Visualization of transient interfacial waves induced by spin-up of two immiscible fluid layers
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Interfacial waves of two immiscible layers in a spin-up container were investigated using experimental visualization. While the interface near the central part rose up, instability waves propagated in an azimuthal direction on the interface. These waves were mainly caused by Kelvin–Helmholtz instability for the velocity difference between two layers during spin-up, but had complicated transient characteristics owing to the rotation in a closed system. We visualized the structure of the interfacial waves by the use of three types of optical characteristics of the interface. Image processing provided the detailed factors of the interfacial waves that were classified in four life stages from their generation to disappearance. The initial generation process involved many frequency modes due to a large velocity difference, and then a low mode stood out during the growth, and disappeared with an ellipsoidal sloshing mode to achieve the rigid rotation in both layers.
KeywordsInterfacial wave Instability Two-layered flow Rotating flow
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