This paper is concerned with the determination of the relationship for the calculation of the discharge coefficient at free overflow over a rectangular sharp-edged broad-crested weir without lateral contraction. The determination was made on the basis of new measurement in a range of the relative thickness of the weir from 0.12 to 0.30 and newly in a large range of relative height of the weir extremely from 0.24 to 6.8 which greatly expands the application possibilities of low weirs. In addition, the effects of friction and surface tension on the value of the discharge coefficient were evaluated as well as the effect of the relative thickness of the weir. The new equation for discharge coefficient, expressed using the relative height of the weir, was subjected to verification made by an independent laboratory which confirmed its accuracy.
The paper deals with the determination of the discharge coefficient, effective head and newly the limit head in the Kindsvater-Shen formula for the determination of a relatively small discharge of clear water using a thin-plate weir with a triangular notch. The determination of the discharge coefficient, effective head and limit head is based on extensive experimental research and is verified by previous measurements by other authors. The experimental research was characterised by a large range of notch angles (from 5.25° to 91.17°), weir heights (from 0.00 m to 0.20 m), and water temperatures (from 15 °C to 45 °C), as well as a focus on relatively small heads (from 0.02 m to 0.18 m), which is where the strengths of the Kindsvater-Shen formula stand out. The experimental research supplemented existing knowledge about the overflow occurring with small heads and small weir notch angles. The newly determined dependencies in the Kindsvater-Shen formula extended its applicability to weirs with small notch angles and newly enabled the determination of the limit head, which restricts its applicability in the determination of small discharges.
Broad-crested side weirs have been the subject of numerous hydraulic studies; however, the flow field at the weir crest and in front of the weir in the approach channel still has not been fully described. Also, the discharge coefficient of broad–crested side weirs, whether slightly inclined towards the stream or lateral, still has yet to be clearly determined. Experimental research was carried out to describe the flow characteristics at low Froude numbers in the approach flow channel for various combinations of in- and overflow discharges. Three side weir types with different oblique angles were studied. Their flow characteristics and discharge coefficients were analyzed and assessed based on the results obtained from extensive measurements performed on a hydraulic model. The empirical relation between the angle of side weir obliqueness, Froude numbers in the up- and downstream channels, and the coefficient of obliqueness was derived.
The paper deals with selected procedures used to calculate the shape of compact nappe during free overfall from a smooth horizontal channel with rectangular cross section. Calculated and measured water surface and velocity conditions in the end section, the level of water surface upstream in front of the end section and the shape of the compact part of an overfall nappe are described for a particular compared case.
The use of environmentally-friendly materials in hydraulic engineering (e.g. the stone lining of weirs at levees) calls for the more accurate estimation of the discharge coefficient for broad-crested weirs with a rough crest surface. However, in the available literature sources the discharge coefficient of broad-crested weirs is usually expressed for a smooth crest. The authors of this paper have summarized the theoretical knowledge related to the effect of weir crest surface roughness on the discharge coefficient. The method of determination of the head-discharge relation for broad-crested weirs with a rough crest surface is proposed based on known discharge coefficient values for smooth surfaces and on the roughness parameters of the weir. For selected scenarios the theoretical results were compared with experimental research carried out at the Laboratory of Water Management Research, Faculty of Civil Engineering (FCE), Brno University of Technology (BUT). and Používání přírodě blízkých materiálů ve vodním hospodářství (např. kamenná opevnění povrchu přelivů v ochranných hrázích) vyvolává požadavek přesnějšího stanovení součinitele průtoku pro přelivy se širokou a hydraulicky drsnou korunou. V dostupných literárních pramenech je součinitel průtoku přelivů se širokou korunou obvykle vyjádřen pouze pro hladký povrch koruny přelivu. Autoři článku shrnuli teoretické poznatky týkající se vlivu drsnosti povrchu koruny přelivu na součinitel průtoku a navrhli metodu pro stanovení způsobu hydraulického výpočtu konzumční křivky přepadu přes přeliv se širokou a drsnou korunou. Postup vychází ze znalosti součinitele průtoku přelivu s hladkou korunou a charakteristik drsnosti. Pro vybrané scénáře byly teoreticky vypočítané hodnoty porovnány s výsledky experimentálního výzkumu uskutečněného v Laboratoři vodohospodářského výzkumu Ústavu vodních staveb, Fakulty stavební, Vysokého učení technického v Brně.
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.