doi:10.2166/hydro.2020.002engMartínez-Aranda, S.Ramos-Pérez, A.García-Navarro, P.A 1D shallow-flow model for two-layer flows based on FORCE scheme with wet-dry treatmentART-2020-120633The two-layer problem is defined as the coexistence of two immiscible fluids, separated by an interface surface. Under the shallow-flow hypothesis, 1D models are based on a four equations system accounting for the mass and momentum conservation in each fluid layer. Mathematically, the system of conservation laws modelling 1D two-layer flows has the important drawback of loss of hyperbolicity, causing that numerical schemes based on the eigenvalues of the Jacobian become unstable. In this work, well-balanced FORCE scheme is proposed for 1D two-layer shallow flows. The FORCE scheme combines the first-order Lax-Friedrichs flux and the second-order Lax-Wendroff flux. The scheme is supplemented with a hydrostatic reconstruction procedure in order to ensure the well-balanced behaviour of the model for steady flows even under wet-dry conditions. Additionally, a method to obtain high-accuracy numerical solutions for two-layer steady flows including friction dissipation is proposed to design reference benchmark tests for model validation. The enhanced FORCE scheme is faced to lake-at-rest benchmarking tests and steady flow cases including friction, demonstrating its well-balanced character. Furthermore, the numerical results obtained for highly unsteady two-layer dambreaks are used to analyse the robustness and accuracy of the model under a wide range of flow conditions.2020http://zaguan.unizar.es/record/13077910.2166/hydro.2020.002http://zaguan.unizar.es/record/130779oai:zaguan.unizar.es:130779info:eu-repo/grantAgreement/ES/MICINN-FEDER/PGC2018-094341-B-I00JOURNAL OF HYDROINFORMATICS 22, 5 (2020), 1015-1037All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess