Numerical Study of Induced Condensation upon Mixing Flows of Water-stream Flow in a Tee-Junction Pipe

The fluid dynamic interaction between a uniform free stream flow and the rotation induced flow from a sharp edged body is numerically investigated. A two-dimensional (2D) finite volume based computation is performed in this regard to simulate the laminar fluid flow around a rotating square cylinder in an unconfined medium. Body fitted grid system along with moving boundaries is used to obtain the numerical solution of the incompressible Navier–Stokes equations. The Reynolds number based on the free stream flow is kept in the range 10≤Re≤200 with a dimensionless rotational speed of the cylinder in the range 0≤Ω≤5. At low Re=10, the flow field remains steady irrespective of the rotational speed. For 50≤Re≤200, regular low frequency Kármán vortex shedding (VS) is observed up to a critical rate of rotation (Ωcr). Beyond Ωcr, the global flow shows steady nature, although high frequency oscillations in the aerodynamic coefficients are present. The rotating circular cylinder also shows likewise degeneration of Kármán VS at some critical rotational speed. However, significant differences can be seen at higher rotation. Such fluid dynamic transport around a spinning square in an unconfined free stream flow is reported for the first time.

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Numerical Study of Bubble Breakup in Fractal Tree-Shaped Microchannels

International Journal of Molecular Sciences ◽

10.3390/ijms20215516 ◽

2019 ◽

Vol 20 (21) ◽

pp. 5516

Author(s):

Chengbin Zhang ◽

Xuan Zhang ◽

Qianwen Li ◽

Liangyu Wu

Keyword(s):

Stream Flow ◽

Numerical Study ◽

Flow Direction ◽

Underlying Mechanism ◽

Two Dimensional ◽

Bubble Breakup ◽

Hydrodynamic Behaviors ◽

Different Levels ◽

Inlet Capillary ◽

Insight Into

Hydrodynamic behaviors of bubble stream flow in fractal tree-shaped microchannels is investigated numerically based on a two-dimensional volume of fluid (VOF) method. Bubble breakup is examined in each level of bifurcation and the transition of breakup regimes is discussed in particular. The pressure variations at the center of different levels of bifurcations are analyzed in an effort to gain further insight into the underlying mechanism of bubble breakup affected by multi-levels of bifurcations in tree-shaped microchannel. The results indicate that due to the structure of the fractal tree-shaped microchannel, both lengths of bubbles and local capillary numbers decrease along the microchannel under a constant inlet capillary number. Hence the transition from the obstructed breakup and obstructed-tunnel combined breakup to coalescence breakup is observed when the bubbles are flowing into a higher level of bifurcations. Compared with the breakup of the bubbles in the higher level of bifurcations, the behaviors of bubbles show stronger periodicity in the lower level of bifurcations. Perturbations grow and magnify along the flow direction and the flow field becomes more chaotic at higher level of bifurcations. Besides, the feedback from the unequal downstream pressure to the upstream lower level of bifurcations affects the bubble breakup and enhances the upstream asymmetrical behaviors.

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Numerical Study of Supersonic Mixed Compression Air Intake with an Array of Air Jets

Journal of Fluids Engineering ◽

10.1115/1.4049370 ◽

2020 ◽

Author(s):

Neeraj Kumar Gahlot ◽

N. K. Singh

Keyword(s):

Stream Flow ◽

Numerical Study ◽

Computational Study ◽

Pressure Ratio ◽

Injection Pressure ◽

Flow Distortion ◽

Air Jets ◽

Air Jet ◽

Air Intake ◽

Equal Spacing

Abstract Computational study of flow physics inside the mixed compression air intake has been carried out with and without air jets at design Mach number of 2.2. RANS equations were solved with k-? turbulence model by using commercially available software ANSYS. The scope of this research is to improve the flow field inside the air intake and efficiency of supersonic air intake by implementing air jets on the ramp surface. An array of air jets containing two, four and five air jet holes respectively have been made on the ramp surface perpendicular to the flow with equal spacing between them. The injection pressure through air jet has kept constant for all the cases. Flow Distortion and Total pressure recovery were selected to measure the performance of air intake. All the simulations have been performed at a back-pressure ratio of 6. The results obtained suggest that implementation of proper spacing between air jets can improve the performance of air intake due to the mixing of vortices generated by air jets with free stream flow. It is revealed that an array of air jets containing four holes on ramp surface works best and helps in controlling the shock induced separation.

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Numerical study on oscillation characteristics of large chugging of direct condensation of steam in a Tee junction with flowing sub-cooled water

Progress in Nuclear Energy ◽

10.1016/j.pnucene.2021.103720 ◽

2021 ◽

Vol 135 ◽

pp. 103720

Author(s):

Shuqian Li ◽

Wenwen Han ◽

Tao Lu ◽

Lianyuan Feng ◽

Nana Hou ◽

...

Keyword(s):

Numerical Study ◽

Tee Junction ◽

Oscillation Characteristics ◽

Direct Condensation

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Numerical Study of Near-Bed Turbulence Structures Influence on the Initiation of Saltating Grains Movement

Journal of Hydrology and Hydromechanics ◽

10.2478/johh-2013-0026 ◽

2013 ◽

Vol 61 (3) ◽

pp. 202-207 ◽

Cited By ~ 12

Author(s):

Robert J. Bialik

Keyword(s):

Coherent Structures ◽

Numerical Study ◽

Streamwise Velocity ◽

Field Observations ◽

Strongly Correlated ◽

Relevant Model ◽

Water Stream ◽

Velocity Fluctuations ◽

Turbulence Structures ◽

Special Procedure

Abstract The focus of this paper is on the analysis of the influence of near-bed turbulence structures with the inclusion of existing coherent structures on the entrainment of saltating particles in a water stream from the Lagrangian perspective. The interactions between turbulence structures and initiation of particles movement is the key for better understanding of the physics of sediment transport and particles behaviour. These aims are addressed by use of a 3D relevant model of spherical saltating particles, in which a special procedure has been designed to produce coherent structures. In this method, the spectra of turbulent kinetic energy, consisting of four ranges, are used to generate the time series of turbulent velocities in the streamwise, vertical and transversal directions. Numerical results suggest that the initiation of sediment movement is strongly correlated to positive streamwise velocity fluctuations and as such, supports earlier laboratory experimental and field observations, showing that the sweeps and outward interactions play a crucial role in the initiation of saltating particles’ movement.

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Numerical study on bi-phase coupled stress fluid in the presence of Hafnium and metallic nanoparticles over an inclined plane

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-11-2018-0677 ◽

2019 ◽

Vol 29 (8) ◽

pp. 2854-2869 ◽

Cited By ~ 36

Author(s):

A. Zeeshan ◽

R. Ellahi ◽

F. Mabood ◽

F. Hussain

Keyword(s):

Drag Force ◽

Stream Flow ◽

Metallic Nanoparticles ◽

Free Stream ◽

Numerical Study ◽

Force Coefficient ◽

Content Type ◽

Metallic Particles ◽

First Time ◽

Coupled Stress

Purpose The purpose of this study is to examine the simultaneous effects of Hafnium particles and partially submerged metallic particles for the flow of bi-phase coupled stress fluid over an inclined flat plane. Design/methodology/approach An unflinching free stream flow that stretches far from the surface of the plane with the possibility of containing some partially submerged metallic particles is considered. Innovative model has been proposed and designed using Runge–Kutta–Fehlberg method. Findings The findings show that the drag force resists the couple stress fluid, whereas the Newtonian flow is supported by increasing the velocity. For both types of flows, movement of the particle is retarded gradually against the drag force coefficient. Originality/value To the best of the authors’ knowledge, this model is reported for the first time.

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Auto-suspension of transported sediment; turbidity currents

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1962.0012 ◽

1962 ◽

Vol 265 (1322) ◽

pp. 315-319 ◽

Cited By ~ 134

Keyword(s):

Stream Flow ◽

Suspended Solids ◽

Critical Size ◽

Fine Sediment ◽

Turbidity Currents ◽

Conventional Theory ◽

Mineral Density ◽

Water Stream ◽

Critical Grain Size ◽

Turbulent Water

It has been apparent for some time past that fine sediment material carried in suspension by a turbulent water stream flowing by gravity is apt to behave inconsistently with conventional theory. This demands that the concentration of suspended solids, which being heavier than the fluid tend to fall through it, must always increase downwards towards the bed. In fact, however, the concentrations of fine sediment grades present in rivers are often found to increase upwards instead of downwards. Further, while the discharge or transport rate of the coarser grades is found to be a function of the stream flow, that of the finer grades appears to be unlimited. The critical grain size below which these anomalies occur is usually put at about 50 µ for sediments of natural mineral density. But the factors on which the critical size depends have not previously been looked into. The reason for these anomalies has remained mysterious. Equally mysterious have been the conditions which enable a submarine turbidity current to maintain itself and to transport sand and silt in turbulent suspension for distances of many hundreds of miles over a very gently sloping ocean bed.

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