Hybrid Reynolds-Averaged Navier–Stokes/Large-Eddy Simulations of F-16XL in Low-Speed High-Alpha Flight

Abstract

This paper reports on the computational fluid dynamics study of flow around the F-16XL aircraft in low-speed high-alpha flight. Previous work established that the computed pressure for this case compared less favorably with those measured in flight tests than did similar comparisons for cases at lower angles of attack. One reason suggested for the discrepancy was that the flow over the outer-wing panel was unsteady. This paper presents time-accurate computations with physical modeling that can capture such unsteady flow phenomena, namely, so-called hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation modeling. The simulations obtained are compared with those measured during flight testing of the vehicle as well as with results computed with more conventional steady physical modeling. Over the outer wing panel, the unsteady simulations compare substantially better than the steady results with the flight-test data, confirming unsteady aerodynamic effects are at play. At the inner-wing locations, the correlations among the simulations (unsteady and steady) and with the flight test are good, confirming the suspicion that the flow is mostly steady there. Although differences are found among all the results compared, they are not exceedingly large; but, the conclusion that unsteady aerodynamic effects are at play over the outer-wing panel are undeniable.