Axial dispersion in pressure perturbed flow through an annular pipe oscillating around its axis |
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Authors: | Suvadip Paul |
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Institution: | (1) Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata, 700 108, India |
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Abstract: | A method of moment is employed to study the axial dispersion of passive tracer molecules released in an unsteady pressure-driven
flow through an annular pipe which is oscillating around its longitudinal axis. The flow unsteadiness is caused by the oscillation
of the tube around its axis as well as by a periodic pressure gradient. A finite difference implicit scheme is adopted to
solve the Aris integral moment equations arising from the unsteady convective-diffusion equation for all time periods. The
main objective is to study the nature of the dispersion coeffcient and mean concentration distribution under the sole as well
as combined oscillation of the two driving forces. The behaviour of the dispersion coeffcient due to the variation of the
aspect ratio, the absorption parameter for purely periodic flow has been examined and the sound response from dispersion coeffcient
is found with the variation of these parameters in the sole presence of pressure pulsation. There is a remarkable difference
in the behavior of the dispersion coeffcient depending on whether the ratio of two frequencies arising from the oscillations
of the tube and the pressure gradient possesses a proper fraction or not. Oscillation of the tube produces much more dispersion
than the pulsation of the pressure gradient and their combined effect leads to a further increase in dispersion. Tube oscillation
shows a stronger effect on the dispersion coeffcient than the pressure pulsation though the effect of physical parameters
are pronounced in the presence of pressure pulsation.
The effect of the frequency parameter on the axial distribution of mean concentration is insensible when the oscillation of
the annular tube is the only forcing. However this effect is much noticeable under the combined action of both forcing and
much more effective under the sole influence of pressure pulsation. |
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Keywords: | " target="_blank"> Axial dispersion finite difference absorption aspect ratio concentration distribution pressure gradient |
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