Sheeja Janardhanan
@scmsgroup.org
Professor
SCMS Group Of Institutions
Scopus Publications
Scopus Publications
Premchand Mallampalli, Sheeja Janardhanan, Kesavadev Varikattu Karottu, and Gnaneswar Ommi
Innovative Research Publishing
Numerous 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 region and appendages and the interaction effects are intricate. Therefore, this study attempts to 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 scaled at 1:36 was the subject of a numerical study in which 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 zigzag maneuvers were 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 when encountering regular waves in shallow water conditions compared to waves in deep waters and a lack of waves in shallow waters.
Anjana Viswanath, Vidya Chandran, and Sheeja Janardhanan
Springer Nature Singapore
Vidya Chandran, Poornima Rajendran, Shabu Gopakumar, K. S. Arun Kumar, C. A. Nikhilraj, and Sheeja Janardhanan
Springer Nature Singapore
Anoop Sasidharan, Ratna Kishore Velamati, Sheeja Janardhanan, Venkata Ramana Murthy Oruganti, and Akram Mohammad
Springer Nature Singapore
Sheeja Janardhanan, Vidya Chandran, and Rajesh Rajan
Informa UK Limited
The 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.
Anoop Sasidharan, Ratna Kishore Velamati, Sheeja Janardhanan, Venkata Ramana Murthy Oruganti, and Akram Mohammad
MDPI AG
An 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.
Vidya Chandran, Sheeja Janardhanan, and M. Sekar
Springer Nature Singapore
Gautam C. Sekhar, D. Gokul Krishna, H. Abhimanue, Fadil K. Meeran, and Sheeja Janardhanan
Springer Science and Business Media LLC
G R Raghav, Sheeja Janardhanan, E Sajith, Vidya Chandran, and V Sruthi
IOP Publishing
Sheeja Janardhanan and Parameswaran Krishnankutty
Springer Singapore
Ensuring navigational safety of a vessel entails the determination of the manoeuvring coefficients or the hydrodynamic derivatives and the subsequent simulation of its trajectory well in advance of constructing the ship and this task is indeed a very challenging one. The number of hydrodynamic derivatives to be determined is based on the mathematical model used for the representation of hydrodynamic forces and moments. This chapter presents the mathematical formulation of the problem and the numerical approach used for obtaining the hydrodynamic derivatives. For this, an attempt has been made to numerically simulate the conventional horizontal planar motion mechanism (HPMM) towing tank experiment using the RANSE CFD model. A container ship model has been modelled for performing simulation andanalysis. The numerical tank size has been set following the ITTC guidelines, applying the grid size of 600,000 hexahedral cells. The free-surface effects have been taken into account. The prescribed body motions have been modelled by using the mesh morphing ANSYS CFX technique with 3-modes motion viz. pure sway, pure yaw and combined sway and yaw motions, referred as combined motions in this chapter. The time histories of forces and moments have been approximated with the Fourier series in order to enable the comparison with the corresponding equations for forces and moments, as represented by the developed mathematical model defined with linear and non-linear hydrodynamic derivatives. These computed derivatives have been compared with the experimental results, showing reasonably good agreement.
Vortex induced vibration of cylindrical structures is an extensively researched topic. Most of the studies have concentrated on the response of the cylinder in the cross flow (CF) direction. In a realistic ocean environment, structures such as drilling and marine risers are more or less free to vibrate both in CF and in line (IL) directions. It has also been observed that the IL vibrations have significant influence on the CF response. Interaction between the responses in inline and cross flow directions has still been not fully understood. This paper addresses the same through a simplified numerical method for understanding the interaction between these two responses using two dimensional computational fluid dynamics (CFD) simulations. Here analyzes two cases have been considered; where in the cylinder is modeled with two different values of ratio of natural frequency of the cylinder in the IL direction to that in the CF direction. The trends of variation of hydrodynamic and structural parameters have been analyzed to comprehend the effect of directional natural frequency ratio on the cylinder response and hydrodynamic force coefficients. The shedding pattern has also been studied in this paper. An increase by 18% in the value of the lift coefficient and 38 % of that in the drag coefficient has been observed when the frequency ratio is increased from 1 to 2. The results show that the cylinder with frequency ratio 2 is more prone to lock in vibration. This phenomenon may be related to the shifting of shedding pattern from 2S to P + S mode when the frequency ratio is 2.
Vidya Chandran, Sekar M., Sheeja Janardhanan, and Varun Menon
MDPI AG
Harnessing the power of vortices shed in the wake of bluff bodies is indeed a boon to society in the face of fuel crisis. This fact serves as an impetus to develop a device called a hydro vortex power generator (HVPG), comprised of an elastically mounted cylinder that is free to oscillate in the cross-flow (CF) direction even in a low velocity flow field. The oscillatory motions in turn can be converted to useful power. This paper addresses the influence of system characteristics viz. stiffness ratio (k*) and mass ratio (m*) on the maximum response amplitude of the elastically mounted cylinder. Computational fluid dynamics (CFD) simulations have been used here to solve a two way fluid–structure interaction (FSI) problem for predicting the trend of variation of the non-dimensional amplitude Y/D with reduced velocity Ur through a series of simulations. Maximum amplitude motions have been attributed to the lowest value of m* with Ur = 8. However, the maximum lift forces correspond to Ur = 4, providing strong design inputs as well as indicating the best operating conditions. The numerical results have been compared with those of field tests in an irrigation canal and have shown reasonable agreement.
Sijo M.T., Jayadevan K.R., and Sheeja Janardhanan
Emerald
Purpose Stir casting is a promising technique used for the manufacture of Al-SiC metal matrix composites. The clustering of reinforcement particles is a serious concern in this production method. In this work, mushy-state solidification characteristics in stir casting are numerically simulated using computational fluid dynamics techniques to study the clustering of reinforcement particles. Design/methodology/approach Effects of process parameters on the distribution of particles are examined by varying stirrer speed, volume fraction of reinforcement, number of blades on stirrer and diameter ratio (ratio of crucible diameter to stirrer diameter). Further, investigation of characteristics of cooling curves during solidification process is carried out. Volume of fluid method in conjunction with a solidification model is used to simulate the multi-phase fluid flow during the mushy-state solidification. Solidification patterns thus obtained clearly indicate a strong influence of process parameters on the distribution of reinforcement particles and solidification time. Findings From the simulation study, it is observed that increase in stirrer speed from 50 to 150 rad/s promotes faster solidification rate. But, beyond 100 rad/s, stirrer speed limit, clustering of reinforcement particles is observed. The clustering of reinforcement particles is seen when volume fraction of reinforcement is increased beyond 10 per cent. When number of blades on stirrer are increased from three to five, an increase in solidification rate is observed, and an uneven distribution of reinforcement particles are observed for five-blade geometry. It is also seen from the simulation study that a four-blade stirrer gives a better distribution of reinforcement in the molten metal. Decrease in diameter ratio from 2.5 to 1.5 promotes faster solidification rate. Originality/value There is 90 per cent closeness in results for simulation study and the published experimental results.