Tetsushi Nagata

Dynamic Forces Acting on Elastic Heaving Airfoils Based on the Bending Stiffness Considerations

In recent years the flow field in the vicinity of moving airfoils capable of flexible elastic deformation has become a focus of attention, and its effects are beginning to be understood. Flow in the vicinity of an elastically deforming airfoil may be understood as a fluid-structure interaction (FSI) problem, and the motion and deformation of elastic airfoils, as well as the associated vortex flow phenomena in their vicinity, are complicated. Especially, the shape and hardness of the elastic regions of an airfoil may affect its rigidity and its bending characteristics and for this reason the influence of such airfoils on the flow fields around them require more detailed consideration. In this study, we fix the bending stiffness, which uniquely determines the nature of the elastic deformation of an elastic airfoil, and study the impact of changes in this quantity on the flow field, as well as the parameters that govern the fluid forces acting on the airfoil. In particular, our goal is to clarify the relationship between three key parameters, Strouhal number St, Reynolds number Re and bending stiffness K and is to elucidate the nature of the dynamic forces acting on an elastic airfoil as a function of these three dimensionless parameters. The bending stiffness K of the elastic airfoil is an important parameter that determines the bending characteristics and the moving boundary conditions at the wall surfaces in the fluid. By defining the new quantity St2/K, we showed that the characteristic of dynamic forces depends on the ratio St2/K.Copyright

Dynamics of Vortices Shed from an Elastic Heaving Thin Film by Fluid–Structure Interaction Simulation

The flow field around a moving body is treated as a fluid–structure interaction, and such phenomena consist of a series of moving elastic deformations of the body, vortex generation, growth, and development. In particular, the flow fields around thin materials have attracted attention due to their importance with respect to the development of micro air vehicles, for example. In this paper, we simulate the fluid–structure interaction of flow fields around an elastic heaving thin film using ANSYS 12.1/ANSYS CFX 12.1. The purpose of this study is to clarify the development of vortex flow structures in the wake of elastic heaving thin films.

Vortex Flow Structures determined by Stiffness of an Elastic Moving Thin Film

Flow field around a moving body is treated as fluid-structure interaction (FSI), and these phenomena have been continued a series of moving elastic deformation of the body, vortex generation, growing and development. In particular, flow fields around thin materials have attracted attention due to their importance in the development of MAVs and so on. In the present paper, we simulate the fluid structure interaction of a flow fields around elastic heaving thin film using ANSYS 14/ANSYS CFX 14. The purpose of the present study is to clarify development of vortex flow structures in the wake of the elastic heaving thin films determined by the body stiffness.

Vortex Structure Rolled Up From Elastic Thin Film by Fluid Structure Interaction Simulation

The flow field around a moving body is treated as a fluid-structure interaction (FSI), which is a series of phenomena from the elastic deformation of a body to vortex generation/growing/development. In the present paper, we simulate the fluid structure interaction of a flow field around an elastic heaving thin film with large deformation using ANSYS 12.1/ANSYS-CFX 12.1, and clarify the elastic deformation, velocity, acceleration, vortex roll-up from the trailing edge, circulation, and dynamic lift, as well as other important parameters to obtain the vorticities, circulations and dynamic lifts. The elastic deformation, velocity and acceleration can produce the large vorticity and the circulation. In particular, the vorticity that rolled up from the trailing edge of the thin film is dependent on the elastic velocity, and the vorticity production at the trailing edge is dependent on the elastic acceleration. Moreover, the vortex production is also distributed to the circulation production and the dynamic lift. Therefore, the elastic deformation, velocity and acceleration can produce and change the flow field for the vorticity, circulation, and dynamic force.Copyright

Wake Structure Around Moving Elastic Airfoils With Projections and Their Characteristics of Dynamic Forces by Fluid Structure Interaction Simulation

The flow around an elastic body is treated as a fluid-structure interaction (FSI), numerous fluid-structure coupled problems have been performed. Recently, two-way coupled analysis, which considers the fluid-structure interaction, has been performed extensively. In the present paper, we simulate a flow field around an elastic heaving flat plate with a variable surface shape and various Young’s moduli and perform bi-directional coupling analysis using ANSYS 12.1/ANSYS-CFX 12.1. In the case of the results without projection, the vorticity that grows along the plate surface, rolled up from the trailing edge, and developed in the wake are dependent on Strouhal number, independent of the Young’s modulus. However, in the case of the results with the projections, the vortex behaviors are different with the Young’s modulus. At E = 3.53 [MPa], the projections effect on the vortex behavior and the dynamic thrust exhibit approximately the same tendency with or without a projection. On the other hand, at E = 10.0 [MPa], the projection effect has an impact on the vortex behavior and the dynamic thrust. The vorticity and the dynamic thrust of E = 10.0 [MPa] become smaller than that of E = 3.53 [MPa] because of strong effects from the projections of the heaving elastic plate.Copyright

The Growth of Vorticity in the Vicinity of a Wall of an Elastic Moving Airfoil and Their Developing Processes

The behavior of a vortex generated by a moving object subjected to vibration and fluidic noise has been investigated both experimentally and numerically. Animals fly and swim by skillfully controlling vorticies generated around their bodies. Moreover, an elastic airfoil that enables elastic deformation in order to fly and swim with low energy has recently attracted a great deal of attention, and industrial applications of this elastic airfoil are expected. The authors performed the PIV measurement for vortex flow in the vicinity of a wall of the elastic NACA0010 and clarified quantitatively the change in the developing process of vortices generated in the vicinity of a wall with elastic deformation. The vorticity generated in the vicinity of the wall near the elastic NACA0010 continues to increase until the acceleration becomes maximum, because the vorticity develops for main flow direction (x-direction). Therefore, the growth and development of vortices generated in the vicinity of the wall near the trailing edge of a heaving airfoil depend strongly on the variation of accelerations of the trailing edge.Copyright