Dynamics of Three-Dimensional Shock-Wave/Boundary-Layer Interactions

Abstract

Advances in measuring and understanding separated, nominally two-dimensional (2D) shock-wave/turbulent-boundary-layer interactions (STBLI) have triggered recent campaigns focused on three-dimensional (3D) STBLI, which display far greater configuration diversity. Nonetheless, unifying properties emerge for semi-infinite interactions, taking the form of conical asymptotic behavior where shock-generator specifics become insignificant. The contrast between 2D and 3D separation is substantial; the skewed vortical structure of 3D STBLI reflects the essentially 2D influence of the boundary layer on the 3D character of the swept shock. As with 2D STBLI, conical interactions engender prominent spectral content below that of the turbulent boundary layer. However, the uniform separation length scale, which is crucial to normalizing the lowest-frequency dynamics in 2D STBLI, is absent. Comparatively, the spectra of 3D STBLI are more representative of the mid-frequency, convective, shear-layer dynamics in 2D, while phenomena associated with 2D separation-shock breathing are muted. Asymptotic behavior breaks down in many regions important to 3D-STBLI dynamics, occurring in a configuration-dependent manner. Aspects of inceptive regions near shock generators and symmetry planes are reviewed. Focused efforts toward 3D modal and nonmodal analyses, moving-shock/boundary-layer interactions, fluid/structure interactions, and flow control are suggested as directions for future work. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 55 is January 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

On wall pressure fluctuations in conical shock wave/turbulent boundary layer interaction

“…Several regions can be identified, which are characterized by different characteristic time scales. A region dominated by high-frequency motions, , corresponding to the incoming turbulent boundary layer, with a peak at associated with the energetic turbulent structures of the boundary layer (Gaitonde & Adler 2023). It should be emphasized that no significant energy was found in the range in the upstream boundary layer. The zone around the foot of the reflected shock, , which is characterized by strong low-frequency motions, especially near the separation point, and associated with flapping motion of the reflected shock system, similar to what is found in more canonical planar SBLIs (Dupont et al.…”

“…A region dominated by high-frequency motions, , corresponding to the incoming turbulent boundary layer, with a peak at associated with the energetic turbulent structures of the boundary layer (Gaitonde & Adler 2023). It should be emphasized that no significant energy was found in the range in the upstream boundary layer.…”

“…Shock wave/boundary layer interaction (SBLI) has been investigated widely in the past few decades; see e.g. the review papers of Dolling (2001), Smits & Dussauge (2006), Clemens & Narayanaswamy (2014) and Gaitonde & Adler (2023). Typically, SBLIs have a detrimental influence on the flow behaviour, causing unwanted effects such as strong pressure fluctuations, structural fatigue fracture, and severe structural vibrations associated with unsteady pressure loads, especially in the presence of separation bubbles (Dupont, Haddad & Debieve 2006;Piponniau et al 2009;Dupont, Piponniau & Dussauge 2019).…”

“…Cases under consideration cover a large range of geometric configurations, including impinging planar shocks (Dupont et al 2006;Robinet 2007;Humble et al 2009;Piponniau et al 2009;Pirozzoli & Bernardini 2011a;Touber & Sandham 2011;Sandham et al 2014;Pasquariello, Hickel & Adams 2017;Lusher & Sandham 2020), over-expanded nozzles (Martelli et al 2017), compression ramps (Adams 2000;Ganapathisubramani, Clemens & Dolling 2007;Wu & Martin 2008;Priebe & Martin 2012;Exposito, Gai & Neely 2021;Helm, Martin & Williams 2021) and transonic normal shock waves (Pirozzoli, Bernardini & Grasso 2010;Burton & Babinsky 2012;Sartor et al 2015;Karnick & Venkatraman 2017). Despite the efforts of the research community, the physical mechanisms involved in SBLIs are not yet completely understood, especially concerning the low-frequency unsteadiness associated with the separation shock, whose frequencies are approximately two orders of magnitude lower than those of the upstream boundary layer, and whose underlying cause is still debated (Priebe et al 2016;Adler & Gaitonde 2020;Ceci et al 2023;Gaitonde & Adler 2023).…”

On low-frequency unsteadiness in swept shock wave–boundary layer interactions

“…Low-frequency pressure fluctuations pose serious concerns to aircraft design, as they are prone to trigger fluid–structure interaction phenomena with potential structural damage. As a result, this phenomenon has been extensively studied, and is reviewed in several reference papers (Dolling 2001; Clemens & Narayanaswamy 2014; Gaitonde & Adler 2023).…”