Some Experiments With Specific Types of Cavitation on Ship Propellers

1982 ◽  
Vol 104 (1) ◽  
pp. 105-114 ◽  
Author(s):  
G. Kuiper
Keyword(s):  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Cavitation Inception ◽  
Sheet Cavitation ◽  
Bubble Cavitation ◽  
Roughness Elements ◽  
Propeller Blades

The influence of the boundary layer and of the nuclei content of the fluid on cavitation inception is investigated. Two models of ship propellers, displaying sheet cavitation and bubble cavitation respectively, are used. Generation of additional nuclei is obtained by electrolysis. It is shown that nuclei are necessary to create sheet cavitation when the laminar boundary layer separates. When the boundary layer is laminar, however, the absence of sheet cavitation is very persistent and independent of the nuclei content. Application of roughness at the leading edge of the propeller blades generates sheet cavitation independent of the nuclei content. Bubble cavitation is strongly affected by the nuclei content of the water. Roughness at the leading edge can indirectly affect bubble cavitation when nuclei are generated by the roughness elements.

An Exploratory Investigation of Cavitation Inception on the Pressure Side of Propellers

2008 ◽  
Author(s):  
Wim M. van Rees ◽  
Martijn X. van Rijsbergen ◽  
Gert Kuiper ◽  
Tom J. C. van Terwisga
Keyword(s):  
Free Stream ◽  
Leading Edge ◽  
Pressure Side ◽  
Cavitation Inception ◽  
Free Stream Turbulence ◽  
Sheet Cavitation ◽  
Edge Roughness ◽  
Exploratory Investigation ◽  
Cavitation Tunnel ◽  
Propeller Blades

Delayed sheet cavitation inception has occasionally been observed in the MARIN Depressurized Towing Tank (DTT). The problems are specifically related to the pressure side of model ship propellers, and occur despite the application of leading-edge roughness. As a consequence, no cavitation at all or cavitation on parts of the propeller blades is observed, in cases where cavitation in the cavitation tunnel or at full scale is present. In an exploratory investigation, the effect of several parameters that may influence cavitation inception is studied in the DTT. In particular, the influences of Reynolds number, free-stream turbulence and additional gas nuclei are investigated. It is concluded that the presence of sufficient gas nuclei is crucial for sheet cavitation inception, even if leading-edge roughness is applied. With additional nuclei in the propeller inflow, sheet cavitation inception in the DTT is no longer delayed with respect to the cavitation tunnel.

Study on Vortex Generators for Control of Attached Cavitation

2017 ◽  
Author(s):  
Bangxiang Che ◽  
Dazhuan Wu
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Main Flow ◽  
Vortex Generators ◽  
Streamwise Vortices ◽  
Fluid Machinery ◽  
Cavitation Inception ◽  
Sheet Cavitation ◽  
Cavitation Phenomenon

Attached cavitation is a type of common cavitation phenomenon in fluid machinery. It is important to develop methods to control its generation. From the view of cavitation inception, the generation of attached cavitation is greatly influenced by the separated boundary layer upstream of cavitation detachment. In this research, a row of microscopic delta-shaped counter-rotating vortex generators (VGs) was applied on the leading edge of the NACA0015 hydrofoil in order to suppress the boundary layer separation and then suppress the generation of attached cavitation. The application of VGs fixed the position of cavitation inception on hydrofoil thus the sheet cavitation became more stable and the cloud cavity shed from hydrofoil with trim trailing edge more regularly. It was found that cavitation inception always appeared adjacent to VGs due to the low pressure in the corner of streamwise vortices induced by VGs. Hydrofoil with VGs showed an entirely different cavitation morphology on the leading edge. A row of separate microscopic vortex cavitation was induced by the counter-rotating vortices firstly. With the lower the height of VGs, the longer the length of these vortex cavitation due to the weaker interaction between vortices and main flow. Following the vortex cavitation, the attached cavitation was developing, but without typical “finger” structure anymore.

Wing Sections for Hydrofoils—Part 3: Experimental Verifications

1985 ◽  
Vol 29 (01) ◽  
pp. 39-50
Author(s):  
Young T. Shen
Keyword(s):  
High Speed ◽  
Design Theory ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Cavitation Inception ◽  
Sheet Cavitation ◽  
Ship Wakes ◽  
Lifting Surfaces ◽  
Propeller Blades ◽  
Force Data

Lifting surfaces such as hydrofoil wings or propeller blades will encounter periodic variations in angle of attack when operated in waves or in nonuniform ship wakes. Undesirable leading-edge sheet cavitation is a common occurrence on hydrofoils and marine propellers. To effectively avoid or delay leading-edge sheet cavitation it is necessary to develop a lifting surface able to tolerate large variations in angle of attack without cavitation. Based on a profile design theory, a series of hydrofoil sections having large cavitation-free bucket widths was developed and presented in previous papers, Part 1 and Part 2. The present paper provides the experimental verification. Profile YS-920 was selected as representative of the series and was tested in a high-speed water tunnel. The measured cavitation inception characteristics and force data of YS-920 were compared with the theoretical predictions. Additionally, they were compared with the measured cavitation and force data of the widely used NACA 66 (MOD) and NACA 16–309 wing sections to show the advantages of using a newly developed hydrofoil section to delay or avoid cavitation.

Keel Design for Low Viscous Drag

1987 ◽  
Author(s):  
Clifford J. Obara ◽  
C. P. van Dam
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Sweep Angle ◽  
Layer Transition ◽  
Layer Flow

In this paper, foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-Layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydro­dynamic characteristics are very much dependent on location and mode of boundary-Layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is lea ding-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.

Suppression of Sheet Cavitation Inception by Water Discharge Through Slit

1987 ◽  
Vol 109 (1) ◽  
pp. 70-74 ◽  
Author(s):  
Hiroharu Kato ◽  
Hajime Yamaguchi ◽  
Shinzo Okada ◽  
Kohei Kikuchi ◽  
Masaru Miyanaga
Keyword(s):  
Boundary Layer ◽  
Flow Visualization ◽  
Discharge Rate ◽  
Water Discharge ◽  
Cavitation Inception ◽  
Suppression Effect ◽  
Sheet Cavitation ◽  
Effect Of Water

This paper studies experimentally the suppression effect of water discharge on incipient and developed sheet cavitation on a hemispherical headform. The water is discharged tangentially from a slit upstream of a cavitating region into the boundary layer on the headform. Increasing the discharge rate, the length of the sheet cavity becomes shorter and then the cavity is suppressed completely. Flow visualization test shows the generation of wavy motion in the boundary layer which disturbs the separated zone, resulting in disappearance of the sheet cavitation.

Some Experiments on the Reattachment of a Laminar Boundary Layer Separating From a Rearward Facing Step on a Flat Plate Aerofoil

1960 ◽  
Vol 64 (599) ◽  
pp. 668-672 ◽  
Author(s):  
T. W. F. Moore
Keyword(s):  
Boundary Layer ◽  
Liquid Film ◽  
Flat Plate ◽  
Laminar Boundary Layer ◽  
Reverse Flow ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Pressure Measurements ◽  
Flow Vortex

Summary:The results of experiments on the reattachment of a laminar boundary layer, separating from a rearward facing step in a flat plate aerofoil, are correlated with the properties of the short leading edge bubble which forms on thin aerofoils near the stall.The experiments, comprising pressure measurements, Pitot explorations, liquid film and smoke studies, indicate that for all Reynolds numbers above the value given by the Owen-KIanfer criterion the reattachment is turbulent behind a stationary air reverse flow vortex bubble. It is also found that the reattachment is laminar for Reynolds numbers below the critical, which further supports Crabtree's interpretation of the Owen-KIanfer criterion in terms of the condition for the growth of turbulent bursts.

scholarly journals Compressible laminar boundary-layer flows of a dusty gas over a semi-infinite flat plate

1988 ◽  
Vol 186 ◽  
pp. 223-241 ◽  
Author(s):  
B. Y. Wang ◽  
I. I. Glass
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Expansion Method ◽  
Boundary Layer Flows ◽  
Two Phase ◽  
Displacement Thickness ◽  
Slip Region ◽  
Two Phases

The compressible laminar boundary-layer flows of a dilute gas-particle mixture over a semi-infinite flat plate are investigated analytically. The governing equations are presented in a general form where more reasonable relations for the two-phase interaction and the gas viscosity are included. The detailed flow structures of the gas and particle phases are given in three distinct regions: the large-slip region near the leading edge, the moderate-slip region and the small-slip region far downstream. The asymptotic solutions for the two limiting regions are obtained by using a series-expansion method. The finite-difference solutions along the whole length of the plate are obtained by using implicit four-point and six-point schemes. The results from these two methods are compared and very good agreement is achieved. The characteristic quantities of the boundary layer are calculated and the effects on the flow produced by the particles are discussed. It is found that in the case of laminar boundary-layer flows, the skin friction and wall heat-transfer are higher and the displacement thickness is lower than in the pure-gas case alone. The results indicate that the Stokes-interaction relation is reasonable qualitatively but not correct quantitatively and a relevant non-Stokes relation of the interaction between the two phases should be specified when the particle Reynolds number is higher than unity.

Keel Design for Low Viscous Drag

1989 ◽  
Vol 33 (02) ◽  
pp. 145-155
Author(s):  
Clifford J. Obara ◽  
C. P. van Dam
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Sweep Angle ◽  
Layer Transition ◽  
Layer Flow

Foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydrodynamic characteristics are very much dependent on location and mode of boundary-layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is leading-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.

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