Progress in Modeling Injector Cavitating Flows With a Multi-Fluid Method

2006 ◽  
Author(s):  
De Ming Wang ◽  
David Greif
Keyword(s):  
Bubble Dynamics ◽  
Measurement Data ◽  
Interfacial Area ◽  
Number Density ◽  
Cavitating Flows ◽  
Set Up ◽  
Single Bubble Dynamics ◽  
Bubble Number ◽  
Bubble Number Density ◽  
Constricted Channel

A finite volume, pressure based semi-implicit algorithm is developed for solving a multi-fluid system of any number of phases with strong coupling between the phases in mass, momentum and energy transfer. The mass transfer from liquid to vapor due to cavitation is modeled based on a single bubble dynamics (Rayleigh-Plesset equation). In order to model the vapor phase of variable size distribution, or polydispersion, the transport equations of bubble number density and interfacial area are derived from taking the moments of the PDF equation in phase space. The modeling of the result equations are effected through consideration of breakup and coalescence. The k-zeta-f turbulence model is adopted which is found to be particularly effective for predicting near wall effects on the turbulence level. Validation efforts are presented in which comparison with available measurement data are made for a number of cases including constricted channel flow with sharp inlet (I-channel), with smooth inlet (Y-channel), a flash-boiling cavitation set-up, and an actual injector set-up.

Interfacial Area and Number Density Transport Equations for Modeling Multiphase Flows With Cavitation

2005 ◽  
Author(s):  
De Ming Wang ◽  
Jaehoon Han ◽  
David Greif ◽  
Iztok Zun ◽  
Matjaz Perpar
Keyword(s):  
Cavitation Erosion ◽  
Volume Fraction ◽  
Interfacial Area ◽  
Physical Models ◽  
Number Density ◽  
Cavitating Flows ◽  
Bubble Distribution ◽  
Bubble Breakup ◽  
Bubble Number ◽  
Bubble Number Density

In this paper we report progress toward developing advanced cavitation models with Eulerian multifluid method. The bubble number density and the interfacial area equations are introduced into the general framework of multifluid method for multiphase cavitating flows in order to account for the variable size nature of the bubble distribution. The physical models for bubble breakup and coalescence are based on the work by Ishii group’s work in recent years. Simulation results of a cavitating flow are compared with the corresponding experimental data, which include the bubble size distribution, bubble volume fraction and bubble number density. The ability of predicting bubble distribution characteristics is particularly useful as an input for cavitation erosion analysis.

Velocity Profile Measurements of Two-Phase Flow in Rectangular Channel Using Ultrasonic Time-Domain Correlation Method

2007 ◽  
Author(s):  
Takuya Hayashida ◽  
Hideki Murakawa ◽  
Hiroshige Kikura ◽  
Masanori Aritomi ◽  
Michitsugu Mori
Keyword(s):  
Flow Measurement ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Correlation Method ◽  
Phase Flow ◽  
Number Density ◽  
Two Phase ◽  
Bubble Number ◽  
Bubble Number Density ◽  
Time Domain Correlation

Velocity measurement using ultrasound has attracted much attention in engineering fields and medical science field. Especially, Ultrasonic velocity profile monitor (UVP) has been in the spotlight in engineering fields, because of its many diagnostic advantages. The major advantage is that UVP can obtain instantaneous velocity distributions on beam line by measuring Doppler shift frequencies of echo signals. And UVP is applicable to existing pipes, because it is non-contact measurement technique. In recent years, various studies about UVP have been done, and UVP has already been put to practical use in engineering plants. The authors especially focused on two-phase flow measurement using ultrasound. Previously, we developed a way to measure bubbly flow using UVP. By this method, we are able to separate liquid information from bubbles information to some degrees. However, when the bubble number density is low, a problem occurs. Because the effect of liquid information is strong under that condition. From this fact, we applied the ultrasound time domain correlation method (UTDC) to two-phase flow measurement. This method is our original technique to measure the velocity distribution. It is based on the cross-correlation between two consecutive echoes of ultrasonic pulses. With this method, we can separate liquid information from bubble information even when the bubble number density is low, because reflected signals depend on the size of reflectors and frequency of ultrasound. In this study, the authors applied the UTDC to two-phase flow measurements in rectangular channel using a multi-wave ultrasonic transducer (TDX). The multi-wave TDX has two kinds of basic frequencies. One is 2MHz for the velocity of rising bubbles and the other is 8MHz for the liquid velocity. So it enables us to measure the velocity of the liquid and that of bubbles at the same point and time. The 2MHz ultrasonic element of TDX has 10mm diameter and the 8MHz ultrasonic element has 3mm diameter.

scholarly journals Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: bubble number-density estimates

2011 ◽  
Vol 57 (204) ◽  
pp. 629-638 ◽  
Author(s):  
J.M. Fegyveresi ◽  
R.B. Alley ◽  
M.K. Spencer ◽  
J.J. Fitzpatrick ◽  
E.J. Steig ◽  
...  
Keyword(s):  
Late Holocene ◽  
Accumulation Rate ◽  
Ice Core ◽  
Temperature History ◽  
Flow Density ◽  
Number Density ◽  
West Antarctica ◽  
Surface Cooling ◽  
Bubble Number ◽  
Bubble Number Density

AbstractA surface cooling of ∼1.7°C occurred over the ∼two millennia prior to ∼1700 CE at the West Antarctic ice sheet (WAIS) Divide site, based on trends in observed bubble number-density of samples from the WDC06A ice core, and on an independently constructed accumulation-rate history using annual-layer dating corrected for density variations and thinning from ice flow. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. Number-density is conserved in bubbly ice following pore close-off, allowing reconstruction of either paleotemperature or paleo-accumulation rate if the other is known. A quantitative late-Holocene paleoclimate reconstruction is presented for West Antarctica using data obtained from the WAIS Divide WDC06A ice core and a steady-state bubble number-density model. The resultant temperature history agrees closely with independent reconstructions based on stable-isotopic ratios of ice. The ∼1.7°C cooling trend observed is consistent with a decrease in Antarctic summer duration from changing orbital obliquity, although it remains possible that elevation change at the site contributed part of the signal. Accumulation rate and temperature dropped together, broadly consistent with control by saturation vapor pressure.

Measurement and interpretation of bubble number-density evolution through the upper 1200 meters of the SPC14 South Pole Ice Core

2021 ◽  
Author(s):  
John Fegyveresi ◽  
Richard Alley ◽  
Joan Fitzpatrick ◽  
Donald Voigt ◽  
Zoe Courville ◽  
...  
Keyword(s):  
Ice Core ◽  
South Pole ◽  
Number Density ◽  
Density Evolution ◽  
Bubble Number ◽  
Bubble Number Density
Sign in / Sign up

Export Citation Format

Share Document