Subhransu Roy

Numerical simulation of two-dimensional room air flow with and without buoyancy

This investigation deals with the velocity and temperature distribution in a room heated by a warm air stream introduced at various levels. Numerical solutions of Navier Stokes equations and energy equation have been obtained by SIMPLE and Semi Implicit Method for Pressure Linked Equation-Consistent (SIMPLEC) algorithms. Steady, laminar, and incompressible flow under Boussinesqs approximation has been considered. Solutions are presented for various locations of inlets and outlets, and for different values of Grashof number and Reynolds number. If the outlet is located at a lower level than the inlet, an increase in Gr makes the warm jet almost horizontal, which finally bends downwards towards the exit. An increase in Gr increases the intensity of recirculation and yields uniform temperature distribution. Location of outlet at higher level than the inlet leads to better temperature distribution.

The Effect of Marangoni-Rayleigh-Benard Convection on the Process Parameters in Blown-Powder Laser Cladding Process—A Numerical Investigation

A two-dimensional model has been developed for the blown-powder laser cladding process to study the influence of Marangoni-Benard and Rayleigh-Benard convection on the process parameters: average dilution, maximum and average melt pool temperatures. Dimensionless governing equations are solved by the finite-volume method. It is found that for Marangoni number, Ma < 0 dilution decreases whereas for Ma > 0 dilution increases slightly. Rayleigh-Benard convection reduces dilution, but its effect is more prominent for Ma > 0 and lower scanning speed. Maximum and average melt pool temperatures fall due to convective heat transfer. However, the reduction in temperature with Ma ≠ 0 is significant only at low scanning speeds, i.e., U* < 2.

Three-Dimensional Numerical Investigation of Thermodynamic Performance Due to Conjugate Natural Convection From Horizontal Cylinder With Annular Fins

This book presents the natural convection heat transfer from a horizontal cylinder with annular fins has been studied numerically. The present numerical investigation is able to capture a complete picture of natural convection over an annular finned horizontal cylinder from where easy visualization of the plume structure and flow field over the tube-fin surface can be obtained pictorially. In the present study, numerical simulations of full Navier-Stokes equation along with the energy equation have been conducted for a horizontal tube with annular fins of constant thickness by varying the Rayleigh number based on fin spacing. Chapter 1 deals with the introduction and literature survey regarding the natural convection heat transfer from horizontal cylinder with annular fins. In Chapter 2, a complete numerical analysis of natural convection from horizontal cylinder with annular fins by varying fin diameter, fin spacing and Rayliegh number. A similar analysis is carried out in chapter 3, taking eccentric fins on horizontal cylinder and results are compared with the concentric one. In chapter 4, an entropy generation analysis of finned tube configuration has been carried out.

Turbulent statistics in flow field due to interaction of two plane parallel jets

Turbulent characteristics of flow fields due to the interaction of two plane parallel jets separated by the jet width distance are studied. Numerical simulation is carried out by large eddy simulation with a dynamic Smagorinsky model for the sub-grid scale stresses. The energy spectra are observed to follow the −5/3 power law for the inertial sub-range. A proper orthogonal decomposition study indicates that the energy carrying large coherent structures is present close to the nozzle exit. It is shown that these coherent structures interact with each other and finally disintegrate into smaller vortices further downstream. The turbulent fluctuations in the longitudinal and lateral directions are shown to follow a similarity. The mean flow at the same time also maintains a close similarity. Prandtl’s mixing length, the Taylor microscale, and the Kolmogorov length scales are shown along the lateral direction for different downstream locations. The autocorrelation in the longitudinal and transverse directions ...

Particle Image Velocimetry Measurements of Rigid and Flexible Rectangular Wings Undergoing Main Flapping Motion in Hovering Flight

The present work is focused on flow field behavior generated by rigid and flexible rectangular wings undergoing main flapping motion using two dimensional Particle Image Velocimetry (PIV). The experiments have been carried for an asymmetry one degree of freedom main flapping motion of both rigid and flexible low aspect ratio wings at 1 Hz flapping frequency in hovering flight mode (advanced ratio, J = 0) at zero geometric angle of attack, zero wing pitch angle and chord wise based Reynolds number of the order of 104 along the wings spanwise direction at its mid chord to obtain instantaneous flow fields. The improved understanding of effect of wake capture, observation of spanwise flow on the wing, and formation-growth-diffusion of wingtip vortices have been achieved. Effect of wing flexibility on the flow field has been studied by comparing the flow field of both rigid and flexible rectangular wings undergoing main flapping motion.