh, Pooja

PhD Thesis Title Interfacial instability in porous medium flow: Influencing factors of viscous fingering Candidate Name: Pooja Singh Roll No.: 18CH91R09Abstract The immiscible and miscible fluid–fluid displacement in porous media is of great importance in several scientific and engineering applications, such as enhanced oil recovery (EOR) and CO2 geo-sequestration. When a low viscosity fluid replaces a high viscosity fluid in porous media, an interfacial instability occurs known as viscous fingering, also known as Saffman-Taylor instability, which reduces the efficiency of the displacement process. Numerous investigations have been conducted to stabilize and control the viscous fingering phenomenon in both immiscible and miscible displacement, the majority of these studies have considered Newtonian fluid. However, due to the complex behavior of non-Newtonian fluids, studies on interfacial instability considering non-Newtonian fluids are still being explored. In this thesis, viscous fingering instability problem is studied considering the non-Newtonian fluid displacement. We present the study of viscous fingering in a radial Hele-Shaw cell in shear-dependent rheological fluid, which transitions from the Newtonian to shear thinning behavior at low shear rates for different constant flow rates of the injection fluid and gap thickness. The viscous fingering characteristics such as side branching, growth of second-generation fingers, and inhibition of tip splitting are observed in the case of shear-thinning flow regime, both experimentally and numerically. The stability of the fingering at ultra-low flow rates exists much beyond that predicted by linear stability analysis.  We propose a quantitative criterion from the linear stability analysis involving non-Newtonian (shear-thinning fluid) to control the pattern formation and suppress viscous fingering controlling a parameter, which is a function of the physical and operating conditions. It is possible to stabilize the interface following a non-linear injection rate, 𝑄 ∼ 𝑡−(2−𝑛)⁄(2+𝑛), which is related to the displaced fluid rheology (n: power-law index). Furthermore, we have experimentally shown a feasible approach toward long-term fingering stabilization with the continuous cyclic time-dependent injection flow rate. We experimentally investigate the interplay and transition of viscous fingering and fracturing for a shear-thickening fluid. We have used cornstarch suspension of different compositions and the rheology of the suspension exhibits shear thickening behavior beyond a critical shear rate. The evolution from viscous fingering to dendritic fracturing morphology is observed. The displacement efficiency of the process can be computed based on the fraction of injected phase to displaced phase as a function of injected volume for different weight fractions of cornstarch suspension. The viscous fingering pattern in 2D media can be significantly different from the 3D pattern as it depends on the geometrical arrangements of the granular structure and flow connectivity in the pore network. However, fingering patterns in the three-dimensional (3D) scenario is different than the 2D case, on account of the gravitational segregation being more effective in 3D porous media. The displacement of the denser fluid by the less dense fluid creates a gravitational tongue, inducing a non-uniform interface that diminishes the displacement efficiency. The interaction between viscous fingering and gravitational segregation is observed in different fields, including hydrocarbons recovery, carbon-dioxide (CO2) sequestration, saltwater aquifer intrusion, and groundwater pollution. We study the three-dimensional viscous fingering morphology to investigate the effect of fluid miscibility and porous medium permeability using the X-ray micro-computed tomography (micro CT) technology. The phase miscibility of the injection fluid to the displaced fluid affects the fingering phenomena, transitioning from dispersion limited to diffusion. The areal sweep efficiency for miscible flow is high in comparison of immiscible flow. We have used the fractal analysis to analyse the complex patterns, and the fractal dimension is related to the process conditions. We report 3D diffusion-limited aggregation simulations to obtain patterns similar to the miscible fingering patterns and provide insights into the pattern growth behavior. The multiphase flow during the steam as well as CO2 injection EOR method can affect the viscous fingering. The coexistence of vapor and liquid in the displacing phase induces anisotropy and heterogeneity in the viscous fingering pattern, markedly distinctive from the classical observations in Hele-Shaw cell experiments and exhibits non-intuitive pattern formations. Therefore, the experimental investigation focuses on immiscible displacement within a radial Hele-Shaw cell using a phase-changing medium. The high viscosity oil is displaced by low viscosity methanol vapor, along with its condensate at different injection pressure. The thermal front movement is impeded due to heat transfer between the fluids as well as the large time scale of thermal diffusion to the other side of the observation window (quartz glass), causing the thermal front to lag behind the fluid front. Initially, momentum diffusion governs heat transfer, followed by thermal diffusion dominance. Interfacial oscillations induced by the Marangoni effect stemming from temperature-induced interfacial tension gradients are observed. Overall, the thesis objective is based on understanding and proposing engineering interventions to the complex problem of interfacial instability in the context of enhanced oil recovery technology.  Keywords: Viscous fingering; Enhanced oil recovery (EOR); Radial Hele-Shaw cell; Saffman-Taylor instability; Non-Newtonian Fluid; Linear stability analysis; fracturing; Fractal dimension; Immiscible and miscible displacement; 3D viscous fingering; X-ray micro-computed tomography; Porous media flow; Diffusion-limited aggregation; Multiphase fluid flow 

Interfacial Instability in Porous Medium Flow: Influencing Factors of Viscous Fingering

Das, Priyadarshini

Performance Assessment of Fly Ash Incorporated Ferrochrome Slag Aggregate Concrete: Particle Packing Optimization Technique

Saha, Sulagna

Understanding Essential Oil Secretory System in Two Commercially Important Cinnamomum spp. with Emphasis on Cinnamomum tamala

Laskar, Mostafizur Rahaman

Quantum Architecture and Algorithms for Structured Hamiltonian Operators with Efficient Gate Complexity and its Application to Signal Processing

Halder, Soumyadeep

Ground State Phases and Dynamics of Single- and Two-Component Dipolar Bose-Einstein Condensates

Gupta, Santosh Kumar

Experimental Investigations of Laser Beam Welded and Post-Weld Heat Treated Nb-1%Zr-0.1%C Alloy and Process Innovation Aided by Artificial Intelligence to Make Welding Economical Abstract  Laser beam welding (LBW) being a high energy density joining technique is preferred for welding both ferrous, non-ferrous and polymers of different thicknesses having applications in the automotive, nuclear, aerospace and chemical industries. Nb-1%Zr-0.1%C (PWC-11) is a solution-strengthened and precipitate-hardened alloy having the potential of structural material to be used in compact high-temperature reactors (CHTR). This alloy is the proposed structural material for the coolant channels to carry heat for hydrogen production. The utility and dependency of autogenous laser beam welded Nb-1%Zr-0.1%C are fundamental research objectives within the CHTR context. Laser beam welding of Nb-1%Zr-0.1%C was carried out in butt configuration to correlate the effect of energy density, viz, laser power, welding speed and laser beam diameter on the mechanical and metallurgical properties of the joint. The performance of the LBW alloy was assessed by carrying out a corrosion test in lead-bismuth eutectic (LBE) maintained at 1100 ℃. The corrosion rate/dissolution behaviour of base metal (BM), fusion zone (FZ) and heat-affected zone (HAZ) were compared based on the weight and dimension change to address the possible reasons for material loss during the operation of carrying out molten LBE at 1100 °C. The increase in micro-hardness of FZ, HAZ and BM could be attributed to the increase in the fraction of low angle grain boundary (LAGB), formation of β-Zr (bcc) phase and oxides of niobium and zirconium. The increase in hardness is an indicator of oxidation, the reason underlying weight loss. β-Zr phase formation increases the susceptibility towards oxidation. The nitride and carbide phases of niobium and zirconium, and compressive residual stress improve the resistance of the alloy towards corrosion and oxidation. The corrosion rates of HAZ, FZ and BM were observed to be equal to 0.25, 0.12, and 0.07 mm/year, respectively. The weight loss %/yr in the BM, FZ and HAZ were seen to equal 0.71%, 1.33% and 2.70%, respectively. The corrosion susceptibility of HAZ was found to be the highest, followed by FZ and BM. Furthermore, the effects of thermal ageing time and temperature used during heat treatment were studied on the tensile strength, elongation, and microhardness of the LBW alloy. The segregation of zirconium, carbon and oxygen increased grain boundary energy and induced brittleness to the grain boundary, resulting in loss of ductility. For the post-weld heat treated (PWHT) samples, the plasticity was found to decrease to about 57% of that of the BM. This was attributed to the precipitation of carbides, grain growth, and dislocation pinning during the ageing process. During the heat treatment of the welded samples, both Yield Strength (YS) and Ultimate Tensile Strength (UTS) were found to decrease to 77% and 86%, of that of the BM, respectively. It had been found that PWHT is a highly resource-intensive material processing technique, resulting in a higher product price for the end customer. Moreover, reactive metals, such as niobium, titanium, and tantalum necessitate particular heat treatment arrangements, further complicating the heat treatment procedure. Post-weld heat treatment of thin sheets of metal (such as niobium in this study) is also difficult due to distortion. To address these challenges, an attempt was made to use artificial intelligence (nature-inspired meta-heuristic optimization technique) to reduce the post-weld treatment procedure. Bonobo Optimization algorithm, which could arrive at the globally optimal solution in fewer iterations than particle swarm optimization (PSO), had the fastest rate of convergence. The mechanical properties of the experiment carried out using optimized parameters, i.e., yield strength (YS), ultimate tensile strength (UTS) and elongation (El) were found to decrease to 85.94%, 98.48% and 58.65%, respectively, of that of the BM and exceeded the PWHT results by 10.13%, 12.51% and 2.75%. Therefore, an AI-based intelligent nature-inspired optimization tool is able to guide the researchers to select the set of input   parameters, so that the enhanced mechanical properties of the weld could be achieved even without carrying out the costly PWHT. Keywords: Laser beam welding; Refractory alloy; Nb-1%Zr-0.1%C; Compact high-temperature reactors; Oxidation; Corrosion; Post-weld heat treatment; Recrystallisation; Artificial intelligence; Bonobo optimizer; Particle swarm optimizer   

Experimental Investigations of Laser Beam Welded and Post-Weld Heat Treated Nb-1%Zr-0.1%C Alloy and Process Innovation Aided by Artificial Intelligence to Make Welding Economical

Sen, Sumit

THEORETICAL STUDY ON NON-EQUILIBRIUM SEDIMENTTRANSPORT IN OPEN CHANNEL FLOWSumit SenAbstractThe thesis primarily focuses on investigating the transport problems of suspendedsediments in turbulent flow through straight rectangular open channels with fixed heightand cross-section. Several theoretical models are developed for the distribution of flowvelocity and sediment concentration for both uniform and non-uniform particles undernon-equilibrium condition, incorporating various turbulent phenomena.A theoretical model is derived for the two-dimensional (2D) distribution of stream-wise velocity in steady, uniform, sediment-laden flow from the Reynolds-averaged Navier-Stokes (RANS) equation by incorporating the effects of sediment concentration and sec-ondary current. The resulting second order partial differential equation (PDE) is solvednumerically and compared with experimental data for both wide and narrow channels.The results indicate that the presence of sediment particles increases the magnitude ofvelocity and as a result, the cross-sectional velocity contours shifts towards the boundarywall with increasing sediment concentration. Additionally, an increase in the aspect ratioof the channel leads to a higher number of circular vortices in the secondary circulation.A model for the steady 2D distribution of sediment concentration along the verticaland stream-wise direction is proposed in turbulent flow over erodible sediment beds.This model incorporates the effect of stratification and considers generalized boundaryconditions. The governing PDE is solved using the spectral collocation method withsecond-kind shifted Chebyshev polynomial. The convergence of the method is gained byfinding the spectral radius of the scheme. Furthermore, a generalized model is presentedto study the steady 2D concentration distribution of coarse sediment, considering theeffects of secondary current, hindered settling, lag velocity, fluid induced lift force andReynolds normal stress gradient. The model also considers the sediment diffusivity asa combination of sediment diffusivity due to the sediment-turbulence interaction anddrift diffusivity. The resulting non-linear PDE is solved numerically and validated withexperimental data under far-field conditions.To gain a better understanding of the sediment transport mechanism, simultaneousstudy of both flow velocity and sediment concentration is important as they are intercon-nected by particle-turbulence interaction. A coupled model of these two is formulatedfor vertical distribution in an unsteady, uniform sediment-laden flow, incorporating theeffects of hindered settling and stratification. The numerical solution is compared withprevious models and experimental data for both unsteady and steady flow conditions. Itis observed that stratification effect results in a decrease in concentration but increase invelocity, while hindered settling leads to an increase in concentration.All these aforementioned models are for uniform sediments; but natural flows con-tain non-uniform particles. Therefore, a model is formulated by modifying the RANSequation to study the unsteady transport of suspended sediments of various grain-sizescoming from erodible sediment beds. This model incorporates the hiding-hindering ef-fect caused by the interaction between non-uniform sediments and utilizes the conceptof mixing length. It is observed that the bimodal distribution of grain sizes evolves fromone strong peak and one weak peak to two strong peaks as the height increases.Keywords : Open channel turbulent flow, Stream-wise velocity, Sediment concen-tration, Uniform and non-uniform sediments, Secondary current, Stratification effect,Hindered settling.xix

Theoretical Study on Non-Equilibrium Sediment Transport in Open Channel Flow

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