Turbulence investigation of the NASA common research model wing tip vortex

Abstract

The paper presents high-speed stereo particle image velocimetry investigation of the NASA Common Research Model wing tip vortex. A three-percent scaled semi-span model, without nacelle and pylon, was tested in the 32-by 48-inch Indraft tunnel, at the Fluid Mechanics Laboratory at the NASA Ames Research Center. Turbulence investigation of the wing tip vortex is presented. Measurements of the wing-tip vortex were performed in a vertical cross-stream plane three tip-chords downstream of the wing tip trailing edge with a 2 kHz sampling rate. Experimental data are analyzed in the invariant anisotropy maps for three various angles of attack (0°, 2°, and 4°) and the same speed generated in the tunnel (V ∞ = 50 m/s). This corresponds to a chord Reynolds number 2.6810 5 , where the chord length of 3" is considered the characteristic length. The region of interest was x = 220 mm and y = 90 mm. The 20 000 particle image velocimetry samples were acquired at each condition. Velocity fields and turbulence statistics are given for all cases, as well as turbulence structure in the light of the invariant theory. Prediction of the wing tip vortices is still a challenge for the computational fluid dynamics codes due to significant pressure and velocity gradients.

Turbulence Structure and Dynamics Investigation of Turbulent Swirl Flow in Pipe Using High-Speed Stereo PIV Data

“…where T is tensor of Reynolds stresses and k is turbulence kinetic energy. The mathematical formulation of three independent invariants and their application to vortex investigation is presented in [13][14][15]22,23] in the following way:…”

“…The determination of the second and the third invariants is possible using the HSS PIV experimental results, which provide all three of the velocity components. All of the possible states of turbulence anisotropy belong to the anisotropy invariant map-curvilinear triangle 012, i.e., the Lumley triangle (Figure 9), defined by Equation (3.4) in paper [22]. Figure 9 presents coordinates of the triangle vertices, of which 0 denotes the state of the three-component isotropic turbulence, point 1 corresponds to the boundary layer of the one-component isotropic turbulence, and 2 is two-component isotropic turbulence.…”

“…HSS PIV data are implemented in the invariant maps in the case of turbomachinery for the first time in the papers. The presented idea in this paper is successfully implemented and published in the papers [22,23], and this was the case of the wing tip vortex formed behind the NASA CRM wing. So, it is shown here that it could be equally successful in application in turbomachinery.…”

High speed stereoscopic PIV investigation of the statistical characteristics of the axially restricted turbulent swirl flow behind the axial fan in pipe

“…8,9 Paper 10 demonstrates the method of calculation of the invariant maps on the basis of the high-speed stereo particle image velocimetry (HSS PIV) results. Application of this approach is continued in a research of the wing tip vortex, 11,12 as well as in this paper. Vortex dynamics, vorticity and vortex detection, as well as turbulence structure investigation of the turbulent swirl flow behind the axial fan on the simpler test rig, with application of the invariant theory is reported in C ˇantrak and Jankovic´.…”