Supersonic gas-particle two-phase flow around a sphere

1990 ◽  
Vol 221 ◽  
pp. 453-483 ◽  
Author(s):  
R. Ishii ◽  
N. Hatta ◽  
Y. Umeda ◽  
M. Yuhi
Keyword(s):  
Flow Field ◽  
Shock Layer ◽  
Cloud Model ◽  
Flow Region ◽  
The Body ◽  
Particle Phase ◽  
Two Phase Flows ◽  
Particle Cloud ◽  
Two Phase ◽  
Loading Ratio

This paper describes supersonic flows of a gas-particle mixture around a sphere. The Euler equations for a gas-phase interacting with a particle one are solved by using a TVD (Total Variation Diminishing) scheme developed by Chakravarthy & Osher, and the particle phase is solved by applying a discrete particle-cloud model. First, steady two-phase flows with a finite loading ratio are simulated. By comparing in detail the dusty results with the dust-free ones, the effects of the presence of particles on the flow field in the shock layer are clarified. Also an attempt to correlate the particle behaviours is made with universal parameters such as the Stokes number and the particle loading ratio. Next, non-steady two-phase flows are treated. Impingement of a large particle-cloud on a shock layer of a dust-free gas in front of a sphere is numerically simulated. The effect of particles rebounded from the sphere is taken into account. It is shown that a temporal reverse flow region of the gas is induced near the body axis in the shock layer, which is responsible for the appearance of the gas flow region where the pressure gradient becomes negative along the body surface. These phenomena are consistent with the previous experimental observations. It will be shown that the present results support a flow model for the particle-induced flow field postulated in connection with ‘heating augmentation’ found in the heat transfer measurement in hypersonic particle erosion environments. The particle behaviour in such flows is so complicated that it is almost impossible to treat the particle phase as an ordinary continuum medium.

Numerical analysis of gas-particle two-phase flows

1989 ◽  
Vol 203 ◽  
pp. 475-515 ◽  
Author(s):  
R. Ishii ◽  
Y. Umeda ◽  
M. Yuhi
Keyword(s):  
Numerical Analysis ◽  
Flow Field ◽  
Gas Phase ◽  
Characteristic Length ◽  
Flow Characteristics ◽  
Jet Flows ◽  
Computational Domain ◽  
Particle Phase ◽  
Two Phase Flows ◽  
Two Phase

This paper is concerned with a numerical analysis of axisymmetric gas-particle two-phase flows. Underexpanded supersonic free-jet flows and supersonic flows around a truncated cylinder of gas-particle mixtures are solved numerically on the super computer Fujitsu VP-400. The gas phase is treated as a continuum medium, and the particle phase is treated partly as a discrete one. The particle cloud is divided into a large number of small clouds. In each cloud, the particles are approximated to have the same velocity and temperature. The particle flow field is obtained by following these individual clouds separately in the whole computational domain. In estimating the momentum and heat transfer rates from the particle phase to the gas phase, the contributions from these clouds are averaged over some volume whose characteristic length is small compared with the characteristic length of the flow field but large compared with that of the clouds. The results so obtained reveal that the flow characteristics of the gas-particle mixtures are widely different from those of the dust-free gas at many points.

Modeling of Particulate Pressure in the Frame of Mesoscopic Eulerian Formalism for Compressible Reactive Dispersed Two-Phase Flows

2006 ◽  
Author(s):  
M. Simoes ◽  
O. Simonin
Keyword(s):  
Stokes Equations ◽  
Flow Region ◽  
Navier Stokes ◽  
Two Phase Flows ◽  
Two Phase ◽  
Specific Flow ◽  
Navier Stokes Equations ◽  
Rocket Motors ◽  
Eulerian Approach ◽  
Liquid Rocket

In space propulsion, compressible reactive dispersed two-phase flows are investigated in order to predict the behavior of solid or liquid rocket motors. In the frame of full Eulerian approach, physical modeling of aerodynamic flows in such motors is performed resolving unsteady compressible Navier-Stokes equations for both phases. However, numerical simulations performed on a simple axisymmetric motor have pointed out a flaw of this basic Eulerian approach. Indeed, the variance of the particle velocity distribution is not accounted for, leading to unrealistic accumulations of particles in some specific flow region. To correct this shortcoming, we have developed an advanced Eulerian model based on a statistical approach in the framework of the Mesoscopic Eulerian Formalism (MEF).

Density Distribution in Stagnation Region of Saffman Equation for Dusty Gas

2002 ◽  
Author(s):  
Kazuhiro Tsuboi
Keyword(s):  
Flow Field ◽  
Particle Density ◽  
Stokes Number ◽  
The Body ◽  
Particle Flow ◽  
Particle Phase ◽  
Primary Interest ◽  
Stagnation Region ◽  
Two Fluid ◽  
Good Agreement

We investigate the behaviour of flow field around an obstacle placed in uniform particle flow based on two-fluid Saffman equation. Particle density in the vicinity of the front stagnation point is, in particular, the primary interest in the present study. In the case of small Stokes number, in which particle impingement does not occur, there exists the exact solution of the flow field of particle phase is obtained. Perturbed solution is also obtained in the reciprocal of Stokes number when Stokes number is large enough. Comparison between numerical results and these solutions shows good agreement and the peak of particle density appears near the threshold of partide impingement to the body surface.

Numerical Simulation of Two-Phase Flow under High Acceleration in SRM with Submerged Nozzle

2013 ◽  
Vol 712-715 ◽  
pp. 1253-1258
Author(s):  
Hai Feng Xue ◽  
Xiong Chen ◽  
Yong Ping Wang ◽  
Ya Zheng
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Particle Phase ◽  
Solid Rocket Motor ◽  
Two Phase ◽  
Submerged Nozzle ◽  
High Acceleration ◽  
Axial Acceleration

The two-dimension axisymmetric and two-phase flow in a full-size solid rocket motor with submerged nozzle under high acceleration condition has been simulated with Euler-Lagrange model. Without acceleration and under high axial acceleration on particle trajectories, the influences of different particle diameters were analyzed. The difference between gas flow field and two-phase flow field is significant. The particle accumulation zone above the inner wall of chamber and nozzle is mainly concentrated in two regions. The axial acceleration will intensify the impaction to the end of the chamber. The accretion of the particle phase diameter will increase the inertia of the particle phase, which may cause the following property worse, and the particles can easily form a highly-concentrated aggregation flow.

scholarly journals Wake attenuation in large Reynolds number dispersed two-phase flows

2008 ◽  
Vol 366 (1873) ◽  
pp. 2177-2190 ◽  
Author(s):  
Frédéric Risso ◽  
Véronique Roig ◽  
Zouhir Amoura ◽  
Guillaume Riboux ◽  
Anne-Marie Billet
Keyword(s):  
Reynolds Number ◽  
Volume Fraction ◽  
Bubble Diameter ◽  
Temporal Variations ◽  
The Body ◽  
Experimental Investigations ◽  
Large Reynolds Number ◽  
Two Phase Flows ◽  
Two Phase ◽  
Multi Body

The dynamics of high Reynolds number-dispersed two-phase flow strongly depends on the wakes generated behind the moving bodies that constitute the dispersed phase. The length of these wakes is considerably reduced compared with those developing behind isolated bodies. In this paper, this wake attenuation is studied from several complementary experimental investigations with the aim of determining how it depends on the body Reynolds number and the volume fraction α . It is first shown that the wakes inside a homogeneous swarm of rising bubbles decay exponentially with a characteristic length that scales as the ratio of the bubble diameter d to the drag coefficient C d , and surprisingly does not depend on α for 10 −2 ≤ α ≤10 −1 . The attenuation of the wakes in a fixed array of spheres randomly distributed in space ( α =2×10 −2 ) is observed to be stronger than that of the wake of an isolated sphere in a turbulent incident flow, but similar to that of bubbles within a homogeneous swarm. It thus appears that the wakes in dispersed two-phase flows are controlled by multi-body interactions, which cause a much faster decay than turbulent fluctuations having the same energy and integral length scale. Decomposition of velocity fluctuations into a contribution related to temporal variations and that associated to the random character of the body positions is proposed as a perspective for studying the mechanisms responsible for multi-body interactions.

Liquid Jet Impingement on a Free Liquid Surface: PIV Study of the Turbulent Bubbly Two-Phase Flow

2010 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Flow Field ◽  
Two Phase Flow ◽  
Jet Impingement ◽  
Flow Region ◽  
Air Entrainment ◽  
Continuous Phase ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Field Characteristics ◽  
Inflow Conditions

The turbulent two-phase flow arising from the normal impingement of a round free-surface water jet on a horizontal air-water interface was experimentally studied. Due to the weakly viscous nature of the flow system under consideration, external perturbations or small variations in jet inflow conditions can lead to drastically different flow field characteristics under seemingly similar test conditions. In the current study, a fully developed turbulent jet, exiting a long pipe, ensured properly characterized inflow conditions. The study considered two jet inflow conditions; one entrained air and created a bubbly two-phase flow field while the other did not. Particle image velocimetry (PIV) was used to characterize the flow field beneath the interface, with and without air entrainment, for various nozzle-to-interface separation distances. Turbulent velocity fields of the continuous-phase and dispersed-phase were simultaneously measured in the developing flow region and presented using Reynolds decomposition into mean and fluctuating components. The mean and RMS velocities of the two-phase flow field were compared with velocity measurements obtained under single-phase conditions.

Research Status of Physical Simulation on LF Furnace Refining Ladle

2014 ◽  
Vol 678 ◽  
pp. 616-619
Author(s):  
Xiao Lei Zhou ◽  
Zhe Shi ◽  
Gui Fang Zhang ◽  
Zhong Ning Du
Keyword(s):  
Flow Field ◽  
Recirculation Zone ◽  
Physical Simulation ◽  
Flow Region ◽  
Phase Region ◽  
Flow Zone ◽  
Two Phase ◽  
Research Status ◽  
Similarity Principle ◽  
Flow Field Measurement

The research status of physical simulation on LF furnace refining ladle is introduced in this paper.Since 1970, the research on the gas-liquid two-phase region has begun. The ladle of blowing argon can be roughly divided into three important flow region has been introduced. Two-phase region, the top horizontal flow zone and recirculation zone exists in the ladle.The establishment of physical model should include similarity principle and flow field measurement technique

On the Numerical Study of Bubbly Flow Created by Ventilated Cavity

2010 ◽  
Vol 29-32 ◽  
pp. 143-148
Author(s):  
Min Xiang ◽  
S.C.P. Cheung ◽  
Ji Yuan Tu ◽  
Wei Hua Zhang ◽  
Yang Fei
Keyword(s):  
Flow Field ◽  
Void Fraction ◽  
Numerical Study ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Flow Region ◽  
Valuable Insight ◽  
Two Phase ◽  
Ventilated Cavity

The aim of the study was to develop a numerical model to reproduce the bubbly flow field created by ventilated cavity which includes three different regions. The model was established based on the Eulerian-Eulerian two-fluid model coupled with a population balance approach which is solved by the Homogeneous Multiple-Size-Group (MUSIG) model to predict bubble size distribution. Base on the model, the simulation was carried out at the experimental condition of Su et al. (1995). Firstly three regions were successfully captured proved by the spatial voidage distribution and streamline shape. Then distributions of void fraction and Sauter mean bubble diameter at various sections below the cavity corresponding to three regions respectively were plotted against experimental data. A close agreement was observed in the void fraction distribution which indicates that qualitative details of the structure of the two-phase flow field below the cavity was successfully produced. The Sauter mean bubble diameter in the pipe flow region was under-predicted for about 10%. In conclusion, the proposed model was validated in predicting the multi-region flow field below the ventilated cavity which will provide a valuable insight in designing and controlling of the two phase systems with the detailed flow field information obtained.

Numerical Analysis of Gas-Particle Two-Phase Subsonic Freejets

1992 ◽  
Vol 114 (3) ◽  
pp. 420-429 ◽  
Author(s):  
N. Hatta ◽  
R. Ishii ◽  
H. Fujimoto
Keyword(s):  
Particle Size ◽  
Numerical Analysis ◽  
Stokes Equations ◽  
Aerodynamic Drag ◽  
Cloud Model ◽  
Navier Stokes ◽  
Particle Phase ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Free Jets

This paper describes a numerical analysis of gas-droplet two-phase subsonic free jets in the axisymmetric system. Thermal coupling through heat transfer to droplets, as well as momentum coupling through aerodynamic drag responsible for droplet motion, is taken into account in the present numerical model. The Navier-Stokes equations for a gas-phase interacting with particle phase are solved by a time-dependent difference technique and the particle-phase is solved by a discrete particle cloud model. The jet flow structures of mixture composed of air and water-droplets with 1 μm, 5 μm, and 30 μm, respectively, in diameter are calculated with a single particle size. Some of significant characteristics for the two-phase subsonic free jets are pointed out, in particular, focusing upon the effect of particle size on the flow structure.

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