High-frequency simultaneous measurements of velocity and concentration within turbulent flows in wind-tunnel experiments
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RESEARCH ARTICLE
High‑frequency simultaneous measurements of velocity and concentration within turbulent flows in wind‑tunnel experiments M. Marro1 · H. Gamel1 · P. Méjean1 · H. Correia1 · L. Soulhac1 · P. Salizzoni1 Received: 13 April 2020 / Revised: 1 October 2020 / Accepted: 12 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We analyse the metrological aspect related to systems devoted to the simultaneous measurements of (one point) velocity and scalar concentration statistics. We consider systems based on the coupling of an anemometer (laser Doppler or hot wire) with a flame ionization detector. In particular, we focus on the estimate of the cross-correlation velocity-concentration. Key aspects in the reliability of such measurements are related to the identification of an optimal distance between the two probes, the time lag with which the velocity and concentration signals are acquired, and, eventually, the influence of seeding particles (when using a laser Doppler anemometer) on the concentration measurements. We investigate these aspects by performing wind-tunnel experiments on the scalar dispersion downwind a ground-level source in a turbulent boundary layer. This analysis allowed us to identify a time delay and a convenient distance between the signals provided by the anemometer and the concentration detector. Results also show that the seeding used for the laser Doppler anemometer measurements modifies the cut-off frequency in the concentration spectra and induces a slightly larger uncertainty on the statistics of scalar field. The results show the reliability of both systems in estimating (horizontal and vertical) turbulent mass fluxes.
* M. Marro marro.massimo@ec‑lyon.fr P. Salizzoni pietro.salizzoni@ec‑lyon.fr 1
Laboratoire de Mécanique des Fluides et d’Acoustique, University of Lyon, CNRS UMR 5509, Ecole Centrale de Lyon, INSA Lyon, Université Claude Bernard, 36, Avenue Guy de Collongue, 69134 Ecully, France
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245
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Experiments in Fluids
(2020) 61:245
Graphic abstract
1 Introduction The experimental estimate of joint velocity-concentration statistics is a key issue for the study of the dispersion and mixing of scalar within a turbulent flow. This requires simultaneous measurements of the flow velocity and the scalar field, which generally imply to couple two separate acquisition systems. The use of particle image velocimetry (PIV) combined to other optical techniques for the concentration measurements is well suited in water flume experiments (e.g., Liao and Cowen 2002). Its use in wind-tunnel tests, however (Vinçont et al. 2000), still presents main shortcomings, mainly concerning the control of the seeding particles emitted by the source (which explains the relatively low number of study published so far adopting these techniques). The most reliable and robust techniques rely so far in the adoption of different metrological approaches for the measurements of combined one-point statistics. In the study of scalar di
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