Multilayer Insulation Ascent Venting Model

The thermal and venting transient experienced by tank-applied multilayer insulation (MLI) in the Earth-to-orbit environment is very dynamic and not well characterized. This new predictive code is a first principles-based engineering model which tracks the time history of the mass and temperature (internal energy) of the gas in each MLI layer. A continuum-based model is used for early portions of the trajectory while a kinetic theory-based model is used for the later portions of the trajectory, and the models are blended based on a reference mean free path. This new capability should improve understanding of the Earth-to-orbit transient and enable better insulation system designs for in-space cryogenic propellant systems

Experimental validation of the quadratic constitutive relation in supersonic streamwise corner flows

The quadratic constitutive relation is a simple extension to the linear eddy-viscosity hypothesis and has shown some promise in improving the computation of flow along streamwise corner geometries. In order to further investigate these improvements, the quadratic model is validated by comparing RANS simulations of a Mach 2.5 wind tunnel flow with high-quality experimental velocity data. Careful set up and assessment of computations using detailed characterisation data of the overall flow field suggests a minimum expected discrepancy of approximately 3% for any experimental–computational velocity comparisons. The corner regions of the rectangular cross-section wind tunnel exhibit velocity differences of 7% between experimental data and computations with linear eddy-viscosity models, but these discrepancies are reduced to 4–5% when the quadratic constitutive relation is used. This improvement can be attributed to a better prediction of the corner boundary-layer structure, due to computations reproducing the stress-induced streamwise vortices which are known to exist in this flow field. However, the strength and position of these vortices do not correspond exactly with those in the measured flow. A further observation from this study is the appearance of additional, non-physical vortices when the value of the quadratic coefficient in the relation exceeds the recommended value of 0.3.This material is based upon work supported by the US Air Force Office of Scientific Research under award number FA9550–16–1–0430

Ecological distribution conflicts as forces for sustainability : an overview and conceptual framework

Unidad de excelencia María de Maeztu MdM-2015-0552Centre: ICTA Digital object identifier for the 'European Research Council' (http://dx.doi.org/10.13039/501100000781) Digital object identifier for 'Horizon 2020' (http://dx.doi.org/10.13039/501100007601).Can ecological distribution conflicts turn into forces for sustainability? This overview paper addresses in a systematic conceptual manner the question of why, through whom, how, and when conflicts over the use of the environment may take an active role in shaping transitions toward sustainability. It presents a conceptual framework that schematically maps out the linkages between (a) patterns of (unsustainable) social metabolism, (b) the emergence of ecological distribution conflicts, (c) the rise of environmental justice movements, and (d) their potential contributions for sustainability transitions. The ways how these four processes can influence each other are multi-faceted and often not a foretold story. Yet, ecological distribution conflicts can have an important role for sustainability, because they relentlessly bring to light conflicting values over the environment as well as unsustainable resource uses affecting people and the planet. Environmental justice movements, born out of such conflicts, become key actors in politicizing such unsustainable resource uses, but moreover, they take sometimes also radical actions to stop them. By drawing on creative forms of mobilizations and diverse repertoires of action to effectively reduce unsustainabilities, they can turn from 'victims' of environmental injustices into 'warriors' for sustainability. But when will improvements in sustainability be lasting? By looking at the overall dynamics between the four processes, we aim to foster a more systematic understanding of the dynamics and roles of ecological distribution conflicts within sustainability processes

Detached-Eddy Simulation of Slat and Flap Aerodynamics for a High-Lift Wing

Three-dimensional multi-element wings are simulated to investigate slat and flap aerodynamics using Detached-Eddy Simulation. The computations are performed by solving the Navier-Stokes equations on unstructured grids. All of the computed cases include the main wing with a half-span flap deflected to 39 degrees and a three-quarter-span slat deflected to 6 degrees. Computations of the model, which simulates a landing configuration at 10 degrees angle of attack and a chord-based Reynolds number of 3.7 million, are validated with surface pressure measurements acquired at the NASA Ames 7- by 10-Foot Wind Tunnel. The results increase the computational knowledge of how to accurately model the flow physics of a multi-element wing with three-dimensional flow by using Detached-Eddy Simulation