scispace - formally typeset
Search or ask a question

Showing papers by "Ephraim M Sparrow published in 2010"


Journal ArticleDOI
TL;DR: In this paper, a transition model for internal flows which enables the prediction of the change of flow regime from turbulent through intermittent to laminar has been implemented by numerical simulation, and the model was employed to study a flow which is decelerated by passing through a conical diffuser.

45 citations


Journal ArticleDOI
TL;DR: In this article, a synergistic combination of experimentation and numerical simulation was used to investigate the risk of tissue temperature elevations caused by recharging of implantable biomedical implantable batteries through a patient's skin.

19 citations


Journal ArticleDOI
01 Mar 2010-Energy
TL;DR: In this article, the authors compared the energy efficiency of convective air warming and direct contact heat conduction for treating hypothermia in a hospital operating room, and found that the specific properties of individual devices within a category played a larger role with regard to energy efficiency.

14 citations


Journal ArticleDOI
TL;DR: In this paper, a quantitative investigation has been performed to determine whether orbital atherectomy gives rise to cavitation, which was performed in two independent fluid environments: a transparent tube having a diameter similar to that of the superficial femoral artery and a large, fluid-filled, open-topped container.
Abstract: A definitive, quantitative investigation has been performed to determine whether orbital atherectomy gives rise to cavitation. The investigation encompassed a synergistic interaction between in vitro experimentation and numerical simulation. The experimentation was performed in two independent fluid environments: 1) a transparent tube having a diameter similar to that of the superficial femoral artery and 2) a large, fluid-filled, open-topped container. All of the experimental and simulation work was based on the geometric model of the Diamondback 360 atherectomy device (Cardiovascular Systems, Inc., St. Paul, MN). Rotational speeds ranged from 80,000 to 214,000 rpm. The presence or absence of cavitation in the experiments was assessed by means of high-speed photography. The photographic images clearly display the fact that there was no cavitation. Flow visualization revealed the presence of fluid flows driven by pressure gradients created by the geometry of the rotating crown. The numerical simulations encompassed the fluid environments and the operating conditions of the experiments. The key result of the numerical simulation is that the minimum fluid pressure due to the rotational motion was approximately 50 times greater than the saturation vapor pressure of the fluid. Since the onset of cavitation requires that the fluid pressure falls below the saturation vapor pressure, the computational outcome strongly supports the experimental findings.

10 citations



Journal ArticleDOI
TL;DR: In this paper, a case study in which the two methodologies, numerical simulation and in vitro experimentation used in tandem, enabled the evaluation of safety issues related to a heat-generating implant.
Abstract: In the design of medical devices, the use of numerical simulation, either with or without complementary experimentation, may lead to a more competent product. The experimentation in question may either be performed in vitro or in vivo. This paper conveys a case study in which the two methodologies, numerical simulation and in vitro experimentation used in tandem, enabled the evaluation of safety issues related to a heat-generating implant. The numerical simulation was implemented by means of ANSYS finite-element software employed in the transient mode. The experimental work provided information necessary for the execution of the simulation and, therefore, was performed as the first phase of the research. The implant is of the type that is equipped with a short-lived battery that requires intermittent recharging. The recharging is accomplished by means of an antenna that is externally mounted on the skin surface. The antenna is the primary of a transformer, and the implant contains the secondary of the transformer. During the recharging period of the battery, heat is generated in both the antenna and the implant. By the symbiotic use of the experimental results and the numerical simulation, time-dependent temperatures were determined in the tissue that is situated in the neighborhood of the implant and the antenna. These temperatures were evaluated from the standpoint of possible tissue damage.

1 citations


Journal ArticleDOI
TL;DR: In this article, an active enhancement device for natural convection in the interfin spaces of a fin array was presented. But the authors did not consider the effect of the interior walls of adjacent fin and the base surface.