Časová proměnlivost hydraulických vlastností půdy a jejich vliv na odhad půdní vlhkosti
Šípek, Václav; Vlček, Lukáš; Tesař, Miroslav; Zelíková, Nikol; Hnilica, Jan
2023 - Czech
Půdní vlhkost hraje významnou roli v hydrologickém cyklu, protože zásadně ovlivňuje proudění vody v systému voda-půda-rostlina. Studie je zaměřena na celoroční odhad nasycení půdního profilu vodou v zalesněném horském území s využitím jednoduchého modelu založenému na konceptu lineární nádrže. Studie je založena na terénním měření nasycené hydraulické vodivosti a zavedení periodické funkce nasycené hydraulické vodivosti do modelu půdní vlhkosti, která možní její sezónní proměnlivost. \nPrůměrná nasycená hydraulická vodivost měřená jednoválcovým infiltrometrem byla v průběhu dvou let vždy vyšší ve vegetačním období, kdy se pohybovala od 33,6 do 44,8 cm hod-1, oproti zimním období, kdy poklesla do rozmezí 13,2 až 22,3 cm hod-1. Do modelu půdní vlhkosti byla implementována funkce, která umožnila spojitou změnu nasycené hydraulické vodivosti s maximem ve vegetační sezóně a minimum v zimním období. Tato modifikace modelu půdní vlhkosti vedla k poklesu průměrné čtvercové chyby odhadu půdní vlhkosti o 33,2 % (z 0,034 cm3cm-3 na 0,023 cm3cm-3) a nárůstu hodnoty Nash-Sutcliffova koeficientu z 0,34 na 0,68. Výsledky studie přispějí k přesnějšímu celoročnímu odhadu půdní vlhkosti, a tedy i ke zlepšení dlouhodobých simulací vlivu klimatické změny na dostupnost vodních zdrojů.\n The study was focused on the temporal variability of saturated hydraulic conductivity in an experimental plot covered by spruce forest and investigated benefits of its incorporation into soil water balance model. The results showed that the higher saturated hydraulic conductivity (33.6-44.8 cm hr-1) was observed in summer period compared to lower values (13.2-22.3 cm hr-1) in the winter period. The use of seasonally variabile saturated hydraulic conductivity improved the efficiency of soil water balance model in terms of lower root mean square error between observed and simulated volumetric soil water content by 33.2 %. The Nash-Sutcliffe coefficient rose from 0.34 to 0.68.
Keywords:
soil moisture; soil hydraulic properties; saturated hydraulic conductivity; climate change
Fulltext is available at external website.
Časová proměnlivost hydraulických vlastností půdy a jejich vliv na odhad půdní vlhkosti
Půdní vlhkost hraje významnou roli v hydrologickém cyklu, protože zásadně ovlivňuje proudění vody v systému voda-půda-rostlina. Studie je zaměřena na celoroční odhad nasycení půdního profilu vodou v ...
Kam a kolik vody odvádí stromy? Modelování vlivu smrkových a bukových porostů na toky vody v půdě během extrémních klimatických podmínek
Zelíková, Nikol; Šípek, Václav
2023 - Czech
Půdní vlhkost propojuje takové procesy, které ovlivňují celý hydrologický cyklus, a tím i dostupnost vodních zdrojů. Jedním z významných faktorů ovlivňující tyto procesy je přítomnost vegetace. Výzkum interakcí mezi vegetací, jejím managementem a procesy ovlivňující toky půdní vody nabývá na významu zejména v době probíhajících klimatických změn i změn krajinného pokryvu. Avšak komplexnost těchto interakcí, ovlivněná navíc jejich rozdílností mezi jednotlivými rostlinnými druhy tento výzkum ztěžuje. Proměna krajinného pokryvu probíhá také v českém lesnictví, konkrétně v podobě obměny smrkových monokultur buky. V této studii je proto zkoumán vliv dvou typů lesních porostů, smrku ztepilého (Picea abies) a buku lesního (Fagus sylvatica), na vodní režim půdy v experimentálním povodí Liz na Šumavě. A to (1) zjištěním rozdílů v množství půdní vláhy na základě dvaceti let naměřených dat a (2) získáním složek vodní bilance (transpirace a perkolace) na těchto dvou kontrastních plochách pomocí modelu bilance půdní vody. Z analýzy dlouhodobých dat půdních vlhkostí vyplývají nepatrně nižší hodnoty půdních vlhkostí pod porosty buku, které zanikají při srovnání průměrných ročních hodnot. Odlišnosti jsou patrné při hodnocení průměrných vlhkostí s hloubkou, kde v nejsvrchnější vrstvě půdního profilu smrk disponuje v průměru o 6 % vyššími zásobami půdní vody než buk. Z pohledu vývoje půdních vlhkostí během vegetační sezóny je půda z počátku sušší pod smrkem, který započíná svou transpiraci dříve. Tento rozdíl je v průběhu sezóny zredukován intenzivní transpirací buku. Výstupy bilančního modelu poukázaly na vyšší míru aktuální evapotranspirace buku a vyšší míru perkolace smrku během každého roku. Tento jev byl zvýrazněn během suchých let, kdežto v letech s dostatkem srážek byly rozdíly minimální. Zvýšení četnosti buku v krajině, tak může ovlivnit míru dotace podzemních vod. Soil moisture links processes that influence the entire hydrological cycle and thus the availability of water resources. One important factor influencing these processes is the presence of vegetation. Research on the interactions between vegetation, its management and the processes affecting soil water fluxes is of particular importance in times of ongoing climate change and land cover changes. However, the complexity of these interactions, further influenced by differences between plant species, makes this research more difficult. Land cover change is also taking place in Czechia, specifically in the replacement of spruce monocultures by beech. Therefore, this study investigates the influence of two types of forest stands, spruce (Picea abies) and beech (Fagus sylvatica), on the soil water regime in the experimental Liz catchment in Bohemian Forest, Czechia. This was performed by (1) evaluating differences in soil moisture based on twenty years of measured data and (2) obtaining the two components of the soil water balance (transpiration and percolation) at two plots (beech and spruce) using a soil water balance model. Analysis of the long-term soil moisture data show slightly lower soil moisture values under the beech stands, which disappear when comparing the annual mean values. Differences are evident when evaluating average soil moisture data with depth, where the topmost layer of the soil profile at the spruce site has on average 6% higher soil water content than beech. At the start of the growing season the soil moisture was initially drier under spruce, due to its earlier start of transpiration. This difference was reduced over the season by the intensive transpiration of beech. The outputs of the balance model indicated a higher rate of actual evapotranspiration of beech and a higher rate of percolation of spruce every year. This effect was more pronounced over the dry years, whereas in years with sufficient rainfall the differences were minimal. Thus, the replacement of spruce trees by beech trees may affect the rate of groundwater recharge.
Keywords:
soil water balance; transpiration; percolation; land cover change; drought
Fulltext is available at external website.
Kam a kolik vody odvádí stromy? Modelování vlivu smrkových a bukových porostů na toky vody v půdě během extrémních klimatických podmínek
Půdní vlhkost propojuje takové procesy, které ovlivňují celý hydrologický cyklus, a tím i dostupnost vodních zdrojů. Jedním z významných faktorů ovlivňující tyto procesy je přítomnost vegetace. Výzkum ...
Teplotní režim lesních horských půd
Dohnal, M.; Votrubová, J.; Mazúchová, R.; Blunár, P.; Tesař, Miroslav
2023 - Czech
S postupující automatizací, digitalizací a lepší dostupností pokročilých meteorologických a hydrologických přístrojů pro kontinuální sledování malých povodí jsou metody a postupy vycházející z bilance energie stále častěji vyhodnocovány v subdenním časovém kroku. V těchto případech již není možné dostupnou energii ztotožnit s čistou radiací a zanedbat tok tepla do půdy. Nevhodně zavedené předpoklady o velikosti toku tepla do půdy nebo použití příliš zjednodušených výpočetních postupů k jeho určení, vnášejí do zdánlivě přesnějších, ale ve skutečnosti pouze v čase podrobnějších, výpočtů značné nejistoty. Monitoring teplotního režimu půd a toků tepla do půdy, tak má velký význam pro ověření používaných výpočetních postupů a lepší pochopení omezení plynoucích z dlouhodobě využívaných předpokladů. Contribution deals with the monitoring of the temperature regime of forest soils and the soil heat flux at small mountainous basins Liz in the Šumava Mts. and Uhlířská in the Jizera Mts. Soil temperatures are measured with the help of soil moisture meters (Pt100 at Liz basin and CS107 at Uhlířská basin), the soil heat flux is measured with the use of the sensor Hukseflux HFP01. Measured results were statistically evaluated, the analysis of the consistence of the measurement was done and cumulative soil heat fluxes were calculated for the individual hydrological years.
Keywords:
soil temperature; heat flux; HUKSEFLUX; Liz catchment
Fulltext is available at external website.
Teplotní režim lesních horských půd
S postupující automatizací, digitalizací a lepší dostupností pokročilých meteorologických a hydrologických přístrojů pro kontinuální sledování malých povodí jsou metody a postupy vycházející z bilance ...
Thermal and creep analysis of VVER-1000 reactor pressure vessel at high temperatures caused by fuel melting during severe accident
Gabriel, Dušan; Gál, P.; Kotouč, M.; Dymáček, Petr; Masák, Jan; Kopačka, Ján
2023 - English
Thermal and creep analysis of the VVER-1000 reactor pressure vessel (RPV) was performed at high temperatures caused by fuel melting during severe accident. First, the integral code ASTEC was applied simulating severe accident evolution since an initiating event up to a hypothetical radioactive release into the environment. The ASTEC outputs including the remaining RPV wall thickness, the heat flux achieved and the temperature profile in the ablated vessel wall served as boundary conditions for the consequent assessment of RPV integrity carried out with the aid of finite element method (FEM). The FEM analysis was performed including the creep behaviour of RPV material using a complex creep probabilistic exponential model with damage. The objective of the analysis was to computationally assess emergency condition and, on this basis, to propose a general methodology for evaluating the integrity of RPV at high temperatures due to fuel melting during severe accident.
Keywords:
integrity of reactor pressure vessel; severe accident; ASTEC; creep; FEM
Fulltext is available at external website.
Thermal and creep analysis of VVER-1000 reactor pressure vessel at high temperatures caused by fuel melting during severe accident
Thermal and creep analysis of the VVER-1000 reactor pressure vessel (RPV) was performed at high temperatures caused by fuel melting during severe accident. First, the integral code ASTEC was applied ...
Simulation of heterogeneously-catalyzed non-isothermal reactive flow in industrial packed beds
Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
2023 - English
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. An industrial real-life heterogeneous catalysis is complex process that combines fully three-dimensional mass, momentum and energy transport on several scales. In the present work, we leverage our previously developed CFD solver for non-isothermal heterogeneously catalyzed reactive flow based on the finite volume method and couple it with our\nin-house DEM-based method for preparation of random packed beds. The resulting framework is verified in the simplified cases against available analytical solutions and correlations and is used to study an industrially-relevant case of ethylene oxychlorination performed in a tubular packed bed comprising CuCl2-coated catalyst carrying particles. In particular, we compare properties of three different industrially used catalyst carrying particles: Raschig rings, Reformax, and Wagon wheels
Keywords:
CFD; OpenFOAM; non-isothermal flow
Available in a digital repository NRGL
Simulation of heterogeneously-catalyzed non-isothermal reactive flow in industrial packed beds
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. An industrial real-life heterogeneous catalysis is complex process that ...
Numerical implementation of incremental minimization principle for materials with multiple rate-independent dissipative mechanisms
Frost, Miroslav; Moskovka, Alexej; Sedlák, Petr; Valdman, Jan
2023 - English
The incremental energy minimization approach is a compact variational formulation of the evolutionary boundary value problem for constitutive models of materials with a rate-independent response. Although it can be easily applied to many conventional models, its main advantages arise when applied to models with multiple strongly coupled dissipation mechanisms, where the direct construction of the coupled yield conditions and flow rules may be challenging. However, this usually requires a more complex numerical treatment of the resulting sequence of time-incremental boundary value problems resolved via the finite element method. This contribution presents, compares and discusses two genuine minimization approaches - the staggered solution procedure relying on alternating minimization and the monolithic approach employing global minimization - for an advanced constitutive model of shape memory alloys.
Keywords:
variational approach; constitutive modeling; numerical implementation
Fulltext is available at external website.
Numerical implementation of incremental minimization principle for materials with multiple rate-independent dissipative mechanisms
The incremental energy minimization approach is a compact variational formulation of the evolutionary boundary value problem for constitutive models of materials with a rate-independent response. ...
Astrophysical black holes embedded in organized magnetic fields
Karas, Vladimír
2023 - English
Large-scale magnetic fields pervade the cosmic environment where the astrophysical black holes are often embedded and influenced by mutual interaction. In thiscontribution, we outline the appropriate mathematical framework to describe magnetized black holes within General Relativity, and we show several examples of how these can be employed in the astrophysical context. In particular, we examine the magnetized black hole metric in terms of an exact solution of electro-vacuum Einstein-Maxwell equations under the influence of a non-vanishing electric charge. New effects emerge: the expulsion of the magnetic flux out of the black-hole horizon depends on the intensity of the imposed magnetic field.
Keywords:
black holes; electromagnetic fields; general relativity
Fulltext is available at external website.
Astrophysical black holes embedded in organized magnetic fields
Large-scale magnetic fields pervade the cosmic environment where the astrophysical black holes are often embedded and influenced by mutual interaction. In thiscontribution, we outline the appropriate ...
Implementation of wall functions into a hybrid fictitious domain-immersed boundary method
Kubíčková, Lucie; Isoz, Martin
2023 - English
Hybrid fictitious domain-immersed boundary method (HFDIB) is a simulation approach used in computational fluid dynamics. The approach avoids usage of complex geometry-conforming computational domains. Instead, a simple domain is used and the geometry is projected onto it by a scalar field and adjustment of governing equations. Hence, the time spent on mesh generation is substantially reduced. It is advantageous to use the HFDIB in geometry optimizations where it allows for a massive optimization speed-up. Nevertheless, there is a problem with simulation of the fluid behavior in the boundary layer in the vicinity of the immersed walls. Especially, in simulation of highly turbulent flows, where the boundary layer is very thin and the usage of finer mesh is unaffordable. In this work, we aim to solve this problem by implementation of Reynolds averaged turbulence models in our custom HFDIB variant. In particular, we implemented the k-ω turbulence model and blended wall functions for closure variables and velocity.
Keywords:
wall functions; immersed boundary method; CFD; RAS
Fulltext is available at external website.
Implementation of wall functions into a hybrid fictitious domain-immersed boundary method
Hybrid fictitious domain-immersed boundary method (HFDIB) is a simulation approach used in computational fluid dynamics. The approach avoids usage of complex geometry-conforming computational domains. ...
Model order reduction of transport-dominated systems with rotations using shifted proper orthogonal decomposition and artificial neural networks
Kovárnová, A.; Isoz, Martin
2023 - English
In the present work, we concentrate on particle-laden flows as an example of industry-relevant transport-dominated systems. Our previously-developed framework for data-driven model order reduction (MOR) of such systems, the shifted proper orthogonal decomposition with interpolation via artificial neural networks, is further extended by improving the handling of general transport operators. First, even with intrusive MOR approaches, the underlying numerical solvers can provide only discrete realizations of transports linked to the movement of individual particles in the system. On the other hand, our MOR methodology requires continuous transport operators. Thus, the original framework was extended by the possibility to reconstruct continuous approximations of known discrete transports via another artificial neural network. Second, the treatment of rotation-comprising transports was significantly improved.
Keywords:
model order reduction; CFD; shifted POD
Fulltext is available at external website.
Model order reduction of transport-dominated systems with rotations using shifted proper orthogonal decomposition and artificial neural networks
In the present work, we concentrate on particle-laden flows as an example of industry-relevant transport-dominated systems. Our previously-developed framework for data-driven model order reduction ...
Development, validation, and application of a solver for non-isothermal non-adiabatic packed bed reactors
Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
2023 - English
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. The main contribution of our work is the development of a numerical model applicable to simulations of such reactors. The developed model is based on the finite volume method, couples the momentum, mass and energy balances, and is free of any empirical closures. As such, the solver falls into the domain of the direct numerical simulation. In the talk, we will (i) present the new solver fundamental working principles, (ii) report on the verication of each of the solver components against existing literature data and (iii) demonstrate an application of the solver on an industrially relevant case of ethylene oxichlorination performed in a tubular reactor packed with Raschig rings coated by CuCl2 catalyst.
Keywords:
CFD; oxichlorination; heterogenous catalysis
Fulltext is available at external website.
Development, validation, and application of a solver for non-isothermal non-adiabatic packed bed reactors
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. The main contribution of our work is the development of a numerical model ...
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