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Newsletter  2019.2  Index

Theme : "Mechanical Engineering Congress, 2018 Japan (MECJ-18)"

  1. Preface
    Masaaki MOTOZAWA, Sadao KUROSAWA
  2. Biomimetic consideration of means to catch fluid forces
    Yoshihiro KUBOTA, Osamu MOCHIZUKI (Toyo University)
  3. Technical Section on Plasma Actuators - Activities in the Past 5 Years and Future Prospects -
    Takehiko SEGAWA (National Institute of Advanced Industrial Science and Technology), Koji FUKAGATA (Keio University), Takashi MATSUNO (Tottori University), Taku NONOMURA (Tohoku University), Naofumi OHNISHI (Tohoku University)
  4. Study of Flow Control by Trial and Error Learning Approach
    Hitoshi ISHIKAWA (Tokyo University of Science)
  5. Thrust Vector Control of Transonic and Supersonic Under-Expanded Jets
    Toshihiko SHAKOUCHI (Mie University)
  6. Active Boundary Layer Control by Jets in a Crossflow
    Hiroaki HASEGAWA (Utsunomiya University)
  7. Micro-tomographic Visualization of Capillary Blood Flow Velocity using Multi-Functional Optical Coherence Tomography
    Souichi SAEKI, Daisuke FURUKAWA (Osaka City University), Takafumi ITO, Yoshiaki NISHINO (Takaoka Toko Co., Ltd.)
  8. Application of multi-functional OCT to diagnose skin mechanics ~Visualization of skin vasculature~ 
    Yusuke HARA (Shiseido Global Innovation Center), Souichi SAEKI (Osaka City University)


Thrust Vector Control of Transonic and Supersonic Under-Expanded Jets

Toshihiko SHAKOUCHI,
Tsubasa TANOUE,
Toshitake ANDO,
Mie University



Sub- and supersonic jet flows are used to gain thrust in jet or rocket engine and the thrust vector control is one of the important function. The thrust vector of jet or rocket engine is controlled to change the flying direction by a complex mechanical system usually (1)~(4). In this study, a simple method of thrust vector control of sub- and super-sonic jets by an expanded Coanda nozzle, CC-nozzle, attached to the tip of the pipe nozzle, Pi-nozzle (Fig.1(a), supplied air pressure: P0 = 0.38 MPa) is shown. The inlet diameter, 6.0 mm, of the CC-nozzle is larger than the Pi-nozzle of 3.7 mm, and shifting CC-nozzle in the radius direction to be zero offset distance (Fig.1(b), A-side, Eccentric nozzle array) the jet from Pi-nozzle deflects and attaches to the wall of CC-nozzle by Coanda effect (Fig.2(c), Deflection jet, deflection angle: β = 6˚). In the concentric array (Fig.1(a)), there was so-called bi-stable state in which the jet from the Pi-nozzle flowed straight (Fig.2(a), Straight jet) and enlarged throughout the CC-nozzle (Fig.2(b), Expansion jet). The jet centerline velocity uc issued from

Pi-nozzle gradually decreases after repeating decrease and increase following flow expansion and compression (Fig.3), and the St-jet is smaller than the Pi-jet because of the flow resistance of the CC-nozzle. uc of the Exp-jet is much smaller than the others (Figs.3,4). The thrust F was calculated approximately by the velocity distribution, u (Fig.4), just after the nozzle exit. The thrust of the Deflection jet is the maximum and it is about 1.4 times of the Straight jet. In this study, a simple thrust vectoring method of supersonic jet by shifting the Coanda nozzle was shown. Now, a fluidic thrust vectoring without moving parts is under consideration.

Key words

 Sub- and super-sonic jets, Under-expanded jet, Vector control, Thrust, Coanda effect


(a) Concentric arrangement  (b) Eccentric arrangement
Fig.1 Arrangement of Pipe and Coanda nozzles
(a) Straight jet (concentric nozzle array) (b) Expansion jet (concentric nozzle array)
(c) Deflection jet (eccentric nozzle array, β =6˚)  
Fig.2 Visualized flow pattern by Schlieren image (α=10°, P0=0.380[MPa])
There are expansion and compression shock waves in the flow pattern.
Fig.3 Centerline velocity distribution, uc
(α =10˚, P0= 0.380 MPa)
Fig.4 Velocity distribution at the cross section
(CC-nozzle, α =10°, P0= 0.380 MPa)

Fig.5 Total thrust at the nozzle exit ( x =17 [mm])


(1) Zaman, K.B.M.Q., Spreading characteristics of compressible jets from nozzles of various geometries, J. of Fluid Mech., Vol.383 (1999), pp.197-228.
(2) Trancossi, M. and Dumas, A., Coanda synthetic jet deflection apparatus and control, SAE International, 2011-01-2590 (2011).
(3) Allen, D.S., Axisymmetric Coanda-assisited vectoring, Master’s thesis of Utah State Univ., (2008).
(4) Mason, M.S. and Crowther, W.J., Fluidic thrust vectoring of low observable aircraft, Proc. of CEAS Aerospace Aero- dynamic Research Conf., (2002, Cambridge, UK).
Last Update:2.22.2019