Measuring and testing – Wind tunnel: aerodynamic wing and propeller study
Patent
1994-07-27
1995-07-25
Chilcot, Jr., Richard F.
Measuring and testing
Wind tunnel: aerodynamic wing and propeller study
138 45, G01M 900
Patent
active
054351758
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a wind tunnel having a free jet test section in which the direction of flow can be rotated during the operation of the wind tunnel. According to the teachings of the invention, this is possible while the wind is blowing, without having to tolerate substantial losses of aerodynamic quality of the flow with regard to uniformity of the velocity distribution and magnitude of the degree of turbulence.
A wind tunnel in which the direction of flow can be rotated during the operation of the wind tunnel is already known from German Patent Document DE 3715016. This wind tunnel is principally intended for aeroacoustic investigations of motor vehicles and is distinguished in that the fan is designed to simulate the flow noise of the motor vehicle standing in an acoustic chamber. However, what is to be understood from the design for the simulation of circumcirculation noise is not evident from the teachings of the described arrangement. In the disclosed arrangement, furthermore, a device is described in which the exit cross-section of the free jet nozzle is markedly smaller than the cross-sectional area of the motor vehicle against which flow is directed. It emerges from this that no excessively stringent requirements are imposed upon the quality of the aerodynamic circumcirculation simulation. For gust simulation, the nozzle can, in accordance with the teachings of the invention DE 3715016, be rotated in the manner of a pendulum about its vertical axis. The connection between nozzle and nozzle prechamber takes place in this case by means of a flexible hose conduit. Since in the course of the rotation of the nozzle the curvature of this hose conduit and consequently also the velocity profile of the elbow flow becoming established constantly changes, the uniformity of the velocity distribution in the nozzle exit cross-section which is attainable by this device is rather moderate.
A further wind tunnel in which the direction of the air flow on emerging from a rigid free jet nozzle can be altered is known from German Patent Document DE 40 07 230. In this case, airfoil wing profiles which are disposed in the form of a cascade and are pivotable in each instance about their vertical axis are used for the purpose of changing the direction of flow. In order that the change of direction of the free jet should be possible, this cascade with the pivotably disposed profiles is mounted behind the exit of the wind tunnel nozzle. The object to be investigated in the wind tunnel test section, which according to the teachings of the described arrangement is preferably a motor vehicle or a motor vehicle model, is therefore exposed to the jet flow influenced by the cascade. This jet flow is characterized by the wakes behind the profiles, which wakes are unavoidable even with the most careful design of the profiles. The wind tunnel could scarcely be suitable for aeroacoustic investigations for example, since upon the free jet noise there is also in addition superposed the noise of the profile cascade which is circumcirculated at high velocity, namely the outflow velocity from the nozzle. With regard to the jet turbulence as well, such a wind tunnel device does not satisfy the requirements to be satisfied for the execution of precise aerodynamic investigations, since the jet turbulence is greatly influenced by the wakes behind the individual profiles and this turbulence moreover still alters to a large extent with the passage distance of the flow as a result of the mixing of these wakes with the flow passing through between the profiles. This would mean for example that the turbulence at the front part of a motor vehicle to be investigated has a different structure from that at the rear.
A similar device for generating gust in a wind tunnel is described by W. Baumert et al. of the Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt in the report DFVLR Reports 89/05 in paragraph 7.4. However, in this case what are involved are relatively small angle changes which
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patent: 3104680 (1963-09-01), Orlin
patent: 3236263 (1966-02-01), Holderer
patent: 4398415 (1983-08-01), Jacocks et al.
patent: 5025659 (1991-06-01), Starr, Jr. et al.
Konrath Bernd
Kramer Carl
Chilcot, Jr. Richard F.
Mercedes - Benz AG
Oen William E.
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