Showing papers by "Ephraim M Sparrow published in 2009"
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TL;DR: In this article, a predictive theory is presented which is capable of providing quantitative results for the heat transfer coefficients in round pipes for the three possible flow regimes: laminar, transitional, and turbulent.
149 citations
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TL;DR: It was found that flow separation occurred for a diffuser expansion angle of 5° for inlet Reynolds numbers less than about 2000, invalidating a prior rule-of-thumb that flowseparation first occurs at a divergence angle of seven degrees.
105 citations
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TL;DR: In this article, a quantitative systematic study based on numerical simulation is performed in which each of eight proposed strategies is evaluated with regard to its capability for producing the same per-exit-port mass outflow.
94 citations
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TL;DR: In this article, the authors investigated the effect of inlet conditions on the downstream behavior of the developing flow in a parallel plate channel by making use of a newly developed model of intermittency, taken together with the RANS equations of momentum conservation, the continuity equation, and the SST turbulence model, and derived practical results.
73 citations
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TL;DR: In this article, three turbulence models for application to the flow in a distribution manifold has been performed by a synergistic combination of numerical simulation and laboratory experiments, and the realizable k-ϵ (REAL) model was found to provide the best representation of the data.
48 citations
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TL;DR: In this paper, a fluid-flow model which automatically determines the flow regime was used to analyze a timewise-periodic pipe flow, and numerical simulation was employed to implement the model.
Abstract: A fluid-flow model which automatically determines the flow regime was used to analyze a timewise-periodic pipe flow. Numerical simulation was employed to implement the model. The range of the instantaneous Reynolds number gave rise to four distinct flow regimes: laminarizing, fully laminar, turbulentizing, and fully turbulent. The period of the imposed harmonic oscillations was varied over a very wide range, and the magnitude of the oscillations was of the same order as that of the steady flow on which the oscillations were superimposed. A large-period limit at which the flow is quasi-steady was identified. The predicted quasi-steady fully developed friction factor for each regime was found to be in excellent agreement with steady-state results applied instantaneously. A metric in the form of the ratio of the turbulence production to turbulence destruction was used to exhibit the turbulence characteristics of each of the four flow regimes. The value of this metric was somewhat different in the laminarizat...
36 citations
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TL;DR: In this article, the authors investigated the geometric shape of the exit ports as a means for tailoring manifold performance and found that the continuous single-slot geometry yielded the most uniform outflow from among those considered.
35 citations
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21 Jan 2009TL;DR: In this paper, the authors propose a 1.1.1-approximation algorithm for the problem of concatenation of 2.0-2.5.0.
Abstract: 1.
28 citations
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TL;DR: In this article, the authors used a bio-heat transfer model to identify the magnitude and location in the tissue of the hot-spot temperature, and then used a tissue-damage integral to identify cell damage and/or necrosis.
23 citations
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TL;DR: In this article, an industry-motivated investigation of the application of turbulence models to external fluid flows has been carried out and five turbulence models, commonly offered in commercially available CFD software (FLUENT® Software, ANSYS® CFX® Software and Star-CD™ Software) were carefully implemented in appropriate numerical simulations of the available experimental data.
Abstract: An industry-motivated investigation of the application of turbulence models to external fluid flows has been carried out. The motivating application is the melt-blowing fiber production process used by 3M in which friction forces exerted by high-speed air jets stretch pliable polymeric fibers. The complex fluid flow is turbulent and unique. The closest traditional fluid flow is the wall jet. In order to achieve results of sufficient accuracy to be used in the design of the production equipment, a necessary prerequisite is the identification of an appropriate turbulence model. To this end, five turbulence models, commonly offered in commercially available CFD software (FLUENT® Software, ANSYS® CFX® Software, and Star-CD™ Software) were carefully implemented in appropriate numerical simulations of the available experimental data. The investigated turbulence representations included several two-equation models and a direct solution of the RANS equation. The experimental data consisted of measured velocity pr...
21 citations
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TL;DR: In this paper, buoyancy-induced flow in a horizontal open-ended cavity has been investigated from three perspectives: assessment of the validity of an existent similarity solution, computational issues relevant to numerical simulation, and obtainment and presentation of results of practical utility.
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27 Mar 2009
TL;DR: Synthesis of Mathematical Models Representing Bioheat Transport, K. Khanafer and K.V. Vafai Numerical Models of Blood Flow Effects in Biological Tissues, James W. Baish and P.S. Ayyaswamy.
Abstract: Synthesis of Mathematical Models Representing Bioheat Transport, K. Khanafer and K. Vafai Numerical Models of Blood Flow Effects in Biological Tissues, James W. Baish, K. Mukundakrishnan, and P.S. Ayyaswamy Numerical Methods for Solving Bioheat Transfer Equations in Complex Situations, J. Liu and Z.-S. Deng Discrete Vasculature (DIVA) Model Simulating the Thermal Impact of Individual Blood Vessels for In Vivo Heat Transfer, B.W. Raaymakers, A.N.T.J. Kotte, and J.J.W. Lagendijk Numerical Bioheat Transfer in Tumor Detection and Treatment, Aili Zhang and Lisa X. Xu Thermal Interactions between Blood and Tissue: Development of a Theoretical Approach in Predicting Body Temperature during Blood Cooling and Rewarming, L. Zhu, T. Schappeler, C. Cordero-Tumangday, and A.J. Rosengart Experimental and Numerical Investigation on Simulating Nanocryosurgery of Target Tissues Embedded with Large Blood Vessels, Z.-S. Deng, J. Liu, J.-F. Yan, Z.-Q. Sun, and Y.-X. Zhou Whole-Body Human Thermal Models, Eugene H. Wissler Computational Infrastructure for the Real-Time Patient-Specific Treatment of Cancer, K.R. Diller, J.T. Oden, C. Bajaj, J.C. Browne, J. Hazle, I. Babuska, J. Bass, L. Bidaut, L. Demkowicz, A. Elliott, Y. Feng, D. Fuentes, S. Goswami, A. Hawkins, S. Khoshnevis, B. Kwon, S. Prudhomme, and R.J. Stafford A Mathematical Model to Predict Tissue Temperatures and Necrosis during Microwave Thermal Ablation of the Prostate, S. Ramadhyani, J.P. Abraham, and E.M. Sparrow
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TL;DR: In this article, the performance characteristics of direct contact devices for the measurement of skin-surface temperature were evaluated in the transient mode and three relevant parameters which contribute significantly to the accuracy of the temperature measurements were identified: the thickness of the foam pad, the thermal conductivity of the pad material, and the contact resistance between the device and the skin surface.
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TL;DR: In this paper, the effect of the area ratio on the degree of uniformity of the flow issuing from a manifold through a discrete set of exit ports was investigated by numerical simulation.
Abstract: Two geometric modalities were investigated to determine their effects on the degree of uniformity of the flow issuing from a manifold through a discrete set of exit ports. The goal of the investigation was to demonstrate how these geometric parameters can be used to achieve a high degree of exit-flow uniformity. The first investigated modality is the area ratio, which compares the total outflow area of all the exit ports with the cross-sectional area of the manifold. The second modality is the extent of pressure loading downstream of the exit ports of the manifold. The investigation was facilitated by numerical simulation for which an appropriate turbulence model was used. Three parameters were varied during the course of the research: (a) the area ratio, (b) the downstream pressure loading characterized by the length-to-diameter ratio of the outflow tubes that are attached to the exit ports, and (c) the Reynolds number. It was found that the area ratio parameter had a marked effect on the uniformity of the outflow from the manifold. Quantitative values of the area ratio corresponding to specified degrees of uniformity (i.e., 2%, 5%, and 10%) were identified. This information can be used as a guideline for manifold design. The imposition of the downstream pressure loading was also demonstrated to have a significant effect on the degree of uniformity, but that effect was not as strong as the effect of the area ratio. The manifold pressure was found to increase from the inlet of the manifold to the downstream end of the manifold. The direction of the jetlike discharge from the exit ports of the manifold into a large collection domain was found to vary along the length of the manifold, with inclined jets emanating from the upstream end and perpendicular jets at the downstream end. Over the range of investigated Reynolds numbers, from 40,000 to 200,000, the degree of uniformity of the mass effusion from the exit ports was found to be unaffected. The results of the numerical simulations were confirmed by experiments.
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TL;DR: A synergistic investigation involving both experiment and numerical simulation was performed in vitro to determine the heat flow from rechargeable neuromodulation systems into surrounding media and found that for both components of MDT, substantially lower rates of heat flow were produced compared with those for ANS and BSC.
Abstract: A synergistic investigation involving both experiment and numerical simulation was performed in vitro to determine the heat flow from rechargeable neuromodulation systems into surrounding media. Each system consists of an implant and an external recharging antenna, and the heat flows of each of these components were determined separately. Three systems, each produced by a different medical device firm, were evaluated. The evaluated products included those from Medtronic Inc. (MDT), ANS (a St. Jude Company), and the Boston Scientific Company (BSC, formerly Advanced Bionics). To ensure statistical significance, three nominally identical samples of each of the three systems were included in the study. Furthermore, for each sample of each system, replicate evaluations were performed for both the implant and the antenna. It was found that for both components of MDT, substantially lower rates of heat flow were produced compared with those for ANS and BSC. With regard to the latter systems, the higher rates of heat flow were not consistently ordered for the implant and for the antenna. In general, replicate data runs for each system and each component were in satisfactory agreement. The different samples of the MDT system showed only minor deviations with regard to heat flow. The deviations among the different samples of both ANS and BSC were larger than those evidenced for MDT.
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01 Jan 2009••
13 Nov 2009TL;DR: Heat transfer associated with the electrical recharging of transcutaneous neuromodulation devices was investigated by a combination of experimentation and numerical simulation.
Abstract: Heat transfer associated with the electrical recharging of transcutaneous neuromodulation devices was investigated by a combination of experimentation and numerical simulation. The investigation was performed for the most commonly used neuromodulation systems. Temperature elevations within perfused tissue were obtained. For one selected device, it is shown that temperature elevations are sufficiently moderate so as not to cause concern of injury.
01 Jan 2009
TL;DR: The magnetic field-driven heat generation in neuromodulation systems consisting of implanted and non-implanted devices is discussed in this paper. But the authors focus on the non-intrusive devices.
Abstract: The magnetic-field-driven heat generation in neuromodulation systems consisting of implanted and
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TL;DR: In this paper, a synergistic approach encompassing numerical simulation and laboratory experimentation is used to identify the optimal geometry for the creation of fine fiber by the melt-blown process, which involves highly complex fluid flow and convective heat transfer.
Abstract: In this article, a synergistic approach encompassing numerical simulation and laboratory experimentation is used to identify the optimal geometry for the creation of fine fiber by the melt-blown process. The problem involves highly complex fluid flow and convective heat transfer. The fine fiber is created by the use of high-velocity, obliquely impinging air jets that stretch a polymer extrudate in the partially fluid state. High-temperature air is used to maintain the fluidity of the polymeric material as it exits the die. Four different geometrical configurations were investigated with regard to their capability of producing high fluid shear and high temperatures in the critical region just downstream of the emergence of the polymer extrudate from the tip of a die. The results of the numerical simulations provided a definitive conclusion about the relative efficacies of the four investigated geometrical configurations. The velocity and temperature profiles of the oblique jets were carefully documented to...