Suppression of Cavity Oscillations via Three-Dimensional Steady Blowing

Abstract

This paper presents an investigation of open-loop control of cavity flow oscillations using a three-dimensional (3-D) array of steady jets located at the leading edge of the cavity. The actuation is introduced to suppress the fluctuating surface pressure in a rectangular cavity with a length-to-depth ratio (L/D) of 6 at Mach numbers from 0.3 to 0.7. Several different slot-jet configurations are assessed for their control performance considering the jet output momentum and interactions with the boundary layer at the leading edge. Significant tonal and broadband reductions of cavity oscillations are observed using 3-D actuation with wavelengths (λ/D) from 0.5 to 1 and with 25-50% spatial duty cycle. High speed (12 kHz) schlieren imaging and two-component and three-component stereoscopic Particle Image Velocimetry (PIV) are performed to investigate the baseline and controlled flow fields. Companion 3-D large eddy simulations (LES) are performed and exhibit good agreement with the experiments. The experiments and complementary LES reveal detailed flow physics. The 3-D actuation introduces strong spanwise wave-like structures which disrupt the growth of the shear layer and reduce the strength of fluctuating flow properties in the impingement region. The experimental and numerical analyses aid in the development of efficient control methodologies.

Effects of Sidewalls and Leading-Edge Blowing on Flows over Long Rectangular Cavities

“…The numerical results of the baseline flow at M ∞ = 0.6 and Re D = 10 4 have been compared to the results from the experiments at Re D = 3.3 × 10 5 . Good agreement is found concerning the properties of Rossiter modes as reported in the study by Zhang et al 33 (not shown here). Moreover, the time-averaged and Reynolds stress flow fields from the present work and the experiments exhibit qualitative agreement as shown in figure 2.…”

“…For spanwise-periodic case at M ∞ = 0.6, the dominant and subdominant Rossiter modes based on the measurement from the aft wall are modes II and I, respectively. This phenomenon is also observed in experimental work from Zhang et al 33 with a higher Reynolds number for M ∞ = 0.6 cavity flow. However, the peaks of these two modes are significantly suppressed in the finite-span case.…”

“…41,42 The initial boundary layer thickness δ 0 /D at the leading edge is set to 0.0167 based on our companion experiments. 33,34 No-slip and adiabatic conditions are specified at the floor and the cavity walls. Sponge zones are applied in the far-field and outflow regions spanning 2D from boundaries of the computational domain to damp out exiting wave structures.…”

“…We will also analyze the influence of active flow control through steady slotted-jets in addition to the sidewall effects on the flows. Active control of the cavity flows with slotted jets has been examined for the objective of reducing pressure fluctuations on the cavity surfaces in our companion experimental studies by Zhang et al, 33 George et al, 34 and Lusk et al 35 From their work, segmented jets are more effective to reduce flow oscillations compared to jets spanning the entire cavity width. Hence, we select effective slot configurations [33][34][35]44 and investigate the control effectiveness taking compressibility and sidewall influences into consideration.…”

“…The choice of control parameters are guided from experimental work. [33][34][35] The present numerical study will offer insights into how momentum injection influences the base flow and ultimately attenuates flow oscillations under different flow conditions. This paper is organized as follows.…”