Towards Simultaneous High-Speed Mixture Fraction and Velocity Imaging in Turbulent Jets

2011 ◽  
Author(s):  
Randy Patton ◽  
Naibo Jiang ◽  
Walter Lempert ◽  
Jeffrey Sutton
Keyword(s):  
High Speed ◽  
Mixture Fraction ◽  
Turbulent Jets ◽  
Velocity Imaging

Large-scale structure and entrainment in the supersonic mixing layer

1995 ◽  
Vol 284 ◽  
pp. 171-216 ◽  
Author(s):  
N. T. Clemens ◽  
M. G. Mungal
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Large Scale ◽  
Mixture Fraction ◽  
Mixing Layer ◽  
Mie Scattering ◽  
Planar Laser ◽  
The Cross ◽  
Convective Mach Number ◽  
Stream Direction

Experiments were conducted in a two-stream planar mixing layer at convective Mach numbers,Mc, of 0.28, 0.42, 0.50, 0.62 and 0.79. Planar laser Mie scattering (PLMS) from a condensed alcohol fog and planar laser-induced fluorescence (PLIF) of nitric oxide were used for flow visualization in the side, plan and end views. The PLIF signals were also used to characterize the turbulent mixture fraction fluctuations.Visualizations using PLMS indicate a transition in the turbulent structure from quasi-two-dimensionality at low convective Mach number, to more random three-dimensionality for$M_c\geqslant 0.62$. A transition is also observed in the core and braid regions of the spanwise rollers as the convective Mach number increases from 0.28 to 0.62. A change in the entrainment mechanism with increasing compressibility is also indicated by signal intensity profiles and perspective views of the PLMS and PLIF images. These show that atMc= 0.28 the instantaneous mixture fraction field typically exhibits a gradient in the streamwise direction, but is more uniform in the cross-stream direction. AtMc= 0.62 and 0.79, however, the mixture fraction field is more streamwise uniform and with a gradient in the cross-stream direction. This change in the composition of the structures is indicative of different entrainment motions at the different compressibility conditions. The statistical results are consistent with the qualitative observations and suggest that compressibility acts to reduce the magnitude of the mixture fraction fluctuations, particularly on the high-speed edge of the layer.

Low-frequency sound sources in high-speed turbulent jets

2008 ◽  
Vol 617 ◽  
pp. 231-253 ◽  
Author(s):  
DANIEL J. BODONY ◽  
SANJIVA K. LELE
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Turbulent Jets ◽  
Acoustic Analogy ◽  
Sound Sources ◽  
Strongly Coupled ◽  
Eddy Simulation ◽  
Phase Cancellation ◽  
Jet Velocity ◽  
Two Jets

An analysis of the sound radiated by three turbulent, high-speed jets is conducted using Lighthill's acoustic analogy (Proc. R. Soc. Lond. A, vol. 211, 1952, p. 564). Computed by large eddy simulation the three jets operate at different conditions: a Mach 0.9 cold jet, a Mach 2.0 cold jet and a Mach 1.0 heated jet. The last two jets have the same jet velocity and differ only by temperature. None of the jets exhibit Mach wave characteristics. For these jets the comparison between the Lighthill-predicted sound and the directly computed sound is favourable for all jets and for the two angles (30° and 90°, measured from the downstream jet axis) considered. The momentum (ρuiuj) and the so-called entropy [p − p∞ − a∞2(ρ − ρ∞)] contributions are examined in the acoustic far field. It is found that significant phase cancellation exists between the momentum and entropy components. It is observed that for high-speed jets one cannot consider ρuiuj and (p′ − a∞2ρ′)δij as independent sources. In particular the ρ′ūxūx component of ρuiuj is strongly coupled with the entropy term as a consequence of compressibility and the high jet velocity and not because of a linear sound-generation mechanism. Further, in more usefully decoupling the momentum and entropic contributions, the decomposition of Tij due to Lilley (Tech. Rep. AGARD CP-131 1974) is preferred. Connections are made between the present results and the quieting of high-speed jets with heating.

scholarly journals High-speed mixture fraction and temperature imaging of pulsed, turbulent fuel jets auto-igniting in high-temperature, vitiated co-flows

2014 ◽  
Vol 55 (7) ◽  
Author(s):  
Michael J. Papageorge ◽  
Christoph Arndt ◽  
Frederik Fuest ◽  
Wolfgang Meier ◽  
Jeffrey A. Sutton
Keyword(s):  
High Temperature ◽  
High Speed ◽  
Mixture Fraction ◽  
Temperature Imaging

scholarly journals Simultaneous temperature, mixture fraction and velocity imaging in turbulent flows using thermographic phosphor tracer particles

2012 ◽  
Vol 20 (20) ◽  
pp. 22118 ◽  
Author(s):  
Benoit Fond ◽  
Christopher Abram ◽  
Andrew L Heyes ◽  
Andreas M Kempf ◽  
Frank Beyrau
Keyword(s):  
Turbulent Flows ◽  
Mixture Fraction ◽  
Velocity Imaging ◽  
Tracer Particles ◽  
Thermographic Phosphor

Ultra-fast velocity imaging in stenotically produced turbulent jets using RUFIS

1998 ◽  
Vol 39 (4) ◽  
pp. 574-580 ◽  
Author(s):  
David P. Madio ◽  
H. Michael Gach ◽  
Irving J. Lowe
Keyword(s):  
Turbulent Jets ◽  
Velocity Imaging

Compressibility effects in a turbulent annular mixing layer. Part 2. Mixing of a passive scalar

2000 ◽  
Vol 421 ◽  
pp. 269-292 ◽  
Author(s):  
JONATHAN B. FREUND ◽  
PARVIZ MOIN ◽  
SANJIVA K. LELE
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Mixture Fraction ◽  
Mixing Layer ◽  
Passive Scalar ◽  
Momentum Equation ◽  
Mixing Efficiency ◽  
Scalar Flux ◽  
Mach Numbers ◽  
Highly Correlated

The mixing of fuel and oxidizer in a mixing layer between high-speed streams is important in many applications, especially air-breathing propulsion systems. The details of this process in a turbulent annular mixing layer are studied with direct numerical simulation. Convective Mach numbers of the simulations range from Mc = 0.1 to Mc = 1.8. Visualizations of the scalar field show that at low Mach numbers large intrusions of nearly pure ambient or core fluid span the mixing region, whereas at higher Mach numbers these intrusions are suppressed. Increasing the Mach number is found to change the mixture fraction probability density function from non-marching to marching and the mixing efficiency from 0.5 at Mc = 0.1 to 0.67 at Mc = 1.5. Scalar concentration fluctuations and the axial velocity fluctuations become highly correlated as the Mach number increases and a suppressed role of pressure in the axial momentum equation is found to be responsible for this. Anisotropy of scalar flux increases with Mc, and is explained via the suppression of transverse turbulence lengthscale.

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