Towing Wind Tunnel Research Articles

Parametric Study for Directional Stability of Tumbling Plates by Wind Tunnel Testing

The tumbling phenomenon is considered to be an important phenomenon for aircraft flight safety because of the possibility of falling objects from the aircraft reaching far away or for knowing the behavior of falling roof tiles blown off by strong winds. Therefore, many tests to measure the force act on the tumbling plate in wind tunnel have been conducted. The authors have been studying the directional stability of the tumbling plate [9], which has a great effect on the reach of falling objects, and have proposed a non-contact measurement method wind tunnel test method from the viewpoint of dynamic balance which can acquire the force without force sensors [12] Here, we call “towing wind tunnel test method”. In this paper, for the evaluation of the directional stability of the tumbling plate, we parametrically changed the planar configuration of the tumbling flat plate and measured the acting force in wind tunnel using this towing wind tunnel test method. As a result, the relationship between the shape of the tumbling plate and the conditions for directional instability was clarified.

Development of a Model Running Facility for a Study on under-floor Flow

We developed a model running facility to study the flow of the under-floor of railway car. The facility was set up in the test section of the Towing Wind Tunnel Facility where by a hood we can eliminate disturbances, such as natural wind. We carried out the model running tests and measured the velocity distribution under the model car. The velocity distribution was almost the same as in the rear cars from the car No.3, and the velocity between the rails was less than the velocity outside of the rail.

Measurement of ground effect and boundary-layer transition by towing wind tunnel

A newly constructed towing wind tunnel facility is introduced. In this wind tunnel, unlike a conventional wind tunnel, a testing model moves in still air on a testing track. This towing wind tunnel facility can therefore simulate highly complex flow between steady ground and a moving model without using a moving belt system. The performance of this facility is first explained. Some results of wings in ground effect experiments and boundary-layer transition experiments obtained using this facility are then given. From these results, we conclude that this facility has enough performance for complex flow testing.

Flows Between the Bottom of Moving Rectangular Body and the Plane Wall

Laminar flows between the bottom surface of a moving rectangular body and the plane wall are investigated experimentally using a towing wind tunnel facility where the model is carried in still air by a linear-motor actuator. The Reynolds number based on the moving speed and the distance between the bottom of the moving body and the fixed plane wall is about 170. In the transient stage of the flow development including the acceleration stage immediately after the body starts to move, the flow is driven not only by viscous shearing stress but also pressure gradient so that the maximum flow velocity exceeds the speed of the moving body. After the flow becomes steady, the normal-to-wall velocity distribution tends to the linear profile of the Couette flow except near the leading edge of the moving body where the flow is still affected by pressure gradient. In addition, the same rectangular-body is carried between two side-walls set normal to the plane wall. For such a nearly two-dimensional configuration, the flow develops to a Couette-Poiseuille flow.

Study of Transition Mechanism in a Wake Behind an Airfoil with a Small Angle of Attack by Using a Towing Wind Tunnel

This paper describes an experimental investigation of the transition mechanism of a wake generated behind a thin airfoil with a small angle of attack in a towing wind tunnel. A linear stability analysis shows that the wake is characterized by a change in the instability from locally absolute to locally convective at a downstream location (30 mm) of the airfoil trailing-edge. When the airfoil is towed in the tunnel, boundary layers develop on the upper/lower airfoil surfaces with different thicknesses. Since the asymmetric wake is generated, starting vortices of a single row are observed first in the wake, which is different from the wake Karman vortex street. The experimental result shows that time-harmonic fluctuations of the starting vortex sustain in the natural transition process due to a self sustained resonance in the absolutely unstable region behind the trailing edge. The wake profile in the saturation steady state yields the vortex street structure, where the fluctuation frequency is defined as the fundamental unstable mode by the final saturation steady state. The growth of the fundamental unstable mode in the convectively unstable region suppresses the high frequency fluctuations associated with the staring vortex generation. On the other hand, low-frequency fluctuations in the quasi-steady state sustaining in the saturation state grow gradually during the vortex street formation, which lead to the vortex street deformation downstream.

307 曳航風洞を用いた迎角をもつ翼後流の研究(流体工学II)

307 曳航風洞を用いた迎角をもつ翼後流の研究(流体工学II)

4120 日向灘研究施設における地面効果を受ける翼の空力特性に関する実験(G05-11 翼・翼列,G05 流体工学)

A new traffic system "Aero-Train" has wings and moves along an U-shaped guide way by utilizing the ground effect. It is necessary to optimize the aerofoil section to generate the ground effect effectively. The aero-train can not use flaps of usual aircrafts, because it is in the proximity to the ground. Moreover, when aerofoil moves near the ground, aerofoil becomes easy to the boundary layer separation and to increase the drag force. Then, we equip a small secondary aerofoil as a high lift device and a separation restraining device above the trailing edge of the aerofoil, and investigate aerodynamic characteristics of aerofoiles at low speed take-off and landing. We find out the most suitable location of a secondary aerofoil by the experiment using the towing wind tunnel at the Sunrise-Beach Research facility in Miyazaki.

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.

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

A study of a new high-speed zero-emission transportation “Aerotrain” is being carried out in Tohoku University and the University of Miyazaki. Because the aerotrain utilizes the ground effect, research on the aerofoil section, which can harness the ground effect effectively, is important. The aerotrain moves along a U-shaped guideway, which has a ground and sidewalls, so it has many viscous interference elements. In an analysis of the ground effects on the aerodynamic characteristics of aerofoils, the boundary layers on the aerofoil surface must be considered. At first, velocity distributions on the surfaces of aerofoils in potential flows are computed using the vortex method, then the momentum integration equations of the boundary layer are solved with experimental formulas. This procedure has the following advantages: modifications of the aerofoil section are easy because it is not necessary to make complicated computational grids, boundary layer transition and separation can be predicted using empirical procedures. The aerodynamic characteristics of four types of aerofoil sections are investigated to clarify the relationship between aerofoil sections and ground effects. Computational results are compared with experimental results obtained using a towing wind tunnel to verify computational precisions. In addition, aerofoil characteristics at an actual cruise speed are analyzed.

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.

Study of the Laminar-turbulent Transition of a Wake Behind an Airfoil by Using a Towing Wind Tunnel

This paper describes an experimental investigation of the natural transition mechanism of a wake generated behind a thin airfoil in a towing wind tunnel. A linear stability analysis shows that the wake is characterized by a change in the instability from locally absolute to locally convective at a downstream location of the airfoil trailing-edge. When the airfoil is towed in the tunnel, starting vortices are observed first in the wake. The experimental result shows that the feature of startig vortex sustains in the natural transition process due to a self sustained resonance in the absolute unstable region behind the trailing edge. The wake profile in the saturation steady state yields the vortex street structure, where the fluctuation frequency is defined as the fundamental unstable mode by the final saturation steady state. The growth of the fundamental unstable mode in the convectively unstable region suppresses the high frequency fluctuations associated with the staring vortex generation. On the other hand, low-frequency fluctuations in the quasisteady state sustaining in the saturation state grow gradually during the vortex street formation, which lead to the vortex street deformation downstream.

地面近傍を走行する翼型の空力特性に及ぼす反り形状の影響(流体工学(翼))

地面近傍を走行する翼型の空力特性に及ぼす反り形状の影響(流体工学(翼))

1453 絶対不安定な後流の乱流遷移に関する実験的研究

This paper describes an experimental investigating of natural transition mechanism of a wake forming behind a thin aerofoil in a towing wind tunnel. A linear stability analysis shows that an absolute instability pocket occurs downstream of the aerofoil trailing-edge. In the process of natural transition, the slight disturbances existing in the flow grow up selectively, and create the structures of vortex street in the wake. When the aerofoil is towed in the tunnel, starting vortices are generated in the wake. The experimental result shows that the feature of starting vortex affects the natural transition process due to the existence of absolute unstable region.

Measurement of Aerofoil Characteristics by Method of Towing Model.

Recently a new transport system Aerotrain has been proposed, and test using the first and second stage models are conducted in a 3 km guide way of old MAGLEV test facility in Miyazaki prefecture. Aerotrain has wings, and flies close to the ground of an open channel to take advantage of the ground effect. Characteristics of wing in ground effect (WIG) have been investigated using conventional wind tunnels. But this type of experiment cannot estimate the ground effect correctly because of the existence of boundary layer developed between bottom of the wings and the ground surface. Therefore, it is necessary to experiment using a towing wind tunnel to clarify characteristics of wing in the real ground effect. The aerodynamic charactersistis of two kinds of aerofoil sections: NAGA 4412 and circular arc aerofoil were clarified by the experriment towing the aerofoils in 3 km guide way of MAGLEV test facility. In addition, we examined problems to utilize the guide way of old MAGLEV as a towing wind tunnel.