Engineering topics

Lyell, M. J.

Publications and source records attributed to Lyell, M. J..

12 records

NASA NTRS1994

Project JOVE

The goal of this project is to investigate new areas of research pertaining to free surface-interface fluids mechanics and/or microgravity which have potential commercial applications. This paper presents an introduction to ferrohydrodynamics (FHD), and discusses some applications. Also, computational methods for solving free surface flow problems are presented in detail. Both have diverse applications in industry and in microgravity fluids applications. Three different modeling schemes for FHD flows are addressed and the governing equations, including Maxwell's equations, are introduced. In the area of computational modeling of free surface flows, both Eulerian and Lagrangian schemes are discussed. The state of the art in computational methods applied to free surface flows is elucidated. In particular, adaptive grids and re-zoning methods are discussed. Additional research results are addressed and copies of the publications produced under the JOVE Project are included.

Lyell, M. J.↗

NASA NTRS1994

Nonlinear effects on the natural modes of oscillation of a finite length inviscid fluid column, supplement 2

The aspects of nonlinear behavior of a finite length liquid column is investigated with an emphasis on bridge dynamics. The primary objectives are to determine the nonlinear corrections to the interface shape of a naturally oscillating finite length liquid column and to determine the nonlinear corrections to the oscillation frequencies for various modes of oscillation. Application of the Lindstedt-Poincare expansion in conjunction with the domain perturbation techniques results in an hierarchical system of equations.

Lyell, M. J.↗

NASA NTRS1993

Fluid column stability in the presence of periodic accelerations

The interface stability of fluid columns in the presence of a periodic acceleration field with a component normal to the longitudinal axis of the isothermal cylinder was investigated. Floquet theory was used in the investigation and the column was taken as infinite. The finite length case was also studied and axisymmetric and nonaxisymmetric oscillations were considered. Results for the infinite length case were good approximations to those for the finite length column.

Lyell, M. J.↗

NASA NTRS1992

Interface stability of a fluid column subject to periodic accelerations normal to the longitudinal axis of the column

This project investigates the interface stability of an inviscid fluid column in the presence of a periodic acceleration field which has a component normal to the longitudinal axis of the column. A ramification of this configuration is that perturbations cannot be considered axisymmetric. The column is taken to be infinite in length. Floquet analysis will be utilized in the stability investigation.

Lyell, M. J.↗

NASA NTRS1992

Acoustic forcing of a liquid drop

The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

Lyell, M. J.↗

NASA NTRS1991

Effect of periodic accelerations on interface stability in a multilayered fluid configuration

The increasing number of research opportunities in a microgravity environment will benefit not only fundamental studies in fluid dynamics, but also technological applications such as those involving materials processing. In particular, fluid configurations that involve fluid-fluid interfaces would occur in a variety of experimental investigations. This work investigates the stability of a configuration involving fluid-fluid interfaces in the presence of a time-dependent (periodic) forcing. The fluid configuration is multilayered and infinite in extent. The analysis is linear and inviscid, and the acceleration vector is oriented perpendicular to each interface. A Floquent analysis is employed, and the resulting algebraic eigensystem is truncated. Nondimensional parameters appear in the algebraic system. A numerical study is performed to elucidate the regions of instability and the effect of parameter variation on the fluid configuration stability.

Lyell, M. J.↗

NASA NTRS1991

Axial forcing of an inviscid finite length fluid cylinder

Current interest in microgravity materials processing has focused attention upon the finite fluid column. This configuration is used in the modeling of float zones. In this paper the incompressible inviscid finite length fluid column is subjected to an axial, time-dependent disturbance. The response of the fluid system and the resulting interface location are determined via Laplace transform methods.

Lyell, M. J.↗

NASA NTRS1991

Instability of multi-layer fluid configurations in the presence of time-dependent accelerations in a microgravity environment

The increasing number of research opportunities in a microgravity environment will benefit not only fundamental studies in fluid dynamics, but also technological applications such as those involving materials processing. In particular, fluid configurations which involve fluid-fluid interfaces would occur in a variety of experimental investigations. This work investigates the stability of a configuration involving fluid-fluid interfaces in the presence of a time-dependent forcing. Both periodic (g-jitter) and nonperiodic accelerations are considered. The fluid configuration is multilayered, and infinite in extent. The analysis is linear and inviscid, and the acceleration vector is oriented perpendicular to each interface. A Floquet analysis is employed in the case of the periodic forcing. In the problem of nonperiodic forcing, the resulting system of equations are integrated in time. Specific nondimensional parameters appear in each problem. The configuration behavior is investigated for a range of parameter values.

Lyell, M. J.↗

NASA NTRS1991

Interface behavior of a multi-layer fluid configuration subject to acceleration in a microgravity environment, supplement 1

With the increasing opportunities for research in a microgravity environment, there arises a need for understanding fluid mechanics under such conditions. In particular, a number of material processing configurations involve fluid-fluid interfaces which may experience instabilities in the presence of external forcing. In a microgravity environment, these accelerations may be periodic or impulse-type in nature. This research investigates the behavior of a multi-layer idealized fluid configuration which is infinite in extent. The analysis is linear, and each fluid region is considered inviscid, incompressible, and immiscible. An initial parametric study of confiquration stability in the presence of a constant acceleration field is performed. The zero mean gravity limit case serves as the base state for the subsequent time-dependent forcing cases. A stability analysis of the multi-layer fluid system in the presence of periodic forcing is investigated. Floquet theory is utilized. A parameter study is performed, and regions of stability are identified. For the impulse-type forcing case, asymptotic stability is established for the configuration. Using numerical integration, the time response of the interfaces is determined.

Lyell, M. J.↗

NASA NTRS1986

Oscillations of a viscous compound drop

The effect of viscosity on normal mode oscillations of a compound drop is determined for a range of values of the viscosity, and the effect of a host medium is considered. The general form of the dispersion relation is derived, and numerical values are obtained for the case of an annular liquid region composed of silicon oil and with the core and host regions taken to be air. Results indicate that the sloshing mode of the compound drop is more damped than the bubble mode.

Lyell, M. J.↗

NASA NTRS1985

Viscous damping of the oscillations of a rotating simple drop

The viscous damping of the small-amplitude capillary oscillations of a rotating simple drop is calculated in the small viscosity limit. The calculation concerns the case of a liquid drop in a gaseous medium, which is relevant to the space processing of materials using acoustic levitation. The method used is that of Lamb in which the inviscid solutions of the problem are used as trial functions in the energy equation to find the damping coefficient.

Lee, C. P.↗

NASA NTRS1985

Oscillations of a compound drop system undergoing rotation

A compound liquid-drop system is comprised of three immiscible concentric fluids: a core fluid of density p(i) surrounded by a shell of density p(s) which is embedded in a medium of density p(o). In this analysis, the fluids are incompressible and inviscid. The effect of rotation upon the modes of oscillation of a compound drop is investigated. Rotation rate is considered as a small perturbation of the normal modes of the compound drop, thus introducing the effects of a Coriolis force and a centrifugal distortion.

Lyell, M. J.↗