HH Processes

Abstract

OpenGeoSys was coupled to the pipe flow model HYSTEM-EXTRAN [HE, version 7.7 or newer] (itwh, Kanalnetzberechnung - Hydrodynamische Abfluss-Transport- und Schmutzfrachtberechnung. HYSTEM-EXTRAN 7 Modellbeschreibung, 2014, itw 2010) in order to simulate pipe leakage in a variably saturated subsurface. The newly developed weak coupling scheme is applicable for the Richards flow process in a modified version of OGS 5 that can be downloaded from the custom branch available at https://github.com/APeche/OGS-HYSTEM-EXTRAN.git. The shared-memory-based coupling was implemented using the interprocess communication method Named Pipes, which is considered a cost-effective and easy-to-implement push-migration solution (Laszewski and Nauduri, Migrating to the Cloud, pp. 1–19, 2012, Laszewski and Nauduri 2012). The implementation of the coupling scheme is based on a timestep-wise update of boundary conditions and source terms. Bidirectional interprocess data transfer is realized using in total two Named Pipes. First pipe is the server pipe, mainly used to send the HE-calculated pipe water level $H_{\text {PW}}$ [L] to OGS. In OGS, $H_{\text {PW}}$ is used as a Dirichlet-type boundary condition assigned to the pipe defect surface. It is converted to a hydrostatic pressure p [$M L^{-1} T^{-2}$] using fluid density $\rho$ [$M L^{-3}$] and gravitational acceleration g [$L T^{-2}$] in the form of $p=H_{\text {PW}}\cdot \rho \cdot g$. The second Named Pipe is the client pipe used to send the OGS-calculated leakage flow $Q_{\text {leak}}$ [$L^3 T^{-1}$] to HE, where it is used as a source term. The coupled model will be referred to as OGS-HE.