Non-dispersive conservative regularisation of nonlinear shallow water (and isothermal Euler) equations

21 pages, 6 figures, 1 table, 35 references. Other author's papers can be downloaded at http://www.denys-dutykh.com/A new regularisation of the shallow water (and isentropic Euler) equations is proposed. The regularised equations are non-dissipative, non-dispersive and possess a variational structure. Thus, the mass, the momentum and the energy are conserved. Hence, for instance, regularised hydraulic jumps are smooth and non-oscillatory. Another particularly interesting feature of this regularisation is that smoothed `shocks' propagates at exactly the same speed as the original discontinuous ones. The performance of the new model is illustrated numerically on some dam-break test cases, which are classical in the hyperbolic realm