High-speed holographic measurements of fiber trajectories and orientation in near homogeneous, isotropic turbulence Technion - Israel Institute of Technology Faculty of Mechanical Engineering Asaf Cohen, Lilach Sabban, René van Hout MSc research

Introduction Multi-phase flow research is important in today's industrial manufacturing techniques and industrial/environmental processes. Particle removal Particle filter Particle separation

Research goal and methodology Lagrangian measurement of rigid fiber orientation and translation dynamics in near homogeneous isotropic air turbulence Method: Two-orthogonal view, time-resolved holographic cinematography Trajectories of nylon fibers Detailed fiber length and orientation Determination of translational and orientational dispersion coefficients

Fibers’ size characterization Fiber characterization: 0.9,1.7 and 3.3dtex nylon fibers, ρ=1.15[gr/cm 3 ] dtex [gr/10Km] is a unit of measure for the linear mass density of fibers Inverted fluorescent microscope (XDY-1) DeltaPix Invenio 2D II CCD camera: 1600x 1200 square pixels, 200X magnification 5.56μm/pix Matlab based image processing using the ‘regionprops’ function Ensemble size 200 fibers 500μm Tresholding Noise clearing Rotating to horizontal Original image taken by microscope Thresholded binary image Cleaned binary imageRotated binary image Theoretical fiber diameter

Histogram of fiber lengths dtex0.9dtex1.7dtex3.3dtex Theoretical length[mm] 0.5 Actual length[mm]0.475±0.003mm 0.501±0.003mm standard deviation[mm]

Histogram of fiber diameters dtex0.9dtex1.7dtex3.3dtex Theoretical diameter[μm] Actual diameter [μm]10.8±2.5μm15.1±2.5μm19.3±2.5μm standard deviation[μm]

Schematic of a basic Inline holography setup

Schematic of orthogonal, double view, inline digital holography high speed laser - Crystalaser, 10 10kHz 2 high speed cameras - PhotronUltimaAPX, 1024x1024 pixels, 17mm/pixel VOI 17[mm 3 ]

Hologram and reconstruction 5mm 10 data sets for each dtex. Acquisition rate: 2000[Hz],  t=0.5[ms] Kolmogorov time scale: 2.27[ms] Particle response time: 2.83[ms] time resolved 5mm Fresnel-Kirchoff integral: Depends on z

The Simple Collapse Concept

In-focus reconstructions In-focus Intensity sum method standard deviation method intensity gradient method Z

Correction and reconstructions distance Removing out of focus fibers and substituting the in focus fibers x The in focus location of the fiber in FOV2 can be accurately determined by the x coordinate in FOV1 FOV1 FOV2

preliminary results Found the 3D orientation vector of the 1.7dtex fibers determine the rotational and translational fiber dispersion coefficients needed to model fiber dispersion in turbulent flows.

Concluding remarks We have shown the feasibility of measuring the 3D orientation and translation of rigid nylon fibers in highly turbulent flows using a two-orthogonal, high speed holography system. Data processing algorithm has been developed. Future developments 3-D trajectory information allows for the determination of translational and orientational dispersion coefficients. Effect of aspect ratio Effect of Reynolds number Method can be extended to different types of non-spherical particles

Acknowledgements Israel Science Foundation: grant no. 915/10 The Edmund J. Safra Philanthropic Foundation, the Wolfson Family Charitable Trust and the Technion Fund for Promotion of Research. Dr. R. Delfos of Delft University of Technology in the Netherlands for generously supplying the nylon fibers that were used in this research. EU COST Actions MP0806 and FP1005. Questions?