Mixing driven by transient buoyancy flows. I. Kinematics

2018 ◽  
Vol 30 (5) ◽  
pp. 054104 ◽  
Author(s):  
W. M. B. Duval ◽  
H. Zhong ◽  
C. Batur
Keyword(s):  
Buoyancy Flows

Laser surface treatment dominated by buoyancy flows

1992 ◽  
Vol 71 (4) ◽  
pp. 1972-1975 ◽  
Author(s):  
A. Schüssler ◽  
P. H. Steen ◽  
P. Ehrhard
Keyword(s):  
Surface Treatment ◽  
Laser Surface ◽  
Laser Surface Treatment ◽  
Buoyancy Flows

Nanoparticle Concentration in Buoyancy Flows

2005 ◽  
Author(s):  
A. G. Agwu Nnanna
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Large Volume Fraction ◽  
Thermal Enhancement ◽  
Buoyancy Driven Flows ◽  
Small Volume Fraction ◽  
Buoyancy Flows

The presence of nanoparticles in buoyancy-driven flows affects the thermophysical properties of the fluid and consequently alters the rate of heat transfer. The focus of this paper is to estimate the range of volume fractions that results in maximum thermal enhancement in buoyancy-driven nanofluids. In this study, a two-dimensional rectangular enclosure with isothermal vertical walls and adiabatic horizontal surface is filled with 27nm Al2O3 - H2O nanofluid. The volume fraction is varied between 0 to 12%. Results shows that for small volume fraction, 0.2≤Φ≤2%, the presence of the nanoparticles does not impede the free convective heat transfer, rather it augments the rate of heat transfer. However, for large volume fraction, Φ>2%, the convective heat transfer coefficient declines due to reduction in the Rayleigh number but the rate of thermal diffusion is enhanced.

scholarly journals Engineered and Natural Marine Seep, Bubble-Driven Buoyancy Flows

2009 ◽  
Vol 39 (12) ◽  
pp. 3071-3090 ◽  
Author(s):  
Ira Leifer ◽  
Henrik Jeuthe ◽  
Svein Helge Gjøsund ◽  
Vegar Johansen
Keyword(s):  
Water Column ◽  
Saline Water ◽  
Sea Surface ◽  
Bubble Plume ◽  
Surface Data ◽  
Wide Range ◽  
Buoyancy Flows ◽  
Surrounding Fluid ◽  
Natural Hydrocarbon ◽  
Good Agreement

Abstract Bubble-plume upwelling flows were studied in the marine environment through dye releases into engineered plumes and a natural hydrocarbon seep plume. For engineered plumes, these experiments measured the water column–averaged upwelling flow Vup(zo) from release depth zo to the sea surface, for a wide range of flows Q, and zo. From Vup(zo), the local upwelling flow Vup(z), where z is depth, was calculated and found to vary with Q as Vup(z) ∼ Q0.23 for plumes strong enough to penetrate a shallow, thermally stratified layer, which was in good agreement with published relationships between Vup(z) and Q. These data were used to interpret data collected at a natural marine seep. For the seep, the upwelling flow decelerated toward the sea surface in contrast to the engineered plumes, which accelerated toward the sea surface. Data showed the seep bubble-plume upwelling flow lifted significantly colder and more saline water. The increased density difference between this upwelling fluid and the surrounding fluid most likely caused the deceleration. Midwater-column bubble measurements showed downcurrent detrainment of smaller bubbles from the bubble plume.

Natural Convection in Enclosures

1988 ◽  
Vol 110 (4b) ◽  
pp. 1175-1190 ◽  
Author(s):  
S. Ostrach
Keyword(s):  
Boundary Layer ◽  
Natural Convection ◽  
Driving Force ◽  
Numerical Solutions ◽  
Scaling Analysis ◽  
Interest In Science ◽  
Flow And Transport ◽  
Mathematical Problems ◽  
Buoyancy Flows ◽  
Core Flows

There exists a great diversity of buoyancy flows in enclosures that are of interest in science and technology. These buoyancy flows pose new and challenging physical and mathematical problems. Emphasis is given to the complexities of the phenomena, viz., the coupling of the flow and transport and of the boundary-layer and core flows, the interaction between the flow and the driving force, which alters the regions in which the buoyancy acts, and the occurrence of flow sub-regions (cells and layers). The importance of scaling analysis and experiments to determine flow details are discussed and the essentials of scaling techniques are outlined. The implications of these for numerical methods are presented, and the inadequacies of purely numerical solutions are pointed out. Representative works covering a broad range of problems are discussed.

A singularity in thermal boundary-layer flow on a horizontal surface

1992 ◽  
Vol 242 ◽  
pp. 419-440 ◽  
Author(s):  
P. G. Daniels
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Boundary Layer ◽  
Numerical Solutions ◽  
Rational Numbers ◽  
Velocity Fields ◽  
Boundary Layer Equations ◽  
Layer Flow ◽  
Buoyancy Flows ◽  
Temperature And Velocity Fields

A thermal boundary layer, in which the temperature and velocity fields are coupled by buoyancy, flows along a horizontal, insulated wall. For sufficiently low local Froude number the solution terminates in a singularity with rising skin friction and falling pressure. The structure of the singularity is obtained and the results are compared with numerical solutions of the horizontal boundary-layer equations. A novel feature of the analysis is that the powers of the streamwise coordinate involved in the structure of the singularity do not appear to be simple rational numbers and are determined from the solution of a pair of ordinary differential equations which govern the flow in an inner viscous region close to the wall. Modifications of the theory are noted for cases where either the temperature or a non-zero heat transfer are specified at the wall.

scholarly journals Impact of room airflow interaction on metabolic CO2 exposure

2019 ◽  
Vol 111 ◽  
pp. 02005 ◽  
Author(s):  
Athanasia Keli ◽  
Arsen K. Melikov ◽  
Mariya P. Bivolarova ◽  
Panu Mustakallio
Keyword(s):  
Distribution Patterns ◽  
Vertical Surface ◽  
Air Distribution ◽  
Outdoor Air ◽  
Displacement Ventilation ◽  
Cfd Simulations ◽  
Flow Rates ◽  
Meeting Room ◽  
Chilled Ceiling ◽  
Buoyancy Flows

CFD simulations were performed to investigate occupants’ exposure to metabolic CO2 in a room with mechanical ventilation. A meeting room occupied by six adult people performing sedentary activity was simulated. Five of the six occupants were simulated to exhale air with realistic CO2 content, while one occupant was inhaling, i.e. the exposed occupant. Both exhalation and inhalation were simulated with constant flow rates. Two air distribution patterns were considered, mixing and displacement air distribution, each was combined with chilled ceiling, as summer conditions were simulated. For both air distribution patterns, the influence of solar gain of 200 W, which was simulated as heated vertical surface (window), and the distance between the occupants facing each other were studied. The simulation results revealed the importance of buoyancy flows generated by heated vertical surfaces for the pollution distribution. It was found out that compared to the case without solar heat gain, the presence of solar gain increased the inhaled CO2 level by 26.9 % in the case of displacement ventilation, while it reduced the exposure by 4.5 % when the outdoor air was distributed by mixing ventilation. The distance between the occupants facing each other did not affect considerably the exposure.

Multi-objective-oriented removal of airborne pollutants from a slot-ventilated enclosure subjected to mechanical and multi component buoyancy flows

2018 ◽  
Vol 60 ◽  
pp. 333-353 ◽  
Author(s):  
Dong-Dong Zhang ◽  
Huai-Yu Zhong ◽  
Di Liu ◽  
Fu-Yun Zhao ◽  
Yuguo Li ◽  
...  
Keyword(s):  
Airborne Pollutants ◽  
Multi Objective ◽  
Buoyancy Flows
Sign in / Sign up

Export Citation Format

Share Document