Axisymmetric and double helix types of vortex breakdown in a straight circular pipe are observed by the flow visualization with kerosene mist. The type and position of the breakdowns are Studied by varying the Reynolds number and the circulation number.
Vortex breakdown is so sensitive to the external disturbance that the use of measuring method With no disturbance to the flow is required. In this connection, we make use of the laserdoppler velocimeter with injecting kerosene mist as a tracer.
Distributions of axial and circumferential velocity components along the radius are measured at various axial stations for two cases of the axisymmetric type. The velocity along the axis, flow patters, the axial variation of the vortex core, and so on are also obtained.
From the results described above, the structure of axisymmetric breakdown, especially, the outline of the flow reversal region is clarified to some degree.
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