Combined Buoyancy and Pressure-Driven Flow Through a Shallow, Horizontal, Circular Vent

1995 ◽  
Vol 117 (3) ◽  
pp. 659-667 ◽  
Author(s):  
L. Y. Cooper
Keyword(s):  
Flow Model ◽  
Flow Coefficient ◽  
Forced Flow ◽  
Exchange Flow ◽  
Bernoulli’S Equation ◽  
Orifice Flow ◽  
Flow Through ◽  
Pressure Driven Flow ◽  
Bidirectional Exchange ◽  
Pressure Driven

Combined buoyancy and pressure-driven (i.e., forced) flow through a horizontal vent is considered where the vent-connected spaces are filled with fluids of different density in an unstable configuration (density of the top is larger than that of the bottom). With zero-to-moderate cross-vent pressure difference, Δp, the instability leads to bidirectional exchange flow between the two spaces, e.g., as in the emptying from the bottom of a liquid-filled can with a single vent opening. For relatively large Δp, the flow through the vent is unidirectional, from the high to the low-pressure space, e.g., as is the case when the can has a large enough second vent at the top. Problems of a commonly used unidirectional orifice vent flow model, with Bernoulli’s equation and a constant flow coefficient, CD are discussed. First, the orifice model does not predict bidirectional flows at zero-to-moderate Δp. Also, when Δp exceeds the critical value, ΔpFL, which defines the onset of unidirectional or “flooding” flow, there is a significant dependence of CD on the relative buoyancy of the upper and lower fluids (i.e., CD is not constant). Analysis of relevant boundary value problems and of available experimental data leads to a mathematical vent flow model, which removes the problems of the orifice flow model. The result is a general algorithm to calculate flow through shallow, horizontal, circular vents under high-Grashof-number conditions.

scholarly journals Rheology and microstructural evolution in pressure-driven flow of a magnetorheological fluid with strong particle–wall interactions

2012 ◽  
Vol 23 (9) ◽  
pp. 969-978 ◽  
Author(s):  
Murat Ocalan ◽  
Gareth H. McKinley
Keyword(s):  
Microfluidic Devices ◽  
Magnetorheological Fluid ◽  
Time Dependent ◽  
Mr Fluid ◽  
Flow Through ◽  
Fluid Particles ◽  
And Performance ◽  
Pressure Driven Flow ◽  
Actuator Design ◽  
Pressure Driven

The interaction between magnetorheological (MR) fluid particles and the walls of the device that retain the field-responsive fluid is critical as this interaction provides the means for coupling the physical device to the field-controllable properties of the fluid. This interaction is often enhanced in actuators by the use of ferromagnetic walls that generate an attractive force on the particles in the field-on state. In this article, the aggregation dynamics of MR fluid particles and the evolution of the microstructure in pressure-driven flow through ferromagnetic channels are studied using custom-fabricated microfluidic devices with ferromagnetic sidewalls. The aggregation of the particles and the time-dependent evolution in the microstructure is studied in rectilinear, expansion and contraction channel geometries. These observations help identify methods for improving MR actuator design and performance.

Pressure-driven radial flow in a Taylor–Couette cell

2010 ◽  
Vol 660 ◽  
pp. 527-537 ◽  
Author(s):  
NILS TILTON ◽  
DENIS MARTINAND ◽  
ERIC SERRE ◽  
RICHARD M. LUEPTOW
Keyword(s):  
Pressure Drop ◽  
Radial Flow ◽  
Outer Cylinder ◽  
Axial Direction ◽  
Generalized Solution ◽  
Transmembrane Pressure ◽  
Flow Through ◽  
Couette Cell ◽  
Pressure Driven Flow ◽  
Pressure Driven

A generalized solution for pressure-driven flow through a permeable rotating inner cylinder in an impermeable concentric outer cylinder, a situation used commercially in rotating filtration, is challenging due to the interdependence between the pressure drop in the axial direction and that across the permeable inner cylinder. Most previous approaches required either an imposed radial velocity at the inner cylinder or radial throughflow with both the inner and outer cylinders being permeable. We provide an analytical solution for rotating Couette–Poiseuille flow with Darcy's law at the inner cylinder by using a small parameter related to the permeability of the inner cylinder. The theory works for suction, injection and even combined suction/injection, when the axial pressure drop in the annulus is such that the transmembrane pressure difference reverses sign along the axial extent of the system. Corresponding numerical simulations for finite-length systems match the theory very well.

Numerical Simulation of Heat Transfer in Mixed Electroosmotic Pressure-Driven Flow in Straight Microchannels

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Amir Shamloo ◽  
Arshia Merdasi ◽  
Parham Vatankhah
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Zeta Potential ◽  
Electric Potential ◽  
Uniform Heat Flux ◽  
Electric Potentials ◽  
Circular Flows ◽  
Flow Through ◽  
Pressure Driven Flow ◽  
Pressure Driven

This paper investigates two-dimensional, time-independent elecroosmotic pressure-driven flow generated by a direct current electric potential with asymmetrical and symmetrical zeta potential distributions along the microchannel walls. Fluid flow through the horizontal microchannel is simulated using a numerical method. Two different cases are proposed to study the effect of electric potential on the flow field. First, negative electric potential is applied on the microchannel walls. In this case, large segments with negative electric potential are initially placed on the first half of the microchannel walls with two different arrangements. Afterward, smaller segments with negative electric potential are placed on the microchannel walls. Next, negative electric potential is replaced by positive electric potential on the microchannel walls in the similar manner. It is shown that applying positive potential on the walls contributes to the localized circular flows within the microchannel. The size of these vortices is also proved to considerably vary with the applied zeta potential magnitude. Finally, the effect of wall zeta potential on heat transfer was studied for all the four types of microchannels by imposing a constant uniform heat flux on the walls. The Nusselt number plots indicate how heat transfer varies along the microchannel walls. The Nusselt number fluctuation can be observed where the positive and negative electric potentials are located.

Combined Natural Convection and Forced Flow Through Small Openings in a Horizontal Partition, With Special Reference to Flows in Multicompartment Enclosures

1989 ◽  
Vol 111 (4) ◽  
pp. 980-987 ◽  
Author(s):  
M. Epstein ◽  
M. A. Kenton
Keyword(s):  
Direct Application ◽  
Forced Flow ◽  
Theoretical Treatment ◽  
Exchange Flow ◽  
Exchange Flows ◽  
Toxic Gases ◽  
Buoyancy Driven Flows ◽  
Single Opening ◽  
Flow Through ◽  
Horizontal Partition

Estimates of the magnitude of buoyancy-driven exchange flows through openings in partitions that separate compartments are needed to assess the movement of toxic gases and smoke through buildings. An experiment using water and brine as a substitute for a light gas moving in a dense gas was designed to measure combined forced and buoyancy-driven exchange flow through a single opening in a horizontal partition. No theoretical treatment exists for this configuration. The same apparatus was used to determine the magnitude of the forced flow required to purge the opening of the oppositely directed buoyant component (i.e., the “flooding” limit). Finally, combined forced and buoyancy-driven flows in a multicompartment enclosure were measured. It has been demonstrated that the combined forced and buoyancy-generated flows in the multicompartment structure can be predicted by a direct application of the results of the study of exchange flow through a single opening.

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