Impact of orifice geometry on the shape of jets: An in vitro Doppler color flow study

James D. Thomas*, John P. O'Shea, Leonardo Rodriguez, Aleksandar D. Popovic, Tracy Svizerro, Arthur E. Weyman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

To investigate the influence of orifice geometry on the three-dimensional shape of jets, an in vitro Doppler color flow study was performed. Jets were formed by discharging blood through round orifices and through orifices with major/minor axis ratios of 2:1, 3:1 and 5:1. These were repeated with orifice areas of 0.1, 0.3 and 0.5 cm2. For turbulent and laminar jets formed by these orifices, Doppler color Bow images were obtained from two orthogonal scanning planes aligned with the major and minor orifice axes. Jet width was measured at 1 cm intervals from 0 to 5 cm from the orifice and used to calculate jet eccentricity (ratio of major to minor axis widths) and the rate of divergence of the jet walls. Jets were observed to diverge more rapidly along walls aligned with the orifice minor axis rather than along the major axis. This differential spreading led to the development of circular symmetry at a short distance from the orifice. Jet divergence (θ) occurred more rapidly for turbulent jets and for jets formed by larger orifices: θ({ring operator}) = 0.80 + 6.3 · A + 7.0 · T + 0.47 · E-OR (r = 95, p < 0.0001, n = 48), where A is orifice area (cm2); T is 0 for laminar jets, 1 for turbulent jets and E-OR combines orifice eccentricity and scanning orientation, ranging from -5 for 5:1 orifices imaged along the major axis, 0 for circular orifices to 5 for 5:1 orifices imaged along the minor axis. Within the jet, eccentricity decayed approximately exponentially with distance from the orifice, more rapidly for turbulent jets, more slowly for the larger and more eccentric orifices. A nonlinear regression model of jet turbulence and orifice eccentricity and size was able to predict jet eccentricity with r = 0.95. Turbulent jets lost approximately 90% of their eccentricity within three orifice diameters of the jet origin. The cause of this circularization appears to be higher shear rates across the jet minor axis profile than across the major axis, leading to a more rapid lateral spread of momentum along the minor axis. These results demonstrate that the details of orifice geometry are obliterated within the proximal jet and support the use of quantitative techniques that assume axial symmetry.

Original languageEnglish (US)
Pages (from-to)901-908
Number of pages8
JournalJournal of the American College of Cardiology
Volume17
Issue number4
DOIs
StatePublished - Mar 15 1991

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Fingerprint Dive into the research topics of 'Impact of orifice geometry on the shape of jets: An in vitro Doppler color flow study'. Together they form a unique fingerprint.

Cite this