Research Publications
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Item Numerical study on the influence of directional natural frequency on flow induced vibrations /(Trans Tech Publications Ltd., 2025-01-23) Janardhanan, SheejaItem Numerical study on maneuvering a container ship in shallow water waves /(IJIRSS, 2023-09-15) Mallampalli, Premchand; Janardhanan, Sheeja; Karottu, KesavadevVarikattu; Ommi, GnaneswarNumerous practical and mathematical techniques have been piloted to study ships’ behavior in deep water conditions with and without waves, and shallow water conditions without waves, while only limited investigations have been carried out to assess ships’ behavior in shallow waters with wave conditions as the flow around the stern regionandappendages and the interaction effects are intricate. Therefore, this study attemptsto understand the infrequently explored subset of a vessel’s behavior in regular waves in shallow water conditions(channel depth to ship draft ratio taken as 1.5). A container ship (S175) model scaledat 1:36 was the subject of a numerical study inwhich it was subjected to static and dynamic maneuver simulations in head sea conditions. The waves were induced using the dispersion relationship of waves in a given depth. The trends of forces and moments acting on the hull while undergoing maneuvering motions were obtained using a smooth particle hydrodynamics-based computational fluid dynamics solver. The resulting periodic trends of forces and moments were analyzed using the Fourier series method to extract the Fourier coefficients and,in turn,calculate the hydrodynamic derivatives. The trajectories in turning circle and zigzagmaneuverswere also simulated using a MATLAB code. The results demonstrate an increase in trajectory parameters and improvement in counter maneuverability owing to the complex flow physics around the hull whenencountering regular waves in shallow water conditionscompared to waves in deep watersand a lack of waves in shallow waters.Item Optimization of a hydro kinetic power generator using genetic algorithm /(Springer Nature, 2023-01-01) Janardhanan, SheejaThe paper discusses the optimization of a renewable energy harvester which converts kinetic energy of slow moving currents into electricity. The metaheuristic method of genetic algorithm is adopted to optimize the process parameters of the Hydro Vortex Power Generator (HVPG). The study is conducted in a three folded manner. The device was optimized for the range of Reynolds number 0.3 × 105 < Re < 2.5 × 105 based on equations derived analytically from vibration theory and then using an empirical equation derived from experimental data for two regimes of flow (250 < Re < 3.8 × 104 and 0.3 × 105 < Re < 2.5 × 105. Empirical optimization model is observed to predict the maximum amplitude of oscillation with in a realistic range with the theoretical model showing a three time over prediction. A comparison with experimental results suggests that the effect of added mass on the amplitude of oscillation is of enhanced damping and hence a more realistic prediction is obtained from empirical model optimization. The most significant result from this analysis is that the empirical model predicts maximum amplitude at lowest value of mass ratio (m*), whereas the theoretical model predicts it at the highest value.Item Aerodynamic analysis of deployable wing arrangement for space shuttle /(Springer Nature, 2022-11-28) Janardhanan, SheejaThe study space for morphing wings is astonishingly wide and provides ample scope for enhancements up against fixed wings. Morphing-wing research has accumulated considerable recognition in the aerospace community over the last decade, and a folding wing is a promising approach that can improve aircraft proficiency over multiple varieties of missions which conclusively enhance the capability of the space shuttle. In this paper, the conventional shape of the wings is being refashioned to serve the requirements for maintaining the flight and also for navigation. The idea was sparked by the traditional Japanese fan and has a hinged mechanism similar to that of the fan. This work introduces a novel concept for retractable dynamic wings on a space shuttle. Modeling of the spacecraft with modified wings is done in SOLIDWORKS. The aerodynamic analysis is performed using the computational fluid dynamics (CFD) method with ANSYS FLUENT® (2020 R1) as the solver. The aerodynamic force coefficients are estimated for five different specific deployment phases, viz., zeroth (0°), one quarter (7.5°), half (15°), three-quarter (22.5°), and full (30°) phases. The result reveals that the coefficient of drag drops and the coefficient of lift rises from the primary phase to the final phase providing promising inputs into the idea of retractable wings.Item Estimation of stability derivatives due to translational motion of various lta vehicles using cfd /(Springer Nature, 2022-11-28) Janardhanan, SheejaIn this paper, the aerodynamic model parameters (stability derivatives) of the aerostat are investigated based on a CFD-based approach. The stability derivatives due to the translational motion of the aerostat are considered for the analysis in this paper. The extraction of the stability derivatives involves the simulation of the oscillations of the aerostat along the vertical direction (heave motion) and axial direction (surge motion). A forced sinusoidal oscillation is used for the simulation of the aerostat, and one stable period of oscillation is taken for the derivatives extraction. Four different aerostats are considered for the current study with four different angles of attack. Zhiyuan aerostat, HAA aerostat, NPL aerostat and GNVR aerostat are the aerostats considered for this study. The stability derivative results obtained for the four aerostats are analysed and compared with respect to their geometrical features. The dynamic stability derivatives of the Zhiyuan aerostat suggest its superiority among the four aerostats considered.Item On the design of a compact emergency mechanical ventilator with negative expiratory exit pressure for COVID-19 patients /(Taylor & Francis, 2022-07-27) Janardhanan, SheejaThe present work deals with the design of a cylinder-piston arrangement to deliver the required tidal volume (TV) of air to the patient through the respiratory tract especially in the setting of severe acute respiratory syndrome corona virus 2 (SARS CoV-2) or corona virus disease (COVID-19). The design ensures that only the desired volume of air is delivered in each breath and a negative pressure is retained at the delivery point in a separate cylinder. The frequency of piston motion is the same as that of the average human respiratory rate (RR). The effect of negative pressure on time of evacuation under the present condition has been verified. The present design provides a compact ventilator unit with a surface area of 0.8 × 0.4 m2 with a minimal power requirement of 116.48 W. An RR of 16 is obtained with a volume flow rate in lit/s by using a twin cylinder arrangement with bore diameter 0.1 m and length 0.4 m. The ratio of inspiration time to expiration time is designed to be 1:2 by controlling the stroke frequency as 16 and piston speed 0.32 m/s. The present design provides promising quantitative information on the design of an automated continuous mechanical ventilator (CMV), which is different from bag mask valve (BMV) operated ventilators, and on preventing and minimising barotrauma.Item Stability derivatives of various lighter-than-air vehicles : a cfd-based comparative study /(MDPI, 2022-07-07) Janardhanan, SheejaAn aerostat with a single tether is proposed for the application of wind measurements at low altitudes. In the current study, the aerodynamic model parameters (stability derivatives) of the aerostat are investigated based on a CFD-based approach. The static, as well as the dynamic stability derivatives of the aerostats are presented. The calculation of the dynamic stability derivatives involves the simulation of the oscillations of the aerostats in their axial direction (surge), the vertical direction (heave) and angular motions with respect to the lateral direction (pitch). A forced sinusoidal oscillation is used for the simulation of the aerostat, and one stable period of oscillation is taken for the derivatives’ extraction. Four different aerostats are considered for the current study with four different angles of attack. The Zhiyuan aerostat, HAA aerostat, NPL aerostat and GNVR aerostat are the aerostats considered for this study. The stability derivative results obtained for the four aerostats are analyzed and compared with respect to their geometrical features. From the static aerodynamic characteristics, the Zhiyuan aerostat shows better performance than the other aerostats in terms of the lift–drag ratio. The dynamic stability derivatives of the Zhiyuan aerostat suggest its application as the proposed low-altitude wind measurement system.Item Numerical study on domain independency for prediction of vortex shedding parameters of a circular cylinder /(Springer Nature, 2022-01-01) Janardhanan, SheejaThe catastrophes of history make vortex-induced vibration an extensively studied area. The response predictions of offshore and sub-sea structures have gained importance off-late ever since these have been widely used by the petroleum industry. Most of the studies have confined to the comprehension of wake characteristics and the estimation of hydrodynamic loading and shedding parameters of stationary cylinders. Computational fluid dynamics has evolved as one of the effective tools in prediction of response characteristics under vortex shedding and many researchers have studied various aspects of computations that are crucial with reasonable degree of accuracy. This paper addresses the effect of the geometrical shape of fluid domain that encompasses a marine riser during simulations. Four different shapes are analyzed using Reynolds Averaged Navier–Stokes Equation-based commercial solver, ANSYS®. All four domains have the same number of elements, mesh density, and flow Reynolds number (Re). Hydrodynamic force coefficients and frequency of shedding in each case were estimated and compared with previously published numerical and experimental results. It is observed that circular domain is the most efficient in predicting both loading and shedding characteristics with less than 10% deviation as against the theoretical results. Elliptical and square domains failed to capture the vortex shedding phenomenon. The study reveals a significant characteristic of numerical simulations on the modeling and meshing of both near-wall and wake regions.Item Shape improvisation of the solar panels on the roof of an electric vehicle /(Springer Nature, 2021-06-15) Janardhanan, SheejaIt is a well-known fact that bluff body appendages induce augmented drag on a vehicle. Hence, aerodynamic design is inevitable for vehicles for better power and performance. The present work is focused on transforming the present shape of the SCMS School of Engineering and Technology’s solar electric vehicle’s solar roofing from a bluff model to aerodynamic. Computational fluid dynamics studies are carried out on the present shape. The top of the vehicle, housing of the solar panel, is chamfered in steps and a new shape is evolved at ensuring an aerodynamic design. Three different shapes are studied in the present work. The one with minimum drag is suggested for the vehicle. The reduction in the area of the solar panels due to the shape improvisation is compensated for by increasing the surface area to retain the same power input. The proposed new shape is found to reduce the overall drag of the vehicle.Item Numerical Study on the Influence of Directional Natural Frequency on Flow Induced Vibrations(Trans Tech Publications Ltd., 2025-01-23) Janardhanan, SheejaA Two dimensional numerical analysis is done for varying directional natural frequency ratio for a cylinder which is mounted elastically and executes two-degrees of freedom vortex induced vibration (VIV). VIV of the cylindrical structure at subcritical Reynolds number (Re) of 3.8 x 104 is studied using a RANSE based CFD transient fluid structure interaction dynamic simulation model employing a user defined function for modeling the response. Analyses are carried out for three different values of directional natural frequency ratios in the range 0.5, 1 and 1.5. Cylindrical models corresponding to mass ratio 1.32 is investigated. Structural damping is neglected in the present study. The study leads to interesting observations with respect to the patterns of trajectories at certain values of frequency. The paper serves as additional guidelines in riser design and its trajectory predictions.