Faculty Publications
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Item Analysis of forced convection heat transfer through graded PPI metal foams(Pleiades journals, 2019) Kotresha, B.; Gnanasekaran, N.A forced convection heat transfer through high porosity graded Pores per inch (PPI) metal foam heat exchanger is numerically solved in this paper. The physical domain of the problem consists of a heat exchanger system attached to the bottom of a horizontal channel to absorb heat from the exhaust gas leaving the system. Two different pore densities of the metal foam 20 and 40 along with two different metal foam materials are considered for the enhancement of heat transfer in the present numerical investigation. The metal foam heat exchanger is considered as a homogeneous porous medium and is modeled using Darcy Extended Forchheirmer model. The heat transfer through the metal foam porous media is solved by using local thermal equilibrium (LTE) model. The effect of graded pore density and graded thermal conductivity is investigated and compared with the nongraded PPI metal foam. The heat exchanger system is simulated over a velocity range of 6–30 m/s. The pressure drop decreases for the graded pore density metal foams compared to the higher PPI metal foam and also increases with increase in the fluid inlet velocity. The results of temperature and velocity distribution for the graded and nongraded metal foams are compared and discussed elaborately. © Springer Nature Singapore Pte Ltd. 2019.Item Development of a chassis mounted multi stage axial flow turbine for wind energy harvesting on a cruising transport vehicle - A CFD based approach(American Society of Mechanical Engineers, 2016) Hegde, S.S.; Thamban, A.; Ahmed, A.; Upadhyay, M.; Mahalingam, A.Fossil fuels have been a means of energy source since a long time, and have tended to the needs of the large global population. These conventional sources are bound to deplete in the near future and hence there is a need for producing energy from renewable energy sources like solar, wind, geothermal, tidal etc. Technologies involving renewable energy are a growing subject of concern. Further, the problem is also one of excessive pollution caused by conventional sources of energy and their impact on the environment. In particular, one of the main sources of pollution is harmful gases emitting out of automobiles. Wind energy is one among the renewable energy sources which is implemented in large scale energy production to supplement growing domestic energy needs. Significant amount of research has been done in this field to harness energy to power household and other amenities using wind farms. The aim of this project is to come up with a low cost solution for wind energy harvesting on moving vehicles. The purpose of this study is to consider the use of wind energy along with conventional energy sources to power automobiles. This would help reduce the use of fossil fuels in automobiles and hence reduce the resulting environmental pollution. Also since the turbine adds to the weight of the vehicle the aim also is to minimize the weight of the turbine. Extensive structural analysis is done for this purpose to choose a material which would be both light weight and also be able to withstand the stresses developed. In the current paper the drag force produced in automobiles is harvested by using a convergent divergent nozzle mounted below the chassis of the car. Initially drag analysis is done in order to determine the increase in drag force produced after mounting of the nozzle. It is found from existing literature that the drag increases by 3.4% after the mounting of the nozzle making it possible the mounting of a nozzle beneath the car. Additionally exhaust gases is also allowed to pass through the same duct to increase the mass flow to the turbine and thus generate more energy. This is made to strike the blades of a 2 stage axial flow turbine whose rotation generates energy. The power output from the turbine is the parameter of interest. This energy can also be stored in batteries and be used to run auxiliary equipment of the automobile including the air conditioner. The exhaust gases will be passed through a catalytic converter before striking the blades of the turbine in order to prevent corrosion of the blades. Computational Fluid Dynamics (CFD) is used to validate the concept and also come up with a design that maximizes energy generation by such turbines. Numerical results obtained by simulation are validated by theoretical calculation based on turbines inlet and outlet velocity triangles. The future scope of the project would include the use of multiple nozzles in order to study its performance. © Copyright 2016 by ASME.Item CFD analysis of turboprop engine oil cooler duct for best rate of climb condition(Institute of Physics Publishing michael.roberts@iop.org, 2016) Kalia, S.; Ca, V.; Hegde, S.M.Turboprop engines are widely used in commuter category airplanes. Aircraft Design bureaus routinely conduct the flight tests to confirm the performance of the system. The lubrication system of the engine is designed to provide a constant supply of clean lubrication oil to the engine bearings, the reduction gears, the torque-meter, the propeller and the accessory gearbox. The oil lubricates, cools and also conducts foreign material to the oil filter where it is removed from further circulation. Thus a means of cooling the engine oil must be provided and a suitable oil cooler (OC) and ducting system was selected and designed for this purpose. In this context, it is relevant to study and analyse behaviour of the engine oil cooler system before commencing actual flight tests. In this paper, the performance of the oil cooler duct with twin flush NACA inlet housed inside the nacelle has been studied for aircraft best rate of climb (ROC) condition using RANS based SST K-omega model by commercial software ANSYS Fluent 13.0. From the CFD analysis results, it is found that the mass flow rate captured and pressure drop across the oil cooler for the best ROC condition is meeting the oil cooler manufacturer requirements thus, the engine oil temperature is maintained within prescribed limits. © Published under licence by IOP Publishing Ltd.Item Numerical investigation of wave interaction with pile breakwater(IEOM Society ieom-society@iieom.org, 2018) Rao, P.S.B.; Mathew, S.E.; Suvarna, P.; Hunasanahally Sathyanarayana, A.H.; Umesh, P.Pile breakwater consists of a number of piles spaced closely. It works similar to the offshore breakwater by attenuating the energy of the waves and it is due the turbulence caused because of wave-pile interaction. The efficiency of the pile breakwater of single row and two rows is investigated numerically. An open source Computational Fluid Dynamics (CFD) software REEF3D is used in the present study. Initially the grid convergence study is conducted in a rectangular wave flume with a two-dimensional setup and the results are evaluated by comparing the numerical wave profile with the theoretical profile in accordance with the adopted wave theory. The efficiency of the numerically modelled pile breakwater is investigated in terms of the transmission coefficient. The simulations carried out are in accordance with the physical model studies as reported by Subba Rao et al., (1999). The numerically obtained results are validated with the experimental data. The numerically obtained results for the pile breakwater has shown an average of 91.5% agreement with that of experimental results. © IEOM Society International.Item Modeling and design validation of fluidized bed reactors for co-gasification of coal and biomass to study hydrodynamics and conversion(ETA-Florence Renewable Energies, 2019) Manu, J.; Dev, R.; Madav, V.The gasifier was designed with reaction chamber of 65mm diameter and 500 mm height. The study of gas-solid hydrodynamics is essential in designing of fluidized bed gasifier. Drag force plays a critical role in modeling fluidization behavior for gas-solid flow. This paper aims to study the effect of drag force on the fluidization parameter for the presently designed gasifier using CFD approach. The Eulerian-Eulerian model, coupled with different drag models was employed for this purpose. Time-averaged solid volume fraction, granular temperature, axial velocity of the solid particle in a lateral direction, and a central axis of the reactor were examined for different drag models like Syamlal O’Brien, Gidaspow, Mckeen and Representative unit cell. Effects of laminar and turbulent models on flow behavior were also studied. The study concluded that the McKeen model shows a relatively flat profile while estimating solid volume fraction while the RUC model overestimated the axial velocity of particles. There was relatively no change in flow behavior for the laminar and turbulent model while predicting the axial velocity of the solid particle in the lateral direction. The axial velocity of particles at a different packing factor was studied and showed no such observable difference in predicting hydrodynamics flow behavior. © 2019 ETA-Florence Renewable Energies.Item Effect of CO2 based natural circulation loop for low temperature applications: CFD analysis(Toronto Metropolitan University, 2019) Wahidi, T.; Nagrani, P.P.; Yadav, A.K.Natural circulation loop (NCL) is a simple and economical heat transfer device in which flow occurs due to the buoyancy effect caused by thermally generated density gradient. In the present study, computational fluid dynamics (CFD) analyses are carried out to emphasize on the fluid ow and heat transfer characteristics of carbon dioxide (CO2 ) based NCL at low temperature (-38°C to 12°C). Studies are conducted in a three-dimensional (3-D) CFD model of NCL at different heat inputs i.e., 100W, 250W, 350W and 500W by keeping the loop fluid at pressure of 50 bar. Methanol is used as coolant in the heat exchanger at a fixed mass flow rate. Effect of loop operating pressure 50 bar on system performance is also investigated. Result are presented in the form of heat transfer rate, pressure drop, Reynolds number (Re) and temperature. Obtained results are validated with available correlations in the form of non-dimensional numbers, and found in good agreement. © 2019, Toronto Metropolitan University. All rights reserved.Item Natural Convection Through High Porosity Metal Foams—A Numerical Study(Springer Science and Business Media Deutschland GmbH, 2021) Kotresha, B.; Jadhav, P.H.; Gnanasekaran, N.Numerical analysis of natural convection through highly porous metal foams attached to the aluminium plates is performed in this study. A heater sandwiched between two aluminium plates attached with aluminium metal foams of different pores per inch (PPI) is considered for the present analysis. Initially, experiments are carried out for aluminium plate-heater assembly for different heat inputs. In the numerical investigation, the aluminium plates are attached with metal foams on either side for further analysis. A well-known Darcy extended Forchheimer flow and LTNE thermal models are considered for the metal foam in the computations. The natural convection is modelled using Boussinesq approximation. Initially, the numerical result for the plate without metal foam is validated with the experimental results for different heat inputs. The results show that the Nusselt number decreases with the increase of metal foam pore density (PPI) and increases with the increase in Rayleigh number. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Numerical Instability Assessment of Natural Circulation Loop Subjected to Different Heating Conditions(Springer Science and Business Media Deutschland GmbH, 2022) Thimmaiah, S.; Wahidi, T.; Yadav, A.K.; Arun, M.Natural circulation loop (NCL) is a passive system in which the driving action of the buoyancy force establishes fluid circulation by overcoming the frictional force without the help of any external power source. NCLs are prone to several kinds of instabilities due to the nonlinearity of the natural convection process. In fact, it is an inability of NCLs to sustain themselves against small perturbations to which any physical system is subjected. This instability in fluid flow creates flow oscillation, chaotic non-linear dynamic behaviour and flow reversal. In this article, three-dimensional computational fluid dynamics (CFD) numerical simulations have been carried out for a range of supercritical pressures (80 bar to100 bar) and heat inputs (250 W to 2500 W) to do the comparative investigation of instability phenomenon in supercritical CO2-based regular natural circulation loop configured with two different types of heat sources, i.e. heater and isothermal wall at the source with a cold heat exchanger (CHX) at sink. Results show higher instabilities for heater-exchanger loop (Heater-CHX) than an isothermal heater with heat-exchanger loop (ISO-CHX). With an increase in heat input, loops attain stability at a faster rate for a given operating pressure. At a lower heat input, both the loops show bidirectional fluctuation, whereas it is unidirectional at high heat input. Nusselt number shows that the Heater-CHX loop’s heat transfer capability is more compared to ISO-CHX loops. Obtained results are validated with the existing correlations, and a good agreement is obtained. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Dispersion in an Urban Cross-Street Intersection(Springer Science and Business Media Deutschland GmbH, 2025) Ranadive, S.; Singh, L.; Jitendra Pal, S.A typical urban street intersection comprises of roadways, pedestrian walkways, and tall buildings on the sides. Due to the large number of vehicles plying on the urban streets, the pedestrians are exposed to vehicular pollution. With the increase in the density of automobiles, there is a bigger threat to pedestrians. The current study investigates pollution dispersion in the case of an eight-story building across a cross-street intersection. The study includes the effect of the aspect ratio (AR = 0.5, AR = 1, and AR = 2), a ratio of building height to road width, on flow patterns and dispersion. The second part of the work includes the effect of wind approach angle (0º, 30º, 45º, 60º) on the dispersion. It is found that the pollutant mass concentration at the nose level of pedestrians is strongly influenced by the aspect ratio wherein the taller building provides less exposure to pedestrians due to the lateral dispersion. The wind approach angle also affects the pollutant concentration at the nose level. The exposure to pollutant is skewed along the length of the road walkways in the case of 30º and 60º. However, the dispersion in more uniform in the case when wind approach angle is 45º. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Advances in Computational Fluid Dynamics Modeling for Biomass Pyrolysis: A Review(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Kulkarni, A.; Mishra, G.; Palla, S.; Ramesh, P.; Surya, D.V.; Basak, T.Pyrolysis, a process for extracting valuable chemicals from waste materials, leverages computational fluid dynamics (CFD) to optimize reactor parameters, thereby enhancing product quality and process efficiency. This review aims to understand the application of CFD in pyrolysis. Initially, the need for pyrolysis and its role in biomass valorization are discussed, and this is followed by an elaboration of the fundamentals of CFD studies in terms of their application to the pyrolysis process. The various CFD simulations and models used to understand product formation are also explained. Pyrolysis is conducted using both conventional and microwave-assisted pyrolysis platforms. Hence, the reaction kinetics, governing model equations, and laws are discussed in the conventional pyrolysis section. In the microwave-assisted pyrolysis section, the importance of wavelength, penetration depth, and microwave conversion efficiencies on the CFD are discussed. This review provides valuable insights to academic researchers on the application of CFD in pyrolysis systems. The modeling of pyrolysis by computational fluid dynamics (CFD) is a complex process due to the implementation of multiple reaction kinetics and physics, high computational cost, and reactor design. These challenges in the modeling of the pyrolysis process are discussed in this paper. Significant solutions that have been used to overcome the challenges are also provided with potential areas of research and development in the future of CFD in pyrolysis. © 2023 by the authors.