Muhammad Noman Hasan

Numerical Analysis of Droplet Impact, Deformation of a Droplet Train in Direct Print Technology

Numerical analysis for a two dimensional case of two–phase fluid flow has been performed to investigate droplet impact, deformation for a droplet train. The purpose of this investigation is to study the phenomenon of liquid droplet impact on a liquid film created by a flattened droplet and the consequent deformation of the film while merging and advancing of the moving front of the film, during the manufacturing processes with jetting technology such as a direct printing process and inkjet printing. This investigation focuses on the analysis of interface tracking and the change of shape for an impacted droplet of a dispensed material. Investigations have been made on the performance of an adaptive quadtree spatial discretization with geometrical Volume–Of–Fluid (VOF) interface representation, continuum–surface–force surface tension formulation and height-function curvature estimation for interface tracking during droplet impact deformation and coalescence of droplet and liquid film produced by flattened droplets to form a printed line. Gerris flow solver, an open source finite volume code, has been used for the numerical analysis which uses a quadtree based adaptive mesh refinement for 2D. The results have been compared with an experimental result from the literature. The investigation has been performed for Reynolds number, Re of 21.1; Weber number, We of 93.8, and contact angle, θ of 30°. For the experimental result considered, the frequency of jetting is 12 kHz.Copyright

Mixed Convection Over a Horizontal Plate With Streamwise Non-Uniform Surface Temperature Distribution

Numerical investigation on mixed convection of a two-dimensional incompressible laminar flow over a horizontal flat plate with streamwise sinusoidal distribution of surface temperature has been performed for different values of Rayleigh number, Reynolds number and frequency of periodic temperature for constant Prandtl number and amplitude of periodic temperature. Finite element method adapted to rectangular non-uniform mesh elements by a non-linear parametric solution algorithm basis numerical scheme has been employed. The investigating parameters are the Rayleigh number, the Reynolds number and frequency of periodic temperature. The effect of variation of individual investigating parameters on mixed convection flow characteristics has been studied to observe the hydrodynamic and thermal behavior for while keeping the other parameters constant. The fluid considered in this study is air with Prandtl number 0.72. The results are obtained for the Rayleigh number range of 102 to 104, Reynolds number ranging from 1 to 100 and the frequency of periodic temperature from 1 to 5. Isotherms, streamlines, average and local Nusselt numbers are presented to show the effect of the different values of aforementioned investigating parameters on fluid flow and heat transfer.