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Computational Fluid Dynamic (CFD) has an important assignment in fluid mechanics, including droplet cases. Finite-difference and front-tracking methods were used in numerical simulations of collisions of liquid droplets on horizontal solid surfaces. This study aims to model the dynamics of a single droplet impacting the horizontal surface with variations of density ratio and gravity. The numerical simulation of the droplet phenomena solution used finite difference method with an implicit scheme. The interface between different phases was tracked by using a front tracking method. The governing equations used continuity and momentum Navier-Stokes equation for incompressible 2-D unsteady flow immiscible fluid where the surface tension be discovered, and the viscosity fluid assumed constant. The Navier-Stokes equations were discretized using the implicit finite difference method on a staggered grid pattern with primitive variable formulation (u, v, p). The pressure term was solved by using the Poisson equation at Neumann boundary conditions. Initial conditions were conducted to the diameter of the droplet of 2.5 mm, and height fall of 0.125 cm with a static contact angle of 90°. The numerical results were validated with the research of Meten Muradog et al. (2010), and the spreading dynamics of the droplet was investigated. The studies show that gravity was dominant to the maximum deformation diameter, and the maximum spreading velocity will increase at a higher density ratio. The greater the density ratio, then droplet height decreases. [ABSTRACT FROM AUTHOR]

CFD tools have an important benchmark problem, and the lid-driven cavity is one of the most outstanding tools. This paper presents the benchmark tool for CFD simulation of a lid-driven cavity, examining the particular case of top-and-bottom moving boundary conditions. The governing equation that is used is an unsteady Navier-Stokes equation in a primitive variable formulation. The solution method is implicit finite difference with staggered grid. The result is a symmetrical vortex with half top and lower part. The Reynolds number was varied between 100, 500,1000, 4000 and 10000. In this paper we also present the secondary vortex in some circumstances. The velocity profile in a quarter, half and three-fourth full x and y axis is also presented. [ABSTRACT FROM AUTHOR]