Validating Geoclaw for Simulating Teton Dam Failure by Comparison with HEC-RAS Results and Historical Observations

The combination of dams degrading with age and other factors like climate change, technical errors, and human errors lead to dams breaching and failing worldwide. In the United States, over 40,000 dams pose a threat to downstream inhabited areas and constitute a widespread hazard if they were to breach. Therefore, it is critical to accurately predict the resultant floods’ downstream flow behavior to create a more resilient community. By improving research, we can concurrently develop and improve mitigation strategies for downstream communities. This study benchmarks the GeoClaw numerical modeling software with the well-documented 1976 Teton Dam failure. A vital tool in dam failure research is two-dimensional (2D) coupled numerical hydrodynamic modeling for dam-breaks. This study aims to benchmark the GeoClaw software, a 2D hydraulic model with novel adaptive mesh refinement (AMR) capabilities (http://www.clawpack.org/) for dam failure analysis by a systematic comparison of dam breach inundation response to both historical data and the industry-standard software HEC-RAS (Hydraulic Engineering Center - River Analysis System). The objectives of this study are to: Determine the suitability of the GeoClaw software based on its capability to resolve inundation extent and flood front arrival times Compare an instantaneous dam breach with a time-dependent breach formation Quantify the uncertainty of the HEC-RAS model through a sensitivity analysis This study concludes the 2D GeoClaw dam break model verified by its stability and accuracy, conservation properties, and calibration with the historical hydrological data and HEC-RAS results at a low computational cost. The overall performance of GeoClaw indicates that it is a validated tool for the simulation of dam-break waves in real-cases with future work. The outcomes of this study will assist dam owners, floodplain managers, and emergency managers alike by providing an additional tool for estimating the impacts of dam failures

Long Range Forces from Two Neutrino Exchange Revisited

The exchange of two massless neutrinos gives rise to a long range force which couples to weakly charged matter. As has been noted previously in the literature, the potential for this force is \VN \propto G_{F}^2 / r^5 with monopole-monople, spin-spin and more complicated interactions. Unfortunately, this is far too small to be observed in present day experiments. We calculate \VN explicitly in the electroweak theory, and show that under very general assumptions forces arising from the exchange of two massless fermions can at best yield $1 / r^5$ potentials.Comment: 5 pages + 1 figure (not included), UFIFT-HEP-92-28/HUTP-92-A04

Symmetry, singularities and integrability in complex dynamics III: approximate symmetries and invariants

The different natures of approximate symmetries and their corresponding first integrals/invariants are delineated in the contexts of both Lie symmetries of ordinary differential equations and Noether symmetries of the Action Integral. Particular note is taken of the effect of taking higher orders of the perturbation parameter. Approximate symmetries of approximate first integrals/invariants and the problems of calculating them using the Lie method are considered

Drones, Virtual Reality, and Modeling: Communicating Catastrophic Dam Failure

Dam failures occur worldwide and can be economically and ecologically devastating. Communicating the scale of these risks to the general public and decision-makers is imperative. Two-dimensional (2D) dam failure hydraulic models inform owners and floodplain managers of flood regimes but have limitations when shared with non-specialists. This study addresses these limitations by constructing a 3D Virtual Reality (VR) environment to display the 1976 Teton Dam disaster case study using a pipeline composed of (1) 2D hydraulic model data (extrapolated into 3D), (2) a 3D reconstructed dam, and (3) a terrain model processed from UAS (Uncrewed Airborne System) imagery using Structure from Motion photogrammetry. This study validates the VR environment pipeline on the Oculus Quest 2 VR Headset with the criteria: immersion fidelity, movement, immersive soundscape, and agreement with historical observations and terrain. Through this VR environment, we develop an effective method to share historical events and, with future work, improve hazard awareness; applications of this method could improve citizen engagement with Early Warning Systems. This paper establishes a pipeline to produce a visualization tool for merging UAS imagery, Virtual Reality, digital scene creation, and sophisticated 2D hydraulic models to communicate catastrophic flooding events from natural or human-made levees or dams

Progress in Interferometry for LISA at JPL

Recent advances at JPL in experimentation and design for LISA interferometry include the demonstration of Time Delay Interferometry using electronically separated end stations, a new arm-locking design with improved gain and stability, and progress in flight readiness of digital and analog electronics for phase measurements.Comment: 11 pages, 9 figures, LISA 8 Symposium, Stanford University, 201

Modulator noise suppression in the LISA Time-Delay Interferometric combinations

We previously showed how the measurements of some eighteen time series of relative frequency or phase shifts could be combined (1) to cancel the phase noise of the lasers, (2) to cancel the Doppler fluctuations due to non-inertial motions of the six optical benches, and (3) to remove the phase noise of the onboard reference oscillators required to track the photodetector fringes, all the while preserving signals from passinggravitational waves. Here we analyze the effect of the additional noise due to the optical modulators used for removing the phase fluctuations of the onboard reference oscillators. We use a recently measured noise spectrum of an individual modulator to quantify the contribution of modulator noise to the first and second-generation Time-Delay Interferometric (TDI) combinations as a function of the modulation frequency. We show that modulator noise can be made smaller than the expected proof-mass acceleration and optical-path noises if the modulation frequencies are larger than $\approx 682$ MHz in the case of the unequal-arm Michelson TDI combination $X_1$, $\approx 1.08$ GHz for the Sagnac TDI combination $\alpha_1$, and $\approx 706$ MHz for the symmetrical Sagnac TDI combination $\zeta_1$. These modulation frequencies are substantially smaller than previously estimated and may lead to less stringent requirements on the LISA's oscillator noise calibration subsystem.Comment: 17 pages, 5 figures. Submitted to: Phys. Rev. D 1

Decadal-centennial scale monsoon variations in the Arabian Sea during the Early Holocene

An essential prerequisite for the prediction of future climate change due to anthropogenic input is an understanding of the natural processes that control Earth's climate on timescales comparable to human-lifespan. The Early Holocene period was chosen to study the natural climate variability in a warm interval when solar insolation was at its maximum. The monsoonal system of the Tropics is highly sensitive to seasonal variations in solar insolation, and consequently marine sediments from the region are a potential monitor of past climate change. Here we show that during the Early Holocene period rapid