Search

A new method is proposed to correct shallow-water model resistance tests for the effect of the tank side walls, i.e. to correct the resistance curve towards shallow water of infinite width. From computed flow fields along ships in shallow water and channels, the tank or channel walls are found to increase the overspeed along the ship (return flow) by an amount that is roughly constant over the channel section. An algebraic equation is derived from which this amount can be solved, using a volume flux derived from a single potential-flow computation. The effect of the tank walls on the resistance curve is represented by a speed shift corresponding with this overspeed. The assumptions made are checked against computed flow fields and resistances. The overspeed increment is very well predicted; its effect on the resistance is fairly well estimated as long as it is not too strong. The method, in routine use for shallow-water tests at MARIN, is most practical; and in view of the large tank wall effects in shallow water, it is essential for good predictions.

This paper addresses shallow-water ship model testing, and the determination of water depth effects on ship resistance. It is shown how effects of water depth, towing tank width, and the scaling of viscous resistance interact, and are of large importance for ship performance prediction. A new method to correct model tests for tank width effects is briefly described. For a set of shallow-water model-test data, it is shown how tank width effects apparently double the water depth influence. Also the model-to-ship extrapolation strongly affects the predicted water depth effect for the ship, easily leading to an overestimation. The procedure to be used, with a depth-dependent form factor, is proposed. A new procedure to correct ship speed trials for water-depth effects is introduced, and validations are shown with full-scale trial data, with the same set of model-test data and with the full-scale predictions based on these.

A practical and efficient system is described for ship hull form optimisation and its application for minimising wave resistance. Parametric hull form deformations are defined in a CAD system, specific for the case considered and related with flow aspects to be addressed. Surrogate-based global optimisation is applied for multi-objective problems, such as optimisation for a ship’s operational profile.

This paper discusses a rational and systematic procedure for understanding and analysing steady ship wave patterns and their dependence on hull form. A stepwise procedure is proposed in which the pressure distribution around the hull is invoked to provide a qualitative understanding of the connection between hull form and wave making. In a recent publication it was shown how this understanding explains various known trends and, in combination with wave pattern computations by free-surface potential flow or Reynolds-averaged Navier–Stokes (RANS) methods, can often be exploited to reduce wave making by modifying the hull form. The present paper provides support for the guidelines given, validates the decomposition into different steps and indicates the connection with previous theoretical approaches.

Methamphetamine use is a growing threat to small rural communities in Western North Carolina. As clandestine labs with their toxic by products flourish, increasing numbers of teenagers are seen in the local emergency departments with symptoms of acute methamphetamine intoxication. Research points to the potential long-term damage likely to be suffered by individuals and the community from this methamphetamine epidemic. It is becoming clear that control efforts are costly and substance abuse treatment for a developed addiction is often ineffective and needs to be repeated. As with most public health threats, there is growing recognition that the problem is best addressed through early intervention. It is suggested that the development of an intensive effort targeting middle school children and their parents, strengthening parent-child bonds and communicating a strong non-use message may be an effective strategy in the prevention of initial experimentation with methamphetamine in adolescence.