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TECHNICAL PAPERS

St and cf Augmentation for Real Turbine Roughness With Elevated Freestream Turbulence

[+] Author and Article Information
Jeffrey P. Bons

Air Force Institute of Technology, Wright-Patterson AFB, OH 45433

J. Turbomach 124(4), 632-644 (Nov 07, 2002) (13 pages) doi:10.1115/1.1505851 History: Received November 02, 2001; Online November 07, 2002
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References

Figures

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Sample 2-D traces from each of the six scaled roughness surfaces. Surfaces nos. 1 to 6 ordered from top to bottom. Traces are offset vertically to eliminate overlap.
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Schematic of flat plate wind tunnel at AFRL in heat transfer measurement configuration
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Schematic of floating panel cf measurement apparatus on AFRL wind tunnel
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Typical temperature and h histories during transient test
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Skin friction versus Reynolds number for smooth and rough panels
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Stanton number versus Reynolds number for smooth and rough panels
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Skin friction for rough panels compared to standard roughness correlations. Each correlation shown using ks from Eq. (7) over all surfaces. Surfaces 1–3 also shown for ks=k/2 (dashed lines). Data for Rex=900,000 only.
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Stanton number for rough panels compared to standard roughness correlations. Each correlation shown using ks from Eq. (7) over all surfaces. Surfaces 1–3 also shown for ks=k/2 (dashed lines). Data for Rex=900,000 only.
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Equivalent sandgrain correlation data versus fit. Data from Bogard et al. 20 with accompanying fit (Eq (7)). Data from “real” roughness surfaces at both Reynolds numbers with accompanying fit (Eq. (10)).
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Equivalent sandgrain (ksadj as determined by matching Schlichting cf prediction with “real” roughness data) versus rms surface slope angle (αrms) with polynomial fit (Eq. (11)).
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Stanton number for “real” roughness panels compared to Dipprey and Sabersky correlation using ksadj and cf from Schlichting. Data for Rex=900,000 only.
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Stanton number for six “real” rough panels + cone surface (no. 7) compared to Dipprey and Sabersky correlation using ksadj and cf from Schlichting. Also, modified Dipprey and Sabersky correlation (Eq. (12)). Data for Rex=900,000 only.
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Mean and fluctuating velocity profiles at roughness surface leading edge. Three levels of freestream turbulence: 1, 5, and 11%. Data for Rex=900,000. (Sparse data presentation for clarity.)
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Skin friction versus Reynolds number for smooth surface at Tu=1, 5, and 11%
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Stanton number versus Reynolds number for smooth surface at Tu=1, 5, and 11%. Elevated turbulence data for Re=900,000 only.
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Comparison of combined (synergistic) roughness/turbulence effects on cf and St with estimates using added and compounded individual effects of roughness alone and turbulence alone. cf data for six rough surfaces at (a) Tu=5% and (b) Tu=11% St data at (c) Tu=5% and (d) Tu=11%. All at Rex=900,000 only.
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Efficiency factor, η=(St/Sto)/(cf/cfo), versus statistical skewness of roughness. Data for six rough surfaces at Tu=1, 5, and 11% for Re=900,000 only. Polynomial fits to all but surface no. 2 data.

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