Title of the Paper: Characteristics of Air Bubble Rising in Low Concentration Polymer Solutions
DOWNLOAD FULL PDF
Authors: Hassan, N. M. S., Khan, M. M. K. and Rasul, M. G.
Abstract: The bubble rise phenomena in different low concentration polymer solutions for higher Reynolds number are
presented in this paper. The main characteristics, namely, the bubble velocity, the bubble trajectory and the drag
relationship are investigated. The experiments were conducted in two different cylindrical columns at various liquid
heights by introducing different bubble volumes (from 0.1mL to 20.0mL) corresponding to each height. The bubble rise
velocity, bubble size and bubble trajectory were measured using a combination of non-intrusive-high speed photographic
method and digital image processing. The parameters that significantly affect the rise of air bubble are identified. The
bubble rise velocity of different volumes and the effect of liquid heights on the bubble rise velocity are analysed and
discussed. The results show that the average bubble rise velocity increases with the increase in bubble volume for
different low concentration polymer solutions and the bubble velocity is not dependant on the size of the test rig. The
results of bubble trajectory for various bubbles are compared and discussed. In trajectory analysis, it is seen that the
smaller bubbles show helical or zigzag motion and larger bubbles follow spiral motion. A new set of data of the drag
coefficient for air bubble for higher Reynolds number are reported and compared with the results of other analytical and
experimental studies available in the literature. The bubble rise characteristics, i.e., bubble velocity, trajectory and drag
coefficient produced acceptable and consistent results.
Keywords: Bubble rise velocity, bubble trajectory, bubble volume, drag co-efficient, Reynolds number, polymer
solution, non-intrusive method
Title of the Paper: A Numerical Study of Natural Convection in a Tilted Cavity with Two
Baffles Attached to its Isothermal Walls
DOWNLOAD FULL PDF
Authors: M. Ghass Emi, M. Pirmohammadi, Gh. A. Sheikhzadeh
Abstract: The purpose of this study is to investigate the effect of inclination angle on flow field and heat
transfer in a differentially heated square cavity with two insulated baffles attached to its isothermal walls. The
isothermal walls are at different temperatures. The walls that make an angle φ with the horizontal are adiabatic.
In our formulation of governing differential equations, mass, momentum and the energy equations are applied
to the cavity and the baffles. To solve the governing differential equations a finite volume code based on
Pantenkar's simpler method is utilized. The results are presented for various Rayleigh number in form of
streamlines, isotherms as well as Nusselt number. It is observed that for all baffle lengths and baffle positions
when ϕ = 90o the Nusselt number is almost minimum. In addition the Nusselt number decreases as baffle
length increases, generally. Finally it is shown that Nusselt number changes with baffles position.
Keywords: Natural Convection, inclined cavity, baffles, Nusselt Number