L1d is a computer code for the quasi-one-dimensional modelling of the gas-dynamic processes within transient-flow facilities. The class of facilities that can be modelled includes free-piston shock tunnels, expansion tubes and light-gas guns. The simulation can include multiple (interacting) gas slugs, pistons and diaphragms but the primary flow interactions have to be along the axis of the facility.
The numerical modelling is based on a quasi-one-dimensional, Lagrangian description of the gas dynamics coupled with engineering correlations for viscous effects and point-mass dynamics for piston motion. This essentially means that the code tracks a number of fixed masses of gas (and pistons) as they travel along a tube of varying area. A simulation can include slugs of gas (consisting of a large number of fixed-mass gas cells) pushing on, or being pushed by, a number of pistons. As in real facilities, the interactions between gas slugs can be controlled by the inclusion of diaphragms which can be set to rupture when specified pressure differences are exceeded.
For further details on the theory built into the program, see the companion Report 13/98. This document contains the following sections:
Last Updated: 20-Jan-1999, 15-Jul-2005 P. A. Jacobs