Overview and Summary of the Third AIAA High Lift Prediction Workshop

The third AIAA CFD High-Lift Prediction Workshop was held in Denver, Colorado, in June 2017. The goals of the workshop continued in the tradition of the first and second high-lift workshops: to assess the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in landing/takeoff (high-lift) configurations. This workshop analyzed the flow over two different configurations, a clean high-lift version of the NASA Common Research Model, and the JAXA Standard Model. The former was a CFD-only study, as experimental data were not available prior to the workshop. The latter was a nacelle/pylon installation study that included comparison with experimental wind tunnel data. The workshop also included a 2-D turbulence model verification exercise. Thirty-five participants submitted a total of 79 data sets of CFD results. A variety of grid systems (both structured and unstructured) as well as different flow simulation methodologies (including Reynolds-averaged Navier-Stokes and Lattice-Boltzmann) were used. This paper analyzes the combined results from all workshop participants. A statistical summary of the CFD results is also included

High-Lift OVERFLOW Analysis of the DLR-F11 Wind Tunnel Model

In response to the 2nd AIAA CFD High Lift Prediction Workshop, the DLR-F11 wind tunnel model is analyzed using the Reynolds-averaged Navier-Stokes flow solver OVERFLOW. A series of overset grids for a bracket-off landing configuration is constructed and analyzed as part of a general grid refinement study. This high Reynolds number (15.1 million) analysis is done at multiple angles-of-attack to evaluate grid resolution effects at operational lift levels as well as near stall. A quadratic constitutive relation recently added to OVERFLOW for improved solution accuracy is utilized for side-of-body separation issues at low angles-of-attack and outboard wing separation at stall angles. The outboard wing separation occurs when the slat brackets are added to the landing configuration and is a source of discrepancy between the predictions and experimental data. A detailed flow field analysis is performed at low Reynolds number (1.35 million) after pressure tube bundles are added to the bracket-on medium grid system with the intent of better understanding bracket/bundle wake interaction with the wing's boundary layer. Localized grid refinement behind each slat bracket and pressure tube bundle coupled with a time accurate analysis are exercised in an attempt to improve stall prediction capability. The results are inconclusive and suggest the simulation is missing a key element such as boundary layer transition. The computed lift curve is under-predicted through the linear range and over-predicted near stall, and the solution from the most complete configuration analyzed shows outboard wing separation occurring behind slat bracket 6 where the experiment shows it behind bracket 5. These results are consistent with most other participants of this workshop

OVERFLOW Contribution to HiLiftPW-3

We plan to perform the following sets of computations: For all our contributions (except where stated) Code: OVERFLOW, Turbulence model: SAnegRCQCR2000. - 1. Results will be submitted for both the full chord flap gap (Case 1a) and partially-sealed Chord Flap gap (Case 1c): 1. Grid Refinement Study; 2. Grids: structured overset grids supplied by HiLiftPW committee; 3. Connectivity: Domain Connectivity Framework, DCF. - 2. Results will be submitted for JAXA Standard Model and Nacelle/Pylon Off (Case 2a), Nacelle/Pylon On (Case 2c): 1. Alpha Study; 2. Grids: structured overset grids supplied by HiLiftPW committee; 3. Connectivity: Pegasus 5 (Peg5). - 3. A study of the effects of different connectivity paradigms: 1. DCF vs Peg5 for HLCRM cases; 2. DCF vs. C3P (NASA Ames) vs. Peg5 for JSM cases; 3. JSM grids will be the focus where we will hopefully see some type of trends with reference to wind tunnel data. - 4. Adaption cases will be attempted for (and submitted where appropriate): 1. Cases 1c,1d: HLCRM; 2. Cases 2c and 2d: JSM; 3. Grid: Near Body grids provided by committee, OffBody grids Cartesian; 4. AMR NearBody and OffBody Adaption. - 5. Case 3 Turbulence model verification study: 1. Grid: Series of 3 finest grids as defined on http://turbmodels.larc.nasa.gov/airfoilwakeverif.html; 2. Turbulence models: SAneg and SAneg RCQCR2000. OVERFLOW 2.2 is a Reynolds-averaged Navier-Stokes (RANS) code developed by NASA..

Drag Prediction for the NASA CRM Wing-Body-Tail Using CFL3D and OVERFLOW on an Overset Mesh

In response to the fourth AIAA CFD Drag Prediction Workshop (DPW-IV), the NASA Common Research Model (CRM) wing-body and wing-body-tail configurations are analyzed using the Reynolds-averaged Navier-Stokes (RANS) flow solvers CFL3D and OVERFLOW. Two families of structured, overset grids are built for DPW-IV. Grid Family 1 (GF1) consists of a coarse (7.2 million), medium (16.9 million), fine (56.5 million), and extra-fine (189.4 million) mesh. Grid Family 2 (GF2) is an extension of the first and includes a superfine (714.2 million) and an ultra-fine (2.4 billion) mesh. The medium grid anchors both families with an established build process for accurate cruise drag prediction studies. This base mesh is coarsened and enhanced to form a set of parametrically equivalent grids that increase in size by a factor of roughly 3.4 from one level to the next denser level. Both CFL3D and OVERFLOW are run on GF1 using a consistent numerical approach. Additional OVERFLOW runs are made to study effects of differencing scheme and turbulence model on GF1 and to obtain results for GF2. All CFD results are post-processed using Richardson extrapolation, and approximate grid-converged values of drag are compared. The medium grid is also used to compute a trimmed drag polar for both codes

Contributions to the Sixth Drag Prediction Workshop Using Structured, Overset Grid Methods

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143028/1/1.C034486.pd

Fiber degeneration associated with hyperphagia-inducing knife cuts in the hypothalamus

The pattern of axonal degeneration associated with hyperphagia-producing hypothalamic knife transections was investigated using the Fink-Heimer method for staining of degenerating axons and their terminal endings. Histological analysis of silver-stained material after parasagittal knife cuts which result in hyperphagia and obesity revealed fiber degeneration coursing longitudinally in the medial forebrain bundle including the perifornical component to reach the nucleus accumbens, the diagonal band, the preoptic-anterior hypothalamic junction, the lateral hypothalamus, the zona incerta, the periventricular thalamus, the parafascicular thalamic nucleus, the substantia nigra pars compacta, the central gray matter, the ventral tegmental area of T\u27sai and the superior colliculus. The data obtained in the present study lend support to the suggestion that projections coursing in the medial forebrain bundle interconnect the anteriomedial hypothalamus and the midbrain tegmentum and may underlie the hyperphagia and obesity produced by hypothalamic knife cuts. © 1980

Contributions to the Sixth Drag Prediction Workshop Using Structured, Overset Grid Methods

International audienceStructured-grid solutions obtained for the NASA Common Research Model for the Sixth AIAA Computational Fluid Dynamics Drag Prediction Workshop are detailed. Three different flow solvers were used among the contributors, and the numerical methodologies and turbulence modeling strategies employed by each code are described. Key results for all authors include grid convergence studies for the drag increment of a nacelle and pylon added to a wing–body configuration and a buffet study accounting for static aeroelastic deformation. Additional studies performed include feature-based adaptive mesh refinement and higher-order convective flux discretization, among others