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Objectives
The objective is to show the variations of amplitudes and phase lead towards bump motion of both the shock wave movement and the unsteady static pressure relatively to the reduced frequencies characterizing this experimental study.
2. Description of the experimental set-up
The test facility features a straight rectangular cross section. The oscillating model used in the here presented study is of 2D prismatic shape and has been investigated as non-vibrating in previous studies (Bron et al. [2001] ,Bron et al. [2003]), from where extensive baseline data are available. In order to introduce capabilities for the planned fliid-structure tests, a fhxible version of the model was built. Figure 1 shows the way the generic model oscillates in the test section and presents the optical access offered by this test facility. The ft>w
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Figure 1. Test facility composition and optical access |
entering the test section can be set to different operating conditions characterized by different inlet Mach number, Reynolds number and reduced frequency (Table 1). The generic model is molded of polyurethane, at defined elasticity (E=36.106MPa) and hardness (80 shore), by vulcanization over a steel metal bed. As shown in Figure 2, it includes a fully integrated mechanical actuator allowing smooth surface deformations. This oscillating mechanism actuates the fhxible model (bump) in a first bending controlled mode shape. While the highest point located at 57% of the chord vibrates in a sinusoidal motion of 0.5mm amplitude, the two edges of the chord stay fixed. A 1D laser sensor measures the model movement through the optical glass top window in one direction with a bandwidth of 20kHz and a resolution of +/-0.01mm. Time-
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Table 1. Operating fbw parameters
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Table 2. Long line probe measurements performed |
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Encoder accuracy on the position of the camshaft |
±10.8Deg. |
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Inner diameter of the 15 Teflon tubes |
0.9mm |
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Length of the 15 Teflon tubes |
0.5m |
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Number of Kulite fast response transducers |
15 |
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Inner diameter of the 15 long lines |
1.3mm |
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Length of the 15 long lines |
5m |
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Amplitude of the first bending mode shape |
±0.5mm |
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Average maximum height of the generic model |
hmax = 10 mm |
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Tested excitation frequencies range |
10Hz<f<200Hz |
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Tested reduced frequency based on the half chord for Miso1 = 0.63 |
0.015<k<0.294 |
resolved pressure measurements are performed on the oscillating surface using pressure taps and Kulite fast response transducers. To achieve this, Tefbn tubes are directly moulded in the 2D fhxible generic model and plugged to the Kulite transducers mounted with the long line probe technique far from the oscillating measured surface (Schaffer and Miatt [1985], see Table 2). These fast response transducers deliver signals with delays and large damping but exempt of resonance effect. The delays, damping, tubes vibrations and tubes elongations have been carefully calibrated. All components of this test facility are fully described in Allegret-Bourdon et al. [2002]. The test section offers optical access from three sides (Figure 1). While the instantaneous model shape is scanned using the geometry measurement system through the top window, Schlieren measurement can be performed using the access through two sides windows. A high-speed video camera produces the Schlieren videos with a sampling frequency of 8kHz.
Figure 2. Cut view of the generic model (bump)
