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Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
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The Shoulder Wave and Separation Generated by a Surface-Piercing Strut
Pages 346-358

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From page 346...
... INTRODUCTION The flow around a surface piercing body is a very complex phenomenon, involving both viscous effects near the surface of the body, and free surface phenomena, including waves of various forms, formation of liquid sheets, bubble entrainment and three dimensional flow separation. For bodies with a long draft, where the model length is the only significant length scale, data is particularly scarce and includes mostly surface: wave mapping.
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From page 347...
... At Pr,=0.255 the second shoulder wave crest is pushed filer downstream, and at Fr~=0.36 the flow becomes extremely unsteady, violent, and turbulent, without any additional steady crests. However, He front of the bubbly region involves an abrupt change in surface elevation, much like a hydraulic jump.
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From page 348...
... There is some agreement in general trends, especially in the forward side. The discrepancy is mostly evident when energy dissipation due to bow wave breaking, splashing, shoulder wave breaking and flow separation are significant.
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From page 349...
... However, the regions containing bubbles, which are marked on each map, also vary substantially in shape and correspond to He large eddies only in some of He cases. The common phenomena include negative vorticity entrainment at the toe of the wave, and in all but one case the vorticity near the wall is positive.
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From page 350...
... CONCLUSIONS For the present surface piercing model with a long dent a bubbly wake is generated at the trough between the bow and the shoulder wave. This phenomenon occurs at x/I'0.41 and Pr~20.153 due to impingement of the flow on the model, a process associated with energy dissipation in the bow wave.
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From page 351...
... primary orientation of the underwater camera and Me light sheet, and c) orientation of the camera and light sheet dunog observations Mom upstream.
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From page 352...
... x/L~.88. The contour interval is 4; shaded areas indicate negative vorticity, and dashed lines indicate the bour~d~ne~ of the bubbly region.
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From page 355...
... x/L-0.60. The vorticity contour interval is 4; she areas indicate negative vortici~, and dashed lines indicate Me presence of bubbles.
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From page 356...
... xJL=O.91. The contour interval is 8; shaded areas indicate negative voracity and dashed lines indicate the boundaries of the bubbly region.
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From page 357...
... lOc) Figure 10: Video images from a single run at FrL=0.255, at a)
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From page 358...
... schematic of vortex grown in the separated region, d) quantitative axial velocity components in the separated region.
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Key Terms

  • bow wave
  • shoulder wave
  • separated region
  • boundary layer
  • surface piercing

  • flow separation
  • wave crest
  • surface elevation
  • light sheet
  • negative vorticity

  • reverse flow
  • video images
  • flow structure
  • contour interval
  • wave breaking

  • flow near
  • energy dissipation
  • indicate negative
  • velocity components
  • total head

  • naval hydrodynamics
  • lines indicate
  • dashed lines
  • velocity distribution
  • bubbly region

  • bubbly wake
  • total energy
  • bow waves
  • laser sheet
  • entrained bubbles


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