* Corresponding author. Tel.: #91 (03222) 55222-4405; fax: (03222) 55303; e-mail: bsri@civil.iitkgp.ernet.in. Finite Elements in Analysis and Design 32 (1999) 85 — 96 Time-domain analysis of infinite reservoir by finite element method using a novel far-boundary condition D. Maity, S.K. Bhattacharyya* Department of Civil Engineering, Indian Institute of Technology, Kharagpur-721302, India Received 2 December 1998; accepted 2 December 1998 Abstract The focus of the present paper is on the time-domain analysis of a dam—reservoir system using a novel far-boundary condition to model an infinite fluid domain to a finite one. The method is based on the finite element discretization of the complete system assuming only pressure to be the nodal unknown parameter and the fluid to be compressible. The truncation boundary condition is derived numerically from the classical wave equation. Studies show the accuracy of the proposed far-boundary condition, using finite element method, while comparing with the existing ones available in the literature.  1999 Elsevier Science B.V. All rights reserved. Keywords: Finite element method; Far-boundary; Hydrodynamic pressure 1. Introduction The estimation of precise hydrodynamic forces on dam faces due to earthquakes is an important aspect of the analysis and design of dams. The first rigorous analysis of hydrodynamic pressures acting on vertical rigid dams was reported by Westergaard [1] in 1933. Since then, many contributions to this subject have been reported in the open literature. In 1978, Chwang [2] obtained analytical solution for sloping dams considering water to be incompressible. In most of the practical problems, it is difficult to obtain a closed form analytical solutions due to complex topographical conditions of the systems (Fig. 1). Due to varied geometric forms of structures and the irregular geometries of the fluid domain, the finite element method is recognised to be a powerful numerical tool for solving such practical problems. Generally the reservoir domain is much larger than that of the structure, so that it is necessary to arbitrarily truncate the reservoir region in order to have a manageable computational domain. In the finite element analysis of such 0168-874X/99/$ — see front matter  1999 Elsevier Science B.V. All rights reserved PII: S 0 1 6 8 - 8 7 4 X ( 9 8 ) 0 0 0 7 7 - 8