25 Jun 2021

A Physics-Informed Neural Network for Sound Propagation in the Atmospheric Boundary Layer

Abstract: We describe what we believe is the first effort to develop a physics-informed neural network (PINN) to predict sound propagation through the atmospheric boundary layer. PINN is a recent innovation in the application of deep learning to simulate physics. The motivation is to combine the strengths of data-driven models and physics models, thereby producing a regularized surrogate model using less data than a purely data-driven model. In a PINN, the data-driven loss function is augmented with penalty terms for deviations from the underlying physics, e.g., a governing equation or a boundary condition. Training data are obtained from Crank-Nicholson solutions of the parabolic equation with homogeneous ground impedance and Monin-Obukhov similarity theory for the effective sound speed in the moving atmosphere. Training data are random samples from an ensemble of solutions for combinations of parameters governing the impedance and the effective sound speed. PINN output is processed to produce realizations of transmission loss that look much like the Crank-Nicholson solutions. We describe the framework for implementing PINN for outdoor sound, and we outline practical matters related to network architecture, the size of the training set, the physics-informed loss function, and challenge of managing the spatial complexity of the complex pressure.

24 Jun 2021

Helicopter Rotor Blade Multiple-Section Optimization with Performance Considerations

Abstract: This paper presents advancements in a surrogate-based, rotor blade design optimization framework for improved helicopter performance. The framework builds on previous successes by allowing multiple airfoil sections to designed simultaneously to minimize required rotor power in multiple flight conditions. Rotor power in hover and forward flight, at advance ratio 𝜇 = 0.3, are used as objective functions in a multi-objective genetic algorithm. The framework is constructed using Galaxy Simulation Builder with optimization provided through integration with Dakota. Three independent airfoil sections are morphed using ParFoil and aerodynamic coefficients for the updated airfoil shapes (i.e., lift, drag, moment) are calculated using linear interpolation from a database generated using C81Gen/ARC2D. Final rotor performance is then calculated using RCAS. Several demonstrative optimization case studies were conducted using the UH-60A main rotor. The degrees of freedom for this case are limited to the airfoil camber, camber crest position, thickness, and thickness crest position for each of the sections. The results of the three-segment case study show improvements in rotor power of 4.3% and 0.8% in forward flight and hover, respectively. This configuration also yields greater reductions in rotor power for high advance ratios, e.g., 6.0% reduction at 𝜇 = 0.35, and 8.8% reduction at 𝜇 = 0.4.

23 Jun 2021

Historic Landscape Management Plan for the Fort Huachuca Historic District National Historic Landmark and Supplemental Areas

Abstract: The U.S. Congress codified the National Historic Preservation Act of 1966 (NHPA) to provide guidelines and requirements for preserving tangible elements of our nation’s past. This preservation was done primarily through creation of the National Register of Historic Places (NRHP), which contains requirements for federal agencies to address, inventory, and evaluate their cultural resources, and to determine the effect of federal undertakings on properties deemed eligible or potentially eligible for the NRHP. This work inventoried and evaluated the historic landscapes within the National Landmark District at Fort Huachuca, Arizona. A historic landscape context was developed; an inventory of all landscapes and landscape features within the historic district was completed; and these landscapes and features were evaluated using methods established in the Guidelines for Identifying and Evaluating Historic Military Landscapes (ERDC-CERL 2008) and their significance and integrity were determined. Photographic and historic documentation was completed for significant landscapes. Lastly, general management recommendations were provided to help preserve and/or protect these resources in the future.

23 Jun 2021

Meteorological Property and Temporal Variable Effect on Spatial Semivariance of Infrared Thermography of Soil Surfaces for Detection of Foreign Objects

Abstract: The environmental phenomenological properties responsible for the thermal variability evident in the use of thermal infrared (IR) sensor systems is not well understood. The research objective of this work is to understand the environmental and climatological properties contributing to the temporal and spatial thermal variance of soils. We recorded thermal images of surface temperature of soil as well as several meteorological properties such as weather condition and solar irradiance of loamy soil located at the Cold Regions Research and Engineering Lab (CRREL) facility. We assessed sensor performance by analyzing how recorded meteorological properties affected the spatial structure by observing statistical differences in spatial autocorrelation and dependence parameter estimates.

17 Jun 2021

Application of Laser Induced Breakdown Spectroscopy (LIBS) for Environmental, Chemical, and Biological Sensing

Abstract: The Army is interested in sensors capable of characterizing/monitoring the environment (battlefield or military training ranges) at proximal distances. Recently, we evaluated laser induced breakdown spectroscopy (LIBS) systems (hand-held, proximal, and bench top) for the characterization of metals (antimony, copper, lead, tungsten, and zinc) in soils obtained from military training ranges. We then compared the results to findings obtained with standard field and laboratory instrumentation for metals analysis - X-ray Fluorescence (XRF) and Inductively Couple P28lasma- Optical Emission Spectroscopy (ICP-OES).

16 Jun 2021

Field Measurement and Monitoring of Hydrodynamic and Suspended Sediment within the Seven Mile Island Innovation Laboratory, New Jersey

Abstract: The Seven Mile Island Innovation Laboratory (SMIIL) was launched in 2019 to evaluate beneficial use of dredge material management practices in coastal New Jersey. As part of that effort, the Philadelphia District requested that the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, collect data to characterize the hydrodynamics and turbidity within the central portions of the SMIIL prior to and during dredge material placement. Pre-dredge monitoring found that apart from punctuated wind events, the study area waters were generally calm and clear with small waves, <0.25 m, slow current speeds (~0.1 m/s), low turbidity (~10 ntus), and low suspended sediment concentrations (~10–20 mg/L). In March 2020, 2,475 m3 of dredged sediment was placed on the northern portion of Sturgeon Island within the SMIIL. Turbidity in the waters surrounding the island was monitored to quantify extent of the sediment plume resulting from the placement. Observations found little to no turbidity plume associated with the dredging operations beyond 20 m from the island and that the plume was largely limited to areas near a tidal creek draining the placement area. Additionally, turbidity levels quickly returned to background conditions at times when the dredge was not in operation.

15 Jun 2021

Red River Structure Physical Model Study: Bulkhead Testing

Abstract: The US Army Corps of Engineers, St. Paul District, and its non-federal sponsors are designing and constructing a flood risk management project that will reduce the risk of flooding in the Fargo-Moorhead metropolitan area. There is a 30-mile long diversion channel around the west side of the city of Fargo, as well as a staging area that will be formed upstream of a 20-mile long dam (referred to as the Southern Embankment) that collectively includes an earthen embankment with three gated structures: the Diversion Inlet Structure, the Wild Rice River Structure, and the Red River Structure (RRS). A physical model has been constructed and analyzed to assess the hydraulic conditions near and at the RRS for verification of the structure’s flow capacity as well as optimization of design features for the structure. This report describes the modeling techniques and instrumentation used in the investigation and details the evaluation of the forces exerted on the proposed bulkheads during emergency operations for the RRS.

15 Jun 2021

Alternatives for Large Crater Repairs using Rapid Set Concrete Mix®

Abstract: Research was conducted at the U.S. Army Engineer Research and Development Center (ERDC) in Vicksburg, MS, to identify alternative repair methods and materials for large crater repairs using Rapid Set Concrete Mix®. This report presents the technical evaluation of the field performance of full-depth slab replacement methods conducted using Rapid Set Concrete Mix® over varying strength foundations. The performance of each large crater repair was determined by using a load cart representing one-half of the full gear of a C-17 aircraft. Results indicate that using rapid-setting concrete is a viable material for large crater repairs, and the performance is dependent on surface thickness and base strength.

15 Jun 2021

A Novel Laboratory Method for the Detection and Identification of Cyanobacteria Using Hyperspectral Imaging: Hyperspectral Imaging for Cyanobacteria Detection

Abstract: To assist US Army Corps of Engineers resource managers in monitoring for cyanobacteria bloom events, a laboratory method using hyperspectral imaging has been developed. This method enables the rapid detection of cyanobacteria in large volumes and has the potential to be transitioned to aerial platforms for field deployment. Prior to field data collection, validation of the technology in the laboratory using monocultures was needed. This report describes the development of the detection method using hyperspectral imaging and the stability/reliability of these signatures for identification purposes. Hyperspectral signatures of different cyanobacteria were compared to evaluate spectral deviations between genera to assess the feasibility of using this imaging method in the field. Algorithms were then developed to spectrally deconvolute mixtures of cyanobacteria to determine relative abundances of each species. Last, laboratory cultures of Microcystis aeruginosa and Anabaena sp. were subjected to varying macro (nitrate and phosphate) and micro-nutrient (iron and magnesium) stressors to establish the stability of signatures within each species. Based on the findings, hyperspectral imaging can be a valuable tool for the detection and monitoring of cyanobacteria. However, it should be used with caution and only during stages of active growth for accurate identification and limited interference owing to stress.

14 Jun 2021

AIS data case Study: identifying AIS coverage gaps on the Ohio River in CY2018

Abstract: This Coastal and Hydraulics Engineering Technical Note describes a method for evaluating the received coverage from Automatic Identification System shore sites and the availability of historic vessel position reports along the Ohio River. The network of AIS shoreside sites installed and operated by the US Army Corps of Engineers and the US Coast Guard receive information transmitted from vessels; however, reception of these transmissions is generally line-of-sight between the vessel and the AIS site antenna. Reception may also be affected by factors such as the quality of the transceiver installation aboard the vessel as well as the state of the equipment at the receiving site. Understanding how to define and quantify coverage gaps along the inland river system can inform research utilizing AIS data, provide information on the performance of the AIS network, and provide guidance for efforts to address identified coverage gaps.