Research in Engineering Physics

Aerospace & Dynamics

Our faculty are actively involved in research in several sub-fields of aerospace engineering. We also have several projects related to dynamics issues for aeronautics. Some of this is housed in the structural dynamics research group, as described below.

 

Research in Aerospace and Dynamics

In the Wisconsin Shock Tube Laboratory, Professor Bonazza and his group investigate the flow induced by the interaction of a shock wave with the interface between gases of different densities, involving shock refraction, mixing and turbulence.

This kind of flow occurs in inertial confinement fusion experiments (the implosion of a spherical shell containing fusion fuels) and supersonic combustion systems (where the shock-induced mixing is postulated to promote the occurrence of chemical reactions over very short times).

Professor Jen Franck uses computational tools to investigate the dynamics and physics of unsteady, turbulent flows. Her lab utilizes a range of computational techniques, including Direct Numerical Simulation (DNS), Large-eddy simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) solvers. These solvers are applied to fundamental problems in fluid mechanics and in applications areas such as aerodynamic flow control, wind/tidal energy, propulsion or flapping flight.

Professor Choy’s research group develops quantum instruments based on atoms and atom-like systems for precise inertial sensing and timekeeping. Research interests in this area include advanced accelerometers and gyroscopes with improved positioning accuracy, precise and stable time and frequency standards, and the application of quantum sensors to navigate using maps of local gravity and magnetic variations.

Professor Thevamaran’s lab studies elastodynamics of non-Hermitian and parity-time symmetric metamaterials that incorporate various ‘engineered losses’, ‘lossy nonlinearities’, and ‘gain’ as useful ingredients to control and direct the mechanical energy transport. These systems exploit the proximity to an exceptional point singularity—a branch point singularity where the eigenvalues and the corresponding eigenvectors of a system coalesce—to create extreme wave-matter interactions. This unique approach to controlling mechanical waves through non-Hermitian material design is emerging as a paradigm shift in metamaterials research and development. Acoustic regulators, vibration absorbers and limiters, and vibration energy harvesters are a few of the many potential devices that can be created with non-Hermitian metamaterials.

Fusion Science and Technology

Fusion reactions combine light ions to produce heavier nuclei, along with energy associated with mass conversion. This energy can be converted to electricity, or the energetic particles can be used for non-electric applications. Faculty and staff in this area are exploring a variety of technologies for the production of fusion energy. The state of matter of the fusion medium is called a plasma – a highly charged gas that can be confined in strong magnetic fields. Therefore, Plasma Physics is the fundamental physics discipline for Fusion Energy Science, but it also can be used for a variety of other science and industry applications.

Research in Fusion Science and Technology

To reach fusion conditions, the high-temperature plasma is confined within a vacuum chamber by strong magnetic fields. Exploring the optimization of various configurations to accomplish this magnetic confinement is a key aspect of Fusion Energy-related research. The department houses a unique magnetic confinement fusion experiment, the Pegasus spherical tokamak under the supervision of Emeritus Professor Fonck. This device is being upgraded to become a center for studies of non-inductive current drive in tokamaks on the national scale. Assistant Professor Diem is responsible with her research team to apply radio-frequency waves to heat this unique tokamak plasma.

There are two other major magnetic fusion experiments on the UW-Madison campus. They are HSX, a stellarator, in the Department of Electrical and Computer Engineering and MST, a reversed-field pinch device, in the Department of Physics. A strong collaborative research environment is formed at all of these facilities being utilized for research by faculty, staff, and students from multiple departments across campus.

As fusion science progresses, large-scale facilities are being utilized to address the high-performance regime. Engineering Physics faculty in fusion energy science are participating in several large scale facilities around the world, among them the ITER tokamak, Cadarache, France well as the two U.S. national user facilities DIII-D and NSTX-U. The research group led by senior scientist McKee studies turbulent fluctuations in DIII-D and NSTX-U based on beam emission spectroscopy (BES). The collaborative research at the Wendelstein 7-X stellarator in Greifswald, Germany is coupled to an on-campus stellarator program by means of the HILOADS international laboratory of the German Helmholtz Association. Assistant Professor Geigers group studies the ion-heat and impurity transport in the core of W7-X, together with comparisons between HSX and W7-X plasmas.. Prof. Schmitz‘s group investigates the plasma edge and plasma material interaction in stellarator geometries with a focus on W7-X.

To realize sustained confinement, materials have to be developed that withstand the conditions in this harsh environment. The MARIA linear helicon plasma is used to study plasma material interactions and fundamental atomic processes in the plasma surface interaction domain. This experiment is supervised by Professor Schmitz.

The Department of Engineering Physics has a robust theory and computation effort spearheaded by Professors Hegna and Sovinec, who use analytic and computational techniques to study the dynamics of high-temperature plasma.

Prof. Hegna is the Director of the Center for Plasma Theory and Computation (CPTC) that fosters collaboration among campus plasma theory efforts. His current research interests include: the macrostability of tokamak and stellarator plasmas, optimization of stellarator confinement, turbulent transport and pedestal stability in three-dimensional configurations, plasma edge and divertor modeling physics. Prof. Sovinec applies nonlinear numerical computation to problems of macroscopic stability and magnetic relaxation in tokamaks and other configurations. He leads the international NIMROD code development team. His current research interests include: numerical methods for extended MHD modeling, the macrostability of tokamaks and stellarators, and tokamak disruption dynamics.

Plasma-material interaction in fusion experiments is a non-linear, multi-scale, multi-state and multi-species plasma physics and atomistic challenge. Prof. Schmitz’s group addresses these challenges by applying large computationally parallel codes for plasma edge physics (EMC3-EIRENE) and the plasma material interaction (ERO2).

Fusion technology addresses the engineering issues that must be addressed to build a reactor capable of producing electricity from fusion. Professors Lindley, Henderson, and Wilson have active research programs to address such issues as heat removal, radiation damage to materials, tritium production, magnet design, neutron and gamma transport, and component lifetime for nowadays experiments and future fusion reactors.

The plasma medium that is intensively studied for fusion application offers a broad range of applications from processing plasmas, to plasma coating and plasma propulsion. One direction that is actively pursued in the Department of Engineering Physics is the development of a plasma source for plasma-based wake field accelerator. Professor Schmitz is a full member of the AWAKE project at CERN and his group operates the Long Wake Field Accelerator Plasma prototype (LWAP-proto) cell.

Mechanics of Materials

The Mechanics of Materials group at UW-Madison combines the study of mechanics (the study of forces, stresses, deformation and motion as applied to engineering structures) and materials science (the study of material development, fabrication, chemical composition, microstructure and properties) to study a wide variety of engineering problems. We merge these disciplines to dramatically enhance our capability both to understand and characterize existing materials and to invent exceptional new materials. The Mechanics of Materials group comprises seven faculty members in the Department of Materials Science and Engineering and the Department of Engineering Physics. They have active programs in the following areas:

Research in Mechanics of Materials

Professor Thevamaran’s laboratory focuses on advancing the fundamental knowledge of process-structure-property-function relations in structured materials and creating innovative structured materials with extreme mechanical properties. He studies a variety of advanced materials from hierarchical carbon nanotube foams and gradient-nano-grained metals to non-Hermitian metamaterials.

In Professor Lakes‘ laboratory, he and his students synthesize and characterize novel materials for engineering applications. Materials that undergo phase transformation are of interest in the context of viscoelastic damping and of negative stiffness. They have developed new materials with reversed properties, including negative Poisson’s ratio, negative stiffness, and negative thermal expansion. Designed materials can have thermal expansion or piezoelectric sensitivity of arbitrarily large magnitude. Professor Lakes and his students have demonstrated, in the lab, composite materials stiffer than diamond over a temperature range.

 

Professor Crone studies biomechanics at the cellular and multicellular scales. Her lab has developed a platform that allows the production of a range of micropatterns on substrates of varying stiffness to study cardiomyocytes (CMs) and skeletal muscle cells differentiated from stem cells. In contrast to standard two-dimensional cultures systems where cells form cell-cell junctions in all directions, they have shown that immature CM cells patterned in interconnected lanes repeatability form extremely polarized structures which produce synchronous contraction, increased nuclear alignment, and highly enhanced sarcomere organization. In recent research exploring the co-culture of CMs with cardiac fibroblasts, they have shown aligned extracellular matrix remodeling and enhanced cardiomyocyte functionality. This platform is highly adaptable and is relevant to fundamental cardiomyocyte research, drug discovery, and toxicity testing.

Professor Notbohm studies mechanics of fibrous materials, cell-matrix interactions, and collective cell migration. The research focuses on mechanics, in particular, relating force to deformation or motion. Applications of the research are in human health, including wound healing, tissue engineering, and progression of fibrotic diseases, most notably cancer. There are also traditional engineering applications of this research, as fibrous materials are lightweight and thought to have desirable properties such as resistance to fracture.

Nuclear Systems Engineering

The United States has about 100 commercial fission reactors producing approximately 19% of our electricity and over 50% of our low-emission electricity. Our nuclear systems engineering research programs are largely devoted to advancing the state of the art in technologies used to produce electricity from fission. Some of our key programs are described below.

Research in Nuclear Systems Engineering

If we are to have a viable commercial nuclear energy fleet and strive to continue to improve upon efficiency, safety, economics, and performance of nuclear reactors we must be able to understand the behavior of a reactor under all operating conditions. Professors Corradini and Anderson have extensive experience modeling reactors and reactor components from a fluids heat transfer and thermodynamics perspective as well as conducting experiments that validate the models.

As simulation takes a larger role in the development of nuclear technology, there is a need to improve the fidelity and complexity of the simulations. With a focus on radiation transport and nuclide inventory tracking — and coupling these to other domain physics — Professors Wilson, Henderson, and Lindley are delivering new simulation capability by combining modern computational science technology with new solution methodologies. These tools are being used to design complex systems like ITER, to improve radiation treatment planning, to understand and improve next-generation reactor designs, and to explore the science-policy boundary of advanced fuel cycles.

Nuclear power has traditionally functioned best as a large baseload generator. However, as the share of variable renewables in the energy mix increases, and deep reductions in carbon emissions are targeted, nuclear energy must play an increasingly flexible role. Professors Lindley, Wilson, and Corradini perform research on the integration of nuclear and renewable energy, the use of nuclear energy to generate heat as well as electricity, and the deployment of novel reactors in new markets. This includes development of computational tools that are used to inform what is feasible and cost-effective; and development of new system concepts that open up new markets for nuclear energy and synergize with renewables.

The neutrons and charged particles inevitably present in nuclear facilities can do significant damage to structural materials. Atoms are displaced, properties are modified, and structures are deformed. We must understand these phenomena in order to produce viable reactor designs and understand component lifetime issues. Professors Sridharan, Couet, Zhang, Szlufarska, and Morgan have state of the art experimental and computational research programs to study the physics of these radiation damage events and the subsequent effect on reactor design, with the objective to design fuels and structural materials that can (i) improve the economics and safety of current nuclear reactors and (ii) withstand the irradiation damage in advanced nuclear reactors.

Materials used in nuclear reactors are subject to intense neutron irradiation, which damage materials and degrade their mechanical integrity and functional properties, affecting reactor safety and economics. Understanding irradiation effects in nuclear fuels and materials is critical for mitigating materials degradation in current nuclear reactors and for developing novel fuels and materials in advanced reactors. Synergistic modeling and experimental studies are carried out in Professors Couet, Sridharan, and Zhang’s groups to investigate how irradiation by high-energy particles changes material microstructure and properties. On the modeling side, Professor Zhang’s group focuses on atomistically informed mesoscale modeling of irradiation-induced damage evolution, defect self-organization, element segregation, and precipitation. The modeling studies are strongly coupled with experimental studies led by Professors Couet and Sridharan. Using ion beam irradiation at the Wisconsin Ion Beam Laboratory, a Nuclear Science User Facility, Couet and Sridharan study the irradiation effects in materials using high-energy light and heavy ions, which are used to mimic neutron irradiation effects. The coupled modeling and experimental capabilities provide a powerful toolkit for understanding irradiation effects, for the purpose of guiding materials design for use in advanced nuclear reactors.

As we look to the future, reactors will tend to operate at higher temperatures in order to increase the efficiency of the energy conversion processes or to produce process heat for industrial applications such as hydrogen production. This leads us to the use of new coolants, such as molten salts, liquid metals and high-temperature gas, and new materials and the need for ensuring that these combinations are compatible. Professors Sridharan, Anderson, and Couet all operate a variety of experiments that test the compatibility of coolants such as high temperature pressurized water, molten salt (fluorides and chlorides), lead, and liquid metals (sodium and lead) with innovative, high-temperature structural materials. The experimental studies are complemented by mesoscale modeling of corrosion in Professor Zhang’s group.

Many advanced nuclear fuel cycles rely on technologies that could be diverted for non-peaceful applications.  Designing safeguards for declared facilities and detection mechanisms for undeclared facilities can help support an international nuclear non-proliferation regime that has been largely successful at stemming the expansion of nuclear weapons. Professor Wilson uses a combination of modeling, simulation, and data science to better understand the opportunities to secure advanced nuclear fuel cycle facilities of the future.

Advanced Detection and Measurement

The ability to precisely determine physical quantities is a critical functionality in many research areas in science and engineering. At the Department of Engineering Physics, advanced measurement tools are developed and applied to study plasma behaviors, properties of nuclear and structured materials, shock wave dynamics, and biological systems. Meanwhile, quantum physics and phenomena are used in the development of precision sensors that detect magnetic fields and inertial forces with unparalleled precision and accuracy, as well as sensitively measure changes in electromagnetic fields and temperature with nanometer-scale resolution.

Advanced Detection and Measurement

The underlying basis in quantum sensing is the discrete nature of electron energies in atoms, ions, or atom-like systems in solids. Each allowed electron energy state, and transition between energy states, corresponds to a characteristic frequency. Measurement of this frequency can allow us to tell time (in the case of atomic clocks) and infer small physical changes in the environment (such as electromagnetic fields, inertial forces, pressure/strain, temperature). Professor Choy’s research group is characterizing and developing quantum sensing platforms based on neutral atoms and optically-active spin defects in diamond.

Professor Choy’s group is also interested in applying nanoscale optics to improve photon detection and miniaturize optical systems in classical and quantum sensors. Moreover, since preparation and measurement of quantum systems rely on their interactions with photons, robust approaches to control photon properties are critical to the utility and performance of quantum devices.

Research centers, consortia, and laboratories