detailed programme - SIMS - Scandinavian Simulation Society

elements, simulations can be ran in parallel on multi-core processors. At the
same time, equation-based modelling offers an intuitive way of writing models.
This paper presents an algorithm for generating distributed models from Modelica
code using bilinear transform. This also enables hard limitations on variables and
their derivatives. The generated Jacobian is linearised and solved using LUdecomposition.
The algorithm is implemented in the Hopsan simulation tool.
Equations are transformed and differentiated by using the SymPy package for
symbolic mathematics. An example model is created and verified against a
reference model. Simulation results are similar, but the equation-based model is
four to five times slower. Further optimisation of the algorithm is thus required.
The long-term aim is to develop a distributed simulation environment with
support for equation-based modelling.
Authors: Robert Braun, Petter Krus.
Organization: Linköping University
Paper 2
Title: A homogeneous two-phase flow model of an evaporator with internal rifled
tubes
Keyword: Two phase flow, Evaporator, Internal rifled boiler tubes, Central WENO
solver, Hyperbolic balance laws
Abstract: In this article is developed numerical model for solving a transient one
dimensional compressible homogeneous two phase model, on the basis of a two
layer model for predominantly one-dimensional flows in a vertical pipe element
with internal rifles. The two layer model uses a non-equilibrium approach and
consist of two continuity equations, two momentum equations and two energy
equations. The homogeneous model is based on the assumption of both
hydraulic- and thermal equilibrium and the consequences and aspects will be
discussed in that contest. The homogeneous flow model consists of three
hyperbolic fluid conservation equations; continuity, momentum and energy and
the pipe wall is modelled as a one dimensional heat balance equation. The models
can be reformulated in the four un-dependant DOF's p(pressure), h(enthalpy)
u(velocity) and T_w(wall temperature). Constitutive relations for the
thermodynamic properties are limited to water/steam and is given by the IAPWS
97 standard and wall friction and heat transfer coefficients are formulated by
Churchill's friction model and by Jirous respectively.
The numerical method for solving the homogeneous fluid equations is presented.
The numerical method is based on a fifth order Central WENO scheme, with
simplified weights functions.
God convergence rate is established and the model is able to describe the entire
evaporation process from sub cooled water to super heated steam at the outlet.
Authors: Axel Ohrt Johansen, Brian Elmegaard.
Organization: DONG Energy – Thermal Power, Technical University of Denmark
– Thermal Energy Systems.
Paper 21
Title: Hydro Power Systems: Scripting Modelica Models for Operational Studies in
Education
Keyword: hydro-power-systems, modeling, simulation, education, optimization,
open-source
Abstract: The Telemark University College is running a master degree program
called ``System and Control Engineering''.
Most students of that program have a background in either electrical, mechanical,
control engineering or a combination of those.
Since Norway covers about 99\% of its electrical energy demand using hydroelectric
power plants it is natural to also educate master students in the subject
of hydro power systems.