Aerodynamics of long fibres settling in air at 10 < Re < 100

The aerodynamics of long aspect ratio nylon fibrous particles has been investigated experimentally whilst settling in air under super dilute conditions without any influence of secondary flows and at fibre Reynolds numbers of 10–100 based on fibre length. Measurement of the orientations and velocities of fibrous particles is undertaken by two-dimensional Particle Tracking Velocimetry (PTV), based on the two end-points. A statistical evaluation of fibres' mean vertical and horizontal components of settling velocities, angular velocity, orientation, number density is presented and used to assess particle aerodynamics.

Graphical abstractThe settling fibrous particles were illuminated by the laser sheet at regular intervals of time and the CCD camera used to record two images of the fibres separated by a delay of about 2.5 ms. The orientations and velocities of fibrous particles were calculated based on the two end-points. Fibre's aerodynamics is assessed by this method.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The dependences of fibre's angular velocity on volume fraction is presented ► The dependences of fibre's orientation on volume fraction is presented ► Fibre's orientation distribution is measured ► The measured dependence of settling velocity on orientation is presented