Mild mixing effect is observed in the Taylor vortex flow (TVF) system in which the animal and plant cell walls are not disrupted as much as other bioreactor systems. These facts would be more important in developing a new bioreactor system, which plays an active role in the medical and bioindustrial fields. Although the mixing methods with an impeller are often used for an agitation in synthetic polymerization, the problem is that there exists a high shearing flow region just after the moving impeller. This region for instance, would cause the destruction of the alga cell when a microorganism in suspension is used as a bioreactor. The TVF is expected to reduce the local increase of these shearing forces because the device doesn’t have any impeller, and lead the bioreactor system to more uniform and stable states in the flow fields for cultivation or oxygen production. TVF in a single-phase flow with an infinite annulus is well known since it has a spectrum transition to turbulence and the oscillation is observed from the wavy vortex mode. Recent Takeda’s study has measured the precise spatiotemporal velocity fields by using the ultrasonic velocity profiler (UVP). On the other hand with a short annulus, we have various vortex modes generated due to the Ekman boundary layers occurred near the upper and lower solid boundaries. Each vortex mode also has the same spectrum transition such as wavy, modulated and soft turbulence modes. But the flow state seems much different from the infinite annulus. Present study measures the velocity profiles of the flow in TVF with a short annulus by using the UVP. We focus on not only the velocity profiles, but also the spectra in oscillation mode that occurs in different vortex modes. From the results, the spectra of the various oscillations are occurred with increase of Reynolds number, and seem different from those in the infinite annulus. This oscillation analysis would contribute to the basic knowledge of the mixing effect in solid-liquid flow when a microorganism in suspension is used as a bioreactor.

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