Effect of Vessel Aspect Ratio in Subcritical Turbulence of Plane Couette Flow in 3D Yukawa Liquids

Subcritical turbulence occurs very abruptly and there is discontinuous transition from laminar state to localized turbulent state. Plane Couette flow (PCF) is a one class of flow, which shows subcritical transition to turbulence. A subcritical transition to turbulence in PCF is recognized by the occurrence of turbulent spots[1] or turbulent bands[2]. In experiments, turbulent spots are triggered by subjecting the system to a jet [3] or introducing a ``bead'' or a ``wire''[4] in the middle of the flow. In simulation, turbulent spots are triggered by Lundbladh-like perturbation[1] and bands are produced by uncorrelated unlocalized finite amplitude white noise[2]. There are various physical factors on which the subcritical transition to turbulence depends on, such as, type of perturbations, value of Reynolds number and system size or aspect ratio. However, we shall focus our investigation on studying the effect of aspect ratio in the subcritical dynamics of PCF.

In the past, we have studied spot formation process in a 3D Yukawa liquid using Molecular dynamics (MD) simulation [1]. To know more about the effect of aspect ratios in subcritical dynamics of PCF at a particle level, we have studied the subcritical turbulence of PCF in a 3D Yukawa liquid at various aspect ratios using MD simulation[5]. We have found that the aspect ratio of the system has significant effect in Fourier space, coherent structures or the turbulent spot structures, spatio-temporal dynamics, etc [5]. For example, in Fourier space, the two dominant modes corresponding to the large-scale and small-scale flow [1] observed very distinctively upon increasing the aspect ratio or size of the system. The number of streak nucleation also observed to increase with the increasing aspect ratio.

In the above paragraph, we have just mentioned few of the results obtained from our simulations. More such results will be presented in details in the Conference.