A review of recent developments in flow control

Abstract

This paper reviews and highlights recent developments of certain aspects of flow control concerned with reducing the drag of, and delaying flow separation on, wings and bodies over which the flow is turbulent. The study is restricted to devices that extend beyond the viscous sub-layer but are on a smaller scale than geometric features of the aircraft (e.g. wing chord).The review is mainly concerned with developments within the UK, although significant developments in other countries are discussed.The review discusses types of flow that need to be controlled, basic features of flow control devices and applications. It concludes with recommendations for future research.

LES Study on Mechanism of Reduction of Shock Induced Flow Separation by MVG

“…In Lin's review [3] on the low-profile vortex generator, it was mentioned that MVG could alleviate the flow distortion in compact ducts to some extent and control boundary layer separation due to the adverse pressure gradients. Similar comments were made in the review by Ashill et al [4].…”

Review of research into shock control bumps

“…In recent years, as our knowledge of the (vortical) flow structures associated with 3-D SCBs has matured, researchers have begun to compare these devices with vortex generators. In one such study, Colliss et al [9] found that the strength of the vortices produced by a 3-D SCB is of the same order of magnitude as those of vortex generators (as reported by Ashill et al [1]), when expressed in terms of the non-dimensional circulation parameter /(u τ h) (where u τ is the local uncontrolled friction velocity and h is the SCB or vortex generator height). However, Colliss et al [9] also explain that quantifying the 'strength' of the vortices is not always trivial: as the existence of strong shear flows, in which the vortices are embedded, can make it difficult to extract the contribution to of the vortex itself.…”

“…Broadly speaking, a glance through the relevant literature from the past two decades reveals that studies of SCBs fall into one of the two categories: (1) Investigations that consist of parametric studies and/or optimisation; and (2) Investigations that probe the detailed flow physics produced by SCBs in controlled environments. In this review article, we will draw together the results from studies of both types.…”

“…Numerous review papers and research projects have made comparisons between SCBs and other (supersonic and transonic) flow control strategies [1,3,33]. A common conclusion amongst these studies and reviews is that 3-D SCBs offer a unique combination of promising performance potential (in terms of drag and/or buffet) and practicality (in terms of ease of installation, cost, weight, etc.)…”

“…The basic principle of shock control is well summarised by Ogawa and Babinsky [23], who explain that any flow control device that causes a flow deflection has the potential to reduce wave drag. However, although other (passive) shock-control techniques have been considered (such as the perforated surface cavity), it has been found that such techniques invariably incur prohibitively high levels of viscous drag which outweigh any wave drag benefit [1,33]. In recent years, as our knowledge of the (vortical) flow structures associated with 3-D SCBs has matured, researchers have begun to compare these devices with vortex generators.…”