The present contribution addresses the possibility of extracting more jet noise suppression capabilities of stationary chevron nozzle exits through unsteady excitation of secondary instabilities. An example of insertion of steady streamwise vorticity into a mixing region is given to illustrate its effectiveness in promoting enhanced mixing. Using stability theory as a guide, unsteady secondary instability of the streamwise vorticity is excited with emphasis on nonlinear effects. The averaged combined effect on the steady flow, through the Reynolds stresses, provides significant further enhancement. Possible implementation in the laboratory is discussed as is further extensions of the much-simplified considerations.
LiuJTC. Developing large-scale wavelike eddies and the near jet noise field. J Fluid Mech1974; 62: 437–464.
2.
Lee-Or Merkine JTC and Liu JTC (1975) On the development of noise-producing large-scale wavelike eddies in a plane turbulent jet. J Fluid Mech 1975; 70: 353–368.
3.
LassiterLWHubbardH. The near noise field of static jets and some model studies for noise reduction. NACA TN 5187,1954.
4.
Mollo-ChristensenE. Jet noise and shear flow instability seen from an experimenter’s viewpoint. J Appl Mech1967; 34: 1–7.
5.
LandahlMTMollo-ChristensenE. Turbulence and random processes in fluid mechanics, 2nd ed. Cambridge, UK: Cambridge University Press, 1994, pp. 132–140.
6.
MankbadiRLiuJTC. Sound generated aerodynamically revisited: large-scale structures in a turbulent jet as a source of sound. Philos Trans R Soc1984; A311: 183–217.
7.
Zaman KBMQ. Streamwise vorticity generation and mixing enhancement in free jets by ‘delta-tabs'. In: AIAA shear flow conference, AlAA 93-3253 (NASA TM 106235), 6–9 July 1993, Orlando, FL, USA.
8.
Zaman KBMQ, Bridges JE and Huff DL. Evolution from ‘tabs’ to ‘Chevron technology’—a review. In: Proceedings of the 13th Asian congress of fluid mechanics, Dhaka, Bangladesh, 17–21 December 2010, pp.47–63.
GirgisIGLiuJTC. Mixing enhancement via the release of strongly nonlinear longitudinal Gortler vortices and their secondary instabilities into the mixing region. J Fluid Mech2002; 468: 29–75.
11.
LiuJTC. An extended Reynolds analogy for excited wavy instabilities of developing streamwise vortices with applications to scalar mixing intensification. Proc R Soc2007; A463: 1791–1813.
12.
FloryanJMSaricWS. Stability of Gortler vortices in boundary layers. AIAA J1982; 20: 316–324.
13.
StuartJT. On the role of Reynolds stress in stability theory. J Aeronaut Sci1956; 23: 86–88.
14.
StuartJT. On the effect of Reynolds stress on hydrodynamic stability. Z Angew Math Mech1956; 36: S32–S38.
15.
SabryASLiuJTC. Longitudinal vorticity elements in boundary layers: nonlinear development from initial Gortler vortices as a prototype problem. J Fluid Mech1991; 231: 615–663.
16.
LeeKLiuJTC. On the growth of mushroom like structures in nonlinear spatially developing Gortler vortex flow. Phys Fluids1992; A4: 95–103.
17.
AsaiMMinagawaMNishiokaM. The Instability and breakdown of a near-wall low-speed streak. J Fluid Mech2002; 455: 289–314.
18.
YuXLiuJTC. The secondary instability of Gortler flow. Phys Fluids1991; A3: 1845–1847.
19.
YuXLiuJTC. On the mechanism of sinuous and varicose modes in three-dimensional viscous instability of Gortler rolls. Phys Fluids1994; 6: 736–750.
20.
MeksynDStuartJT. Stability of viscous motion between parallel planes for finite disturbances. Proc R Soc1951; A208: 517–526.
21.
Malatesta V, Souza LF, Liu JTC, et al. Heat transfer analysis in a flow over concave wall with primary and secondary instabilities. In: Proceedings IUTAM ABCM symposium on laminar turbulent transition, Rio de Janerio, Brazil, 8–12 September 2014.
22.
LiuJTC. An extended Reynolds analogy for excited wavy instabilities of developing streamwise vortices with applications to scalar mixing intensification. Proc R Soc2007; A463: 1791–1813.
23.
TsuiYYWuPW. Investigation of the mixing flow structure in multilobe mixers. AIAA J1966; 34: 1386–1391.
24.
SwearngenJDBlackwelderRF. The growth and breakdown of streamwise vortices in the presence of a wall. J Fluid Mech1987; 182: 255–290.
25.
DoerrPCKlockerMJ. Numerical investigation of plasma actuator force-term estimations from flow experiments. J. Phys. D: Appl. Phys2015; 48: 395203, .
