### Abstract

Turbulent air flow through subchannels is simulated to obtain characteristic frequency on large scale flow pulsation in square arrayed 6-rod bundles. The turbulent mixing between the subchannels is dominated by the large scale flow pulsation phenomenon. Therefore, it is crucial to understand flow patterns in the subchannels for the design of reliable nuclear reactor elements. Numerical simulation using a CFD code is performed by solving the unsteady equations with large eddy simulation (LES) model. For the numerical simulation, two kinds of grid including two subchannels are created. Models with two different P/D ratios (P/D=1.08, 1.35) are simulated. P/D=1.08 case is our main concern to investigate flows in tight lattice rod buddle. The shortened channel length with periodic boundary condition is employed to reduce the computing time. The geometry of the simulated model is based on the 3-D experimental equipment. The velocity fluctuation data in the stream-wise and cross directions are obtained from the simulated model to find the characteristic frequency. The large scale flow pulsations are explained by time history of velocity, Fast Fourier Transform analysis and cross-correlation analysis. The fluctuation frequency at the center of gap and 20 mm away from that point are obtained. The characteristic frequency is 87.5 Hz through the entire monitoring points. Results demonstrate that the periodic flow pulsations occur with small pitch-to-diameter ratio (P/D=1.08) and the vortices trains are highly synchronized. There is no large scale pulsation in P/D=1.35 case.

Original language | English |
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Title of host publication | ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 |

Pages | 3611-3616 |

Number of pages | 6 |

Edition | PARTS A, B, C, D |

DOIs | |

Publication status | Published - 2011 Dec 1 |

Event | ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 - Hamamatsu, Japan Duration: 2011 Jul 24 → 2011 Jul 29 |

### Publication series

Name | ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 |
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Number | PARTS A, B, C, D |

Volume | 1 |

### Other

Other | ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 |
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Country | Japan |

City | Hamamatsu |

Period | 11/7/24 → 11/7/29 |

### Fingerprint

### All Science Journal Classification (ASJC) codes

- Fluid Flow and Transfer Processes

### Cite this

*ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011*(PARTS A, B, C, D ed., pp. 3611-3616). (ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011; Vol. 1, No. PARTS A, B, C, D). https://doi.org/10.1115/AJK2011-18005

}

*ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011.*PARTS A, B, C, D edn, ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011, no. PARTS A, B, C, D, vol. 1, pp. 3611-3616, ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011, Hamamatsu, Japan, 11/7/24. https://doi.org/10.1115/AJK2011-18005

**Large scale flow pulsation in square arrayed rod bundles.** / Kim, Taehwan; Jung, Hee Yoon; Bae, Ji Yeul; Kim, Kyung Min; Cho, Hyung Hee; Shin, Chang Hwan; In, Wang Kee.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

TY - GEN

T1 - Large scale flow pulsation in square arrayed rod bundles

AU - Kim, Taehwan

AU - Jung, Hee Yoon

AU - Bae, Ji Yeul

AU - Kim, Kyung Min

AU - Cho, Hyung Hee

AU - Shin, Chang Hwan

AU - In, Wang Kee

PY - 2011/12/1

Y1 - 2011/12/1

N2 - Turbulent air flow through subchannels is simulated to obtain characteristic frequency on large scale flow pulsation in square arrayed 6-rod bundles. The turbulent mixing between the subchannels is dominated by the large scale flow pulsation phenomenon. Therefore, it is crucial to understand flow patterns in the subchannels for the design of reliable nuclear reactor elements. Numerical simulation using a CFD code is performed by solving the unsteady equations with large eddy simulation (LES) model. For the numerical simulation, two kinds of grid including two subchannels are created. Models with two different P/D ratios (P/D=1.08, 1.35) are simulated. P/D=1.08 case is our main concern to investigate flows in tight lattice rod buddle. The shortened channel length with periodic boundary condition is employed to reduce the computing time. The geometry of the simulated model is based on the 3-D experimental equipment. The velocity fluctuation data in the stream-wise and cross directions are obtained from the simulated model to find the characteristic frequency. The large scale flow pulsations are explained by time history of velocity, Fast Fourier Transform analysis and cross-correlation analysis. The fluctuation frequency at the center of gap and 20 mm away from that point are obtained. The characteristic frequency is 87.5 Hz through the entire monitoring points. Results demonstrate that the periodic flow pulsations occur with small pitch-to-diameter ratio (P/D=1.08) and the vortices trains are highly synchronized. There is no large scale pulsation in P/D=1.35 case.

AB - Turbulent air flow through subchannels is simulated to obtain characteristic frequency on large scale flow pulsation in square arrayed 6-rod bundles. The turbulent mixing between the subchannels is dominated by the large scale flow pulsation phenomenon. Therefore, it is crucial to understand flow patterns in the subchannels for the design of reliable nuclear reactor elements. Numerical simulation using a CFD code is performed by solving the unsteady equations with large eddy simulation (LES) model. For the numerical simulation, two kinds of grid including two subchannels are created. Models with two different P/D ratios (P/D=1.08, 1.35) are simulated. P/D=1.08 case is our main concern to investigate flows in tight lattice rod buddle. The shortened channel length with periodic boundary condition is employed to reduce the computing time. The geometry of the simulated model is based on the 3-D experimental equipment. The velocity fluctuation data in the stream-wise and cross directions are obtained from the simulated model to find the characteristic frequency. The large scale flow pulsations are explained by time history of velocity, Fast Fourier Transform analysis and cross-correlation analysis. The fluctuation frequency at the center of gap and 20 mm away from that point are obtained. The characteristic frequency is 87.5 Hz through the entire monitoring points. Results demonstrate that the periodic flow pulsations occur with small pitch-to-diameter ratio (P/D=1.08) and the vortices trains are highly synchronized. There is no large scale pulsation in P/D=1.35 case.

UR - http://www.scopus.com/inward/record.url?scp=84881410396&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84881410396&partnerID=8YFLogxK

U2 - 10.1115/AJK2011-18005

DO - 10.1115/AJK2011-18005

M3 - Conference contribution

SN - 9780791844403

T3 - ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011

SP - 3611

EP - 3616

BT - ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011

ER -