Lohmayer M (2025)
Publication Language: English
Publication Type: Thesis
Publication year: 2025
URI: https://www.ltd.tf.fau.de/files/2025/11/dissertation-lohmayer.pdf
This thesis introduces
a novel, compositional, and thermodynamically consistent
modeling language for multiphysical systems,
encompassing those governed by the principles of
classical mechanics, electromagnetism, and thermodynamics.
At its core,
the language builds on
port-Hamiltonian systems theory.
By interpreting the Hamiltonian
as an exergy storage function,
the inherent passivity of port-Hamiltonian systems
is fully reconciled with
nonequilibrium thermodynamics.
Akin to metriplectic systems and the GENERIC formalism,
additional structural properties
ensure that
both the first and second laws of thermodynamics
are guaranteed.
Inspired by bond graphs,
the modeling language features
a simple graphical syntax,
which is built upon a specialization of
the multicategory of undirected wiring diagrams.
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The compositional syntax not only enables
the hierarchical decomposition of complex systems
into simple reusable parts
but also facilitates communication among
human experts, non-experts, AI language models,
and computational tools
for simulation, optimization, and control.
The structured, energy-based approach
aims to promote
systematic enhancement and reusability of models
across diverse scientific and engineering domains.
To demonstrate the utility of the framework,
the thesis examines two advanced applications:
First,
it is shown that the modeling language
can serve as a modular multibody framework.
While the mathematical formulation
of the primitive subsystems
is based on the Lie group
of Euclidean isometries,
the compositional approach allows users to work
with higher-level abstractions,
starting with bodies and joints.
Second,
the thesis considers a series of
fluid and plasma models.
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Specifically,
an ideal fluid model
is reused as a subsystem of
a Navier-Stokes-Fourier model,
which in turn is reused as a subsystem of
two different plasma models.
The hierarchical decomposition reveals
how increasingly complex models
are built from
simpler and ultimately primitive subsystems
that represent
energy storage
as well as reversible and irreversible dynamics.
The graphical syntax
naturally expresses the interconnection of subsystems
through shared energy domains.
APA:
Lohmayer, M. (2025). Exergetic Port-Hamiltonian Systems: a compositional, energy-based language for modeling mechanical, electromagnetic, and thermodynamic systems (Dissertation).
MLA:
Lohmayer, Markus. Exergetic Port-Hamiltonian Systems: a compositional, energy-based language for modeling mechanical, electromagnetic, and thermodynamic systems. Dissertation, 2025.
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