Analysis of Delta-Wing Vortical Substructures Using Detached-Eddy Simulation

Abstract

An u nderstanding of the vortical structures which comprise the vortical flowfield around slender bodies is essential for the development of highly maneuverable and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missile s at extreme flight conditions. D emands for more maneuverable air vehicles have pushed the limits of current CFD methods in the high Reynolds number regime. Simulation methods must be able to accurately describe the unsteady, vortic al flowfields associated with fighter aircraft at Reynolds numbers more representative of full scale vehicles. It is the goal of this paper to demonstrate the ability of DetachedEddy Simulation, a hybrid RANS-LES method, to accurately model the vortical flowfield over a slender delta wing at Reynolds numbers above 1 million. Detached-Eddy Simulation has successfully predicted the location of the vortex breakdown phenomenon and the goal of the current effort is to analyze and assess the influence of vortical substructures in the separating shear layers which roll up to form the leading-edge vortices. Very detailed experiments performed at O NERA using 3 -D Laser Doppler Velocimetry measurement will be used to compare simulations utilizing DES turbulence models. The computational results provide novel insight into the formation and impact of the vortical substructures in the separating shear layers on the entire vortical flowfield.

Numerical Simulation on the Steady and Unsteady Internal Flows of a Centrifugal Pump

“…Near solid walls in the grid system where the value of ω is very large, k still remains the finite value, and k l −ω is smaller than max( x, y,z ) Δ= Δ Δ Δ . Therefore RANS simulation with SST k-ω model is suitable for turbulent flow computation near walls as described by Mitchell et al (2006) and C DES = 0.65 for unstructured grid system.…”

Experiences in accurately predicting time-dependent flows

“…Each grid in the series is refined in all three coordinate directions by a factor pffiffi ffi of 1= 2 from the previous grid in the series. Results from the grids were presented in [19], including a fifth grid created with adaptive mesh refinement (AMR) that had 3.2 million cells (Grid 5).…”

“…Due to the relative symmetry of the flow field over the leeward surface of the delta wing, only the portside flow field was examined. Details of the model, the wind tunnel, and LDV system, as well as the computational study are specified in [19]. Table 3 Grids used in 701 leading-edge sweep delta wing computations [19] Grid Name Number of cells (millions) Four semi-span grids were created for the delta wing (as described in Table 3) of 1.2 (Grid 1), 2.7 (Grid 2), 6.7 (Grid 3), and 10.7 million cells (Grid 4).…”

“…Details of the model, the wind tunnel, and LDV system, as well as the computational study are specified in [19]. Table 3 Grids used in 701 leading-edge sweep delta wing computations [19] Grid Name Number of cells (millions) Four semi-span grids were created for the delta wing (as described in Table 3) of 1.2 (Grid 1), 2.7 (Grid 2), 6.7 (Grid 3), and 10.7 million cells (Grid 4). Each grid in the series is refined in all three coordinate directions by a factor pffiffi ffi of 1= 2 from the previous grid in the series.…”

Detached-Eddy Simulation of the Vortical Flowfield about the VFE-2 Delta Wing

“…These NASA data were given to the working group for code validation from the beginning of the project. 26 Specifically for the purposes of the AVT-131 working group, DLR measurements with the 2/3-scaled NASA Low-Turbulence Pressure Tunnel (LTPT) model were obtained. Several test campaigns delivered surface pressure data and flow field data for increasing knowledge of the behavior of the rounded leading-edge delta wing 4 American Institute of Aeronautics and Astronautics configuration.…”