title: Pressure distribution in unsteady sink and source flows.
abstract: Basic flow generated in a viscous incompressible fluid by a "point" sink (source) of mass is revised. In practice, such flow can be modeled by sucking (pushing) fluid from a thin tube with a small porous sphere at one end. Intuitively, by sucking (pushing) fluid, one creates low (high) pressure near the origin and a positive (negative) radial pressure gradient drives the fluid to (from) the origin. A simple analysis, however, shows that the pressure distribution for both steady flows is the same. Then a question arises: How does the fluid "know" in what direction to flow? To explain this "paradox" an unsteady flow is considered and the pressure terms responsible for the flow direction are derived.
authors.affiliation: University of Notre Dame, Notre Dame, Indiana 46556, USA and P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow 117851, Russia.
authors.forename: S I
authors.initials: SI
authors.lastname: Voropayev