Publication

Optimal open-loop control of the recirculation length in the wake of a cylinder

2012
Talks

Abstract

We consider steady equilibrium solution of the 2-D Navier-Stokes equations describing the flow around a circular cylinder. It is well known that, for moderate Reynolds numbers, the recirculation length is an increasing function of the Reynolds number. We first express the recirculation length as a cost-functional and then use a Lagrangian-based optimization procedure to compute the linear sensitivity of the recirculation length with respect to base flow modifications, localized bulk point forces and blowing and suction at the cylinder wall. The results are compared to nonlinear steady-state computations. The influence of a shortened or increased recirculation on the stability of the flow above threshold (Re=47) is finally discussed.

Official source

https://infoscience.epfl.ch/entities/publication/422d6040-c919-4df7-95d0-e44760c8a375

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2012
Talks

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/422d6040-c919-4df7-95d0-e44760c8a375

About this result

Related concepts (32)

Navier–Stokes equations

The Navier–Stokes equations (nævˈjeː_stəʊks ) are partial differential equations which describe the motion of viscous fluid substances, named after French engineer and physicist Claude-Louis Navier and Irish physicist and mathematician George Gabriel Stokes. They were developed over several decades of progressively building the theories, from 1822 (Navier) to 1842-1850 (Stokes). The Navier–Stokes equations mathematically express momentum balance and conservation of mass for Newtonian fluids.

Reynolds number

In fluid mechanics, the Reynolds number (Re) is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers, flows tend to be turbulent. The turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents).

Fluid dynamics

In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.

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Optimal open-loop control of the recirculation length in the wake of a cylinder

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