Browsing by Author "Rodriguez, Carlos G."

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    One-Dimensional, Finite-Rate Model for Gas-Turbine Combustors
    Rodriguez, Carlos G. (Virginia Tech, 1997-07-11)
    An unsteady, finite-rate, one-dimensional model has been developed for the analysis for gas-turbine combustors. The basis of the model is the one-dimensional, integral form of the conservation equations for multi-species, non-equilibrium, reacting mixtures. Special procedures were devised for the flow-division of the inlet flow into primary- and annular-flows, for both straight- and reverse-flow combustors. This allows the model to handle complete combustor configurations, which at present are beyond the reach of more sophisticated CFD tools. The model was validated with a steady-state analytical solution for a basic problem, and with steady-state results from a production code applied to a production combustor. Additional calculations show the ability of the code to predict blow-out due to rich and lean mixtures, and to predict the response of a combustor to perturbations in operating and boundary conditions.
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    Three dimensional flow analysis by the vortex-lattice method
    Rodriguez, Carlos G. (Virginia Tech, 1990)
    A Vortex-Lattice Method (VLM) has been developed for the analysis of three-dimensional lifting bodies undergoing arbitrary motions. So far, the present method has been applied to thin surfaces in translational motion. Several cases were tested, such as rectangular, delta, sweptback and trapezoidal planforms. Emphasis has been placed on the comparison of the results with available experimental data. Consequently, many of the strengths and limitations of the technique were made apparent. Good agreement has been obtained for the aerodynamic coefficients, with a relatively coarse discretization of the surface. Results are valid as long as there is no separation or vortex breakdown. However, accurate pressure distribution calculations need at least three or four times the number of panels used for aerodynamic coefficients calculations. The method gives a qualitative description of the wake configuration, but unrealistically high velocities are induced near the vortex elements. Work is underway to extend the technique to more general types of bodies and maneuvers.
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    Viscous-inviscid interaction for incompressible flows over airfoils
    Rodriguez, Carlos G. (Virginia Tech, 1993)
    This thesis presents the results obtained so far in an investigation concerning viscous effects in incompressible flows over airfoils. These effects are taken into account by assuming the existence of a boundary layer which interacts with an external inviscid flow. Numerical methods for solving the inviscid and boundary-layer flows are briefly described. The main objective of the investigation is the development of an interaction technique between both regions of flow. The method chosen for the interaction is the so-called semi-inverse procedure. This procedure is derived from a perturbation analysis of the linearized versions of the governing equations. The resulting method is subjected to a stability analysis, which shows that it will break down when used in conjunction with separated-flow boundary-layer solvers. The semi-inverse procedure is tested on several airfoils, using an attached-flow boundary-layer solver. Numerical results show that the method is sufficiently accurate for engineering purposes in the low-to-medium range of angles of attack, but its applicability is questionable when there is a large separation region. Finally, recommendations are made regarding future work to overcome the limitations of the present technique.