Abstract
The flow field quality has a principal signification at wind tunnel measurement. The creation of the flow field of air by fan leads to the rotation of entire flow field which is, moreover, deformed at the bends of the wind tunnel with close circulation. Despite the wind tunnels are equipped with the devices which eliminate these non-uniformities, in the most of cases, the air flow field has not ideal parameters in the test section. For the evaluation of the measured results of the model in the wind tunnel, the character of flow field deformation is necessary. The following text describes the possible general forms of the flow field nonuniformity and their effect on the aerodynamic coefficients calculation.
Highlights
The requirement for keeping a uniform air flow field uniformity in the wind tunnel is the state when the axial speed component has an identical value in each point of the test section that influences the measured model
The vortex flow field represents a certain generalization of the rotating flow field, where the axis of rotation is not located in the center of the wind tunnel center, but it is in the random position on the radial speed plane
The line between individual cases is dependent on the parameters of the individual vortices related to the defined data, i.e. the vortex intensity related to the speed of the flow field in the wind tunnel, or the vortex range related to the area of the flow field, etc
Summary
The requirement for keeping a uniform air flow field uniformity in the wind tunnel is the state when the axial speed component has an identical value in each point of the test section that influences the measured model. The radial speed component, which is perpendicular to the axial axis of the wind tunnel, should be zero. The level of the flow field non-uniformity in the wind tunnel is screened, for example, by a measuring probe, at defined points in the test section. The measuring space should be divided into four sectors in the chosen radial plane (i.e. the plane perpendicular to the axial axis of the wind tunnel). If the method described here is repeated in the other radial planes of the test section, the character of the development of the turbulence in the axial direction can be analyzed. The following text focuses on the general flow field deformation in one radial plane and without time-sensitive effects
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