David P. Hoult

PHYSICAL PROCESSES IN THE SPREAD OF OIL ON A WATER SURFACE

ABSTRACT Formulae are recommended for calculating the extent of the spread of oil slicks on water as a function of time. They are based on empirical measurements of spreading rates and analytical and theoretical studies of the physical processes which accelerate or retard the spread of a film Both one-dimensional and two-dimensional (axisymmetric) slicks are treated. Comparisons of the recommended formulae are made with the limited number of field observations, both for the rate of spread and the maximum slick size.

Architectural innovation in product development through early supplier integration

The paper explains how an important opportunity exists to pro-actively integrate suppliers at an early stage in the concept exploration and definition stages of product development. Research suggests that the concept of architectural innovation can be extended so that product features are matched with the associated specialized technical skills of partners in the development team. In addition to the establishment of integrated product teams, key enablers include: long-term commitment to suppliers; co-location; joint responsibility for design and configuration control; seamless information flow; and retaining flexibility in the definition of system configuration. Important contributing factors include: supplier-capability-enhancing investments; target costing; and incentive mechanisms. To promote innovative outcomes in military and government programmes, attention is drawn to the importance of governments championing closely-knit customer-supplier relationships. Firms can build enduring competitive strength by leveraging the specialized knowledge bases of their supplier networks. Two case-studies provide lessons to improve current approaches to the creation of long-term partnerships, or strategic alliances, with suppliers.

A Theory of Plume Rise Compared with Field Observations

A theory for the rise of a plume in a horizontal wind is proposed in which it is assumed that, for some distance downwind of a high stack, the effects of atmospheric turbulence may be ignored in comparison with the effects of turbulence generated by the plume. The theory, an extension of the local similarity ideas used by Morton, Taylor, and Turner,1 has two empirical parameters which measure the rate that surrounding fluid is entrained into the plume. Laboratory measurements of buoyant plume motion in laminar unstratified cross flow are used to estimate the empirical parameters. Using this determination of the parameters in the theory, the trajectories of atmospheric plumes may be predicted. To make such a prediction, the observed wind velocity and temperature as functions of altitude, and flow conditions at the stack orifice, are used in numerically integrating the equations. The resulting trajectories are compared with photographs, made by Leavitt, et al.,2 of TVA, of plumes from 500 to 600 ft high sta...

Turbulent plume in a laminar cross flow

Abstract A simple entrainment hypothesis, a synthesis of previous models, is presented to explain the rise and growth of a turbulent plume in a laminar cross flow. The entrainment rate is assumed proportional to the plume parameter and the tangential and normal velocity differences between the plume and the surrounding fluid. Because a linear combination of the entrainment due to each velocity difference is assumed, two constants of proportionality or entrainment parameters are introduced in the model. Sources of momentum, buoyancy or combinations of the two are accounted for by the theory. The major purpose of this research was to determine the entrainment parameters. Experiments done in neutrally stable ambient fluids show that the entrainment coefficients have, within the scatter of available data, constant values for a fully turbulent plume and small density differences. Superposition of the two entrainment effects was verified by experiments on pure jets in a cross flow.

High Reynolds number flow in a moving corner

The problem of a piston moving in a cylinder is studied experimentally using flow visualization techniques. A vortex motion is observed at the piston face and cylinder wall interface as the cylinder wall moves toward the piston. Non-dimensional scaling parameters for the vortex size and stability are determined and semi-empirical theories for the size of the vortex are presented.

Laboratory experiments of smokestack plumes in a stable atmosphere

Abstract This research is concerned with the simulation in laboratory experiments of the motion of buoyant smokestack plumes in the atmosphere. The theoretical results of previous researchers are presented and used to determine the dimensionless parameters of the flow. The conditions for geometric similarity to field scale plumes are discussed and it is shown that Reynolds number need not be simulated provided the plumes are fully turbulent at the stack exit. The thermally-stratified wind tunnel at M.I.T. is described and its operating characteristics are discussed. The significance of maintaining supercritical flow is explained and illustrated. The results of plume rise measurements made in the tunnel are presented and shown to be accurately described by the theoretical model, with minor modifications. The geometric similarity of model plumes to field measurements of plumes is clearly demonstrated. The close agreement between laboratory experiments and field measurements lends additional credence to the contention that atmospheric turbulence does not play a significant role in plume rise phenomena.

Development of a theoretical cost model for advanced composite fabrication

Abstract This paper outlines the development of a theoretical approach to the estimation of processing time for the fabrication of advanced composite parts. The model, termed ‘first-order model’, assumes that all subprocess steps can be modelled as having first-order dynamics. The steps are then linearized and summed according to their ‘extensive’ variables. Part complexity is handled using an information theoretic approach. The result for hand lay-up is a simple linear equation which compares favourably with experiments and with other very detailed cost estimation models. The model is very general, and appears applicable to all additive (composites) as well as subtractive (machining) processes.

A CORRELATION OF FIELD OBSERVATIONS OF PLUME RISE

Data from 137 sets of plume observations, comprising nearly 1 500 data points, are correlated with two simple formulae. These formulae, one for the buoyancy-dominated rise region and the other for the stratification-dominated levelled-off region of a plume, represent an approximate form of the entrainment theory of Hoult, et al. (1968)1 for the case of uniform atmospheric stratification and zero wind shear. The observations, which are those of the Tennessee Valley Authority and of Bringfelt (1968),6 were made of plumes whose source strengths ranged from 0.4 to 111 Mw and which were emitted from stacks of heights between 21 and 183 m. The two formulae are found to correlate the data equally well over all values of the stack exit and meteorological parameters, provided only that the bulk mean velocity of the stack gases exceeds the mean wind speed by at least 20%. The ratio of observed to calculated plume rise is found to be distributed log normally about the mean value. The median rise at large distances d...

Calibration of laser fluorescence measurements of lubricant film thickness in engines

A laser fluorescent diagnostic method was employed to measure lubricant film thickness on the cylinder wall/piston interface of two engines

Differential geometry and the forming of aligned fibre composites

Abstract In this paper it is shown that certain aspects of the forming of aligned fibre composites into complex shapes can be treated as a mapping problem. By application of differential geometry theory we show that the required in-plane shear to form an ideal complex shape is related to part curvature and the initial fibre placement. In order to draw fibre mappings for various complex shaped parts we present several new algorithms which are used with existing computer-aided design software. A particularly powerful aspect of the algorithm allows complex curvature parts to be approximated using flat facets. Finally, results from room temperature forming experiments are given which demonstrate broad agreement with theory, and a specific correlation between the calculated ideal in-plane shear and the observed fibre misalignment.