1048 Mathematical and Computer Modelling Reports

AppL murlt. Modding Vol. I I, pp 364370, I987

A TWO-DIMENSIONAL TIME-DEPENDENT MODEL FOR SURFACE SHEAR AND

BUOYANCY-DRIVEN FLOWS IN DOMAINS WITH LARGE ASPECT RATIO

SLMON K. SINHA and SUBRATA~ENGUPTA

Department of Mechanical Engineering, University of Miami, Coral Gables, FL 33124, U.S.A.

Abstract-A two-dimensional numerical model has been developed for studying flows in enclosures having a large length-to-depth ratio. The model solves the two-dimensional Navier-Stokes and energy equations subject to hydrostatic, Boussinesq, and rigid-lid assumptions. Turbulent momentum and heat diffusion are incorporated using variable eddy coefficients. The flow is driven by surface wind shear and heat transfer. Two cases were run for a rectangular domain, subject to a suddenly imposed surface shear stress while the surface and bottom were mainained at two different but constant temperatures. The difference between the cases was the formulation used for predicting the eddy viscosities and diffusivities. The variations of velocities and :emperatures with time were studied. Both velocities and temperatures were found to undergo a sudden rapid change, after an initial period of slow change. before attaining steady state. This has been explained in light of the differences in the convective and diffusive time scales and the nature of coupling between the governing equations.

Key Maor&-Environmental flows

Appl. malh Modding Vol I I. pp. 389-392. 1987

INCREMENTAL STOCHASTIC MODEL FOR THE TEMPORAL DISTRIBUTION OF PEAK TRAFFIC

DEMAND

ATTAHIRU SULE ALFA

Transport Institute and Department of Civil Engineering, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada

Abstract-This paper presents the incremental stochastic user equilibrium (ISUE) model for predicting how travellers select their departure times from an origin in a single origin-destination pair system if they have desired times of arrival at the destination. The temporal distribution of the peak traffic is the result of commuters’ selections of departure times. The stochastic user equilibrium (SUE) model is one of the techniques for estimating this distribution, but is computationally cumbersome to apply. In addition, existence and uniqueness of the solution to the SUE formulation and its approximations have not been proven. The ISUE is another approximation to the SUE, and it is based on an approach for which existence and uniqueness of the solution have been established.

Key Words-Peak traffic demand, stochastic model

J. Op/ Rex. So<. Vo,. 38. No IO. pp. 891498. 1987

MODELLING TECHNIQUES FOR SIMULATION OF SUBMARINE ENGAGEMENTS

B. M. KNAPP,’ A. R. DLJDLEY* and J. S. RYDER’

‘EASAMS Ltd, Camberley, Surrey, U.K.

2Admiralty Research Establishment, Portland, Dorset, U.K

Abstract-The process of designing complex, costly military systems benefits substantially from analyses of performance as predicted by some form of mode1 of the system and its operating environment. In this paper, techniques are described that have been implemented in a suite of computer programs to represent