Blast-wave propagation in a spray

1978 ◽  
Vol 88 (4) ◽  
pp. 641-657 ◽  
Author(s):  
T. H. Pierce
Keyword(s):  
Gas Phase ◽  
Blast Wave ◽  
Wave Structure ◽  
Blast Waves ◽  
Decay Rates ◽  
Liquid Droplets ◽  
Two Phase ◽  
Number Range ◽  
Reactive Liquid ◽  
Particle Velocities

A first-order analysis is presented for the propagation of a blast wave through a dilute spray of non-reactive liquid droplets that are suspended in a non-reactive gas-phase carrier. The analysis permits straightforward computation of decay rates and internal wave structure for wave strengths in the approximate Mach number range 4 ≤ Ms ≤ 15, and loading factors (mass of spray per unit mass of carrier) less than about 0·4. The droplets must be sufficiently small to completely change phase in a distance behind the shock that is at all times negligible compared with the wave radius. Representative calculations are presented and discussed. These show more rapid decay rates and higher pressures, densities, and particle velocities in two-phase blast waves when compared against equivalent gas-phase blast waves. A simplification of the analysis for the regime of higher wave Mach numbers (strong waves) is also given, which for that case allows direct algebraic calculation of early wave characteristics.

Towards the Understanding of Transformation of Annular to Droplet-Annular Gas-Liquid Flow

2016 ◽  
Author(s):  
Parmod Kumar ◽  
Sushanta K. Mitra ◽  
Arup Kumar Das
Keyword(s):  
Liquid Film ◽  
Gas Phase ◽  
Gaseous Phase ◽  
Annular Flow ◽  
Clear Understanding ◽  
Gravitational Acceleration ◽  
Liquid Droplets ◽  
Two Phase ◽  
Phase Velocities ◽  
Gas Liquid Flow

Annular flow and its deviations due to change of phase velocities in parallel and counter flows are very common in many adiabatic and non-adiabatic applications of two phase flow. The transformation from annular flow to its counterpart droplet-annular flow is often poorly understood as it needs to handle multi scale interfaces experimentally or numerically. In the present work, attempts have been made to capture both wavy annular interface and dynamics of tiny droplets throughout its life cycle using grid based volume of fluid framework. 3-D simulation domain with length (L)/diameter (D) ratio as 6 is considered under the effect of gravitational acceleration and phase inertial field. Wavy interface is observed numerically between the phases using phase fraction contours along with the occurrence of three very interesting phenomena, which include rolling, undercutting and orificing. At low liquid and gas velocities orificing has been observed which restricts the path of gaseous phase. Departure from the orificing phenomenon has been seen at higher gas phase velocities which transforms to other phenomenon called rolling. Rolling is the folding of liquid film by the high velocity gaseous phase towards the radially outward direction. Further, increase in liquid phase velocities above gaseous phase velocities results in undercutting of liquid film by the gas phase. Moreover the liquid droplets can be seen in the entire phenomenon through the gas phase in the core of the tube. We presented a regime map of gas liquid velocities to segregate clear understanding of annular to droplet-annular flow due to orificing, rolling and undercutting. The present study will enrich the knowledge of multiphase flow transportation in process plants, chemical reactors, nuclear reactors and refineries where gas-liquid annular flow is most widely used flow pattern.

Numerical modeling of the influence of bubbles on flow and heat transfer in the descending gas-liquid flow in a pipe

2012 ◽  
Vol 9 (1) ◽  
pp. 131-135
Author(s):  
M.A. Pakhomov
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Liquid Flow ◽  
Bubble Diameter ◽  
Gas Content ◽  
Two Phase ◽  
Eulerian Description ◽  
Flow And Heat Transfer ◽  
Gas Liquid Flow ◽  
The Mathematical Model

The paper presents the results of modeling the dynamics of flow, friction and heat transfer in a descending gas-liquid flow in the pipe. The mathematical model is based on the use of the Eulerian description for both phases. The effect of a change in the degree of dispersion of the gas phase at the input, flow rate, initial liquid temperature and its friction and heat transfer rate in a two-phase flow. Addition of the gas phase causes an increase in heat transfer and friction on the wall, and these effects become more noticeable with increasing gas content and bubble diameter.

Numerical Analysis of Two-Phase Pipe Flow of Liquid Helium Using Multi-Fluid Model

2001 ◽  
Vol 123 (4) ◽  
pp. 811-818 ◽  
Author(s):  
Jun Ishimoto ◽  
Mamoru Oike ◽  
Kenjiro Kamijo
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Liquid Helium ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Numerical Results ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Normal Fluid

The two-dimensional characteristics of the vapor-liquid two-phase flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the two-phase flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the two-phase flow of liquid helium is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained should contribute to the realization of advanced cryogenic industrial applications.

Effect of Pressure on Bubble Growth Within Liquid Droplets at the Superheat Limit

1982 ◽  
Vol 104 (4) ◽  
pp. 750-757 ◽  
Author(s):  
C. T. Avedisian
Keyword(s):  
Vapor Bubble ◽  
Bubble Growth ◽  
High Speed ◽  
Ambient Pressure ◽  
Organic Liquid ◽  
Liquid Droplets ◽  
Growth Data ◽  
Two Phase ◽  
Photographic Evidence ◽  
Good Agreement

A study of high-pressure bubble growth within liquid droplets heated to their limits of superheat is reported. Droplets of an organic liquid (n-octane) were heated in an immiscible nonvolatile field liquid (glycerine) until they began to boil. High-speed cine photography was used for recording the qualitative aspects of boiling intensity and for obtaining some basic bubble growth data which have not been previously reported. The intensity of droplet boiling was found to be strongly dependent on ambient pressure. At atmospheric pressure the droplets boiled in a comparatively violent manner. At higher pressures photographic evidence revealed a two-phase droplet configuration consisting of an expanding vapor bubble beneath which was suspended a pool of the vaporizing liquid. A qualitative theory for growth of the two-phase droplet was based on assuming that heat for vaporizing the volatile liquid was transferred across a thin thermal boundary layer surrounding the vapor bubble. Measured droplet radii were found to be in relatively good agreement with predicted radii.

Effect of Particle Residence Time on Particle Dispersion in a Plane Mixing Layer

1993 ◽  
Vol 115 (4) ◽  
pp. 751-759 ◽  
Author(s):  
Tsuneaki Ishima ◽  
Koichi Hishida ◽  
Masanobu Maeda
Keyword(s):  
Gas Phase ◽  
Residence Time ◽  
Time Scale ◽  
Characteristic Time ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Laser Doppler Velocimeter ◽  
Characteristic Time Scale ◽  
Two Phase ◽  
Particle Residence Time

A particle dispersion has been experimentally investigated in a two-dimensional mixing layer with a large relative velocity between particle and gas-phase in order to clarify the effect of particle residence time on particle dispersion. Spherical glass particles 42, 72, and 135 μm in diameter were loaded directly into the origin of the shear layer. Particle number density and the velocities of both particle and gas phase were measured by a laser Doppler velocimeter with modified signal processing for two-phase flow. The results confirmed that the characteristic time scale of the coherent eddy apparently became equivalent to a shorter characteristic time scale due to a less residence time. The particle dispersion coefficients were well correlated to the extended Stokes number defined as the ratio of the particle relaxation time to the substantial eddy characteristic time scale which was evaluated by taking account of the particle residence time.

A Developed Numerical Method for Turbulent Unsteady Fluid Flow in Two-Phase Systems with Moving Interface

2017 ◽  
Vol 14 (06) ◽  
pp. 1750063 ◽  
Author(s):  
A. M. Hegab ◽  
S. A. Gutub ◽  
A. Balabel
Keyword(s):  
Numerical Model ◽  
Gas Phase ◽  
Level Set ◽  
The Body ◽  
Phase System ◽  
Computational Domain ◽  
Two Phase ◽  
Moving Interface ◽  
Level Set Function ◽  
Gas System

This paper presents the development of an accurate and robust numerical modeling of instability of an interface separating two-phase system, such as liquid–gas and/or solid–gas systems. The instability of the interface can be refereed to the buoyancy and capillary effects in liquid–gas system. The governing unsteady Navier–Stokes along with the stress balance and kinematic conditions at the interface are solved separately in each fluid using the finite-volume approach for the liquid–gas system and the Hamilton–Jacobi equation for the solid–gas phase. The developed numerical model represents the surface and the body forces as boundary value conditions on the interface. The adapted approaches enable accurate modeling of fluid flows driven by either body or surface forces. The moving interface is tracked and captured using the level set function that initially defined for both fluids in the computational domain. To asses the developed numerical model and its versatility, a selection of different unsteady test cases including oscillation of a capillary wave, sloshing in a rectangular tank, the broken-dam problem involving different density fluids, simulation of air/water flow, and finally the moving interface between the solid and gas phases of solid rocket propellant combustion were examined. The latter case model allowed for the complete coupling between the gas-phase physics, the condensed-phase physics, and the unsteady nonuniform regression of either liquid or the propellant solid surfaces. The propagation of the unsteady nonplanar regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The computational results demonstrate a remarkable capability of the developed numerical model to predict the dynamical characteristics of the liquid–gas and solid–gas flows, which is of great importance in many civilian and military industrial and engineering applications.

Experimental Determination of Statistical Properties of Two-Phase Turbulent Motion

1960 ◽  
Vol 82 (3) ◽  
pp. 609-621 ◽  
Author(s):  
S. L. Soo ◽  
H. K. Ihrig ◽  
A. F. El Kouh
Keyword(s):  
Gas Phase ◽  
Tracer Diffusion ◽  
Statistical Properties ◽  
Solid Particles ◽  
Turbulent Motion ◽  
Two Phase ◽  
Gaseous State ◽  
Diffusion Technique ◽  
And Diffusion

Experimental methods for the determination of certain statistical properties of turbulent conveyance and diffusion of solid particles in a gaseous state are presented. Methods include a tracer-diffusion technique for the determination of gas-phase turbulent motion and a photo-optical technique for the determination of motion of solid particles. Results are discussed and compared with previous analytical results.

scholarly journals Collisions of Two-Phase Liquid Droplets in a Heated Gas Medium

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1476
Author(s):  
Pavel Tkachenko ◽  
Nikita Shlegel ◽  
Pavel Strizhak
Keyword(s):  
Volume Fraction ◽  
Industrial Applications ◽  
Droplet Breakup ◽  
Liquid Volume ◽  
Liquid Droplets ◽  
Vapor Bubbles ◽  
Two Phase ◽  
Relative Volume Fraction ◽  
Phase Liquid ◽  
Gas Medium

The paper presents the experimental research findings for the integral characteristics of processes developing when two-phase liquid droplets collide in a heated gas medium. The experiments were conducted in a closed heat exchange chamber space filled with air. The gas medium was heated to 400–500 °C by an induction system. In the experiments, the size of initial droplets, their velocities and impact angles were varied in the ranges typical of industrial applications. The main varied parameter was the percentage of vapor (volume of bubbles) in the droplet (up to 90% of the liquid volume). The droplet collision regimes (coalescence, bounce, breakup, disruption), size and number of secondary fragments, as well as the relative volume fraction of vapor bubbles in them were recorded. Differences in the collision regimes and in the distribution of secondary fragments by size were identified. The areas of liquid surface before and after the initial droplet breakup were determined. Conditions were outlined in which vapor bubbles had a significant and, on the contrary, fairly weak effect on the interaction regimes of two-phase droplets.

scholarly journals Feasibility Study on Downhole Gas–Liquid Separator Design and Experiment Based on the Phase Isolation Method

2021 ◽  
Vol 11 (21) ◽  
pp. 10496
Author(s):  
Yuntong Yang ◽  
Zhaoyu Jiang ◽  
Lianfu Han ◽  
Wancun Liu ◽  
Xingbin Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Gas Phase ◽  
Separation Efficiency ◽  
Dynamic Test ◽  
Phase Flow ◽  
Total Flow ◽  
Total Flow Rate ◽  
Two Phase ◽  
Oil Gas ◽  
Liquid Separator

As oil exploitation enters its middle and late stages, formation pressure drops, and crude oil degases. In production profile logging, the presence of the gas phase will affect the initial oil–water two-phase flowmeter’s flow measurement results. In order to eliminate gas-phase interference and reduce measurement costs, we designed a downhole gas–liquid separator (DGLS) suitable for low flow, high water holdup, and high gas holdup. We based it on the phase isolation method. Using a combination of numerical simulation and fluid dynamic measurement experiments, we studied DGLS separation efficiency separately in the two cases of gas–water two-phase flow and oil–gas–water three-phase flow. Comparative analysis of the numerical simulation calculation and dynamic test results showed that: the VOF model constructed based on k−ε the equation is nearly identical to the dynamic test, and can be used to analyze DGLS separation efficiency; the numerical simulation results of the gas–water two-phase flow show that when the total flow rate is below 20 m3/d, the separation efficiency surpasses 90%. The oil–gas–water three-phase’s numerical simulation results show that the oil phase influences separation efficiency. When the total flow rate is 20 m3/d–50 m3/d and gas holdup is low, the DGLS’s separation efficiency can exceed 90%. Our experimental study on fluid dynamics measurement shows that the DGLS’s applicable range is when the gas mass is 0 m3/d~15 m3/d, and the water holdup range is 50%~100%. The research presented in this article can provide a theoretical basis for the development and design of DGLSs.

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