Reverse flow inside a parallel plate channel can be achieved by placing an obstruction at the entry. The present work is carried out to study the influence of (i) splitter plates behind the flat plate obstruction at the front end and (ii) splitter plates placed at the rear end of the channel in tandem with the obstruction at the front. The results show that the splitter plate at the front end has a slight unfavourable effect due to a little reduction in the reverse flow. However, when the splitter plate is placed at the rear end, it interferes with the alternate formation and shedding of vortices near the rear end. This interference depends upon the length of the splitter plate and also on its position relative to the exit of the test channel. The resulting flow field causes an increase in the magnitude of the reverse flow which remains constant over a wide range of splitter plate positions.

E. G. Tulapurkara

Susheel K. Swain

Channel flow

Vortex shedding

REVERSE FLOW

SPLITTER PLATE

Fluid structure interaction

Channel

VORTEX

CHANNELS

Fluid flow

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IIT Madras

Influence of splitter plate on the reverse flow in a channel

Fluid Dynamics Research

Reactivity of [Cp*Mo(CO)3Me], 1 with various chalcogenide ligands such as Li[BH2E3] and Li[BH3EFc] (E = S, Se or Te; Fc = (C5H5-Fe-C5H4)) has been described. Room temperature reaction of 1 with Li[BH2E3] (E = S and Se) yielded metal chalcogenide complexes [Cp*Mo(CO)2(η2-S2CCH3)], 2 and [Cp*Mo(CO)2(η1-SeC2H5)], 3. In compound 2, {Cp*Mo(CO)2} fragment adopts a four-legged piano-stool geometry with a η2-dithioacetate moiety. In contrast, treatment of 1 with Li[BH3(EFc)] (E = S, Se or Te; Fc = C5H5-Fe-C5H4) yielded borate complexes [Cp*Mo(CO)2(μ-H)(μ-EFc)BH2], 4-6 in moderate yields. Compounds 4-6 are too unstable and gradual conversion to [{Cp*Mo(CO)2}2(μ-H)(μ-EFc] (7: E = S; 8: Se) and [{Cp*Mo(CO)2}2(μ-TeFc)2], 9 happened by subsequent release of BH3. All the compounds have been characterized by mass spectrometry, IR, multinuclear NMR spectroscopy and structures were unequivocally established by crystallographic analysis for compounds 2, 3 and 7. © Indian Academy of Sciences.

Fulltext

Journal of Chemical Sciences

Reactivity of [Cp*Mo(CO)3Me] with chalcogenated borohydrides Li[BH2E3] and Li[BH3EFc] (Cp* = (η5-C5Me5); E = S, Se or Te; Fc = (C5H5-Fe-C5H4))

It is known that reverse flow occurs in a channel when there is an obstruction at the entry. However, it has been recently shown that the reverse flow can be realised even without an obstruction. This is achieved when the two sides of the channel have a stagger and are kept at an angle of attack to the free stream. The features of the computed reverse flow agree with the experimental results. The computations show that the pumping mechanism of reverse flow in the present case can be explained by the relatively lower pressure near the entry to the channel and the slightly higher pressure near the exit of the channel. The low pressure region, near the entry to the channel, having staggered walls and kept at an angle of attack, is generated by the flow separation at the leading edge of the bottom wall of the channel. Copyright © 2012 Inderscience Enterprises Ltd.

Progress in Computational Fluid Dynamics

A numerical study on the mechanism of reverse flow in a channel without obstruction at the entry

In this investigation the complex unsteady flow through and around a channel in the presence of an obstruction at the entry is studied by solving directly the unsteady Navier-Stokes equations. Depending on the location of the obstruction, the flow through the channel either reverses its direction, stagnates or continues in the same direction as that of the flow outside but with reduced magnitude. The Reynolds number of 4000 is considered, as experimental results are available for comparison. The computed results are in close agreement with experiments. The computations help with better understanding of the phenomenon of reverse flow and fluid pumping. © 2005 Published by The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.

Reverse flow in channel with obstruction at entry

The occurrence of reverse flow in a channel when an obstruction is placed at the entry is already known. In this article an attempt is made to bring out the mechanism that governs this phenomenon. Flow visualisation and pressure measurements are employed for this purpose. The obstruction at the front end of the channel is essential for triggering the reverse flow. For reverse, stagnant and slow forward flow, sharp changes in presence occur at the two ends of the channel. The resulting flow field gives rise to a delicate balance of pressure along the channel that controls the flow direction and magnitude. It is argued that there is a limitation on the maximum reverse flow achievable.The occurrence of reverse flow in a channel when an obstruction is placed at the entry is already known. In this article an attempt is made to bring out the mechanism that governs this phenomenon. Flow visualization and pressure measurements are employed for this purpose. The obstruction at the front end of the channel is essential for triggering the reverse flow. For reverse, stagnant and slow forward flow, sharp changes in pressure occur at the two ends of the channel. The resulting flow field gives rise to a delicate balance of pressure along the channel that controls the flow direction and magnitude. It is argued that there is a limitation on the maximum reverse flow achievable.

On the mechanism of reverse flow in a channel with an obstruction at the entry

The occurrence of reverse flow in a channel when a bluff body is kept at the entry is already known. In the earlier investigations, attention was focused on the generation of the reverse flow with bluff bodies, such as flat plate and other geometries, having the same width as the channel. The separation of the shear layers from the obstruction at the front end and the interaction of the shear layers at the rear end are mainly responsible for the reverse flow. To gain further insight into the phenomenon, the effects of the width of the obstruction at the front and that of placing another at the rear end in tandem with the front one are examined in this study. It is observed that the reverse flow occurs even when the width of the flat plate (b) is less than the channel width (w); the lower limit being b/w=0.6. At this b/w the reverse flow velocity is small, but it increases progressively with b/w until a maximum of about 30% of the forward velocity is attained for b/w≥2.0. However, reverse flow as high as 0.6 times the free-stream velocity is obtained when another plate is kept close to the rear end in addition to the front plate. Further increase in the reverse flow to 0.83 times the free-stream velocity has been achieved by replacing the flat plate model at the rear with a semicircular scoop. © 1994 American Institute of Physics.

Physics of Fluids

Reverse flow in channel-effect of front and rear obstructions

In the present study the flow through and around a parallel walled channel with various obstruction geometries placed at the channel entry is investigated. The flow inside the channel is found to be either stagnant, reverse, or in the forward direction depending upon the position of the obstruction. Experiments were carried out with various obstruction geometries like square, triangular, circular and semi-circular to study the effect of the shape of the geometry on the reverse flow phenomenon. Of the four, the triangular geometry gave the maximum reverse flow. The square and the semi-circular gave almost the same as the flat plate. The maximum forward flow also depends upon the shape of the obstruction geometry. To study the effect of the afterbody length the rectangular shape was chosen and models of different afterbody lengths were investigated. It is seen that the shorter afterbody lengths give a higher reverse flow. The maximum forward flow velocity however is higher for larger afterbody lengths. © 1993 Springer-Verlag.

Experiments in Fluids

Reverse flow in channel-influence of obstruction geometry

Free Shear Layers, Base Pressure and Bluff-Body Drag

AIAA Journal

Effects of splitter plates on the wake flow behind a bluff body

In this study the flow through and around a parallel-walled channel with an obstruction (flat plate) placed at the channel inlet is investigated. Depending on the position of the obstruction, the flow inside the channel is in a direction opposite to that outside, stagnant or in the same direction as outside but with reduced magnitude. Flow visualization in water is used to examine the fluid motion, although some wind tunnel measurements have been made and are also reported. The parameters that have been varied are the gap between the obstruction and the entry to the channel, the length of the channel and the Reynolds number. The maximum value of the reverse flow velocity is found to be about 20 % of that of the flow outside. The maximum forward velocity inside the channel (when it occurs) is only about 65% of the outside velocity even for very large gaps between the obstruction and the channel entrance. A tentative explanation is offered for the observed features. © 1989, Cambridge University Press. All rights reserved.

Journal	Data powered by TypesetFluid Dynamics Research
Publisher	Data powered by TypesetElsevier
ISSN	01695983
Open Access	No