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Full-Text Articles in Physics

Influence Of Grain Size Distribution On Ultrasonic Scattering, Andrea Arguelles, Joseph A. Turner Jan 2016

Influence Of Grain Size Distribution On Ultrasonic Scattering, Andrea Arguelles, Joseph A. Turner

Review of Progress in Quantitative Nondestructive Evaluation

Elastic wave scattering at grain boundaries in polycrystalline media can be quantified to determine microstructural properties. The amplitude drop observed for coherent wave propagation (attenuation) as well as diffuse-field scattering events (such as the single-scattering response) have been extensively studied. In all cases, the scattering shows a clear dependence on grain size, grain geometric morphology, and material texture (i.e., macroscale anisotropy). Scattering models used to quantify such scattering experiments are often developed under the assumption of a single effective grain diameter implying a very narrow distribution of grain size throughout the sample. However, several microscopy studies suggest that most ...


Novel Methods To Measure Surface Wave Velocity By Using Laser-Generated Tone-Burst Surface Wave, Ju-Ho Lee, Jongbeom Kim, Kyung-Young Jhang Jan 2016

Novel Methods To Measure Surface Wave Velocity By Using Laser-Generated Tone-Burst Surface Wave, Ju-Ho Lee, Jongbeom Kim, Kyung-Young Jhang

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic wave velocity is a characteristic of material, which is considered as a significant factor of nondestructive testing (NDT) techniques. Generally, bulk wave velocity is measured by Time-of-Flight (TOF) of pulse echo from back wall reflection; however, pulse-echo method cannot be applied to surface acoustic wave in a case that an edge does not exist in a close range. Even when we use through-transmission method, it is quite cumbersome to measure the accurate distance between transmitter and receiver; this problem is more critical when using contact angle transducers.

This study proposes two new signal processing methods to measure laser-generated surface ...


Calibration Of Air-Coupled Transducers For Absolute Nonlinear Ultrasonic Measurements, Nicholas Selby, David Torello, Jin-Yeon Kim, Laurence J. Jacobs Jan 2016

Calibration Of Air-Coupled Transducers For Absolute Nonlinear Ultrasonic Measurements, Nicholas Selby, David Torello, Jin-Yeon Kim, Laurence J. Jacobs

Review of Progress in Quantitative Nondestructive Evaluation

We describe a novel calibration technique of air-coupled transducers for nonlinear ultrasonic measurements through homogenous, isotropic media. Our calibration technique combines laser interferometrywith a model-based approach to derive a relationship between received force at the transducer face and the measured output voltage. Conventional nonlinear ultrasonic measurement techniques have relied upon contact receiving transducers that are heavily influenced by contact conditions (e.g. inconsistent coupling) and laser interferometers that are prohibitively expensive and rely on a mirror-finished surface or complicated optics. Air-coupled transducers are significantly less expensive than laser interferometers and are robust relative to surface conditions, but current calibration techniques ...


Characterization Of An Electrodynamic Flexural Transducer For Air-Coupled Ultrasonics, Tobias J. R. Eriksson, Yichao Fan, Sivaram Nishal Ramadas, Steve Dixon Jan 2016

Characterization Of An Electrodynamic Flexural Transducer For Air-Coupled Ultrasonics, Tobias J. R. Eriksson, Yichao Fan, Sivaram Nishal Ramadas, Steve Dixon

Review of Progress in Quantitative Nondestructive Evaluation

Air-coupled ultrasonics (ACU) has had an increasing importance in non-destructive evaluation (NDE), particularly for inspection of composite materials for example in the aerospace industry [1]. The main problem for ACU is the large impedance mismatch between piezoelectric ceramics and air, and a lack of suitable materials for impedance matching [2]. Many different solutions to this problem have led to a range of transducer technologies and designs, e.g. composite transducers and capacitive micromachined ultrasonic transducers (CMUTs). In previous work by the authors three designs of a novel ACU transducer, combining electromagnetic coupling and flexural mode vibrations, so called electrodynamic flexural ...


A Novel Thermosonic Imaging System For Non-Destructive Testing, Dan Xiang, Micheal Long, Carson Willey Jan 2016

A Novel Thermosonic Imaging System For Non-Destructive Testing, Dan Xiang, Micheal Long, Carson Willey

Review of Progress in Quantitative Nondestructive Evaluation

Thermosonic (Sonic IR) Imaging is a new nondestructive testing (NDT) technique that uses high-frequency sonic excitation together with infrared (IR) detection to image surface and subsurface defects. This Sonic IR imaging technique uses a short (usually fraction of a second) pulse of high frequency (typically 20-40 kHz) sound which is applied at some convenient point on the surface of the object under inspection to produce localized frictional heating at the defect. An IR camera images the heating of the surface resulting from the effects of friction or other irreversible internal surface interactions in the vicinity of defects. These effects result ...


Non-Contact Evaluation Of Residual Stress In Metals With Laser-Generated Surface Acoustic Waves And A Point-Like Fiber-Optic Sagnac Detector, Łukasz Ambrozinski, Ivan Pelivanov, Michael B. Prime, Matthew O’Donnell Jan 2016

Non-Contact Evaluation Of Residual Stress In Metals With Laser-Generated Surface Acoustic Waves And A Point-Like Fiber-Optic Sagnac Detector, Łukasz Ambrozinski, Ivan Pelivanov, Michael B. Prime, Matthew O’Donnell

Review of Progress in Quantitative Nondestructive Evaluation

Stress can remain in a material after the original load is removed. It can be purposely introduced to improve the properties of structural components, but can also be undesired, shortening a component’s lifetime, changing its original geometry or even leading to failure.

There is a large spectrum of problems where residual stress must be evaluated. An acousto-elastic approach is non-destructive and uses stress-dependent alterations in ultrasound (US) speed of bulk or surface modes [1]. However, these alterations are incredibly small (10-3 ÷ 10-5) and, thus, accurate measurement of both the US wave speed and propagation distance is required. Thickness measurement ...


Study The Nonlinearity In Sonic Ir Imaging Nde, Xiaoyan Han, Qiuye Yu, Omar Obeidat Jan 2016

Study The Nonlinearity In Sonic Ir Imaging Nde, Xiaoyan Han, Qiuye Yu, Omar Obeidat

Review of Progress in Quantitative Nondestructive Evaluation

Sonic IR Imaging combines pulsed ultrasound excitation and infrared imaging to detect defects in materials. The sound pulse causes rubbing due to non-‐unison motion between faces of defects, and infrared sensors image the temperature map over the target to identify defects. It works in various materials, including metal/metal alloy, ceramics, and composite materials. Its biggest advantage is that it's a fast, wide area NDE technique. It takes only a fraction of a second or a few seconds, depending on the thermal properties of the target, for one test over a few square feet. However, due to the ...


Elastic Wave Fields Generated By Shear Horizontal Piezoelectric Fiber Patch (Sh-Pfp) Transducers: Parameter Study By Modelling And Laser Vibrometric Measurements, Bernd Köhler, Tobias Gaul, Frank Schubert, Uwe Lieske Jan 2016

Elastic Wave Fields Generated By Shear Horizontal Piezoelectric Fiber Patch (Sh-Pfp) Transducers: Parameter Study By Modelling And Laser Vibrometric Measurements, Bernd Köhler, Tobias Gaul, Frank Schubert, Uwe Lieske

Review of Progress in Quantitative Nondestructive Evaluation

Recently, a novel lightweight and thin piezoelectric transducer was proposed [1-3]. It generates in-plane surface tractions and thus shear horizontal elastic waves in both bulk materials and waveguides. The paper describes the principle of operation of this Shear Horizontal Piezoelectric Fiber Patch (SH-PFP). In continuation of the previous work, several variants of the SH-PFP are studied. The generated wavefield is characterized bywavefield snapshots and directivity functions. Both numerical simulation and measurements by 3D Laser Vibrometry are performed and the results are compared, showing a good agreement. We discuss possible further developments of the SH-PFP transducer to allow 1D directivity and ...


Crack Detection Using Low-Frequency Ultrasonic Waves Caused By Low Directivity And Scattering, Shingo Onodera, Yuji Kato, Toshihiko Sugiura Jan 2016

Crack Detection Using Low-Frequency Ultrasonic Waves Caused By Low Directivity And Scattering, Shingo Onodera, Yuji Kato, Toshihiko Sugiura

Review of Progress in Quantitative Nondestructive Evaluation

In recent years, nondestructive testing techniques for maintenance and checking of materials and structures have been more required with social infrastructure’s aging. Although ultrasonic waves are valid in internal inspection, conventional ultrasonic detection techniques are inadequate for detecting fatigues or closed cracks, because ultrasound waves hardly reflect at them[1]. However, it has been reported that the transmitted wave through a closed crack contains nonlinear ultrasonic waves[2] such as super- and sub- harmonics, and they have been expected to be used for an alternative detecting method.

In our previous research, we experimentally examined transmission of ultrasonic waves through ...


Validation Of Utsim2, A New Ultrasonic Simulation Package, Robert Grandin, Timothy Gray Jan 2016

Validation Of Utsim2, A New Ultrasonic Simulation Package, Robert Grandin, Timothy Gray

Review of Progress in Quantitative Nondestructive Evaluation

The Center for NDE (CNDE) at Iowa State University has a long history of developing physics models for NDE and packaging these models into simulation tools which make the modeling capabilities accessible to CNDE’s industrial sponsors. Recent work at CNDE has led to the development of a new ultrasonic simulation package, UTSim2, which aims to continue this tradition of supporting industrial application of CNDE models. In order to meet this goal, UTSim2 has been designed as an extensible software package which can support previously-developed physics models as well as future models yet to be developed. Initial work has focused ...


Characterizing Acoustic Fluidized Bed Hydrodynamics Using X-Ray Computed Tomography, David R. Escudero, Theodore J. Heindel Jul 2013

Characterizing Acoustic Fluidized Bed Hydrodynamics Using X-Ray Computed Tomography, David R. Escudero, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized bed reactors are important assets of many industrial applications because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Characterizing the hydrodynamics of a fluidized bed is important to better understand the behavior of these multiphase flow systems. The hydrodynamic behavior in a cold flow 3D fluidized bed, with and without acoustic intervention, using X-ray computed tomography is investigated in this study. Experiments are carried out in a 10.2 cm ID fluidized bed filled with glass beads, with material density of 2600 kg/m3 and particle size ranges between 212–600 μm. In ...


A High-Speed X-Ray Detector System For Noninvasive Fluid Flow Measurements, Timothy B. Morgan, Benjamin R. Halls, Terrence R. Meyer, Theodore J. Heindel Jul 2013

A High-Speed X-Ray Detector System For Noninvasive Fluid Flow Measurements, Timothy B. Morgan, Benjamin R. Halls, Terrence R. Meyer, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

The opaque nature of many multiphase flows has long posed a significant challenge to the visualization and measurement of desired characteristics. To overcome this difficulty, X-ray imaging, both in the form of radiography and computed tomography, has been used successfully to quantify various multiphase flow phenomena. However, the relatively low temporal resolution of typical X-ray systems limit their use to moderately slow flows and time-average values. This paper discusses the development of an X-ray detection system capable of high-speed radiographic imaging that can be used to visualize multiphase flows. Details of the hardware will be given and then applied to ...


Acoustic Field Effects On Minimum Fluidization Velocity In A 3d Fluidized Bed, David R. Escudero, Theodore J. Heindel Jul 2012

Acoustic Field Effects On Minimum Fluidization Velocity In A 3d Fluidized Bed, David R. Escudero, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds are used in a variety of process industries because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Minimum fluidization velocity is an important factor in understanding the hydrodynamic behavior of fluidized beds, and this characteristic may be modified through high frequency (sound) vibrations. The effects caused by sound wave frequency on the minimum fluidization velocity in a 3D fluidized bed are investigated in this study. Experiments are carried out in a 10.2 cm ID cold flow fluidized bed filled with glass beads with material density of 2600 kg/m3, and particles ...


Cavitation From A Butterfly Valve: Comparing 3d Simulations To 3d X-Ray Computed Tomography Flow Visualization, Graham Brett, Marc Riveland, Terrence C. Jensen, Theodore J. Heindel Jul 2011

Cavitation From A Butterfly Valve: Comparing 3d Simulations To 3d X-Ray Computed Tomography Flow Visualization, Graham Brett, Marc Riveland, Terrence C. Jensen, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Flow control valves may experience localized cavitation when the local static pressure drops to the liquid vapor pressure. Localized damage to the valve and surrounding area can occur when the vapor cavity collapses. Valve designs that reduce cavitation are based on empirical evidence and accumulated experience, but there are still considerable cavitation problems in industry. Valve designers may use computational fluid dynamics (CFD) to simulate cavitation in flow control valves, but model validation is challenging because there are limited data of local cavitation from the valve surface. Typically, the intensity of cavitation in a control valve is inferred from measurements ...


A Method To Quantify Mixing In A Two Component Fluidized Bed, Norman K. Keller, Theodore J. Heindel Aug 2010

A Method To Quantify Mixing In A Two Component Fluidized Bed, Norman K. Keller, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized bed technology can be used for pyrolysis and gasification of solid fuel particles such as biomass, which is important to industry because of its potential as an alternative for petroleum-based fuels. To efficiently utilize a fluidized bed reactor it is necessary, among other factors, to investigate the mixing and segregation behavior of the fuel particles with the bed material. In order to characterize the material distribution, a technique to visualize the biomass inside a fluidized bed reactor has been developed using X-ray computed tomography (CT) scans. This paper presents an image analysis procedure that can be used to quantify ...


Modeling A Biomass Fluidizing Bed With Side Port Air Injection, Mirka Deza, Francine Battaglia, Theodore J. Heindel Aug 2009

Modeling A Biomass Fluidizing Bed With Side Port Air Injection, Mirka Deza, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds are used to gasify materials such as coal or biomass in the production of producer gas. Modeling these reactors using computational fluid dynamics is advantageous when performing parametric studies for design and scale-up. While two-dimensional simulations are easier to perform than three-dimensional simulations, they may not capture the proper physics. This paper compares two- and three-dimensional simulations with experiments for a reactor geometry with side port air injection. The side port is located within the bed region so that the injected air can help promote mixing. Of interest in this study is validating the hydrodynamics of fluidizing biomass ...


Repeatability Of Gas Holdup In A Fluidized Bed Using X-Ray Computed Tomography, Joshua B. Drake, Theodore J. Heindel Aug 2009

Repeatability Of Gas Holdup In A Fluidized Bed Using X-Ray Computed Tomography, Joshua B. Drake, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Characterizing the hydrodynamics in fluidized beds is important to many processes from producing biofuels to coating pharmaceuticals. X-ray computed tomography (CT) can quantify local time-averaged phase fractions in multiphase systems that are highly dynamic, like fluidized beds. This paper describes the calibration methods used to produced CT images of a 15.24 cm diameter fluidized bed, how in-house software used these CTs to calculate gas holdup, and how well multiple CTs of a dynamic fluidized bed produced repeatable results while varying bed material and superficial gas velocities. It was concluded there is a very high degree of repeatability using the ...


X-Ray Particle Tracking Velocimetry In Fluidized Beds, Joshua B. Drake, Lie Tang, Theodore J. Heindel Aug 2009

X-Ray Particle Tracking Velocimetry In Fluidized Beds, Joshua B. Drake, Lie Tang, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds are commonly found in the chemical and energy processing industries because of their low pressure drop, uniform temperature distribution, and high heat transfer rates. For example, in biomass gasification, biomass particles are injected into a heated bubbling bed of inert material (typically refractory sand) that volatilizes to form a flammable gas. However, the movement of the biomass particle through the bubbling bed is difficult to quantify because the systems are opaque. This paper describes X-ray particle tracking velocimetry (XPTV) applied to fluidized beds, where X-ray flow visualization is used to track the location of a single fabricated tracer ...


Approximating A Three-Dimensional Fluidized Bed With Two-Dimensional Simulations, Mirka Deza, Francine Battaglia, Theodore J. Heindel Oct 2008

Approximating A Three-Dimensional Fluidized Bed With Two-Dimensional Simulations, Mirka Deza, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Modeling these reactors with computational fluid dynamics (CFD) simulations is advantageous when performing parametric studies for design and scale-up. From a computational resource point of view, two-dimensional simulations are easier to perform than three-dimensional simulations, but they may not capture the proper physics. This paper will compare two- and three-dimensional simulations in a 10.2 cm diameter fluidized bed with side air injection to determine when two-dimensional simulations are adequate to capture the bed hydrodynamics ...


Minimum Fluidization Velocity And Gas Holdup In Fluidized Beds With Side Port Air Injection, Nathan P. Franka, Joshua B. Drake, Theodore J. Heindel Aug 2008

Minimum Fluidization Velocity And Gas Holdup In Fluidized Beds With Side Port Air Injection, Nathan P. Franka, Joshua B. Drake, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Knowing how the fluidized bed hydrodynamics vary as reactor dimensions are scaled up is vital for improving reactor efficiency. This study utilizes 10.2 cm and 15.2 cm diameter fluidized beds with added side port air injection to investigate column diameter effects on fluidized bed hydrodynamics. Both inert (glass beads) and biomass (ground walnut shell and ground corncob) bed materials are used and the hydrodynamic differences with side port air injection are recorded. Minimum ...


A Validation Study For The Hydrodynamics Of Biomass In A Fluidized Bed, Mirka Deza, Francine Battaglia, Theodore J. Heindel Aug 2008

A Validation Study For The Hydrodynamics Of Biomass In A Fluidized Bed, Mirka Deza, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Computational modeling of fluidized beds can be used to predict operation of biomass gasifiers after extensive validation with experimental data. The present work focused on computational simulations of a fluidized bed using a multifluid Eulerian-Eulerian model to represent the gas and solid phases as interpenetrating continua. Hydrodynamic results from the simulations were quantitatively compared with X-ray flow visualization studies of a similar bed. It was found that the Gidaspow model can accurately predict the hydrodynamics of the biomass in a fluidized bed. The coefficient of restitution of biomass was fairly high and did not affect the hydrodynamics of the bed ...


Qualitative Observations Of Dense Particle Motion In A Vibration-Excited Granular Bed, Timothy B. Morgan, Theodore J. Heindel Nov 2007

Qualitative Observations Of Dense Particle Motion In A Vibration-Excited Granular Bed, Timothy B. Morgan, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

The Brazil nut effect is a classic phenomenon in which larger objects typically migrate to the top of a bed of smaller granular media when exposed to vibration. An example of this phenomenon is finding Brazil nuts on the top of a can of mixed nuts. In this study, the Brazil nut problem is simulated by submerging a large particle in a bed of granular media and then subjecting the system to vibration. Stereoscopic X-ray imaging is used to visualize the large particle motion. These images are then compiled into movies where the particle motion may be tracked. Observations of ...


Stability Issues For Gas-Liquid Flows In Bubble Columns, Deify Law, Francine Battaglia, Theodore J. Heindel Nov 2007

Stability Issues For Gas-Liquid Flows In Bubble Columns, Deify Law, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

In the present work, gas-liquid flow dynamics in a bubble column are simulated with CFDLib using an Eulerian-Eulerian ensemble-averaging method in a two dimensional Cartesian system. The time-averaged gas holdup simulations are compared to experimental measurements of a cylindrical bubble column performed by Rampure et al. [1]. Numerical predictions are presented for the time-averaged gas holdup at various axial heights as a function of radial position. The effects of grid resolution, bubble pressure model, and drag coefficient models on the numerical predictions are examined. The bubble pressure model is reported to account for bubble stability, thus providing physical solutions. The ...


Visualizing Fluid Flows With X-Rays, Theodore J. Heindel, Terrence C. Jensen, Joseph N. Gray Jul 2007

Visualizing Fluid Flows With X-Rays, Theodore J. Heindel, Terrence C. Jensen, Joseph N. Gray

Mechanical Engineering Conference Presentations, Papers, and Proceedings

There are several methods available to visualize fluid flows when one has optical access. However, when optical access is limited to near the boundaries or not available at all, alternative visualization methods are required. This paper will describe flow visualization using an X-ray system that is capable of digital X-ray radiography, digital X-ray stereography, and digital X-ray computed tomography (CT). The unique X-ray flow visualization facility will be briefly described, and then flow visualization of various systems will be shown. Radiographs provide a two-dimensional density map of a three dimensional process or object. Radiographic images of various multiphase flows will ...


Numerical Simulations Of Gas-Liquid Flow Dynamics In Bubble Columns, Deify Law, Francine Battaglia, Theodore J. Heindel Nov 2006

Numerical Simulations Of Gas-Liquid Flow Dynamics In Bubble Columns, Deify Law, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

There is great potential for using computational fluid dynamics (CFD) as a tool in scale-up and design of bubble columns. Full-scale experimentation in bubble columns is expensive and CFD is an alternative approach to study bubble column hydrodynamics. However, CFD can be computationally intensive as a predictive tool for a full three-dimensional geometry. In this paper, a 0.2 m diameter semi-batch bubble column is numerically simulated and the results are compared to experimental measurements performed by Rampure et al. [1]. The objectives are to examine and determine an appropriate set of numerical parameters and to determine if two-dimensional simulations ...


The Effect Of A Modified Downcomer On The Hydrodynamics In An External Loop Airlift Reactor, Samuel T. Jones, Theodore J. Heindel Jul 2006

The Effect Of A Modified Downcomer On The Hydrodynamics In An External Loop Airlift Reactor, Samuel T. Jones, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Gas holdup and superficial liquid velocity in the downcomer and riser are studied for an external loop airlift reactor with an area ratio of 1:16. Two downcomer configurations are investigated consisting of the downcomer open or closed to the atmosphere. Experiments for these two configurations are carried out over a range of superficial gas velocities from UG = 0.5 to 20 cm/s using three aeration plates with open area ratios of 0.62, 0.99 and 2.22%. These results are compared to a bubble column operated with similar operating conditions. Experimental results show that the gas holdup ...


Using X-Rays For Multiphase Flow Visualization, Theodore J. Heindel, Jeremy L. Hubers, Terrence C. Jensen, Joseph N. Gray, Alexander C. Stiegel Jun 2005

Using X-Rays For Multiphase Flow Visualization, Theodore J. Heindel, Jeremy L. Hubers, Terrence C. Jensen, Joseph N. Gray, Alexander C. Stiegel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Gas-liquid, gas-solid, liquid-solid, and gas-liquid-solid multiphase flows are difficult to visualize, characterize, and quantify because the systems are typically opaque. Invasive or noninvasive measurement methods are typically used for determining internal flow and transport characteristics of these complex flows. The difficulty with invasive methods is that they can alter the internal flow of a multiphase system causing interference with realistic process measurements. X-ray imaging provides one family of noninvasive measurement techniques used extensively for product testing and evaluation of static objects with complex structures. These techniques have been extended to visualize dynamic systems, such as those which characterize multiphase flows ...


Gas Holdup In Opaque Cellulose Fiber Slurries, Sarah M. Talcott, Theodore J. Heindel Jun 2005

Gas Holdup In Opaque Cellulose Fiber Slurries, Sarah M. Talcott, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Three different cellulose fiber types are used to study their effect on gas holdup and flow regime transition in a 10.2 cm semi-batch bubble column. The three natural fiber types include bleached softwood chemical pulp (softwood), bleached hardwood chemical pulp (hardwood), and bleached softwood chemithermomechanical pulp (BCTMP). Gas holdup is recorded over a range of fiber mass fractions (0 ≤ C ≤ 1.6%) and superficial gas velocities (Ug ≤ 23 cm/s). Experimental results show that gas holdup decreases with increasing fiber mass fraction. Homogeneous, transitional, and heterogeneous flow is observed for all three fiber types at low fiber mass fractions ...


Ultrasonic System Models And Measurements , Ana Lilia Lopez-Sanchez Jan 2005

Ultrasonic System Models And Measurements , Ana Lilia Lopez-Sanchez

Retrospective Theses and Dissertations

In this work ultrasonic models and measurements are used to characterize a number of the important elements of an ultrasonic measurement system as well as the entire system. Ultrasonic measurement models for predicting the response from reference reflectors are described, including a new ultrasonic measurement model recently developed to simulate the ultrasonic response of an infinitely long cylindrical cavity. The reference reflectors considered include spherical pores, flat-bottom holes and side-drilled holes, which are commonly used in nondestructive evaluation studies. These reflectors are employed in a series of modeling/experimental studies to assess where approximate and more exact scattering models are ...


Effect Of Gas Distributor On Gas Holdup In Fiber Suspensions, Xufeng Su, Theodore J. Heindel Jul 2004

Effect Of Gas Distributor On Gas Holdup In Fiber Suspensions, Xufeng Su, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Two different aeration plates are used to study their effect on gas holdup and flow regime transition in fiber suspensions. Two gas distributors with different open areas (A = 0.57% and 2.14%) and the same orifice diameter (do = 1 mm) are used, and experiments are performed using three different Rayon fiber lengths (L = 3, 6, and 12 mm) over a range of superficial gas velocities (Ug ≤ 18 cm/s) and a range of fiber mass fractions (0 ≤ C ≤ 1.8%) in a 15.24 cm diameter semi-batch bubble column. Experimental results show that the distributor with A = 2.14 ...