Double-averaged velocity and stress distributions for hydraulically-smooth and transitionally-rough turbulent flows

• Autorzy: Cameron S. M. , Nikora V. I. , Coleman S. E.
• Języki publikacji: EN

Abstrakty

EN

We analyse experimental measurements of turbulent open-channel flow over hydraulically-smooth and transitionally-rough beds using the double-averaging methodology. Oil with a viscosity of 15×10-6 m2/s is used instead of water so that transitional-range roughness Reynolds numbers can be achieved with large (11.1 mm) roughness elements, allowing spatial variations in the mean velocity field to more easily be measured. Distributions of double-averaged velocities, turbulence intensities, form-induced intensities, and viscous, Reynolds, form-induced and total shear stresses are studied with comparisons made between distributions for hydraulically-smooth, transitionally-rough, and fully-rough boundaries. Measured streamwise turbulence intensities for all experiments peaked at a constant distance from the bed (z ++d + = 15) when elevation scale is adjusted using the zero-plane displacement d for the logarithmic velocity distribution. This collapse suggests that turbulence intensity distributions may be useful in assessing appropriate values of d for transitionally-rough and fully-rough boundaries. Form-induced normal and shear stresses above the roughness tops were found to collapse towards a common curve independent of roughness Reynolds number.

Słowa kluczowe

EN

double-averaging methodology; open-channel flow; particle image velocimetry

• Wydawca: Instytut Geofizyki PAN ; Springer
• Czasopismo: Acta Geophysica
• Rocznik: 2008
• Tom: Vol. 56, no. 3
• Strony: 642--653
• Opis fizyczny: bibliogr. 18 poz.

Twórcy

autor

Cameron S. M.

autor

Nikora V. I.

autor

Coleman S. E.

• School of Engineering, University of Aberdeen, Aberdeen, United Kingdom,

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