Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session L5: Jets III: General |
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Chair: Sofia Larsson, Lulea University of Technology, Sweden Room: 104 |
Monday, November 23, 2015 4:05PM - 4:18PM |
L5.00001: Jet mixing in a down-scaled model of a rotary kiln Sofia Larsson, Simon Johansson Rotary kilns are large, cylindrical, rotating ovens with a burner in one end that are used in various industrial processes to heat up materials to high temperatures. Kiln burners are characterized by long diffusion flames where the combustion process is largely controlled by turbulent diffusion mixing between the burner fuel jet and the surrounding combustion air. The combustion air flow patterns have a significant effect on the mixing and hence the combustion efficiency and flame shape, motivating a systematic study of the kiln aerodynamics and the mixing characteristics. In this work, a downscaled, isothermal model of a rotary kiln is investigated experimentally through simultaneous particle image velocimetry and planar laser-induced fluorescence measurements. The kiln is modeled as a cylinder with three inlets in one end; two semicircular-shaped inlets for what is called the secondary fluid divided by a wall in between, called the back plate, where the burner nozzle is located. Three momentum flux ratios of the secondary fluid are investigated, and the interaction with the burner jet is scrutinized. It is found that the burner jet characteristics, its mixing with the secondary fluid and the resulting flow field surrounding the jet are dependent on the momentum flux ratio. [Preview Abstract] |
Monday, November 23, 2015 4:18PM - 4:31PM |
L5.00002: Stretched Inertial Jets Elisabeth Ghabache, Arnaud Antkowiak, Thomas Seon, Emmanuel Villermaux Liquid jets often arise as short-lived bursting liquid flows. Cavitation or impact-driven jets, bursting champagne bubbles, shaped-charge jets, ballistospores or drop-on-demand inkjet printing are a few examples where liquid jets are suddenly released. The trademark of all these discharge jets is the property of being stretched, due to the quenching injection. the present theoretical and experimental investigation, the structure of the jet flow field will be unraveled experimentally for a few emblematic occurrences of discharge jets. Though the injection markedly depends on each flow configuration, the jet velocity field will be shown to be systematically and rapidly attracted to the universal stretching flow z/t. The emergence of this inertial attractor actually only relies on simple kinematic ingredients, and as such is fairly generic. The universality of the jet velocity structure will be discussed. [Preview Abstract] |
Monday, November 23, 2015 4:31PM - 4:44PM |
L5.00003: On the local acceleration and flow trajectory of jet flows from circular and semi-circular pipes via 3D particle tracking velocimetry Jin-Tae Kim, Alex Liberzon, Leonardo P. Chamorro The distinctive differences between two jet flows that share the same hydraulic diameter $d_{h}=$ 0.01 m and \textit{Re }$\approx $ 6000, but different (nozzle) shape are explored via 3D Particle Tracking Velocimetry using OpenPTV (\underline {http://www.openptv.net}). The two jets are formed from circular and semicircular pipes and released in a quiescent water tank of 40 $d_{h}$ height, 40 $d_{h}$ wide, and 200 $d_{h}$ long. The recirculating system is seeded with 100 $\mu $m particles, where flow measurements are performed in the intermediate flow field (14.5 \textless $x/d_{h\thinspace }$\textless 18.5) at 550Hz for a total of $\approx $ 30,000 frames. Analysis is focused on the spatial distribution of the local flow acceleration and curvature of the Lagrangian trajectories. The velocity and acceleration of particles are estimated by low-pass filtering their position with a moving cubic spline fitting, while the curvature is obtained from the Frenet-Serret equations. Probability density functions (p.d.f.) of these quantities are obtained at various sub-volumes containing a given streamwise velocity range, and compared between the two cases to evaluate the memory effects in the intermediate flow field. [Preview Abstract] |
Monday, November 23, 2015 4:44PM - 4:57PM |
L5.00004: Experimental study of global oscillations in low density rectangular jets Rithwik N, Vinoth B. R The global oscillations of helium jets from rectangular nozzles are studied experimentally. The objectives of the work are: (i) study the effect of nozzle aspect ratio on global oscillations, (ii) study the effect of velocity profile which has continuously varying $Re_{h}$ and $\frac{h}{\theta}$ at the nozzle exit, on global oscillations, and (iii) control of global oscillations. The effect of aspect ratio ($AR$) of rectangular nozzle on the global oscillations is studied using three nozzles of $AR$ = 06, 12 and 20. The behavior of nozzles with $AR$ = 12 and $AR$ = 20 are found to be similar. Nozzles which have a varying height at the exit plane, are used to generate exit velocity profiles with continuously varying $Re_{h}$ and $\frac{h}{\theta}$ to study the role of $Re_{h}$ and $\frac{h}{\theta}$ on global oscillations of rectangular jets. It is found that the jets with the above velocity profile oscillates with single frequency. Circular wires are used to control the global oscillation of rectangular jets. The most sensitive region for rectangular jets with respect to suppression of global oscillations is found to be near the nozzle exit. But, the placement of wire at nozzle exit does not suppress the global oscillations. [Preview Abstract] |
Monday, November 23, 2015 4:57PM - 5:10PM |
L5.00005: High fidelity simulation of liquid jet in an excited crossflow Xiaoyi Li, Marios Soteriou Dynamic excitation of liquid jet in crossflow by externally oscillating the air stream has attracted much attention mainly due to its relevance to thermoacoustic instability mitigation. In this work, first principle high fidelity simulations of liquid jet atomization in an excited gaseous crossflow are performed using a dual-fluid Combined Level-Set and Volume Of Fluid (CLSVOF) interface capturing approach enhanced by a ghost fluid sharp interface treatment. Adaptive mesh refinement and Lagrangian algorithm for the smallest, spherical droplets are used to reduce the simulation cost. The simulations are validated against recently published experimental results. Mean features such as average jet penetration, volume flux and droplet size distribution and dynamic evolution of these quantities are studied. Proper Orthogonal Decomposition (POD) analyses of liquid surface features as well as detailed visualizations of the gaseous flow in the vicinity of the liquid column are performed. Detailed discussion of the impact of excitation on the physics of atomization is presented and the mechanisms by which excitation modifies the spray are identified. [Preview Abstract] |
Monday, November 23, 2015 5:10PM - 5:23PM |
L5.00006: Strain Rates and Scalar Dissipation Rates in Gaseous Transverse Jets Takeshi Shoji, Levon Gevorkyan, Andrea Besnard, Ann Karagozian This experimental study quantifies local strain rates and scalar dissipation rates for the non-reactive gaseous jet in crossflow (JICF) using simultaneous acetone planar laser-induced fluorescence (PLIF) imaging and stereo particle image velocimetry (PIV). Flush nozzle and flush pipe injectors are used to create jets consisting of mixtures of He and $\rm N_2$, with varying exit velocity profiles, jet-to-crossflow momentum flux ratios $J$, and density ratios $S$. Strain rates in the vicinity of windward and lee-side jet shear layers are quantified based both on scalar dissipation rates extracted from PLIF measurements within locally 1D layer-like structures and on vector fields extracted from PIV measurements. Strain rates from the simultaneous measurements are in very good qualitative agreement with one another on the jets' windward and lee sides, and are also consistent with flame ignition locations in comparable reactive JICF experiments. Quantitative differences in strain fields are most pronounced at lower $J$ values, corresponding to absolutely unstable shear layers and high local strain fields, although these differences are affected by the PLIF spatial resolution for a range of flow conditions. Extraction of dominant mode structures via POD will also be presented. [Preview Abstract] |
Monday, November 23, 2015 5:23PM - 5:36PM |
L5.00007: Rapid mixing of viscous liquids by electrical coiling Tiantian Kong, Jingmei Li, Zhou Liu, Liqiu Wang, Ho Cheung Shum We study the coiling of viscous liquid jets under an axial electric field. As a viscous jet accelerated by the electric field encounters a solid substrate, it is forced to decelerate, leading a compressive force that sets the jet to coil. We show that the coiling characteristics are significantly influenced by the applied electric force. Based on a balance between the electric and viscous torque, we deduce a scaling law to predict the coiling frequency from the relevant physical parameters, including the viscosity, dielectric constant, volumetric flow rate of the liquid and the applied electric field intensity. Moreover, we exploit this electrically controlled coiling to achieve rapid mixing between viscous liquids. We show that as a compound viscous jet is induced to coil electrically, the diffusion distance between viscous liquids is significantly reduced. As such, the mixing is enhanced remarkably despite the low Reynolds number, which is on the order of 10$^{-7}$. We further show that the degree of mixing can be precisely tuned by the applied electric force. Our approach of electric coiling offers a novel and versatile way to dispense, mix and print precursor liquids with large viscosities, including resins, food suspensions and polymer blends. [Preview Abstract] |
Monday, November 23, 2015 5:36PM - 5:49PM |
L5.00008: ABSTRACT MOVED TO KP2.036 |
Monday, November 23, 2015 5:49PM - 6:02PM |
L5.00009: Numerical and experimental study of the dynamics of a superheated jet Avick Sinha, Shivasubramanian Gopalakrishnan, Sridhar Balasubramanian Flash-boiling is a phenomenon where a liquid experiences low pressures in a system resulting in it getting superheated. The sudden drop in pressures results in accelerated expansion and violent vapour formation. Understanding the physics behind the jet disintegration and flash-boiling phenomenon is still an open problem, with applications in automotive and aerospace combustors. The behaviour of a flash-boiling jet is highly dependent on the input parameters, inlet temperature and pressure. In the present study, the external (outside nozzle) and the internal (inside nozzle) flow characteristics of the two-phase flow has been studied numerically and experimentally. The phase change from liquid to vapour takes place over a finite period of time, modeled sing Homogeneous Relaxation Model (HRM). In order to validate the numerical results, controlled experiments were performed. Optical diagnostic techniques such as Particle Image Velocimetry (PIV) and Shadowgraphy were used to study the flow characteristics. Spray angle, penetration depth, droplet spectra were obtained which provides a better understanding of the break-up mechanism. Linear stability analysis is performed to study the stability characteristics of the jet. [Preview Abstract] |
Monday, November 23, 2015 6:02PM - 6:15PM |
L5.00010: Effects of Annular and Rectangular Confinement on the Hydrodynamics of Reacting, Swirling Jets Benjamin Emerson, Tim Lieuwen In gas turbine combustors, flames are stabilized in the shear layers of swirling jets. In such devices, the flame's dynamics and its unsteady heat release are strongly governed by the fluid dynamics of the swirling jet flow. This unsteady heat release can couple with an acoustic mode of the combustor to cause a troublesome self-excited oscillation known as combustion instability. This coupling often occurs through the fluid dynamics, where the flame is dynamically wrinkled by acoustically excited vortical structures. This study uses linear stability analysis to study the effects of confinement on the fluid dynamics of reacting, swirling jets. Previous studies have explored confinement effects of an outer cylindrical wall. This study investigates other types of confinement. The analysis compares the classical arrangement, with flow through an outer cylindrical wall, to two other arrangements: flows through annular or rectangular confinements. The analysis shows that these confinement changes can have significant impacts on the instability growth rates, frequencies, and mode shapes. For example, changing a cylindrical confinement to a rectangular confinement tends to alter the hydrodynamic mode shape by straightening the nodal lines in the hydrodynamic velocity field. [Preview Abstract] |
Monday, November 23, 2015 6:15PM - 6:28PM |
L5.00011: Experimental observations of a complex, supersonic nozzle concept Andrew Magstadt, Matthew Berry, Mark Glauser, Christopher Ruscher, Sivaram Gogineni, Barry Kiel A complex nozzle concept, which fuses multiple canonical flows together, has been experimentally investigated via pressure, schlieren and PIV in the anechoic chamber at Syracuse University. Motivated by future engine designs of high-performance aircraft, the rectangular, supersonic jet under investigation has a single plane of symmetry, an additional shear layer (referred to as a wall jet) and an aft deck representative of airframe integration. Operating near a Reynolds number of $3 \times 10^6$, the nozzle architecture creates an intricate flow field comprised of high turbulence levels, shocks, shear \& boundary layers, and powerful corner vortices. Current data suggest that the wall jet, which is an order of magnitude less energetic than the core, has significant control authority over the acoustic power through some non-linear process. As sound is a direct product of turbulence, experimental and analytical efforts further explore this interesting phenomenon associated with the turbulent flow. [Preview Abstract] |
Monday, November 23, 2015 6:28PM - 6:41PM |
L5.00012: Advanced Supersonic Nozzle Concepts: Experimental Flow Visualization Results Paired With LES Matthew Berry, Andrew Magstadt, Cory Stack, Datta Gaitonde, Mark Glauser Advanced supersonic nozzle concepts are currently under investigation, utilizing multiple bypass streams and airframe integration to bolster performance and efficiency. This work focuses on the parametric study of a supersonic, multi-stream jet with aft deck. The single plane of symmetry, rectangular nozzle, displays very complex and unique flow characteristics. Flow visualization techniques in the form of PIV and schlieren capture flow features at various deck lengths and Mach numbers. LES is compared to the experimental results to both validate the computational model and identify limitations of the simulation. By comparing experimental results to LES, this study will help create a foundation of knowledge for advanced nozzle designs in future aircraft. [Preview Abstract] |
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