On the Calculation of a Flapping Flexible Airfoil in the Flow of Viscous Incompressible Fluid
Authors: Dynnikov Y.A. | Published: 08.04.2016 |
Published in issue: #4(673)/2016 | |
Category: Calculation and Design of Machinery | |
Keywords: viscous incompressible fluid, flapping airfoil, hydrodynamics, numerical simulation, flow-structure interaction, method of viscous vortex do-mains |
The study of motion of deformable bodies in a liquid flow is a topical task in engineering and biomechanics. Modelling of these problems as a two-way coupled interaction is problematic. In this case, at each time step, the hydrodynamic equations must be solved taking into account the motion of the body, which deforms and moves under the action of the hydrodynamic forces that depend on the motion of the body. One way to solve these problems is to use the splitting method when the equations of hydrodynamics and dynamics are solved separately by successive iterations. However, this approach does not always lead to a solution. In particular, when there is a significant difference in timescales of fluid hydrodynamic and body dynamics, the splitting method requires an unattainably small time step. In this paper, the meshless numerical method eliminating these problems is applied. The method allows combining the equations of flow vorticity from the surface of the body in the viscous fluid, and the equations of solid body dynamics into an integrated system of linear equations. This way all the unknowns including the body motion parameters are calculated over one time step, without splitting them into the hydrodynamic and the dynamic components. The examples of numerical solutions to the problems of rigid and flexible airfoils flapping in a viscous fluid flow are presented. The airfoil flexibility is modelled by flexible coupling of several non-deformable sections. The numerical solutions are compared with the experimental results. It is shown that the flexibility of the airfoil can have a significant influence on the flow and the resulting propulsive force of the flapping airfoil.
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