Definition of dimensionless coefficient of resistance and coefficient of roughness in cross-section of stream with large roughness element
Treść / Zawartość
The results of investigations carried out in the stream Będkówka – a left bank tributary of the Rudawa River are presented in this paper. A stream sector with large roughness element was chosen for investigations. The performed measurements included cross-section leveling and longitudinal leveling of the stream channel, bed load (sediment) sampling, and hydrometric measurements. Cross section leveling included five cross-sections in the 19-m long stream sector; these were located upstream and downstream the large roughness element and in its region. Differentiation of flow velocity in the region of large roughness element and its influence on differentiation of the load granulometric composition in the stream channel was shown. Immediately downstream the large roughness grain zone a fine grain sediment was frapped, its diameter d50 was seven to ten times smaller than that of the sediment in bed present in the stream channel. The dimensionless coefficient of resistance was calculated taking into account the equivalent bottom roughness determined in each of the examined sections by use of Gladki`s formulae. It was found that the large roughness element in the Będkówka stream caused a change of hydraulic conditions of water flow and, in consequence, the dimensionless coefficient of resistance in the grain section increased by about four times. The coefficient of channel roughness was also determined and it was shown that the coefficient of roughness in the section of large roughness element determined with consideration of the determined dimensionless coefficient of resistance increased on the average in the section of large roughness grain by over 34% in relation to the coefficient of channel roughness.
- Byczkowski A. 1996. Hydrologia. T. 2, Wydawnictwo SGGW, Warszawa.
- Kubrak J., Żbikowski A. 1995. Hydrauliczne warunki przepływu w korytach wielkich wód. [W:] Hydrauliczne i ekologiczne problemy inżynierii rzecznej. Materiały seminaryjne KatedryBudownictwa Wodnego SGGW w Warszawie. B-1-B-14.
- Schroeder W. 1989. Gestaltungsmoeglichkeiten einer Renaturierungsstrecke und hydraulische Hachweise. Wasserbau-Mitteilungen der TH Darmstadt, Heft 29.
- van Rijn L. C. 1984. Sediment transport. Part II: Suspended load transport. Journal of HydraulicEngineering, vol.110, No 10. 1613-1641.