Integrated computational fluid dynamics (CFD) and computational structural dynamics (CSD) simulations of flow over a cylinder with a flexible splitter plate attached to the rear stagnation point, are performed. Flow over a cylinder produces vortex shedding, which causes unsteady pressure and shear stress distributions over a flexible splitter plate. As a result, the flexible splitter plate vibrates with distinct frequencies, which are different from the vortex-shedding frequency and natural frequencies of the plate. A systematic and detailed analysis of the effects of the flexible plate on fluid-structure dynamics and on the drag and lift of the cylinder, is presented.
A computational methodology, which combines a computational fluid dynamics (CFD) technique and a computational structural dynamics (CSD) technique, is employed to design a deformable foil whose kinematics is inspired by the propulsive motion of the fin or the tail of a fish or a cetacean. The unsteady incompressible Navier–Stokes equations are solved using a second-order accurate finite difference method and an immersed-boundary method to effectively impose boundary conditions on complex moving boundaries. A finite element-based structural dynamics solver is employed to compute the deformation of the foil due to interaction with fluid. The integrated CFD–CSD simulation capability is coupled with a surrogate management framework (SMF) for nongradient-based multivariable optimization in order to optimize flapping kinematics and flexibility of the foil. The flapping kinematics is manipulated for a rigid nondeforming foil through the pitching amplitude and the phase angle between heaving and pitching motions. The flexibility is additionally controlled for a flexible deforming foil through the selection of material with a range of Young's modulus. A parametric analysis with respect to pitching amplitude, phase angle, and Young's modulus on propulsion efficiency is presented at Reynolds number of 1100 for the NACA 0012 airfoil.
A computational simulation methodology, which combines a computational fluid dynamics technique and a computational structural dynamics technique, is employed to design a deformable foil of which kinematics is inspired by the propulsive motion of a fin or a tail of fish and cetacean. The unsteady incompressible Navier-Stokes equations are solved using a second-order accurate finite-difference method and an immersed-boundary method to effectively impose boundary conditions on complex moving boundaries. A finite-element-based structural dynamics solver is employed to compute the deformation of the foil due to interaction with fluid. A phase angle between pitching and heaving motions as well as the flexibility of the foil, which is represented by the Youngs modulus are varied to find out how these factors affect the propulsion efficiency.
A newly developed computational methodology for high-fidelity prediction of fluid and structure dynamics and their unsteady interaction is presented. The present methodology combines an immersed-boundary method, which is capable of simulating flow over non-grid-conforming complex moving bodies and a structural dynamics solver, which is based on a finite-element method and is capable of predicting time-accurate dynamics of deforming solid structures. The pressure and velocity of fluid and geometric information of submerged structures are time-accurately coupled through an integration algorithm. The capability of the present computational fluid dynamics (CFD)–computational structure dynamics (CSD) coupling technique is assessed in a number of validation simulations.
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