I modeling of Hydraulic Conductivity in the Regulated Stresams of Southeast Lithuania

The presented work aims to evaluate the changes in hydraulic conductivity and the planning possibilities for the naturalization of regulated streams in the Southeast Lithuania. The investigations have been carried out in sections of the regulated streams Nemėža, Ž–2, Žalesa and Girija. The hydraulic roughness coefficient, varying within 0,030 and 0,094, has been determined on the basis of morphometric parameters of the regulated streams, and on distribution and density of woody vegetation in the cross profile of the channel. Sections of the flood hydraulic conductivity reserve decreased to the water overflow to the valley limit already exist in the regulated streams of southeast Lithuania. Having calculated the hydraulic roughness coefficients, HEC–RAS (River Analysis System) is used to estimate the influence of woody vegetation on the hydraulic conductivity of the stream. According to simulation results in the investigated sections of the regulated streams the hydraulic conductivity reserve is lost when the hydraulic roughness coefficient reaches the limit of 0.060–0.080. Thus, if the channel slopes were overgrown with woody and grass vegetation and the roughness coefficient exceeded 0.060–0.080, the hydraulic conductivity of the channels could be used to reduce the channel roughness to the admissible limit (0.060)

Impact of Land Drainage and Natural Factors on the Changes of the Hydrological Regime of the Tatula River

Impact of the land drainage on the river catchment in Lithuania has so far been evaluated as of rather mixed character as the impact is rather complex and multifaceted. When drainage systems are installed, the hydrographic network of the territory changes and conditions of the formation of catchment may change as well. Implementing naturalisation processes at the regulated sectors of the river, there appear places where the limit of the flood hydraulic conductivity might reach the line of the overflow of the river in the valley. In the article, using the analytical, statistical and mathematical methods of modelling, the impact of land drainage and natural factors on the changes of hydrological regime of the Tatula river is analysed. Areas of the wet land in the basin of the Tatula river form 90 % of all the area. Analysis of the interchanges of excessively wet lands and drained area in 1960– 2009 shows that until 1961, such drained areas reached only 12 % of all the area of wet land, and in 2000 such area reached 94 %. When the biggest part of the basin area was drained, there appeared no essential annual or seasonal differences of the catchment changes. Using HEC–RAS programme for the modelling, it was determined that the coefficient of the hydraulic roughness in the Tatula river changes from 0.028 to 0.049. The water level in the river bed is in all the cases lower than that of the regulated river. Even when the spring debit is maximal, the water in the regulated bed of the river does not overflow. If the coefficient of the river roughness is made higher and reaches 0,160 the water in the bed overflows in all the regulated sectors of the Tatula river

Influence of Woody Vegetation of Regulated Streams in Southeast Lithuania for the Hydraulic Conductivity

The analysis of overgrowing of regulated stream slopes with woody vegetation shows that its distribution on ditch slopes is not uniform. The most favourable conditions for the majority of the species of woody vegetation are on the lower and middle thirds of a slope. At the existing density of woody vegetation (0.01 to 0.68 u.m-2) the roughness coefficient ranged from 0.030 to 0.045. In all investigated stream sections, when spring flood discharge probability is with 10 %, water overflow indicator is positive; the water depth in the bed (zV) of the natural reaches was lower than the depth of a regulated stream (hG). The reserve of hydraulic conductivity in the investigated Nemėža stream section is lost when roughness coefficient reaches 0.080

State of riparian buffer strips of channelised streams

Straipsnyje pateikiami Pietryčių Lietuvos reguliuotų upelių pakrančių apsaugos juostų kokybiniai ir kiekybiniai rodikliai bei jų analizė. Atliekant tyrimus pakrančių apsaugos juostoje rasta 20 sumedėjusios augalijos rūšių, iš jų 12 medžių ir 8 krūmų rūšys. Dažniausia medžių rūšis pakrančių apsaugos juostoje yra baltalksnis (Alnus incana Moench.), karpotasis beržas (Betula pendula Roth.) ir juodalksnis (Alnus glutinosa Gaertn.). Labiausiai paplitusiais krūmais pakrančių apsaugos juostoje laikytini: pilkasis karklas (Salix cineria L.), trapusis gluosnis (Salti fragilis L.) ir paprastasis lazdynas (Corylus avellana L.). Bendras sumedėjusios augalijos tankumas pakrančių apsaugos juostoje r=0,068±0,02 vnt. m"2. Tankiausiai tarp medžių rūšių paplitęs baltalksnis (Alnus incana Moench) - 1,09 • 10~2 vnt. m-2 ir blindė {Salix caprea L.) - 0,51 • 10"2 vnt. m"2. Tankiausiai tarp krūmų rūšių apsaugos juostoje paplitęs pilkasis karklas (Salix cineria L.) - 1,83 ■ 10"2 vnt. m-2 ir trapusis gluosnis {Salix fragilis L.) - 0,82 • 10'2 vnt. m"2. Reguliuotų upelių pakrančių apsaugos juostų tyrimai parodė, kad 81 proc. atvejų šalia reguliuoto upelio buvo pieva ir ganykla. Nemėžos upelio pakrančių apsaugos juostos šalia dirbamosios žemės pločio vidurkis gautas 1,30 m, o Mažojo - tik 0,77 m, tai sudaro atitinkamai tik 52 ir 31 proc. teisės aktais reikalaujamo juostos pločio. Reguliuotų upelių šlaitų apaugimas sumedėjusią augalija turi didesnę įtaką pakrančių apsaugos juostų apaugimui, nes reguliuotų upelių šlaituose sumedėjusi augalija dažnai nenaikinama (čia jos gausiau), be to, pakrančių apsaugos juostose jai augti sunkesnės sąlygos tiek drėgmės, tiek ūkiniu požiūriaisThe article presents an analysis of the qualitative and quantitative indices of riparian buffer strips along the channelised streams in the southeast of Lithuania. During the research, 20 types of woody vegetation were found in these strips, consisting of 12 types of trees and 8 types of bushes. The most common tree types are grey alder (Alnus incana Moench.), common birch (Betula pendul Roth.) and black alder {Alnus glutinosa Gaertn.). The most common bushes were grey willow (Salix cineria L.), brittle willow (Salix fragilis L/) and European hazelnut (Corylus avellana L.). The total vegetation density was derived using the formula r=0.068±0.02 units nr2. The greatest tree densities were those of grey alder (Alnus incana Moench.) 1.09 • lO'2 units nr2, and common willow (Salix caprea L.) 0.51 ■ 10"2units m*2. The greatest bush densities were those of common sallow (Salix cineria L.) 1.83 • 10"2units nr2, and brittle willow (Salix fragilis L.) 0.82 • 10"2 units nv2. The research showed that 81% of the riparian buffer strips had a meadow or a pasture nearby. The average width of the riparian buffer strip at the Nemeza stream is 1.30m and at the Mazasis stream it is only 0.77 m, which is respectively only 52% and 31% of the strip width required by juridical acts. The overgrowth of channelised streams by woody vegetation has a large influence on the overgrowth of the riparian buffer strips, as the overgrown vegetation found there is not destroyed (it is plentiful). The growing conditions in the riparian buffer strips are also more difficult with regard to levels of humidity and agricultureVytauto Didžiojo universitetasŽemės ūkio akademij

Sumedėjusios augalijos paplitimo ir rūšinės sudėties tyrimai reguliuotuose Pietryčių Lietuvos upeliuose

Vytauto Didžiojo universitetasŽemės ūkio akademij

Modelling of hydraulic permeability of regulated streams

Straipsnyje pateiktas reguliuotų Pietryčių Lietuvos upelių, apaugusių sumedėjusia augalija, funkcionalumo (hidraulinio pralaidumo) modeliavimas ir galimybės planuoti reguliuotų upelių natūralizavimą. Sumedėjusios augalijos tyrimai atlikti Neries upės baseine. Įvertinus šiurkštumo įtaką Nemėžos upelio hidrauliniam pralaidumui nustatyta, kad tiriamajame ruože sumedėjusios augalijos tankumas kinta nuo 0,01 iki 0,68 vnt. m-2. Esant dabartiniam sumedėjusios augalijos tankumui hidrauliniais skaičiavimais nustatytas šiurkštumo koeficientas siekė 0,025-0,045. Esant natūriniais tyrimais įvertintam šiurkštumo koeficientui visuose tirtuose upelio ruožuose, kai pavasario potvynio debitas 10 % tikimybės, vandens išsiliejimo rodiklis teigiamas, vandens lygis vagoje (hV) visais atvejais mažesnis negu reguliuoto upelio gylis (hG). Anksčiau minėtame Nemėžos upelio ruože hidraulinio pralaidumo atsarga prarandama, kai šiurkštumo koeficientas pasiekia 0,080. Toliau didinant upelio ruožuose šiurkštumo koeficientą (0,081-0,135), kai pavasario potvynio debitas 10 % tikimybės, 8-iuose iš 23-jų ruožų vandens išsiliejimo rodiklis neigiamas, vagoje minimos tikimybės debitas netelpa. Padidinus šiurkštumo koeficientą iki 0,140, vanduo išsilieja 10-yje ruožų, padidinus iki 0,160 - 19-oje ruožų; kai šiurkštumo koeficientas 0,170, vandens išsiliejimo rodiklis neigiamas visuose nagrinėjamuose upelio ruožuoseThe article presents the functionality (hydraulic permeability) modelling of the regulated Southeast Lithuanian streams overgrown with woody vegetation and the possibilities to plan naturalization of the regulated streams. The research of woody vegetation was carried out in the Neris river basin. Having evaluated the influence of hydraulic roughness (Manning coefficient of roughness) on hydraulic permeability of the Nemėža stream it was established that the density of woody vegetation in the investigated section varied from 0.01 to 0.68 u. m-2. At the existing density of woody vegetation the hydraulic roughness established by hydraulic calculations reached 0.025-0.045. Under present hydraulic roughness coefficient assessed by natural investigations in all investigated stream sections, when spring flood discharge probability is 10%, water overflow indicator is positive; the water level in the bed (hV) is in all senses lower than the depth of a regulated stream (hG). The reserve of hydraulic permeability in the investigated Nemėža stream section is lost when roughness coefficient reaches the limit of 0.080. A further increase of roughness coefficient in the stream sections (0.081-0.135) results in the overflow of spring flood discharge of 10% probability in 8 of 23 sections, and in this case water overflowing indicator is negative. The increase of roughness coefficient up to 0.140 results in water overflowing in 10 sections; increase of up to 0.160 – in 19 sections and when roughness coefficient reaches 0.170, water overflowing indicator is negative in all investigated sections of the streamVytauto Didžiojo universitetasŽemės ūkio akademij

Skysčių mechanika, techninė termodinamika

Mokomoji knyga parengta pagal „Skysčių mechanikos ir termodinamikos“ modulių programas. Jame pateikiamos pagrindinės skysčių mechanikos ir techninės termodinamikos žinios, nagrinėjančios skysčių pusiausvyros ir tekėjimo dėsnius. Aptariamos skysčių fizikinės savybės, hidrostatinis slėgis ir slėgio jėga, skysčio tekėjimo lygtys, hidrauliniai nuostoliai, vamzdžių ir vamzdynų bei angų ir antgalių hidrauliniai skaičiavimai. Knygoje pateikiamas trumpas įvadinis techninės termodinamikos kursas. Studentams pateikiami pagrindiniai techninės termodinamikos procesų analizės principai, supažindinama su idealizuotų procesų vertinimo ir analizės pradmenimis. Leidinys skirtas VGTU Mechanikos, Statybos pagrindinių ir tęstinių studijų studentams. Juo galės naudotis ir kitų universitetų studentai, kurių studijų programose yra „Skysčių mechanikos ir termodinamikos“ ar panašūs moduliai

Numerical and Field Investigations of Local Bridge Abutment Scour and Unsteady Downstream River Flow From a Nearby Hydropower Plant

Sudden and often fluctuations of water discharges and levels in the downstream reach of the hydropower plant make water fauna and flora existence conditions unbearable. Besides, a riverbed here is subjected to long lasting and intensive scour and deformations. The aim of our investigations is to develop measures improving the water flow regime in the downstream reach of the hydropower plants. The Nemunas River and Kaunas hydropower plants were selected as basis for our numerical and field investigations. Actual flow regime below the hydropower plant was observed and analysed on the ground of the long lasting dynamic measurement data. Numerical treatment of field measurement data and flow simulation works were arranged and carried out simultaneously. Numerical hydrodynamic model MIKE 21 made it possible to evaluate existing river flow conditions and to apply the model for simulation of many different turbine regimes and to select the optimal one. The content of our research was as follows: 1) analysis of typical turbines regimes while switching them on and off and flow regimes downstream; 2) continuous long lasting measurement of water level in many cross-sections of the river under investigation downstream the hydropower plants; 3) numerical simulation and investigation of untypical turbines regimes while switching them on and off and flow regimes downstream with application software MIKE 21 in the same unsteady flow conditions in which field measurements were made; 4) evaluation of the accuracy of hydrodynamic modeling results and possibilities for their application in predicting the local bridge abutment scour. The obtained data on water level and flow rate dynamics downstream the Kaunas hydropower plants have been analysed. Numerical model was developed to simulate the scour at bridge abutment and was calibrated for the same unsteady flow conditions. The obtained accurate results can be used for local bridge abutment scour evaluation

Numerical and field investigations of local bridge abutment scour and unsteady downstream river flow from a nearby hydropower plant

Staigūs ir dažni vandens debito ir lygio svyravimai upės ruože žemiau hidroelektrinės sukelia intensyvius ir ilgai trunkančius bendruosius ir vietinius upės vagos dugno išplovimus, kurie gali kelti grėsmę hidrotechnikos ir kitiems upių statiniams. Šiuo požiūriu ypač svarbios yra vagos dugno deformacijos ties tiltų atramomis bei jų tyrimų metodai. Šio darbo tikslas – nustatyti nenusistovėjusio tekėjimo dėsningumus upės ruože žemiau hidroelektrinės ir jos poveikį tilto atramų vietinio išplovimo dėsningumams. Modeliniams ir lauko tyrimams buvo pasirinkta Nemuno upė žemiau Kauno hidroelektrinės. Atlikti natūriniai tyrimai ir tėkmės modeliavimas pagal sinchroniškai išmatuotą vandens lygių dinamiką. Skaitmeninis hidrodinamikos modelis leido įvertinti upės nenusistovėjusios tėkmės charakteristikas ir dugno deformacijų ties tilto atrama dėsningumus. Buvo sprendžiami tokie uždaviniai: 1) išanalizuoti charakteringi Kauno hidroelektrinės darbo režimai, sukeliantys nenusistovėjusį tekėjimą žemutiniame hidroelektrinės bjefe; 2) atlikti natūriniai sinchroniniai vandens lygių dinamikos Nemune ties Kaunu matavimai kintant Kauno hidroelektrinės darbo režimams; 3) skaitmeniniame hidrodinamikos modelyje su MIKE 21 programine įranga ištirta Nemuno hidraulinių charakteristikų dinamika tomis pat nenusistovėjusio vandens tekėjimo sąlygomis, kuriomis buvo atliekami natūriniai tyrimai; 4) įvertintas hidrodinamikos modeliavimo rezultatų tikslumas ir jų naudojimo tiltų atramų vietiniams išplovimams prognozuoti galimybės. Tyrimais nustatyta, kad nenusistovėjusio tekėjimo modeliavimas su MIKE 21 programine įranga leidžia gauti tikslius rezultatus, kurie gali būti panaudoti tilto atramų vietinio išplovimo gyliams skaičiuotiSudden and often fluctuations of water discharges and levels in the downstream reach of the hydropower plant make water fauna and flora existence conditions unbearable. Besides, a riverbed here is subjected to long lasting and intensive scour and deformations. The aim of our investigations is to develop measures improving the water flow regime in the downstream reach of the hydropower plants. The Nemunas River and Kaunas hydropower plants were selected as basis for our numerical and field investigations. Actual flow regime below the hydropower plant was observed and analysed on the ground of the long lasting dynamic measurement data. Numerical treatment of field measurement data and flow simulation works were arranged and carried out simultaneously. Numerical hydrodynamic model MIKE 21 made it possible to evaluate existing river flow conditions and to apply the model for simulation of many different turbine regimes and to select the optimal one. The content of our research was as follows: 1) analysis of typical turbines regimes while switching them on and off and flow regimes downstream; 2) continuous long lasting measurement of water level in many cross-sections of the river under investigation downstream the hydropower plants; 3) numerical simulation and investigation of untypical turbines regimes while switching them on and off and flow regimes downstream with application software MIKE 21 in the same unsteady flow conditions in which field measurements were made; 4) evaluation of the accuracy of hydrodynamic modeling results and possibilities for their application in predicting the local bridge abutment scour. The obtained data on water level and flow rate dynamics downstream the Kaunas hydropower plants have been analysed. Numerical model was developed to simulate the scour at bridge abutment and was calibrated for the same unsteady flow conditions. The obtained accurate results can be used for local bridge abutKauno technologijos universitetasVilniaus Gedimino technikos universitetasVytauto Didžiojo universitetasŽemės ūkio akademij

The Road of Experimental Pavement Structures: Experience of Five Years Operation

The road of experimental pavement structures was constructed in 2007 and still continues its operation. The road consists of 27 different pavement structures with the same class of pavement structure but the different type and composition of materials. The experimental pavement structures were laid on the road to the query, one traffic lane is used by loaded traffic and other – by unloaded traffic. In May, 2012 totally 320 000 ESAL’s (100 kN) passed the road. Annually – about 70 000 ESAL’s. This article gives the research results of the bearing capacity and surface characteristics of experimental pavement structures after five years of their service