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 hydraulic characteristics of flow over rectangular broad-crested weirs with varying upstream slopes were experimentally studied. A series of laboratory experiments was performed to investigate the effects of changing upstream slopes from 90º to 75º, 60º, 45º, 30º, 22.5º, 15º, and 10º on the flow surface pattern, discharge coefficient values, approach velocity profile and flow separation zone. In addition, a new mathematical relationship for water surface profile and a new correction factor to estimate discharge coefficient over weirs with various upstream slopes were introduced. The results showed decreasing upstream slopes from 90º to 10º leading to increasing discharge coefficient values and dissipation of the separation zone. and Práca obsahuje výsledky experimentálneho štúdia prietoku vody cez pravouhlý priepad so širokou priepadovou hranou s rozdielnymi sklonmi návodného povrchu priepadu. Uskutočnili sme sériu laboratórnych pokusov s cieľom štúdia vplyvu rôznych sklonov návodného povrchu priepadu od 90°, 75°, 60°, 45°, 30°, 22,5°, 15°, až po 10° na tvar hladiny, hodnoty prietokového súčiniteľa, rýchlostné profily a na prúdenie v oblasti separácie. Okrem toho boli zistené nové matematické vzťahy na výpočet tvaru hladiny, ako aj nové korekčné faktory na určenie prietokových súčiniteľov cez priepad s rozdielnymi sklonmi návodného povrchu. Z výsledkov vyplýva, že znižujúce sa sklony návodného povrchu priepadu od 90° po 10° vedú k zvýšeniu prietokového súčiniteľa a k disipácii oblasti separácie.
We describe the extension of the multiplication on a not-necessarily-discrete topological monoid to its flow compactification. We offer two applications. The first is a nondiscrete version of Hindman’s Theorem, and the second is a characterization of the projective minimal and elementary flows in terms of idempotents of the flow compactification of the monoid.
In this paper congestion control problem in connection-oriented communication network with multiple data sources is addressed. In the considered network the feedback necessary for the flow regulation is provided by means of management units, which are sent by each source once every data packets. The management units, carrying the information about the current network state, return to their origin round trip time after they were sent. Since the source rate is adjusted only at the instant of the control units arrival, the period between the transfer speed modifications depends on the flow rate earlier, and consequently varies with time. A new, nonlinear algorithm combining the Smith principle with the proportional controller with saturation is proposed. Conditions for data loss elimination and full resource utilisation are formulated and strictly proved with explicit consideration of irregularities in the feedback information availability. Subsequently, the algorithm robustness with respect to imprecise propagation time estimation is demonstrated. Finally, a modified strategy implementing the feed-forward compensation is proposed. The strategy not only eliminates packet loss and guarantees the maximum resource utilisation, but also decreases the influence of the available bandwidth on the queue length. In this way the data transfer delay jitter is reduced, which helps to obtain the desirable Quality of Service (QoS) in the network.
A synthetic jet can be produced over broad range of time and length-scales. Theirs unique attributes make them attractive fluidic actuators for various flow-control tasks. Generation, evolution and interaction of synthetic jets are reviewed in the presented paper. Application of this actuator type ranging from separation and turbulence control, control to thrust vectoring and mixing augmentation to skin friction control is shown. and Obsahuje seznam literatury
Labelling of DNA in replicating cells using 5-bromo-2'- deoxyuridine (BrdU) is widely used, however the rapid clearance and metabolisation of BrdU in the living organism is a critical issue. Although the pharmacokinetic of BrdU in experimental animals is empirically approximated, the exact time-curve remains unknown. Here we present novel method for estimation of the BrdU content in the blood serum. The application is based on the in vitro cocultivation of tumour cells with the examined serum and the subsequent quantification of the incorporated BrdU in the DNA using flow cytometry analysis. Our results demonstrate that this approach can quantify the BrdU concentration in serum at 1 μmol.dm-3 and might represent an attractive alternative to conventional chromatographic analysis. The employment of tumour cells as "detectors" of the BrdU content in serum provides an advantage over high pressure liquid chromatography (HPLC), as this approach allows us to approximate not only the concentration of BrdU, but also to determine, whether BrdU is present in the blood serum in effective concentration to reliable label all cells undergoing the S-phase of the cell cycle. The presented application might be a helpful tool for studies on pharmacokinetics of BrdU or other thymidine analogues when testing various administration routes or protocols., J. Mikeš, J. Ševc, J. Košuth, A. Matiašová, Z. Daxnerová, P. Fedoročko., and Obsahuje bibliografii
The document deals with the research of flow in the cross-over channel of the high-pressure stage with partial admission of first stage. In the opening part there is a description of the experimental model and the method of measuring flow fields with high velocity gradient using the stereo PIV principle. The second part describes the design of the model inlet part. The third chapter deals with measuring in the cross-over channel outlet slot with no influence of the stator blade cascade of the flollowing stage. The stator blade cascade feedback is described in the fourth part. During all the measurements we observe the influence of the shaft revoluton on the flow field at the cross-over channel outlet. and Obsahuje seznam literatury
The cavitations in turbo-machines decrease their efficiency and have a bad impact of their work-life and therefore constructors are always trying to avoid or minimize the cavitation risks in hydraulic machines. In this paper we have done the LDV measurement of flow in the model pump suction sump with baffle. In precedent works we did the PIV (Particles Image Velocimetry) measurement with and without baffle. Around the pump bell there are very complex vortices, which can affect seriously the flow characteristics of the pump. They can also cause vibrations, cavitations and decrease the efficiency of the system. In this experiment the pump suction sump and the pump bell with particular structure are used to search the flow situation in the surrounding of the bell. Both LDV and PIV experiments were done with steady flow using appropriate materials. and Kavitace v turbogenerátorech a čerpacích systémech snižuje jejich účinnost a negativně ovlivňuje jejich životnost. Snahou konstruktérů je proto vyloučit nebo minimalizovat riziko kavitace v hydraulických strojích. V článku jsou prezentována měření rychlostních polí pomocí LDV v modelové sací jímce s tokovým usměrňovačem a výsledky jsou porovnány s dřívějšími měřeními pomocí PIV. V blízkosti sacího zvonu vznikají komplikované vírové struktury, které mohou následně ovlivňovat charakteristiku čerpadla a které mohou být příčinou vzniku vibrací, kavitace a snížení účinnosti. Pozornost proto byla zaměřena na měření rychlostních polí v okolí sacího zvonu.
We study the prolongation of semibasic projectable tangent valued $k$-forms on fibered manifolds with respect to a bundle functor $F$ on local isomorphisms that is based on the flow prolongation of vector fields and uses an auxiliary linear $r$-th order connection on the base manifold, where $r$ is the base order of $F$. We find a general condition under which the Frölicher-Nijenhuis bracket is preserved. Special attention is paid to the curvature of connections. The first order jet functor and the tangent functor are discussed in detail. Next we clarify how this prolongation procedure can be extended to arbitrary projectable tangent valued $k$-forms in the case $F$ is a fiber product preserving bundle functor on the category of fibered manifolds with $m$-dimensional bases and local diffeomorphisms as base maps.
The flow behaviour of coarse-grained slurry depends on particle size, shape, density and concentration, and on the density and rheological properties of the carrier liquid. The present paper describes the results of an experimental investigation and flow visualisation of model coarse-grained particle-water mixtures in a closed pipe loop with smooth stainless steel pipes of inner diameter 36 mm. Glass balls and washed graded pebble gravel of mean diameter d50 = 6 mm were used as model coarse-grained material. The effect of slurry velocity and particle concentration on the slurry flow behaviour and pressure drop in the turbulent regime was evaluated. Particle distribution in the pipe cross-section and motion of particles along the pipe invert, particle saltation and particle conveying in the carrier liquid were investigated in a transparent pipe viewing section and motion of individual particles was described. Velocity profiles of the carrier liquid and conveyed particles were determined. and Tokové chování hrubozrnných suspenzí závisí na velikosti, tvaru a hustotě částic, koncentraci pevné fáze a hustotě a reologických vlastnostech nosné kapaliny. Článek popisuje výsledky experimentálního výzkumu a vizualizace proudění modelové hrubozrnné suspenze v experimentální potrubní lince s hladkým nerezovým potrubím s vnitřním průměrem 36 mm. Skleněné kuličky a praný oblý štěrk (kačírek) se středním zrnem d50 = 6 mm byly použity jako modelový materiál. Byl vyhodnocen vliv rychlosti proudění suspenze a koncentrace pevné fáze na chování a tlakové ztráty suspenze. Rozdělení částic v příčném průřezu potrubí a pohyb částic podél dna potrubí, jejich saltace a unášení v nosné kapalině byly zkoumány v transparentní části potrubí a byl popsán pohyb jednotlivých částic a pro vybrané případy byly stanoveny rychlostní profily nosné kapaliny a unášených částic.