‘Postage-stamp PIV’: small velocity fields at 400 kHz for turbulence spectra measurements

Abstract

Time-resolved particle image velocimetry recently has been demonstrated in high-speed flows using a pulse-burst laser at repetition rates reaching 50 kHz. Turbulent behavior can be measured at still higher frequencies if the field of view is greatly reduced and lower laser pulse energy is accepted. Current technology allows image acquisition at 400 kHz for sequences exceeding 4000 frames but for an array of only 128 × 120 pixels, giving the moniker of ‘postage-stamp PIV’. The technique has been tested far downstream of a supersonic jet exhausting into a transonic crossflow. Two-component measurements appear valid until 120 kHz, at which point a noise floor emerges whose magnitude is dependent on the reduction of peak locking. Stereoscopic measurement offers three-component data for turbulent kinetic energy spectra, but exhibits a reduced signal bandwidth and higher noise in the out-of-plane component due to the oblique camera images. The resulting spectra reveal two regions exhibiting power-law dependence describing the turbulent decay. The frequency response of the present measurement configuration exceeds nearly all previous velocimetry measurements in high speed flow.

Hybrid time series from PIV for characterization of turbulent flow fields: ASTRA -- Approach using Spatially and Temporally Resolved Advection

“…For this reason, the effect of a lower temporal resolution will be investigated. The recorded data set is artificially sampled down by using just every [1,3,5]th velocity field. By reducing the sampling frequency, the displacement of the structures D (see Eqn.…”

“…Only in exceptional cases it is possible to achieve significantly higher sampling rates. An example is the so-called postage stamp PIV with frame rates as high as 400kHz [3]. However, this can only be done for a handful of images and very small field of view (FOV).…”

The flow around a surface mounted cube: a characterization by time-resolved PIV, 3D Shake-The-Box and LBM simulation

“…The 3D STB and (with limitations) the TR-PIV techniques, in principle, can be adapted to flows with much higher Reynolds numbers and flow conditions that currently are beyond to reach of DNS. The employed measurement techniques are capable of very high dynamic temporal and spatial range, at least for onepoint statistics of the velocity vector data in small fields of view (Beresh et al 2018) or by multi-pulse STB (Novara et al 2016(Novara et al , 2019. For example, in compressible and swept wing aerodynamics there is continued research interest in the laminar-transitional flow conditions when the surface mounted obstacle heights H are significantly smaller than the BL thicknesses, thus mimicking surface imperfections and roughness caused by limitations in manufacturing capabilities in aerodynamic vehicle production.…”

12th International Symposium on Particle Image Velocimetry (PIV 2017)

“…The most recent installation of this meeting, the 12th International Symposium on Particle Image Velocimetry (PIV 2017), was held in Busan, Korea on 18-22 June 2017. This special feature of Measurement Science and Technology contains six papers that were selected from PIV 2017 that focus on new advancements of PIV measurements and analysis techniques.The paper by Beresh et al [1] introduces high-speed time-resolved PIV using a pulseburst laser at repetition rates reaching 50 kHz. The technology allows image acquisition at 400 kHz for sequences exceeding 4000 frames but for an array of only 128 × 120 pixels, giving the moniker of 'postage-stamp PIV'.…”

“…The paper by Beresh et al [1] introduces high-speed time-resolved PIV using a pulseburst laser at repetition rates reaching 50 kHz. The technology allows image acquisition at 400 kHz for sequences exceeding 4000 frames but for an array of only 128 × 120 pixels, giving the moniker of 'postage-stamp PIV'.…”