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422. Floods effects on rivers morphological changes application to the Medjerda River in Tunisia
- Creator:
- Gharbi, Mohamed, Soualmia, Amel, Dartus, Denis, and Masbernat, Lucien
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- floods, hydrodynamics, sediment transport, modelling, and river morphology
- Language:
- Slovak
- Description:
- In Tunisia especially in the Medjerda watershed the recurring of floods becoming more remarkable. In order to limit this risk, several studies were performed to examine the Medjerda hydrodynamic. The analysis of results showed that the recurrences of floods at the Medjerda watershed is strongly related to the sediment transport phenomena. Initially, a one dimensional modelling was conducted in order to determine the sediment transport rate, and to visualize the river morphological changes during major floods. In continuity of this work, we will consider a two-dimensional model for predicting the amounts of materials transported by the Medjerda River. The goal is to visualize the Medjerda behaviour during extreme events and morphological changes occurred following the passage of the spectacular flood of January 2003. As a conclusion for this study, a comparative analysis was performed between 1D and 2D models results. The objective of these comparisons is to visualize the benefits and limitations of tested models. The analysis of the results demonstrate that 2D model is able to calculate the flow variation, sediment transport rates, and river morphological changes during extreme events for complicated natural domains with high accuracy comparing with 1D Model.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
423. Flow characteristics at trapezoidal broad-crested side weir
- Creator:
- Říha, Jaromír and Zachoval, Zbyněk
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- broad-crested side weir, experimental research, flow characteristics, and hydraulics
- Language:
- Slovak
- Description:
- 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.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
424. Flow characteristics of rectangular broad-crested weirs with sloped upstream face
- Creator:
- Goodarzi, Ehsan, Farhoudi, Javad, and Shokri, Naser
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- broad crested weir, upstream face slope, flow surface pattern, discharge coefficient, correction factor, separation zone, velocity profile, priepad širokou priepadovou hranou, sklon návodného povrchu, tvar povrchu hladiny, výtokový koeficient, korekčný faktor, oblasť separácie, and profily rýchlosti prúdenia
- Language:
- Slovak
- Description:
- 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.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
425. Flow measurement in the model pump suction sump with baffle by means of LDV and PIV
- Creator:
- Mansa, Kante, Yulin, Wu, Yong, Li, Xiaoming, Li, and Yu, Xu
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- PIV, LDV, flow in pump suction area, velocity measurement, proudění v sací jímce, and měření rychlostí
- Language:
- Slovak
- Description:
- 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.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
426. Flow structure of coarse-grained slurry in a horizontal pipe
- Creator:
- Vlasák, Pavel, Kysela, Bohuš, and Chára, Zdenek
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- coarse-grained slurry, turbulent flow, pressure drop, velocity distribution, flow structure, concentration effect, hrubozrnné suspenze, turbulentní proudění, tlakové ztráty, rozdělení rychlostí, struktura proudu, and vliv koncentrace
- Language:
- Slovak
- Description:
- 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.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
427. Flow structure within a vegetation patch in a gravel-bed river
- Creator:
- Jahadi , Mahsa, Afzalimehr , Hossein, and Rowinski , Paweł M.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- submerged vegetation patch, mixing layer, spatially evolving flow, and gravel bed river
- Language:
- Slovak
- Description:
- Investigation of the interactions between submerged vegetation patch and flow structure is of crucial importance for river engineering. Most of hydraulic models have been presented for fully developed flows over uniform vegetation in the laboratory conditions; however, the mentioned interactions are complex in river flows where the flow is not developed along small patch. This reveals a gap between developed and non-developed flow along the vegetation patch. This study was conducted in a gravel-bed river in the central Iran. The results reveal that the flow structure in evolving flow (non-developed flow) along the patch resembles that in shallow mixing layer. Accordingly, a shallow mixing layer model and modified equations are combined to quantify evolving area along the patch. The evolving shallow mixing layer equations for the flow along a non-uniform vegetation patch reach a reasonable agreement with field data. However, the spreading coefficient of this model less than one was reported in literature, 0.06 and 0.12. In addition, the flow immediately downstream the vegetation patch behaves similar to a jet and is parameterized by two conventional models, conventional logarithmic law and mixing layer theory. These models present a reasonable agreement with the measured velocity profiles immediately downstream the patch.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
428. Fodor on causes of mentalese symbols
- Creator:
- Aytekin, Tevfik and Sayan, Erdinç
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- causal theory of content, naturalistic semantics, asymmetric dependence, causal law, and operative causes
- Language:
- Slovak
- Description:
- Jerry Fodor’s causal theory of content is a well-known naturalistic attempt purporting to show that Brentano was wrong in supposing that physical states cannot possess meaning and reference. Fodor’s theory contains two crucial elements: one is a notion of ''asymmetric dependence between nomic relations'', and the other is an assumption about the nature of the ''causally operative properties'' involved in the causation of mental tokens. Having dealt elsewhere with the problems Fodor’s notion of asymmetric dependence poses, we show in this paper a difficulty with the other element of his theory concerning what kinds of properties are the causally operative ones in the tokenings of a semantic symbol in the brain of a perceiver. After presenting this difficulty, we examine three possible responses a Fodorian might make to our criticism., Kauzální teorie obsahu Jerryho Fodora je známým naturalistickým pokusem, který ukazuje, že Brentano se mýlil v domněnce, že fyzické stavy nemohou mít smysl a odkaz. Fodorova teorie obsahuje dva klíčové elementy: jeden je představa o ''asymetrické závislosti mezi nomic vztahy'', a jiný je předpoklad o povaze ''kauzálně operativních vlastností'' zahrnutý v příčině duševních tokenů. Když jsme se zabývali problémy s Fodorovým pojetím asymetrické závislosti, ukázali jsme v tomto článku problém s dalším prvkem jeho teorie týkajícím se toho, jaké vlastnosti jsou kauzálně operativní v tokenech sémantického symbolu v mozku vnímatele. . Poté, co představíme tento problém, zkoumáme tři možné reakce, které by Fodorian mohl učinit pro naši kritiku., and Tevfik Aytekin ; Erdinç Sayan
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
429. Foreknowledge and free will
- Creator:
- Blum, Alex
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- foreknowledge and freewill
- Language:
- Slovak
- Description:
- We contend that since what is true cannot be false, foreknowledge is transparently incompatible with free will. We argue that what is crucial to the conflict is the role of truth in foreknowledge and that the identity of the one who foreknows is irrelevant., Tvrdíme, že vzhledem k tomu, že to, co je pravdivé, nemůže být falešné, je předzvěst transparentně neslučitelná se svobodnou vůlí. Tvrdíme, že rozhodující pro konflikt je role pravdy v předzvědomí a že identita toho, kdo předvídá, je irelevantní., and Alex Blum
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
430. Foreword
- Creator:
- Schmidt, Martin
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Language:
- Slovak
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public