Coherent Structures in a Channel with Groyne Fields: A Numerical Investigation Using LES

2005 ◽  
Author(s):  
Andrew McCoy ◽  
George Constantinescu ◽  
Larry Weber
Keyword(s):  
Numerical Investigation ◽  
Coherent Structures

Numerical Investigation of the Coherent Structures and Sound Properties in Sonic Coaxial Jets

2017 ◽  
Vol 9 (3) ◽  
pp. 554-573
Author(s):  
Haitao Shi ◽  
Dawei Chen ◽  
Pei Wang ◽  
Nansheng Liu ◽  
Xiyun Lu
Keyword(s):  
Numerical Investigation ◽  
Coherent Structures ◽  
High Frequency ◽  
Sound Production ◽  
Recirculation Zone ◽  
Decomposition Analysis ◽  
Coaxial Jets ◽  
Secondary Shock ◽  
Eddy Simulation ◽  
Annular Jet

AbstractNumerical investigation of the underexpanded sonic coaxial jets is carried out using large eddy simulation for three typical inner nozzle lip-thicknesses. Various fundamental mechanisms dictating the flow phenomena including shock structure, shear layer evolution and sound production are investigated. It is found that the inner nozzle lip induces a recirculation zone between inner and outer jets, which significantly influences the behaviors of shock structures and shear layers. The sound properties of the coaxial jets are further analyzed in detail. As the inner lip-thickness increases, the helical screech mode switches to an axisymmetric one and high-frequency screech also occurs with an oscillation frequency of recirculation zone. Based on the temporal Fourier transform and correlation analysis, the primary sources of low- and high-frequency screeches are associated with the downstream shock cells in the jet column and the secondary shock structures in the outer annular jet, respectively. The proper orthogonal decomposition analysis reveals that the dominant structures constructed by the most energetic modes shift from the downstream shock cells region to the upstream secondary shock region as the lip-thickness increases. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the coherent structures and sound properties in sonic coaxial jets.

scholarly journals Numerical investigation of a jet from a blunt body opposing a supersonic flow

2011 ◽  
Vol 684 ◽  
pp. 85-110 ◽  
Author(s):  
Li-Wei Chen ◽  
Guo-Lei Wang ◽  
Xi-Yun Lu
Keyword(s):  
Supersonic Flow ◽  
Shear Layer ◽  
Numerical Investigation ◽  
Coherent Structures ◽  
Blunt Body ◽  
Free Stream ◽  
Mach Disk ◽  
Recirculation Region ◽  
Small Scale ◽  
Flow States

AbstractNumerical investigation of a sonic jet from a blunt body opposing a supersonic flow with a free stream Mach number ${M}_{\infty } = 2. 5$ was carried out using large-eddy simulation for two total pressure ratios of the jet to the free stream, i.e. $\mathscr{P}= 0. 816$ and 1.633. Results have been validated carefully against experimental data. Various fundamental mechanisms dictating the flow phenomena, including shock/jet interaction, shock/shear-layer interaction, turbulent shear-layer evolution and coherent structures, have been studied systematically. Based on the analysis of the flow structures and features, two typical flow states, i.e. unstable and stable states corresponding to the two values of $\mathscr{P}$, are identified and the behaviours relevant to the flow states are discussed. Small-scale vortical structures mainly occur in the jet column, and large-scale vortices develop gradually in a recirculation region when the jet terminates through a Mach disk and reverses its orientation as a conical free shear layer. The turbulent fluctuations are enhanced by the rapid deviation of the shear layer and the interaction with shock waves. Moreover, the coherent structures of the flow motion are analysed using the proper orthogonal decomposition technique. It is found that the dominant mode in the cross-section plane exhibits an antisymmetric character for the unstable state and an axisymmetric one for the stable state, while statistical analysis of unsteady loads indicates that the side loads can be seen as a rotating vector uniformly distributed in the azimuthal direction. Further, we clarify a feedback mechanism whereby the unsteady motion is sustained by the upstream-propagating disturbance to the Mach disk through the recirculation subsonic region and downstream propagation in the conical shear layer. Feedback models are then proposed which can reasonably well predict the dominant frequencies of the two flow states. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the opposing jet/supersonic flow interaction.

Numerical investigation of turbulent flow coherent structures in annular jet pumps using the LES method

2017 ◽  
Vol 61 (1) ◽  
pp. 86-97 ◽  
Author(s):  
MaoSen Xu ◽  
XueLong Yang ◽  
XinPing Long ◽  
Qiao Lyu ◽  
Bin Ji
Keyword(s):  
Turbulent Flow ◽  
Numerical Investigation ◽  
Coherent Structures ◽  
Annular Jet ◽  
Jet Pumps
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