History, review and summary of the cavity flow phenomena

This paper provides a detailed historical review of the cavity flow phenomena in fluid mechanics, from recorded studies in the late 19th century to more recent work. Research has been reviewed, independently and in culmination with other studies, to summarise the major and minor governing parameters of the flow. Outlined are influences of technology, regarding numerical models, experimental methods, analysis, and control techniques. All Mach regimes are assessed; low incompressible, sub-, trans-, super- and hypersonic where substantial research was available. A large variety of cavity geometry was presented, mostly rectangular, with more complex features akin to industry application, and where available, assessment of the boundary layer structure is also included. Conclusions on present understanding, and requirements for future work are given, with an aligned set of available data.

Cavity flow-field initialisation and development is dependent on; upstream (U/S) flow conditions of; airspeed $M_{\infty }$, boundary layer (BL) disturbance ($\delta$), displacement (${\delta }^{\ast }$) and momentum ($\theta$) thickness, either laminar or turbulent, and cavity geometry; length ($L$), depth ($D$) and width ($W$), with ratios $L/D,L/W,\delta /D$ and $L/\theta$ defining cavity response. I.e., a narrow cavity with a thin BL U/S tends toward a periodic 3D flow-field, with 3D effects and periodicity decreasing as $W$ and $\delta$ increase. Control is achievable through SL stabilisation via spanwise disturbance from the leading edge (LE), or thickening the BL, thus shear layer (SL). Experiments are preferred over numerical models, due to the inefficiency and high cost of required models (Colonius, 2001; Rowley and Williams, 2006; Lawson and Barakos, 2011). We understand effects of $L$, $D$, $L/D$, and $M_{\infty }$, thus future work should focus on $W$, BL and how they impact mode switching and stream/spanwise flow propagation. Also introducing more complex geometry, realistic to application, to observe additional 3D effects and U/S momentum change, in contribution to a scaling parameter and determination of criteria for activation of material displacement.