Effects of nozzle exit boundary-layer conditions on excitability of heated free jets

AIAA Journal ◽  
1989 ◽  
Vol 27 (6) ◽  
pp. 712-718 ◽  
Author(s):  
J. Lepicovsky ◽  
W. H. Brown
Keyword(s):  
Boundary Layer ◽  
Nozzle Exit ◽  
Free Jets ◽  
Exit Boundary

scholarly journals An Experimental Investigation of Nozzle-Exit Boundary Layers of Highly Heated Free Jets

1992 ◽  
Vol 114 (2) ◽  
pp. 469-475
Author(s):  
J. Lepicovsky
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Boundary Layers ◽  
Laminar Boundary Layer ◽  
Nozzle Exit ◽  
Total Pressure ◽  
Free Jets ◽  
Exit Boundary ◽  
Mach Numbers

An experimental investigation of the effects of nozzle operating conditions on the development of nozzle-exit boundary layers of highly heated air free jets is reported in this paper. The total pressure measurements in the nozzle-exit boundary layer were obtained at a range of jet Mach numbers from 0.1 to 0.97 and jet total temperatures up to 900 K. The analysis of results shows that the nozzle-exit laminar boundary-layer development depends only on the nozzle-exit Reynolds number. For the nozzle-exit turbulent boundary layer, however, it appears that the effects of the jet total temperature on the boundary-layer integral characteristics are independent from the effect of the nozzle-exit Reynolds number. This surprising finding has not yet been reported. Further, laminar boundary-layer profiles were compared with the Pohlhausen solution for a flat-wall converging channel and an acceptable agreement was found only for low Reynolds numbers. For turbulent boundary layers, the dependence of the shape factor on relative Mach numbers at a distance of one momentum thickness from the nozzle wall resembles Spence’s prediction. Finally, the calculated total pressure loss coefficient was found to depend on the nozzle-exit Reynolds number for the laminar nozzle-exit boundary layer, while for the turbulent exit boundary layer this coefficient appears to be constant.

scholarly journals An Experimental Investigation of Nozzle-Exit Boundary Layers of Highly Heated Free Jets

1990 ◽  
Author(s):  
J. Lepicovsky
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Boundary Layers ◽  
Laminar Boundary Layer ◽  
Nozzle Exit ◽  
Total Pressure ◽  
Free Jets ◽  
Exit Boundary ◽  
Mach Numbers

An experimental investigation of the effects of nozzle operating conditions on the development of nozzle-exit boundary layers of highly heated air free jets is reported in this paper. The total pressure measurements in the nozzle-exit boundary layer were obtained at a range of jet Mach numbers from 0.1 to 0.97 and jet total temperatures up to 900 K. The analysis of results shows that the nozzle-exit laminar boundary-layer development depends only on the nozzle-exit Reynolds number. For the nozzle-exit turbulent boundary layer, however, it appears that the effects of the jet total temperature on the boundary-layer integral characteristics are independent from the effect of the nozzle-exit Reynolds number. This surprizing finding has not yet been reported. Further, laminar boundary-layer profiles were compared with the Pohlhausen solution for a flat-wall converging channel and an acceptable agreement was found only for low Reynolds numbers. For turbulent boundary layers, the dependence of the shape factor on relative Mach numbers at a distance of one momentum thickness from the nozzle wall resembles Spence’s prediction. Finally, the calculated total pressure loss coefficient was found to depend on the nozzle-exit Reynolds number for the laminar nozzle-exit boundary layer, while for the turbulent exit boundary layer this coefficient appears to be constant.

Nozzle-Exit Boundary-Layer Effects on a Controlled Supersonic Jet

AIAA Journal ◽  
2015 ◽  
Vol 53 (7) ◽  
pp. 2027-2039 ◽  
Author(s):  
Rachelle L. Speth ◽  
Datta V. Gaitonde
Keyword(s):  
Boundary Layer ◽  
Nozzle Exit ◽  
Supersonic Jet ◽  
Exit Boundary

Disturbance growth triggered by steady heating of a jet’s nozzle exit boundary layer

1995 ◽  
Vol 7 (10) ◽  
pp. 2304-2306 ◽  
Author(s):  
David Cornelius ◽  
Ganesh Raman
Keyword(s):  
Boundary Layer ◽  
Nozzle Exit ◽  
Exit Boundary ◽  
Disturbance Growth

scholarly journals Influence of nozzle-exit boundary-layer conditions on the flow and acoustic fields of initially laminar jets

2010 ◽  
Vol 663 ◽  
pp. 507-538 ◽  
Author(s):  
C. BOGEY ◽  
C. BAILLY
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Nozzle Exit ◽  
Initial Conditions ◽  
Frequency Noise ◽  
Noise Component ◽  
Potential Core ◽  
Velocity Fluctuations ◽  
Laminar Jets ◽  
Exit Boundary

Round jets originating from a pipe nozzle are computed by large-eddy simulations (LES) to investigate the effects of the nozzle-exit conditions on the flow and sound fields of initially laminar jets. The jets are at Mach number 0.9 and Reynolds number 105, and exhibit exit boundary layers characterized by Blasius velocity profiles, maximum root-mean-square (r.m.s.) axial velocity fluctuations between 0.2 and 1.9% of the jet velocity, and momentum thicknesses varying from 0.003 to 0.023 times the jet radius. The far-field noise is determined from the LES data on a cylindrical surface by solving the acoustic equations. Jets with a thinner boundary layer develop earlier but at a slower rate, yielding longer potential cores and lower centreline turbulent intensities. Adding random pressure disturbances of low magnitude in the nozzle also increases the potential core length and reduces peak r.m.s. radial velocity fluctuations in the shear layer. In all the jets, the shear-layer transition is dominated by vortex rolling-ups and pairings, which generate strong additional acoustic components, but also amplify the downstream-dominant low-frequency noise component when the exit boundary layer is thick. The introduction of inlet noise however results in weaker pairings, thus spectacularly reducing their contributions to the sound field. This high sensitivity to the initial conditions is in good agreement with experimental observations.

scholarly journals Importance of the nozzle-exit boundary-layer state in subsonic turbulent jets

2018 ◽  
Vol 851 ◽  
pp. 83-124 ◽  
Author(s):  
Guillaume A. Brès ◽  
Peter Jordan ◽  
Vincent Jaunet ◽  
Maxime Le Rallic ◽  
André V. G. Cavalieri ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nozzle Exit ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Turbulent Jets ◽  
Acoustic Energy ◽  
Frequency Noise ◽  
Mean Velocity ◽  
Radiated Noise ◽  
Exit Boundary

To investigate the effects of the nozzle-exit conditions on jet flow and sound fields, large-eddy simulations of an isothermal Mach 0.9 jet issued from a convergent-straight nozzle are performed at a diameter-based Reynolds number of $1\times 10^{6}$. The simulations feature near-wall adaptive mesh refinement, synthetic turbulence and wall modelling inside the nozzle. This leads to fully turbulent nozzle-exit boundary layers and results in significant improvements for the flow field and sound predictions compared with those obtained from the typical approach based on laminar flow in the nozzle. The far-field pressure spectra for the turbulent jet match companion experimental measurements, which use a boundary-layer trip to ensure a turbulent nozzle-exit boundary layer to within 0.5 dB for all relevant angles and frequencies. By contrast, the initially laminar jet results in greater high-frequency noise. For both initially laminar and turbulent jets, decomposition of the radiated noise into azimuthal Fourier modes is performed, and the results show similar azimuthal characteristics for the two jets. The axisymmetric mode is the dominant source of sound at the peak radiation angles and frequencies. The first three azimuthal modes recover more than 97 % of the total acoustic energy at these angles and more than 65 % (i.e. error less than 2 dB) for all angles. For the main azimuthal modes, linear stability analysis of the near-nozzle mean-velocity profiles is conducted in both jets. The analysis suggests that the differences in radiated noise between the initially laminar and turbulent jets are related to the differences in growth rate of the Kelvin–Helmholtz mode in the near-nozzle region.

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