Fluid and plasma dynamics play an important role in many areas of both physics and engineering. Progress in this field requires the application of the most sophisticated methods of modern theoretical and experimental physics.

Professor Joel Koplik's research concerns the subcontinuum aspects of fluid mechanics, which are relevant for situations in which molecular scale information is needed to complement a macroscopic description. Using molecular dynamics, large-scale numerical computations determine the trajectories of individual molecules, and then the average behavior of the fluid is deduced. For example, the characteristics of the spreading of liquids on solid surfaces are sensitive to the structure of the materials involved. A recent study indicated how different spreading regimes (partial, complete, and terraced) are interrelated and quantified the molecular motion associated with each. Current work in this area concerns dewetting, the withdrawal of a partially wetting liquid from an out-of-equilibrium configuration covering a substrate, and the effects of surfactant additives on wetting dynamics. Another recent study investigated the nature of the boundary condition for a mixture of two liquids at a solid wall, and whether there were deviations from the familiar no-slip behavior. A further area of current interest concerns the fluid dynamics of non-Newtonian liquids such as polymer melts. Aside from uncertainties about their correct macroscopic dynamical equations, such materials exhibit intriguing surface instabilities, such as sharkskin and melt fracture, when extruded into jets. We are now formulating molecular-scale simulations aimed at understanding the origins of such behavior. Research in fluid mechanics also goes on at the Benjamin Levich Institute for Physico-chemical Hydrodynamics, chaired by Professor Andreas Acrivos. The institute is an interdepartmental organization devoted to research in fluid mechanics. Its staff includes faculty members active in this area and their research students and fellows. Currently, the principal research topics at the institute include bio-fluid mechanics, dynamic wetting phenomena and the effects of surfactants, dynamical systems theory and chaos, the effective properties of composite materials, free-surface flows, hydrodynamic stability theory, the mechanics of sedimentation and suspensions, molecular fluid mechanics, the transition to turbulence, and theories of fully developed turbulence and turbulent structures.