Laminar Swirling Flow in the Entrance Region of a Circular Pipe

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Treated in this paper is the laminar swirling flow in the hydrodynamic entrance region of a circular pipe, in which the entering flow has uniform axial-and linearly varying tangential-velocity components. The analysis is carried out within the framework of the boundary layer theory, the solutions being obtained by means of an extended form of the finite difference method invented by Leigh and Terril. the following results are obtained from the analysis: (1) The entrance length is significantly increased by the presence of swirl at the entrance section. (2) The additional pressure drop based on the center-line pressure at the entrance section is considerably decreased as the swirl is increased. (3) If the wall temperature is constant, the local Nusselt number is increased by a few percent at a certain distance downstream from the entrance section when Prandtl number is taken as 0.72. (4) The damping coefficients of the swirl show an exponential decay shortly after the entrance section. However, in the immediate neighbourhood of the entrance section, the damping of the swirl is a little faster than the exponential decay.
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