Investigation of Particle Velocity and Drag with Spherical and Non-spherical Particles Through a Backward Facing Step PDF Download
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Author: Kyle Frederick Larsen
Publisher:
ISBN: 9780549080695
Category : Dispersion
Languages : en
Pages : 132
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Book Description
In this work, a Phase Doppler Particle Analyzer (PDA) was used to measure gas and particle phase velocities in a backward facing step. The step produced a 2:1 increase in cross sectional area with a Reynolds number of 22,000 (based on step height) upstream of the step. Spherical particles of 1--10 mum with an average diameter of 4mum were used to measure the gas phase velocity. At least three sizes in the range of (38--212 mum) for four different particles shapes were studied. The shapes included: spheres, flakes, gravel, and cylinders. Since the PDPA is not able to measure the size of the non-spherical particles, the particles were first separated into size bins and a technique was developed using the PMT (photo multiplier tubes) gain to isolate the particle size of interest for each size measured. The same technique was also used to measure terminal velocities of the particles in quiescent air.
Author: Kyle Frederick Larsen
Publisher:
ISBN: 9780549080695
Category : Dispersion
Languages : en
Pages : 132
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Book Description
In this work, a Phase Doppler Particle Analyzer (PDA) was used to measure gas and particle phase velocities in a backward facing step. The step produced a 2:1 increase in cross sectional area with a Reynolds number of 22,000 (based on step height) upstream of the step. Spherical particles of 1--10 mum with an average diameter of 4mum were used to measure the gas phase velocity. At least three sizes in the range of (38--212 mum) for four different particles shapes were studied. The shapes included: spheres, flakes, gravel, and cylinders. Since the PDPA is not able to measure the size of the non-spherical particles, the particles were first separated into size bins and a technique was developed using the PMT (photo multiplier tubes) gain to isolate the particle size of interest for each size measured. The same technique was also used to measure terminal velocities of the particles in quiescent air.
Author: Dean A. Wilson
Publisher:
ISBN:
Category : Dynamics of a particle
Languages : en
Pages : 36
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Book Description
Author: Stanford University. Thermosciences Division. Thermosciences Division
Publisher:
ISBN:
Category :
Languages : en
Pages : 242
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Book Description
Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 1518
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Book Description
Author: David Lee Black
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 658
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Book Description
Author: Margaret Byron
Publisher:
ISBN:
Category :
Languages : en
Pages : 159
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Book Description
The motion of particles suspended in environmental turbulence is relevant to many scientific fields, from sediment transport to biological interactions to underwater robotics. At very small scales and simple shapes, we are able to completely mathematically describe the motion of inertial particles; however, the motion of large aspherical particles is significantly more complex, and current computational models are inadequate for large or highly-resolved domains. Therefore, we seek to experimentally investigate the coupling between freely suspended particles and ambient turbulence. A better understanding of this coupling will inform not only engineering and physics, but the interactions between small aquatic organisms and their environments. In the following pages, we explore the roles of shape and buoyancy on the motion of passive particles in turbulence, and allow these particles to serve as models for meso-scale aquatic organisms. We fabricate cylindrical and spheroidal particles and suspend them in homogeneous, isotropic turbulence that is generated via randomly-actuated jet arrays. The particles are fabricated with agarose hydrogel, which is refractive-index-matched to the surrounding fluid (water). Both the fluid and the particle are seeded with passive tracers, allowing us to perform Particle Image Velocimetry (PIV) simultaneously on the particle and fluid phase. To investigate the effects of shape, particles are fabricated at varying aspect ratios; to investigate the effects of buoyancy, particles are fabricated at varying specific gravities. Each particle type is freely suspended at a volume fraction of [Phi]=0.1%, for which four-way coupling interactions are negligible. The suspended particles are imaged together with the surrounding fluid and analyzed using stereoscopic PIV, which yields three velocity components in a two-dimensional measurement plane. Using image thresholding, the results are separated into simultaneous fluid-phase and solid-phase velocity fields. Using these simultaneous measurements, we examine particles' turbulent slip velocity and compare it to particles' quiescent settling velocity, which we measure directly. We observe that the slip velocity is strongly reduced relative to the quiescent case, and explore various mechanisms of particle loitering in turbulence. We further explore the relationship between the instantaneous particle velocity and the instantaneous fluid velocity, and develop a linear parametrization. By comparing our experimental data to a simple one-dimensional flow in the context of this parametrization, we elucidate aspects of slip velocity that are unique to turbulence. We obtain the particles' angular velocity by applying the solid-body rotation equation to velocity measurements at points inside the particle. We find that the expected value of angular velocity magnitude does not vary significantly with particle aspect ratio, as long as particles are nearly neutrally buoyant. Stronger effects on rotation are found for more negatively-buoyant particles. We also investigate particles' inheritance of vorticity from turbulent velocity fields, and find that particle rotation can be predicted by applying a spatial filter to fluid-phase vorticity. The results of this study will allow us to more accurately predict the motion of aspherical particles, giving new insights into oceanic carbon cycling, industrial processes, and other important topics. This analysis will also shed light onto biological questions of navigation, reproduction, and predator-prey interaction by quantifying the turbulence-driven behavior of meso-scale aquatic organisms, allowing researchers to sift out passive vs. active effects in a behaving organism. Lastly, processes that are directly dependent on particle dynamics (e.g., sediment transport, industrial processes) will be informed by our results.
Author: G. E. Stringham
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 90
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Book Description
Author: Doychev, Todor
Publisher: KIT Scientific Publishing
ISBN: 3731503077
Category : Engineering (General). Civil engineering (General)
Languages : en
Pages : 272
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Book Description
This book contributes to the fundamental understanding of the physical mechanisms that take place in pseudo turbulent particulate flows. In the present work we have considered the sedimentation of large numbers of spherical rigid particles in an initially quiescent flow field. We have performed direct numerical simulations employing an immersed boundary method for the representation of the fluid-solid interface. The results evidence that depending on the particle settling regime (i.e. Galileo number and particle-to-fluid density ratio) the particles may exhibit strong inhomogeneous spatial distribution. It is found that the particles are preferentially located in regions with downward fluid motion. The particles inside clusters experience larger settling velocities than the average. The flow in all flow cases is observed to exhibit characteristic features of pseudo-turbulence. The particle-induced flow field is further found to be highly anisotropic with dominant vertical components. The results indicate that, in the present flow configurations, the collective and mobility effects play significant role for the particle and fluid motion.
Author:
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 572
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Book Description
Author: David M Kelly
Publisher: CRC Press
ISBN: 1351119524
Category : Technology & Engineering
Languages : en
Pages : 376
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Book Description
This book will serve as a reference guide, and state-of-the-art review, for the wide spectrum of numerical models and computational techniques available to solve some of the most challenging problems in coastal engineering. The topics covered in this book, are explained fundamentally from a numerical perspective and also include practical examples applications. Important classic themes such as wave generation, propagation and breaking, turbulence modelling and sediment transport are complemented by hot topics such as fluid and structure interaction or multi-body interaction to provide an integral overview on numerical techniques for coastal engineering. Through the vision of 10 high impact authors, each an expert in one or more of the fields included in this work, the chapters offer a broad perspective providing several different approaches, which the readers can compare critically to select the most suitable for their needs. Advanced Numerical Modelling of Wave Structure Interaction will be useful for a wide audience, including PhD students, research scientists, numerical model developers and coastal engineering consultants alike.
