Journal of the Society of Naval Architects of Korea (대한조선학회논문집)

The Society of Naval Architects of Korea (대한조선학회)
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A Numerical Study of Effects of Body Shape on Cavity and Drag of Underwater Vehicle

몸체 형상이 수중운동체의 공동 발달과 항력특성에 미치는 영향에 대한 수치적 연구

  • Kim, Hyoung-Tae (Department of Naval Architecture & Ocean Engineering, Chungnam National University) ;
  • Kang, Kyung-Tae (Department of Naval Architecture & Ocean Engineering, Chungnam National University) ;
  • Choi, Jung-Kyu (Department of Naval Architecture & Ocean Engineering, Mokpo National University) ;
  • Jung, Young-Rae (Agency for Defense Development) ;
  • Kim, Min-Jae (Agency for Defense Development)
  • Received : 2017.10.23
  • Accepted : 2018.04.12
  • Published : 2018.06.20
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Abstract

The calculation of steady-state cavitating flows around Supercavitating Underwater Bodies (SUB's), which consist of a circular disk head (cavitator), a conical fore-body, a cylindrical middle-body and either a boat-tail or a flare-tail, are carried out. To calculate the axisymmetric cavitating flow, used is a commercial computational fluid dynamics code based on the finite volume method, Fluent. From the analysis of numerical results, the cavity and drag, affected by the fore-body and tail of the SUB's, are investigated. Firstly, the effect of the fore-body shape is investigated with the same disk cavitator and a cylindrical rear-body of fixed diameter. Then with the same cavitator and a fixed fore-body, the effect of the rear-body shape is investigated. Before the cavity generated by the cavitator covers the slant of fore-bodies sufficiently, the larger the cone angle of the fore-body(i.e., the shorter the slant length), the larger the drag and the slower the development of cavity. After the cavity covers the fore-body completely so that the pressure drag component of the body is vanished, the characteristics of drag-velocity curves are identical. Also, as the tail angle is bigger, the cavity generated by the cavitator is suppressed further and the drag becomes larger. The peak of the drag appears for the flare-tail, i.e., when the tail angle is positive(+). On the contrary, the trough of the drag appears for the boat-tail, i.e., when the tail angle is negative(-). When the tail angle is 5 degrees, the peak of the drag appears at the body speed of 80m/s and the value of the drag is 43% larger than that at the design speed of 100m/s. When the tail angle is -5 degrees, the trough of the total drag appears at 75m/s and that drag is 30% smaller than that of the cavitator, which means the rest of the body has a negative drag.

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References

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