On Cavitation Nuclei in Water Tunnels

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Paper 270

H.- J. Heinke C. Johannsen Ship Model Basin (SVA) Potsdam Hamburg Ship Model Tank (HSVA)

W. Kröger P. Schiller E.-A. Weitendorf University Rostock Hamburg University of Technology Consultant, Hamburg

(TUHH)

Singapore

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The Three Cavitation Tunnels Used

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Time Dependent Nuclei and Oxygen Content with Pressures in Berlin Tunnel K27 without Model

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2D-Profile Cavitation Test in Berlin Tunnel K27

Speed VA = 5.5 m/s and angle of attack (α + α0) = 10°

2D-Profile in Berlin Tunnel K27 at VA = 5.5 m/s, cav-number Ϭ = 2.0 and and angle of attack = 10°

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2D-Profile in tunnels K15A and K27 at VA = 5.5 m/s, cav-number Ϭ = 1.5 and and angle of attack = 10°

SVA Potsdam Tunnel K15A(Small Test Section)

TU Berlin K27(Free Surface Tunnel)

Oxygen Saturation O2 = 58 %Nuclei concentration c =28.0 cm-3

Oxygen Saturation O2 = 34 %Nuclei concentration c =0.15 cm-3

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Time dependentHYKAT and K15Abubble concentrations c(20-230µm) with ship modelfor gassed and degassed02-saturations

Propeller loading KT = 0.29; Cavitation number σn= 2.0

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Propeller loading KT = 0.22; Cavitation number σn= 1.5

Time dependent HYKAT bubble concentrations c(20-230µm) with ship model for gassed and degassed 02-saturations

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Relative suction side cavitation occurrence from 20 revsfor two water qualities

in HYKAT at 10° starboard (left turning propeller)

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Conclusion

Free Surface Tunnel K27 (Berlin): High deaerating capacity

HYKAT (Hamburg): Typical nuclei concentration low → c ≈ 0.75 cm-3 (at 02 ≈ 0.80)

K15A (Potsdam): Higher nuclei concentration → c ≈ 1.0 to 3.0cm-3 (at 02 ≈ 0.60)

Suction side cavity extent of cp prop. in HYKAT (02 ≈ 0.80) and K15A (02 ≈ 0.60)

is about the same *)

Inclusion of O2- and nuclei content in scale effects considerations is difficult

due to water history, as well interaction betw. tunnel pressures and O2- content *) at fully developed cavitation