Viscosity of a dusty plasma liquid
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AL, NONLINEAR, AND SOFT MATTER PHYSICS
Viscosity of a Dusty Plasma Liquid N. A. Vorona, A. V. Gavrikov, A. S. Ivanov, O. F. Petrov, V. E. Fortov, and I. A. Shakhova Institute of Thermal Physics of Extreme States, Russian Academy of Sciences, ul. Izhorskaya 13/19, Moscow, 125412 Russia e-mail: [email protected] Received December 1, 2006
Abstract—We present the results of our experimental study of the flow of a dusty plasma liquid produced by macroparticles in an argon plasma. The dependences of shear viscosity for such a liquid on the magnitude of the external force inducing the dusty plasma liquid flow and on the plasma-generating gas pressure are analyzed. We have established that the viscosity of a dusty plasma medium decreases with increasing shear stress in it, while the viscosity of such a liquid increases with buffer gas pressure. The flow of a dusty plasma liquid under the action of an external force has been found to resemble the plastic deformation of a Bingham body. We suggest that the formation of crystal-like dusty plasma clusters in a “liquid” phase can be responsible for the non-Newtonian behavior of the dusty plasma liquid flow. PACS numbers: 52.27.Lw DOI: 10.1134/S1063776107100172
1. INTRODUCTION Investigation of phenomena related to the viscosity of a dusty plasma attracts increasing attention, since it can provide new information about the structure and properties of the strongly coupled system under consideration. The viscous properties of a medium with a screened Coulomb interaction have been mathematically modeled in [1, 2]. In addition, experimental works have been done in recent years to directly measure the shear viscosity of a dusty plasma [3, 4]. In [3], an attempt was made to experimentally determine the shear viscosity of a 2D system—a layer of macroparticles in a dusty plasma trap. The shear viscosity was first estimated in [4] when studying a laminar flow in the 3D case. The existence of internal friction in a dusty plasma medium was established experimentally and the shear viscosity of the dust component was estimated. Note that the results of [3] and [4] differ by two orders of magnitude: η/ρ ≈ 2 mm2 s–1 [3] and ≈1.3 × 102 mm2 s–1 [4]. This difference could have been attributed to different dimensions of the objects under study. At the same time, there is a significant difference between the conditions for the existence of a dusty plasma structure in these papers. This is primarily true for the plasma-generating gas pressure. In [3] and [4], the dusty plasma trap existed at pressures of about 1 and 35 Pa, respectively. Therefore, analyzing the dependence of shear viscosity on the plasma-generating gas pressure is undoubtedly of considerable interest. In addition, several points (the formation of a flow channel that exceed appreciably in sizes the region of external action and the threshold nature of the flow) indicative of an anomalous behavior of the dusty plasma flow were noted in [4]. The formation of a flow channel that exceeds appreciably the region of external
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