9 Feb 2022

Implementation of Flexible Vegetation into CSHORE for Modeling Wave Attenuation

Abstract: This technical report presents the new numerical modeling capabilities for simulating wave attenuation and mean water level changes through flexible vegetation such as smooth cordgrass in coastal and marine wetlands. These capabilities were implemented into the Cross-SHORE (CSHORE) numerical model. The biomechanical properties of vegetation such as dimensions, flexibility, and bending strength are parameterized in terms of the scaling law. Correspondingly, a new formulation of the vegetation drag coefficient, CD, is developed using field data from a salt marsh in Terrebonne Bay, LA, by considering spatially varying effective stem and blade heights of species. This report also presents a general procedure for using the model to simulate hydrodynamic variables (i.e., waves, currents, mean water levels) at vegetated coasts, which are used to quantify the effects of wave attenuation and reduction of surge and runup due to vegetation. Preliminary model validation was conducted by simulating a set of laboratory experiments on synthetic vegetation, which mimicked the flexibility of Spartina alterniflora. The validation results indicate that the newly developed vegetation capabilities enable CSHORE to predict changes of wave heights and water levels through marshes by considering species-specific biomechanical features. The model is also applicable to assess vegetation effectiveness against waves and surges.

7 Feb 2022

Antecedent Precipitation Tool (APT) Version 1.0: Technical and User Guide

Abstract: This document provides an overview of the technical components of the Antecedent Precipitation Tool (APT) and a user guide for using the APT. The APT is an automation tool that the US Army Corps of Engineers (USACE) developed to facilitate the comparison of antecedent or recent precipitation conditions for a given location to the range of normal precipitation conditions that occurred during the preceding 30 yr¹. In addition to providing a standardized methodology to evaluate normal precipitation conditions (“precipitation normalcy”), the APT can assess the presence of drought conditions and the approximate dates of the wet and dry seasons for a given location.

7 Feb 2022

Dynamics Modeling and Robotic-Assist, Leader-Follower Control of Tractor Convoys

Abstract: This paper proposes a generalized dynamics model and a leader-follower control architecture for skid-steered tracked vehicles towing polar sleds. The model couples existing formulations in the literature for the powertrain components with the vehicle-terrain interaction to capture the salient features of terrain trafficability and predict the vehicles response. This coupling is essential for making realistic predictions of the vehicles traversing capabilities due to the power-load relationship at the engine output. The objective of the model is to capture adequate fidelity of the powertrain and off-road vehicle dynamics while minimizing the computational cost for model based design of leader-follower control algorithms. The leader-follower control architecture presented proposes maintaining a flexible formation by using a look-ahead technique along with a way point following strategy. Results simulate one leader-follower tractor pair where the leader is forced to take an abrupt turn and experiences large oscillations of its drawbar arm indicating potential payload instability. However, the follower tractor maintains the flexible formation but keeps its payload stable. This highlights the robustness of the proposed approach where the follower vehicle can reject errors in human leader driving.

3 Feb 2022

Observation of Crack Arrest in Ice by High Aspect Ratio Particles during Uniaxial Compression

Abstract: In nature, ice frequently contains dissolved solutes or entrapped particles, which modify the microstructure and mechanical properties of ice. Seeking to understand the effect of particle shape and geometry on the mechanical properties of ice, we performed experiments on ice containing 15 wt% silica spheres or rods. Unique to this work was the use of 3-D microstructural imaging in a -10ºC cold room during compressive loading of the sample. The silica particles were present in the ice microstructure as randomly dispersed aggregates within grains and at grain boundaries. While cracks originated in particle-free regions in both sphere- and rod-containing samples, the propagation of cracks was quite different in each type of sample. Cracks propagated uninhibited through aggregates of spherical particles but were observed to arrest at and propagate around aggregates of rods. These results imply that spherical particles do not inhibit grain boundary sliding or increase viscous drag. On the other hand, silica rods were found to span grains, thereby pinning together the microstructure of ice during loading. These results provide insights into mechanisms that can be leveraged to strengthen ice.

1 Feb 2022

Deconstruction Feasibility Assessment of Warehouse District Facilities at Fort Leonard Wood, Missouri

Abstract: The U.S. Army Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) and Fort Leonard Wood, MO, are in the sixth year of efforts to plan and implement a program in support of installation sustainability. As part of this effort, ERDC-CERL personnel supported the Fort Leonard Wood Directorate of Public Works (DPW) by conducting a deconstruction assessment of multiple buildings in the warehouse district. The project delivery team visited Fort Leonard Wood in April 2017 to conduct quantity take-offs of the buildings. An abbreviated interim report that focused exclusively on Bldgs. 2338 and 2339 was pro-vided to the Chief, Master Planning Branch, at that time. These two buildings were representative of the majority of the buildings in the assessment and thus became the model that we describe in detail in the sections below. Differences between the other warehouses and the model are discussed. Several buildings that had configurations different from that of the model were evaluated independently.

27 Jan 2022

Energy Atlas—Mapping Energy-Related Data for DoD Lands in Alaska: Phase 2—Data Expansion and Portal Development

ABSTRACT: As the largest Department of Defense (DoD) land user in Alaska, the U.S. Army oversees over 600,000 hectares of land, including remote areas accessible only by air, water, and winter ice roads. Spatial information related to the energy resources and infrastructure that exist on and adjacent to DoD installations can help inform decision makers when it comes to installation planning. The Energy Atlas−Alaska portal provides a secure value-added resource to support the decision-making process for energy management, investments in installation infrastructure, and improvements to energy resiliency and sustainability. The Energy Atlas–Alaska portal compiles spatial information and provides that information through a secure online portal to access and examine energy and related resource data such as energy resource potential, energy corridors, and environmental information. The information database is hosted on a secure Common Access Card–authenticated portal that is accessible to the DoD and its partners through the Army Geospatial Center’s Enterprise Portal. This Enterprise Portal provides effective visualization and functionality to support analysis and inform DoD decision makers. The Energy Atlas–Alaska portal helps the DoD account for energy in contingency planning, acquisition, and life-cycle requirements and ensures facilities can maintain operations in the face of disruption.

26 Jan 2022

In Situ Visualization with Temporal Caching

Abstract: In situ visualization is a technique in which plots and other visual analyses are performed in tandem with numerical simulation processes in order to better utilize HPC machine resources. Especially with unattended exploratory engineering simulation analyses, events may occur during the run, which justify supplemental processing. Sometimes though, when the events do occur, the phenomena of interest includes the physics that precipitated the events and this may be the key insight into understanding the phenomena that is being simulated. In situ temporal caching is the temporary storing of produced data in memory for possible later analysis including time varying visualization. The later analysis and visualization still occurs during the simulation run but not until after the significant events have been detected. In this article, we demonstrate how temporal caching can be used with in-line in situ visualization to reduce simulation run-time while still capturing essential simulation results.

25 Jan 2022

Freight Fluidity for the Port of Baltimore: Vessel Approach and Maritime Mobility Metrics

Abstract: The United States Army Corps of Engineers is tasked with maintaining waterborne transportation system elements. Understanding channel utilization by vessels informs decisions regarding operations, maintenance, and investments in those elements. Historically, investment decisions have been informed by safety, environmental considerations, and projected economic benefits of alleviating channel restrictions or shipping delays (usually derived from models). However, quantifying causes and impacts of shipping delays based on actual historical vessel location data and then identifying which causes could be ameliorated through investment has been out of reach until recently. In this study, Automatic Identification System vessel position reports were used to develop quantitative measures of transit and dwell-time reliabilities for commercial vessels calling at the Port of Baltimore, Maryland. This port has two deep-water approaches: Chesapeake Bay and the Chesapeake and Delaware Canal. Descriptive metrics were determined for each approach, including port cycle time, harbor stay hours, travel time inbound, and travel time outbound. Then, additional performance measures were calculated: baseline travel time, travel time index, and planning time index. The key finding of this study is that the majority of variability in port cycle time is due to the variability in harbor stay hours, not from channel conditions or channel restrictions.

24 Jan 2022

AIS Data Case Study: Evaluating Reception of AIS Position Reports on the Missouri River by LOMA AIS Sites in April and August 2020

Abstract: This Coastal and Hydraulics Engineering Technical Note (CHETN) describes a method for evaluating the received coverage from Automatic Identification System (AIS) shoreside sites along the Missouri River managed by the US Army Corps of Engineers (USACE) Lock Operations Management Application (LOMA), and presents the results of that analysis. The purpose is to identify AIS coverage gaps in the current system. Reception of AIS transmissions between shore-based transceivers and vessels is generally line-of-sight between the vessel and the AIS site antenna. However, signal reception may be affected by factors such as the distance and terrain between the vessel and the transceiver site, quality of the transceiver installation, state of the equipment either aboard the vessel or at the shore transceiver station, and atmospheric phenomena. Quantifying coverage gaps along the inland waterways system can inform research that uses AIS data, provide information on the performance of the AIS network, and provide guidance for efforts to address coverage gaps to improve navigation safety. In autumn 2020, severe shoaling was occurring on the Missouri River. As the shoals were identified, the Kansas City District requested the LOMA system transmit AIS Aid to Navigation (AtoN) to mark the shoals in several critical areas. However, vessel pilots sometimes reported that they were not receiving the AIS AtoN being transmitted. At the request of the Kansas City District, the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory (ERDC-CHL), conducted a coverage analysis using data collected from the LOMA AIS transceivers in the area to determine if there were coverage issues and their extent and to aid in determining the best means of addressing any coverage gaps.

21 Jan 2022

USACE Research and Development Strategy: Communication Products

Abstract: This paper provides the U.S. Army Corps of Engineers (USACE) communication products sent by LTG Scott A. Spellmon to help as we discuss the first USACE Research and Development Strategy. The USACE R&D Strategy was approved at the 1Q22 EGM in Atlanta, and is now ready for fielding, communicating, and implementing. The materials included here are (1) The USACE R&D Strategy, (2) USACE R&D Strategy Slide Deck, (3) USACE Top 10 R&D Priorities 2-pager; (4) USACE Top 10 R&D Priorities Placemat. The USACE R&D Strategy Slide Deck has several examples of R&D products and capabilities, aligned with the Top 10 R&D Priorities, for your use. Please add to these examples with your own, highlighting past R&D success stories as well as the need for future potential R&D.