Engineering topics

Finn, R.

Publications and source records attributed to Finn, R..

9 records

NASA NTRS1999

A Symmetry Breaking Experiment Aboard Mir and the Stability of Rotating Liquid Films

We discuss results from two parts of our study on the behavior of liquids under low-gravity conditions. The first concerns the Interface Configuration Experiment (ICE) aboard the Space Station Mir on the Mir-21/NASA-2 mission; for a certain 'exotic' container, distinct asymmetric liquid configurations are found as locally stable ones, even though the container itself is rotationally symmetric, in confirmation of mathematical results and numerical computations. The second investigation concerns the behavior of slowly rotating liquids; it is found that a rotating film instability observed previously in a physical experiment in 1-g, scaled to render gravity effects small, does not correspond to mathematical and computational results obtained for low gravity. These latter results are based on the classical equilibrium theory enhanced with a van der Waals potential of adhesion.

Concus, P.↗

NASA NTRS1998

Measurement of Critical Contact Angle in a Microgravity Space Experiment

Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USML-2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

Concus, P.↗

NASA NTRS1998

Measurement of Critical Contact Angle in a Microgravity Space Experiment

Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USMT,2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

Concus, P.↗

NASA NTRS1996

Equilibrium liquid free-surface configurations: Mathematical theory and space experiments

Small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. We describe some of our mathematical results that predict such behavior and that form the basis for physical experiments in space. The results include cases of discontinuous dependence on data and symmetry-breaking type of behavior.

Concus, P.↗

NASA NTRS1992

On accurate determination of contact angle

Methods are proposed that exploit a microgravity environment to obtain highly accurate measurement of contact angle. These methods, which are based on our earlier mathematical results, do not require detailed measurement of a liquid free-surface, as they incorporate discontinuous or nearly-discontinuous behavior of the liquid bulk in certain container geometries. Physical testing is planned in the forthcoming IML-2 space flight and in related preparatory ground-based experiments.

Concus, P.↗

NASA NTRS1985

Free Surface Phenomena Under Low- and Zero-Gravity Conditions

In a low- or zero-gravity environment the free surface of a liquid can behave in striking, unexpected ways. For example, in a partially filled container, a free surface that is well behaved under terrestrial conditions can rise to an arbitrarily large height or even fail to exist when gravity is absent. An answer is sought to the central mathematical questions: Under what conditions can free surfaces exist and what are their properties? -- and experimental questions of what means can be devised to observe and to measure the surfaces quantitatively. Current activity focuses on material selection and the design of optical diagnostic methods for in-space experiments. These experiments will test mathematical predictions of discontinuous transition from existence to nonexistence of capillary free surfaces in certain geometric configurations under zero gravity conditions. Liquids and container materials suitable for achieving the required contact-angle range and optical properties are being investigated, as well as the effects of contaminants and fluid motion on contact angle. The optical diagnostic technique investigation concerns laser-induced fluorescence, including emphasis on data on acquisition, sources and detectors, reliability, data management, and computer control.

Concus, P.↗

NASA NTRS1982

The size and shape of equilibrium capillary surfaces

The classical theory of capillary is concerned largely with size and shape estimates in symmetric asymptotic configurations. Recent developments leading to global results for all symmetric cases, and to qualitative information on asymptotic properties are discussed. Additional stability criteria are described. Asymmetric situations leading to behavior that differs strikingly from the symmetric case are discussed. When gravity vanishes, capillary surfaces in the accustomed sense may not appear. The question of characterizing those tubes in which surfaces can be found has partially been settled. Progress toward determining the effects of contact angle hysteresis in cases of particular interest is reported.

Finn, R.↗

NASA NTRS1979

The shape of a pendent liquid drop

Formal solutions of the static equilibrium equations for the form of the outer surface of a pendent liquid drop are studied. An approach is adopted in which only the one-parameter family determined by vertex height (u sub 0) need be described. Attention is restricted to rotationally symmetric configurations, and all symmetric solutions are characterized for the case where the Lagrange parameter lambda is equal to zero. It is shown that for any u sub 0 the function u(r; u sub 0) can be extended as a parametric solution of a system of equations for all arc lengths, yielding a curve without limit sets or double points, and that the resulting capillary rotation surface spreads out indefinitely away from the axis r = 0. The asymptotic form of the surface in the case of large absolute values of u sub 0 is characterized quantitatively, along with the global structure of all such surfaces.

Concus, P.↗

NASA NTRS1977

Mathematical and computational studies of equilibrium capillary free surfaces

The results of several independent studies are presented. The general question is considered of whether a wetting liquid always rises higher in a small capillary tube than in a larger one, when both are dipped vertically into an infinite reservoir. An analytical investigation is initiated to determine the qualitative behavior of the family of solutions of the equilibrium capillary free-surface equation that correspond to rotationally symmetric pendent liquid drops and the relationship of these solutions to the singular solution, which corresponds to an infinite spike of liquid extending downward to infinity. The block successive overrelaxation-Newton method and the generalized conjugate gradient method are investigated for solving the capillary equation on a uniform square mesh in a square domain, including the case for which the solution is unbounded at the corners. Capillary surfaces are calculated on the ellipse, on a circle with reentrant notches, and on other irregularly shaped domains using JASON, a general purpose program for solving nonlinear elliptic equations on a nonuniform quadrilaterial mesh. Analytical estimates for the nonexistence of solutions of the equilibrium capillary free-surface equation on the ellipse in zero gravity are evaluated.

Albright, N.↗