Control of unsteady partial cavitation and cloud cavitation in marine engineering and hydraulic systems

2020 ◽  
Vol 32 (5) ◽  
pp. 052108 ◽  
Author(s):  
Ebrahim Kadivar ◽  
Mikhail V. Timoshevskiy ◽  
Mikhail Yu. Nichik ◽  
Ould el Moctar ◽  
Thomas E. Schellin ◽  
...  
Keyword(s):  
Hydraulic Systems ◽  
Cloud Cavitation ◽  
Partial Cavitation ◽  
Marine Engineering

scholarly journals Dynamics and Intensity of Erosive Partial Cavitation

2007 ◽  
Vol 129 (7) ◽  
pp. 886-893 ◽  
Author(s):  
Xavier Escaler ◽  
Mohamed Farhat ◽  
Eduard Egusquiza ◽  
François Avellan
Keyword(s):  
Free Stream ◽  
Stream Velocity ◽  
Cloud Cavitation ◽  
Sheet Cavitation ◽  
A Value ◽  
Partial Cavitation ◽  
Cavitation Tunnel ◽  
Shedding Frequency ◽  
Testing Condition ◽  
Collapse Process

An experimental work has been carried out to investigate the dynamic behavior and the intensity of erosive partial cavitation on a 2-D hydrofoil. Both sheet (stable) and cloud (unstable) cavitation have been tested in a cavitation tunnel for various free stream velocities. Special attention has been given to validate the use of acceleration transducers for studying the physical process. In particular, the modulation in amplitude of the cavitation induced vibrations in a high frequency band has allowed us to determine the shedding frequency and the relative intensity of the collapse process for each testing condition. Regarding the cavity dynamics, a typical Strouhal value based on its length of about 0.28 has been found for cloud cavitation; meanwhile, for sheet cavitation, it presents a value of about 0.16. Furthermore, the level of the vibration modulation in the band from 45kHz to 50kHz for cloud cavitation shows a power law dependency on the free stream velocity as well as a good correlation with the pitting rate measured on stainless steel samples mounted on the hydrofoil.

An Experimental Study of Unsteady Partial Cavitation

2004 ◽  
Vol 126 (1) ◽  
pp. 94-101 ◽  
Author(s):  
Jean-Baptiste Leroux ◽  
Jacques Andre´ Astolfi ◽  
Jean Yves Billard
Keyword(s):  
Cavity Length ◽  
Pressure Fluctuations ◽  
Cavity Growth ◽  
Pressure Measurements ◽  
Cloud Cavitation ◽  
Hydraulic Machinery ◽  
Partial Cavitation ◽  
Basic Physics ◽  
Vapor Cloud ◽  
Cavity Closure

Unsteady partial cavitation can cause damage to hydraulic machinery and understanding it requires knowledge of the basic physics involved. This paper presents the main results of a research program based on wall-pressure measurements aimed at studying unsteadiness in partial cavitation. Several features have been pointed out. For cavity lengths that did not exceed half the foil chord the cavity was stated to be stable. At the cavity closure a peak of pressure fluctuations was recorded originating from local cavity unsteadiness in the closure region at a frequency depending on the cavity length. Conversely, cavities larger than half the foil chord were stated to be unstable. They were characterized by a cavity growth/destabilization cycle settled at a frequency lower than the previous ones. During cavity growth, the closure region fluctuated more and pressure fluctuations traveling in the cavity wake were detected. When the cavity was half the foil chord, cavity growth was slowed down and counterbalanced by large vapor cloud shedding. When the cavity length was maximum (l/c∼0.7–0.8), it was strongly destabilized. The reason for such destabilization is discussed at the end of the paper. It is widely believed that the cavity instability originates from a process involving the shedding of vapor clouds during cavity growth, a re-entrant jet, and a shock wave phenomenon due to the collapse of a large cloud cavitation.

Numerical simulation and analysis of condensation shocks in cavitating flow

2018 ◽  
Vol 838 ◽  
pp. 759-813 ◽  
Author(s):  
Bernd Budich ◽  
S. J. Schmidt ◽  
N. A. Adams
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Volume Fraction ◽  
Cavity Growth ◽  
Pressure Rise ◽  
Shock Propagation ◽  
Two Phase ◽  
Cloud Cavitation ◽  
Cavity Collapse ◽  
Partial Cavitation

We analyse unsteady cavity dynamics, cavitation patterns and instability mechanisms governing partial cavitation in the flow past a sharp convergent–divergent wedge. Reproducing a recent reference experiment by numerical simulation, the investigated flow regime is characterised by large-scale cloud cavitation. In agreement with the experiments, we find that cloud shedding is dominated by the periodic occurrence of condensation shocks, propagating through the two-phase medium. The physical model is based on the homogeneous mixture approach, the assumption of thermodynamic equilibrium, and a closed-form barotropic equation of state. Compressibility of water and water vapour is taken into account. We deliberately suppress effects of molecular viscosity, in order to demonstrate that inertial effects dominate the flow evolution. We qualify the flow predictions, and validate the numerical approach by comparison with experiments. In agreement with the experiments, the vapour volume fraction within the partial cavity reaches values ${>}80\,\%$ for its spanwise average. Very good agreement is further obtained for the shedding Strouhal number, the cavity growth and collapse velocities, and for typical coherent flow structures. In accordance with the experiments, the simulations reproduce a condensation shock forming at the trailing part of the partial cavity. It is demonstrated that it satisfies locally Rankine–Hugoniot jump relations. Estimation of the shock propagation Mach number shows that the flow is supersonic. With a magnitude of only a few kPa, the pressure rise across the shock is much lower than for typical cavity collapse events. It is thus far too weak to cause cavitation erosion directly. However, by affecting the dynamics of the cavity, the flow aggressiveness can be significantly altered. Our results indicate that, in addition to classically observed re-entrant jets, condensation shocks feed an intrinsic instability mechanism of partial cavitation.

Early Marine Engineering in the United States

1898 ◽  
Vol 46 (1197supp) ◽  
pp. 19189-19190
Author(s):  
Charles H. Haswell
Keyword(s):  
United States ◽  
The United States ◽  
Marine Engineering

HAYNES Ti-3Al-2.5V

Alloy Digest ◽  
2008 ◽  
Vol 57 (1) ◽  
Keyword(s):  
Stainless Steel ◽  
Physical Properties ◽  
Tensile Properties ◽  
Weight Ratio ◽  
Heat Treating ◽  
Hydraulic Systems ◽  
Seamless Tubing

Abstract Haynes Ti-3Al-2.5V alloy is used where the strength/weight ratio is of prime importance; the alloy is 43% lighter than 21-6-9 stainless steel. It is most often used in the form of seamless tubing for aircraft hydraulic systems. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on forming, heat treating, and joining. Filing Code: TI-145. Producer or source: Haynes International Inc.

MECASTEEL 145

Alloy Digest ◽  
2014 ◽  
Vol 63 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Yield Strength ◽  
Tensile Properties ◽  
High Strength ◽  
Hydraulic Systems ◽  
Minimum Yield

Abstract Mecasteel 145 (minimum yield strength 145 ksi) is a high-strength prehardened steel that can be used in substitution for conventional steels, such as AISI 4330, in the manufacture of massive steel components such as machines, hydraulic systems, and pumps. This datasheet provides information on composition and tensile properties as well as fracture toughness. It also includes information on forming. Filing Code: SA-691. Producer or source: Industeel USA, LLC. Revised as Alloy Digest SA-703, July 2014.

MECASTEEL 90

Alloy Digest ◽  
2014 ◽  
Vol 63 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Yield Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Strength ◽  
Hydraulic Systems ◽  
Aisi 4130 ◽  
Minimum Yield

Abstract Mecasteel 90 (minimum yield strength 90 ksi) is a high-strength prehardened steel that can be used in substitution for conventional steels, such as AISI 4130, in the manufacture of massive steel components such as machines, hydraulic systems, and pumps. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on forming and joining. Filing Code: SA-697. Producer or source: Industeel USA, LLC.

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