Study of Geometric Porosity on Static Stability and Drag Using Computational Fluid Dynamics for Rigid Parachute Shapes

This paper explores use of computational fluid dynamics to study the eect of geometric porosity on static stability and drag for NASA's Multi-Purpose Crew Vehicle main parachute. Both of these aerodynamic characteristics are of interest to in parachute design, and computational methods promise designers the ability to perform detailed parametric studies and other design iterations with a level of control previously unobtainable using ground or flight testing. The approach presented here uses a canopy structural analysis code to define the inflated parachute shapes on which structured computational grids are generated. These grids are used by the computational fluid dynamics code OVERFLOW and are modeled as rigid, impermeable bodies for this analysis. Comparisons to Apollo drop test data is shown as preliminary validation of the technique. Results include several parametric sweeps through design variables in order to better understand the trade between static stability and drag. Finally, designs that maximize static stability with a minimal loss in drag are suggested for further study in subscale ground and flight testing

Implementation of Implicit Adaptive Mesh Refinement in an Unstructured Finite-Volume Flow Solver

This paper explores the implementation of adaptive mesh refinement in an unstructured, finite-volume solver. Unsteady and steady problems are considered. The effect on the recovery of high-order numerics is explored and the results are favorable. Important to this work is the ability to provide a path for efficient, implicit time advancement. A method using a simple refinement sensor based on undivided differences is discussed and applied to a practical problem: a shock-shock interaction on a hypersonic, inviscid double-wedge. Cases are compared to uniform grids without the use of adapted meshes in order to assess error and computational expense. Discussion of difficulties, advances, and future work prepare this method for additional research. The potential for this method in more complicated flows is described

Dynamic Mesh CFD Simulations of Orion Parachute Pendulum Motion During Atmospheric Entry

This paper demonstrates the usage of computational fluid dynamics to study the effects of pendulum motion dynamics of the NASAs Orion Multi-Purpose Crew Vehicle parachute system on the stability of the vehicles atmospheric entry and decent. Significant computational fluid dynamics testing has already been performed at NASAs Johnson Space Center, but this study sought to investigate the effect of bulk motion of the parachute, such as pitching, on the induced aerodynamic forces. Simulations were performed with a moving grid geometry oscillating according to the parameters observed in flight tests. As with the previous simulations, OVERFLOW computational fluid dynamics tool is used with the assumption of rigid, non-permeable geometry. Comparison to parachute wind tunnel tests is included for a preliminary validation of the dynamic mesh model. Results show qualitative differences in the flow fields of the static and dynamic simulations and quantitative differences in the induced aerodynamic forces, suggesting that dynamic mesh modeling of the parachute pendulum motion may uncover additional dynamic effects

Panoptic segmentation forecasting

Our goal is to forecast the near future given a set of recent observations. We think this ability to forecast, i.e., to anticipate, is integral for the success of autonomous agents which need not only passively analyze an observation but also must react to it in real-time. Importantly, accurate forecasting hinges upon the chosen scene decomposition. We think that superior forecasting can be achieved by decomposing a dynamic scene into individual 'things' and background 'stuff'. Background 'stuff' largely moves because of camera motion, while foreground 'things' move because of both camera and individual object motion. Following this decomposition, we introduce panoptic segmentation forecasting. Panoptic segmentation forecasting opens up a middle-ground between existing extremes, which either forecast instance trajectories or predict the appearance of future image frames. To address this task we develop a two-component model: one component learns the dynamics of the background stuff by anticipating odometry, the other one anticipates the dynamics of detected things. We establish a leaderboard for this novel task, and validate a state-of-the-art model that outperforms available baselines

The circulation and water masses in the Gulf of the Farallones

Six ADCP and CTD ship surveys of the continental shelf and slope in the vicinity of the Gulf of the Farallones, CA, were conducted in 1990}1992. ADCP data provide much more detail on the structure of the currents over the slope and shelf in the Gulf and reveal a persistent, largely barotropic poleward #ow with a complex mesoscale #ow "eld superimposed. The directly measured currents are not well represented by the geostrophic velocity "elds derived from hydrographic casts. Important upper-ocean circulation features include: a Slope Countercurrent (SCC), variable shelf circulation, and submesoscale eddy-like features. The SCC was present in all seasons and is believed due to a strong year-round positive wind-stress curl enhanced by Point Reyes. Its #ow was poleward throughout the upper 300 m, and often surface intensi"ed. Poleward transport in the upper 400 m was 1}3 Sv, much greater than previous geostrophic estimates for the California Current System constrained to a 500 dbar reference level. The shelf circulation was much more variable than the SCC and generally exhibited a pattern consistent with classic Ekman dynamics, responding to synoptic wind forcing. Submesoscale vortices, or eddies, often dominated the general #ow "eld. These eddies are thought to be generated by the frictional torque associated with current}topography interactions. Their centers typically have a distinct water type associated with either the SCC or the southward-#owing California Current. Higher spiciness anomalies, representing a higher percentage of Paci"c Equatorial Water (PEW), were typically found in the core of the SCC or within anticyclonic eddies. Lower (bland) spiciness anomalies, characteristic of a higher percentage of Paci"c Subarctic Water (PSAW), were associated with cyclonic eddies. While these circulation features were largely barotropic, the #ow also adjusted baroclinically to changes in the density "eld, as di!erent water types were advected by the general #ow "eld or by mesoscale instabilities in the large-scale boundary currents as they interacted with topography. Despite a seasonal cycle in regional wind and ocean temperature time series, there is no obvious seasonal pattern in the circulation. Most of the temporal variability in the current appears to be due to synoptic and interannual variations in atmospheric forcing. Because of the very dynamic three-dimensional nature of the regional circulation, the Gulf of the Farallones is likely to be a center for active mixing and exchange between the coastal and California Current waters, relative to most US west coast locales

Assessment of Turbulent Shock-Boundary Layer Interaction Computations Using the OVERFLOW Code

The performance of two popular turbulence models, the Spalart-Allmaras model and Menter s SST model, and one relatively new model, Olsen & Coakley s Lag model, are evaluated using the OVERFLOWcode. Turbulent shock-boundary layer interaction predictions are evaluated with three different experimental datasets: a series of 2D compression ramps at Mach 2.87, a series of 2D compression ramps at Mach 2.94, and an axisymmetric coneflare at Mach 11. The experimental datasets include flows with no separation, moderate separation, and significant separation, and use several different experimental measurement techniques (including laser doppler velocimetry (LDV), pitot-probe measurement, inclined hot-wire probe measurement, preston tube skin friction measurement, and surface pressure measurement). Additionally, the OVERFLOW solutions are compared to the solutions of a second CFD code, DPLR. The predictions for weak shock-boundary layer interactions are in reasonable agreement with the experimental data. For strong shock-boundary layer interactions, all of the turbulence models overpredict the separation size and fail to predict the correct skin friction recovery distribution. In most cases, surface pressure predictions show too much upstream influence, however including the tunnel side-wall boundary layers in the computation improves the separation predictions

Function and flexibility of object exploration in kea and New Caledonian crows

Data collection with the New Caledonian crows was funded by an International Seedcorn Award from the University of York to M.L.L. This study was supported by a Rutherford Discovery Fellowship (A.H.T.). Our data are deposited at: http://dx.doi.org/10.5061/dryad.dq04j [48].A range of non-human animals frequently manipulate and explore objects in their environment, which may enable them to learn about physical properties and potentially form more abstract concepts of properties such as weight and rigidity. Whether animals can apply the information learned during their exploration to solve novel problems, however, and whether they actually change their exploratory behavior to seek functional information about objects have not been fully explored. We allowed kea (Nestor notabilis) and New Caledonian crows (Corvus moneduloides) to explore sets of novel objects both before and after encountering a task in which some of the objects could function as tools. Following this, subjects were given test trials in which they could choose among the objects they had explored to solve a tool-use task. Several individuals from both species performed above chance on these test trials, and only did so after exploring the objects, compared with a control experiment with no prior exploration phase. These results suggest that selection of functional tools may be guided by information acquired during exploration. Neither kea nor crows changed the duration or quality of their exploration after learning that the objects had a functional relevance, suggesting that birds do not adjust their behavior to explicitly seek this information.Publisher PDFPeer reviewe

Computational Modeling to Limit the Impact Displays and Indicator Lights Have on Habitable Volume Operational Lighting Constraints

Even with no ambient lighting system "on", the International Space Station glows at night. The glow is caused by indicator lamps and displays that are not included with the specification of the ambient lighting system. How does this impact efforts to improve the astronaut's lighting environment to promote more effective sleep patterns? Do the extra indicators and displays add enough light to change the spectrum of light the crew sees during the day as well? If spacecraft environments are specifically engineered to have an ambient lighting system that emits a spectrum promoting a healthy circadian response, is there a way control the impact? The goal of this project is to investigate how additional light sources, such as displays and indicators change the effective light spectrum of the architectural lighting system and how impacts can be mitigated

Subsecond pore-scale displacement processes and relaxation dynamics in multiphase flow

With recent advances at X‐ray microcomputed tomography (μCT) synchrotron beam lines, it is now possible to study pore‐scale flow in porous rock under dynamic flow conditions. The collection of four‐dimensional data allows for the direct 3‐D visualization of fluid‐fluid displacement in porous rock as a function of time. However, even state‐of‐the‐art fast‐μCT scans require between one and a few seconds to complete and the much faster fluid movement occurring during that time interval is manifested as imaging artifacts in the reconstructed 3‐D volume. We present an approach to analyze the 2‐D radiograph data collected during fast‐μCT to study the pore‐scale displacement dynamics on the time scale of 40 ms which is near the intrinsic time scale of individual Haines jumps. We present a methodology to identify the time intervals at which pore‐scale displacement events in the observed field of view occur and hence, how reconstruction intervals can be chosen to avoid fluid‐movement‐induced reconstruction artifacts. We further quantify the size, order, frequency, and location of fluid‐fluid displacement at the millisecond time scale. We observe that after a displacement event, the pore‐scale fluid distribution relaxes to (quasi‐) equilibrium in cascades of pore‐scale fluid rearrangements with an average relaxation time for the whole cascade between 0.5 and 2.0 s. These findings help to identify the flow regimes and intrinsic time and length scales relevant to fractional flow. While the focus of the work is in the context of multiphase flow, the approach could be applied to many different μCT applications where morphological changes occur at a time scale less than that required for collecting a μCT scan

Transport processes investigation: A necessary first step in site scale characterization plans

We propose an approach, which we call the Transport Processes Investigation or TPI, to identify and verify site-scale transport processes and their controls. The TPI aids in the formulation of an accurate conceptual model of flow and transport, an essential first step in the development of a cost effective site characterization strategy. The TPI is demonstrated in the highly complex vadose zone of glacial tills that underlie the Fernald Environmental Remediation Project (FEMP) in Fernald, Ohio. As a result of the TPI, we identify and verify the pertinent flow processes and their controls, such as extensive macropore and fracture flow through layered clays, which must be included in an accurate conceptual model of site-scale contaminant transport. We are able to conclude that the classical modeling and sampling methods employed in some site characterization programs will be insufficient to characterize contaminant concentrations or distributions at contaminated or hazardous waste facilities sited in such media