LAMINAR-FLOW IN ROTATING CURVED PIPES

When a curved pipe rotates about the centre of curvature, the fluid fl owing in it is subjected to both Coriolis and centrifugal forces. Base d on the analogy between laminar flows in stationary curved pipes and in orthogonally rotating pipes, the flow characteristics of fully deve loped laminar flow in rotating curved pipes are made clear and definit e by similarity arguments, computational studies and using experimenta l data. Similarity arguments clarify that the flow characteristics in loosely coiled rotating pipes are governed by three parameters: the De an number K-LC, a body force ratio F and the Rossby number R0. As the effect of R0 is negligible when R0 is large, computational results are presented for this case first, and then the effect of R0 is studied. Flow structure and friction factor are studied in detail. Variations o f flow structure show secondary flow reversal at F approximate to -1, where the two body forces are of the same order but in opposite direct ions. It is also shown how the Taylor-Proudman effect dominates the ho w structure when R0 is small. Computed curves of the friction factor f or constant Dean number have their minimum at F approximate to -1. A c omposite parameter K-L is introduced as a convenient governing paramet er and used to correlate the characteristics. By applying K-L to the a nalogy formula previously derived for two limiting hows, a semi-empiri cal formula for the friction factor is presented, which shows good agr eement with the experimental data for a wide range of the parameters.