In this paper we compute the numerical solutions of Navier-Stokes equationsin the case of the two dimensional disk impulsively started in a uniform back-ground flow. We shall solve the Navier-Stokes equations (for different Reynoldsnumbers ranging from 1.5 · 10^3 up to 10^5 ) with a fully spectral numericalscheme. We shall give a description of unsteady separation process in terms oflarge and small scale interactions acting over the flow. The beginning of theseinteractions will be linked to the topological change of the streamwise pressuregradient on the disk. Moreover we shall see how these stages of separation arerelated to the complex singularities of the solution. Infact the analysis of thespectrum of the angular velocity component is carried out by using the sin-gularity tracking method, and in particular we shall see how the behavior ofthe rate of exponential decay in time is influenced by the presence of large andsmall scale interactions.
|Numero di pagine||9|
|Stato di pubblicazione||Published - 2010|