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The Reynolds decomposition is used to derive a new set of mean-flow equations for linear viscous fluids, with low compressibility (fluids in the liquid state). Additional shear and normal stresses are related to the velocity turbulent fluctuations in order to interpret the considerable energy dissipation in processes which are accompanied by rapid changes in liquid density, at least within the frame of the local thermodynamic equilibrium (LTE) approximation. A constitutive equation for the normal turbulent stresses, which involves the turbulent bulk viscosity, is given. A closure equation for the turbulent bulk viscosity is suggested. In the field of hydraulic engineering, the model is applied to investigate the classical problem of 1D finite amplitude pressure waves propagation in liquid-filled pipes (water hammer phenomenon). Available experimental pressure data are used to calibrate the model parameters and to demonstrate the capability of the proposed theoretical model in reproducing the experimental trials. The model results are discussed with attention paid to the role played by the turbulent bulk viscosity on the energy dissipation processes. [ABSTRACT FROM AUTHOR]

Abstract Human presence, coastal erosion, and tourism activities are increasing the attention to coastal flooding risk. To perform risk assessments, long time series of observed or hindcast wave parameters and tide levels are then necessary. In some cases, only a few years of observation are available, so that observed extreme data are not always representative and reliable. A hindcast system aimed to reconstruct long time series of total tide levels may be of great help to perform robust extreme events analysis and then to protect human life, activities as well as to counteract coastal erosion by means of risk assessments. This work aims to propose a simplified method to hindcast storm surge levels time series in semi-enclosed basins with low computational costs. The method is an extension of a previous work of some of the authors and consists of a mixed approach in which the estimation of storm surge obtained by using the theory of linear dynamic system is corrected by using a statistical method. Both steps are characterized by low computational costs. Nevertheless, the results may be considered reliable enough also in view of the simplicity of the approach. The proposed method has been applied to the Manfredonia case study, a small village located in the Southern Adriatic Italian coast and often prone to coastal flooding events. The comparison of extreme events estimated on the basis of hindcast levels time series is satisfactorily similar to those estimated on the basis of observed tide series. [ABSTRACT FROM AUTHOR]