A major safety concern in pressurized-water-reactor (PWR) design is the loss-of-coolant accident (LOCA), in which a break in the primary coolant circuit leads to depressurization, boiling of the coolant, consequent reduced cooling of the reactor core, and, unless remedial measures are taken, overheating of the fuel rods. This concern has led to the development of several computer models for safety analysis, the validity of which can be assessed only after their accuracy and sensitivity have been subjected to parametric studies, such as: nodalization studies to ensure grid-independency of the results; investigation of alternative empirical input, such as heat-transfer representations, choice of flow regimes, etc., and the representation of stratified two-phase flow in the horizontal pipes. This paper presents such parametric studies for a postulated PWR accident. The results are presented and discussed. It is concluded that the predictions are significantly affected by the number of grid nodes used, by the chosen heat-transfer and interphase friction correlations and by the modelling of stratified two-phase flow in horizontal pipes. Such sensitivities may, it is suggested, be exhibited by other LOCA simulations.

The paper discusses the limitations of current practices of evaluating thermal performance of wet cooling towers and describes a more advanced mathematical model for mechanical and natural draft cooling towers. The mathematical model computes the two-dimensional distributions of: air velocity (two components); temperature, pressure, and moisture content; and water temperature. The downward direction of water flow is presumed. The local interphase heat and mass transfer rates are calculated from empirical correlations for which two options are provided. In the first option, only one constant (Ka, based on Merkel’s approximations) is employed; in the second option, two separate constants for heat and mass transfer are used. Boundary conditions can be either of the prescribed cooling range or of the prescribed hot water temperature types. The governing equations are solved by a finite difference method. The model is embodied into a computer code (VERA2D) which is applicable for the natural and mechanical draft towers of both the crossflow and counterflow arrangements. Several applications of the code are described in Part II of the paper.

A model for predicting physical characteristics of combustion in the recirculating, chemically-reacting flow in the base region of a rocket exhaust plume is described. The nozzle jet and the free stream are considered as supersonic or subsonic, mixing turbulently to form an axisymmetric and compressible free-boundary layer. The turbulence is accounted for by a two-equation model, which solves the transport equations for the local kinetic energy of the fluctuating motion and its dissipation rate. Full account is taken of heat-transfer effects, and a detailed finite-rate chemical-kinetics scheme is included, which allows for any number of species. Simultaneous solutions of the elliptic differential equations are obtained by a finite-difference technique, and the chemical-kinetic equations are solved by a procedure developed by Pratt and Wormeck (1976). The prediction procedure, composed of the mathematical model and its solution algorithm, is applied to predict the helds of variables for representative supersonic-missile flight conditions, with subsonic recirculating base-flow, and a full description of the chemistry. The results are presented and discussed.

The ESCIMO theory of turbulent combustion is applied to the hydrogen~air diffusion flame, with the following simplifications: o (1) the reaction is laminar-diffusion controlled within the “fold”; (2) fold properties depend upon age alone, at a given point in the flame; (3) fold properties at “birth” can be deduced by tracing upstream along a line of constant mean fuel-air ratio; (4) fold-birth rate is proportional to entrainment rate, distributed in specified ways across thejet; (5) fold size at birth is proportional to local jet width; and (6) the fold-stretching rate is proportional to the average velocity gradient in the mean flow along the postulated trajectory. Comparisons with the experimental data reported earlier by Kent and Bilger lead to the conclusions: o (i) the agreement in respect of hydrodynamic features is good; (ii) suitable choice of input parameters permits the experimental data for unmixedness tobe fitted fairly well; (iii) allowance for “intermittency” should be made in future work.

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Numerical predictions are presented for the motion and distortion of a single gas bubble rising through the liquid. The computations were made with an implicit finite-difference procedure which solves the transient equations of motion throughout the bubble and the liquid, such that the free surface between the gas bubble and the liquid is not a boundary of the computational domain.

Evaluation of seismic reflection data has identified the presence of fluid escape structures cross-cutting overburden stratigraphy within sedimentary basins globally. Seismically-imaged chimneys/pipes are considered to be possible pathways for fluid flow, which may hydraulically connect deeper strata to the seabed. The properties of fluid migration pathways through the overburden must be constrained to enable secure, long-term subsurface carbon dioxide (CO2) storage. We have investigated a site of natural active fluid escape in the North Sea, the Scanner pockmark complex, to determine the physical characteristics of focused fluid conduits, and how they control fluid flow. Here we show that a multi-scale, multi-disciplinary experimental approach is required for complete characterisation of fluid escape structures. Geophysical techniques are necessary to resolve fracture geometry and subsurface structure (e.g., multi-frequency seismics) and physical parameters of sediments (e.g., controlled source electromagnetics) across a wide range of length scales (m to km). At smaller (mm to cm) scales, sediment cores were sampled directly and their physical and chemical properties assessed using laboratory-based methods. Numerical modelling approaches bridge the resolution gap, though their validity is dependent on calibration and constraint from field and laboratory experimental data. Further, time-lapse seismic and acoustic methods capable of resolving temporal changes are key for determining fluid flux. Future optimisation of experiment resource use may be facilitated by the installation of permanent seabed infrastructure, and replacement of manual data processing with automated workflows. This study can be used to inform measurement, monitoring and verification workflows that will assist policymaking, regulation, and best practice for CO2 subsurface storage operations.

This paper is concerned with the prediction of three-dimensional turbulent flows around bodies of arbitrary shape, with particular emphasis on a ship's hull. Two solution methods are compared employing a non-orthogonal coordinate system, in which the surface of the body is arranged to coincide with a coordinate surface. The velocity components are solved for the axial, radial and circumferential components in the cylindrical-polar system from which the non-orthogonal coordinates are derived. The partial-differential equations governing the flows under consideration are solved by two finite-difference methods for three-dimensional, parabolic1and partially-parabolic2flows. Turbulence is accounted for through a two-equation model of turbulence developed by Harlow and Nakayama3and modelled by Launder and Spalding.4Solutions are presented for flow around a ship's hull which demonstrate the potential of the present methods.

A general technique for predicting properties of highly turbulent, chemically reacting diffusion flames with regions of recirculating flow and with radial pressure gradients is described. The technique is explicitly written for calculations on low altitude, axisymmetric rocket exhaust flames, but may readily be applied to other combustion systems where coupling between chemical reactions and turbulent mixing processes is strong. The application of the method is illustrated: agreement between results obtained and experimental measurements is good, although more stringent further testing is needed.

Coarse-grid predictions of the steady turbulent flow in a right-angled tee-junction are presented, attention being confined to the cylindrical "horizontal" portion of the tee. The finite-difference forms of the conservation equations of mass and momentum governing the flow in a tee-junction are solved by using a three-dimensional version of the SIMPLE algorithm of Patankar and Spalding. The kinetic-energy and dissipation-rate equations of a model of turbulence are also solved. The predictions show that the calculation procedure is capable of producing physically realistic predictions.