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| Author(s): |
Ricardo Alberto Coppola Germanos
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD) |
| Defense date: | 2009-02-05 |
| Examining board members: |
Marcello Augusto Faraco de Medeiros;
Paulo Celso Greco Junior;
Márcio Teixeira de Mendonça;
Carlos Anissem Soares Moser;
Savio Brochini Rodrigues
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| Advisor: | Marcello Augusto Faraco de Medeiros |
| Abstract | |
Aerospace applications are frequently associated with compressible flows at relatively high Reynolds number. Nevertheless important applications involve compressible flows at relatively low Reynolds number in the aerospace context. Among them, the flow on gas turbine blades and high lift devices such as slats and flaps at high angle of attack are particulary important. Besides, progress in aeroespace research is dependent on developing more efficient propulsion systems. In aerodynamic applications at low Reynolds number, often a substancial portion of the flow is in the transition regime, or in the initial stages of a turbulent flow. The objective of the present study is the Direct Numerical Simulation of three-dimensional transition of compressible flows in a mixing layer. Inspired on the worked devoted to modulated waves, the current work investigates the linear and nonlinear temporal evolution of wavetrains in this phenomenon. The Navier-Stokes equations were solved with a sixth-order compact finite-difference schemes. The time integration was performed by a fourth-order Runge-Kutta scheme. Moreover, the methods to solve the spatial derivatives were modified to work with non-uniform grids. This technique was implemented with the objective to improve the resolution of the grid where the phenomenon occurs and to reduce the computational cost. The numerical investigation starts with an analysis of the growth rate of the wavetrains in linear regime to verify the numerical code. The results compared favourably with linear theory. Tests were also performed in the nonlinear regime to simulate the oblique wavetrains and it was possible to reproduce the classical hydrodynamic instability phenomena. (AU) | |