title: Sharp Transition in the Lift Force of a Fluid Flowing Past Nonsymmetrical Obstacles: Evidence for a Lift Crisis in the Drag Crisis Regime.
abstract: Bluff bodies moving in a fluid experience a drag force which usually increases with velocity. However in a particular velocity range a drag crisis is observed, i.e., a sharp and strong decrease of the drag force. This counterintuitive result is well characterized for a sphere or a cylinder. Here we show that, for an object breaking the up-down symmetry, a lift crisis is observed simultaneously to the drag crisis. The term lift crisis refers to the fact that at constant incidence the time-averaged transverse force, which remains small or even negative at low velocity, transitions abruptly to large positive values above a critical flow velocity. This transition is characterized from direct force measurements as well as from change in the velocity field around the obstacle.
authors.affiliation: Naval Academy Research Institute, IRENAV CC600, 29240 Brest Cedex 9, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Bot
authors.affiliation: Laboratoire FAST, Univ. Paris-Sud, CNRS, Université Paris-Saclay, F-91405 Orsay, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Rabaud
authors.affiliation: Naval Academy Research Institute, IRENAV CC600, 29240 Brest Cedex 9, France.
authors.forename: Goulven
authors.initials: G
authors.lastname: Thomas
authors.affiliation: Naval Academy Research Institute, IRENAV CC600, 29240 Brest Cedex 9, France.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lombardi
authors.affiliation: Naval Academy Research Institute, IRENAV CC600, 29240 Brest Cedex 9, France.
authors.forename: Charles
authors.initials: C
authors.lastname: Lebret