Browsing by Author "Saha, Sujoy"

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Computational analysis on fluid flow characteristics in a modified annular dump combustor of a ship /
(Elsevier, 2023-12-30) Saha, Sujoy
The improvement of systems of aeronautical and marine propulsion able to meet the forthcoming drastic certification requirements on the reduction of the level of pollutants emission heavily relies on the development of new concepts of combustion chamber technologies. In view of this, a novel numerical investigation has been performed on the basis of characteristics of the flow of a fluid passing over a simple annular-shaped dump combustor and a modified dump combustor with certain central restrictions like rectangular and spherical shapes. The restrictions are located at a fixed distance of 0.14 m from the inlet. Flow characteristics and patterns are presented sequentially in the form of streamline contours, velocity contour, pressure contour, axial velocity profiles, and centerline velocity profiles. The above-mentioned flow characteristics are studied at several locations in the flow field for various Reynolds numbers (Re), ranging from 103 to 106 for all considered models. The flow regulating mass and momentum conservation partial differential governing equations along the x-axis and y-axis are discretised with the help of the control volume-based finite volume approach. The SIMPLE algorithm and second-order upwind scheme are used to solve iteratively the discretised equations for the case of a fixed aspect ratio of 3 and for a central abstraction of 120 %. The analysis corroborates and concludes that more numbers of bubbles are formed in a geometrically modified dump combustor than in a plain dump combustor. Additionally, it has been found that the number of recirculating bubbles increases along with the value of the Reynolds number. Consequently, the core recirculation zone is improved, which ensures the desirable mixing of fluids in the ship combustor and helps significantly in the reduction of NOx emission and combustion residuals. Furthermore, as the Reynolds number (Re) increases, the variation in axial velocity also raises for all considered Reynolds numbers, indicating an improved chance of better mixing. At a Re of , the axial velocity profile reaches its peak for both the modified combustors, although at different locations. Specifically, the magnitude of the axial velocity profile is 1.05 at the position of 0.14 m for the rectangular restriction and 0.10 m for the spherical restriction. Consequently, a higher Reynolds number may be recommended for optimal mixing.
Effect of internal load and temperature on graded spherical shell
(Indian Maritime University, Kolkata Campus, 2023) Balmiki, Sanjay; Saha, Sujoy
In this work, the effect of internal pressure in a functionally graded hollow spherical shell is theoretically studied. The material properties through the graded direction are assumed to be non-linear with power law distribution. In order to obtain the effect of internal pressure and temperature on the design of pressure vessel, Navier and heat conduction equations are solved by direct method. The pressure variation and the mechanical stress distribution such as radial stress distribution and hoop stress distribution along the radial direction are presented in a sequential manner. The radial distribution of temperature has also been depicted in the result and discussion section. As a result of which it may be concluded that the material which has lower power law index is beneficial in terms of generation of lower thermal stress. The study also aims to understand the influence of autofrettage on stress distribution and load bearing capacity in thick spherical shells. Analytical equations, based on the Maximum Shear Stress theory and Distortion Energy theory, are derived to determine the optimum radius of the elastic-plastic juncture, known as 𝐶𝑜𝑝𝑡 in autofrettage technology. The results demonstrate that autofrettage increases the pressure inside the shell, enhancing its ability to withstand higher internal pressures.
Enhancement of heat transfer of laminar flow of viscous oil through a circular tube having integral axial rib roughness and fitted with helical screw-tape inserts
(Begell House Inc., 2012-01-01) Saha, Sujoy
The experimental friction factor and Nusselt number data for laminar flow through a circular duct having integral axial rib roughness and fitted with helical screw-tape inserts have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts in combination with integral axial rib roughness perform better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of the fin parameter.
MHD Laminar Modeling and Numerical Simulation on Ferromagnetic Fluid Flow in a Channel /
(Begell house inc., 2016-01-01) Saha, Sujoy
This study numerically investigated two dimensional, incompressible, Newtonian and electrically conducting laminar fluid flow characteristics under the consideration of MHD phenomenon. In this work the water base magnetic fluid, flowing through a channel under the action of magnetic field, is applied along axial direction, has been considered. The computational investigation has been performed with respect to the formation of stream line contour, vorticity magnitude contour, tangential velocity contour, wall static pressure, and wall shear stresses. The continuity and momentum equations, considering laminar and Magneto hydro dynamics (MHD) are solved for magnetic number arising from MHD of 3.66 and for Reynolds numbers ranging from 80 to 200. The above mentioned flow characteristics have a greater importance in case of various industrial applications such as diffuser, combustor, heat exchanger, mixing chamber, industrial equipment, chemical processing unit etc., which are worth mentioning.
Numerical design on annular dump combustor of a ship
(Indian Maritime University, Kolkata Campus, 2022-08) Soni, Vaibhav; Saha, Sujoy