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1544. Modeling annual maximum peak flows at various dams and barrages in Pakistan

Creator:
Muhammad, Faqir and Afreen, Shazia
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Gumbel, generalized extreme value distribution, probability weighted moments, peaks over threshold model, power comparisons, všeobecné extrémne hodnoty, pravdepodobnosťou vážené momenty, maximálne prietoky ročné, maximálne prietoky nad určitou hranicou, porovnanie mocnín, and empirické rozdelenia pravdepodobností (EDF)
Language:
Slovak
Description:
The main focus of this paper is to find a suitable distribution for the hydrology series of six catchments in Pakistan. Among others Gumbel and Generalized Extreme Value (GEV) distributions were implemented for frequency analysis using Probability weighted moments (PWM) and maximum likelihood (ML) methods for estimating the parameters. Based on goodness of fit tests it was found that GEV distribution fits closely and PWM method is best suited for estimating the parameters. Peaks over threshold (POT) series model was also tried which resulted in favor of GEV distribution. The quantile estimates based on aforementioned distributions also revealed that GEV distribution has been found close to the observed values of annual maximum peak (AMP) flows. Power comparison studies using various goodness of fit tests for Gumbel and GEV distributions using Log-normal and Weibull as alternative distributions at different levels of significance and for different sample sizes n = 10, 30, 50 showed that Anderson Darling (AD) test is more powerful test followed by Modified Anderson Darling (MAD), Cramer Von Mises (CVM) and Kolmogorov Smirnov (KS) test. and Príspevok je zameraný na odvodenie vhodného rozdelenia pravdepodobností hydrologických radov šiestich povodí v Pakistane. Spomedzi iných sa použili rozdelenia Gumbela a jeho štandardnej extrémnej hodnoty (GEV), s odvodením parametrov metódou momentov vážených pravdepodobnosťou (PWM) a metódou maximálnej pravdepodobnosti (ML) pre analýzu početností. Na základe testov zhody sa zistilo, že na odhad parametrov je najvhodnejšia metóda PWM, a že najlepšia zhoda je pre GEV rozdelenie. Model s výberom maxím nad určitou hranicou (POT) sa tiež použil, s najlepšou zhodou tiež pre rozdelenie GEV. Odhady kvantilov uskutočnené podľa vyššie uvedených rozdelení tiež potvrdili, že tieto pre rozdelenie GEV sú blízke pozorovaným hodnotám ročných maxím (AMP). Porovnanie mocnín (PC) sa tiež uskutočnili pri použití rôznych testov zhody. Pre rozdelenia podľa Gumbela a GEV, alternatívne tiež rozdelenia podľa Weibulla a Logaritmicko-normálne, sa pre súbory s veľkosťou n = 10, 30, 50 členov ako najúčinnejšie ukázali nasledujúce testy na rôznych hladinách významnosti: podľa Andersona Darlinga (AD) ako najúčinnejšieho, nasledoval modifikovaný Anderson Darling (MAD), podľa Cramera von Missesa (CVM) a Kolmogorova-Smirnova (KS).
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1545. Modeling of sand-water slurry flow through horizontal pipe using CFD

Creator:
Gopaliya, Manoj Kumar and Kaushal, D.R.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
CFD, slurry flow, particle size, solid concentration, and pipeline
Language:
Slovak
Description:
The paper presents three-dimensional CFD analysis of two-phase (sand-water) slurry flows through 263 mm diameter pipe in horizontal orientation for mixture velocity range of 3.5-4.7 m/s and efflux concentration range of 9.95- 34% with three particle sizes viz. 0.165 mm, 0.29 mm and 0.55 mm with density 2650 kg/m3 . RNG k-ε turbulence closure equations with Eulerian multi-phase model is used to simulate various slurry flows. The simulated values of local solid concentration are compared with the experimental data and are found to be in good agreement for all particle sizes. Effects of particle size on various slurry flow parameters such as pressure drop, solid phase velocity distribution, friction factor, granular pressure, turbulent viscosity, turbulent kinetic energy and its dissipation have been analyzed.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1546. Modeling of the land management influence on soil water budget for the case of heavy soils in depression

Creator:
Zaradny, Henryk
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
water flow, water uptake by plants, farmers’ activities, two-dimensional mathematical model, prúdenie vôd, odber vody rastlinami, farmárske činnosti, and dvojrozmerný matematický model
Language:
Slovak
Description:
In the paper the results of measurements and two dimensional mathematical simulation for polder in the depression for 1996 are presented. The mathematical model takes into account hydraulics conductivity of soils in form of tensors, water uptake by plants and elastic capacity of soils. In the last decade in Poland many hectares of field culture changed not only ownership, but also the manner in which it was farmed. It also refers to polders with compound soil profiles and complex water conditions. Often in such areas, alluvial soils and relatively high water tables occur. These conditions are preferred in grassland as opposed to arable land farming. Very often these rules are forgotten by new farmers or they stop farming or they use their land for other activities due to bad crop yield; turning it to - for example - grasses and weeds from mowed ditches and dikes store. This causes conflicts between farmers and the holder of the melioration system or the water reservoir in the vicinity. An example of such a situation is a small polder where soil water conditions are influenced by the reservoir with retained water levels between about 0 - 1.5 m above the surface of the surrounding land. It is concluded that if the beginning of the vegetation season (April) is wet, the moisture conditions are unfavourable for crop production. But if April is dry, then even if the rest of the season is wet, the moisture conditions will still be satisfactory. This conclusion was derived from presented results of simulation. It is true only if farmers’ activities are responsible and rational for such soil and water conditions. and Štúdia prezentuje výsledky pozorovaní a dvojrozmernej matematickej simulácie poldra v depresii za rok 1966. Matematický model uvažuje s hydraulickou vodivosťou pôd v tenzorovom tvare, odberom vody rastlinami a pružnou kapacitou pôd. V poslednom desaťročí sa v Poľsku zmenili nielen vlastnícke pomery na veľkej ploche poľnohospodárskych kultúr, ale aj spôsob, akým boli obrábané. Týka sa to aj poldrov so zložitými pôdnymi profilmi a vodným režimom. Často ide o plochy s aluviálnymi pôdami a pomerne vysokou hladinou vody. Takéto podmienky sú vhodnejšie pre trávnaté porasty ako pre hospodárenie na oráčinách. Noví hospodári často zabúdajú na tieto zásady, často prestávajú hospodáriť na týchto pôdach alebo ich využívajú na iný účel z dôvodu nízkych úrod. Tieto sa tak často zmenia na skládky napr. trávy a burín z vykášaných priekop a hrádzí. Toto spôsobuje konflikty medzi farmármi a správcami melioračných sústav alebo nádrží v ich blízkosti. Príkladom takéhoto stavu je malý polder, kde vodné pomery pôd ovplyvňuje vodná nádrž s pohybom hladín okolo 0–1,5 m nad povrchom okolitých pôd. Záverom sa konštatuje, že ak počiatok vegetačnej sezóny (apríl) je vlhký, celkové vlhkostné podmienky sú pre úrodu nepriaznivé. Ak je však naopak apríl suchý, potom aj ak je zvyšok vegetačnej sezóny vlhký, celkove vlhkostné podmienky budú dostatočné. Tento záver vyplynul z uvedených výsledkov simulácie. Bude to tak však iba v prípade zodpovedných a rozumných činností farmára, dotýkajúcich sa pôdnych a vlhkostných podmienok.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1547. Modeling sediment concentration and discharge variations in a small Ethiopian watershed with contributions from an unpaved road

Creator:
Guzman, Christian D., Tilahun A., Seifu A., Dagnew, Dessalegn C., Zegeye, Assefa D., Tebebu, Tigist Y., Yitaferu, Birru, and Steenhuis, Tammo S.
Type:
article, model:article, and TEXT
Subject:
saturation excess runoff, infiltration excess (Hortonian) runoff, soil erosion, Ethiopian highlands, and PED model
Language:
Slovak
Description:
Drainage of paved and unpaved roads has been implicated as a major contributor of overland flow and erosion in mountainous landscapes. Despite this, few watershed models include or have tested for the effect roads have on discharge and sediment loads. Though having a model is an important step, its proper application and attention to distinct landscape features is even more important. This study focuses on developing a module for drainage from a road and tests it on a nested watershed (Shanko Bahir) within a larger previously studied site (Debre Mawi) that receives overland flow contributions from a highly compacted layer of soil on an unpaved road surface. Shanko Bahir experiences a sub-humid monsoonal climate and was assessed for the rainy seasons of 2010, 2011, and 2012. The model chosen is the Parameter Efficient Distributed (PED) model, previously used where saturation-excess overland flow heavily influences discharge and sediment concentration variation, though infiltration-excess occasionally occurs. Since overland flow on unpaved surfaces emulates Hortonian flow, an adjustment to the PED model (the developed module) advances possible incorporation of both flow regimes. The modification resulted in similar modeling performance as previous studies in the Blue Nile Basin on a daily basis (NSE = 0.67 for discharge and 0.71 for sediment concentrations). Furthermore, the road while occupying a small proportion of the sub-watershed (11%) contributed importantly to the early discharge and sediment transport events demonstrating the effect of roads especially on sediment concentrations. Considerations for the dynamic erodibility of the road improved sediment concentration simulation further (NSE = 0.75). The results show that this PED modeling framework can be adjusted to include unpaved compacted surfaces to give reasonable results, but more work is needed to account for contributions from gullies, which can cause high influxes of sediment.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1548. Modelling and numerical simulation of groundwater flow in the reparian alluvial aquifer

Creator:
Burger, František
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
stream-Aquifer model, model calibration/verification, MODFLOW, water regime, natural state, model povrchový tok-kolektor, kalibrácia a verifikácia modelu, vodný režim, and prírodý stav
Language:
Slovak
Description:
The objective of this study is to make a conceptual and numerical model of the groundwater flow system which will improve the understanding of the groundwater cycle in the area of the Čenkov Valley, Slovakia. Extreme deficits of atmospheric precipitation and thereof resulting periods of low water flows and discharges could very negative impact the water management. Increasing water consumption in the future will be the most critical in strong and intensive dry periods. Almost every climatic zone could suffer from drought, although its features could considerably vary from region to region. The study is handling with creating, calibration and verification of numerical model of groundwater flow in the reparian alluvial aquifer of the Čenkov Valley in south-east part of the Danubian lowland for minimal anthropogenic disrupted natural conditions in the past and quasi-steady deficit water regime of the area. The conceptual model is based on data from earlier studies in the area complemented with data collected in the field. Results of model solutions are presented in the study - groundwater level, filtration velocity vectors, groundwater paths by particle tracking and water budget of study area. Created numerical model could be used for simulation of underground dam function, which belongs to the types of artificial recharge of reparian alluvial aquifer management, and also for creating prognostic scenarios concerning expected climatic changes. Additional future work may include adding a solute transport model to the flow model. and Cieľom predloženej štúdie je vytvorenie koncepčného a numerického modelu systému prúdenia podzemnej vody na území Čenkovskej nivy na Slovensku. Extrémne deficity atmosférických zrážok a z toho vyplývajúce obdobia nízkych vodných stavov a prietokov môžu vplývať na vodné hospodárstvo veľmi negatívne. Zvýšená spotreba vody bude v budúcnosti najkritickejšia práve počas drasticky suchých periód. Takmer každá klimatická zóna môže trpieť suchom, hoci jeho charakteristiky sa môžu od regiónu po región značne líšiť. Štúdia sa zaoberá tvorbou, kalibráciou a verifikáciou numerického modelu prúdenia podzemnej vody v pririečnom hydrogeologickom kolektore Čenkovskej nivy v juhovýchodnej časti Podunajskej roviny, za minimálne antropogénne narušených prírodných podmienok v minulosti a kvázi ustáleného deficitného vodného režimu územia. Koncepčný model je založený na údajoch z predošlých štúdií doplnených o údaje zhromaždené v teréne. V štúdii sú prezentované výsledky modelového riešenia - poloha hladiny podzemnej vody, vektory filtračnej rýchlosti, smery prúdenia podzemnej vody prostredníctvom trasovania pohybu častíc a vodná bilancia územia. Vytvorený numerický model môže byť využitý na simuláciu funkcie podzemnej priehrady, ktorá patrí medzi typy umelého nasycovania pririečneho aluviálneho kolektora a tiež pri tvorbe prognostických scenárov, zaoberajúcich sa klimatickými zmenami. Doplnková budúca štúdia sa môže venovať pripojeniu transportného modelu chemických látok k prezentovanému tokovému modelu.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1549. Modelling free surface flow with curvilinear streamlines by a non-hydrostatic model

Creator:
Zerihun, Yebegaeshet T.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
curvilinear flow, finite difference method, hydraulic structures, hydrodynamics, non-hydrostatic pressure, and nonuniform flow
Language:
Slovak
Description:
This study addresses a particular phenomenon in open channel flows for which the basic assumption of hydrostatic pressure distribution is essentially invalid, and expands previous suggestions to flows where streamline curvature is significant. The proposed model incorporates the effects of the vertical curvature of the streamline and steep slope, in making the pressure distribution non-hydrostatic, and overcomes the accuracy problem of the Saint-Venant equations when simulating curvilinear free surface flow problems. Furthermore, the model is demonstrated to be a higher-order one-dimensional model that includes terms accounting for wave-like variations of the free surface on a constant slope channel. Test results of predicted flow surface and pressure profiles for flow in a channel transition from mild to steep slopes, transcritical flow over a short-crested weir and flow with dual free surfaces are compared with experimental data and previous numerical results. A good agreement is attained between the experimental and computed results. The overall simulation results reveal the satisfactory performance of the proposed model in simulating rapidly varied gravity-driven flows with predominant non-hydrostatic pressure distribution effects. This study suggests that a higher-order pressure equation should be used for modelling the pressure distribution of a curvilinear flow in a steeply sloping channel.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1550. Modelling of ground water flow in nonhomogeneous media using an integral equation method

Creator:
Hoření, Bohumír
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
ground water flow, numerical model, integral equations, proudění podzemní vody, numerický model, and integrální rovnice
Language:
Slovak
Description:
The paper presents the basic assumptions and relations for underlying the solution of ground water flow using an integral equations method. The basic laws of physics used for this solution are briefly introduced. The mathematical model describes the flow in a saturated domain both for the spatial and the plane problems. The principal parts of the numeric solution of the problem are treated in more detail. To provide an example of an application, a simple model of a dike is presented. For a homogeneous, isotropic dike the solution describes the development of the flow with time and the corresponding changes to the free surface of ground water. The resulting steady-state flow through the dike is compared with the published results (Polubarina-Kočina, 1952). Another example describes the flow through an nonhomogeneous, isotropic dike if a variable hydraulic conductivity depends on the geometric height. Singularities distributed within the domain are used for an iterative solution of the nonlinear partial differential equation describing the ground water flow. and Příspěvek uvádí základní předpoklady a vztahy pro řešení proudění podzemní vody metodou integrálních rovnic. Stručně jsou uvedeny základní fyzikální zákony potřebné pro řešení. Matematický model popisuje proudění v nasycené oblasti jak pro prostorovou, tak i pro rovinnou úlohu. Podrobněji jsou probrány hlavní části numerického řešení problému. Příkladem aplikace je jednoduchý model hráze. Řešení sleduje vývoj proudění v čase a odpovídající změny volné hladiny podzemní vody pro homogenní isotropní hráz. Výsledný ustálený stav proudění hrází je porovnán s výsledky publikovanými v literatuře (Polubarina-Kočina, 1952). Další příklad popisuje proudění nehomogenní isotropní hrází se součinitelem filtrace proměnným v závislosti na geometrické výšce. Pro iterační řešení nelineární parciální diferenciální rovnice proudění podzemní vody jsou využity singularity rozložené uvnitř oblasti.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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