Modelling of supercritical turbulent flow in an open channel with transversal ribs on its bottom was concentrated particularly on the development of flow separation behind ribs and on the corresponding changes of free surface. Further, the pressure drag of individual ribs was investigated including its dependence on the rib spacing, as well as the origin of secondary flow near the side walls of the channel behind ribs. Numerical results obtained by the software ANSYS CFX 11,0 were compared with experiments carried out by means of LDA and PTV techniques in free-surface water experiments carrid out by means of LDA and PIV techniques in free-surface water channel 200 x 200 mm with one or two transversal ribs 10 x 10 mm with various spacing. and Obsahuje seznam literatury
Modelling of turbulent flow in curved channels and diffusers of rectangular cross-section was aimed at the evolution of secondary flow and origin of flow separation and their connection with energy losses and pressure recovery. Results of numerical simulations carried out using software CFX TASCflow 2.12 were compared with experiments made in a water channel. Turbulent flow in diffusers of rectangular cross-section with the constant channel height, flow turn angle 90 deg and area ratio AR = 1.5 was investigated. Numerical simulation was carried out for flow in diffusers with the cylindrical inner wall and with the cylindrical centreline. Turbulent flow in a curved channel of constant cross-section was investigated for comparison. Further, the effect of the inner wall radius on the character of flow in the diffuser was studied. Flow separation occurs on the inner wall of the channel before the bend exit and its extent is restricted to the central part of the channel due to secondary flow going from the sidewalls to the channel axis. The extent of separation region and consequently the energy losses decrease with the increasing radius of the inner wall curvature. and Obsahuje seznam literatury
The paper deals with the determination of the basic characteristics of flow at the crest of a rectangular broad-crested weir and in detail with the characteristics of flow separation at the upstream edge of the weir crest. The determination of the characteristics is made on the basis of measurement of the water surface level, the pressure head and the velocity field using the Particle Image Velocimetry method. The characteristics are expressed dimensionless in relation to the energy overflow head and the critical depth. and Článek pojednává o stanovení základních charakteristik proudu na široké koruně pravoúhlého přelivu a detailně o charakteristikách odtržení proudu za návodní hranou koruny přelivu. Charakteristiky jsou stanoveny na základě měření úrovně hladiny, tlakové výšky a rychlostního pole metodou Particle Image Velocimetry. Charakteristiky jsou vyjádřeny bezrozměrně ve vztahu k energetické přepadové výšce a kritické hloubce.