Nonlinear Analysis of Shear Coaxial Jets with Transverse Acoustic Forcing

2022 ◽  
Author(s):  
Anup Saha ◽  
Jonathan Crosmer ◽  
Harish Subramani ◽  
Gemunu H. Gunaratne ◽  
Sukesh Roy ◽  
...  
Keyword(s):  
Nonlinear Analysis ◽  
Coaxial Jets ◽  
Transverse Acoustic ◽  
Acoustic Forcing

Atomization of acoustically forced liquid sheets

2019 ◽  
Vol 880 ◽  
pp. 653-683 ◽  
Author(s):  
Sandip Dighe ◽  
Hrishikesh Gadgil
Keyword(s):  
Acoustic Field ◽  
Cutoff Frequency ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Liquid Sheets ◽  
Aerodynamic Interaction ◽  
Transverse Acoustic ◽  
External Acoustic Field ◽  
Acoustic Forcing ◽  
Sheet Breakup

Atomization of a smooth laminar liquid sheet produced by the oblique impingement of two liquid jets and subjected to transverse acoustic forcing in quiescent ambient is investigated. The acoustic forcing perturbs the liquid sheet perpendicular to its plane, thereby setting up a train of sinuous waves propagating radially outwards from the impingement point. These sheet undulations grow as the wave speed decreases towards the edge of the sheet and the sheet characteristics, like intact length and mean drop size, reduce drastically as compared to the natural breakup. Our observations show that the effect of the acoustic field is perceptible over a continuous range of forcing frequencies. Beyond a certain forcing frequency, called the cutoff frequency, the effect of the external acoustic field ceases. The cutoff frequency is found to be an increasing function of the Weber number. Our measurements of the characteristics of spatially amplifying sinuous waves show that the instabilities responsible for the natural sheet breakup augment in the presence of external forcing. Combining the experimental observations and measurements, we conclude that the linear theory of aerodynamic interaction (Squire’s theory) (Squire, Brit. J. Appl. Phys., vol. 4 (6), 1953, pp. 167–169) predicts the important features of this phenomenon reasonably well.

Asymmetric Transverse Acoustic Excitation of a Hollow Cone Spray Sheet With Air Swirl

2019 ◽  
Author(s):  
Rohit R. Bhattacharjee ◽  
Aravind I. Babu ◽  
Satyanarayanan R. Chakravarthy
Keyword(s):  
Cone Angle ◽  
Acoustic Excitation ◽  
Hollow Cone ◽  
Breakup Length ◽  
Swirl Angle ◽  
Transverse Acoustic ◽  
Spray Axis ◽  
Acoustic Forcing ◽  
Pressure Swirl ◽  
Hollow Cone Spray

Abstract The objective of this study was to experimentally observe the effects of externally perturbing a hollow cone spray sheet with acoustic excitation. These effects were quantified by measuring changes in the spray breakup length, swirl angle, and oscillatory behaviour of the sheet edge. We used a pressure swirl nozzle embedded into a swirler with 60° vane angles and a geometric swirl no. of SG = 0.981. Water was used to produce a hollow cone spray sheet and air was used as our swirler agent. For asymmetric forcing, only one side of the spray chamber was attached to a transverse duct (aligned perpendicular to the spray axis) along with two speakers. The duct harmonics were found to be 115 Hz, 204 Hz, and 313 Hz. Our experimental modes were also found to be comparable with results obtained numerically using the acoustic solver package from ANSYS. Our results show that for most cases the spray edges, cone angle, and breakup length responds to the acoustic forcing. While the cone angle increased with air swirl, for some cases without acoustic forcing the breakup length increased with air swirl.

Turbulent Nonpremixed Jet Flames under Transverse Acoustic Forcing

2020 ◽  
Author(s):  
Miguel A. Plascencia ◽  
Mario Roa ◽  
Ann R. Karagozian ◽  
Douglas G. Talley
Keyword(s):  
Jet Flames ◽  
Transverse Acoustic ◽  
Acoustic Forcing ◽  
Turbulent Nonpremixed

Dynamic-mode decomposition based analysis of shear coaxial jets with and without transverse acoustic driving

2016 ◽  
Vol 790 ◽  
pp. 5-32 ◽  
Author(s):  
Jia-Chen Hua ◽  
Gemunu H. Gunaratne ◽  
Douglas G. Talley ◽  
James R. Gord ◽  
Sukesh Roy
Keyword(s):  
Coherent Structures ◽  
Flux Ratio ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Oscillatory Behaviour ◽  
Natural Approach ◽  
Coaxial Jets ◽  
Mode Decomposition ◽  
Transverse Acoustic ◽  
Injector Flows

Modal decompositions of unperturbed and acoustically driven injector flows from shear coaxial jets are implemented using dynamic-mode decomposition, which is a natural approach in the search for collective oscillatory behaviour in nonlinear systems. Previous studies using proper orthogonal decomposition had revealed the most energetic pairs of coherent structures in injector flows. One of the difficulties in extracting lower-energy coherent structures follows from the need to differentiate robust flow constituents from noise and other irregular facets of a flow. The identification of robust features is critical for applications such as flow control as well, since only they can be used for the tasks. A dynamic-mode decomposition based algorithm for this differentiation is introduced and used to identify different classes of robust dynamic modes. They include (1) background modes located outside the injector flow that decay rapidly, (2) injector modes – including those presented in earlier studies – located in the vicinity of the flow, (3) modes that persist under acoustic driving, (4) modes responding linearly to the driving and, most interestingly, (5) a mode whose density exhibits antiphase oscillatory behaviour in the observation plane and that appears only when $J$, the outer-to-inner-jet momentum flux ratio, is sufficiently large; we infer that this is a projection of a mode rotating about the symmetry axis and born via a spontaneous symmetry breaking. Each of these classes of modes is analysed as $J$ is increased, and their consequences for the flow patterns are discussed.

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