Advances in Water Treatment and Enviromental Management

148 WATER TREATMENTFig. 5a: Spatial Distribution of Mean Velocity U LandTurbulence Intensity Tu xwithout Grid (= type T0)Fig. 5b: Spatial Distribution of Mean Velocity U L andTurbulence Intensity Tu xwith Grid (= type T1)and the turbulence intensity again prove to be constant over the cross-section, butturbulence intensities now increase to a value of .Moreover, the measurements of the longitudinal and transversal velocity fluctuations( ) indicate the degree of isotropy of the turbulence without and with thegrid (Fig. 6). This fact is described by Baines and Peterson (1958) for air flow andalso by Lance and Bataille (1984) in water flow.Finally the decay of turbulence is governed by the following asymptotic law:In Fig. 7 is plotted the variation of turbulence intensities along the axis for all testconditions. No noticeable influence of the Reynolds-number, Re, in the range studiedwas found.Baines and Peterson (1958) also gave a function for the lateral scale of turbulence:(5)(6)