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(1973)ReportA detailed study on the optimisation of the parameter values of the Boughton daily rainfall-runoff model. Optimum values were sought using the Steepest descent, Simplex and Davidson optimising methods. It had been intended to correlate these optimum parameter values with measurable catchment characteristics. Rapid initial reductions in the values of the objective function were readily achieved and the solutions approached apparent optimum points on the response surface. However several of these points were found for each catchment and there were large differences in the parameter values between points. It was found that further improvements in the objective function could usually be achieved by using another of the search techniques or by numerical trials, and in this way, downhill paths on the response surface were found from the apparently optimum points. This work was pursued for one of the catchments until the paths appeared to be converging, but coincidence at a true optimum could not be achieved.. A number of somewhat different sets of parameter values which appeared to lie in a flat "valley" area of the response service were obtained, and these sets gave equally good fits to the observed runoff data. An algebriac analysis of the of the operation of the model and of the effect on the objective function of changes in some individual parameter values led to important findings on some of the problems encountered. It is probable that the findings from the algebriac and numerical analyses would be applicable to the rainfall-runoff models.
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(1973)ReportStudy of traditional patterns of water use. Data reported for the Raiapu Enga clan in the Saka Valley near Wapenamanda in the Western Highlands. Regional and environment and culture briefly described. Attitudes to water, including fear of poison,, female contamination. Sources are natural streams, rivers and springs. Rainwater also in the wet season. Pollution status varies from relatively clean to human and porcine faecal material. Water is collected in late afternoons in gourds, bamboos, tins and cooking pots, for which the average return journey takes 12.5 minutes. Each domestic group collects 2.46 liters a day of which 79% is drunk. The rest is used for cooking food (for humans and pigs), drinking for dogs, pigs and chickens, washing utensils, and discarded. Total per capita use is 0.68 litres per day. On average 0.54 litres are drunk daily and, including the water both contained in food and caused by food oxidation. 2.4 litres per day are available to the body. Per capita use decreases with increasing size of domestic group: travel time to source has no association with water use patterns. Major non-domestic uses of water include coffee washing and growing the reed-like plant Kuta from which women's aprons are made.
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(1973)ReportThe mechanism of suspension of a non-buoyant particle in a turbulent flow has been examined from the viewpoint of the history of an individual particle. A program developed to compute trajectories of a non-buoyant particle within a field of eddies. The trajectories indicate that a particle may be suspended indefinitely within an individual eddy of the eddy field or may fall through the eddy field with a fall velocity which differs from the settling velocity of the particle in the quiscent fluid. The quantitative results are specific to the particular conditions examined. In a flow in which the net vertical flow of the fluid is zero, the time averaged fall velocity of a non-buoyant particle may differ from the settling velocity of the particle in the quiescent fluid and may be reduced to zero. In a series of experiments, rates of entrainment of fluids across a density discontinuity between two fluid layers have been measured. In these experiments, the turbulent flow of a fluid layer has been simulated by the motion induced by an oscillating grid. Density discontinuities due to temperature differences, salinity differences and the presence in one layer of suspended particles have been examined. The measured entrainment rates are consistent with the hypothesis that under given conditions the rate of entrainment is dependent upon the molecular diffusitivity of the property causing the the density discontinuity
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(1974)ReportThe efficiency of programmable and manual methods of finding the shortest spanning tree of a graph is investigated. Incomplete connecting graphs are the main concern. Computer programs for three methods are included.
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(1970)ReportFour principal topics: groundwater from unconsolidated sediments, groundwater recharge, digital and analog models in groundwater investigations, conjunctive use of surface and groundwater.
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(1970)ReportHere the method used by Wood (1968, 1970) is extended to cover the case of the flow of a stably layered fluid from a reservoir through a contraction with a round crested weir at its min imum width. The conditions under which a single layer may be separated form a two layer system by having this lighter layer alone flowing over a weir are first examined. The conditions under which two layers continuously decrease in depth from the reservoir to and downstream of the weir are determined. It is shown that in this case the theory involves computations not only at the section of minimum width but also a section upstream of this point (the virtual point of control). For a weir shape, chosen so as to simplify the algebra, complete solutions are obtained. For the case of the flow of single layer, the depth of flow over the weir depends only on the depth of the upstream layer, and is two thirds of that depth. For the two layer system it is shown that the depth of the layers over the weir depend not only on the depth updtream but also on the width of the crest and indirectly on the geometry of the crest and the contraction. Some simple experiments were carried out to verify the major conclusions of this theory. The method presented should have applications in predicting flow in numerous engineering fields where more than one layer is flowing and where viscous effects are likely to be small.
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(1970)ReportExamines the rapidly varied flow phenomenon in a two layer density stratified system. Only one layer flows, the other being stationary. The flow regime changes from supercritical to subcritical across the region of rapidly varied flow. The analogous phenomenon in open channel hydraulics is the hydraulic jump. In stratified flows it will be referred to as a density jump because it is generally accompanied by a change in the density of the flowing layer. It is shown there is a fundamental difference between the hydraulic and the density jump in that the conjugate conditions on either side of a density jump are not uniquely related as they are with the hydraulic jump. There are a range of possible states which may be attained downstream of a density jump for a given upstream state. It is shown that the rate of entrainment of ambient fluid into a density jump and therefore the conditions downstream of the jump are a function of the downstream control. The limiting cases of maximum and minimum entrainment and control mechanisms within the jump are examined. Several forms of control are investigated among these being the broad crested weir, a free overfall and channel friction. An entrainment function is derived, relating a local entrainment parameter to a local Froude number within the entraining zone of a density jump. Some features of unsteady density flows are examined and it is shown that all the properties of strarting flow or nose are controlled by the following layer, which in turn is generally controlled by boundary friction. An approximate expression is derived for the fall in momentum flux across a density jump and this is compared with experimental data. Finally, experimental velocity and density distributions downstream of density jumps are presented, and are shown to be functions of the Froude number of the flow upstream of the density jump, and the rate of entrainment within the jump. The significant result arising from this work is that conditions downstream of density jump which will occur, for example, at power station cooling pond outfalls and some ocean sewage outfalls, can be predicted. A design example, showing how station cooling pond efficiencies can be optimised by the control of mixing at the outfall, is included in the appendices.
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(1970)ReportWithin a background of dispersion of fine sediments injected by liquid transport, this survey reviews existing theories and data preparatory to work on interface behaviour in disposal. 1. Introduction, definitions, description and phenomena. 2. Physics of flow of density currents. 3. Turbidity currents as agents for transportation of solid granular materials. 4. Density and turbidity currents in the specialised environment of the ocean.