scholarly journals Fundamental theory of void fraction of cohesive spheres with logarithmic normal size distribution

2012 ◽  
Vol 120 (1406) ◽  
pp. 417-419 ◽  
Author(s):  
Yutaka AIKAWA ◽  
Michitaka SUZUKI ◽  
Daiki ATARASHI ◽  
Etsuo SAKAI
Keyword(s):  
Size Distribution ◽  
Void Fraction ◽  
Fundamental Theory

Numerical Simulation of Subcooled Flow Boiling Using a Bubble Tracking Method

2016 ◽  
Author(s):  
Tomio Okawa ◽  
Naoki Miyano ◽  
Kazuhiro Kaiho ◽  
Koji Enoki
Keyword(s):  
Numerical Simulation ◽  
Size Distribution ◽  
Void Fraction ◽  
Bubble Size ◽  
Flow Boiling ◽  
Bubble Nucleation ◽  
Bubble Size Distribution ◽  
Subcooled Flow Boiling ◽  
Tracking Method ◽  
Subcooled Flow

The process of bubble nucleation in subcooled flow boiling was visualized using a high speed camera to show that the bubble size can be significantly different between the nucleation sites. However, the bubble size is usually assumed constant in the numerical simulation of subcooled flow boiling. To explore the effect of the bubble size distribution on the void fraction in subcooled flow boiling, numerical simulations were performed using a bubble tracking method in which the size and position of each bubble are calculated individually using a Lagrangian coordinates. In the present simulation, the void fraction was greater when the bubble size distribution was taken into consideration. Since the bubble tracking method requires many correlations, further improvement is necessary. The present numerical results however indicate that the bubble size distribution should be taken in to consideration to evaluate the void fraction in subcooled flow boiling accurately.

Application of a Fiber Optic Probe to High Void Fraction Air/Water Flow

2008 ◽  
Author(s):  
A. J. Pertzborn ◽  
W. C. Smith
Keyword(s):  
Size Distribution ◽  
Water Flow ◽  
Void Fraction ◽  
Droplet Size ◽  
Fiber Optic ◽  
Droplet Size Distribution ◽  
Spray Nozzle ◽  
Fiber Optic Probe ◽  
Flow Measurements ◽  
Optic Probe

Successful development of CFD models for droplet flows is aided by knowledge of the droplet size distribution in the flow, but current instrumentation for measuring droplet size is limited. In an attempt to improve the quality of data collected, fiber optic probe (FOP) technology was investigated. A spray nozzle injected water droplets into an air stream to create a high void fraction droplet flow. Measurements were acquired with the spray nozzle at two different locations upstream of the FOP position. Mean droplet velocity measurements were acquired using laser Doppler velocimetry (LDV) at the FOP position. The droplet size distribution at the probe location was determined by using both the FOP and LDV measurements. The initial results indicate that FOP technology can successfully measure the droplet size distribution in a high void fraction air/water flow and it should be further developed for this application.

Pressure Wave Propagation in a Bubbly Medium: A Multiscale Modelling Approach

2014 ◽  
Author(s):  
Anil Kapahi ◽  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Wave Propagation ◽  
Size Distribution ◽  
Void Fraction ◽  
Bubble Size ◽  
Pressure Wave ◽  
Bubble Size Distribution ◽  
Pressure Amplitude ◽  
Bubbly Medium ◽  
Different Levels ◽  
Modelling Approach

This work uses a compressible Eulerian multi-material solver with three modeling approaches to examine shock and pressure wave propagation in a bubbly medium. These approaches represent different levels of complexity from fully resolving the dispersed bubbles to treating the bubbly medium as a homogeneous mixture. An intermediate approach is based on treating bubbles as discrete singularities. Propagation of the pressure wave through the bubbly medium is compared between the simplified approaches and the fully resolved bubble simulation. Different scenarios demonstrating the effect of pressure amplitude, void fraction, and bubble size distribution are presented to further understand wave propagation in bubbly media.

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