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The goal of the paper is to investigate experimentally the Taylor-Lighthill-Païdoussis (TLP) model of fluid forces in axial flow, in the case of a cylinder array. This model consists of a 2D representation of the fluid forces, assuming that the local fluid forces depend only on the local rotation and velocity of the structure. The experimental setup consists of a wind tunnel with test section of length 2m and width 24cm surrounding a square array of 9x9 cylinders with pitch-to-diameter ratio of 1.33. The Reynolds number is about 10^5. The yaw angle of the central cylinder and its position relatively to its neighbours are adjustable. Velocity profiles are measured by means of thin Pitot-like tubes. The steady fluid forces exerted on the central cylinder are recorded using a 6-axis load cell. A boundary layer develops along some 20 diameters with an increase of the velocity maximum. Translating the central cylinder by 0.2D alters the channel velocity by 5-10%. The relationship between lift force and yaw angle shows a linear behaviour, with a proportionality coefficient in agreement with the literature inspired by the TLP model. Furthermore, the fluid force acting on a translated cylinder tends to bring it back to its initial position. This positive fluid stiffness effect does not agree with the TLP model. Implications on the flow field and resulting efforts will be further discussed.

cylinder array; axial flow; force measurements