|
چکیده
|
Nowadays, considering the importance of the energy and speed in the world as well as the limited available energy, the optimum condition should be always considered in designing. In the field of marine industry, considering the length of the water constraints of our country and special strategic situation of the region, there should be an ongoing attempt to reduce energy consumption and increase speed of the high speed crafts. In this research, nature has been used as a guide to reach our target. Study of the skin of the fast marine’s faunas such as sharks and dolphins, has generated the idea of riblet covered surfaces. Among various methods of the friction drag reduction, the use of riblets and micro-surfaces are more suitable to use on large vessels in terms of their practicality and their mechanism of drag reduction. Here, drag reduction using riblets has been investigated in three phases, fully immersed in water, floating in the air and in the two-phase conditions comprising water and air fluids. There are very few numerical studies about riblets. Therefore, in this research, riblets has been simulated using the software to study their performance. Various riblet surfaces made in the world and currently used has been studied and ANSYS-CFX has been used to study their performance. There are three types of riblets that has been experimented in different laboratories around the world including sawtooth, scalloped and blade of which the results are available. The results has been validated with the experimental results performed in the towing tank. The effects of the shape of riblets on the hydrodynamic parameters are presented. Then, different methods of constructing riblet covered surfaces has been investigated and the possibility of their construction in our country has been evaluated. 3-D printing and micro-particles moulding are among construction methods of riblet covered surfaes which has been investigated in this project. Based on the obtained results, rible
|