Abstract
A method to identify the surface of solid models immersed in fluid flows is devised that examines the spatial distribution of flow tracers. The fluid–solid interface is associated with the distance from the center of a circle to the centroid of the tracers ensemble captured within it. The theoretical foundation of the method is presented for 2D planar interfaces in the limit of a continuous tracer distribution. The discrete regime is analyzed, yielding the uncertainty of this estimator. Also the errors resulting from curved interfaces are discussed. The method's working principle is illustrated using synthetic data of a 2D cambered airfoil, showing that one of the limitations is the treatment of an object thinner than the search circle diameter. The method is readily adapted to 3D and applied to the 3D PTV data of the flow around a juncture. The surface is reconstructed within the expected uncertainty, and specific limitations, such as the smoothing of sharp edges is observed.Graphic abstract
Highlights
Flow field measurements based on particle imaging tech‐ niques (Adrian and Westerweel 2011; Raffel et al 2018) have advanced in the last decades in terms of spatiotempo‐ ral resolution and velocity measurement range matching the requirements of complex flows as encountered for industrial applications (Schanz et al 2016; Discetti and Coletti 2018; Michaux et al 2018, among others)
Experiments are conducted by Robotic volumetric particle image velocimetry (PIV) (Jux et al 2018), in which particle images are acquired by a coaxial volumetric velocimeter (CVV, Schneiders et al 2018). 10,000 image quadruples of 640 × 452 p x2 are recorded at a rate of 858 Hz
The analysis is solely based on the spatial distribution of particle tracers in the fluid domain, assuming the interface between the seeded fluid flow and the void solid region is a valid representation of the object silhouette
Summary
Flow field measurements based on particle imaging tech‐ niques (Adrian and Westerweel 2011; Raffel et al 2018) have advanced in the last decades in terms of spatiotempo‐ ral resolution and velocity measurement range matching the requirements of complex flows as encountered for industrial applications (Schanz et al 2016; Discetti and Coletti 2018; Michaux et al 2018, among others). Oftentimes, for aerody‐ namics studies, the attention is focused on the flow around an object immersed in a fluid stream. The velocimetry data are exploited to study the near-surface flow properties, such as pressure or even skin friction (Depardon et al 2005; Ragni et al 2009; Auteri et al 2015; Jux et al 2020, among others). For the latter task, accurate determina‐ tion of the object surface position and orientation is deemed essential. The prob‐ lem of object surface determination for applications in fluid flow investigations has only been studied in few works and problem-specific solutions have been proposed
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