On the combined flow and structural measurements via robotic volumetric PTV

Francesco M A Mitrotta,Andrea Sciacchitano,Jurij Sodja

doi:10.1088/1361-6501/ac41dd

Francesco M A Mitrotta, Andrea Sciacchitano + Show 1 more

Open Access

https://doi.org/10.1088/1361-6501/ac41dd

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Abstract

This study describes a novel measurement approach for combined flow and structural measurements in wind tunnels using robotic volumetric particle tracking velocimetry (PTV). The measurement approach is based on the application of a particle tracking algorithm on images including flow or structure tracers, where the latter are implemented by means of fiducial markers. The main steps of the measurement procedure comprise the simultaneous acquisition of flow and structure tracers in the same images, the distinction of the tracers leading to separate flow and structure image sets, the application of Lagrangian particle tracking and the further post-processing, and recombination of the obtained data. The approach is applied to the fluid-structure interaction between a flexible plate with a span of 1.2 m and a periodic gust. The total measurement volume amounts approximately to 150 liters. A phase-averaged description of the FSI problem is presented, with the focus on the effects of the spatio-temporal averaging of the flow information. The structural displacements obtained from the PTV system are validated against a scanning vibrometer. The phase-averaged displacement of the markers is also analyzed, assessing both the validity of the phase-averaged approach and the physical coherence of their motion with respect to a structural model of the plate. It is found that robotic volumetric PTV is suitable for the measurement of large-scale structural displacements, while it should not be used to measure small-scale vibrations. Finally, a visualization of the combined measurement is presented, together with an analysis of the consistency between the measured structure and flow field.

Highlights

In aeroelastic experiments, the interaction between flow and structure governs the studied phenomena
A relevant requirement for experiments involving fluid-structure interaction (FSI) is the non-intrusiveness of the measurement system, so as to ensure that the structural properties of the model, the mass distribution of the latter as well as the flow field are not altered by the measurement apparatus (Ricketts 1990)
All comparisons are performed using the particle tracking velocimetry (PTV)-helium-filled soap bubbles (HFSB) data set, considering a horizontal plane cutting the plate at half of its span at phase φ = 0 and employing a bin overlap factor of 75%

Summary

Introduction

The interaction between flow and structure governs the studied phenomena. For this reason, static and dynamic measurements of the flow field around the experimental model and of its structural response are needed. A relevant requirement for experiments involving fluid-structure interaction (FSI) is the non-intrusiveness of the measurement system, so as to ensure that the structural properties of the model, the mass distribution of the latter as well as the flow field are not altered by the measurement apparatus (Ricketts 1990). A variety of measurement devices has been used over the years in aeroelastic experiments. The awareness of the need for a proper flow characterization for the understanding of aeroelastic phenomena was already present at that time. Pressure transducers were the main tool for unsteady aerodynamic measurements, as quantitative flow visualization techniques were not yet mature enough (Ricketts 1990)

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