Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step

• Type: Article in International Scientific Journal
• Date: 2019

Authors

Afonso, MM (Author) FCUP; Meliga, P (Author) Other; Serre, E (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: FLUIDS

Vol. 4

Final page: 33

ISSN: 2311-5521

Indexing

ISI Web of Knowledge - 0 Citations

Scopus - 1 Citation

Other information

Authenticus ID: P-00Q-DYG

DOI: 10.3390/fluids4010033

Abstract (EN): With the aim of providing a first step in the quest for a reduction of the aerodynamic drag on the rear-end of a car, we study the phenomena of separation and reattachment of an incompressible flow by focusing on a specific aerodynamic geometry, namely a backward-slanted step at 25 circle of inclination. The ensuing recirculation bubble provides the basis for an analytical and numerical investigation of streamwise-streak generation, lift-up effect, and turbulent-wake and Kelvin-Helmholtz instabilities. A linear stability analysis is performed, and an optimal control problem with a steady volumic forcing is tackled by means of a variational formulation, adjoint methods, penalization schemes, and an orthogonalization algorithm. Dealing with the transient growth of spanwise-periodic perturbations, and inspired by the need of physically-realizable disturbances, we finally provide a procedure attaining a kinetic-energy maximal gain on the order of 106, with respect to the power introduced by the external forcing.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 16