Flow Around Bodies With Attached Open Cavities

O'Neill, J. P.

doi:10.21236/ad0064364

Cited by 3 publications

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“…When the propagating, dynamically growing particle–gas bubble system is captured at early times (see Figure B), it exhibits the characteristic features of supercavitation. − The elongated body along with the complex tail structure and turbulence in the wake is present in the shadowgraph images. Here, the supercavitated particle resides inside the gas bubble (cavity), which lowers the overall skin friction drag .…”

Section: Discussionmentioning

confidence: 99%

“…The typical criterion used for identifying a supercavitating flow is σ < 0.1 . An approximate relationship connecting the cavity length ( L ) and its diameter ( d m ) to cavitation number is given by which has been observed to be nearly independent of the cavitator shape . On the basis of the dimensions shown in Figure B, L = 340 μm and d m = 50 μm.…”

Section: Discussionmentioning

confidence: 99%

“…48 An approximate relationship connecting the cavity length (L) and its diameter (d m ) to cavitation number is given by 49 σ σ σ = + + L d 0.008 (0.066 1.7 ) m (4) which has been observed to be nearly independent of the cavitator shape. 47 On the basis of the dimensions shown in Figure 3B, L = 340 μm and d m = 50 μm. Inserting these values into eq 4 gives σ = 0.06 < 0.1, which indicates a supercavitating flow.…”

Section: ■ Discussionmentioning

confidence: 99%

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Ejection of Metal Particles into Superfluid⁴He by Laser Ablation

et al. 2016

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The dynamics following laser ablation of a metal target immersed in superfluid $^4$He is studied by time-resolved shadowgraph photography. The delayed ejection of hot micrometer-sized particles from the target surface into the liquid was indirectly observed by monitoring the formation and growth of gaseous bubbles around the particles. The experimentally determined particle average velocity distribution appears similar as previously measured in vacuum but exhibits a sharp cutoff at the speed of sound of the liquid. The propagation of the subsonic particles terminates in slightly elongated non-spherical gas bubbles residing near the target whereas faster particles reveal an unusual hydrodynamic response of the liquid. Based on the previously established semi-empirical model developed for macroscopic objects, the ejected transonic particles exhibit supercavitating flow to reduce their hydrodynamic drag. Supersonic particles appear to follow a completely different propagation mechanism as they leave discrete and semi-continuous bubble trails in the liquid. The relatively low number density of the observed non-spherical gas bubbles indicates that only large micron-sized particles are visualized in the experiments. Although the unique properties of superfluid helium allow a detailed characterization of these processes, the developed technique can be used to study the hydrodynamic response of any liquid to fast propagating objects on the micrometer-scale.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: ■ Discussionmentioning

confidence: 99%

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Ejection of Metal Particles into Superfluid⁴He by Laser Ablation

et al. 2016

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Numerical modelling of cavities on axisymmetric bodies at zero and non‐zero angle of attack

Ingber

Hailey

1992

Numerical Methods in Fluids

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SUMMARYThe flow about submerged, fully cavitating axisymmetric bodies at both zero and non-zero angle of attack is considered in this paper. A cavity closure model that relates the point of detachment, the angle that the separating streamline makes with the body and the cavity length is described. The direct boundary element method is used to solve the potential flow problem and to determine the cavity shape. A momentum integral boundary layer solver is included in the formulation so that shear stresses can be incorporated into the drag calculations. The numerical predictions based on the proposed closure model are compared with water tunnel measurements and photographs. KEY WORDS Cavitation flow Cavity closure model Drag on cavitating bodies Boundary element method

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