An understanding of the relationship between the flow generators and harbor design could result in an acceptable seawater renewal into an enclosed basin. The flushing culverts located in the breakwater are the most cost-effective technique for improving water renewal in port engineering. The aim of the paper was to identify and quantify the relation between flow generators and culvert flow to propose an optimal position for the flushing culverts. Mentioned relations are important for designing and positioning the flushing culverts in marinas to achieve optimal sea exchange in the marina basin. Field measurements in the marina Opatija were performed and the data served for calibrating a 3D circulation model and a wave generation/propagation model. The absolute volume of the flow through the culverts caused by wind waves has the more important contribution to the water renewal in the marina basin than the coastal springs have. The optimal flow rates through the culverts are performed by positioning the flushing culvert axis at the mean sea level in accordance with the main incident direction of the propagating waves.Water 2018, 10, 936 2 of 22 discharge, etc.). An understanding of the relationship between the flow generators and harbor design could result in an acceptable seawater renewal with the purpose of reducing pollution concentrations introduced into an enclosed basin [13].Previous scientific research offers mathematical procedures to compute the seawater renewal efficiency of a semi-enclosed basin, frequently grounded either on hydrodynamic or morphological features. Most approaches for seawater renewal estimation are fundamentally built around tidal oscillations as the dominant generator of water circulation inside enclosed basins [14][15][16].The structural features such as the planform geometry of a port, inlet width, water depth, bed slope and so forth, also influence the water renewal efficiency [15][16][17][18]. In regions where the tidal oscillation range is considerably small like the Mediterranean and the Adriatic Sea, the water renewal is also consequently reduced substantially. In these areas, it is widespread to use openings or flushing culverts (pipes or rectangular openings in a breakwater) with the aim of improving the water exchange capacity of the basin [19,20]. Flushing culverts are regarded as the most cost-effective technique for improving water renewal in port engineering. Its purpose is to improve the water renewal within an enclosed basin harnessing also other flow generators like wind and waves, without allowing undesirable wave energy to come into and disturb the port basin. Optimal opening layouts design can be achieved by taking into account two basic yet contradicting criteria, i.e., the water renewal and the wave energy penetration into the harbor [21].Wind action and waves have also been identified to have a significant influence on the seawater renewal. Research making use of numerical models, established to study the Venice lagoon seawater circulation, demonstrated a valuable...

In this work contribution of wind and waves on the water exchange through flushing culverts between the marina and surrounding water body have been investigated. The hybrid modelling technique was used. Results of culvert discharge, produced by waves on physical model, were implemented in 3D circulation model. Using circulation model, the optimum flushing culverts position in body of breakwater was defined for marinas with hypothetical geometry, characteristic for Croatian Adriatic Sea. The model was forced by wind from 8 directions and velocities 1-5 Bf. Furthermore, numerical simulations were also done for a real-world marina-the Ičići marina. The real breakwater geometry and hydrographic conditions (depths, tides, sea temperatures and salinity) were included. The analysis results show that the flushing culverts may have important contribution to seawater exchange in marina, even in summertime situations with significant wave heights of 0.5 m and duration of 6 hours.

In areas with small tidal oscillations (such as the Mediterranean Sea), the exchange of water in harbours can be improved by pipe culverts incorporated in breakwaters. The effect of natural factors on water exchange was tested via in-situ measurements conducted in Opatija marina. It was established that the flow in partly submerged pipe culverts exceeds by two times the flow in a fully submerged pipe culvert. In the period without wind and waves, almost three percent of the total volume circulates through a pipe culvert during a single tidal oscillation. Analiza izmjene vode kroz cijevne propuste u marini OpatijaU područjima s malim oscilacijama plime i oseke (npr. Sredozemno more), izmjena vode u lučicama može se poboljšati pomoću cijevnih propusta ugrađenih u lukobranima. Utjecaj prirodnih čimbenika na izmjenu vode ispituje se pomoću terenskih mjerenja provedenih u marini Opatija. Ustanovljeno je kako protok u djelomično potopljenom cijevnom propustu raste dvostruko više u odnosu na protok u potpuno potopljenom cijevnom propustu. U razdoblju bez vjetra i valova, približno 3 % ukupnog volumena cirkulira kroz cijevni propust tijekom jedne plimne oscilacije. Ključne riječi: izmjena vode, cijevni propusti, vjetar, lukobran, valovi generirani vjetrom Fachbericht Damjan Bujak, Dalibor Carević, Ratko Ramuščak, Tin Kulić, Ivana Bartolić Analyse des Wasseraustauschs durch die Rohrdurchlässe in der Marina Opatija In den Gebieten mit geringen Flut-und Ebbeschwankungen (z. B. Mittelmeer) kann der Wasseraustausch in den Häfen durch Rohrdurchlässe, die in den Hafendamm eingebaut sind, verbessert werden. Der Einfluss natürlicher Faktoren auf den Wasseraustausch wird mithilfe von Feldmessungen, die in der Marina Opatija durchgeführt wurden, untersucht. Festgestellt wurde, dass der Durchfluss in den teilweise versenkten Rohrdurchlässen im Vergleich zum Durchfluss in vollständig versenkten Rohrdurchlässen doppelt so stark ansteigt. Im Zeitraum ohne Wind und Wellen fließen etwa 3% des Gesamtvolumens durch die Rohrdurchlässe während einer Flutschwankung. Schlüsselwörter: Wasseraustausch, Rohrdurchlass, Hafendamm, durch Wind generierte Wellen

The quality of seawater in enclosed water basins can be negatively affected by inadequate exchange of seawater. Various culverts (pipe culverts, box culverts, and duct culverts) are presented in the paper as an efficient solution for preventing stagnation of seawater. In addition to positive influence of culvert-induced higher circulation of seawater in the basin, the wave energy penetrating during stormy weather into the protected area via culverts may be a limiting factor. Basic culvert shaping recommendations, relying on the study of previous research and structural solutions for culverts used on Croatian coast, are also presented in the paper.

This paper presents the results of 2D and 3D numerical simulations of sea circulation and water mass exchange for a marina with hypothetical dimensions (L/B=2 and L/B=0.5) to calculate the return flow factor. The return flow factor b was analyzed in relation to the marina entrance width, sea current velocity outside the marina (0, 1, 2, and 5 cm/s) and the sea surface level oscillation dynamics. The basic comparative parameter is the e-flushing time, Tf. The intensity of forced circulation is calculated to achieve time Tf of less than 10 days. The impact of the wind field on the e-flushing time for different marina widths was analyzed using a 3D numerical model. The numerical simulation results indicate that the e-flushing time Tf depends on the amplitude of the tidal signal, secondary to the width of the marina inlet, and the smallest amount on the velocity field in the outer region. Conversely, the return flow factor b depends on the width of the marina entrance, less on the tidal signal amplitude, and least on the current velocity outside the marina if currents are ≥ 1 cm/s. Forced circulation of 1 m3/s is only required for the marina with a smaller tidal amplitude (position Dubrovnik) to achieve Tf<10 days. If at the observed location wind is a dominant sea circulation generator, a wider marina entrance will allow faster sea exchange.