Numerical simulation of smart hydrofoil in marine system M.H. Djavareshkian a,n , A. Esmaeili a , A. Parsania b a Ferdowsi University of Mashhad, Iran b Department of Mechanical Engineering, Payame Noor University, Tehran 19395-3697, Iran article info Article history: Received 14 July 2012 Accepted 13 July 2013 Available online 24 August 2013 Keywords: Smart shape Hydrodynamic coefficients Hydrofoil Wave Trochoid abstract A pressure-based implicit finite-volume technique is used to solve the Navier–Stocks equation, simulating flow around a smart hydrofoil. The Volume of Fraction (VOF) method is applied to track the free surface. This simulation focuses two main goals. Initially, the equation of a free surface wave, generated by the moving submerge hydrofoil, is extracted, and the wavelength and amplitude of the wave are assessed in the different submerge distances (h/c) and angle of flap (AOF). It is found that the trochoid equation predicts the free surface wave very well. Secondly, the simulation of fluid flow around the smart hydrofoil is performed, and its results are compared with the conventional hydrofoil. For both hydrofoils (smart and conventional), the effect of submerge distance and flap angle is evaluated. The results indicate that smart hydrofoils produce higher lift to drag ratio (L/D) than that of the conventional ones. Besides, the wave amplitude of smart hydrofoil is greater than conventional ones. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Many smart aerodynamics and hydrodynamics configurations are still at the research and development stage, and their further commercial development depends on potential applications. They may provide solutions to existing problems or advanced techno- logical possibilities that would otherwise not be feasible. Some smart configuration applications already exist in the aerodynamics of an airplane's wing (Bolonkin and Gilyard, 1999; Pern and Jacob, 1999; Campanile and Anders, 2005; Chinnasamy, 2006; Matsuzaki and Torii, 2006; Majji et al., 2007; Abdullah et al., 2009, 2010; Wickramasinghe et al., 2009). However, several studies are done to apply smart shape in the helicopter's blades (Anusonti-Inthra et al., 2005; Tiseo and Koopmann, 2006). Moreover, the aerody- namic of smart spoiler in racecar is performed (Djavareshkian and Esmaeli, 2012). Another application of smart structure can be considered in the aerodynamic of Wing in Ground vehicles (WIG) (M. Djavareshkian et al., 2011; M.H. Djavareshkian et al., 2011). Consequently, applied smart shape in the wind turbine is illu- strated powerful influence on the aerodynamic performance (Barlas and Van Kuik, 2010). Therefore, almost all previous investigations have confirmed the beneficial implementation of smart configurations and have more experience of smart shapes that could be adapted for marine applications. On the other hand, hydrofoils are widely utilized on ships and marine vehicles; furthermore, hydrofoil performance plays a significant role in the design of the vehicles. Therefore, increasing the performance can be affected on the ships and marine vehicles abilities (Kouh et al., 2002; Xie and Vassalos, 2007). Many ways and techniques can be utilized to increase hydrofoil performance. One of them is employing different optimization algorithms such as Neural Networks and Lagrange multiplier method (Schmitz et al., 2004; Hsin et al., 2006; Yang et al., 2009). Having high performance, the optimized hydrofoil can be worked in a special condition, and the change of mentioned condition causes to reduce the hydrofoil abilities. Therefore, to achieve maximum performance in all states, the shape of hydrofoil should be adapted, and it just becomes possible by using smart configurations in the hydrofoil surfaces. Up to now, using smart configurations in the marine vehicles is performed by Rediniotis et al. (1997, 2002), Quackenbush et al. (2005), Ming et al. (2009), and Wang et al. (2008). So far, the smart flap, which is applied smart structure as a hydrofoil's flap, is not considered, especially close to the water surface. In this study, the hydrodynamic effects of using smart design in the hydrofoil's flap surfaces are numerically studied in which the hydrofoil moves near the water free surface. The smart hydrofoil is deflecting like fish body. Then, the comparison of smart and conventional flaps is numerically done. The effect of submerge distance and angle of the flap is performed, too. Another novelty of this paper is that the free surface wave equation is achieved, and the relationship between wavelength and amplitude of the wave is obtained for both hydrofoils (smart and conventional), various submerge distances and AOFs. Finally, a new equation for water wave is suggested, and its accuracy is studied. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/oceaneng Ocean Engineering 0029-8018/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.oceaneng.2013.07.015 n Corresponding author. Tel.: +98 511 8615100; fax: +98 511 8436432. E-mail addresses: javareshkian@ferdowsi.um.ac.ir (M.H. Djavareshkian), aliesmaeli30316@yahoo.com (A. Esmaeili), a.parsania@farspnu.ac.ir (A. Parsania). Ocean Engineering 73 (2013) 16–24