Development of an Optical set-up for 3D PIV with a Large Volume

Abitan, Haim; Velta, Clara Marika; Zhang, Yisheng; Ribergård, Simon L.; Nielsen, Jakob Skov

doi:10.18409/ispiv.v1i1.138

Cited by 2 publications

(4 citation statements)

References 5 publications

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“…Therefore we can treat the output of the LED as of a single wavelength. The signal current i s on a pixel in a CMOS detector in volumetric PTV experiment (with a Laser) was found (Abitan et al, 2022) to depend on the pulse energy of a laser E p and other parameters according to:…”

Section: Estimation Of the Image Signal In Volumetric Ptv With An Ledmentioning

confidence: 99%

“…Such high-power 532 nm lasers are not simple to build and are expensive and complicated to develop. Further more, a detailed model (Abitan et al, 2022) that was developed for estimation of the required pulse energy in volumetric PTV experiments taught us that in order to image particles at the far edge of the depth of field, one would need to increase the pulse energy and average power of the laser by a meaningful factor (between 2-4, depending on the acceptable circle of confusion of the imaged particle).…”

Section: Introductionmentioning

confidence: 99%

“…The reduced working distance and increased aperture diameter reduced the required pulse energy to 17.5 mJ and the average power to 70 W . In tandem, we explored fast scanning and multi reflections techniques (Abitan et al, 2021) where one use the laser beam repeatedly and thus increase the efficiency of the illuminating source. Here, we report on the development of a pulsed and collimated high-power 460 nm Gallium Nitride LED unit for illuminating large volumes for PTV measurements.…”

Section: Introductionmentioning

confidence: 99%

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Optical and Electrical Considerations for Developing Pulsed High-Power LED for Volumetric Particle Tracking Velocimetry

Abitan,

Edelsten,

Zhang

et al. 2022

LXLASER

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Volumetric Particle Tracking Velocimetry (PTV) in volumes larger than 103 cm3 with 15 μm Air Filled Soap Bubbles (AFSB) requires a powerful pulsed laser source of few tenth of mJ pulse energy, depending on the optical arrangement of the experiment. Initial experiments in our lab with 15 μm AFSB and 1 mJ pulse energy from a 532 nm laser source showed that in order to image turbulence flow phenomena in volumes about 4x10^3 cm^3 at 1 m working distance and an f-number of 8, one would need a laser source with about 315 mJ pulse energy and 1260 W average power at 4 kHz repetition rate. Such high-power 532 nm lasers are not simple to build and are expensive and complicated to develop. By reducing the working distance and increasing the diameter of the camera aperture, the required laser power was reduced by a factor 18 to 17.5 mJ pulse energy and 70 W average power, which is still a very high power laser. As a possible alternative, we report here on the development of a collimated beam, high-power, pulsed 460 nm LED for volumetric PTV measurements of turbulence flow in a large volume seeded with AFSB p articles. We report of the optical and electrical consideration that are required in development of such an LED source. First, we combined a practical model for the output power of an LED with a model that estimates the signal level on a CMOS detector in a volumetric PTV experiment with AFSB particles. It predicted that our LED should be driven by 277 A in order to generate 1 mJ of optical pulse energy with 20 μs pulse duration. In order to avoid power drooping at high currents density in the LED, we chose an architecture of LEDs array where each LED unit of the array operates at 20 μs pulse duration, 4 kHz repetition rate and with peak current of 200 A. Each such LED will deliver 0.72 mJ pulse energy and 24 such LED units will supply the required optical density. Second, we report of the optical and electrical features of the collimated , high-power, pulsed 460 nm LED unit we built. We tested the LED in a PTV experiment where the LED operated with 0.72 mJ pulse energy, 1 kHz repetition rate and 20 A peak current. The measured signal current from a CMOS-pixel due to Mie scattering AFSB particles was in good agreement with the predicated signal level.

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Section: Estimation Of the Image Signal In Volumetric Ptv With An Ledmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical and Electrical Considerations for Developing Pulsed High-Power LED for Volumetric Particle Tracking Velocimetry

Abitan,

Edelsten,

Zhang

et al. 2022

LXLASER

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show abstract

“…The laboratory consists of two main setups; one to quantify the degree of non-equilibrium and one to measure and analyze the true underlying processes, to be described in coming work e.g. [28,29,30,31]. This will allow us to directly test e.g.…”

Section: Establishing a New Laboratory And Developing A Theoretical F...mentioning

confidence: 99%

Dynamic Triad Interactions and Non-equilibrium Turbulence

Velte

Buchhave²

2021

Springer Proceedings in Physics

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The classical K41 theory, based on the ideas of Kolmogorov, Richardson and Batchelor, has in recent years with accumulating evidence become subject to increased scrutiny. We elaborate on the idea that the deficiencies of the theory originate in the fundamental assumption of universal equilibrium, which in turn is the result of the basic assumption of locality of nonlinear interactions. These very fundamental assumptions are argued to have no anchoring in the governing Navier-Stokes equation. The possibility for other kinds of solutions are discussed from a historical perspective. K41 is also identified to represent an equilibrium solution that cannot predict non-equilibrium turbulence. Why the need for new perspectives on the established theory?The theoretical framework developed by Kolmogorov (including the contributing ideas of Richardson and Batchelor, often collectively referred to as the 'K41' theory [1, 2, 3]), has comprised the cornerstone of our understanding of turbulence for more than half a century. It has up until recently not been so frequently acknowledged that Kolmogorov's ideas were initially heavily questioned. In fact, it took two decades before K41 was convincingly supported by experiments; first in a turbulent round jet by Gibson [4] and secondly (and more widely acknowledged) by Grant, Stewart and Moilliet [5]. Once these empirical studies supporting K41 finally appeared, the theory has been amply supported by further experiments and simulations in some flows, while other theories have been more successful in predicting non-K41 types of flows (c.f.

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Development of an Optical set-up for 3D PIV with a Large Volume

Cited by 2 publications

References 5 publications

Optical and Electrical Considerations for Developing Pulsed High-Power LED for Volumetric Particle Tracking Velocimetry

Optical and Electrical Considerations for Developing Pulsed High-Power LED for Volumetric Particle Tracking Velocimetry

Dynamic Triad Interactions and Non-equilibrium Turbulence

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