Sumários
INSTABILITY AND TRANSITION
21 março 2022, 17:00 • Carlos Frederico Neves Bettencourt da Silva
Origin of turbulence: dynamical systems and chaos. Logistic map and the Lorentz equations. The Kelvin-Helmholtz instability. Linear-Stability analysis. Stability of parallel flows and the Orr-Sommerfeld equations. The Tollmien-Schlichting waves. Secondary instabilities in boundary layers and jets. Hairpin vortices in boundary layers and vortex rings in circular jets. The preferred jet mode.
VORTICITY DYNAMICS (cont.)
18 março 2022, 17:00 • Carlos Frederico Neves Bettencourt da Silva
(Continuation from the previous lecture): Vorticity: definition, circulation, Biot-Savart law, Helmholtz law, Kelvin theorem. Vorticity and enstrophy governing equations: production, diffusion, dissipation of enstrophy. Vorticity and vortices: Lamb-Ossen, Rankine, Burgers vortices. Vorticity and turbulence.
LABORATORY AND COMPUTATIONAL WORK: acquisition of velocity time signals in a free turbulent jet; use of a 2d Navier-Stokes solver to solve a given problem
17 março 2022, 17:00 • Carlos Frederico Neves Bettencourt da Silva
The experimental work took place in several session where each team of students acquired the instantaneous velocity signal at several jet locations using a hot wire anemometer (potential core, intermittent region, centerline (several locations). Each one of the teams of students latter used their data to compute and explain the evolution of several turbulent quantities; In the computational project the students were given a 2d Navier-Stokes solver and were assigned several problems to solve, requiring an analysis of the evolution of several unsteady flow phenomena. Both the laboratory and computational projects were supported through several sessions of discussion with the students. Both works required a report and the classifications were given after a discussion with each team of students.
VORTICITY DYNAMICS
14 março 2022, 17:00 • Carlos Frederico Neves Bettencourt da Silva
Vorticity: definition, circulation, Biot-Savart law, Helmholtz law, Kelvin theorem. Vorticity and enstrophy governing equations: production, diffusion, dissipation of enstrophy. Vorticity and vortices: Lamb-Ossen, Rankine, Burgers vortices. Vorticity and turbulence.
EQUATIONS OF FLUID MECHANICS
11 março 2022, 17:00 • Carlos Frederico Neves Bettencourt da Silva
Equations of fluid mechanics: Knudsen number and the continum assumption. Convective derivative. Mass conservation. Navier-Stokes equations. Dissipation in a viscous fluid.