Experimental investigation of the scour patterns of the porous group cylinders configured in tripod arrangement for sea structures

Population growth rate of the world has increased because of mankind's exploration of agriculture and adopt a sedentary life. Thanks to population growth, have accelerated scientific discoveries and humanity come those days. Due to industrial revolution actualized in the recent past population growth rate has increased even more and industrial revolution led to energy requirement. At first, energy requirements supplied by fossil fuel based coal and petroleum but increasing number of industrial facilities and fast moving industry caused lack on energy. Energy has become one of our biggest needs today. With the development of technology and industry, the energy needs of world countries and our country are increasing day by day. Many of countries supply with energy needs self resources and import the other countries. This increase leads countries to search for new energy sources. However, increasing environmental pollution and increasing population in our world direct us to search for clean renewable energy sources. In this context, technologies have been developed and are currently being used to generate energy from the sun and wind, which are renewable energy sources. Some world countries have invested and are still making serious investments in clean energy resources. One of the renewable energy resources used in the oceans or seaside countries is the open sea wind fields. In practice can use many differents wind turbine foundation types. First of this foundation types is monopile type. Monopile type foundation is used to up to 30 meters water depths and 1-2 mW power production. The other one of this foundation types is gravity foundation type. Gravity foundation type is used to up to 30 meters like monopile type. Currently used on most offshore wind projects, the gravity foundation consists of a large base constructed from either concrete or steel which rests on the seabed. The turbine is dependent on gravity to remain erect. Another offshore wind turbine foundation type is jacket type. Jacket type foundation is used to 30 - 45 meters water depths. Unlike all of this foundation types, floating foundation types is used deeper water lke 50 meters and over. The other one of the foundation systems used in wind farms established in open seas is tripod leg system.Tripod foundation system can use up to 35 meters water depths. In case of tripod systems installed in practice, the dominant flow/current direction of the local and global scour is formed around the porous systems was investigated in the light of how the density of the porous cylinders and the arrangement of the cylinders changed according to the layout configuration. The channel where the experiments were conducted is 26.00 meters in length, 0.98 meters in width and 0.85 meters in depth. The cylinders were placed and the scour patterns were detected during the experiments. For this purpose false ded was formed by laying sand with a thickness of 0.20 meters. In the experiments, solid cylinders of the same diameter as the porous cylinders were used initially as reference case. The distance from each center of each cylinder to the other is adjusted in the shape of equilateral triangle to be 4D at the center and fixed to the sand bed and tested for two current directions. The current directions are equilateral triangle, the height of the triangle is parallel to the direction of flow of a cylinder, and the triangle edges of the other two cylinders are placed in the sand bed so that the flow is perpendicular. This bird flight is referred to as direction 1. Current direction 2 is the current direction 1 rotated 180 °. The current flowing in current direction 2 is initially set to meet the current perpendicular to the edge. During the experiments, after scouring procuess for 8 hours, the eroded bed was scanned with a laser scanner to obtain information on the depths of scour, depth of material transport and quantities in the sand bed. Once the experiments completed, the same experiments were repeated for groups of cylinders in medium density and low density provided that the distance between the cylinders remains constant. After each test, the channel was drained very slowly again, the test results were noted by scanning. After the first 6 experiments are completed in this way, the experimental setup were reproduced first for the medium density cylinder group as the distance between the cylinders is 3D and 2D respectively. The results for the same direction currents and for cylinders of the same intensity were compared with each other, from the data obtained as a result of the experiments. According to these results, it was seen that for different groups of porous cylinders placed at the same distance, the cylinder density decreased and the amount of scour and the amount of material transport decreased. For cylinders of the same density, the change in flow direction changed the current in the tripod foot, which caused the scoring traces behind the porous cylinder group to change. If the distance between the cylinders decrease, the interaction between the cylinders increase and the scour pattern behind the obstacle exhibit dramatic changes.