arXiv subjects

Vishwanath Kadaba Puttanna

Publications and source records attributed to Vishwanath Kadaba Puttanna.

3 recordsLinked to original sources

arXiv2026

Aggregation Effects on Heat Transfer in Viscoplastic Nanofluid Entrance Flows

This study numerically investigates heat transfer enhancement in laminar, incompressible viscoplastic nanofluid flow through the entrance region of a circular cylinder with a uniformly heated wall, including the effects of both, non-aggregation and aggregation of nanoparticles. Nanofluid properties are modeled using Brinkman and Maxwell models in the case of non-aggregation, and Krieger-Dougherty, Maxwell-Bruggeman models in the case of aggregation, while the viscoplastic behavior is described by the Bingham-Papanastasiou model. The governing boundary layer equations are solved using a finite-difference method. The effects of yield stress and nanoparticle volume fraction (up to 5%) on friction, pressure drop, and Nusselt number are analyzed, and performance evaluation criteria are evaluated to identify the optimal volume fraction for maximum efficiency.

physics.flu-dyn↗

arXiv2026

Nonlocal flow sampling enables vortex trapping of heavy particles

Most analyses of inertial particle motion in vortical flows rely on the point-particle approximation, in which the fluid velocity is assumed to be linear at the scale of the particle, and for heavy particles inertia typically leads to centrifugal expulsion from vortex cores. Here, we show that a spatially extended particle, modeled as a rigid symmetric dumbbell of two identical inertial point particles connected by a massless rod that samples the flow at two points, can converge to a vortex-centered spinning state. We study the dynamics of this inertial dumbbell in a steady two-dimensional Lamb-Oseen vortex and identify three qualitatively distinct long-time behaviors controlled by the Stokes number. In the weak-inertia limit, the motion remains bounded and traces spirographic-like trajectories around the vortex center, while at sufficiently large inertia centrifugal effects dominate and trajectories spiral outward, approaching inertial point-particle behavior. Between these limits, the dumbbell can reach a trapped spinning state in which the center-of-mass converges to the vortex center and spins steadily, with accessibility determined by the initial conditions. Basin-of-attraction maps and ensemble statistics reveal a non-monotonic dependence of the accessibility of the spinning state on inertia, with basins of finite measure occurring only over an intermediate range of Stokes numbers. Linear stability is governed by the logarithmic slope of the vortex angular-velocity profile, and for the Lamb-Oseen vortex the spinning state is stable for all Stokes numbers. These results highlight how nonlocal flow sampling by spatially extended inertial particles can fundamentally alter transport and long-time behavior in vortical flows.

physics.flu-dyn↗

arXiv2024

Electrostatic force between two charged spherical conductors in an electric field: Matched asymptotic expansion approach

In this study, we derive the asymptotic expressions for the electrostatic force between two charged spherical conductors in an electric field. Davis \cite{davis1964two} initially provided an expression for these forces, which are split into components along the X and Z directions. These forces are influenced by several factors, including the separation distance between the spheres, their sizes, their charges, the applied external electric field, and 10 specific force coefficients. These coefficients involve complex series expressions, and computing them requires summing up the 24 infinite series. To tackle the challenge of series convergence, previous researchers (\cite{lekner2012electrostatics}, \cite{lekner2013forces}, \cite{arp1977particle}) have used various methods to derive asymptotic expressions. In this work, the method of matched asymptotic expansions has been implemented to derive the asymptotic forms of these 24 series, specifically for the scenario involving two equal-sized conducting spheres in an external electric field. Accurate calculation of these series is crucial, especially when the distance between the spheres is very small, making the series calculations computationally intensive. We utilize the method proposed by Cox and Brenner \cite{Cox1967} to derive the asymptotic expressions and hence compute the 10 force coefficients and finally apply them to compute the electrostatic force for small separations. Additionally, we assess the accuracy of these asymptotic expressions by comparing them to the actual series and analyzing their deviations through percentage errors.

math-ph↗