Hydrodynamic model of groundwater flow in “Bokanjac - Poličnik” aquifer - calibration

Za simulaciju toka podzemnih voda u kršu primjenjuju se razni tipovi determinističkih modela, kao što su model ekvivalentnog poroznog medija (eng. Single-Continuum Porous – Equivalent - SCPE), hibridni model (HM), diskretni model s jednom ili više pukotina. Najjednostavniji pristup od svih je primjena SCPE modela koji se bazira na pretpostavci laminarnog toka te konstantne temperature, gustoće i viskoznosti vode, gdje je tok vođen potencijalnom energijom, tj. gradijentom tlaka. Cilj ovog rada je primijeniti SCPE pristup unutar numeričkog modela Modflow kako bi se simuliralo otjecanje podzemnih voda u krškom vodonosniku “Bokanjac – Poličnik“ te dobio uvid u raspodjelu ekvipotencijala i strujnog polja unutar vodonosnika. Sliv “Bokanjac – Poličnik“ predstavljen je ortogonalnom mrežom s ćelijama dimenzija 200 m x 200 m u horizontalnoj ravnini te s dva sloja u vertikalnom smjeru. Kalibracija se odnosi na 29. siječnja do 30. lipnja 1967. godine (153 dana). Korišteni su podaci dnevnih oborina s ombrografske stanice smještene unutar analiziranog područja. Simulacija je pokazala da se definiranjem pukotina na način da im se pridruže velike vrijednosti koeficijenata propusnosti mogu uspješno opisati pojave unutar vodonosnika, bez upotrebe sofisticiranijih modela kao što je hibridni model (HM).Deterministic models such as Single – continuum porous – equivalent (SCPE), the hybrid model (HM), the discrete single fracture or pipe set model (DSFS), and the discrete multiple fracture or pipe set model (DMFS) have been used in simulating groundwater flow in karst aquifer. The simplest one, the SCPE, is based on laminar flow assumtion with constant temperature, density and viscosity of water where flow can be simulated with the potential flow equation of fluid mechanics. The goal of this paper is to apply SCPE approach within numerical model Modflow in order to simulate groundwater flow in karst aquifer “Bokanjac – Poličnik“ and to get insight into spatial distribution of equipotentials and flow field. Catchment “Bokanjac – Poličnik“ is represented by an orthogonal network with grid spacing of 200x200 m in horizontal plane and with two layers in vertical direction. Calibration period covers period from 29.1.1967 to 30.6.1967 (153 days). Data from nearby ombrographic station ware used. Simulation shows that defining of karst fractures with very large hydraulic conductivity cells in an SCPE approach can successfully describe flow regime within karst aquifer

Comparison of modelled and measured surface wind waves

Prikazana je usporedba rezultata mjerenja i numeričkog modeliranja površinskih vjetrenih valova na Jadranu. Model za valno generiranje uzima podatke o vjetru iz prognoze Aladin. Rabljene su dvije modelske prostorne domene: regionalna (Jadran) i lokalna (kanalski sustav jugoistočnog Jadrana). U lokalnoj domeni upotrijebljena je detaljnija prostorna diskretizacija. Stupanj korelacije izmjerenih i modeliranih vrijednosti primarno ovisi o pouzdanosti ulaznih podataka o vjetru.The comparison between measurement data and numerical modelling results for surface wind waves on the Adriatic is presented. The wave generation model receives wind data from the Aladin forecast. Two spatial model domains are used: regional (Adriatic) and local (south-eastern Adriatic channel system). A detailed spatial discrétisation is used in the local domain. The degree of correlation between the measured and modelled values is primarily dependent on the reliability of input wind data

The (im)possibility of reducing the meteotsunami amplitude by constructing protective breakwaters

Plitkovodni gravitacijski val uzrokovan gibanjem atmosferskog poremećaja povećava svoju amplitudu kroz energetski transfer omogućen Proudmanovom rezonancijom. Nailaskom na lučki bazen oblika lijevka dešava se dodatna amplificija valnog signala. Ukoliko valna grupa koja nailazi sadrži i frekvencije bliske lučkim vlastitim frekvencijama moguća je i pojava rezonancije s daljnjim povećenjem valnih amplituda. Cjelokupna pojava naziva se meteocunami, a primjer te pojave desio se i 21.6.1978. u Veloj Luci, pri čemu su registrirane valne visine od 6 m. U radu je provedena numerička analiza dinamike morskih razi u krajnjoj točki Vele Luke uslijed valne pobude s maksimalnim visinama od 0,19 m ispred ulaza u zaljev Vela Luka. Kao odgovor na valnu pobudu u krajnjoj točki luke dobivene su valne visine od 5,5 m. Analiziran je utjecaj hipotetskih vertikalnih nepropusnih lukobrana, na valne visine u samoj Veloj luci. Korištene su dvije varijante pozicije ispred ulaza u Velu Luku. Modelski rezultati ukazuju na relativno malo smanjenje valnih visina.Shallow water gravity wave caused by motion of atmospheric disturbances increases its amplitude through energy transfer enabled by the Proudman resonance. The waveform signals get further amplified reaching the funnel shaped port basin. If the incoming wave group contains frequencies close to the port\u27s eigen frequencies the resonance with a further increase of wave amplitude is likely to occur. The whole phenomenon is called meteotsunami, and an example of this phenomenon occurred on 21 June 1978 in Vela Luka, where the wave height was registered to be 6 m. The paper deals with carrying out the numerical analysis of the sea level dynamics in the final point brought about due to wave excitation with a maximum height of 0,19 m in front of the entrance to the Vela Luka Bay. In response to the wave excitation in the port\u27s final point, the obtained wave height was 5,5 m. Furthermore, the analysis involving the influence of hypothetical vertical impermeable breakwaters, set on two variant positions outside the entrance to Vela Luka was carried out. The model results indicate that there is a relatively small decrease in wave height

HYDRAULISCH-HYDROLOGISCHE SYNTHESE DES AUSFLUSSES DER KARSTQUELLE GOLUBINKA

Prikazana je hidrauličko-hidrološka analiza i rezultati hidrograma istjecanja za krški izvor Golubinka, što obuhvaća razdoblje 7. rujna 2012. do 1. listopada 2013. Cilj je bio stjecanje uvida u procese koji se javljaju na slivnom području izvora Golubinka, u smislu količine istjecanja, razina podzemne vode i procjeđivanja unutar krškog vodonosnika, u odnosu na količinu oborina izmjerenih tijekom analiziranog razdoblja. Na osnovi dvaju pristupa određen je odgovarajući koeficijent turbulentnog procjeđivanja kroz krške kanale analiziranog vodonosnika koji se potom može koristiti u numeričkom modeliranju.The hydraulic-hydrology analysis and discharge hydrograph results for the Golubinka karst spring are presented for the period from 7 September 2012 to 1 October 2013. The objective was to gain insight into processes occurring in the Golubinka spring drainage area, in terms of quantities of discharge, groundwater levels, and seepage within the karst aquifer, as related to the precipitation measured during the analysed period. An appropriate coefficient of turbulent seepage through karst channels in the analysed aquifer was determined based on two approaches. This coefficient can subsequently be used in numerical modelling.Dargestellt werden die hydraulisch-hydrologische Analyse und die Ergebnisse des Hydrogramms des Ausflusses für die Karstquelle Golubinka, was den Zeitraum vom 7. September 2012 bis zum 1. Oktober 2013 umfasst. Das Ziel war es, Einblick in die Prozesse zu erlangen, die im Wassersammelgebiet der Quelle Golubinka im Sinne der Ausflussmenge, des Grundwasserniveaus und der Filterung innerhalb des Karstgrundwasserleiters auftreten, im Vergleich zur Niederschlagsmenge, die während des analysierten Zeitraums gemessen wurde. Aufgrund zweier Ansätze wurde ein entsprechender Koeffizient der turbulenten Filterung durch die Karstkanäle des analysierten Grundwasserleiters festgelegt, der dann bei der nummerischen Modellierung angewendet werden kann

Hydraulic properties of U-shaped stormwater overflows

Opisuju se hidrauličke karakteristike kišnog preljeva U oblika, alternativnog rješenja kojim se omogućuje smanjenje ukupne duljine preljevne građevine. Prikazani su rezultati hidrauličkih ispitivanja koja su provedena zbog toga što su nedostajali podaci o svojstvima preljeva toga oblika. Ispitivanje na fizikalnom modelu poslužilo je i za optimizaciju preljeva koja je provedena u dva koraka. Opisane su i odgovarajuće numeričke analize radi usporedbe s rezultatima na modelu.Authors describe hydraulic properties of the U-shaped stormwater overflows, which constitute an alternative solution for reducing an overall length of traditional stormwater overflow facilities. Results of hydraulic tests conducted to obtain additional data about properties of such overflows are presented. Physical model tests were also conducted to optimise overflow facilities using a two-step process. Appropriate numerical analyses are also given to enable comparison with scale model results

Near-bottom pollution transport modelling

Opisano je modeliranje pronosa pridneno ispuštenog onečišćenja pri stacionarnom tečenju u kanalu jednolikog pravokutnog presjeka s primjenom dvodimenzionalnih i trodimenzionalnih modela. Osim usporedbe rezultata ravninskog i prostornog numeričkog modeliranja raspodjele koncentracije pridneno ispuštenog onečišćenja u kanalu idealiziranih geometrijskih obilježja, dana je i usporedba reprezentativne veličine tzv. brzine miješanja s rezultatima dobivenim fizikalnim modeliranjem.The near-bottom transport of pollution, discharged during stationary flow into a channel of uniform rectangular cross section, is modelled by means of two-dimensional and three-dimensional models. Comparison between in-plane and three-dimensional numerical modelling results, defining distribution of near-bottom pollution in a channel of idealized geometrical properties, is provided. A comparison between the representative value of the so called mixing velocity, and the results obtained by physical modelling, is also presented

Hydraulic-Hydrology Analysis of the Turbulent Seepage Flow within Karst Aquifer of the Golubinka Spring Catchment

This paper shows the results of the hydraulic-hydrologic calculations of karst spring discharges and the groundwater level in the aquifer of spring catchment. The calculations were performed for the Golubinka spring in Zadar area for the 4-year period. The chosen approach was a model using relatively scarce data set, including limnigraphic data on the difference between the sea water level and the freshwater level on the spring itself and the precipitation data fromthemeteorological station Zadar.The determination of discharge hydrographs, based on inherent assumptions and available data, yields the proportionality coefficients between the discharge and the limnigraphic data on the Golubinka spring itself. Further, based on the discharge hydrograph, groundwater level oscillation was determined.The resulting spring discharge hydrograph and groundwater levels, along with the assumption of Golubinka spring as the only spring on the catchment, were used in creating turbulent seepagemodel of the fractured system within the aquifer, which evidently extends along the axis of theGolubinka spring catchment.Themodel yielded suitable turbulent seepage coefficients of the fracture system. By using the numericalmodel KarstMod it was estimated that, on average, concentrated fracture flow drains around 85% of infiltrated volumes and the remaining 15% accounts for diffuse matrix flow. Finally, theModflow model was used in order to get insight into the flow field and the distribution of equipotentials in the aquifer of the Golubinka catchment

Comparison of results obtained by physical and numerical in-plane flow models

Prikazana je usporedba rezultata proračuna i mjerenja polja brzine strujanja na dionici umirivanja toka i ulijevanja u more za projektno rješenje HE Ombla u područje izvorišne špilje i jezerca. U istraživanjima su uspoređeni rezultati brzina dobiveni mjerenjem na fizikalnom modelu i proračunom ravninskih modela. Rabljena su dva numerička modela temeljeni na metodama konačnih diferencija i volumena. Numerički rezultati uspoređeni su s rezultatima mjerenja na fizikalnom modelu.The comparison of calculated and measured field flow velocities at the flow steadying and sea discharge section, for the zone of the source cave and lake, is presented in the scope of design solution development for the Ombla hydropower plant. Velocity results obtained by physical model measurements and in-plane model analyses are compared. Two numerical models, based on the finite difference and volume methods, are used. Numerical results are compared with results obtained by physical model measurements