אנו מודים Susantha Wijesinghe אשר תוכנן ונבנה מערכת דחיסת תמונה אנו משתמשים. אנו מכירים תמיכה מן DMR-1208990 להעניק NSF.

<ol>
	<li>Marcus, G., Parsa, S., Kramel, S., Ni, R., Voth, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+the+Solid-body+Rotation+of+Anisotropic+Particles+in+3D+Turbulence.">Measurements of the Solid-body Rotation of Anisotropic Particles in 3D Turbulence.</a> New J. Phys. 16, 102001 (2014).</li><li>Bretherton, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+motion+of+rigid+particles+in+a+shear+flow+at+low+Reynolds+number.">The motion of rigid particles in a shear flow at low Reynolds number.</a> J. Fluid Mech. 14 (02), 284-304 (1962).</li><li>Oullette, N., Xu, H., Bodenschatz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+study+of+three-dimensional+Lagrangian+particle+tracking+algorithms.">A quantitative study of three-dimensional Lagrangian particle tracking algorithms.</a> Exp. in Fluids. 40 (2), 301-313 (2006).</li><li>Parsa, S., Calzavarini, E., Toschi, F., Voth, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rotation+Rate+of+Rods+in+Turbulent+Fluid.">Rotation Rate of Rods in Turbulent Fluid.</a> Phys. Rev. Lett. 109 (13), 134501 (2012).</li><li>Parsa, S., Voth, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inertial+Range+Scaling+in+Rotations+of+Long+Rods+in+Turbulence.">Inertial Range Scaling in Rotations of Long Rods in Turbulence.</a> Phys. Rev. Lett. 112 (2), 024501 (2014).</li><li>Tsai, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+versatile+camera+calibration+technique+for+high-accuracy+3d+machine+vision+metrology+using+off-the-shelf+tv+cameras+and+lenses.">A versatile camera calibration technique for high-accuracy 3d machine vision metrology using off-the-shelf tv cameras and lenses.</a> IEEE Journal of Robotics and Automation. 3 (4), 323-344 (1987).</li><li>Blum, D., Kunwar, S., Johnson, J., Voth, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+nonuniversal+large+scales+on+conditional+structure+functions+in+turbulence.">Effects of nonuniversal large scales on conditional structure functions in turbulence.</a> Phys. Fluids. 22 (1), 015107 (2010).</li><li>Mann, J., Ott, S., Andersen, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+study+of+relative,+turbulent+diffusion.">Experimental study of relative, turbulent diffusion.</a> RISO Internal Report. , (1999).</li><li>Chan, K., Stich, D., Voth, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+image+compression+for+high-speed+particle+tracking.">Real-time image compression for high-speed particle tracking.</a> Rev. Sci. Instrum. 78 (2), 023704 (2007).</li><li>Goldstein, H., Poole, C., Safko, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Classical Mechanics, 3rd Edition. , 134-180 (2002).</li><li>Parsa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Rotational dynamics of rod particles in fluid flows. , (2013).</li><li>Wijesinghe, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Measurement of the effects of large scale anisotropy on the small scales of turbulence. , (2012).</li><li>Wallace, J., Foss, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Measurement+of+Vorticity+in+Turbulent+Flows.">The Measurement of Vorticity in Turbulent Flows.</a> Annu. Rev. Fluid Mech. 27, 469-514 (1995).</li><li>Su, L., Dahm, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scalar+imaging+velocimetry+measurements+of+the+velocity+gradient+tensor+field+in+turbulent+flows.+I.+Assessment+of+errors.">Scalar imaging velocimetry measurements of the velocity gradient tensor field in turbulent flows. I. Assessment of errors.</a> Phys. Fluids. 8, 1869-1882 (1996).</li><li>L&#252;thi, B., Tsinober, A., Kinzelbach, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lagrangian+measurement+of+vorticity+dynamics+in+turbulent+flow.">Lagrangian measurement of vorticity dynamics in turbulent flow.</a> J. Fluid Mech. 528, 87-118 (2005).</li><li>Frish, M., Webb, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+measurement+of+vorticity+by+optical+probe.">Direct measurement of vorticity by optical probe.</a> J. Fluid Mech. 107, 173-200 (1981).</li><li>Zimmerman, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracking+the+dynamics+of+translation+and+absolute+orientation+of+a+sphere+in+a+turbulent+flow.">Tracking the dynamics of translation and absolute orientation of a sphere in a turbulent flow.</a> Rev. Sci. Instrum. 82 (3), 033906 (2011).</li><li>Zimmerman, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rotational+Intermittency+and+Turbulence+Induced+Lift+Experienced+by+Large+Particles+in+a+Turbulent+Flow.">Rotational Intermittency and Turbulence Induced Lift Experienced by Large Particles in a Turbulent Flow.</a> Phys. Rev. Lett. 106 (15), 154501 (2011).</li><li>Klein, S., Gibert, M. a. t. h. i. e. u., B&#233;rut, A., Bodenschatz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+3D+measurement+of+the+translation+and+rotation+of+finite-size+particles+and+the+flow+field+in+a+fully+developed+turbulent+water+flow.">Simultaneous 3D measurement of the translation and rotation of finite-size particles and the flow field in a fully developed turbulent water flow.</a> Meas. Sci. Technol. 24 (2), 1-10 (2013).</li><li>Bellani, G., Byron, M., Collignon, A., Meyer, C., Variano, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shape+effects+on+turbulent+modulation+by+large+nearly+neutrally+buoyant+particles.">Shape effects on turbulent modulation by large nearly neutrally buoyant particles.</a> J. Fluid Mech. 712, 41-60 (2012).</li></ol>

אין המחברים אינטרסים כלכליים מתחרים לחשוף.

מדידות של ערבוליות והסיבוב של חלקיקי זרימת נוזל סוער ארוכות הוכרו מטרות חשובות מכניקת זורמים ניסיונית. הסיבוב מוצק הגוף של כדורים הקטנים ב מערבולת הוא השווה למחצית ערבוליות הנוזלת, אבל הסימטריה הסיבובית של תחומים הפכה מדידה ישירה של הסיבוב מוצק הגוף שלהם קשה. באופן ...

בפרסומים העדכניים, הצגנו את השימוש של חלקיקים עשויים זרועותיה דקות מרובות למדידת תנועה סיבובית של חלקיקי מערבולת 1. חלקיקים אלה יכולים להיות מפוברק באמצעות מדפסות 3D, ויתכן נמדדים מצבה, האוריינטציה שלהם במדויק, וקצב הסיבוב באמצעות מספר מצלמות. שימוש בכלים מתורת גוף רזה, ניתן להראות כי חלקיקים אלה המקביל 2 ellipsoids היעיל, ואת התנועות הסיבוביות של חלקיקים אלה זהות לאלה של ellipsoids היעיל שלהם. חלקיקים בזרועות סימטריות שווה באורכם לסובב כמו כדורים. חלקיק אחד כזה הוא שקע, שבו יש שלוש זרועות ניצבים הדדיים המצורפות במרכזה. התאמת האורכים היחסיים של זרועות שקע יכולה להקים מקבילת חלקיקים לכל אליפסואיד תלת-צירי. אם אורך זרוע אחת מוגדר שווה לאפס, זה יוצר צלב, אשר אליפסואיד המקביל הוא דיסק. חלקיקים עשויים דקנשק תופס חלק קטן המנפח המוצק של עמיתיהם אליפסואידי המוצקים שלהם. כתוצאה מכך, הם משקעים לאט יותר, מה שהופכים אותם קלים יותר התאמת צפיפות. זה מאפשר הלימוד של חלקיקים הרבה יותר גדולים מאשר הוא נוח עם חלקיקים אליפסואידי מוצקים. בנוסף, ניתן לבצע הדמיה בריכוזי חלקיקים גבוהים משמעותי, שכן החלקיקים לחסום חלק קטן של האור מחלקיקים אחרים. במאמר זה, שיטות ייצור ומעקב של חלקיקים מודפסים 3D מתועדים. כלים למעקב אחרים תנועת translational של חלקיקים כדוריים מעמדות חלקיקים כפי שניתן לראות על ידי מספר רב של מצלמות פותחו על ידי מספר קבוצות 3,4. הפרסה et al. 5 מורחבת בגישה זו כדי לעקוב אחר מוטה באמצעות המיקום והכיוון של המוטות לראות מספר מצלמות. כאן, אנו מציגים שיטות בודה חלקיקים של מגוון רחב של צורות בשחזור אוריינטציות 3D שלהם. זה מציע האפשרות דואר להאריך מעקב 3D של חלקיקים עם צורות מורכבות למגוון רחב של יישומים חדשים. יש טכניקה זו יש פוטנציאל גדול להמשך פיתוח בגלל המגוון הרחב של צורות חלקיקים שניתן תוכנן. יש רבים מן הצורות יישומים ישירים בתזרים הסביבה, שבו פלנקטון, זרעים, גבישי קרח מגיעים במגוון עצום של צורות. חיבורים בין סיבובי חלקיקים ומאפיינים בקנה מידה קטנה יסוד של זרימה טורבולנטית 6 מראים כי מחקר של סיבובים של חלקיקים אלה מספק דרכים חדשות להסתכל על תהליך המפל הסוער.

<table><tbody><tr><td>Condor Nd:YAG 50 W laser</td><td>Quantronics</td><td>532-30-M</td><td></td></tr><tr><td>High speed camera</td><td>Basler</td><td>A504k</td><td></td></tr><tr><td>High speed camera</td><td>Mikrotron</td><td>EoSens Mc1362</td><td></td></tr><tr><td>Rhodamine-B</td><td>ScienceLab.com</td><td>SLR1465</td><td></td></tr><tr><td>Sodium Hydroxide</td><td>Macron</td><td>7708</td><td>Pellets.</td></tr><tr><td>500 Connex 3D printer</td><td>Objet</td><td></td><td>Used to make smaller particles. Particles ordered from RP+M (rapid prototyping plus manufacturing).</td></tr><tr><td>VeroClear</td><td>Stratasys</td><td>RGD810</td><td>Objet build material.</td></tr><tr><td>Clear Form 1 Photopolymer Resin</td><td>Formlabs</td><td></td><td></td></tr><tr><td>Cylindrical and spherical lenses</td><td></td><td></td><td></td></tr><tr><td>200 mm macro camera lenses</td><td></td><td></td><td>F-mount.</td></tr><tr><td>Ultrasonic bath</td><td>Sonicator</td><td></td><td></td></tr><tr><td>Calcium Chloride</td><td>Spectrum Chemical Mfg. Corp.</td><td>CAS 10043-52-2</td><td>Pellets.</td></tr><tr><td>LabVIEW System Design Software</td><td>National Instruments</td><td></td><td>Used to trigger cameras, control grid, and trigger laser.</td></tr><tr><td>XCAP Software</td><td>EPIX</td><td></td><td>Used with LabVIEW to trigger cameras.</td></tr><tr><td>MATLAB</td><td>Mathworks</td><td></td><td>Used for all image and data analysis. Programs for extracting 3D orientations from multiple images are included with this publication.</td></tr><tr><td>OpenPTV: Open Source Particle Tracking Velocimetry</td><td>OpenPTV Consortium</td><td></td><td></td></tr><tr><td>ParaView</td><td>Kitware</td><td></td><td></td></tr><tr><td>AutoCAD</td><td>AutoDesk</td><td></td><td>Used to design all particles. Screenshots of particle designs are all of AutoCAD.</td></tr><tr><td>Mesh with 0.040 x 0.053 inch holes</td><td>Industrial Netting</td><td>XN5170&amp;ndash;43.5</td><td></td></tr><tr><td>Camera filters</td><td>Schneider Optics</td><td>B+W 040M</td><td></td></tr></tbody></table>

methods for measuring the orientation and rotation rate of 3d-printed particles in turbulence

שיטות ניסיוניות מוצגות למדידת התנועה הסיבובית ו translational של חלקיקי איזוטרופי ב זורם נוזל סוער. טכנולוגיית הדפסת 3D משמשת לפברק חלקיקים בזרועות רזות מחוברות במרכז משותף. צורות בחנו הן צלבים (שתי מוטות מאונכות), שקעים (שלוש מוטות מאונכות), שלשות (שלוש מוטות בסימטריה מישוריים משולשת), ו tetrads (ארבע זרועות בסימטרית tetrahedral). שיטות להפקה בסדר גודל של 10,000 חלקיקים צבועים fluorescently מתוארות. מדידות זמן נפתר האורינטציה שלהם וקצב סיבוב מוצק גוף מתקבלות ארבעה סרטוני מסונכרנים של התנועה שלהם זרימה טורבולנטית בין נדנוד רשתות עם R λ = 91. בשגרת מספר יחסית נמוכה ריינולדס זה, חלקיקי advected הם קטנים מספיק כי הם משוערים חלקיקים נותבו אליפסואידי. אנו מציגים תוצאות של מסלולי 3D זמן נפתר של מיקום וכיוון של החלקיקים כמוגם מדידות של שיעורי הסיבוב שלהם.

איור 3 א מציג תמונה של הטטרדה מאחד המצלמות שלנו מעל מגרש של זוויות אוילר המתקבלת קטע מסלולו (איור 3c). 3 ב איור, התוצאות של האלגוריתם למציאת-אוריינטציה, המתואר בפרוטוקול 5 - 5.3, הן על גבי התמונה הטטרדה. הזרועות של הטטרדה באי...

Watch this Scientific Journal Video about Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence at JoVE.com

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

שיטות למדידת התמצאות סיבוב שעיר 3D מודפסות חלקיקי Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

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3-Dimensional Kinetics of a Rigid Body

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Dynamics of Rotational Motions

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10.0K Views.  Wesleyan University. We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

Video: Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Encapsulation and Permeability Characteristics of Plasma Polymerized Hollow Particles

In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma polymerization of isopropanol on various solid substrates, including silica and potassium chloride. This versatile technique is used to treat nanoparticles and nanopowders with sizes ranging from 37 nm to 1 micron, by depositing films whose thickness can be anywhere from 1 nm to upwards of 100 nm. Dissolution of the core allows us to study the rate of permeation through the film. In these experiments, we determine the diffusion coefficient of KCl through the barrier film by coating KCL nanocrystals and subsequently monitoring the ionic conductivity of the coated particles suspended in water. The primary interest in this process is the encapsulation and delayed release of solutes. The thickness of the shell is one of the independent variables by which we control the rate of release. It has a strong effect on the rate of release, which increases from a six-hour release (shell thickness is 20 nm) to a long-term release over 30 days (shell thickness is 95 nm). The release profile shows a characteristic behavior: a fast release (35% of the final materials) during the first five minutes after the beginning of the dissolution, and a slower release till all of the core materials come out.

We have used plasma enhanced chemical vapor deposition to deposit thin films ranging from a few nm to several 100 nm on nano-sized particles of various materials. We subsequently etch the core material to produce hollow nanoshells whose permeability is controlled by the thickness of the shell. We characterize the permeability of these coatings to small solutes and demonstrate that these barriers can provide sustained release of the core material over several days.

אנקפסולציה וחדירות מאפיינים של חלקיקים פלזמה polymerized הולו

In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma ...

Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids&#160;and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data.
The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.1&#160;Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.

This paper demonstrates the experimental procedure to measure terminal settling velocities of spherical particles in surfactant-based shear thinning viscoelastic fluids. Fluids over a wide range of rheological properties are prepared and settling velocities are measured for a range of particle sizes in unbounded fluids and fluids between parallel walls.

מדידה ניסיונית של מהירות יישוב של חלקיקים כדוריים בנוזלים ויסקואלסטיים לא מכופתרים ומרותקים על בסיס חומרים פעילי שטח

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

אוטומציה של מצב נעילה בתוך לייזר סיב סיבוב קוי קיטוב באמצעות מדידות קיטוב פלט

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

תלת ממד חלקיקי מעקב velocimetry עבור יישומי Turbulence: מקרה של Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to turbulent flow conditions are presented. For that purpose, the incipient motion of a single bead is studied on regular substrates that consist of a monolayer of fixed spheres of uniform size that are regularly arranged in triangular and quadratic symmetries. The threshold is characterized by the critical Shields number. The criterion for the onset of motion is defined as the displacement from the original equilibrium position to the neighboring one. The displacement and the mode of motion are identified with an imaging system. The laminar flow is induced using a rotational rheometer with a parallel disk configuration. The shear Reynolds number remains below 1. The turbulent flow is induced in a low-speed wind tunnel with open jet test section. The air velocity is regulated with a frequency converter on the blower fan. The velocity profile is measured with a hot wire probe connected to a hot film anemometer. The shear Reynolds number ranges between 40 and 150. The logarithmic velocity law and the modified wall law presented by Rotta are used to infer the shear velocity from the experimental data. The latter is of special interest when the mobile bead is partially exposed to the turbulent flow in the so-called hydraulically transitional flow regime. The shear stress is estimated at onset of motion. Some illustrative results showing the strong impact of the angle of repose, and the exposure of the bead to shear flow are represented in both regimes.

Two different methods for characterizing the incipient particle motion of a single bead as a function of the sediment bed geometry from laminar to turbulent flow are presented.

באופן חזותי המבוסס על אפיון חלקיק התחלתית של סובסטרטים רגיל: מלמינריות לתנאים הסוערת

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to ...

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine micro-organisms, and/or sediments in the ocean, or fluidized bed reactors and combustion processes in engineered systems. In order to study the effect of turbulence on the kinematics of particles in such flows, simultaneous measurements of both the flow and particle kinematics are required. Non-intrusive, optical flow measurement techniques for measuring turbulence, or for tracking particles, exist but measuring both simultaneously can be challenging due to interference between the techniques. The method presented herein provides a low cost and relatively simple method to make simultaneous measurements of the flow and particle kinematics. A cross section of the flow is measured using a particle image velocimetry (PIV) technique, which provides two components of velocity in the measurement plane. This technique utilizes a pulsed-laser for illumination of the seeded flow field that is imaged by a digital camera. The particle kinematics are simultaneously imaged using a light emitting diode (LED) line light that illuminates a planar cross section of the flow that overlaps with the PIV field-of-view (FOV). The line light is of low enough power that it does not affect the PIV measurements, but powerful enough to illuminate the larger particles of interest imaged using the high-speed camera. High-speed images that contain the laser pulses from the PIV technique are easily filtered by examining the summed intensity level of each high-speed image. By making the frame rate of the high-speed camera incommensurate with that of the PIV camera frame rate, the number of contaminated frames in the high-speed time series can be minimized. The technique is suitable for mean flows that are predominantly two-dimensional, contain particles that are at least 5 times the mean diameter of the PIV seeding tracers, and are low in concentration.

The technique described herein offers a low cost and relatively simple method to simultaneously measure particle kinematics and turbulence in flows with low particle concentrations. The turbulence is measured using particle image velocimetry (PIV), and particle kinematics are calculated from images obtained with a high-speed camera in an overlapping field-of-view.

מדידה סימולטני של מערבולת, קינמטיקה של חלקיקים באמצעות זרימת טכניקות הדמיה

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine ...

3D Printing - Evaluating Particle Emissions of a 3D Printing Pen

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament fabrication (FFF) is an inexpensive method used most frequently by consumers. Studies with 3D printers have shown that during the printing process particulate and volatile substances are released. Handheld 3D printing pens also use the FFF method but the consumer&#8217;s proximity to the 3D pens gives reason to higher exposure compared to a 3D printer. At the same time, 3D printing pens are often marketed for children who could be more sensitive to the printing emission. The aim of this study was to implement a low cost method to analyze the emissions of 3D printing pens. Polylactide (PLA) and acrylonitrile butadiene styrene (ABS) filaments of different colors were tested. In addition, filaments containing metal and carbon nanotubes (CNTs) were analyzed. An 18.5 L chamber and sampling close to the emission source was used to characterize emissions and concentrations near the breathing zone of the user.
Particle emissions and particle size distributions were measured and the potential release of metal particles and CNTs investigated. Particle number concentrations were found in a range of 105 - 106 particles/cm3, which is comparable to previous reports from 3D printers. Transmission electron microscopy (TEM) analysis showed nanoparticles of the different thermoplastic materials as well as of metal particles and CNTs. High contents of metal were observed by inductively coupled plasma mass spectrometry (ICP-MS).
These results call for a cautious use of 3D pens due to potential risk to the consumers.

This protocol presents a method to analyze the emission of 3D printing pens. Particle concentration and particle size distribution of the released particle is measured. Released particles are further analyzed with transmission electron microscopy (TEM). Metal content in filaments is quantified by inductively coupled plasma mass spectrometry (ICP-MS).

הדפסה בתלת-ממד - הערכת פליטות חלקיקים של עט הדפסה בתלת-ממד

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament ...

Frugal Imaging Technique of Capillary Flow Through Three-Dimensional Polymeric Printing Powders

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in microfluidic and millifluidic studies. With the advent of three-dimensional (3D) printing, a new domain of materials has emerged, thereby increasing the demand for novel polymers. Specifically, polymeric powders, with average particle sizes on the order of a micron, are experiencing a growing interest from academic and industrial communities. Controlling material tunability at the mesoscopic to microscopic length scales creates opportunities to develop innovative materials, such as gradient materials. Recently, a need for micron-sized polymeric powders has been growing, as clear applications for the material are developing. Three-dimensional printing provides a high-throughput process with a direct link to new applications, driving investigations into the physio-chemical and transport interactions on a mesoscale. The protocol that is discussed in this article provides a non-invasive technique to image fluid flow in packed powder beds, providing high temporal and spatial resolution while leveraging mobile technology that is readily available from mobile devices, such as smartphones. By utilizing a common mobile device, the imaging costs that would normally be associated with an optical microscope are eliminated, resulting in a frugal-science approach. The proposed protocol has successfully characterized a variety of combinations of fluids and powders, creating a diagnostic platform for quickly imaging and identifying an optimal combination of fluid and powder.

The proposed technique will provide a novel, efficient, frugal, and non-invasive approach for imaging fluidic flow through a packed powder bed, yielding high spatial and temporal resolution.

טכניקת הדמיה חסכנית של זרימה נימית באמצעות אבקות הדפסה פולימריות תלת מימדיות

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in ...

ויזואליזציה של דינמיקת פולימרים למיטוב איכות הדפסה בתלת-ממד

Real-Time Imaging of Bonding in 3D-Printed Layers

In recent times, 3D printing technology has revolutionized our ability to design and produce products, but optimizing the print quality can be challenging. The process of extrusion 3D printing involves pressuring molten material through a thin nozzle and depositing it onto previously extruded material. This method relies on bonding between the consecutive layers to create a strong and visually appealing final product. This is no easy task, as many parameters, such as the nozzle temperature, layer thickness, and printing speed, must be fine-tuned to achieve optimal results. In this study, a method for visualizing the polymer dynamics during extrusion is presented, giving insight into the layer bonding process. Using laser speckle imaging, the plastic flow and fusion can be resolved non-invasively, internally, and with high spatiotemporal resolution. This measurement, which is easy to perform, provides an in-depth understanding of the underlying mechanics influencing the final print quality. This methodology was tested with a range of cooling fan speeds, and the results showed increased polymer motion with lower fan speeds and, thus, explained the poor printing quality when the cooling fan was turned off. These findings show that this methodology allows for optimizing the printing settings and understanding the material behavior. This information can be used for the development and testing of novel printing materials or advanced slicing procedures. With this approach, a deeper understanding of extrusion can be built to take 3D printing to the next level.

מחבר זרקור: הדמיה בזמן אמת של מליטה בשכבות מודפסות בתלת-ממד  

With a non-invasive and real-time technique, nanoscopic polymer motion inside a polymer filament is imaged during 3D printing. Fine-tuning this motion is crucial for producing constructs with optimal performance and appearance. This method reaches the core of plastic layer fusion, thus offering insights into optimal printing conditions and material design criteria.