Kimitaka Hirano

An Analysis of Ground Effects on Aerodynamic Characteristics of Aerofoils with a Secondary Aerofoil

Investigation of a new high-speed zero-emission transportation “Aerotrain” is proceeded mainly in Tohoku University and University of Miyazaki. Since the Aerotrain utilizes the ground effect, researches of the aerofoil section which can efficiently harness the ground effect are important. The Aerotrain moves along U-shaped guide way which has a ground and two side walls, so a many viscous interference occur between the Aerotrain and the walls. The flow through primary and secondary aerofoils is analyzed to prevent the boundary layer separation for the improvement of the aerodynamic characteristics at low speed near the ground. A small secondary aerofoil is equipped above the trailing edge of the primary aerofoil to increase lift at takeoff and landing. The most suitable location of secondary aerofoil is investigated through the boundary layer approximation analysis and the experiment using a towing wind tunnel. We verify the effect of secondary aerofoil by experiment, confirm the accuracy of the analysis by comparing with experimental results, and try to find the most suitable aerofoil section for the Aerotrain.

An Analysis of Ground Effects on Aerodynamic Characteristics of Aerofoils Using Boundary Layer Approximation

Investigation of a new high-speed zero-emission transportation “Aerotrain” is proceeded mainly in Tohoku University and Miyazaki University. Since the aerotrain utilizes the ground effect, researches of the aerofoil section which can harnesses the ground effect effectively are important. The aerotrain moves along U-shaped guide way which has a ground and side walls, so it has many viscous interference elements. In an analysis of ground effects on aerodynamic characteristics of aerofoils, it must be considered boundary layers on the aerofoil surface. At first, velocity distributions on surfaces of aerofoils in potential flows are computed using the vortex method, then the momentum integration equations of boundary layer is solved with experimental formulas. This procedure has following advantages : modifications of aerofoil section are easy because it is not necessary to make complicated computational grids, a boundary layer transition and separation can be predicted using empirical procedures. The aerodynamic characteristics of four kinds of aerofoil sections is investigated to clarify the relation between aerofoil sections and ground effects. Computational results are compared with experiments results by the towing wind tunnel to verify computational precisions. In addition, aerofoil characteristics at actually cruise speed are analyzed.

The Visualization and Measurement of Flows over Groups of Circular Cylinders Placed Perpendicularly on a Ground Plane.

This experimental research simulates that tidal waves which are higher than coastal pine forests strike against the forests. Canopy models of coastal forests are presented as groups of circular cylinders with steel wool placed perpendicularly on a ground plane. The circular cylinders and the steel wool present trunks and crowns of trees, respectively. The effect of canopy models on flow fields is studied with flow visualization and image processing. Two patterns of canopy models are used; one is a continuous pattern and the other a gap-toothed pattern. With flow visualization, crowns of these models dam up tidal waves, and the waves rise up to about twice the height of trees at the frontal part of canopy models. Velocity fields of the flows are measured by image processing of the correlation method. Then, the velocity fields are revised under constraint of the equation of continuity. Velocity fields in the downstream regions of the plant canopies are evidently different between two patterns of models.

Visualization and Numerical Analysis of Flows between corotating Multidisks

Flows between corotating flat multidisks were studied with two methods, flow visualization and numerical simulation. Flow visualization was performed for Reynolds number from 600 to 2000 and dimensionless spacing H/R of two disks from 0.1 to 0.4. When angular velocities of multidisks were changed to faster, slower or reverse rotation, streaklines of flow fields were observed in the laser light sheet. For the reverse of rotation, unsteady behavior of secondary flows in the meridian plane of two disks showed that tornado effects appeared on the disk in a short time, and then steady secondary flows of constant rotation were formed. Incompressible axisymmetric viscous flows between the multidisks were analyzed through the finite element method-the SMAC method. Growth process of the tornado effects in flow fields was numerically represented in detail. Results from numerical simulation corresponded to that of flow visualization.