Colin J. Apelt

Computation of wind flows over three-dimensional buildings

Abstract A computer program has been developed to compute turbulent flows over three-dimensional rectangular surface-mounted bluff bodies and the results have been applied to wind flows over buildings. The program solves the steady-state Reynolds equation using a κ—ϵ model of turbulence. The resulting differential equations are solved by the use of the SIMPLE algorithm. Four flows have been studied and the computed results compared with full scale and wind tunnel measurements carried out by others. Good agreement has been obtained in most cases.

Simulation of flow past a cube in a turbulent boundary layer

This paper considers the flow over a surface-mounted cube placed in a turbulent boundary layer. The flow is considered to be incompressible and one face of the cube is set perpendicular to the approach flow direction. This flow is simulated on computer by the solution of the Reynolds equation and continuity equation with the help of a k−ϵ model of turbulence. Computed predictions are compared with experimental measurements. A very good level of agreement is obtained for mean pressures and velocities in the vicinity of the cube, and adequate agreement is obtained for velocity fluctuations.

Application of a Boussinesq model for the computation of breaking waves - Part 2: Wave-induced setdown and setup on a submerged coral reef

In continuation of a recent companion paper (Skotner, C., Apelt, C.J., Application of a Boussinesq model for the computation of breaking waves. Part 1: Development and verification. Ocean Eng., in press) describing the development of a set of Boussinesq equations that can be used to study the transformation of waves before, during and after wave breaking provided the bed slope is relatively gentle, the present paper presents new data and tests the ability of the developed model to compute wave-induced setdown and setup of regular waves propagating onto a submerged coral reef consisting of relatively steeper slopes. This is done by comparison with new laboratory measurements conducted in a closed wave flume. The results show that the model computes accurately the setdown and setup of regular waves of small incident wave height but there is a tendency to underestimate the wave setup as the incident wave height increases.

The aerodynamic disturbance caused by the free-ends of a circular cylinder immersed in a uniform flow

The disturbances caused by the free-ends of a smooth, circular cylinder immersed in a low-turbulence, steady, uniform flow have been determined. The cylinder was sufficiently long to include an undisturbed central section separating the two interference regions and was treated as two cantilevers springing from the plane of symmetry at the centre of the span. Measurements were made of mean and fluctuating surface pressures, local mean pressure drag, r.m.s. lift and r.m.s. drag and Strouhal number of vortex shedding, at an upper subcritical Reynolds number of 4.4 × 104. Oil-flow visualization was performed on the surface of the cylinder. The results reveal the nature of the disturbance to vortex shedding within the interference region, which was found to extend to a distance of 20 cylinder diameters from the free-end.

Correlations for mine tailings consolidation parameters

ABSTRACT Because of the excessive time required for the determination of the compressibility and permeability of fine mine tailings, estimates of the volume required for the storage of such tailings are often based on very limited data. Correlations based on the index properties of mine tailings are presented that enable reliable estimates of the required parameters to be obtained rapidly. The index properties themselves may be determined within a week using small quantities of tailings. The correlations are based on data for disparate types of tailings and a variety of test methods. They are thus applicable to most mine tailings, but must be applied with caution to tailings in which chemical bonding may curtail consolidation or that contain significant quantities of relatively coarse particles or clays with fibrous particles.

Application of a Boussinesq model for the computation of breaking waves. Part 1 : Development and verification

Based on a set of Boussinesq-type equations with improved linear frequency dispersion characteristics in deeper water, the present paper incorporates the simplified effect of spilling wave breaking into the equations. The analysis is restricted to a single horizontal dimension but the method can be extended to include the second horizontal dimension. Inside the surf zone the vertical variation of the horizontal velocity profile is assumed to be composed of an (initially unknown) organised velocity component below the roller and a surface roller travelling with the wave celerity. This leads to a new set of equations which is capable of simulating the transformation of waves before, during and after wave breaking. The model is calibrated and verified by comparison with several wave flume measurements. The results show that the model produces sound physical results.

Internal wave generation in an improved two-dimensional Boussinesq model

A set of Boussinesq-type equations with improved linear frequency dispersion in deeper water is solved numerically using a fourth order accurate predictor-corrector method. The model can be used to simulate the evolution of relatively long, weakly nonlinear waves in water of constant or variable depth provided the bed slope is of the same order of magnitude as the frequency dispersion parameter. By performing a linearized stability analysis, the phase and amplitude portraits of the numerical schemes are quantified, providing important information on practical grid resolutions in time and space. In contrast to previous models of the same kind, the incident wave field is generated inside the fluid domain by considering the scattered wave field in one part of the fluid domain and the total wave field in the other. Consequently, waves leaving the fluid domain are absorbed almost perfectly in the boundary regions by employment of damping terms in the mass and momentum equations. Additionally, the form of the incident regular wave field is computed by a Fourier approximation method which satisfies the governing equations accurately in water of constant depth. Since the Fourier approximation method requires an Eulerian mean current below wave trough level or a net mass transport velocity to be specified, the method can be used to study the interaction of waves and currents in closed as well as open basins. Several computational examples are given. These illustrate the potential of the wave generation method and the capability of the developed model.

The application of wave induced forces to a two-dimensional finite element long wave hydrodynamic model

This paper describes the modification of a two-dimensional finite element long wave hydrodynamic model in order to predict the net current and water levels attributable to the influences of waves. Tests examine the effects of the application of wave induced forces, including comparisons to a physical experiment. An example of a real river system is presented with comparisons to measured data, which demonstrate the importance of simulating the combined effects of tides and waves upon hydrodynamic behavior.