Effects of radiation and chemical reaction on MHD flow past a vertical plate with variable temperature and mass diffusion
This research investigates the effects of radiation, chemical reaction and porosity of the medium on unsteady flow of a viscous, incompressible and electrically conducting fluid past an exponentially accelerated vertical plate with variable wall temperature and mass diffusion in the presence of transversely applied uniform magnetic field. The plate temperature and the concentration level near the plate increase linearly with time. The fluid model under consideration has been solved by Laplace transform technique. The model contains equations of motion, diffusion equation and equation of energy. To analyze the solution of the model, reasonable sets of the values of the parameters have been considered. The numerical data obtained is discussed with the help of graphs and tables. The numerical values obtained for skin-friction, Sherwood number and Nusselt number have been tabulated. It is found that the velocity of fluid increases when the values of permeability parameter, acceleration parameter and radiation parameter are increased. But trend is reversed with the chemical reaction parameter. It means that the velocity decreases when the chemical reaction parameter is increased.
Journal of Naval Architecture and Marine Engineering; Vol. 16 No. 2 (2019); 99-108
Association of Naval Architects and Marine Engineers
Copyright (c) 2019 Journal of Naval Architecture and Marine Engineering
Motion predictions of ships in actual operating conditions using potential flow based solver
Prediction of ship's response in real voyage condition is essential for efficient ship design. At sea, ships rarely voyage in head wave conditions, and mostly prefer oblique waves for lower resistance and better propulsion. This paper provides oblique wave simulation results for a container, tanker and bulk carrier using a commercial potential flow (PF) based solver, HydroSTAR. Although, PF codes have limitation regarding resistance prediction, they are well reliable in predicting ship motion in waves. The paper aims at providing a relative comparison of ship resistance and motion in different heading angles for three major ship models namely KCS, KVLCC2 and JBC. The paper should prove useful to shippers in case of weather routing or route selection for voyage.
Journal of Naval Architecture and Marine Engineering; Vol. 14 No. 1 (2017); 65-76
Copyright (c) 2017 Journal of Naval Architecture and Marine Engineering
Wave interaction with Floating platform of different shapes and supports using BEM approach
Wave interaction with a floating thin elastic plate which can be used as floating platform is analyzed using Boundary Element Method (BEM) for different shapes such as rectangular, circular and triangular. Different support conditions are considered and the performance of the floating platform under the action of ocean waves is explored. The study is performed under the assumption of linearized water wave theory and the floating elastic plate is modelled based on the Euler-Bernoulli beam theory. Using Galerkins approach, a numerical model has been developed and the hydrodynamic loading on the floating elastic plate of shallow draft (thickness) is investigated. The wave forces are generated by the numerical model for the analysis of the floating plate. The resulting bending moment and optimal deflection due to encountering wave force is analysed. The present study will be helpful in design and analysis of the large floating platform in ocean waves.
Journal of Naval Architecture and Marine Engineering; Vol. 14 No. 2 (2017); 115-133
A preliminary study of the pressure and shear stress on a plane surface beneath a circular cylinder in turbulent flow fields
This paper studies the fluctuating forces on a plane surface beneath a circular cylinder in the subcritical flow regime using two-dimensional computational fluid dynamics (CFD). The turbulent flow fields were calculated via numerical solutions of the NavierStokes (NS) equations without a turbulence model (laminar flow computation), large eddy simulation (LES), and Reynolds-Averaged N-S equations (RANS) approach with the shear-stress transport (SST) turbulence model. The primary goal is to evaluate the performance of 2-D turbulence simulation with different approaches and to have preliminary knowledge of the forces on the plane which is important in studying scours and flow-induced vibration in ocean engineering. Results show that although a coarse mesh scheme can only obtain potential flows, the laminar approach with high mesh resolution can adequately simulate turbulent flows at moderate Reynolds numbers. Spatially, the fluctuating forces on the plane surface due to the flow are significant within three times the cylinder diameter in the downstream, and within one cylinder diameter in the upstream of the cylinder. The pressure fluctuations are approximately two orders of magnitude larger than the shear stress fluctuations. In the frequency domain, the fluctuating forces are significant under twice the vortex-shedding frequency. Within one cylinder diameter in the downstream and upstream regions of the cylinder, the pressure fluctuations on the plane surface are well correlated, while the shear stress is not so well correlated.
Journal of Naval Architecture and Marine Engineering; Vol. 14 No. 1 (2017); 9-24
Assisted convective heat transfer and entropy generation in a solar collector filled with nanofluid
Heat transfer phenomena of flat plate solar collector filled with different nanofluids has been investigated numerically. Galerkins Finite Element Method is used to solve the problem. Heat transfer rate, average bulk temperature, average sub-domain velocity, outlet temperature, thermal efficiency, mean entropy generation and Bejan number has been investigated by varying the solid nanoparticle volume fraction of water/Cu, water/Ag and water/Cu/Ag nanofluids from 0% to 3%. It is found that the solid nanoparticle volume fraction has great effect on heat transfer phenomena. It is observed that the increases of the solid volume fraction (up to 2%) enhances the heat transfer rate and collector efficiency where after 2% the rate of change almost constant. Higher heat transfer rate and collector efficiency has been obtained 19% and 13% for water/Ag nanofluid respectively.
Journal of Naval Architecture and Marine Engineering; Vol. 13 No. 2 (2016); 135-150
Copyright (c) 2016 Journal of Naval Architecture and Marine Engineering
Stress distribution in CNT-Aluminum matrix composite by changing distances between CNT bundles
Carbon Nanotubes (CNTs) are identified as exceptional in terms of mechanical, electrical, magnetic and optical properties. CNT based composites are also playing a vital role in several fields of science. In this research, four bundles of CNTs with square Representative Volume Element (RVE) is used and ANSYS Multiphysics 11.0 software is used for simulation purpose. In this study, stress distribution of CNT based Aluminum composite is noticed by changing distances of CNT bundles. Stress distribution and transverse Youngs Modulus are investigated by changing different parameters. From this study it can be known how CNT bundles can be formed together to increase or decrease stress. The brief result is that, if the distance of CNT center from reference point is increased then the stress is decreased.
Journal of Naval Architecture and Marine Engineering; Vol. 13 No. 2 (2016); 125-133
Numerical estimation of shallow water effect on multipurpose amphibious vehicle resistance
This research paper investigated the hydrodynamic resistance of Multipurpose Amphibious Vehicles (MAV) due to navigate in low water depth numerically. This type of vehicle and other coastal floating vehicles encounter the problem of a small under keel clearance with river bed. The proper estimation of ship resistance and squat is influence largely on the power calculation in the design stage. The present work describes the effect of shallow water on the Multipurpose Amphibious Vehicles (MAV) resistance at different speed using Computational Fluid Dynamics (CFD) techniques. A comparison in the drag on the hull is illustrated between depth restriction and infinite depth water. This paper provides a wide introduction into the problems of modelling of the restricted water depth effects on the ship behaviour, specifically hydrodynamic resistance and squat using CFD which is applied by ANSYS-CFX14.0.
Journal of Naval Architecture and Marine Engineering; Vol. 14 No. 1 (2017); 1-8
Numerical simulation of turbulent boundary layers of surfaces covered with foul release and antifouling coatings
In order to compare the frictional resistance of three kinds of ships hull coatings (Foul Release, SPC copper, SPC TBT) in the unfouled conditions, the numerical studies have been made. Simulations have been carried out for different Reynolds numbers in the range of 2.85 × 5.5 × based on the plate length and flow velocity. Antifouling coatings have a larger mean roughness than Foul Release. The results have indicated that frictional resistance coefficient of Foul Release test plate is lower than SPC copper and SPC TBT test plates. The total resistance obtained by computational fluid dynamics has been compared with the experimental data and good agreement in results has been found which those have shown the ability of CFD modeling in calculating of fluid flow resistance by considering the coating characteristics.
Journal of Naval Architecture and Marine Engineering; Vol. 13 No. 1 (2016); 17-26
Dual solutions for heat and mass transfer in chemically reacting radiative non-Newtonian fluid with aligned magnetic field
Through this paper we investigated the heat and mass transfer in chemically reacting radiative Casson fluid flow over a slandering/flat stretching sheet in a slip flow regime with aligned magnetic field. This study is carried out under the influence of non uniform heat source/sink. First we converted the governing equations of the flow into ordinary differential equations by making use of suitable similarity transformations. The obtained non-linear differential equations are solved numerically using Runge-Kutta based shooting technique. Further, graphical representation has been given to study the effects of various physical parameters on velocity, temperature and concentration fields. Also numerical computations has been carried out to investigate the influence of the physical parameters involved in the flow on skin friction, rate of heat and mass transfer coefficients. Through this investigation, it is observed that aligned angle, Casson parameter and velocity slip parameter have the tendency to control the velocity field. Also heat transfer rate in flat stretching sheet is higher than that of slendering stretching sheet. A good agreement of the present results with the existed literature has been observed.
Journal of Naval Architecture and Marine Engineering; Vol. 14 No. 1 (2017); 25-38
Numerical simulation of vortex induced vibration in heat exchanger tube bundle at low Reynolds number
It is sound recognized that when the tube is forced to vibrate or is naturally excited to sufficient amplitudes by flow-induced forces, cyclones peeling phenomena arises at downstream of a tube which clues to vibration in the tube. Two-dimensional numerical recreation model for the computation of flow induced vibration of heat exchanger tube bundle imperiled to cross- flow is proficient in current research. Computational Fluid Dynamics (CFD) tool, GAMBIT (grid generation) and ANSYS FLUENT (fluid flow analysis) are operated during numerical investigations. k-epsilon model is used to solve the Navier Stokes equations. Lift coefficient graph derived from analysis is used to predict the vortex shedding frequency using Fast Fourier Transform (FFT). The results of flow rate, Strouhal number, Reduced velocity, Natural frequency of tube as found from the experimental data has been verified numerically for a Reynolds number range of 4.45 × 104<Re <4.65 × 104 . It is concluded that experimental results are well in agreement with the numerical results.
Journal of Naval Architecture and Marine Engineering; Vol. 14 No. 2 (2017); 77-91