In Klingenberg, Schnücke and Xia (Math. Comp. 86 (2017), 1203-1232) an arbitrary Lagrangian-Eulerian discontinuous Galerkin (ALE-DG) method to solve conservation laws has been developed and analyzed. In this paper, the ALE-DG method will be extended to several dimensions. The method will be designed for simplex meshes. This will ensure that the method satisfies the geometric conservation law, if the accuracy of the time integrator is not less than the value of the spatial dimension. For the semi-discrete method the L 2 -stability will be proven. Furthermore, an error estimate which provides the suboptimal (k + 1 2 ) convergence with respect to the L ∞ 0, T ; L 2 (Ω) -norm will be presented, when an arbitrary monotone flux is used and for each cell the approximating functions are given by polynomials of degree k. The two dimensional fully-discrete explicit method will be combined with the bound preserving limiter developed by Zhang, Xia and Shu in (J. Sci. Comput. 50 (2012), 29-62). This limiter does not affect the high order accuracy of a numerical method. Then, for the ALE-DG method revised by the limiter the validity of a discrete maximum principle will be proven. The numerical stability, robustness and accuracy of the method will be shown by a variety of two dimensional computational experiments on moving triangularThe numerical flux function needs to satisfy certain properties. These properties are discussed in the Section 2.4.Finally, on the reference cell, the semi-discrete ALE-DG method appears as the following problem:Problem 1 (The semi-discrete ALE-DG method on the reference cell). Find a function(4.5)Proof. Since f (c) contains merely constant coefficients andthe integration by parts formula providesThus, we obtain the identity (4.5) by (4.6) and (4.7).Next, we assume that u * h = c solves the semi-discrete ALE-DG method Problem 1. Then, we obtain by (4.4) and (4.5)(4.8)
17The equation (4.8) and the ODE (2.12) are equivalent, since c is an arbitrary constant,is an arbitrary test function and the quantitiesare merely time-dependent. We note that the time evolution of the metric terms J K(t) needs to be respected in the time discretization of the semi-discrete ALE-DG method Problem 1. Therefore, we discretize the ODE (2.12) and (4.4) simultaneously by the same TVD-RK method. The stage solutions of the TVD-RK discretization for (2.12) will be used to update the metric terms in the TVD-RK discretization for (4.4).The fully-discrete ALE-DG method: First, the ODE (2.12) is discretized by a s-stage TVD-RK method:where K n+γ j := K (t n + γ j t) and ω n+γ j := ω (t n + γ j t). The stage solutions {J K n,i } s i=0 are used to update the metric terms in the TVD-RK discretization of (4.4). The Runge-Kutta method needs to solve the ODE (2.12) exact such thatwhere T (t n+1 ) is the regular mesh of simplices which has been used in the Section 2.1 to construct the time-dependent cells (2.3). We note that in a d-dimensional space a TVD-RK method with order greater than or equal to d is necessary to compute the metric ...