Normal-Blowing Fluidic Thrust Vectoring for Supercritical Aft-deck Convergent-Divergent nozzles

  • Oluwatobi Afilaka

Student thesis: Phd


Thrust vectoring (TV) is the ability to manipulate the direction of thrust from a propulsive nozzle in order to provide forces and moments for control. Fluidic thrust vectoring (FTV) is based on the forced addition or removal of fluid from exhaust flow to control the deflection of that flow. The use of FTV compared to Mechanical TV reduces observability due to its vectoring functionality being achieved with a fixed geometry. The weight and manufacturing cost may also be reduced compared to equivalent MTV systems due to its simpler geometry. Normal-blowing FTV (NBFTV) utilises a secondary fluid injected normal to a convex curved surface (also called a reaction surface) in order to force the separation and subsequent vectoring of an attached jet. The aim of this thesis is to evaluate the performance of the NBFTV technique for aircraft pitch control. Performance is assessed as a measure of effectiveness (ability to produce large vectoring angles) and efficiency (the ratio of normal momentum out to secondary momentum in, referred to as system gain). The application of interest incorporates a fixed geometry convergent-divergent nozzle adjoined to an aft-deck, which is a rearward extension of the lower nozzle surface into a single convex curved surface. FTV system performance is sensitive to nozzle exit slot height to reaction surface (RS) radius ratio, and RS termination angle. An H/R of 0.2 and a RS termination angle of 30° were chosen to be representative of a practical nozzle configuration. Experiments were carried out using a symmetric nozzle with a uniform exit pressure profile, and a skewed nozzle with a non-uniform exit pressure profile matched to the RS curvature. Both nozzle profiles were designed for a Nozzle Pressure Ratio (NPR) of 3. Baseline experiments were carried out to determine how readily a jet issuing from both nozzle profiles would attach to the RS. The operational range of the NBFTV nozzle was then established by varying the injection point of the actuation along the streamwise direction of the RS with the injection hole spacing to diameter ratio (s/D) kept constant at 1.85. Subsequent experiments focused on determining the effect of s/D on the system performance at a given injection point. Experimental results demonstrate that for the same operating NPR and H/R the separation point of a skewed curved wall jet (CWJ) is always located downstream of that of a symmetric CWJ. As a result, the skewed nozzle generates normal force coefficients which are approximately 10% higher than that of a symmetric nozzle. It is shown that NBFTV is most effective at the overexpanded nozzle condition (NPR
Date of Award1 Aug 2019
Original languageEnglish
Awarding Institution
  • The University of Manchester
Supervisorwilliam crowther (Supervisor) & Katharine Smith (Supervisor)

Cite this