Motion of a cylinder under the surface of a heavy fluid

General equations are derived for the approximate solution of the flow of a heavy infinite depth about a submerged circular cylinder where the center of the cylinder is submerged 1.5 diameter or greater. Then by replacing the cylinder by a dipole of a certain strength an equation is derived for the wave resistance of a circular cylinder moving in a fluid of finite depth

Unsteady effects during resistance tests on a ship model in a towing tank

It is known that there are oscillations in the wave resistance during the constantvelocity phase of a towing-tank resistance test on a ship model. In this work, the unsteady thin-ship resistance theory has been applied to this case. The results have been compared with experiment data obtained using a towing carriage the velocity history of which can be programmed. It is demonstrated here that generally excellent correlation exists between the theory and the experiments. In particular, one can predict the influence of Froude number, rate of acceleration, and type of smoothing of the acceleration on the characteristics of the oscillations. These characteristics include the amplitude, rate of decay, frequency, and phasing of the oscillations in the curve of wave resistance versus time

Plastic Reconstruction of Dehenerative Achilles Tendon Ruptures Using the Bioprosthesis of Xenopericardium

Two methods for the plastic reconstruction of degenerative Achilles tendon ruptures have been developed, using biological xenopericardium prosthetics. 21 patients were operated. In cases of tendon gliding surface deformation, the insulating plastic reconstruction was used in 14 of them by wrapping the suture area with xenopericardium; the replacement plastic reconstruction was applied in 7 patients. In case of an unrecoverable defect, the tendons were replaced with a specially formed prosthesis. The long-term results of the use of xenopericardium prostheses were compared with the traditional methods. The study involved 120 patients, divided into 5 groups according to the type of surgery: the closed perirocous suture of the Achilles tendon (25 patients), the open stitching of the ruptured tendon (28 patients), the plastic tendon by Chernavsky (24 patients), the tendon plastics by the lavsan ribbon (22 patients) and the tendon grafting with xenopericardium bioprostheses (21 patients). The results were evaluated by the method of Leppilahti J. (1998). The results obtained suggest that the application of xenopericardial prosthetics leads to a significant increase in the number of excellent and good results in comparison with the other methods

Long Wave Dynamics along a Convex Bottom

Long linear wave transformation in the basin of varying depth is studied for a case of a convex bottom profile in the framework of one-dimensional shallow water equation. The existence of travelling wave solutions in this geometry and the uniqueness of this wave class is established through construction of a 1:1 transformation of the general 1D wave equation to the analogous wave equation with constant coefficients. The general solution of the Cauchy problem consists of two travelling waves propagating in opposite directions. It is found that generally a zone of a weak current is formed between these two waves. Waves are reflected from the coastline so that their profile is inverted with respect to the calm water surface. Long wave runup on a beach with this profile is studied for sine pulse, KdV soliton and N-wave. Shown is that in certain cases the runup height along the convex profile is considerably larger than for beaches with a linear slope. The analysis of wave reflection from the bottom containing a shallow coastal area of constant depth and a section with the convex profile shows that a transmitted wave always has a sign-variable shape.Comment: Submitted to Journal of Fluid Mechanic