| Summary: | Taylor-Couette flow is a viscous flow inside an annulus cylinder, whereas
the outer and the inner cylinders are made fix and rotating respectively. If the
axial flow takes part in this situation, the flow is defined as Taylor-Couette-
Poiseuille flow. It can be found in some engineering applications such as in
journal bearings, electric generators and motors, oil drillings, nuclear and
chemical reactors, and also heat exchangers. If the rotation speed of the inner
cylinder attains the critical speed, the onset of instability occurs. Here the laminar
flow changes to the transition flow before becoming turbulent. In addition, it is
noticed that a high pumping power to turn the inner cylinder is needed in order to
change the sequence of the flow patterns in the transition flow.
The instability of the transition flow in a Taylor-Couette-Poiseuille flow was
studied experimentally. The main objective was to clarify the effects of the
geometry and the dynamic parameters on the flow pattern and the friction factor
in the transition condition from the laminar to the turbulent flow. The test section
was an annulus cylinder with a rotating inside cylinder. The diameter of outer
cylinder was made unchanged of 140 mm. The inner cylinders were 100 mm and
135 mm, therefore the radius ratios were 0.716 and 0.964 respectively. The
length of the cylinder was 800 mm, hence their aspect ratios were 40 and 320
respectively. The working fluids were water and water-glycerin solutions. The
rotation speeds of the inner cylinder were varied from 7 to 49 rpm. The axial flow
was 0.1 � 1 gpm. The circumferential and the axial Reynolds numbers ranged
from 135.1 � 5568 and 31.7 � 316.6 respectively. In the experiments at radius
ratio of 0.716, aluminium powder was added to the working fluids in order to
obtain a high quality picture for the visualization study purposes.
From the visualization studies, it is found that the spiral vortex flow pattern
appears at low speed of the inner cylinder and no axial flow. This flow pattern is
different with the circumferential vortex if the upper and lower ends of the annulus
cylinder are closed. At higher rotating, the circumferential and turbulent vortices
are found. If the axial flow took part, the vortices move in the same direction of
the axial flow. The average wave length in the axial direction and wave numbers
were 0.055 m and 2.284 respectively.
From the measurement it is concluded that: (1) the axial friction decreases with
the increase of the flow rate, rotation and gap of the annulus cylinder. Flow
resistance can be expressed as 1 88 1 8 19 93 1 2904 , , , f Re Ro ï� ï� ï� ï�½ ï�¨ with correlation coefficient of 0,94, and average error of 23,8%. The equation is valid for Re1 = 135,1 â�� 5586, Ro = 0,0065 â�� 2,3443, ï�¨ = 0,716 â�� 0,964
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