Vízügyi Közlemények, 1966 (48. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(100) specific gravity quartz gravel) into the relationship between Bogárdi's bed stability factor and diameter of sediment particle IEq. (4), Fig. J]. Bogárdi's Eq. (4) has been developed further by the author to render it applicable 'to fluids of arbitrary specific gravity and viscosity and sediments of any specific gravity. Furthermore, Eqs. (8) to (12) have become dimensionless ( Fig. 2). Any change in viscosity and specific gravity affects the type of flow. Thus if the temperature of water is reduced from 20 to 5 Centigrades, the independent variable in Eq. (8) suffers a change of 30%. A change in the specific gravity of sediment from 2.65 to 1.50 g/cu. cm entails a change of more than 200% in the dependent variable of Eq. (8). A dimensionless invariant has been derived by Laursen for describing the total potential sediment (bed-load -f- suspended) which the stream is capable of carrying, i.e. the sediment transporting capacity. This invariant is given in Eq. (13). After the necessary transformations this has also been included in Fig. 2. The results of these investigations, the practical utilization of results is illustrated by numerical examples. In one of these examples a method is given for checking the potential danger of scouring in a particular case. In another example the method for determining sediment transporting capacity is demonstrated. A drawback of the above investigations is that they are limited to uniform sediments only. The laws governing the movement of mixed sediments occurring in Nature await to be explored. Valuable investigations in this field are being performed — among others — by Rákóczi and Stelczer. NEW ASPECTS OF FLOW - THROUGH STUDIES By I. Horváth, Civ. Engr., P. Pásztó, Chem. Engr., Dr. L. Szabó, Civ. Engr. (For the Hungarian text see pp. 490) Problems arising in connection with the hydraulic study of water treatment installations are dealt with in the paper. Theoretical and practical aspects of these studies are discussed on the basis of experiments performed at the Laboratory of the Chair for Water Development, Technical University for Building and Traffic Engineering, Budapest and the Research Institute for Water Resources Development. On the strength of experimental results and theoretical considerations the following conclusions have been arrived at: 1. In flow through studies experiments cannot be reproduced unless identica conditions can be ensured. 2. In the determination of the flow through curve the shape of the latter and the hydraulic efficiency derived therefrom are appreciably influenced by the discharge passing through the treatment installation and the highest concentration of water mixed with tracer material. 3. For the above reasons flow through studies should possibly be performed by methods permitting the use of low tracer concentrations which result in negligible increase of density. Where this proves impossible, care should be taken in comparative studies to use identical tracer concentrations in all alternatives. 4. For checking the reliability of flow through studies, during experiments changes of water temperature and tracer concentration in a vertical should also be observed in control sections. 5. For determining the accuracy of measurement the observation of tracer concentration is recommended not only after the installation, but also in the entrance section. From these data the error of tracing the flow through curve can be determined as described in the paper. 6. The experimental method relying on the theory of the flow-through curve can be applied successfully to the hydraulic study of aeration installations of sewage treatment plants as well. Valuable parameters characteristic for the operation and efficiency of the biological treatment system can be obtained in this manner.