J. L. Duda

Fluid mechanics of laminar liquid jets

Abstract The flow behavior of Newtonian jets is analyzed by the use of a coordinate system which reduces the problems associated with free boundaries. The resulting general equations are simplified by a boundary-layer type analysis and numerical as well as approximate analytical solutions are presented. These solutions predict the velocity distributions and the shape of jets under the influence of surface and body forces. Measurements of jet shape confirm the accuracy of the calculations. The methods developed in this study can in principle be useful in the analysis of a wide class of free-boundary problems.

Analysis of Two-Dimensional Diffusion-Controlled Moving Boundary Problems

This paper presents a technique for the analysis of unsteady, two-dimensional diffusive heat- or mass-transfer problems characterized by moving irregular boundaries. The technique includes an immobilization transformation and a numerical scheme for the solution of the transformed equations. Specifically, the immobilization consists of transforming the governing partial differential equations into a coordinate system where the phase boundaries correspond to fixed coordinate surfaces. An example problem involving the solidification or melting of a finite cylinder is analyzed, and results for a range of conditions are presented.

DRYING OF SOLVENT COATED POLYMER FILMS

ABSTRACT The ability to predict the drying behavior of coating is of great importance to the coating industry. For this purpose, the model developed by Vrentas and Vrentas has been used to predict the concentration profile as well as the thickness and the temperature change of the polymer film as a function of time. The model incorporates the coupling between heat and mass transfer and diffusion induced convection which occurs when a single layer of a binary polymer solution is dried in a convection heated oven. The model was solved numerically by using the finite difference approximation and it was applied to the well characterized polyvinylacetate(PVAC)-toluene system. The effects of operating conditions on

Solution adsorption from liquid chromatography

Abstract The dynamic technique of frontal analysis is applied toward the measurement of binary solution-solid adsorption utilizing a commercial liquid chromatograph. The original mathematical treatment of ideal equilibrium chromatography is reexamined. Careful analysis of the chromatographic adsorption process indicates that the absolute surface excess concentration determined from the dynamic experiment is constrained to be a volumetric reduced adsorption if the assumption of constant volumetric flow rate is made. A macroscopic approach, however, shows that this constraint can be removed if, in addition to the outlet concentration, the outlet flow rate is accurately monitored. The macroscopic approach also reveals that the dynamic technique can be applied in spite of finite mass transfer resistance and adsorption kinetics. New dynamic and static experimental results for the system n-hexane/n-hexanol/silica gel are presented and are shown to agree over the entire composition range. The advantages of the dynamic flow technique are outlined.

Heat or mass transfer-controlled dissolution of an isolated sphere

Abstract A comprehensive set of finite-difference solutions describing the heat or mass transfer-controlled dissolution of isolated spheres is presented. The analysis is based on a generalized formulation which includes three specific classes of dissolution problems. A coordinate transformation which immobilizes the moving boundary and maps the infinite region of interest into a finite region is used to minimize the difficulties associated with a numerical analysis of this problem. Radius-time and particle lifetime results are reported for ranges of parameters which include the majority of physically important dissolution processes. In addition, the results of this investigation are used to determine the accuracy and range of applicability of various approximate analytical solutions.

The Chemical Degradation of Ester Lubricants

Gel permeation chromatography is shown to be a valuable technique for analysis of the oxidation and thermal degradation products of various types of esters. Esters potentially useful as synthetic lubricant basestocks, such as tridecyl pelargonate (a mono-ester), di-2-ethylhexyl sebacate (a diester) and trimethylolpropane triheptanoate (a neopentyl polyolester) form products of up to 50 000 molecular weight when oxidized at high temperatures. The oxidation products have been separated by molecular weight using preparative gel permeation chromatography (GPC) and then have been analyzed spectrographically. The polymeric products of oxidation show similar chemical bond structure for the various types of esters studied. The importance of oxygen and metal catalysis on product formation is demonstrated. The influence of steel surfaces on the products of oxidation suggests a tribochemical reaction resulting in the ultimate formation of a “friction polymer.” Presented at the 33rd Annual Meeting in Dearborn, Michig...

Flow of a newtonian fluid through a sudden contraction

The full Navier-Stokes equations describing flow through a sudden contraction are solved by an explicit finite-difference method. Streamlines, vorticity distributions, velocity profiles, excess pressure drops, and entrance lengths are calculated as functions of Reynolds number and radius ratio. The results are compared with existing experimental data and the limited theoretical work available.

Steady flow in the region of closed streamlines in a cylindrical cavity

An analytical solution is developed to describe the steady, closed streamline velocity field within a cylindrical cavity with a uniformly translating wall at low Reynolds numbers. The solution has application for the case of two-phase flow in a tube where regions of fluid are segmented by a moving train of bubbles or plugs, such as in the pulmonary and peripheral capillaries of the body where segments of plasma are trapped between red blood cells. The mathematical approach presented in this study can in principle be useful in the analysis of a wide class of closed-streamline creeping-flow problems.

Wear Characteristics of Aluminum-Silicon Alloy under Lubricated Sliding Conditions

The wear characteristics of aluminum-silicon alloys were studied using a pin-on-disk-type wear tester with different types of lubricants under fully flooded condition. Aluminum-silicon alloy pin specimens were run against the same aluminum-silicon disc surfaces. Wear tests showed that wear resistance of aluminum-silicon alloy was largely influenced by the type of lubricant. Test results showed that hydrocarbon-based fluids such as mineral oils or poly-a-olefins exhibit better wear-protecting property and higher load-carrying capacity than polar base fluids such as polyol esters or polyalkylene glycols. This is contrary to the results of iron-iron systems. The effect of water on the wear and scuffing resistance of aluminum-silicon alloy was also investigated. Water was found to promote the formation of aluminum oxide and silicon oxide layers on the surface which reduced the wear rate and increased scuffing load for aluminum-silicon alloy. Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19,...

Molecular diffusion in polymeric systems

Diffusion dans les polymeres fondus et en solution; diffusion dans les verres polymeriques; diffusion dans les polymeres composites