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Role of secondary shear-layer vortices in the development of flow asymmetry on a cone–cylinder body at high angles of incidence.

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Bibliographic Details
Title: Role of secondary shear-layer vortices in the development of flow asymmetry on a cone–cylinder body at high angles of incidence.
Authors: Kumar, Roopesh1, Guha, Tufan Kumar1, Kumar, Rajan1 rkumar@fsu.edu
Source: Experiments in Fluids. Oct2020, Vol. 61 Issue 10, pN.PAG-N.PAG. 1p.
Subjects: Flow velocity, Particle image velocimetry, Hydraulic cylinders, Flow visualization, Spheromaks
Abstract: Vortex asymmetry develops on slender bodies at high angles of incidence, leading to large side-forces and yaw moments even in symmetrical flight conditions. In the present experimental study, the flow over a slender body consisting of a conical forebody and a cylindrical aftbody is studied at high angles of incidence at low speeds. Experiments consisted of force measurements using a six-component strain gauge balance and velocity field using Particle Image Velocimetry. Results show that a pair of counter-rotating vortices develop nearly symmetrically over a polished cone but become asymmetric over the cylinder. Several secondary shear-layer vortices develop at the cone–cylinder junction and over the cylinder due to sharp turning angle, surface imperfections, and joints. These secondary shear-layer vortices then merge with the primary vortex pair, leading to the flow asymmetry. The flow characteristics and side-forces vary significantly when the conical forebody is rotated about its axis of symmetry and set to different azimuthal positions. The results strongly suggest that a change in the geometry at the cone–cylinder junction and surface imperfections present on the cylindrical aftbody play an important role in determining the overall flow-asymmetry and the magnitude of side-forces generated on the slender body at high angles of incidence. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Vortex asymmetry develops on slender bodies at high angles of incidence, leading to large side-forces and yaw moments even in symmetrical flight conditions. In the present experimental study, the flow over a slender body consisting of a conical forebody and a cylindrical aftbody is studied at high angles of incidence at low speeds. Experiments consisted of force measurements using a six-component strain gauge balance and velocity field using Particle Image Velocimetry. Results show that a pair of counter-rotating vortices develop nearly symmetrically over a polished cone but become asymmetric over the cylinder. Several secondary shear-layer vortices develop at the cone–cylinder junction and over the cylinder due to sharp turning angle, surface imperfections, and joints. These secondary shear-layer vortices then merge with the primary vortex pair, leading to the flow asymmetry. The flow characteristics and side-forces vary significantly when the conical forebody is rotated about its axis of symmetry and set to different azimuthal positions. The results strongly suggest that a change in the geometry at the cone–cylinder junction and surface imperfections present on the cylindrical aftbody play an important role in determining the overall flow-asymmetry and the magnitude of side-forces generated on the slender body at high angles of incidence. [ABSTRACT FROM AUTHOR]
ISSN:07234864
DOI:10.1007/s00348-020-03045-y