ProfilePicDr Tariq Saeed obtained both his MEng and PhD degrees in Aerospace Engineering from the University of Cambridge. His thesis was on the “Conceptual Design of a Laminar-Flying-Wing Aircraft”, which utilised surface suction as a form of laminar flow control. Here at Imperial College London, he is currently developing an experiment to investigate the transition process on a swept wing. This research aims to support and facilitate the theoretical investigations undertaken by  the LFC-UK  team.

Journal Articles

  • T.I. Saeed and W.R. Graham, Design Study for a Laminar-Flying-Wing Aircraft, Journal of Aircraft, 2015, Vol. 52, No. 5.
  • T.I. Saeed, W.R. Graham and C.A. Hall, Boundary-Layer Suction System Design for Laminar-Flying-Wing Aircraft, Journal of Aircraft, 2011, Vol. 48, No. 4.

Conference Presentations and Proceedings

  • T.I. Saeed, J.F. Morrison and M.S. Mughal, Roughness effects on swept-wing crossflow transition in moderate free-stream turbulence, 29th Congress of the International Council of the Aeronautical Sciences, St. Petersburg, Russia, 2014 (ICAS-2014-0542).
  • T.I. Saeed and J.F. Morrison, Experimental Investigation on the Effects of Free-Stream Turbulence on Swept-Wing Transition, 66th Annual Meeting of the APS Division of Fluid Mechanics, Pittsburgh, Pennsylvania, 2013.
  • T.I. Saeed and W.R. Graham, Conceptual Design for a Laminar Flying Wing Aircraft, 50th AIAA Aerospace Sciences and New Horizons Meeting, Nashville, Tennessee, 2012 (AIAA-2012-0868).
  • T.I. Saeed, W.R. Graham, H.Babinsky, J.P. Eastwood, C.A. Hall, J.P. Jarrett, M. Lone and K.A. Seffen,Boundary-Layer Suction System Design for Applivation to Laminar-Flying-Wing Aircraft, 28th Applied Aerodynamics Conference, Chicago, Illinois, 2010 (AIAA-2010-4379).
  • T.I. Saeed, W.R. Graham, H.Babinsky and C.A. Hall, Conceptual Design for a Laminar Flying Wing Aircraft, 27th Applied Aerodynamics Conference, San Antonio, Texas, 2009 (AIAA-2009-3616).

 Research Interests

Below is the Armstrong Whitworth AW-52 aircraft, an aircraft ahead of its time.  The wing profile was designed to maintain extensive regions of laminar flow; however, this was based on the understanding of transition at the time, which only  considered two dimensional T-S wave instabilities.  Its failure to achieve laminar flow was quickly establised by Gray in 1952 on conducting flight tests.  It revealed to the aerodynamic community that swept wings behave very differently to unswept ones, due to crossflow.  Questions that were asked back in the 1940s and 1950s are, to an extent, still being asked today; in fact the AW-52 is a source of inspiration for the two areas of research I have looked into thus far in my career. 


Experimental investigation of swept wing transition

Despite there being no shortage of publications on the topic of swept-wing transition, both experimentally and computationally, there is still considerable interest in the area. This in part is  driven by  the need for more efficient aircraft, which in turn demand more accurate transition prediction methods.  The eN method is the current  industry  standard, however its two obvious shortfalls are that  it  is: 1) unable to account for non-linearities in the flow, and 2) does not consider environmental disturbances.  There is therefore renewed interest in developing techniques that capture all the necessary physics of the problem, whilst also being accessible to real aircraft wing designers. These techniques still require further experimental verification.


There are four types of instability mechanisms that appear on swept wings: attachment-line, streamwise, centrifugal, and crossflow. The focus of this study is the crossflow instability.  Briefly, this instability arises due to a secondary, spanwise, flow in three-dimensional boundary layers, that is connected with the in-plane curvature of streamlines that develop due to the combined influences of sweep and pressure gradient. The crossflow velocity profile features an inflection point, which in turn leads to a basic instability mechanism that is inviscid. The physical manifestation of this instability is a spanwise array of co-rotating vortices, whose axis are aligned to within a few degrees of the local inviscid streamlines. Depending on environmental conditions, amplified disturbances appear as stationary as well as travelling waves.

Environmental disturbances feed into the boundary  layer through the receptivity process.  The literature details that in contrast to T-S instabilities, acoustic disturbances have almost no affect on the crossflow problem, whilst the effect of two-dimensional roughness is also weak.  However, stationary crossflows are particularly sensitive to three-dimensional surface irregularities e.g. isolated or even an array of spanwise roughness elements; whilst, travelling waves are sensitive to both roughness and free-stream turbulence.

Crossflow instability - [Bippes 1999]

Conceptual design of a laminar flying wing aircraft

The Greener by  Design initiative, a branch of the Royal Aeronautical Society, has identified the laminar-flying-wing configuration as the most promising long-term prospect for fuel-efficient civil aviation. However, in the absence of detailed evaluations, its potential remains uncertain. As an initial contribution, the work presented a point design study  for a specification chosen to maximize aerodynamic efficiency, via large wingspan and low sweepback. The resulting aircraft carries 220 passengers over a range of 9000km at Mach 0.67, and has a lift-to-drag ratio of 60.9, far in excess of conventional passenger transports. However, its overall effectiveness is compromised by a high empty-to-payload weight ratio and a poor engine efficiency in cruise. As a result, it has a much less marked fuel consumption advantage (11.9–13.9g per passenger km, compared to 14.6) over a conventional competitor designed, using the same methods, for the same mission. Both weight ratio and engine efficiency could be improved by moving to a low-aspect-ratio, delta-wing-like, planform, but at the cost of an aerodynamic efficiency penalty. This conflict, which h as no t previously been recognized, is inherent to the laminar-flying-wing concept, and is likely & ; ;nbs p;to undermine it s attractiveness. To find out more, take a look at my PhD thesis.