This paper aims to perform a numerical analysis of application effects of a superhydrophobic paint by completely coating the blades of a model-scale marine propeller in order to make it a superhydrophobic surface (SHS). First, a two-dimensional study was conducted. Two foils were analyzed for several hydrophobic conditions, varying the slip length. Pressure and skin friction distributions were shown. There is an increase of lift-to-drag ratio with hydrophobicity, but followed by an increase in suction pressure. In three-dimensional case, a propeller was simulated for several hydrophobic conditions, comparing thrust, torque and efficiency coefficients and pressure and friction distribution. Results with propeller showed that an increase in slip length is not always followed by an increase in efficiency, with an apparent efficiency gain limit. For the imposed simulation conditions, from the limit of gain, efficiency no longer increases with hydrophobicity, but its area of low pressure continues to grow.
The large-scale presence of debris is a recurrent issue in the Madeira River, located on Amazon rainforest, North of Brazil, and it is a major concern for the Santo Antonio hydropower plant, located at this region. In order to avoid the abundant amount of debris, floating structures called log booms are installed across the river to retain and deflect them. This paper aims to present the methods used to investigate the structural characteristics of a truncated scale model of a log boom line, through water proof strain-gauges and load cells in hydrodynamic experiments. For that, the model was towed along the model basin of the Institute for Technological Research and wooden scale logs were included to simulate the log jam phenomenon. The paper covers experiment methods, from model design to setting of data acquisition devices and system, characteristics of the experimental runs, and further data analysis. The influence of the scale debris on the structural elements are presented, which can leads to develop a correlation model to scale the fluid-structure interactions in the real prototype.
Debris containment grid is an important part of hydroelectric power plant, since it retains objects, preventing damage to the turbine. In the case of the Santo Antonio hydropower plant, located in the Amazon rainforest, in the north of Brazil, the most significant debris are logs. This paper aims to analyze the interaction between several log boom modules (type of debris containment grids developed specifically for containing logs) present in a debris containment line present in Santo Antonio hydropower plant, as well as its interactions with the fluid, varying the advance velocity and side-slip angle. The analysis of the fluid-body interaction is performed using CFD software with Finite Volume Method approach. The problem is divided into steps. Firstly, one log boom module is simulated with several velocities and side-slip flow angle, obtaining a relation between forces, moments and movements. Next, in order to save the expected computational cost, the module is analyzed and compared through the porosity approach. Finally, the analysis of a line with several log boom modules, including the interaction between each module, is carried out. The results of the simulations will allow to perform an analysis of the line stability, obtaining the forces, moments and movements of each log boom module, observing its influence in the log boom line. With a fluid-body hydrodynamic analysis of several modules in a line, data are provided for a structural analysis. Since the porosity approach is used to reduce the computational cost, this paper also contributes to similar cases, with a main interest in larger scales of forces and movements.
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