STOL landing thrust: Reverser jet flowfields

Analysis tools and modeling concepts for jet flow fields encountered upon use of thrust reversers for high performance military aircraft are described. A semi-empirical model of the reverser ground wall jet interaction with the uniform cross flow due to aircraft forward velocity is described. This ground interaction model is used to demonstrate exhaust gas ingestion conditions. The effects of control of exhaust jet vector angle, lateral splay, and moving versus fixed ground simulation are discussed. The Adler/Baron jet-in-cross flow model is used in conjunction with three dimensional panel methods to investigate the upper surface jet induced flow field

Investigation of impingement region and wall jets formed by the interaction of high aspect ratio lift jets and a ground plane

Flow characteristics of impinging jets emanating from rectangular exit area converging nozzles of exit area aspect ratio four, six, and eight were investigated. Azimuthal distributions of wall jet radial momentum flux in the ground plane were strongly directional and sensitive to rectangular nozzle exit area aspect ratio, jet impingement angle, and height above ground, H/D. Effects of jet exit velocity profile nonuniformities were also investigated. Data from the single nozzle rectangular jet impringement investigations were incorporated into an existing VTOL aircraft ground flow field computer program. It is suggested that this program together with the Douglas Neumann program modified for V/STOL applications may be used for the analysis and prediction of flow fields and resulting forces and moments on multijet V/STOL aircraft hovering in ground effect

Fighting for Atlanta: Tactics, Terrain, and Trenches in the Civil War

Between 2005 and 2009, Earl J. Hess authored a superb trilogy of books that brought new light to oft-studied campaigns by focusing on the role of trenches and field fortifications in the Eastern Theater. More recently, the prolific historian published the Tom Watson Book Award winning Civil War Infantry Tactics: Training, Combat, and Small-Unit Effectiveness (2015) as well as a series of works detailing pivotal battles of the Atlanta Campaign. Thus, Fighting for Atlanta: Tactics, Terrain, and Trenches in the Civil War seems to be the natural convergence of years of research and writing

Civil War in the Southwest Borderlands, 1861-1867

Civil War historiography has been well served by the recent proliferation of borderland studies. This burgeoning corner of the conflict’s literature has added nuance to our understanding of emancipation, the war in Appalachia, the Confederate diaspora, the Native American experience, and the war’s transnational dimensions. Civil War in the Southwest Borderlands by Andrew E. Masich is an accessible and well-researched addition to the literature. In this sweeping, largely narrative history, Masich argues “that cultural groups fought civil wars in the Southwest Borderlands concurrent with and connected to the American Civil War and that such wars often occur when two or more ethnically or culturally distinct peoples occupy the same space and vie for survival and dominance” (4) The war between the Union and the Confederacy created new and oftentimes more destructive conflicts in a region already burdened with long standing tension and rivalries

Driving reform through communities of practice in scientific fields

Humans learn through social interactions therefore it is not surprising that we create around ourselves social structures that guide and support our learning as well as our practice. Communities of practice are one such social structure that exists within fields of science. Understanding the secondary cultures that are represented in the epistemology, practices, and perceptions of each field can help us better approach reform in fields using communities of practice as a starting point. The intersections of communities, culture, and change represent challenges to reform in education that should be explored and leveraged

Teaching and learning science in the 21st century: challenging critical assumptions in post-secondary science

It is widely agreed upon that the goal of science education is building a scientifically literate society. Although there are a range of definitions for science literacy, most involve an ability to problem solve, make evidence-based decisions, and evaluate information in a manner that is logical. Unfortunately, science literacy appears to be an area where we struggle across levels of study, including with students who are majoring in the sciences in university settings. One reason for this problem is that we have opted to continue to approach teaching science in a way that fails to consider the critical assumptions that faculties in the sciences bring into the classroom. These assumptions include expectations of what students should know before entering given courses, whose responsibility it is to ensure that students entering courses understand basic scientific concepts, the roles of researchers and teachers, and approaches to teaching at the university level. Acknowledging these assumptions and the potential for action to shift our teaching and thinking about post-secondary education represents a transformative area in science literacy and preparation for the future of science as a field

Leveraging communities of practice to build integrated professional learning communities for STEM education

In the modern educational era, there is an increasing focus on Science, Technology, Engineering and Math (STEM) education. Innovation and workforce preparation play a large role in the push to increase scientific literacy, thinking skills and high-skilled personnel. However, there are ongoing issues with reforming education to meet these goals as well as the recruitment and retention of students in these fields. STEM and the various other iterations in which it is found, represents a challenge in education, as there are often many intersecting cultures, epistemologies, practices and expectations that are unique to each of the represented fields. As a result, educators often struggle with creating STEM experiences and programs that truly integrate each of the disciplines in a meaningful way. This discussion explores the potential role of leveraging existing communities of practice into Professional Learning Communities in order to shift the attention toward student experiences while more clearly defining the goals, roles and expectations in STEM

Civil War In The Southwest Borderlands, 1861-1867

The Civil War\u27s civil wars Civil War historiography has been well served by the recent proliferation of borderland studies. This burgeoning corner of the conflict\u27s literature has added nuance to our understanding of emancipation, the war in Appalachia, the Confederate diaspora, the Native American...

Exploring Inflated Pahohoe Lava Flow Morphologies and the Effects of Cooling Using a New Simulation Approach

Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth (e.g., Figure 1) indicate that the emplacement process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. Thus, interpretation of emplacement conditions for pahoehoe lava flows on Mars requires fundamentally different models. A new model that implements a simulation approach has recently been developed that allows exploration of a variety of key influences on pahoehoe lobe emplacement (e.g., source shape, confinement, slope). One important factor that has an impact on the final topographic shape and morphology of a pahoehoe lobe is the volumetric flow rate of lava, where cooling of lava on the lobe surface influences the likelihood of subsequent breakouts

Inferred Lunar Boulder Distributions at Decimeter Scales

Block size distributions of impact deposits on the Moon are diagnostic of the impact process and environmental effects, such as target lithology and weathering. Block size distributions are also important factors in trafficability, habitability, and possibly the identification of indigenous resources. Lunar block sizes have been investigated for many years for many purposes [e.g., 1-3]. An unresolved issue is the extent to which lunar block size distributions can be extrapolated to scales smaller than limits of resolution of direct measurement. This would seem to be a straightforward statistical application, but it is complicated by two issues. First, the cumulative size frequency distribution of observable boulders rolls over due to resolution limitations at the small end. Second, statistical regression provides the best fit only around the centroid of the data [4]. Confidence and prediction limits splay away from the best fit at the endpoints resulting in inferences in the boulder density at the CPR scale that can differ by many orders of magnitude [4]. These issues were originally investigated by Cintala and McBride [2] using Surveyor data. The objective of this study was to determine whether the measured block size distributions from Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC-NAC) images (m-scale resolution) can be used to infer the block size distribution at length scales comparable to Mini-RF Circular Polarization Ratio (CPR) scales, nominally taken as 10 cm. This would set the stage for assessing correlations of inferred block size distributions with CPR returns [6]