Modeling the dynamics of flow in gas pipelines
The description of nonstationary one-dimensional flow of a nonideal gas in a pipe is treated with the goal of developing a mathematical description of flow and pressure (density) dynamics adequate for creating a simulation model of large pipeline networks, the analysis starts from Newton's equation of motion. The continuity equation, and the energy equation. The authors determine the relationships among: space discretization, terms of Newton's equation, and frequency of the dynamic processes occurring in the system. The resulting dynamic description of a pipe is discussed for two different modes of space discretization, and quantitative rules for space discretization are given.
Transient simulation of natural gas distribution systems by means of medium-sized process computers
Modelling and simulation of transient flow and pressure in natural gas distribution networks can provide useful tools with respect to pipeline system planning, forecasting, dispatching, and security. An adequate digital computer program for these purposes should provide the following features - the program must match the real process dynamics in a sufficently accurate way, - the program must be capable to be run on a medium-sized process computer, - for on-line purposes the program must be designed such that computations of the transients in the real process can be performed faster than in real-time. These points are discussed in detail for an existing simulation program, called GANESI. Some aspects of using such a program in an interactive version for computer aided design purposes and for on-line applications such as dispatching are also pointed out.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).