Faculty Publications
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Item Lattice Boltzmann computation of two dimensional differentailly heated cavity of incompressible fluid with different aspect ratios(Institute of Electrical and Electronics Engineers Inc., 2017) Karki, P.; Yadav, A.K.; Arumuga Perumal, D.A.Lattice Boltzmann Method (LBM) is a novel computational technique to solve fluid flow problem in bounded domain. Continuum based methods are being widely used to solve the natural convection problem, whereas in the last two decades, mesoscopic approach has gained popularity to solve heat transfer and fluid flow problems. In natural convection cavity, density difference caused by heating and cooling of fluid at different locations gives rise to buoyancy force which in turn drives the fluid flow. The right side and left side wall of the cavity is made hot and cold respectively whereas top and bottom walls are made adiabatic. In the present work, natural convection problem of differently heated cavity with constant Prandtl number (Pr = 0.71) and varying Rayleigh number (Ra =103-106) is solved employing LBM to study the effect of various aspect ratios (H/L) on both Nusselt number and streamlines. Results are plotted in the form of streamlines and isotherms for different Rayleigh numbers at different aspect ratios. Nusselt numbers are obtained at the hot wall and cold wall to study the rate of heat transfer. Obtained results are compared with the existing results. It is found that with increase of Rayleigh number, there is increase in the Nusselt number. The increment in aspect ratio leads to the significant decrement in the Nusselt number and vice versa. © 2017 IEEE.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 Three-Dimensional FEM Analysis of Nanoparticle-Assisted Radiofrequency Ablation of Tissue-Mimicking Phantom(Springer Science and Business Media Deutschland GmbH, 2021) Naik, S.S.; Bonthala, B.P.; Yadav, A.K.Radiofrequency ablation (RFA) is a minimally invasive procedure to damage the cancer cells. In RFA, heat is generated only at the center zone of the tumor, and this heat has to propagate up to the periphery of the tumor. Since the thermal conductivity of phantom is low, it reduces heat transfer rate, and time required for complete ablation of tumor will be more. Since the ablation time is one of the main concerns, it is required to reduce it below the standard time (≈7.3 min). The ablation time can be reduced by injecting the nanoparticles into the tumor. In this paper, numerical studies are conducted on PAG phantom to analyze the effect of nanoparticle assisted RFA on the ablation time. Results indicate that in case of nanoparticles assisted RFA, heat conduction rate increases and takes lesser time (17.56% less) to ablate the tumor completely than that in conventional RFA. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Numerical Study of Mixed Convection in Single and Double Lid Driven Cavity Using LBM(Springer Science and Business Media Deutschland GmbH, 2021) Sen, S.; Arumuga Perumal, D.; Yadav, A.K.The lattice Boltzmann method (LBM) has been gaining popularity over the last two decades and the method has been extended from simple fluid flow problems to problems involving heat transfer. In the present work, an attempt is made to model cases involving mixed convection. Two types of problems are considered in this study; the first one dealing with mixed convection in a single-sided lid-driven cavity and the second one dealing with mixed convection in a double-sided lid-driven cavity in parallel and anti-parallel configurations at constant Prandtl number and various values of Richardson number. For the first problem, a square domain is considered with a moving lid at a lower temperature while the stationary wall at the bottom at a higher temperature. The cavity side walls are treated with an adiabatic boundary condition. In LBM, a forcing term dependent on temperature difference is utilized to vary the value of y-velocity in order to satisfy the effects of gravity on mixed convection. A grid independence study is conducted to show that the results are independent of the grid chosen, and good agreement with literature is achieved. The second problem is an extension of the first one; the cavity bottom wall is first given a velocity in the opposite direction, and then in the same direction, and the velocity streamlines, temperature contours and local Nusselt number variation in the top wall for these cases are plotted. The developed method helps in the visualization of various phenomena such as splitting of flow into two halves for the parallel configuration and formation of secondary vortices with high Reynolds number. © 2021, Springer Nature Singapore Pte Ltd.Item Optimum injection timings for bioethanol-diesel blends and its effect on tail pipe emission in common rail diesel engine(American Institute of Physics Inc., 2021) Lamani, V.T.; Baliga M, A.U.; Yadav, A.K.; Kumar, G.N.; Naik, R.; Arya, B.computational study of a CRDI engine is carried out to examine the performance and tailpipe emissions the with bioethanol blended diesel fuel for various injection timing. The simulation ponders various bioethanol diesel blends (0-30 %), and for several injection timings from 21°- 33° BTDC in the interval of 3°CA, at ∼90MPa injection pressure. The k-ς-f model is used to simulate turbulence inside the cylinder. Combustion study is analyses is carried by using three zone extended coherent flame model. Equivalence ratio for all the cases of blends is kept constant and equal to the case of neat diesel (E0). Optimum injection timing (IT) is obtained for maximum indicated thermal efficiency (ITE) for bioethanol diesel blends operation. The maximum indicated thermal efficiency for E0, E10, E20 and E30 is found at 27°, 27°, 30° and 33° IT respectively. Significant increase in ITE of ∼5% is observed in the case of E30 compared to diesel (E0). Effect of IT on tail pipe emissions such as NO, soot and CO formation is also obtained. The results indicate that ignition delay increases and mean soot formation decreases with advancing the IT's. For all advanced IT higher in-cylinder peak pressure and temperature are observed. Obtained results are validated with available literature data and found a good agreement. © 2021 Author(s).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 Comparative Numerical Appraisal of Subcritical and Supercritical CO2-Based Natural Circulation Loop(Springer Science and Business Media Deutschland GmbH, 2022) Wahidi, T.; Yadav, A.K.A natural circulation loop (NCL) is a passive heat transfer system in which circulation occurs solely due to density differences caused by thermal imbalance and the elevational difference between the source and sink of the loop. Carbon dioxide (CO2)-based NCL is highly sensitive to operating conditions and vulnerable to unstable behaviour, mainly due to intense changes in the thermo-physical properties of CO2. Therefore, NCLs always require precise design assessment that focusses on the interaction of all the transient responses of buoyancy and friction forces, ensuring a stable zone of operation. In this article, a three-dimensional computational fluid dynamics study has been carried out for over a range of pressures (30 to 100 bar) and heat inputs (500 to 1500 W) to do the comparative investigation of fluid flow and heat transfer phenomenon of subcritical/supercritical CO2-based NCLs with water-based NCL. The simulations quantify the degree of instability and heat transfer rate for subcritical/supercritical CO2 and water. A possible mechanism for continuous flow oscillation and measurement of instability with different pressure in unstable loops is also proposed in this study. Obtained results are validated with the correlations available in the literature; it shows an amicable agreement. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Exergy Analysis of a Triangular Duct Solar Air Heater with Square Ribs(Springer Science and Business Media Deutschland GmbH, 2022) Nidhul, K.; Kumar, S.; Yadav, A.K.; Anish, S.The awareness about limited energy resources has urged the scientific community to scrutinize the energy conversion devices and optimize existing limited resources. In this analytical study, the exergetic performance analysis of a triangular cross-section square ribbed solar air heater (SAH) is compared with a conventional SAH. Reynolds number (Re) and temperature rise parameter (∆T/G) are varied, and their effect on exergetic efficiency is quantified. For the present study, maximum exergetic efficiency for the present study is obtained for non-dimensionalized rib height (e/D) of 0.05 and non-dimensionalized rib pitch (P/e) of 10. The optimum combinations of roughness parameters are interpreted through plots to design turbulators for triangular cross-section solar air heaters. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Study of Electronic and Optical Properties of Bulk and Monolayer Vanadium Di-Sulfide for Energy Storage Devices(Institute of Electrical and Electronics Engineers Inc., 2023) Yadav, A.K.; Jasil, T.K.; Pandey, S.K.In this study, the WIEN2k code implementation of the density functional theory (DFT) approach was used to examine the structural, electronic, and optical characteristics of bulk and monolayer VS2 material. For both bulk and monolayer VS2 material, we calculated the various properties including density of states, band-structure, and dielectric functions using the generalised gradient approximation (GGA). This method gives better results for the structural parameters and shows that monolayer VS2 is more favorable for energy storage devices. Additionally, we report the growth of the bulk and monolayer VS2 crystals using a chemical vapor deposition system. It was also found the crystal growth of monolayer VS2 started at the growth temperature of 690 °C. Bulk VS2 crystal growth also performed in this study. Raman spectroscopy shows a peak intensity started at 385 cm-1 for monolayer VS2 growth crystal at 690 °C. These observations show monolayer VS2 material is more suitable for energy storage devices. © 2023 IEEE.Item Facile hydrothermal synthesis of vanadium disulfide nanomaterial for supercapacitor application(SPIE, 2023) Mandal, A.; Pandey, N.; Pandey, S.K.; Yadav, A.K.; Chakrabarti, S.Vanadium disulfide (VS2) is a prominent metallic member of transition metal dichalcogenides (TMDs) family and has already demonstrated its flair in energy storage device applications such as supercapacitors and batteries. In this work, we have synthesized hexagonal shape VS2 nanomaterial using a facile one step hydrothermal route and investigated the phase, morphology and structural properties of the material. The formation of phase has been confirmed from the X-ray diffraction (XRD) plot by correlating with the database of Joint Committee on Powder Diffraction Standards (JCPDS) 00-036-1139 of 1T VS2. Further, the crystalline behavior of VS2 nanomaterial can be seen from the high resolution transmission electron microscopy (HRTEM) measurement. Moreover, the morphology of the synthesized material is obtained from the field emission gun-scanning electron microscopy (FEG-SEM). Also, the characteristic Raman peaks of 1T VS2 at 140.3 cm-1 and 192.3 cm-1 have been observed from the Raman spectrum indicating the metallic behavior of synthesized material. The peak at 281.8 cm-1 is attributed to the in-plane vibrational mode (E2g1) while the peak at 404.5 cm-1 represents the out-of-plane vibrational mode (A1g) of V-S bond. The Fourier transform infrared (FTIR) spectrum shows the V-S-V and V=S vibrational modes around 534 cm-1 and 982 cm-1 respectively. The study introduces a low cost, large scale, highly crystalline, and metallic VS2 nanomaterial with potential application for next generation supercapacitors and other energy storage devices. © 2023 SPIE.