This paper deals with studying of two topics – measuring of velocity profile deformation behind a over-flooded construction and modelling of this velocity profile deformation by computational fluid dynamics (CFD). Numerical simulations with an unsteady RANS models - Standard k-ε, Realizable k-ε, Standard k-ω and Reynolds stress models (ANSYS Fluent v.18) and experimental measurements in a laboratory flume (using ADV) were performed. Results of both approaches showed and affirmed presence of velocity profile deformation behind the obstacle, but some discrepancies between the measured and simulated values were also observed. With increasing distance from the obstacle, the differences between the simulation and the measured data increase and the results of the numerical models are no longer usable.
The channel network at this region was built up for drainage and also to provide irrigation water. The water level in the whole channel network system affect groundwater level and viceverse. From the view of mutual interaction between channel network and groundwater it has been necessary to assess impact of channel network silting on this interaction. The measurements of thickness of silts along three main channels were carried out in 1993. Then in 2004 there were done measurements in selected profiles along three channels: Aszód, Gabčíkovo-Topoľníky and Komárňanský channel. The paper shows changes in measured thickness and volume of silt in particular channels. It was shown the channel silting up has not been changed significantly during the monitored period. This fact is documented by graphical presentation of silt thicknesses of channels. The differences between silt top and channel bottom levels are presented. and Obsahom príspevku je hodnotenie zmien stavu kanálovej siete Žitného Ostrova z hľadiska zanesenia kanálov dnovými nánosmi v období rokov 1993 až 2004. Kanálová sieť bola vybudovaná v tomto regióne v priebehu 19. storočia jednak na čiastočné odvodnenie územia a zároveň na zabezpečenie závlah. Hladina vody v kanáloch ovplyvňuje výšku hladiny podzemnej vody v ich okolí a naopak. Z hľadiska procesu vzájomnej interakcie kanálovej siete s okolitou podzemnou vodou je nevyhnutné venovať pozornosť vplyvu zanášania kanálov dnovými nánosmi, keďže tieto môžu v značnej miere tento proces ovplyvňovať. V roku 1993 boli merané zanesenia kanálovej siete ŽO na vopred stanovených priečnych profiloch niektorých hlavných kanálov. V priebehu rokov 2004 boli vykonané kontrolné merania zanesenia vo vybraných profiloch kanálov Aszód, Gabčíkovo-Topoľníky a Komárňanského kanála. Tieto kontrolné merania sa robili vždy v úseku na začiatku, v strede a na konci jednotlivých kanálov, pretože sa uvažovalo s predpokladom lineárnych zmien hrúbok nánosov pozdĺž kanálov. Grafickými prílohami príspevok dokumentuje skutočnosť, že v priebehu sledovaného obdobia nedošlo k podstatným zmenám zanesenia kanálovej siete. Keďže pre účely príspevku sú dôležité hrúbky nánosov (teda rozdiely medzi dnom kanála a vrchom nánosovej vrstvy), bolo postačujúce, aby kontrolné merania boli robené od hladiny a neboli vztiahnuté na nadmorské výšky.
The spatial and temporal patterns of surface water (SW) - groundwater (GW) exchange are significantly affected by riverbed silting, clogging or erosion processes, by altering the thickness and hydraulic conductivity of riverbed sediments. The duration of SW-GW exchange is controlled by the drainage and infiltration resistance of river bottom sediments (e.g. Andrássy et al., 2012). Generally, these two parameters primarily depend on the hydraulic conductivity and on the thickness of clogged layer. In this study the flow processes between GW and SW were modeled by model TRIWACO for different infiltration resistance and drainage resistance of riverbed sediments. The model area is situated on the Rye Island, which is a lowland area with very low slope. In this area a channel network was built up, where the flow conditions are controlled by water-gates. Because of the low slope and the system of water gates built on the channels, the riverbeds are influenced by intensive clogging processes. First, the applicability of model TRIWACO in the study area was tested by modelling the response of GW on SW level fluctuation. It was simulated, how the regulation of water level and flow direction in the channels influence the GW level, especially in extreme hydrological conditions (drought/flood), and if the GW flow direction and GW level change as it was expected. Next, the influence of channel network silting up on GW-SW interaction was modeled. The thickness of riverbed sediments was measured and their hydraulic conductivity from disturbed sediment samples was evaluated. The assessed hydraulic conductivity was used to calculate the infiltration resistance and the drainage resistance of riverbed sediments in the study area. Then, the GW level and flow direction was simulated for different infiltration resistance and drainage resistance of sediments.