Abstract
Flow around a cylinder has been extensively studied due to its practical importance in engineering; much attention has been devoted to drag reduction and vortex shedding suppression using active and passive control devices. A strong motivation for studying such practical problems come from the fact that large amplitude of lift fluctuation and alternate vortex shedding are generally design concerns for engineers. Several numerical and experimental studies have been devoted for studying flow around a cylinder with a flexible plate attached to its centerline. This investigation has been known to be one of the most successful ways of controlling vortex shedding. Other active device for vortex shedding cycle reduction in order to minimize sound pressure is a cylinder equipped with hairy flaps. Experimental studies of air around a cylinder equipped with hairy flaps show that hairy flaps can reduce the wake deficit by modifying the shedding cycle behind the cylinder. For the modelisation and simulation of such a coupling problem, fluid structure capabilities need to be performed. Fluid structure coupling problems can be solved using different solvers; a monolithic solver and a partitioned process. Monolithic process is a fully implicit method preserving energy at the fluid structure interface. However its implementation is more complex when specific methods are required for both fluid and structure solvers. When efficient fluid and structure software packages are available, a partitioned procedure can be used in order to couple the two codes. The present work is devoted to simulation of fluid structure interaction problems and flow around thin flexible hairy flaps, using a partitioned procedure. One of the main problems encountered in the simulation is the automatic remeshing when the flaps come into contact and the fluid mesh between the flaps undergoes high mesh distortion. . In this paper, numerical simulation has been performed and Strouhal number for two different Reynolds number Re=1.46 10 4 and 1.89 10 4 have been investigated. For both Reynolds number experimental data is available. For comparison with flow around a plain cylinder, numerical simulation were also performed and Strouhal number compared to experimental value
Highlights
Fluid Structure Interaction (FSI) plays a crucial role in design for engineering and manufacturing
For a new product design several numerical and experimental tests need to be performed before getting to production process
Empirical data presented in current tank seismic design codes as Eurocode, are based on simplified assumptions for the geometry and material tank properties and cannot be used for complex geometry
Summary
Fluid Structure Interaction (FSI) plays a crucial role in design for engineering and manufacturing. For a new product design several numerical and experimental tests need to be performed before getting to production process These can be encountered in many engineering applications, where mechanical structures can be subjected to complex flow causing large deformation and damages. From experimental investigation, carried out by Kamps et al [5], results show that, above a certain Reynolds number, the hairy flaps lead to a jump in the vortex shedding frequency This phenomenon is observed in the water flow experiments as a jump in the nondimensional Strouhal number that is related to the change of the shedding cycle. Numerical simulation of this specific problem, including complexities due to presence of very thin flexible hairy flaps, is addressed in this paper for two different Reynolds numbers. As reported in [5], for these Reynolds numbers, the tonal peak due to vortex shedding seems to be shifted to slightly higher frequencies, indicating that the tripping tape merely corresponds to a small increase of the effective cylinder diameter in this Reynolds number range
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