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The Second International Vortex Flow Experiment provided a variety of experimental data for a 65° swept delta wing sharp and blunt leading edges. Flow details including forces and moments, surface pressures, Pressure Sensitive Paint measurements, and off-surface flow variables from Particle Image Velocimetry were made available for comparisons with computational simulations. This paper concentrates on some typical problems of delta wings with rounded leading edges at subsonic speed: the prediction of the main leading edge separation, the generation of the second inner vortex, the effect of transition, and Reynolds number effects.

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.

The objective of the Cranked-Arrow Wing Aerodynamics Project International was to allow a comprehensive validation of computational fluid dynamics methods against the Cranked-Arrow Wing Aerodynamic ...

Ten groups participating in the Cranked Arrow Wing Aerodynamics Project International (CAWAPI) within the NATO-RTO task group AVT 113 have contributed viscous simulations of a full scale model of the F-16XL aircraft at different flight conditions. Three different classes of grids have been used by the different participants: a common structured grid, a common unstructured grid, and so-called individually tailored grids, which have been used by four participants: Lockheed Martin Aeronautics Company, University of Tennessee, Boeing Phantom Works, and EADS Military Air Systems. This paper focuses on the use of these individually generated grids. The different grid generation techniques and strategies (nonadapted, manually adapted, and solution-based adapted) are discussed and the solutions obtained in these individually tuned grids are compared with flight test data for different test cases.

flow solvers and the behavior found to be both model and code-specific. For one flow solver, these errors in skin friction were parameterized such that the deviation can be estimated in more complex cases. This is expected to be particularly useful in industrial simulations, where the number of grid points is limited by computational cost constraints. Additionally, feedback is provided to the user regarding local grid quality enabling targeted improvements, either manually or potentially using automatic grid adaption. The approach can be viewed as the incorporation of best practice guidelines within the code itself, thus reducing the necessary user expertise. The error approximation has been shown to be successful for various airfoil cases and the application to a full aircraft configuration is planned.

The Second International Vortex Flow Experiment provided a variety of experimental data for a 65° delta wing with sharp and blunt/rounded leading edges. Flow measurements including forces and moments, surface pressures, Pressure Sensitive Paint measurements, and off-surface flow variables from Particle Image Velocimetry were made available for comparisons with computational simulations. A number of test cases were chosen for simulation by seven numerical groups, and a summary of their results is presented here. The ability of computational fluid dynamics to predict such flow features as the dual primary vortex system found on the blunt leading edge configuration and a shock/vortex interaction for the sharp leading edge are assessed. While computational simulation has made great strides in recent years, there are still areas where further improvement can be made, including in turbulence modeling, transition modeling, and the ability to accurately compute unsteady flows.

The objective of the Cranked-Arrow Wing Aerodynamics Project International (CAWAPI) was to allow a comprehensive validation of Computational Fluid Dynamics methods against the CAWAP flight database. A major part of this work involved the generation of high-quality computational grids. Prior to the grid generation an IGES file containing the air-tight geometry of the F-16XL aircraft was generated by a cooperation of the CAWAPI partners. Based on this geometry description both structured and unstructured grids have been generated. The baseline structured (multi-block) grid (and a family of derived grids) has been generated by the National Aerospace Laboratory NLR. Although the algorithms used by NLR had become available just before CAWAPI and thus only a limited experience with their application to such a complex configuration had been gained, a grid of good quality was generated well within four weeks. This time compared favourably with that required to produce the unstructured grids in CAWAPI. The baseline all-tetrahedral and hybrid unstructured grids has been generated at NASA Langley Research Center and the USAFA, respectively. To provide more geometrical resolution, trimmed unstructured grids have been generated at EADS-MAS, the UTSimCenter, Boeing Phantom Works and KTH/FOI. All grids generated within the framework of CAWAPI will be discussed in the article. Both results obtained on the structured grids and the unstructured grids showed a significant improvement in agreement with flight test data in comparison with those obtained on the structured multi-block grid used during CAWAP.