Ravanski model interakcije vode, nanosa i zagađivača u prirodnim vodotocima

Abstract

U okviru ovog rada je razvijen ravanski model koji sadrži sve važne aspekte interakcije vode, nanosa i zagađivača u prirodnim vodotocima. Model obuhvata procese strujanja vode, oba oblika kretanja nanosa (suspendovani i vučeni), mehanizme razmene mase između nanosa u suspenziji i nanosa u aktivnom sloju, deformacije korita usled erozije i deponovanja nanosnog materijala, mehanizme razmene mase između nanosa u aktivnom sloju i aktivnom stratumu, kao i procese transporta nekonzervativne zagađuju´ce materije koja je u interakciji sa nanosom preko procesa adsorpcije/desorpcije. Formulisane jednačine transporta zagađivača obuhvataju njegovu pojavu u rastvorenom i adsorbovanom obliku. Razmena između dva vida pojave zagađivača (rastvoreni i adsorbovani) je opisana preko kinetickih procesa prvog reda, pri cemu je modelisanje koeficijenata razmene usko povezano sa dostupnom povrˇsinom za adsorpciju. Sa druge strane, razmena između materije adsorbovane na suspendovani nanos, odnosno materije adsorbovane na nanos u aktivnom sloju je neposredno vezana za nanosne procese uvlačenja zrna u suspenziju i deponovanja istih iz suspenzije. Početni šematski testovi su podrazumevali proveru razvijenog algoritma za rešavanje advektivnih članova jednačina. Druga grupa šematskih testova je podrazumevala implementaciju razvijenog modela transporta zagađujuće materije, pri čemu su testirani i kvalitativno ocenjeni mehanizmi razmene i interakcije. Za testiranje modela na primerima aluvijalnih vodotokova izabrane su dve deonice reke Dunav. Prva lokacija se nalazi u pograniˇcnoj zoni između Mađarske i Srbije gde su testirani aspekti modela koji se odnose na proracun tečenja i ponašanje nanosa. Druga deoncia se nalazi kod Beograda gde je, pored proračuna strujanja i nanosa, vršena analiza modela transporta zagađujuće materije obuhvatajući sve relevantne mehanizme i aspekte izučavanih procesa. Upoređivanjem terenskih merenja i rezultata proračuna je konstatovano da razvijeni model može simulirati interakciju vode, nanosa i zagađivača u prirodnim vodotocima sa zadovoljavajucom tačnošću i pouzdanošću.

This work presents the development of a two-dimensional model for flow, sediment and pollutant interaction in natural watercourses. The model incorporates water flow computation, both aspects of sediment transport (suspended and bed-load), the mechanisms of exchange between suspended and bed sediment, bed evolution due to erosion and deposition, the mechanisms of exchange between active layer and active stratum sediment, as well as the processes of nonconservative pollutant transport including its interaction with sediment particles by adsorption/desorption. Deriving the governing equations for pollutant transport included the dissolved and adsorbed pollutant. The exchange between the dissolved and adsorbed pollutant was described using a first order kinetic process, while the modeling of the exchange coefficients remained closely related to the sediment surface available for adsorption. On the other hand, the exchange between the pollutant adsorbed on suspended sediment and the pollutant adsorbed on active layer sediment was directly related to the sediment processes of entrainment and deposition. Numerical tests included the evaluation of the developed algorithm for advection terms. The second group of numerical tests targeted the pollutant transport model, with the emphasis on the mechanisms of exchange and interaction. For field test cases two reaches of the Danube River were used. The first reach was located in the border area between Hungary and Serbia. Field data collected there was used to analyze the developed model’s ability to simulate flow and sediment transport. Data collected on the second reach near Belgrade was used to perform flow, sediment and pollutant transport simulations, taking into account all the relevant mechanisms of the studied processes. Comparing the computed and measured values, it was concluded that the developed model is able to simulate the interaction of flow, sediment and pollutant in natural watercourses with acceptable precision and reliability.