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2015

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Full-Text Articles in Mechanical Engineering

A Framework For Control Of Robots With Energy Regeneration, Hanz Richter Dec 2015

A Framework For Control Of Robots With Energy Regeneration, Hanz Richter

Hanz Richter

This paper focuses on robot control problems where energy regeneration is an explicit consideration, and it proposes a methodology for modeling and control design of regenerative motion control systems. The generic model consists of a robotic manipulator where some joints are actively controlled and the remaining joints are energetically self-contained and semi-actively controlled. The model can capture various electromechanical and hydraulic actuator configurations for industrial robots and powered human-assist devices. The basic control approach consists of three steps. First, a virtual control design is conducted by any suitable means. Then, virtual control inputs are enacted by a matching law for …


Motion Control Of A Container With Slosh: Constrained Sliding Mode Approach, Hanz Richter Dec 2015

Motion Control Of A Container With Slosh: Constrained Sliding Mode Approach, Hanz Richter

Hanz Richter

A constrained sliding mode control methodology developed by the author is applied to the motion control of an open container filled with liquid. The objective is to control the position of the container to meet the performance and robustness requirements, and to specify a safe operating set, i.e., the set of initial conditions from which the system can be operated without exceeding a prescribed liquid level and additional constraints. A conventional sliding mode regulator is designed first to address nominal performance in the sliding mode. Then, a robustly invariant cylinder formed as the Cartesian product of an ellipsoid, and a …


Muscle Synergies Improve Estimation Of Knee Contact Forces During Walking, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd Dec 2015

Muscle Synergies Improve Estimation Of Knee Contact Forces During Walking, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd

Allison Kinney

This study investigates whether use of subject-specific muscle synergies can improve optimization predictions of muscle excitation patterns and knee contact forces during walking. Muscle synergies describe how a small number of neural commands generated by the nervous system can be linearly combined to produce the broad range of muscle electromyographic (EMG) signals measured experimentally. By quantifying the interdependence of individual EMG signals, muscle synergies provide dimensionality reduction for the neural control redundancy problem. Our hypothesis was that use of subjectspecific muscle synergies to limit muscle excitation patterns would improve prediction of muscle EMG patterns at the hip, knee, and ankle …


Muscle Synergy Constraints Improve Prediction Of Knee Contact Force During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd Dec 2015

Muscle Synergy Constraints Improve Prediction Of Knee Contact Force During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd

Allison Kinney

Knowledge of patient-specific muscle and joint contact forces during activities of daily living could improve the treatment of movement-related disorders (e.g., osteoarthritis, stroke, cerebral palsy, Parkinson’s disease). Unfortunately, it is currently impossible to measure these quantities directly under common clinical conditions, and calculation of these quantities using computer models is limited by the redundant nature of human neural control (i.e., more muscles than theoretically necessary to actuate the available degrees of freedom in the skeleton). Walking is a particularly important task to understand, since loss of mobility is associated with increased morbidity and decreased quality of life. Though numerous musculoskeletal …


Evaluation Of Different Optimal Control Problem Formulations For Solving The Muscle Redundancy Problem, Friedl De Groote, Allison Kinney, Anil Rao, Benjamin Fregly Dec 2015

Evaluation Of Different Optimal Control Problem Formulations For Solving The Muscle Redundancy Problem, Friedl De Groote, Allison Kinney, Anil Rao, Benjamin Fregly

Allison Kinney

This study evaluates several possible optimal control problem formulations for solving the muscle redundancy problem with the goal of identifying the most efficient and robust formulation. One novel formulation involves the introduction of additional controls that equal the time derivative of the states, resulting in very simple dynamic equations. The nonlinear equations describing muscle dynamics are then imposed as algebraic constraints in their implicit form, simplifying their evaluation. By comparing different problem formulations for computing muscle controls that can reproduce inverse dynamic joint torques during gait, we demonstrate the efficiency and robustness of the proposed novel formulation.


Synergies Controls Improve Prediction Of Knee Contact Forces And Muscle Excitations During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd Dec 2015

Synergies Controls Improve Prediction Of Knee Contact Forces And Muscle Excitations During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd

Allison Kinney

This study investigates whether use of muscle excitation controls constructed from subjectspecific muscle synergy information can improve optimization prediction of knee contact forces and muscle excitations during walking. Muscle synergies quantify how a large number of experimental muscle electromyographic (EMG) signals can be reconstructed by linearly mixing a much smaller number of neural commands generated by the nervous system. Our hypothesis was that controlling all muscle excitations with a small set of experimentally calculated neural commands would improve prediction of knee contact forces and leg muscle excitations compared to using independently controlled muscle excitations.


Comparison Of Material Properties And Microstructure Of Specimens Built Using The 3d Systems Vanguard Hs And Vanguard Hiq+Hs Sls Systems, T.J. Silverman, Allison Kinney, W. Yong, J.H. Koo Dec 2015

Comparison Of Material Properties And Microstructure Of Specimens Built Using The 3d Systems Vanguard Hs And Vanguard Hiq+Hs Sls Systems, T.J. Silverman, Allison Kinney, W. Yong, J.H. Koo

Allison Kinney

The HiQ upgrade to the 3D Systems Vanguard selective laser sintering (SLS) machine incorporates a revised thermal calibration system and new control software. The paper compares the tensile modulus, tensile strength, elongation at break, flexural modulus, Izod impact resistance and microstructure of two batteries of standard specimens built from recycled Duraform PA (Nylon 12). The first set is built on a Vanguard HS system and the second on the same system with the HiQ upgrade installed. The upgrade reduces user intervention, decreases total build time and improves surface finish. However, using the default processing parameters, tensile, flexure and impact properties …


Comparing Mathematical And Heuristic Approaches For Scientific Data Analysis, Aparna Varde, Shuhui Ma, Mohammed Maniruzzaman, David Brown, Elke Rundensteiner, Richard Sisson Dec 2015

Comparing Mathematical And Heuristic Approaches For Scientific Data Analysis, Aparna Varde, Shuhui Ma, Mohammed Maniruzzaman, David Brown, Elke Rundensteiner, Richard Sisson

David C. Brown

Scientific data is often analyzed in the context of domain-specific problems, for example, failure diagnostics, predictive analysis, and computational estimation. These problems can be solved using approaches such as mathematical models or heuristic methods. In this paper we compare a heuristic approach based on mining stored data with a mathematical approach based on applying state-of-the-art formulae to solve an estimation problem. The goal is to estimate results of scientific experiments given their input conditions. We present a comparative study based on sample space, time complexity, and data storage with respect to a real application in materials science. Performance evaluation with …


Metal Wear Detection Apparatus And Method Employing Microfluidic Electronic Device, Jiang Zhe, Li Du, Joan Carletta, Robert Veillette Nov 2015

Metal Wear Detection Apparatus And Method Employing Microfluidic Electronic Device, Jiang Zhe, Li Du, Joan Carletta, Robert Veillette

Robert Veillette

An apparatus and a method for detection of wear particles in a lubricant are disclosed. The apparatus includes a microfluidic device including a microchannel sized for a lubricant containing wear particles to pass therethrough and first and second electrodes extending into the microchannel. A detection system is coupled with the electrodes for detection of wear particles passing through the microchannel, based on a change in capacitance of the electrodes.


Inductive Coulter Counting: Detection And Differentiation Of Metal Wear Particles In Lubricant, Li Du, Jiang Zhe, Robert Veillette Nov 2015

Inductive Coulter Counting: Detection And Differentiation Of Metal Wear Particles In Lubricant, Li Du, Jiang Zhe, Robert Veillette

Robert Veillette

A device based on an inductive Coulter counting principle for detecting metal particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring the inductance change in a coil. First, the sensing principle is demonstrated at the mesoscale using a solenoid. Next, a small planar coil suitable for use in a microscale device is tested. Static tests are conducted on the planar coil using iron and aluminum particles ranging from 80 to 500 µm. The testing results show that the coil can be used to detect and distinguish ferrous and nonferrous metal particles …


A Magnetic Coulter Counting Device For Wear Debris Detection In Lubrication, Li Du, Joan Carletta, Robert Veillette, Jiang Zhe Nov 2015

A Magnetic Coulter Counting Device For Wear Debris Detection In Lubrication, Li Du, Joan Carletta, Robert Veillette, Jiang Zhe

Robert Veillette

A device based on a magnetic Coulter counting principle to detect metal particles in lubrication oil is presented. The device detects the passage of ferrous and non ferrous particles by monitoring inductance change in a coil. First, the sensing principle is demonstrated at the mesoscale using a solenoid. Next, a microscale device is developed using a planar coil. The device is tested using iron and aluminum particles ranging from 100μm to 500μm. The testing results show the device is capable of detecting and distinguishing ferrous and non-ferrous metal particles in lubrication oil. The design concept demonstrated here can be extended …


Real-Time Monitoring Of Wear Debris In Lubrication Oil Using A Microfluidic Inductive Coulter Counting Device, Li Du, Jiang Zhe, Joan Carletta, Robert Veillette, Fred Choy Nov 2015

Real-Time Monitoring Of Wear Debris In Lubrication Oil Using A Microfluidic Inductive Coulter Counting Device, Li Du, Jiang Zhe, Joan Carletta, Robert Veillette, Fred Choy

Robert Veillette

A microfluidic device based on an inductive Coulter counting principle to detect metal wear particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring the inductance change of an embedded coil. The device was tested using iron and copper particles ranging in size from 50 to 125 μm. The testing results have demonstrated that the device is capable of detecting and distinguishing ferrous and nonferrous metal particles in lubrication oil; such particles can be indicative of potential machine faults in rotating and reciprocating machinery.


The Fracture Behavior Of An Al–Mg–Si Alloy During Cyclic Fatigue, Diya Azzam, Craig Menzemer, Tirumalai Srivatsan Oct 2015

The Fracture Behavior Of An Al–Mg–Si Alloy During Cyclic Fatigue, Diya Azzam, Craig Menzemer, Tirumalai Srivatsan

Craig Menzemer

In this paper, is presented and discussed the cyclic fracture behavior of the Al–Mg–Si alloy 6063 that is a candidate used in luminaire light poles. The light poles were subject to fatigue deformation. Test sections were taken from the failed region of the light pole and carefully examined in a scanning electron microscope with the objective of rationalizing the macroscopic fracture mode and intrinsic micromechanisms governing fracture under cyclic loading. The fatigue fracture surface of the alloy revealed distinct regions of early microscopic crack growth, stable crack growth and unstable crack growth and overload. An array of fine striations was …


The Quasi-Static Deformation, Failure, And Fracture Behavior Of Titanium Alloy Gusset Plates Containing Bolt Holes, Therese Hurtuk, Craig Menzemer, Anil Patnaik, Tirumalai Srivatsan, Kannan Manigandan, T. Quick Oct 2015

The Quasi-Static Deformation, Failure, And Fracture Behavior Of Titanium Alloy Gusset Plates Containing Bolt Holes, Therese Hurtuk, Craig Menzemer, Anil Patnaik, Tirumalai Srivatsan, Kannan Manigandan, T. Quick

Craig Menzemer

In this article, the influence of bolt holes, specifically their number and layout on strength, deformation, and final fracture behavior of titanium alloy gusset plates under the influence of an external load is presented and discussed. Several plates having differences in both the number and layout of the bolt holes were precision machined and then deformed under quasi-static loading. The specific influence of number of bolt holes and their layout on maximum load-carrying capability and even fracture load was determined. The conjoint influence of bolt number, bolt layout pattern, nature of loading, contribution from local stress concentration, and intrinsic microstructural …


A Study To Evaluate And Understand The Response Of Aluminum Alloy 2026 Subjected To Tensile Deformation, Daniel Lam, Craig Menzemer, Tirumalai Srivatsan Oct 2015

A Study To Evaluate And Understand The Response Of Aluminum Alloy 2026 Subjected To Tensile Deformation, Daniel Lam, Craig Menzemer, Tirumalai Srivatsan

Craig Menzemer

The strain concentration factors were determined for aluminum alloy 2026 in the T3511 temper using multi-hole structural coupon specimens. Samples of the alloy were evaluated for both the 6.25 mm (0.25 in.) thick and 10 mm (0.4 in.) thick specimens and having widths of 50 mm (2 in.) and 100 mm (4 in.), respectively. For the case of the specimens that were 50 mm in width the mechanical tests were conducted for both the open hole and filled hole conditions and the corresponding strain concentration value was determined. Threaded fasteners having collars were used for the case of the filled …


The Bolt Bearing Response And Tensile Deformation Capacity Of Plates Made From A Titanium Alloy, Nicholas Tinl, Craig Menzemer, Anil Patnaik, Tirumalai Srivatsan Oct 2015

The Bolt Bearing Response And Tensile Deformation Capacity Of Plates Made From A Titanium Alloy, Nicholas Tinl, Craig Menzemer, Anil Patnaik, Tirumalai Srivatsan

Craig Menzemer

In this article, the bearing capacity and elongation characteristics of bolt holes in a titanium alloy (i.e., Ti-6Al-4V) deformed in uniaxial tension is presented and discussed. The specific role played by bolt hole confinement on bearing capacity is highlighted. The nature of final fracture is examined and the intrinsic features present on the fracture surface are rationalized in concurrence with macroscopic mechanical response. The behavior of the candidate alloy (Ti-6Al-4V) is compared with conventionally preferred and chosen candidate materials steel and aluminum alloys. An empirical relationship suitable for purpose of structural design is proposed.


An Investigation And Understanding Of The Mechanical Response Of Palmyrah Timber, Hatim Sobier, Craig Menzemer, Tirumalai Srivatsan Oct 2015

An Investigation And Understanding Of The Mechanical Response Of Palmyrah Timber, Hatim Sobier, Craig Menzemer, Tirumalai Srivatsan

Craig Menzemer

The Palmyrah tree flourishes in tropical areas around South East Asia, and particularly in Sri Lanka. Palmyrah is an important economic resource for the region, and has found use in structural applications for both residential dwellings and commercial buildings. While there is a great deal of local field experience with Palmyrah, the mechanical properties have not been well characterized or understood. In an effort to assist engineers with the design and efficient use of the timber, a study was undertaken to evaluate the mechanical response of Palmyrah and develop estimates of design allowable properties. Properties evaluated include static bending strength, …


Understanding The Mechanical Response Of Built-Up Welded Beams Made From Commercially Pure Titanium And A Titanium Alloy, Anil Patnaik, Narendra Poondla, Craig Menzemer, Tirumalai Srivatsan Oct 2015

Understanding The Mechanical Response Of Built-Up Welded Beams Made From Commercially Pure Titanium And A Titanium Alloy, Anil Patnaik, Narendra Poondla, Craig Menzemer, Tirumalai Srivatsan

Craig Menzemer

During the last two decades, titanium has gradually grown in stature, strength and significance to take on the recognition of being a modern and high performance metal that is noticeably stronger and concurrently lighter than the most widely chosen and used steels in a spectrum of industrial applications. Technological innovations have necessitated reduction of part weight, cost and lead time, including concurrent enhancement of performance of structural parts and components made using titanium and its alloys. This has provided the impetus to develop economically viable structural design methodologies and specifications, while at the same time bringing forth innovative and economically …


A Study Of Fatigue And Fracture Response Of Cantilevered Luminaire Structures Made From Aluminum Alloy 6063, Craig Menzemer, Diya Azzam, Tirumalai Srivatsan Oct 2015

A Study Of Fatigue And Fracture Response Of Cantilevered Luminaire Structures Made From Aluminum Alloy 6063, Craig Menzemer, Diya Azzam, Tirumalai Srivatsan

Craig Menzemer

In the experimental results elegantly and exhaustively elaborated upon in this paper the local stresses, obtained from finite element analysis, was used to develop estimates of the stress intensity factor (SIF). In combination with crack growth data, the fatigue lives of both the through-plate and an integrally stiffened socket connection were estimated using software developed by the U.S. Air Force (and referred to as AFGROW). The fatigue life estimates correlated well with the test results provided the crack growth rate data was obtained under conditions of minimal closure at higher stress ratios (of the order R = 0.7). In an …


Isolating Corrosion Of Steel Plates Coupled With Titanium, Anil Patnaik, X. Shan, M. Adams, T. Srivatsan, Craig Menzemer, Joe Payer Oct 2015

Isolating Corrosion Of Steel Plates Coupled With Titanium, Anil Patnaik, X. Shan, M. Adams, T. Srivatsan, Craig Menzemer, Joe Payer

Craig Menzemer

Over twenty six percent of the bridges in the United States are structurally deficient or functionally obsolete. Corrosion of steel used in structures like bridges and buildings is a problem that has gained increased interest and focused concern. Steel is often the metal that is preferred for use in such applications due to a synergism of ease of availability, acceptable mechanical properties and cost effectiveness. Through the years, titanium has grown in strength, stature and significance to be recognized as an emerging high performance metal that is both stronger and lighter than steel. A distinctive property of titanium and its …


Mechanisms Governing Fatigue, Damage, And Fracture Of Commercially Pure Titanium For Viable Aerospace Applications, Udaykar Bathini, Tirumalai Srivatsan, Anil Patnaik, Craig Menzemer Oct 2015

Mechanisms Governing Fatigue, Damage, And Fracture Of Commercially Pure Titanium For Viable Aerospace Applications, Udaykar Bathini, Tirumalai Srivatsan, Anil Patnaik, Craig Menzemer

Craig Menzemer

In this paper, the cyclic stress amplitude controlled high-cycle fatigue properties and final fracture behavior of commercially pure titanium (Grade 2) are presented and discussed. The material characterization was developed and put forth for selection and use in a spectrum of applications spanning the industries of aerospace, defense, chemical, marine, and commercial products. Test specimens were prepared from the as-received plate stock of the material with the stress axis both parallel (longitudinal) and perpendicular (transverse) to the rolling direction of the plate. The test specimens were cyclically deformed at a constant load ratio of 0.1, at different values of maximum …


Infuence Of Welding And Heat Treatment On Microstructure, Properties And Fracture Behaviour Of A Wrought Aluminium Alloy, Eric Hilty, Craig Menzemer, Kannan Manigandan, Tirumalai Srivatsan Oct 2015

Infuence Of Welding And Heat Treatment On Microstructure, Properties And Fracture Behaviour Of A Wrought Aluminium Alloy, Eric Hilty, Craig Menzemer, Kannan Manigandan, Tirumalai Srivatsan

Craig Menzemer

Welding of aluminium alloy, belonging to the 6XXX series, exerts an adverse influence on its strength. The loss of strength immediately adjacent to the welds can have an influence on overall behaviour of the structure or component. In this study, the technique of gas metal arc welding was used. The filler material used was a silicon-containing aluminium alloy. Subsequent to welding, the alloy (6061-T4) was subjected to post-weld heat treatment (PWHT) at 185°C for 6 h. Both the as-welded and artificially aged extrusions of aluminium alloy 6061 were examined for both microstructural development and resultant influence on mechanical properties. Light …


The Bearing Strength And Fracture Behavior Of Bolted Connections In Two Aluminum Alloys, Nicholas Tinl, Craig Menzemer, Kannan Manigandan, Tirumalai Srivatsan Oct 2015

The Bearing Strength And Fracture Behavior Of Bolted Connections In Two Aluminum Alloys, Nicholas Tinl, Craig Menzemer, Kannan Manigandan, Tirumalai Srivatsan

Craig Menzemer

In this paper, the bearing capacity, taken as a combination of strength, elongation, and failure by fracture characteristics of bolt holes in two aluminum alloys, 5052-H32 and 6061-T6, that were deformed in uniaxial tension is presented and discussed. The specific role played by bolt hole confinement on the bearing capacity of each aluminum alloy is highlighted. An increase in the bearing ratio caused plastic deformation around the holes to gradually increase. For both the chosen aluminum alloys the average bearing ratio at the time of failure of the test sample was found to vary with end distance. The experimentally determined …


Where Do We Stand On The Relationship Between Tau Biomarkers And Mild Cognitive Impairment?, Bryn Martin, Philip Allen Oct 2015

Where Do We Stand On The Relationship Between Tau Biomarkers And Mild Cognitive Impairment?, Bryn Martin, Philip Allen

Philip A Allen

We present an editorial on a recent publication by Amlien et al. [2013] in which diffusion tensor imaging (DTI) was used to quantify longitudinal decreases in fractional anisotropy (FA) and increased radial diffusivity (DR) in patients with mild cognitive impairment (MCI). These longitudinal alterations were found to be greater in MCI patients with high cerebrospinal fluid (CSF) tau levels at baseline and greater than healthy controls. Amlien et al. concluded that tau levels were an important early biomarker for predicting rate of disease progression and outcome. The results of this study are an interesting finding for possible predictive …


Task-Specific And General Cognitive Effects In Chiari Malformation Type I, Philip Allen, James Houston, Joshua Pollock, Christopher Buzzelli, Xuan Li, A. Harrington, Bryn Martin, Francis Loth, Mei-Ching Lien, Jahangir Maleki, Mark Luciano Oct 2015

Task-Specific And General Cognitive Effects In Chiari Malformation Type I, Philip Allen, James Houston, Joshua Pollock, Christopher Buzzelli, Xuan Li, A. Harrington, Bryn Martin, Francis Loth, Mei-Ching Lien, Jahangir Maleki, Mark Luciano

Philip A Allen

Our objective was to use episodic memory and executive function tests to determine whether or not Chiari Malformation Type I (CM) patients experience cognitive dysfunction.


High School Bridge Program: A Multidisciplinary Stem Research Program, Jiang Zhe, Dennis Doverspike, Julie Zhao, Paul Lam, Craig Menzemer Oct 2015

High School Bridge Program: A Multidisciplinary Stem Research Program, Jiang Zhe, Dennis Doverspike, Julie Zhao, Paul Lam, Craig Menzemer

Dennis Doverspike

A Science, Technology, Engineering and Math (STEM) summer Bridge Program was developed for high school students. The program was designed to encourage students to consider choosing an engineering major in college and to explore STEM as a future career. This was accomplished through a 10-week program involving multidisciplinary research activities. The participants in the program included 33 high school students. Among former participants in position to make a choice in terms of attending college, 100% had chosen to continue on in college, and 86% had chosen to major in a STEM area. The results indicated that that the program had …


A Parametric Analysis Of A Reservoir-Extended Porous Slider Bearing With Self-Circulation And Cavitation Effects, Joshus Johnson, Minel Braun, Kevin Kreider, Gerald Young Sep 2015

A Parametric Analysis Of A Reservoir-Extended Porous Slider Bearing With Self-Circulation And Cavitation Effects, Joshus Johnson, Minel Braun, Kevin Kreider, Gerald Young

Gerald W Young

This work considers a porous slider bearing fed by an external contiguous reservoir. The bearing system consists of a lubricating film, a porous medium, and the external reservoir, which runs along the entire length of the porous medium. The Darcy model is used for modeling the flow inside the porous medium. The translational velocity of the reservoir wall and porous medium, together with the convergent-divergent slider lubricating film profile, acts to pump the fluid out of and into the lubricating film and the reservoir, respectively. Cavitation effects are modeled realistically using the switch function and modified equations of the Elrod …


A Parametric Analysis Of A Reservoir-Extended Porous Slider Bearing With Self-Circulation And Cavitation Effects, Joshus Johnson, Minel Braun, Kevin Kreider, Gerald Young Sep 2015

A Parametric Analysis Of A Reservoir-Extended Porous Slider Bearing With Self-Circulation And Cavitation Effects, Joshus Johnson, Minel Braun, Kevin Kreider, Gerald Young

Kevin L. Kreider

This work considers a porous slider bearing fed by an external contiguous reservoir. The bearing system consists of a lubricating film, a porous medium, and the external reservoir, which runs along the entire length of the porous medium. The Darcy model is used for modeling the flow inside the porous medium. The translational velocity of the reservoir wall and porous medium, together with the convergent-divergent slider lubricating film profile, acts to pump the fluid out of and into the lubricating film and the reservoir, respectively. Cavitation effects are modeled realistically using the switch function and modified equations of the Elrod …


Heat Transfer For Turbulent Annular Flow Of High Prandtl Number Fluids, Benjamin Chung, Lindon Thomas, Yi Pang Sep 2015

Heat Transfer For Turbulent Annular Flow Of High Prandtl Number Fluids, Benjamin Chung, Lindon Thomas, Yi Pang

Yi Pang

Heat transfer for high Prandtl number fluids flowing turbulently in a concentric circular tube annulus with prescribed wall heat flux is investigated analytically. This surface rejuvenation-based analysis is restricted to thermally and hydrodynamically fully developed flow with constant properties and negligible viscous dissipation. This formulation leads to predictions for the Nusselt Number that are in basic agreement with predictions obtained on the basis of earlier eddy diffusivity models for Prandtl number range from 30 to 1000 and Reynolds number range from 10,000 to 1,000,000.


An Analysis Of Heat Transfer In A Turbulent Heat Generating Flow With High Prandtl Numbers, Benjamin Chung, Yi Pang Sep 2015

An Analysis Of Heat Transfer In A Turbulent Heat Generating Flow With High Prandtl Numbers, Benjamin Chung, Yi Pang

Yi Pang

Turbulent heat transfer in a circular tube associated with heat generating fluid of high Prandtl number and wall heat flux is investigated analytically. In the present study, a more comprehensive surface renewal type model, the surface rejuvenation model is employed, which accounts for the fact that turbulent eddies do not generally reach the wall itself. Results of the bulk-to-wall temperature difference on the basis of this model are presented graphically in terms of Reynolds number, Prandtl number and the ratio of wall heat flux to internal heat generation for both cases of heating and cooling. Some limiting solutions are compared …