“…Shannon and Morris 7 and Bilka et al. 18 presented the statistics of the velocity field for a similar trailing edge, which agree with those shown here. Figure 8 summarizes the principal features of the blunt trailing edge flow.…”
Section: Resultssupporting
confidence: 89%
“…Bilka et al. 18 considered the correlation length of surface pressure fluctuations on the edge and reported a value of approximately lz/yf≈2.5 at the shedding frequency, which is thus similar to the correlation length of the upwash velocity measured in the present study (lz/yf=2.2-3.3). Figure 11.Coherence of the upwash velocity |γ(f,Δz)| (equation (5)) along the spanwise coordinate direction at the end of vortex formation zone, x/T=1,Re=3.8×104.Figure 12.Correlation length of the upwash velocity (a) and non-dimensional representation (b) (estimated using equation (6)).…”
Section: Resultssupporting
confidence: 89%
“…Between 0.5<x/T<1, the maximum value rms(v)/u∞>0.2, which is slightly lower than the values reported by Bilka et al. 18 (rms(v)/u∞≈0.3). Figure 9.rms of the velocity fluctuations around beveled trailing edge, Re=3.8×104 (shadow regions in black).…”
Section: Resultscontrasting
confidence: 67%
“…Discussion with the authors has lead to the conclusion that the disagreement can be explained by an erroneous estimate of the upwash velocity spectrum in the latter study (Figure 10 in Bilka et al. 18 ). This substantial underestimation of the velocity fluctuations also lead to the unexpected agreement of the predicted vortex shedding noise with acoustic measurement results.…”
Section: Resultsmentioning
confidence: 83%
“…Bilka et al. 18 predicted noise emission from a series of beveled trailing edges following the methodology of Roger et al. 14 The authors indirectly estimated the auto-spectral density of the upwash velocity in the wake from uncorrelated PIV measurements by invoking Taylor’s hypothesis, i.e.…”
Coherent vortex shedding from blunt and beveled trailing edges generates tonal noise, which is usually undesired. To obtain a better understanding of the noise generation under such conditions, the flow field around a beveled trailing edge was characterized for Reynolds numbers based on the bluntness ranging from 2.5 × 104 to 5.1 × 104. Flow field statistics were obtained by means of planar high-speed two-component and stereoscopic particle image velocimetry measurements. The development of the shear layers and vortex roll-up is described in the present study. Related length scales, the vortex formation length, and wake thickness parameter were derived from the measurements. Noise emission due to vortex shedding was predicted from an analytic solution, derived from diffraction theory and the reversed Sears’ problem, and compared to acoustic phased array measurements. This approach has previously been shown to provide accurate results for sharply truncated edges, but questions with regard to the applicability with different trailing edge geometries remained open. The prediction required the auto-spectral density, correlation length, and convective velocity of the upwash velocity component in the vortex formation region. Direct application with data obtained from particle image velocimetry measurements showed an overestimation of about 20 dB when compared to the acoustic measurements. The results thus showed that the prediction of vortex shedding noise based on the simplified wake model and diffraction theory is not generally applicable.
“…Shannon and Morris 7 and Bilka et al. 18 presented the statistics of the velocity field for a similar trailing edge, which agree with those shown here. Figure 8 summarizes the principal features of the blunt trailing edge flow.…”
Section: Resultssupporting
confidence: 89%
“…Bilka et al. 18 considered the correlation length of surface pressure fluctuations on the edge and reported a value of approximately lz/yf≈2.5 at the shedding frequency, which is thus similar to the correlation length of the upwash velocity measured in the present study (lz/yf=2.2-3.3). Figure 11.Coherence of the upwash velocity |γ(f,Δz)| (equation (5)) along the spanwise coordinate direction at the end of vortex formation zone, x/T=1,Re=3.8×104.Figure 12.Correlation length of the upwash velocity (a) and non-dimensional representation (b) (estimated using equation (6)).…”
Section: Resultssupporting
confidence: 89%
“…Between 0.5<x/T<1, the maximum value rms(v)/u∞>0.2, which is slightly lower than the values reported by Bilka et al. 18 (rms(v)/u∞≈0.3). Figure 9.rms of the velocity fluctuations around beveled trailing edge, Re=3.8×104 (shadow regions in black).…”
Section: Resultscontrasting
confidence: 67%
“…Discussion with the authors has lead to the conclusion that the disagreement can be explained by an erroneous estimate of the upwash velocity spectrum in the latter study (Figure 10 in Bilka et al. 18 ). This substantial underestimation of the velocity fluctuations also lead to the unexpected agreement of the predicted vortex shedding noise with acoustic measurement results.…”
Section: Resultsmentioning
confidence: 83%
“…Bilka et al. 18 predicted noise emission from a series of beveled trailing edges following the methodology of Roger et al. 14 The authors indirectly estimated the auto-spectral density of the upwash velocity in the wake from uncorrelated PIV measurements by invoking Taylor’s hypothesis, i.e.…”
Coherent vortex shedding from blunt and beveled trailing edges generates tonal noise, which is usually undesired. To obtain a better understanding of the noise generation under such conditions, the flow field around a beveled trailing edge was characterized for Reynolds numbers based on the bluntness ranging from 2.5 × 104 to 5.1 × 104. Flow field statistics were obtained by means of planar high-speed two-component and stereoscopic particle image velocimetry measurements. The development of the shear layers and vortex roll-up is described in the present study. Related length scales, the vortex formation length, and wake thickness parameter were derived from the measurements. Noise emission due to vortex shedding was predicted from an analytic solution, derived from diffraction theory and the reversed Sears’ problem, and compared to acoustic phased array measurements. This approach has previously been shown to provide accurate results for sharply truncated edges, but questions with regard to the applicability with different trailing edge geometries remained open. The prediction required the auto-spectral density, correlation length, and convective velocity of the upwash velocity component in the vortex formation region. Direct application with data obtained from particle image velocimetry measurements showed an overestimation of about 20 dB when compared to the acoustic measurements. The results thus showed that the prediction of vortex shedding noise based on the simplified wake model and diffraction theory is not generally applicable.
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