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Robert Ellis

Publications and source records attributed to Robert Ellis.

3 recordsLinked to original sources

The FLARE Facility

The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly extend the accessible parameter space, targeting Lundquist numbers up to S ~ 10^5 and normalized system sizes up to \lambda ~ 10^3. This paper details the facility's core engineering components, including the primary vacuum vessel, internal flux cores, highly segmented external coil systems, modular capacitor banks, and the safety interlock and control architecture. An initial diagnostic suite is presented, comprising high-resolution 2D magnetic probe arrays, triple Langmuir probes, a fully fiber-coupled interferometer, ion Doppler spectroscopy, and fast camera imaging. Initial operations demonstrate the device's experimental flexibility and reliability, successfully executing symmetric push-pull reconnection, spheromak merging, and asymmetric downstream configurations. Currently operating within "Stage 2.5" with S ~ 2,500 and \lambda ~ 60 for anti-parallel reconnection, FLARE provides immediate access to the multiple X-line regimes. Planned hardware upgrades, advanced diagnostic additions, and integration with fully kinetic simulations will further expand its capabilities as it transitions into a collaborative user facility for the broader plasma science community.

physics.plasm-ph

Optimal Load Shedding for Public Safety Power Shutoffs

Public utilities are faced with situations where high winds can bring trees and debris into contact with energized power lines and other equipments, which could ignite wildfires. As a result, they need to turn off power during severe weather to help prevent wildfires. This is called Public Safety Power Shutoff (PSPS). We present a method for load reduction using a multi-step genetic algorithm for Public Safety Power Shutoff events. The proposed method optimizes load shedding using partial load shedding based on load importance (critical loads like hospitals, fire stations, etc). The multi-step genetic algorithm optimizes load shedding while minimizing the impact on important loads and preserving grid stability. The effectiveness of the method is demonstrated through network examples. The results show that the proposed method achieves minimal load shedding while maintaining the critical loads at acceptable levels. This approach will help utilities to effectively manage PSPS events and reduce the risk of wildfires caused by the power lines.

eess.SY

Comparison of numerical software for predicting the performance of a horizontal axis tidal turbine

For tidal energy to become an alternative energy resource to fossil fuels then there needs to be confidence in the predicted performance of horizontal axis tidal turbine devices. A number of computational fluids dynamics packages are now available to assist in the design and testing of new devices. The work in this paper describes a comparative study as a scoping exercise between two widely used packages, OpenFOAM and ANSYS CFX. The numerical simulations were run using the same geometry, mesh and turbulence model on both software. The results were compared to experimental testing conducted at INSEAN. The setup for each model is detailed. Differences were noted in the running and setup of the models as well as within the time history of the results. Overall both CFX and OpenFOAM were shown to give good predictions for the performance coefficients compared to the experimental testing with the data averaged over several complete rotations and well when compared to each other.

physics.flu-dyn