New Steam Tables

International Journal of Fluid Machinery and Systems

2016

By high speed Liquid Droplet Impingement (LDI) on material, fluid systems are seriously damaged, therefore, it is important for the solution of the erosion problem of fluid systems to consider the effect of material in LDI. In this study, by using an in-house fluid/material two-way coupled method which considers reflection and transmission of pressure, stress and velocity on the fluid/material interface, high-speed LDI on wet/dry material surface is simulated. As a result, in the case of LDI on wet surface, maximum equivalent stress are less than those of dry surface due to damping effect of liquid film. Empirical formula of the damping effect function is formulated with the fluid factors of LDI, which are impingement velocity, droplet diameter and thickness of liquid film on material surface.

“…In this study, a value of C c C a =10000 is used. The saturated vapor pressure of water p v is calculated by the empirical formula given by Sugawara [13].…”

Section: Governing Equations In Fluidmentioning

confidence: 99%

Numerical Analysis of Damping Effect of Liquid Film on Material in High Speed Liquid Droplet Impingement

Sasaki

International Journal of Fluid Machinery and Systems

2016

“…The working fluids are considered to be water, vapor, and air, where vapor and air (noncondensable gas) are included in the gas phase. The saturated vapor pressure of water p * v is given by the empirical formula (15) . The surface tension is not considered in the present study.…”

Section: Journal Of Fluid Science and Technologymentioning

confidence: 99%

Numerical Analysis of Nonspherical Bubble Collapse Behavior and Induced Impulsive Pressure during First and Second Collapses near the Wall Boundary

Nohmi

et al. 2011

JFST

Cavitation often involves an abrupt phase change phenomenon. This phenomenon causes cavitation erosion on the material surface. In particular, violent bubble collapse near the material surface causes severe erosion. Numerical simulation is a powerful approach by which to clarify the high-speed, complex bubble collapse behavior near the wall boundary. In the present study, numerical analysis of nonspherical bubble collapse behavior and induced impulsive pressure at several initial standoff distance from the wall boundary is performed using a locally homogeneous model of a gasliquid two-phase medium. The second collapse is confirmed to be more violent than the first collapse, and a circular erosion pattern is predicted owing to a toroidal bubble collapse attached to the wall boundary at a certain standoff distance. The influence of the symmetry breaking of the initial spherical bubble shape on the collapse behavior is investigated, and the asymmetry is found to influence the second bubble collapse, especially the generation of the high impulsive pressure in the central area.

“…In the present study, model constants C e C a and C c C a are set to 1,000 and 1 m −1 (15) . The saturated vapor pressure of water p * v is given by the following empirical formula (16) :…”

Section: Journal Of Fluid Science and Technologymentioning

confidence: 99%

Numerical Prediction of Cavitation Erosion Intensity in Cavitating Flows around a Clark Y 11.7% Hydrofoil

Nohmi

et al. 2010

JFST

A numerical prediction method of cavitation erosion is proposed. In this method, the analysis of bubbles in cavitating flows is performed and the intensity of cavitation erosion is evaluated by the impact pressure induced by spherical bubble collapse. In the present study, two-dimensional cavitating flow around the Clark Y 11.7 % hydrofoil is used to examine the proposed numerical prediction method. The proposed numerical method predicts that the intensities of cavitation erosion in noncavitating, attached cavitating and pseudo-supercavitating flows are far weaker than the intensity of cavitation erosion in a transient cavitating flow, and the intensity in the vicinity of the sheet cavity termination is high. These results correspond well to experimental results, and it is confirmed that systematic erosion characteristics are generally captured by this method. Furthermore, the velocity dependence of cavitation erosion is examined, and it is found that the exponent n in the relation between the intensity I and main flow velocity U in (I ∝ U n in) becomes large when the bubble radius is large and ranges between 4.3 and 7.0 in the present study. According to the bubble dynamics, the ambient pressure and the rate of increases in pressure increase as the main flow velocity, and the maximum internal pressure increase. Therefore, it is thought that smaller bubbles cause cavitation erosion when the main flow velocity is large.