Results from the Fifth AIAA Computational Fluid Dynamics Drag Prediction Workshop are presented. As with past workshops, numerical calculations are performed using industry-relevant geometry, methodology, and test cases. This workshop focused on force/moment predictions for the NASA Common Research Model wing-body configuration, including a grid refinement study and an optional buffet study. The grid refinement study used a common grid sequence derived from a multiblock topology structured grid. Six levels of refinement were created, resulting in grids ranging from 0.64 x 10(6) to 138 x 10(6) hexahedra, a much larger range than is typically seen. The grids were then transformed into structured overset and hexahedral, prismatic, tetrahedral, and hybrid unstructured formats all using the same basic cloud of points. This unique collection of grids was designed to isolate the effects of grid type and solution algorithm by using identical point distributions. This study showed reduced scatter and standard deviation from previous workshops. The second test case studied buffet onset at M = 0.85 using the medium grid (5.1 x 10(6) nodes) from the sequence described earlier. The prescribed alpha sweep used finely spaced intervals through the zone where wing separation was expected to begin. Some solutions exhibited a large side of body separation bubble that was not observed in the wind-tunnel results. An optional third case used three sets of geometry, grids, and conditions from the Turbulence Model Resource website prepared by the Turbulence Model Benchmarking Working Group. These simple cases were intended to help identify potential differences in turbulence model implementation. Although a few outliers and issues affecting consistency were identified, the majority of participants produced consistent results.

Results from the Fourth AIAA Drag Prediction Workshop are summarized. The workshop focused on the prediction of both absolute and differential drag levels for wing-body and wing-body/horizontal-tail configurations of the NASA Common Research Model, which is representative of transonic transport aircraft. Numerical calculations are performed using industry-relevant test cases that include lift-specific flight conditions, trimmed drag polars, downwash variations, drag rises, and Reynolds-number effects. Drag, lift, and pitching moment predictions from numerous Reynolds-averaged Navier-Stokes computational fluid dynamics methods are presented. Solutions are performed on structured, unstructured, and hybrid grid systems. The structured-grid sets include point-matched multiblock meshes and overset grid systems. The unstructured and hybrid grid sets comprise tetrahedral, pyramid, prismatic, and hexahedral elements. Effort is made to provide a high-quality and parametrically consistent family of grids for each grid type about each configuration under study. The wing-body/horizontal families comprise coarse, medium, and fine grids; an optional extrafine grid augments several of the grid families. These mesh sequences are used to determine asymptotic grid-convergence characteristics of the solution sets and to estimate grid-converged absolute drag levels of the wing-body/horizontal configuration using Richardson extrapolation.

Results from the 5, AIAA CFD Drag Prediction Workshop are presented. This workshop is focused on force/moment predictions for the NASA Common research wing-body configuration, including a grid refinement study and an optional buffet study. The article presents the summary of data of all participants.

A HiLiftPW-1 post-workshop activity is presented, whereby the DLR TAU transition prediction module is used to determine transition locations for the NASA trapezoidal wing. Transitional RANS computations are then performed over the angle-of-attack range of 6 to 37 degrees at a Mach number of 0.2 and Reynolds number of 4.3 million. The transitional RANS results show a major improvement in comparison to previously performed fullyturbulent computations, but still show deciencies in the wing tip region.

On the basis of the DLR, German Aerospace Center contribution to the fourth AIAA Drag Prediction Workshop, a procedure is documented to produce an unstructured grid family as self-similar as possible, with a specific procedure for steering the near-field advancing-layer process. A novel hybrid mesh generation approach is presented, in which adjoint-based dissipation error evaluations are successfully employed to improve the solution accuracy for specific conditions. An intrinsic deficit of the standard mesh generation procedure results in an unsatisfying resolution of flow features at the wing body junction. For this case, a solution strategy based on chimera grids is tested and found to improve the aerodynamic evaluation.

Results from the Fourth AIAA Drag Prediction Workshop (DPW-IV) are summarized. The workshop focused on the prediction of both absolute and differential drag levels for wing-body and wing-body-horizontal-tail configurations that are representative of transonic transport air- craft. Numerical calculations are performed using industry-relevant test cases that include lift- specific flight conditions, trimmed drag polars, downwash variations, dragrises and Reynolds- number effects. Drag, lift and pitching moment predictions from numerous Reynolds-Averaged Navier-Stokes computational fluid dynamics methods are presented. Solutions are performed on structured, unstructured and hybrid grid systems. The structured-grid sets include point- matched multi-block meshes and over-set grid systems. The unstructured and hybrid grid sets are comprised of tetrahedral, pyramid, prismatic, and hexahedral elements. Effort is made to provide a high-quality and parametrically consistent family of grids for each grid type about each configuration under study. The wing-body-horizontal families are comprised of a coarse, medium and fine grid; an optional extra-fine grid augments several of the grid families. These mesh sequences are utilized to determine asymptotic grid-convergence characteristics of the solution sets, and to estimate grid-converged absolute drag levels of the wing-body-horizontal configuration using Richardson extrapolation.

A summary about the DLR, German Aerospace Center, results from the fourth AIAA Computational Fluid Dynamics (CFD) Drag Prediction Workshop (DPW) is presented. Compared to the investigations in the previous three workshops the latest workshop had a stronger focus on drag and trim drag predictions as well as pitching moment calculations. Therefore the new Common Research Model (CRM) developed by NASA's Subsonic Fixed Wing Aerodynamics Technical Working Group is applied. It represents a state of the art transonic transport aircraft configuration and in contrast to the configurations previously used it includes a horizontal tail plane (HTP) with three different tail settings.

On the basis of the DLR contribution to DPW4, a procedure to produce an unstructured grid-convergence family as self-similar as possible is documented, with a specific procedure for steering the nearfield, advancing-layer process. A novel hybrid mesh generation approach is presented, in which adjoint-based dissipation error evaluations are successfully employed to improve the solution accuracy for specific conditions. An intrinsic deficit of the standard mesh generation procedure, results in an unsatisfying resolution of ow features at the wing-body junction. For this case, an alternative solution strategy based on chimera grids is tested and found to improve the aerodynamic evaluation.

It has been observed that delta wings placed in a transonic freestream can experience a sudden movement of the vortex breakdown location as the angle of incidence is increased. The current paper uses computational fluid dynamics to examine this behavior in detail. The study shows that a shock/vortex interaction is responsible. The balance of the vortex strength and axial flow and the shock strength are examined to provide an explanation of the sensitivity of the breakdown location. Limited experimental data are available to supplement the computational fluid dynamics results in certain key respects, and the ideal synergy between computational fluid dynamics and experiments for this problem is considered.

Nine organizations participated in the Cranked-Arrow Wing Aerodynamics Project International study and have contributed steady and unsteady viscous simulations of a full-scale semispan model of the F-16XL aircraft. Three different categories of flight Reynolds/Mach number combinations are computed and compared with flight-test measurements for the purpose of code validation and improved understanding of the flight physics. Steady-state simulations are done with several turbulence models (of different complexity, with no topology information required) that overcome Boussinesq-assumption problems in vortical flows. Detached-eddy simulation and its successor, delayed detached-eddy simulation, are used to compute the time-accurate flow development. Common structured and unstructured grids as well as individually adapted unstructured grids were used. Although discrepancies are observed in the comparisons, overall reasonable agreement is demonstrated for surface pressure distribution, local skin friction, and boundary velocity profiles at subsonic speeds. The physical modeling, be it steady or unsteady flow, and the grid resolution both contribute to the discrepancies observed in the comparisons with flight data, but at this time, how much each part contributes to the whole cannot be determined. Overall, it can be said that the technology readiness of computational fluid dynamics simulation technology for the study of vehicle performance has matured since 2001, such that it can be used today with a reasonable level of confidence for complex configurations.

A steady computational fluid dynamic (CFD) study is performed over a wide range of Reynolds numbers at low incidence and subsonic speeds on the Second International Vortex Flow Experiment (VFE-2) b ...

Numerical results are presented and discussed in this paper allowing a deeper and more precise characterization of the unique double vortex system, which develops on the second International Vortex ...