Proceedings of Fluid Mechanics and Fluid Power (FMFP) 2023, Vol. 2
Fluid Dynamics
- 2025
- Book
- Editors
- Hardik Kothadia
- K. R. Arun
- G. Rajesh
- Jaywant H. Arakeri
- Book Series
- Lecture Notes in Mechanical Engineering
- Publisher
- Springer Nature Singapore
About this book
This book presents select proceedings of the 10th International and 50th National Conference on Fluid Mechanics and Fluid Power. It covers recent research developments in the area of fluid mechanics, measurement techniques in fluid flows, and computational fluid dynamics. The key research topics discussed in this book are fundamental studies in flow instability and transition, fluid-structure interaction, multiphase flows, solidification, melting, cavitation, porous media flows, bubble and droplet dynamics, bio-mems, micro-scale experimental techniques, flow control devices, underwater vehicles, bluff body, bio-fluid mechanics, aerodynamics, turbomachinery, propulsion and power, heat transfer and thermal engineering, fluids engineering, advances in aerospace and defence technology, micro- and nano-systems engineering, acoustics, structures and fluids, advanced theory and simulations, novel experimental techniques in thermo-fluids engineering and many more. The book is a valuable reference for researchers and professionals interested in thermo-fluids engineering.
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Table of Contents
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Frontmatter
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Effects of Roughness on the Pressure Side of a Symmetric NACA 0015 Airfoil
M. Vikram, Bheema Kalyana Raama, Ranga Srinivas Gokul, E. Karthik Vel, S. Nadaraja PillaiAirfoils are critical components in various applications, with wind turbines being a key focus due to their role in sustainable energy generation. The efficiency of wind turbines is influenced by multiple factors, with blade design being paramount. While techniques like camber and active aerodynamic control have been used to enhance performance, they often introduce complexities and increased costs. Surface tailoring, particularly the use of surface roughness, offers a passive control method that has been explored since the 1950s. This chapter delves into the effects of surface roughness on the pressure side of a symmetric NACA 0015 airfoil, providing a thorough analysis of how varying roughness averages impact aerodynamic performance. The study involves an experimental setup using a subsonic wind tunnel and a symmetric airfoil with different roughness elements applied to the pressure side. The results reveal significant improvements in lift and aerodynamic efficiency, particularly with a 320-grit roughness, which demonstrates the lowest drag and highest lift-to-drag ratio. The chapter discusses the underlying aerodynamic principles, highlighting how surface roughness induces turbulence, delays flow separation, and maintains a favorable pressure gradient. This research expands the potential applications of surface roughness in optimizing airfoil performance, offering insights that could be crucial for advancements in wind energy and other aerodynamically driven fields.AI Generated
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AbstractAn empirical investigation was carried out on a base NACA 0015 symmetric airfoil, alongside a modified version featuring emery sheets of varying grit sizes, spanning the entire chord length from the leading edge to the trailing edge on the airfoil’s pressure side. Comprehensive time-series pressure data was meticulously collected through a sophisticated Ethernet-based simultaneous pressure scanner equipped with 64 channels and placed on the airfoil surface, comprising 21 pressure ports. This analytical study is primarily aimed at enhancing the airfoil’s aerodynamic efficiency through the strategic utilization of surface roughness applied to the pressure side. Notably, the emery sheets used exhibited different grit sizes, specifically 80, 120, 220, 320, and 400 grits. The exhaustive analysis of the acquired pressure data underscores the efficacy of employing surface roughness as an economical and viable passive flow control device for augmenting the overall efficiency of the airfoil. -
Effect of 2D Roughness on Heat Transfer in Rayleigh–Bénard Convection
Vinay Kumar Tripathi, Pranav JoshiThis chapter investigates the intricate effects of 2D roughness on heat transfer in Rayleigh–Bénard convection, a phenomenon where fluid is heated from below and cooled from above, leading to complex convective patterns. The study focuses on the impact of sinusoidal rough walls on heat transfer, revealing significant differences compared to smooth walls. Through meticulous simulations using Ansys Fluent, the research demonstrates that at low Rayleigh numbers, the presence of sinusoidal roughness can suppress heat transfer by approximately 25% compared to smooth walls. This suppression is attributed to the increased thermal boundary layer thickness, which offers greater resistance to convective heat transfer. The chapter provides detailed temperature and velocity profiles, highlighting the formation of a single convection roll and the behavior of thermal and hydrodynamic boundary layers. The findings are validated against experimental and numerical results from prior studies, ensuring the robustness of the conclusions. This comprehensive analysis offers valuable insights into the dynamics of Rayleigh–Bénard convection over rough surfaces, making it an essential read for those interested in advanced heat transfer mechanisms and fluid dynamics.AI Generated
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AbstractThe present study shows the effect of 2D boundary roughness on heat transfer in Rayleigh–Bénard convection (RBC). The non-dimensional heat transfer characterized by the Nusselt number \(Nu\) is computed for Rayleigh number \(Ra = 1.96 \times 10^{5}\). The heat transfer (\(Nu\)) is observed to be decreased (\(\approx 25\%\)) due to sinusoidal horizontal rough walls in comparison with that for smooth horizontal walls. The suppression of the heat transfer is attributed to the larger thermal resistance offered by the thicker thermal boundary layer near the top and bottom sinusoidal rough walls as compared to that by the thermal boundary layer for smooth walls. -
Creeping Flow of Shear-Thinning Fluids Through an Orifice
Niharika Dutt, Swati A. PatelThe chapter explores the fundamental aspects of fluid flow through pipe orifices, emphasizing the behavior of shear-thinning fluids under low Reynolds number conditions. It begins by highlighting the significance of orifice flow meters in practical engineering applications, particularly in industries dealing with viscous oils. The study focuses on the discharge coefficient, which is influenced by the Reynolds number, diameter ratio, and orifice thickness. The investigation delves into the impact of different pressure tapping locations, such as corner taps and D−D/2 taps, on the discharge coefficient's performance. The numerical methodology employs the finite element-based software COMSOL Multiphysics to solve the governing differential equations for power-law fluids. The results reveal the intricate flow kinematics, including the formation and disappearance of eddies, and the variation of viscosity contours with the power-law index. The chapter concludes with a proposed correlation for the discharge coefficient, considering the power-law index and orifice thickness, and discusses the implications for the design and operation of orifice flow meters in real-world applications.AI Generated
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AbstractIn this study, the two-dimensional creeping flow of shear-thinning fluids through a square-edged concentric orifice in a pipe has been analysed numerically over a wide range of orifice plate thickness, 1/16 ≤ γ ≤ 1 with fixed diameter ratio of the orifice to pipe, β = 0.5. The numerical result has been derived over the range of power-law index, 0.2 ≤ n ≤ 1 to analyse the discharge coefficient as an important parameter while using an orifice meter as a flow measuring device for shear-thinning fluids. The influence of the orifice plate thickness (γ) and power-law index (n) on the discharge coefficient has been studied in detail. Further flow field has been examined in terms of velocity contours, viscosity contours, and streamline patterns over the range of thickness of the orifice and power-law index. A comparison has been made between two different types of pressure tapings, i.e., D−D/2 taps and corner taps for the entire thickness-to-diameter ratio taken into consideration. In addition, a correlation has been established for the discharge coefficient as relation to orifice thickness and power-law index thereby enabling their interpolation for the intermediate values in various applications. -
Analysis of Aerodynamic Characteristics of Wing with Fence
V. Prasanna Vasan, S. Lakshmi Balaji, K. Dhatchna Moorthy, E. Karthik Vel, T. A. Sundaravadivel, S. Nadaraja PillaiThe chapter investigates the aerodynamic benefits of wing fences on tapered and swept-back wings, focusing on their role in reducing pressure drag and enhancing static stability. It highlights the challenges posed by spanwise flow, which increases the risk of tip stalling and strengthens wing tip vortices, particularly during take-off and landing. The study employs subsonic wind tunnel experiments to analyze the effects of single and double fences of varying lengths on wings with different taper ratios. Key findings include significant improvements in the lift coefficient (C_L) and a reduction in total drag, with single fences generally outperforming double fences in terms of C_L max. The chapter also discusses the manufacturing ease of wing fences and their potential to improve aircraft performance and safety during critical phases of flight. The experimental results provide valuable data on the pressure distribution and flow characteristics, offering a deeper understanding of how wing fences can be optimized for better aerodynamic efficiency.AI Generated
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AbstractThe major demand associated with the aviation industry is to reduce the total drag and to increase the CLmax of the wing. The tapered wing was found to have lesser pressure drag but it also has a pitfall of formation of span wise flow which is a major drawback. Obstructing the span wise flow plays a challenging part in the tapered wing which can be done with addition of boundary layer potential fences. The attachment of wing fences disrupts the span wise flow which results in improved aerodynamic efficiency of the aircraft. In this experimental investigation we interpret the installation of single and double fence with different dimensions on 2 different taper ratio wing. From results, we infer that the attachment of single fence was effective in increment of CLmax and installation of double fence were effective in the total drag reduction. Employment of single fence in tapered wing shows an 9% (approx) increment than the base models investigated in this paper. Thus, the wing fence is a very potential passive device that can provide major aerodynamic performance and can improve the efficiency of civil aircrafts. -
A Comparative Assessment of Algebraic Volume of Fluid Formulations for Capturing Sharp Interfaces
Kommineni Vijay, Rahul Kumar, Prabhansu, Jyotirmay BanerjeeThe chapter presents a detailed comparative assessment of algebraic Volume of Fluid (VOF) formulations, focusing on their ability to capture sharp interfaces in computational fluid dynamics. It begins by discussing the challenges and limitations of existing algebraic and geometric VOF methods, particularly in three-dimensional implementations. The chapter then delves into various numerical schemes, including CICSAM, m-CICSAM, SAISH, and MSTACS, each designed to address specific issues such as numerical diffusion and interface smearing. The performance of these schemes is evaluated through benchmark test cases, including the hollow circle and square oblique translation, Zalesak’s slotted disk problem, and three-dimensional shearing tests. The results demonstrate the superior performance of MSTACS in maintaining interface sharpness across a wide range of Courant numbers, making it a promising candidate for future research and applications. The chapter concludes by advocating for a simple algebraic formulation within a unified framework, aiming to reduce the complexity associated with switching between different schemes.AI Generated
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AbstractIn the present work, a comparative assessment is presented to establish the accuracy of some algebraic Volume of Fluid (VOF) schemes toward capturing a sharp interface. The comparative assessment is reported here between CICSAM, m-CICSAM, SAISH, and MSTACS through benchmark test cases in two- and three-dimensional domain. It is established through the present analysis that MSTACS exhibits a minimal degree of numerical diffusion compared to other schemes, resulting in precise depiction of sharp interfaces across a broad spectrum of Courant numbers. -
Thermohydraulic Performance of Nanofluid Flow in Various Cross-Section Ducts: A CFD Study
Varma Anwesha, Kottayat NidhulThis chapter delves into the intricate world of nanofluid flow within various cross-sectional ducts, focusing on the thermohydraulic performance under turbulent conditions. The study employs computational fluid dynamics (CFD) to investigate the heat transfer and pressure drop characteristics of Al2O3-water nanofluids in circular, square, triangular, serpentine, and elliptical ducts. The research highlights the significant enhancement in the Nusselt number and friction factor observed in serpentine geometries, attributed to the increased turbulent kinetic energy and mixing induced by the wavy profile. Conversely, elliptical geometries demonstrate superior thermohydraulic performance parameters, balancing heat transfer enhancement with manageable pressure drops. The chapter also explores the impact of Reynolds number on the overall performance, revealing that while higher Reynolds numbers boost heat transfer, they also elevate pumping power requirements. The detailed analysis of velocity and turbulent kinetic energy contours provides a deep understanding of the flow dynamics within each geometry, offering crucial insights for optimizing heat exchanger designs and enhancing thermal management systems.AI Generated
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AbstractThis paper presents the numerical study of forced convective heat transfer with the help of nanofluids for various duct cross sections, namely circular, square, triangular, serpentine and elliptical are taken into consideration. The CFD analysis is carried out in a turbulent regime with Reynolds number (Re) in the range of 3000−9000 and a volume fraction of 1%. Nanofluids have shown considerable augmentation in the base fluid’s heat transfer and thermal conductivity. A single-phase model predicts the Nusselt number (Nu), Nu enhancement factor, friction factor and thermohydraulic performance factor. The highest Nusselt number and friction factor enhancement were noticed for similar hydraulic diameter and heat input for serpentine geometry. Due to the higher friction factor in the serpentine duct, the highest value of THPP was reported for elliptical geometry. -
Performance Evaluation of Solar Air Heater Duct with Inverted Y-Shaped Ribs: A Numerical Exercise
Monalisha Swain, Arnab MukherjeeThe chapter explores the optimization of solar air heaters (SAH) through the implementation of inverted Y-shaped ribs, focusing on the enhancement of thermal performance. The study employs numerical simulations to analyze the effects of relative roughness pitch (p/e) and Reynolds number (Re) on the thermo-hydraulic performance of ribbed SAHs. Key findings include the identification of optimal p/e values and Re ranges that maximize the Nusselt number, indicating improved heat transfer. The investigation also delves into the velocity distribution and turbulence generation within the SAH duct, highlighting how the introduction of ribs enhances mixing and heat transfer. Additionally, the chapter examines the friction factor and its variation with Re and p/e, providing a balanced view of the trade-offs between heat transfer enhancement and pressure drop. The results offer valuable insights for the design and optimization of SAHs, contributing to the advancement of solar energy utilization.AI Generated
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AbstractThe research explores the characteristics of heat transfer and fluid flow in a solar air heater (SAH) duct, where transverse inverted-Y-shaped ribs are used. The study's key findings regarding friction factor, Nusselt number, and visualizations of flow parameters within the SAH are presented. To predict the heat transfer rate in rectangular SAH, the analysis incorporates various dimensionless parameters, such as relative roughness pitch (P/e), and Reynolds number (Re). This study examines a range of relative roughness pitch values (9.4 to 25.86) and Reynolds numbers (5243 to 18,000) with variation in relative roughness height. A two-dimensional computational domain features an aluminum absorber plate with a uniform heat flow of 1000 W/m2. The study significantly improves heat transfer by incorporating an inverted Y-shaped ribbed absorber plate in SAH. This indicates a substantial enhancement in the overall efficiency of heat transfer within the solar air heater. -
Numerical Study on Flow Through Gas Turbine Combustor Diffuser
Sayan Patra, K. P. ShanmugadasThe chapter investigates the performance characteristics of gas turbine combustor diffusers, focusing on the critical factors that influence their efficiency. It begins by highlighting the importance of diffusers in reducing flow velocity and achieving the desired pressure rise in gas turbine combustors. The study emphasizes the challenge of designing an optimum diffuser that minimizes flow separation, which can lead to higher pressure drops and lower operational efficiency. A comprehensive literature review is presented, discussing the key parameters that affect diffuser performance, such as the pressure recovery coefficient, area ratio, and turbulence intensity. The chapter also explores the complexities of modeling diffusers using computational fluid dynamics (CFD) codes, particularly the difficulties in resolving near-wall flow structures and the trade-offs between different turbulence models. The research employs the SST k-ω model in ANSYS FLUENT to investigate the performance of a 2D diffuser, validating the results against benchmark data. The study examines the effects of inlet turbulence intensity and area ratio on pressure recovery, providing valuable insights into optimizing diffuser design. Additionally, the chapter discusses the limitations of RANS models in predicting flow behavior in three-dimensional regions and suggests future work using Large Eddy Simulation (LES) to enhance the accuracy of diffuser performance predictions.AI Generated
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AbstractThe present work numerically investigates the performance aspects of a canonical diffuser geometry and the effect of turbulence as a possible parameter to control separation. A numerical model is developed in Ansys FLUENT and validated with the results of an experimental data set. The internal flow field is simulated for different inlet turbulence intensities and expansion ratios. The results show that turbulence intensity is proportional to the pressure recovery up to a maximum limit beyond which there is no more variation. Pressure recovery reaches a maximum up to an AR of 2.1 beyond which it starts falling rapidly. Numerical investigations using the RANS model on a 3D geometry show less pressure rise than experimental results. -
Ground Effects on Flows Past Symmetric Airfoils of Different Thicknesses
Dilip Lalchand Parmar, Deepak Kumar Singh, Arjun SharmaThis chapter investigates the profound impact of ground effects on the aerodynamic performance of symmetric airfoils with varying thicknesses. By examining the lift and drag characteristics under different flow conditions, the study sheds light on the complex interplay between airfoil geometry and ground proximity. The research reveals that as the gap between the airfoil and the ground decreases, the lift coefficients exhibit significant variations, influenced by the airfoil's thickness and the Reynolds number. The study employs advanced computational fluid dynamics techniques, utilizing the Reynolds-Averaged-Navier–Stokes equations and the Spalart–Allmaras turbulence model, to simulate flows over NACA0012 and NACA0018 airfoils. The results highlight the critical role of surface pressure distributions in determining lift characteristics, with thicker airfoils experiencing more pronounced ground effects. The chapter also explores the dependence of ground effects on Reynolds number, providing insights into how varying flow conditions affect aerodynamic performance. This detailed analysis offers a comprehensive understanding of the aerodynamic phenomena at play, making it an essential read for those interested in the intricacies of airfoil-ground interactions.AI Generated
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AbstractGround effects on flows past NACA0012 and NACA0018 airfoils, are studied at chord-based Reynolds numbers of \(5 \times 10^{4}\) and \(3 \times 10^{5}\), using Reynolds-Averaged-Navier–Stokes simulations. Gap ratios in the range 0.15–1.0, are considered. The simulations are conducted for two values of angle of attack, \(0^\circ\) and \(10^\circ\). At a higher value of Reynolds number, lift coefficients decrease more rapidly for the thicker airfoil with decreasing gap ratio, at \(0^\circ\) angle of attack, due to increase in suction pressure on the lower airfoil surface. At \(10^\circ\) angle of attack, positive lift coefficients are obtained that increase more rapidly for the thinner airfoil with decreasing gap ratio, due to increase in positive pressure coefficients on the lower airfoil surface. At a lower value of Reynolds number, the flow is significantly affected due to separation of boundary layers on the lower and upper airfoil surfaces at \(0^\circ\) and \(10^\circ\) angles of attack, respectively. -
Optimization and Benchmarking of Twin VAWT Configurations Using Taguchi and Data Envelopment Analysis
V. Vishnu Namboodiri, Rahul GoyalThe chapter delves into the optimization and benchmarking of twin vertical axis wind turbine (VAWT) configurations to enhance their power extraction capabilities. It addresses the limitations of horizontal axis wind turbines (HAWTs) in decentralized energy applications and highlights the potential of VAWTs due to their omnidirectional wind acceptance and lower operational control requirements. The study employs the Taguchi orthogonal array for optimization and Data Envelopment Analysis (DEA) for benchmarking, focusing on key parameters such as turbine spacing, angle between turbines, and solidity ratio. Through numerical simulations and detailed analysis, the chapter identifies optimal configurations and benchmark models, providing valuable insights into improving the efficiency and scalability of VAWTs for wind farm applications. The findings underscore the significance of the solidity ratio in influencing VAWT performance and demonstrate the effectiveness of the proposed methods in optimizing and benchmarking twin VAWT configurations.AI Generated
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AbstractIncreasing energy demands yield the development of new interventions in sustainable and renewable energy sources. Wind energy has gained significant attention due to its market acceptance and scalability. Optimization and scalability of vertical axis wind turbines (VAWTs) are essential for wind farm applications. The present study discusses a strategy to optimize and benchmark the twin VAWT configurations and utilizes the Taguchi design of experiments as an optimization tool. At the same time, data envelopment analysis is considered as the benchmarking tool. The Taguchi L4 array is used to perform the required numerical simulations, and a further signal–noise (S/N) ratio is calculated to obtain the optimum result. The responses to the numerical simulations are further utilized to establish benchmarking turbine configurations. The twin VAWT configurations having turbine spacing (TS) = 1.3D, the angle between the turbine (TA) = 90°, and the solidity ratio = 0.373 are found to be optimal. The O2 and O3 models were selected as the benchmark models through input-oriented Charnes, Cooper, and Rhodes (ICCR) and input-oriented Banker, Charnes, and Cooper (IBCC) data envelopment analysis (DEA) models. -
Aerodynamic Characteristics of S809 and S1046 Airfoils with Constant and Variable Split
G. Bhanu Chandana, G. S. Nivedha, N. Nivethitha, S. Nadaraja PillaiThis chapter delves into the intricate world of wind turbine blade optimization by examining the aerodynamic characteristics of two prominent airfoils, S809 and S1046, with a focus on chordwise splits and varying gap lengths. The research is driven by the imperative to enhance power production and efficiency, thereby reducing reliance on fossil fuels and mitigating climate change. By employing computational fluid dynamics (CFD) and experimental validation, the study provides a thorough analysis of how different split configurations affect the aerodynamic performance of these airfoils. The investigation reveals that splitting the airfoils can decrease drag and dynamic stall, potentially leading to improved energy production and overall efficiency. The chapter also explores the impact of turbulence intensities, comparing real-world conditions at 12% to base models at 5%, to provide a more accurate reflection of operational environments. Through detailed velocity contours and performance graphs, the study offers a nuanced understanding of how constant and tapered splits influence the lift and drag coefficients of the airfoils. The findings highlight the superior stall characteristics of the S809 airfoil, which could lead to reduced noise and more predictable airflow separation. Additionally, the research underscores the importance of split location and relative angle between split walls and freestream in designing effective split configurations. The comprehensive analysis and comparative study of S809 and S1046 airfoils make this chapter an essential read for those seeking to advance wind energy research and optimize wind turbine performance.AI Generated
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AbstractWind energy is a significant contributor to global renewable energy production. Therefore, it is essential to optimize this energy resource by mitigating unfavorable aerodynamic conditions as much as possible. One such method is the use of passive flow control devices that offer various advantages since they do not require complex actuation mechanisms, which makes them cost-effective and easy to implement. This project aims to study the behavior of an airfoil by splitting it into two parts along the length of the chord. The gap between the two split parts of the airfoil will be varied mechanically to study the boundary layer separation. The flow over the surface of the split airfoil will be energized by the formation of the jets at the rear end, leading to a delay in boundary layer separation, thus decreasing the dynamic stall of the airfoil. -
Numerical Investigation of Low Reynold's Number Mini-Channel Water Cooling for Li–Ion Battery Thermal Management
Indra Kumar Lokhande, Nishant TiwariThe chapter delves into the critical role of thermal management in ensuring the reliable performance and longevity of lithium-ion batteries, particularly in applications such as electric vehicles and renewable energy storage. It explores various cooling systems, with a focus on liquid-based mini-channel cooling, which offers enhanced heat transfer capabilities due to its small hydraulic diameters and large surface area-to-volume ratios. The study conducts a detailed numerical simulation to evaluate the thermal performance of a mini-channel water-cooled battery management system at low Reynolds numbers, optimizing fluid flow characteristics, pumping power, and contact thermal resistance. The investigation reveals that a Reynolds number of 50 provides an efficient and economical balance, significantly improving thermal performance while maintaining safe operating temperatures. The chapter also discusses the impact of different discharge rates and Reynolds numbers on battery temperature, pumping power, and contact thermal resistance, providing valuable insights for designing efficient and cost-effective cooling systems.AI Generated
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AbstractA three-dimensional numerical analysis was conducted to examine the impact of Reynold’s number on a liquid-cooled battery thermal management system. The findings indicate that the battery’s temperature rises with increasing charging/discharging current rates. To address this issue, a numerical model was developed, utilizing a mini-channel to extract heat from the battery through water circulation. The model evaluated the temperature variation at Reynold’s numbers of 10, 50, and 100, assessing their impact on pumping power and contact thermal resistance. To ensure accuracy, the three-dimensional numerical model of conjugate heat transfer with the battery model was validated against previous works, enabling the determination of temperature variation, contact thermal resistance, and pumping power. The results indicated that a Reynold’s number of 50 proved to be the most efficient for high current discharges up to 6C. Additionally, the proposed cooling system demonstrated that cooling half of the surface on a single side of the cell efficiently maintained the battery’s maximum temperature within 325 K. Overall, the study showcased the potential of the mini-channel-based battery cooling system as a lightweight, robust, and cost-effective solution. -
Primary Instability Analysis of Modified Square Cylinder
Darshna Songara, Pritanshu Ranjan, Mayuresh MagdumThe chapter explores the significance of flow past bluff bodies, highlighting their impact on various structures and systems, from bridge pillars to marine structures. It emphasizes the importance of understanding the critical Reynolds number (Re critical), at which periodic flow behavior and vortex shedding begin, and how this threshold is influenced by geometric modifications. The study investigates the flow characteristics around concave and convex square cylinders, revealing distinct differences in drag coefficients, Strouhal numbers, and flow topologies. Through detailed computational analyses and comparisons, the chapter provides a comprehensive understanding of how geometric alterations affect wake behavior, force distributions, and potential applications, such as energy harvesting and noise reduction. The findings underscore the necessity of considering geometric modifications in the design and optimization of structures subjected to cross-flow conditions.AI Generated
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AbstractThis study attempts to compare the behavior of concave and convex square cylinders in laminar incompressible flow to investigate the effect of geometry on primary instability. Cases are simulated in finite volume-based software OpenFOAM and developed and unsteady flow characteristics are compared at Reynolds number (Re hereafter) 55. Stuart–Landau equation was used to calculate the critical Re, which is the onset of primary instability. It was found that the critical Re for the concave cylinder, Re = 53.76, is higher than that for the convex cylinder, Re = 43.12, and the value of the coefficient of drag came out to be 1.41 and 1.612 for the concave and convex cylinder, respectively. This difference was attributed to the stronger shear layer for convex cylinder than concave, which was responsible for its higher coefficient of drag. Additionally, velocity and vorticity plots were analyzed for both cylinders to understand the flow field better. -
Aerodynamics of a Simplified High-Speed Train—Effect of Moving Ground and Wheel Rotation
Mohammad Asif Sultan, Subhransu RoyThe chapter explores the aerodynamic performance of high-speed trains, emphasizing the influence of moving ground and wheel rotation on drag and lift forces. It begins by highlighting the importance of aerodynamic studies for reducing power consumption and enhancing passenger comfort at high speeds. The research employs a 1/8th scale model of a high-speed train, considering various details such as bogies, wheel fairings, and inter-carriage gaps to realistically represent flow dynamics. The study compares three boundary conditions: stationary ground, moving ground, and moving ground with rotating wheels, revealing significant variations in aerodynamic drag and lift coefficients. The moving ground condition increases the total drag by 10.2%, while the addition of wheel rotation further elevates it by 1.2%. The chapter also delves into the flow separation and vortex structures in the wake of the train, providing a detailed analysis of the static pressure distribution and velocity contours. The findings underscore the critical role of underbody effects and the necessity of considering realistic boundary conditions in aerodynamic simulations. The conclusions draw from extensive numerical simulations validated against wind tunnel experiments, offering a comprehensive understanding of the aerodynamic behavior of high-speed trains under different operational scenarios.AI Generated
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AbstractDuring aerodynamic simulation of a moving train set under no-wind condition, the train set is held stationary in the computational domain; the air moves over the train, the ground moves below the train and the wheels rotate about a stationary axis. However, during wind tunnel experiments for train aerodynamics it is not always possible to provide a moving floor (ground) and a rotating wheel. Therefore we need to assess the quality of drag data if moving floor and/or rotating wheel is not used. Here computational fluid dynamics (CFD) simulations involving the two-equation realizable \(k-\epsilon \) turbulence model have been carried out to evaluate the effect of moving ground and rotation of wheels on the aerodynamic characteristics of a high-speed train set. Simulation results show that the total drag with stationary ground is the least, but when the ground is moving, a 10.2% increase in drag is observed which further increases by 1.2% when the rotation of wheels is also considered. Moving ground increases the aerodynamic drag coefficient and pressure distributions of each bogie. The rotation of the wheels increases the flow velocity near the wheels and the overall drag contribution of the bogies. -
Laminar Combined Convection in Pseudoplastic Fluids from a Horizontal Cylinder in an Adiabatic Channel
Khyati Aherwar, Niharika Dutt, Preeti Suri, Swati A. PatelThis chapter investigates the complex interplay of laminar combined convection in pseudoplastic fluids flowing over a horizontal cylinder within an adiabatic channel. The study focuses on the influence of confinement and cross-buoyancy effects, which are critical in various industrial applications such as food processing, energy storage, and polymer processing. The research examines how the degree of confinement and the relative directions of forced flow and thermal buoyancy alter velocity and thermal fields, leading to assisting, opposing, or cross-buoyancy phenomena. The chapter provides a thorough literature review, highlighting the scarcity of studies on cross-buoyancy-driven flow in confined channels, especially for non-Newtonian fluids. It presents a detailed problem formulation, numerical methodology, and validation of results, ensuring the reliability of the findings. The results discuss the flow kinematics, thermal fields, drag and lift coefficients, and average Nusselt numbers, offering a comprehensive understanding of heat transfer enhancement in pseudoplastic fluids. The chapter concludes with a proposed correlation for predicting average Nusselt numbers, providing a valuable tool for engineers and researchers in optimizing heat transfer processes in confined channels.AI Generated
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AbstractThe laminar combined free and forced convection is studied in pseudoplastic or shear-thinning fluids flowing past a confined horizontal cylinder. The forced flow is directed normal to the direction of thermal buoyancy in a confined channel with adiabatic walls. The study expands the results over the range of pseudoplastic fluids varying in the power-law index, n from 0.3 to 1, including Newtonian fluid as a limiting case. The effect of non-dimensional parameters on the cross-buoyancy flow, Prandtl number, 1 ≤ Pr ≤ 100, Reynolds number, 1 ≤ Re ≤ 20, Richardson number, 0 ≤ Ri ≤ 3, and Grashof number, 10 ≤ Gr ≤ 105 have been explored for two values of cylinder confinement B, defined as the diameter of cylinder to height of the channel, D/H = 1/10, 1/5. The governing equations have been solved for the steady-state flow over the range of parameters by employing finite-element numerical scheme. The flow and thermal field distorted by cross-buoyancy past a hot cylinder is analysed by plotting the streamlines and isotherms in the channel. The total drag, lift coefficients, and average Nusselt number increase as the confinement ratio, B increases from 1/10 to 1/5. At Ri = 3 for B = 1/5, the flow reversal adjacent to the wall in the downstream section of the cylinder has been observed at Re = 20 for Pr = 1 which is abolished as the shear-thinning effect of fluid decreases. Finally, a correlation to predict the average Nusselt number as Nuavg = f(Re, Pr, Ri, n) for both the confinements has been proposed over the range of parameters. -
Numerical Investigation of Forced Convection Inside a MCHS Using Microfin—Dimple as a Flow Disruptive Structure
Karan Dhuper, Lalit Kumar, Siddhartha DuttaguptaThe rapid advancement in semiconductor technology has led to the development of compact electronic devices with high heat dissipation rates, posing significant challenges to thermal management. This chapter investigates the use of microchannel heat sinks (MCHS) with microfin and dimple structures to enhance heat transfer and optimize thermal performance. Through extensive numerical simulations, the study compares the hydrothermal characteristics of conical and cylindrical fins, both with and without dimples, under varying Reynolds numbers. The findings reveal that conical fins, particularly those with dimples, exhibit superior heat transfer capabilities due to the induced vertical fluid motion and enhanced mixing. The chapter also explores the impact of dimples on pressure drop and overall thermal performance, providing a detailed analysis of temperature contours and flow structures. The results highlight the potential of microfin-dimple configurations in addressing the cooling demands of modern electronic devices, offering a deeper understanding of the complex interplay between fluid dynamics and heat transfer in microchannel systems.AI Generated
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AbstractThe present work investigates the hydrothermal performances of MCHS incorporating dimple structures. Conical and cylindrical fins with dimples are used as a flow disruptive structure. To solve the governing equations, finite volume methodology (FVM) is considered. The results are presented using the parameter space of Po number, Nu number, and TP. A comparative study of different flow disruptive structures (conical fin, conical fin with dimple, cylindrical fin, and cylindrical fin with dimple) is done to find the superior MCHS design based on their TP values. It is observed that microfin improves the heat dissipation at the expense of pressure loss. The obtained results reveal that the conical fin configuration shows higher thermal characteristics when compared with the other configurations. The reduction in heat dissipation and pressure loss is observed while introducing the dimple inside the microchannel. Further, flow topology along with the streamlines is discussed to give the reasoning behind the different TP values of different design configurations. -
Maximizing Savonius Turbine Performance Using Kriging Surrogate Model and Grey Wolf-Driven Cylindrical Deflector Optimization
Paras Singh, Vishal Jaiswal, Subhrajit Roy, Raj Kumar SinghThe chapter addresses the critical need for sustainable energy solutions, focusing on the optimization of Savonius turbines, a type of vertical axis wind turbine. The study highlights the challenges faced by Savonius turbines, particularly their low wind energy conversion efficiency, and explores innovative methods to enhance their performance. The research employs a kriging surrogate model and grey wolf optimization to fine-tune the design parameters of a cylindrical deflector placed upstream of the turbine's blades. This approach aims to maximize the turbine's coefficient of power (C_p) and coefficient of moment (C_m), key metrics for evaluating turbine efficiency. The chapter delves into the computational modeling and simulation processes, including the use of unsteady RANS simulations and the Menter's k-ω SST turbulence model, to accurately predict flow patterns and optimize turbine performance. The results demonstrate significant improvements in turbine efficiency, with the optimized deflector configuration showing a remarkable 34.24% increase in C_p at a tip speed ratio (TSR) of 0.9. The chapter also provides detailed flow structure analyses, including pressure, velocity, and vorticity contours, to illustrate the physical mechanisms behind the performance enhancements. This comprehensive optimization framework offers valuable insights into the design and improvement of Savonius turbines, paving the way for more efficient and sustainable wind energy solutions.AI Generated
This summary of the content was generated with the help of AI.
AbstractWith the growing power demand and the imperative for renewable energy sources, wind power stands as a vital component of the energy transition. To optimize energy production, researchers have focused on design optimization of Savonius-type vertical axis wind turbines (VAWTs). The current study utilizes unsteady Reynolds-averaged Navier–Stokes (URANS) simulations using the sliding mesh technique to obtain flow field data and power coefficients. A Kriging Surrogate model is trained on the numerical data of randomly initialized data points to construct a response surface model. The grey wolf optimization (GWO) algorithm is then utilized to achieve the global maxima on this surface, using the turbine’s power coefficient as the objective function. A comparative analysis is carried out between simulation and experimental data from prior studies to validate the accuracy of the numerical model. The optimized turbine–deflector configuration shows an improvement of 34.24% in power coefficient. Additionally, the GWO algorithm’s effectiveness is compared to Particle Swarm Optimization (PSO) and is found to be better in most cases, converging toward the global maxima faster. This study explores a relatively unexplored realm of metaheuristic optimization of wind turbines using deflectors, for efficient energy harvesting, presenting promising prospects for enhancing renewable sources.
- Title
- Proceedings of Fluid Mechanics and Fluid Power (FMFP) 2023, Vol. 2
- Editors
-
Hardik Kothadia
K. R. Arun
G. Rajesh
Jaywant H. Arakeri
- Copyright Year
- 2025
- Publisher
- Springer Nature Singapore
- Electronic ISBN
- 978-981-9767-83-0
- Print ISBN
- 978-981-9767-82-3
- DOI
- https://doi.org/10.1007/978-981-97-6783-0
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