Nonlinear control of unsteady finite-amplitude perturbations in the Blasius boundary-layer flow
Article dans une revue avec comité de lecture
JournalJournal of Fluid Mechanics
The present work provides an optimal control strategy, based on the nonlinear Navier–Stokes equations, aimed at hampering the rapid growth of unsteady finite-amplitude perturbations in a Blasius boundary-layer flow. A variational procedure is used to find the blowing and suction control law at the wall providing the maximum damping of the energy of a given perturbation at a given target time, with the final aim of leading the flow back to the laminar state. Two optimally growing finite-amplitude initial perturbations capable of leading very rapidly to transition have been used to initialize the flow. The nonlinear control procedure has been found able to drive such perturbations back to the laminar state, provided that the target time of the minimization and the region in which the blowing and suction is applied have been suitably chosen. On the other hand, an equivalent control procedure based on the linearized Navier–Stokes equations has been found much less effective, being not able to lead the flow to the laminar state when finite-amplitude disturbances are considered. Regions of strong sensitivity to blowing and suction have been also identified for the given initial perturbations: when the control is actuated in such regions, laminarization is also observed for a shorter extent of the actuation region. The nonlinear optimal blowing and suction law consists of alternating wall-normal velocity perturbations, which appear to modify the core flow structures by means of two distinct mechanisms: (i) a wall-normal velocity compensation at small times; (ii) a rotation-counterbalancing effect al larger times. Similar control laws have been observed for different target times, values of the cost parameter, and streamwise extents of the blowing and suction zone, meaning that these two mechanisms are robust features of the optimal control strategy, provided that the nonlinear effects are taken into account.
Files in this item
- jfm control
Showing items related by title, author, creator and subject.
Article dans une revue avec comité de lectureFARANO, Mirko; CHERUBINI, Stefania; ROBINET, Jean-Christophe; DE PALMA, Pietro; SCHNEIDER, T. M. (Cambridge University Press (CUP), 2018)Transitional turbulence in shear flows is supported by a network of unstable exact invariant solutions of the Navier–Stokes equations. The network is interconnected by heteroclinic connections along which the turbulent ...
Article dans une revue avec comité de lecturePARENTE, ENZA; ROBINET, Jean-Christophe; DE PALMA, Pietro; CHERUBINI, Stefania (Cambridge University Press, 2022)Recently, many authors have investigated the origin and growth of turbulent bands in shear flows, highlighting the role of streaks and their inflectional instability in the process of band generation and sustainment. ...
Article dans une revue avec comité de lecturePARENTE, Enza; FARANO, Mirko; ROBINET, Jean-Christophe; DE PALMA, Pietro; CHERUBINI, Stefania (The Royal Society Publishing, 2022-05)A new mathematical framework is proposed for characterizing the coherent motion of fluctuations around a mean turbulent channel flow. We search for statistically invariant coherent solutions of the unsteady Reynolds-averaged ...
Article dans une revue avec comité de lecturePARENTE, Enza; ROBINET, Jean-Christophe; DE PALMA, Pietro; CHERUBINI, Stefania (American Physical Society, 2020)The modal and nonmodal linear stability of a stably stratified Blasius boundary layer flow, composed of a velocity and a thermal boundary layer, is investigated. The temporal and spatial linear stability of such flow is ...
Article dans une revue avec comité de lectureMANCINI, C.; FARANO, Mirko; DE PALMA, Pietro; ROBINET, Jean-Christophe; CHERUBINI, Stefania (Elsevier, 2017)This work describes the development of a method for the global hydrodynamic stability analysis of diffusion flames. The low-Machnumber (LMN) Navier–Stokes (NS) equations for reacting flows are solved together with a transport ...