Computational Fluid Dynamics Methods Used in the Development of the Space Launch System Liftoff and Transition Lineloads Databases

The objective of this paper is to document the reasoning and trade studies that supported the selection of appropriate tools for constructing aerodynamic lineload databases for the Liftoff and Transition phases of flight for launch vehicles. These decisions were made amid the maturation of an evolving workflow for generating databases on variants of the Space Launch System launch vehicle, with most being based on results from brief developmental studies performed in response to specific, unforeseen challenges that were encountered in analyzing a given configuration. This report is intended to provide a summary of the results and the decision-making processes chronologically over the design cycles of various configurations, starting with isolated free-air bodies for the Block 1 Crew, then the Block 1B Crew and Cargo configurations, and most recently the Block 1B Crew configuration in proximity to the launch tower. The results from these analyses led to the selection of the CREATE-AV Kestrel flowsolver for simulating these problems. The need to accurately capture the expected leeward-wake flow field characteristics required the use of Delayed Detached Eddy Simulation (DDES) method, for which the vorticity magnitude was employed as the solution Adaptive Mesh Refinement (AMR) function over the off-body Cartesian grid region. In addition, the Spalart-Allmaras (SA) model is used to account for the flow turbulence effects

Wind loads for petrochemical structures

Techniques currently available to practicing engineers for estimating wind loads for petrochemical structures have little theoretical or experimental basis. This dissertation research is an effort to expand the understanding of wind effects on petrochemical and other, similar structures. Petrochemical structures introduce geometric scales into wind tunnel model simulations below what are common for enclosed structures. Wind tunnel experiments were performed to help determine whether this will introduce problems in achieving dynamic similarity between models and prototypes. The experiments did not reveal any clear indication that petrochemical structures cannot be modeled in wind tunnels at scales similar to those used for enclosed buildings. Aerodynamic coefficients were measured for models of open frame structures, partially clad structures, and vertical vessels in the LSU Wind Tunnel Laboratory. When possible, the values were compared with the literature or current analysis techniques. For open frames, diagonal braces and solid flooring had significant effects on the wind loads which are not reflected in current analysis methods. Shielding of equipment located within open frames was found to be underestimated by current analysis methods. Wind loads for partially clad structures exceeded those of enclosed structures with similar overall geometry for some cladding configurations. Wind loads for vertical vessels in paired arrangements were found to deviate significantly from wind load estimates for single vessels - a fact that is not represented adequately in current analysis techniques. When appropriate, recommendations were made to address the shortcomings in wind load analysis for these structures. An analytical model was developed to describe the variation of the wind force coefficient for higher-solidity open frame structures with respect to solidity ratio and plan aspect ratio. The model reproduced trends in experimental data from previous researchers and provided insight into the development of upper-bound wind loads for open frame structures. Experimental data was used to estimate the bias and variance of analytical estimates of wind force coefficients for petrochemical structures. Applying recommendations from this research reduced the variance in these estimates. The structural reliability of a petrochemical structure designed for wind loads according to current industry guidelines is only slightly lower than an enclosed structure

Wide-Field InfraRed Survey Telescope (WFIRST) Final Report

In December 2010, NASA created a Science Definition Team (SDT) for WFIRST, the Wide Field Infra-Red Survey Telescope, recommended by the Astro 2010 Decadal Survey as the highest priority for a large space mission. The SDT was chartered to work with the WFIRST Project Office at GSFC and the Program Office at JPL to produce a Design Reference Mission (DRM) for WFIRST. Part of the original charge was to produce an interim design reference mission by mid-2011. That document was delivered to NASA and widely circulated within the astronomical community. In late 2011 the Astrophysics Division augmented its original charge, asking for two design reference missions. The first of these, DRM1, was to be a finalized version of the interim DRM, reducing overall mission costs where possible. The second of these, DRM2, was to identify and eliminate capabilities that overlapped with those of NASA's James Webb Space Telescope (henceforth JWST), ESA's Euclid mission, and the NSF's ground-based Large Synoptic Survey Telescope (henceforth LSST), and again to reduce overall mission cost, while staying faithful to NWNH. This report presents both DRM1 and DRM2.Comment: 102 pages, 57 figures, 17 table

HUMAN INTERACTIONS IN PHYSICAL AND VIRTUAL SPACES: A GIS-BASED TIME-GEOGRAPHIC EXPLORATORY APPROACH

Information and communication technologies (ICT) such as cell phone and the Internet have extended opportunities of human activities and interactions from physical spaces to virtual spaces. The relaxed spatio-temporal constraints on individual activities may affect human activity-travel patterns, social networks, and many other aspects of society. A challenge for research of human activities in the ICT age is to develop analytical environments that can help visualize and explore individual activities in virtual spaces and their mutual impacts with physical activities. This dissertation focuses on extending the time-geographic framework and developing a spatio-temporal exploratory environment in a space-time geographic information system (GIS) to facilitate research of human interactions in both physical and virtual spaces. In particular, this dissertation study addresses three research questions. First, it extends the time-geographic framework to assess the impacts of phone usage on potential face-to-face (F2F) meeting opportunities, as well as dynamic changes in potential F2F meeting opportunities over time. Secondly, this study extends the time-geographic framework to conceptualize and represent individual trajectories in an online social network space and to explore potential interaction opportunities among people in a virtual space. Thirdly, this study presents a spatio-temporal environment in a space-time GIS to facilitate exploration of the relationships between changes in physical proximity and changes in social closeness in a virtual space. The major contributions of this dissertation include: (1) advancing the time-geographic framework in its ability of exploring processes of virtual communication alerting physical activity opportunities; (2) extending some concepts of the classical time geography from a physical space to a virtual space for representing and exploring virtual interaction patterns; (3) developing a space-time GIS that is useful for exploring patterns of individual activities and interactions in both physical and virtual spaces, as well as the interactions between these two spaces

Development of an experiment for visible radiation measurements from a satellite

The inversion problem, I.E., determining the atmospheric turbidity from polarimetry of radiation emerging from the earth's atmosphere, is presented. A major theoretical advance was made by finding a successful approximation for the forward peak scattering of aerosols together with a simplified characterization of particle size distributions. An engineering model of a multibarreled photopolarimeter suitable for operation from a satellite was evaluated in laboratory and high altitude jet aircraft tests. Comparison of the data from flights over the Mexican desert with theoretical curves for a Rayleigh atmosphere with negligible turbidity is in agreement

Assessment of the Structural and Thermal Behavior of Concrete Masonry Construction via Experimentally Informed Numerical Models

This dissertation aims at describing and examining the compressive and out-of-plane behavior and failure patterns of mortarless masonry prisms and walls through experimental tests and numerical models. In addition, the thermal performance of various masonry units is investigated through detailed thermo-fluid dynamic models to contribute to the masonry construction knowledge base. Studies on the behavior of masonry systems are fundamental to understanding their structural and thermal performance. One of the variations of this type of construction is dry-stack masonry, i.e., units laid without mortar between the joints. Despite reducing the time and cost of construction, mortarless construction has not gained widespread acceptance as a viable alternative to mortared masonry because the mechanical behavior of the mortarless system is not yet fully understood. To address this knowledge gap, this research developed numerical models to compare their response under compressive and out-of-plane loads with experimental tests. The validated structural numerical models of mortarless masonry prisms and reinforced mortarless walls are then used to predict and thoroughly examine the effects of design parameters. The mortarless prisms in these models included variations in the surface roughness between the units. These models revealed that both the stress distribution and failure pattern depended on the unit strength, the condition of the surface in contact between the units, and the grout strength for grouted prisms. The mortarless walls studied here included grout and steel reinforcement within the cells. In these walls, the load-carrying capacity, the displacement ductility, and the failure patterns were examined based on variations in the unit and grout compressive strength, yield strength, and reinforcement and grouting ratios. The thermal response of masonry units also merits further study to better understand the behavior of standard units as well as thermally efficient unit configurations. In this research, validated numerical models were used to evaluate the heat flow path, the distribution of temperatures, and the air velocities within the units. The results revealed the importance of including the three heat transfer mechanisms and the air flow within the cells of masonry units to better approximate the experimental thermal performance