ABSTRACT:

It is well known that sand transport occurs on a sand bottom when water flows over it with a velocity above a certain level. This fact may cause scours around structures placed on sea or river bottoms. The flow over a flat surface with a parallel placed circular cylinder has been investigated experimentally performing some wind tunnel tests, in order to increase our knowledge on this phenomenon. Hence, surface pressure distributions on the cylinder and the flat surface have been obtained in addition to surface flow visualization. These tests have been performed in the cases of different gaps between cylinder and flat surface (including zero gap).

INTRODUCTION

Circular cylindrical structures such as marine pipelines are used for disposal of industrial and municipal wastewater into the sea, for cooling water in nuclear power plants, and for the transformation of gas and crude oil from offshore platforms. Marine cables, on the other hand, are increasingly used for communication. Design of marine pipelines and marine cables are rather complicated problem. One of the factors which needs to be taken into consideration, in the design process is the scour around the pipeline. The scour around the pipeline is caused by the presence of the pipeline itself due to wave and/or current effect. This problem due to the effect of the close proximity of a circular cylinder on flow over a flat surface is of fundamental interest as well as being important in many engineering applications. A large volume of knowledge has been accumulated on the subject during the last decade. Many researchers have tried to understand flow pattern around the cylinders. For various gap values, they measured the mean pressure distribution around the cylinder and along the wall and the velocity fluctuations by means of a hot wire anemometer.

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