Sergio Rojas

Ph.D. (Physics), The City College of The City University of New York, May 1998.

M.S. (Computational Finance), The Oregon Graduate Institute of Science and Technology, Feb 2001.

From August, 1992 to December, 1997, I was a Ph.D. student in the Physics program of The City College of the City University of New York ( CCNY). I was awarded the Ph.D. degree in Physics in May 29, 1998.

During my Ph.D. studies at CCNY, I worked extensively on the subject of Statistical Physics of Classically Disordered Systems and its applications to fluid flow through porous materials, which also allows me to gain substantial experience in the field of Computational Fluid Dynamics, particularly at low Reynolds number.

This stage of my education allows me to strength and became very knowledgeable on a variety of computer software and programming languages including FORTRAN, C, NEKTON (a CFD simulation software), Mathematica (a major symbolic computer software), and HTML. In addition, I also acquired a very strong working knowledge on the UNIX operating system (Silicon Graphics-IRIS, Digital-Solaris, Sun-SunOS, and PC-Linux), including C-shell scripting programming language.

My Ph.D. experience was very useful while working as a Researcher in the subject of Oil Reservoir Simulation for PDVSA-INTEVEP, a well known oil company in Venezuela. I was involved in a project to built a 3-D, 3-phases Oil Reservoir Simulator based on a Mixed Finite Element discretization model of the respective governing equations and Boundary conditions (most available commercial oil reservoir simulator are base on Finite Difference Methods). Among other things, such simulator would allow the fully testing of important empirical, semi-empirical, and theoretical relationships between reservoir permeability and the fluids (oil, water, and gas) saturation of the rock.

Following is the abstract of my Ph.D. Dissertation, and some of my publications.

Nonlinear flow in porous media

Rojas, Sergio Jesus

Professor Advisor: Koplik, Joel

Numerical solutions of the Navier-Stokes equations in two-dimensional quasi-periodic and quasi-isotropic random media were obtained to analyze the local and large scale aspects of finite Reynolds number flow. For Reynolds number less than one, the results show a first correction to Darcy's law which is cubic in the Darcy (averaged) velocity, while for Reynolds number greater than one, the results are in agreement with Forchheimer equation. That is, the correction to Darcy's law is quadratic in the average (Darcy) velocity. The cubic correction to Darcy's law support Mei and Auriault's (1991) theoretical study, based on homogenization theory. In addition, the results show support to a unifying empirical equation describing fluid flow in porous media of similar structure, first proposed by Beavers and Sparrow (1969). Also, the results show agreement, except by a multiplicative constant, with Sangani and Acrivos (1982) equation for the drag on dilute array of cylinders.

Publications

• Rojas, S., and Moody, J. (2001). "Cross-sectional analysis of the returns of iShares MSCI Index Funds using Independent Component Analysis". OGI CSE610 Internal Report, Oregon Graduate Institute of Science and Technology.
• Rojas, S., and Koplik, J. (1998). "Non-linear Flow in Porous Media". Phys. Rev. E. , 58(4), 4776.
• Rojas, S. (1998). "Non-linear Flow in Porous Media", Ph.D. Dissertation, The City University of New York, USA.
• Barreto, W., and Rojas, S. (1992), "An Equation of State for Radiating Dissipative Spheres in General Relativity". Astrophys. and Space Sci., 193(2), 201.
• Rojas, S. (1991). "Distribuciones de Materia Esféricas, Disipativas y Radiantes en Relatividad General", B.S. Dissertation, Universidad de Oriente, Venezuela.