Elastic convection in vibrated viscoplastic fluids
Hayato Shiba1, Jori E Ruppert-Felsot, Yoshiki Takahashi
1Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Physical Review Letters
|March 16, 2007
Summary
Freestanding convection rolls spontaneously form in oscillating shear-thinning yield stress fluids. The onset of this novel fluid behavior is governed by a critical stress related to fluid inertia and yield stress.
Area of Science:
- Fluid dynamics
- Non-Newtonian fluid mechanics
- Pattern formation
Background:
- Yield stress fluids exhibit a critical stress threshold before flow initiation.
- Vertical oscillations can induce complex behaviors in fluids.
- Convection typically requires boundary constraints for pattern formation.
Purpose of the Study:
- To investigate the emergence of freestanding convection rolls in shear-thinning yield stress fluids under vertical oscillation.
- To determine the parameters governing the spontaneous selection of convection roll diameter.
- To identify the critical stress condition for the onset of convective motion.
Main Methods:
- Experimental observation of fluid behavior under controlled vertical oscillations.
- Systematic variation of oscillation parameters (amplitude, frequency).
- Analysis of fluid motion to characterize convection roll formation and stability.
Main Results:
- Observation of novel freestanding convection rolls in shear-thinning yield stress fluids.
- Spontaneous selection of convection roll diameter across a range of parameters without container boundaries.
- Hysteresis-free transition to convection above a critical plate acceleration amplitude.
Conclusions:
- Vertical oscillation can drive freestanding convection in shear-thinning yield stress fluids.
- A nondimensional stress, comparing inertial to yield stress, dictates the onset of convection.
- The findings reveal new possibilities for pattern formation in complex fluids.
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