scholarly journals Numerical Investigation of Swirling Hydrogen Flames: Effect of Swirl and Fuel Jet in Coherent Structures

2016 ◽  
Vol 1 ◽  
pp. 19-33
Author(s):  
V. Suresh Balaji ◽  
Ashoke De ◽  
Santanu De
Keyword(s):  
Numerical Investigation ◽  
Coherent Structures ◽  
Fuel Jet

Modal Analysis of Breakup Mechanisms for a Liquid Jet in Crossflow

2021 ◽  
pp. 1-36
Author(s):  
Sheikh Salauddin ◽  
Wilmer Flores ◽  
Michelle Otero ◽  
Bernhard Stiehl ◽  
Kareem Ahmed
Keyword(s):  
Coherent Structures ◽  
Liquid Fuel ◽  
Hydrodynamic Instability ◽  
Aviation Industry ◽  
Dynamic Mode ◽  
Capillary Breakup ◽  
Breakup Mechanism ◽  
Jet In Crossflow ◽  
Fuel Jet ◽  
Primary Breakup

Abstract Liquid fuel jet in Crossflow (LJIC) is a vital atomization technique significant to the aviation industry. The hydrodynamic instability mechanisms that drive a primary breakup of a transverse jet are investigated using modal and traveling wavelength analysis. This study highlights the primary breakup mechanisms for aviation fuel Jet-A, utilizing a method that could be applied to any liquid fuel. Mathematical decomposition techniques known as POD (Proper Orthogonal Decomposition) and Robust MrDMD (Multi-Resolution Dynamic Mode Decomposition) are used together to identify dominant instability flow dynamics associated with the primary breakup mechanism. Implementation of the Robust MrDMD method deconstructs the nonlinear dynamical systems into multiresolution time-scaled components to capture the intermittent coherent structures. The Robust MrDMD, in conjunction with the POD method, is applied to data points taken across the entire spray breakup regimes: enhanced capillary breakup, bag breakup, multimode breakup, and shear breakup. The dominant frequencies of breakup mechanisms are extracted and identified. These coherent structures are classified with an associated time scale and Strouhal number. Three primary breakup mechanisms, namely ligament shedding, bag breakup, and shear breakup, were identified and associated with the four breakup regimes outlined above. Further investigation portrays these breakup mechanisms to occur in conjunction with each other in each breakup regime, excluding the low Weber number Enhanced Capillary Breakup regime. Spectral analysis of the Robust MrDMD modes' entire temporal window reveals that while multiple breakup mechanisms are convolved, there is a dominant breakup route for each breakup regime. An associated particular traveling wavelength analysis further investigates each breakup mechanism. Lastly, this study explores the effects of an increased momentum flux ratio on each breakup mechanism associated with a breakup regime.

Localized Breakup Instabilities for a Liquid Jet in Crossflow

2021 ◽  
Author(s):  
Sheikh Salauddin ◽  
Wilmer Flores ◽  
Michelle Otero ◽  
Kareem Ahmed
Keyword(s):  
Coherent Structures ◽  
Hydrodynamic Instability ◽  
Aviation Industry ◽  
Small Scale ◽  
Dynamic Mode ◽  
Capillary Breakup ◽  
Jet In Crossflow ◽  
Fuel Jet ◽  
Primary Breakup ◽  
Scale Surface

Abstract Liquid fuel jet in Crossflow (LJIC) is significant to the aviation industry since it is a vital technique for atomization. The hydrodynamic instability mechanisms that drive a transverse jet’s primary breakup were investigated using modal and traveling wavelength analysis. This study highlights the primary breakup mechanisms for aviation fuel Jet-A. However, the techniques discussed are applicable to any liquid. Mathematical decomposition techniques are known as POD (Proper Orthogonal Decomposition), and MrDMD (Multi-Resolution Dynamic Mode Decomposition) are used together to identify dominant instability flow dynamics associated with the primary breakup mechanism. Implementation of the MrDMD method deconstructs the nonlinear dynamical systems into multiresolution time-scaled components that capture the intermittent coherent structures. The MrDMD, in conjunction with the POD method, is applied to data points taken across the entire spray breakup regimes, which are: enhanced capillary breakup, bag breakup, multimode breakup, and shear breakup. The dominant frequencies of both breakup regimes are extracted and identified. These coherent structures are classified with an associated time scale and Strouhal number. Characterization of the traveling column and surface wavelengths are conducted and associated with a known instability model. It is found that the Plateau-Rayleigh instability model predicts columns wavelengths similar to wavelengths found in dominant modes associated with a capillary breakup. Rayleigh Taylor’s instability model matches well with bag and multimode breakup. Small scale surface wavelengths associated with a shear breakup are correlated to a modified Rayleigh Taylor instability model founded by Wang et al. [1]. Furthermore, an atomization model that predicts the Sauter Mean Diameter associated with the dominant small-scale surface traveling wavelengths is established.

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.

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