### Abstract

Fully developed intermittent flow in a strongly curved tube was numerically simulated using a numerical scheme based on the SIMPLER method. Physiological pulsatile flow in the aorta was simulated as intermittent flow, with a waveform consisting of a pulse-like systolic flow period followed by a stationary diastolic period. Numerical simulations were carried out for the following conditions: Dean number κ = 393, frequency parameter α = 4-27, curvature ratio δ = 1/2, 1/3 and 1/7, and intermittency parameter η = 0-1/2, where η is the ratio of a systolic time to the cycle period. For α = 18 and 27 the axial-flow profile in a systolic period becomes close to that of a sinusoidally oscillatory flow. At the end of the systole, a region of reversed axial velocity appears in the vicinity of the tube wall, which is caused by the blocking of the flow, similar to blocked flow in a straight tube. This area is enlarged near the inner wall of the bend by the curvature effect. Circumferential flow accelerated in a systole streams into the inner corner and collides at the symmetry line, which creates a jet-like secondary flow towards the outer wall. The region of reversed axial velocity is extended to the tube centre by the secondary flow. The development of the flow continues during the diastolic period for α higher than 8, and the flow does not completely dissipate, so that a residual secondary vortex persists until the next systole. Accordingly, the development of secondary flow in the following systolic phase is strongly affected by the residual vortex at the end of the previous diastolic phase, especially by stationary diastolic periods. Therefore, intermittent flow in a curved tube is strongly affected by the stationary diastolic period. For η = 0 and 1/5, the induced secondary flow in a systole forms additional vortices near the inner wall, whereas for η = 1/3 and 1/2 additional vortices do not appear. The characteristics of intermittent flow in a curved tube are also strongly affected by the length of the diastolic period, which represents a period of zero flow.

Original language | English |
---|---|

Pages (from-to) | 263-287 |

Number of pages | 25 |

Journal | Journal of Fluid Mechanics |

Volume | 347 |

Publication status | Published - 1997 Sep 25 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Computational Mechanics
- Mechanics of Materials
- Physics and Astronomy(all)
- Condensed Matter Physics

### Cite this

*Journal of Fluid Mechanics*,

*347*, 263-287.

**Fully developed intermittent flow in a curved tube.** / Komai, Yutaka; Tanishita, Kazuo.

Research output: Contribution to journal › Article

*Journal of Fluid Mechanics*, vol. 347, pp. 263-287.

}

TY - JOUR

T1 - Fully developed intermittent flow in a curved tube

AU - Komai, Yutaka

AU - Tanishita, Kazuo

PY - 1997/9/25

Y1 - 1997/9/25

N2 - Fully developed intermittent flow in a strongly curved tube was numerically simulated using a numerical scheme based on the SIMPLER method. Physiological pulsatile flow in the aorta was simulated as intermittent flow, with a waveform consisting of a pulse-like systolic flow period followed by a stationary diastolic period. Numerical simulations were carried out for the following conditions: Dean number κ = 393, frequency parameter α = 4-27, curvature ratio δ = 1/2, 1/3 and 1/7, and intermittency parameter η = 0-1/2, where η is the ratio of a systolic time to the cycle period. For α = 18 and 27 the axial-flow profile in a systolic period becomes close to that of a sinusoidally oscillatory flow. At the end of the systole, a region of reversed axial velocity appears in the vicinity of the tube wall, which is caused by the blocking of the flow, similar to blocked flow in a straight tube. This area is enlarged near the inner wall of the bend by the curvature effect. Circumferential flow accelerated in a systole streams into the inner corner and collides at the symmetry line, which creates a jet-like secondary flow towards the outer wall. The region of reversed axial velocity is extended to the tube centre by the secondary flow. The development of the flow continues during the diastolic period for α higher than 8, and the flow does not completely dissipate, so that a residual secondary vortex persists until the next systole. Accordingly, the development of secondary flow in the following systolic phase is strongly affected by the residual vortex at the end of the previous diastolic phase, especially by stationary diastolic periods. Therefore, intermittent flow in a curved tube is strongly affected by the stationary diastolic period. For η = 0 and 1/5, the induced secondary flow in a systole forms additional vortices near the inner wall, whereas for η = 1/3 and 1/2 additional vortices do not appear. The characteristics of intermittent flow in a curved tube are also strongly affected by the length of the diastolic period, which represents a period of zero flow.

AB - Fully developed intermittent flow in a strongly curved tube was numerically simulated using a numerical scheme based on the SIMPLER method. Physiological pulsatile flow in the aorta was simulated as intermittent flow, with a waveform consisting of a pulse-like systolic flow period followed by a stationary diastolic period. Numerical simulations were carried out for the following conditions: Dean number κ = 393, frequency parameter α = 4-27, curvature ratio δ = 1/2, 1/3 and 1/7, and intermittency parameter η = 0-1/2, where η is the ratio of a systolic time to the cycle period. For α = 18 and 27 the axial-flow profile in a systolic period becomes close to that of a sinusoidally oscillatory flow. At the end of the systole, a region of reversed axial velocity appears in the vicinity of the tube wall, which is caused by the blocking of the flow, similar to blocked flow in a straight tube. This area is enlarged near the inner wall of the bend by the curvature effect. Circumferential flow accelerated in a systole streams into the inner corner and collides at the symmetry line, which creates a jet-like secondary flow towards the outer wall. The region of reversed axial velocity is extended to the tube centre by the secondary flow. The development of the flow continues during the diastolic period for α higher than 8, and the flow does not completely dissipate, so that a residual secondary vortex persists until the next systole. Accordingly, the development of secondary flow in the following systolic phase is strongly affected by the residual vortex at the end of the previous diastolic phase, especially by stationary diastolic periods. Therefore, intermittent flow in a curved tube is strongly affected by the stationary diastolic period. For η = 0 and 1/5, the induced secondary flow in a systole forms additional vortices near the inner wall, whereas for η = 1/3 and 1/2 additional vortices do not appear. The characteristics of intermittent flow in a curved tube are also strongly affected by the length of the diastolic period, which represents a period of zero flow.

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M3 - Article

VL - 347

SP - 263

EP - 287

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -