17 th International Conference on Environmental Science and Technology Athens, Greece, 1 to 4 September 2021 Numerical Modelling of Wave Reflection from Port Structures for Reliable Forecasting of Berth Downtime CHONDROS M. 1,3, *, MALLIOURI D. 1 , METALLINOS A. 1,3 , PAPADIMITRIOU A. 1,3 , KARAMBAS T. 2 , MAKRIS C. 2 , BALTIKAS V. 2 , KONTOS Y. 2 , NAGKOULIS N. 2 , ANDROULIDAKIS Y. 2 , KLONARIS G. 4 , TSOUKALA V. 1 , and MEMOS C. 1 1 Laboratory of Harbour Works, School of Civil Engineering, National Technical University of Athens, Zografou Campus, 9, Iroon Polytechniou Str., 15780, Zografou, Greece 2 Laboratory of Maritime Engineering, School of Civil Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece 3 Scientia Maris, 15234, Agias Paraskevis Str. 117, Chalndri Greece 4 Department of Geography, Ghent University, Krijgslaan 281, BE-9000 Ghent, Belgium *corresponding author: e-mail: chondros@hydro.ntua.gr Abstract: Forecast of wave agitation inside port basins and consequent downtime of berth positions are of utmost importance to make a port “smarter” by efficiently managing its infrastructure. Within Accu-Waves project (http://accuwaves.eu), a decision-making tool is being developed to provide forecast data on prevailing sea states in the vicinity of port entrances and inside harbour basins. The said tool will be based on cooperating hydrodynamic models that derive data from global scale, open sea forecasts. The implementation of the project includes development and application of a hydrodynamic circulation model, a spectral wave propagation model and a phase-resolving wave model for port basins. The latter is based on the hyperbolic mild-slope (HMS) equations, capable of simulating wave propagation and reflection. In order to achieve higher levels of simulation accuracy in the vicinity of waterfront structures, we need to robustly model the reflection of incipient waves from such structures (e.g., quay walls). In the present paper, this need is met through the incorporation of an additional, case- specific eddy viscosity coefficient to the governing mild- slope equations (of the phase-resolving wave model). This coefficient accounts for the energy dissipation on port structures’ fronts and its value is decided based on the corresponding reflection coefficient. A basic set of incident wave scenarios are simulated, required in investigating the numerics of reflection by the corresponding eddy viscosity coefficients in the wave model. Our pilot investigation refers to numerical experiments for several cases of waves approaching an either fully or partially reflective vertical quay wall. The proposed methodology could enhance similar HMS models; its results should be valuable for port operators. Keywords: port downtime, wave reflection, quay walls, numerical modelling, smart ports 1. Introduction Sea-state forecast platforms and applications are of utmost importance for the rapidly expanding field of e- Navigation. However, the existing online modelling applications do not provide high-resolution sea level and wave climate forecasts at port scale, i.e., sea-state conditions adjacent to harbor protection structures and inside port basins (Makris et al. 2021). To accomplish the latter, a wave propagation model (Karambas and Samaras 2017; Makris et al. 2019) is incorporated within the Accu- waves project (Memos et al. 2019) to provide forecast data on prevailing sea states in the vicinity of port entrances and inside basins (Makris et al. 2021). The model is based on the 2-DH, depth-integrated, harmonic, hyperbolic formulation of the mild-slope (HMS) equation for wave propagation (Copeland 1985). The governing equations utilized for mass and quantity of motion for linear wave propagation in coastal waters of mildly sloping beds can be written as: + ( ) + ( ) =0 (1) + 1 ( 2 ) − 1 ℎ() = ℎ 2 2 + ℎ 2 2 − (2) + 1 ( 2 ) − 1 ℎ() = ℎ 2 2 + ℎ 2 2 − (3) where is the instantaneous surface elevation, and are the wave induced depth-integrated horizontal velocities along the and axes, respectively, is the still water depth, is the wave (phase) celerity, = 2/ is the wave angular frequency with the wave period, ℎ is the horizontal eddy viscosity coefficient coping with wave breaking, and is the normalized bed friction coefficient. Partial and full reflection of waves impinging on harbour structures can be modelled based on an updated version of Karambas and Bowers’s (1996) modelling approach by adding an extra dissipation term in the right-hand-side (r.h.s.) of the momentum equations (2) and (3) and including a further turbulent eddy viscosity coefficient . It is noted that if the relfection coefficient of waves from harbour structures is known a priori, the aforementioned