Etching of metallographic specimens by cavitation
Cavitation damage in water to unalloyed metals and Ni superalloy, using ultrasonic vibratory testing with magnetostrictive transducer
Young, S. G.↗
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A review of NASA research to determine the resistance of materials to cavitation damage in liquid metal environments
Cavitation damage resistance of Fe, Ni and Co alloys in liquid sodium and mercury
Freche, J. C.↗
Cavitating Venturi sump
By ducting spent fluid into a cavitating Venturi sump formed in a main stream of propellant, hazardous working fluid of fluidic systems on board spacecraft or rockets is vented harmlessly.
Mangion, C.↗
Cavitation data for hydraulic equipment
Development of cavitation B-factors for helium, parahydrogen, nitrogen, fluorine, oxygen, refrigerant 114, and water is discussed. B-factor is defined and numerical relationships are established. Mathematical models are included and alternative methods of determining B-factor are explained.
Hord, J.↗
Experimental and predicted cavitation performance of an 80.6 deg helical inducer in high temperature water
The cavitating performance of a stainless steel 80.6 degree flat-plate helical inducer was investigated in water over a range of liquid temperatures and flow coefficients. A semi-empirical prediction method was used to compare predicted values of required net positive suction head in water with experimental values obtained in water. Good agreement was obtained between predicted and experimental data in water. The required net positive suction head in water decreased with increasing temperature and increased with flow coefficient, similar to that observed for a like inducer in liquid hydrogen.
Kovich, G.↗
Cavitation in liquid cryogens. 2: Hydrofoil
Boundary layer principles, along with two-phase concepts, are used to improve existing correlative theory for developed cavity data. Details concerning cavity instrumentation, data analysis, correlative techniques, and experimental and theoretical aspects of a cavitating hydrofoil are given. Both desinent and thermodynamic data, using liquid hydrogen and liquid nitrogen, are reported. The thermodynamic data indicated that stable thermodynamic equilibrium exists throughout the vaporous cryogen cavities. The improved correlative formulas were used to evaluate these data. A new correlating parameter based on consideration of mass limiting two-phase flow flux across the cavity interface, is proposed. This correlating parameter appears attractive for future correlative and predictive applications. Agreement between theory and experiment is discussed, and directions for future analysis are suggested. The front half of the cavities, developed on the hydrofoil, may be considered as parabolically shaped.
Hord, J.↗
Recent theories of cavitation damage including non-symmetrical bubble collapse effects
Theories of cavitation damage mechanisms are discussed. Photographic evidence has shown that the actual collapse of bubbles near a symmetry-destroying feature such as a nearby wall results in a toroidal-like collapse, with the final generation of a liquid microjet oriented toward the wall. Numerical analyses indicate that the shock wave intensity emitted during collapse is not likely to be strong enough to be damaging to most materials. It has been determined that actual damage is usually a result of a combination of impact effect of the microjet and the shock wave pressures generated by bubble rebounds.
Hammitt, F. G.↗
Effect of cavitation on fluid stability in polymer thickened fluids and lubricants
The effects of cavitating flow on the polymeric additives used in functional fluids are described. A comparison of thermal and mechanical stability tests for these polymer solutions show distinct differences in the machanism of the polymer degradation. The thermal degradation tests appear to cause an unzippering or depolymerization type of reaction in which there is no particular selectivity based on molecular weight. The mechanical degradation of these fluids appears to be based on molecular weight. Measurements of molecular weight distributions during mechanical degradation show that for a given level of intensity only molecules above a certain minimum size are degraded. The effects of ultrasonic radiation on polymer degradation are reported. Tests were conducted to demonstrate the mechanism of mechanical polymer degradiation in an orifice. A more severe test than the orifice test in which two tapered roller bearings loaded against each other produce the mechanical breakdown is discussed.
Duda, J. L.↗
Physical effects in cavitating flows
The microscopic and macroscopic aspects of the physical effects of cavitating flows are discussed. The microscopic features are related to the properties of nuclei in liquids and to the moderate tensile strengths which are usually encountered in flows. The macroscopic features are concerned with the growth of vapor or gaseous cavities from a small initial size and with their eventual collapse. Mathematical models are developed to analyze the characteristics of: (1) tensile strength in liquids, (2) growth of vapor bubbles, and (3) collapse of vapor bubbles.
Plesset, M. S.↗
A theoretical investigation of thermodynamic effects on developed cavitation
The results of a theoretical investigation of thermodynamic effects on developed cavitation are presented. An approximate solution to the conservation equations for a two-phase laminar boundary layer is obtained. This analysis produces an expression for the temperature difference between the liquid and vapor phases which can be applied to developed cavity flows. Experimental data of cavity temperature depressions are correlated using this result. In addition, a theoretical estimate of the Nusselt number for the cavity is made using a turbulent boundary layer cavity model proposed by Brennen. The result agrees in part with empirically determined expressions for the cavity Nusselt number.
Weir, D. S.↗
Thermodynamic effects on developed cavitation
The results of an investigation of thermodynamic effects are presented. Distributions of temperature and pressure in a developed cavity were measured for zero- and quarter-caliber ogives. A semiempirical entrainment theory was developed to correlate the measured temperature depression in the cavity. This theory correlates the maximum temperature depression expressed in dimensionless form as the Jakob number in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, and Peclet, and dimensionless cavity length, L/D. The results show that in general, the temperature depression increases with L/D and temperature and the cavitation number based on measured cavity pressure is a function of L/D for a given model contour, independent of the thermodynamic effect.
Holl, J. W.↗
Tabulation and summary of thermodynamic effects data for developed cavitation on ogive-nosed bodies
Thermodynamic effects data for developed cavitation on zero and quarter caliber ogives in Freon 113 and water are tabulated and summarized. These data include temperature depression (delta T), flow coefficient (C sub Q), and various geometrical characteristics of the cavity. For the delta T tests, the free-stream temperature varied from 35 C to 95 C in Freon 113 and from 60 C to 125 C in water for a velocity range of 19.5 m/sec to 36.6 m/sec. Two correlations of the delta T data by the entrainment method are presented. These correlations involve different combinations of the Nusselt, Reynolds, Froude, Weber, and Peclet numbers and dimensionless cavity length.
Holl, J. W.↗
Dynamics of cavitating cascades and inducer pumps
Report chronicles advances in understanding and predicting unsteady dynamic characteristics of cavitating cascades and inducer pumps. It includes bibliography of 19 papers authored between 1972 and 1980.
Brennen, C. E.↗
A numerical method for the dynamics of non-spherical cavitation bubbles
A boundary integral numerical method for the dynamics of nonspherical cavitation bubbles in inviscid incompressible liquids is described. Only surface values of the velocity potential and its first derivatives are involved. The problem of solving the Laplace equation in the entire domain occupied by the liquid is thus avoided. The collapse of a bubble in the vicinity of a solid wall and the collapse of three bubbles with collinear centers are considered.
Lucca, G.↗
Dynamics and mechanism of cavitation erosion on perspex and epoxy resins tested in a rotating disk device
The cavitation erosion behavior including the initiation, dynamics and mechanism of damage process on perspex and epoxy resin specimens tested in a rotating disk device were discussed with respect to exposure time. The inception of erosion always took place at the location nearest to the center of rotation of the disk. Subsequently, as exposure time increased, erosion initiated at other locations as well. Light optical photographs and scanning electron micrographs clearly indicate that most of the material loss appears to occur form the networks of cracks due to their interaction and pits indicate particle debris. The optical degradation (loss of transmittance) on perspex was observed to be more on the rear side than on the front side.
Rao, P. V.↗
Cavitation erosion characteristics of poly(methyl methacrylate) in a rotating disk device
The cavitation erosion behavior including the initiation, dynamics and mechanism of damage process on perspex and epoxy resin specimens tested in a rotating disk device were discussed with respect to exposure time. The inception of erosion always took place at the location nearest to the center of rotation of the disk. Subsequently, as exposure time increased, erosion initiated at other locations as well. Light optical photographs and scanning electron micrographs clearly indicate that most of the material loss appears to occur form the networks of cracks due to their interaction and pits indicate particle debris. The optical degradation (loss of transmittance) on perspex was observed to be more on the rear side than on the front side. Previously announced in STAR as N83-11329
Veerabhadra Rao, P.↗
Size scale effect in cavitation erosion
An overview and data analyses pertaining to cavitation erosion size scale effects are presented. The exponents n in the power law relationship are found to vary from 1.7 to 4.9 for venturi and rotating disk devices supporting the values reported in the literature. Suggestions for future studies were made to arrive at further true scale effects.
Rao, P. V.↗
Empirical relations for cavitation and liquid impingement erosion processes
A unified power-law relationship between average erosion rate and cumulative erosion is presented. Extensive data analyses from venturi, magnetostriction (stationary and oscillating specimens), liquid drop, and jet impact devices appear to conform to this relation. A normalization technique using cavitation and liquid impingement erosion data is also presented to facilitate prediction. Attempts are made to understand the relationship between the coefficients in the power-law relationships and the material properties.
Rao, P. V.↗