Analysis and Control of Transonic Cavity Flow Using DES and LES

Abstract

Numerical simulations of the flow inside a cavity with a length-to-depth ratio (L/D) of 5 and a width-to-depth ratio (W/D) of 1 have been conducted using Large-Eddy Simulation (LES) and Detached-Eddy Simulation (DES). The cavity is exposed to a free-stream of zero incidence, M ∞ = 0.85 and Re = 1 × 10 6 (based on the cavity length). Previous numerical simulations of 3D cavities using Unsteady Reynolds-Averaged Navier-Stokes (URANS) have proved difficult in accurately predicting the noise level and frequency content (and hence flow features) inside cavities. Simulation techniques such as LES and DES are therefore applied to the 3D cavity and this paper demonstrates its superior effectiveness relative to URANS in the analysis of cavity flows. Plots depicting the level of noise, frequency content and velocity profiles inside the cavity are presented. Comparisons are made with experimental unsteady pressure and PIV measurements. It was found that both DES and LES fare much better than URANS in resolving the higher frequencies and velocity distributions inside the cavity. Nomenclature A Cross-sectional area D Cavity depth dt CFD time-step h Height of control device L Cavity length LE Cavity leading-edge (lip) M Mach number Re Reynolds number, R e = U L ν SP L Sound Pressure Level T E Cavity trailing-edge (downstream corner) U Velocity W Cavity width w Width of control device x,y,z X-, y-and z-coordinates Subscripts ∞ Free-stream rms Root-mean square value j Jet

External flow velocity and synthetic jets parameters influence on cavity flow structure and acoustics characteristics using RANS/ILES

“…It was found that this method provides higher accuracy than DES method 9 for the grid with the same number of cells. Its accuracy is comparable with the results that were obtained using LES method, 9 whose number of cells was twice as many. In this paper the influence of SJs on the flow in the three-dimensional cavity of M219 was studied using RANS/ILES method.…”

“…Narrowband spectra are shown for cases, which have the greatest impact on the level of the peak values on the back wall of the cavity (see Figure 6). Analysis showed that spectra in the pairs of point (1,4), (2,5), (3,6) (7,9), and (8,10) are rather close, so results for most cases will be presented only for the points which are located in the section z ¼ 0. For M 0 ¼ 0.85 four jets before the cavity (case no.…”

“…Structured computational mesh consisted of 2.6 × 10 6 cells (3.4 × 10 5 in a cavity). It was found that this method provides higher accuracy than DES method 9 for the grid with the same number of cells. Its accuracy is comparable with the results that were obtained using LES method, 9 whose number of cells was twice as many.…”

Control of Supersonic Cavity Flow Using Plasma Actuators

“…In comparing the 2-D and 3-D resonance cases, it was consistently observed that 3-D excitation generated less broadband amplification than 2-D. This supports the attribution of the broadband reduction to the 3-D nature of excitation by the subsonic work [25,34]. Figure 13 shows 2-D and 3-D excitation spectral differences.…”

Control of High Subsonic Cavity Flow Using Plasma Actuators

“…The peak tone at the second Rossiter mode has decreased by almost 8 dB, and the average broadband spectra has decreased by roughly 3 dB. Because the forcing is not truly two-dimensional, it is believed that the broadband reduction is at least partially due to modest three-dimensionality imposed on the nominally two-dimensional cavity flow [41]. The presence of EMI makes the interpretation of the results more difficult, but it appears that forcing at this frequency induces some jitter in the second Rossiter mode, making it broader, and promotes amplification (though not significantly) of other modes.…”