LES Simulation of the Internal Flow and Near-Field Spray Structure of an Outward-Opening GDi Injector and Comparison with Imaging Data

2008 ◽  
Author(s):  
B. Befrui ◽  
G. Corbinelli ◽  
D. Robart ◽  
W. Reckers ◽  
H. Weller
Keyword(s):  
Near Field ◽  
Internal Flow ◽  
Imaging Data ◽  
Spray Structure

Characteristics of Nozzle Internal Flow and Near-Field Spray of Multi-Hole Injectors for Diesel Engines

2015 ◽  
Author(s):  
Pengbo Dong ◽  
Takuya Inaba ◽  
Keiya Nishida ◽  
Youichi Ogata ◽  
Daisuke Shimo ◽  
...  
Keyword(s):  
Diesel Engines ◽  
Near Field ◽  
Internal Flow

PREDICTION OF NOISE GENERATED BY A ROUND NOZZLE JET FLOW USING COMPUTATIONAL AEROACOUSTICS

2011 ◽  
Vol 19 (03) ◽  
pp. 291-316 ◽  
Author(s):  
ALI UZUN ◽  
M. YOUSUFF HUSSAINI
Keyword(s):  
Flow Field ◽  
Near Field ◽  
Internal Flow ◽  
Jet Flow ◽  
Computational Aeroacoustics ◽  
Far Field ◽  
Free Jet ◽  
Grid Points ◽  
Field Noise ◽  
Inflow Conditions

This paper demonstrates an application of computational aeroacoustics to the prediction of noise generated by a round nozzle jet flow. In this study, the nozzle internal flow and the free jet flow outside are computed simultaneously by a high-order accurate, multi-block, large-eddy simulation (LES) code with overset grid capability. To simulate the jet flow field and its radiated noise, we solve the governing equations on approximately 370 million grid points using high-fidelity numerical schemes developed for computational aeroacoustics. Projection of the near-field noise to the far-field is accomplished by coupling the LES data with the Ffowcs Williams–Hawkings method. The main emphasis of these simulations is to compute the jet flow in sufficient detail to accurately capture the physical processes that lead to noise generation. Two separate simulations are performed using turbulent and laminar inflow conditions at the jet nozzle inlet. Simulation results are compared with the corresponding experimental measurements. Results show that nozzle inflow conditions have an influence on the jet flow field and far-field noise.

Local, Near-Field Mixing Augmentation Using Square Coaxial Jets

2004 ◽  
Author(s):  
Samuel Bonnafous ◽  
Victor Piffaut ◽  
Wai-Ho Choy ◽  
Dimitris E. Nikitopoulos
Keyword(s):  
Near Field ◽  
Internal Flow ◽  
Spreading Rate ◽  
Central Plane ◽  
Mean Velocity ◽  
Mixing Rates ◽  
Spreading Rates ◽  
Diagonal Plane ◽  
Axis Switching ◽  
First Time

Results from un-forced experiments in flows ensuing from circular and equivalent square coaxial nozzles with parallel sides are presented in this paper. The nozzles are contoured and are designed so that the hydraulic diameters of the internal flow passages are identical for both geometries. The flow experiments were conducted at a co-flow-jet Reynolds number of Re = 16,000 and inner-to-outer jet nominal velocity ratios of λ = 0, 0.5, 1.5. Axis switching, a phenomenon readily observed in single non-axisymmetric nozzles, is shown for the first time to occur in the square coaxial nozzles as well. Comparisons of the mixing regions of the flows from both geometries are made to examine mixing advantages when using square nozzle configurations. Comparisons of stream wise mean velocity fields measured on a center plane parallel to the square nozzle sides, on a diagonal plane of the square nozzle and the center plane of the corresponding circular nozzle, are presented and discussed. Axis switching is shown to be evident in the near-field shear regions for all velocity ratios, resulting in considerable mixing advantages. The spreading rates (and therefore mixing rates) of the outer mixing region of the square nozzles clearly exceed the spreading rate observed in the circular case on the central plane. Axis switching and improved mixing is also observed in the inner mixing region of the square nozzle. This work is relevant to coaxial nozzles for gas turbine combustor applications, although the study has been carried out in a scaled up geometry with respect to this application.

scholarly journals Multivariate Analysis Applied to Polymer Imaging Data Obtained by Near-Field Infrared Microscopy

2017 ◽  
Vol 15 (0) ◽  
pp. 19-24 ◽  
Author(s):  
Takayuki Yamagishi ◽  
Kenta Honobe ◽  
Satoka Aoyagi ◽  
Mayumi Okawa ◽  
Tomoko Kawashima
Keyword(s):  
Multivariate Analysis ◽  
Near Field ◽  
Imaging Data ◽  
Infrared Microscopy

The near-field flow characteristics of some wall-mounted mixing tabs

1999 ◽  
Vol 103 (1023) ◽  
pp. 253-256
Author(s):  
S. C. M. Yu ◽  
L. P. Chua ◽  
E. K. Goh
Keyword(s):  
Boundary Layers ◽  
Near Field ◽  
Flow Characteristics ◽  
Vortex Generator ◽  
Internal Flow ◽  
Vortex Generators ◽  
Streamwise Vortices ◽  
Internal Flows ◽  
Distortion Control ◽  
Flow Feature

It is well known that passive vortex generators can be very effective in controlling separation by ‘re-energising’ the low momentum fluids at the boundary layers. They have been used extensively in many practical aerodynamic applications; both in external and internal flows. Typical examples include aerofoil stall alleviation and engine face distortion control in the jet aircraft intake during high angles of incidence. The general flow feature behind a vortex generator is that a pair of contra-rotating streamwise vortices would be formed which will significantly strengthen the flow at the boundary layers. However, the rationale for successful vortex generator designs is often poorly understood. In many cases, vortex generator designs have even been shown to be arbitrary. Anderson et al and Reichert and Wendt used rectangular fin and tapered fin vortex generators respectively, to eliminate the internal flow separation of S-shaped intake ducts. Both geometries were found to be equally effective. Weng and Guo successfully applied aerofoil shape type of vortex generators to suppress the swirl on the engine face of an S-shaped intake duct at high angles of incidence.

The effect of transient needle lift on the internal flow and near-nozzle spray characteristics for modern GDI systems investigated by high-speed X-ray imaging

2021 ◽  
pp. 146808742098675 ◽  
Author(s):  
Dmitrii Mamaikin ◽  
Tobias Knorsch ◽  
Philipp Rogler ◽  
Jin Wang ◽  
Michael Wensing
Keyword(s):  
High Speed ◽  
Near Field ◽  
Internal Flow ◽  
Transient Behavior ◽  
Liquid Jet ◽  
Nozzle Flow ◽  
Spray Characteristics ◽  
X Ray ◽  
X Ray Imaging ◽  
Primary Breakup

The development of the injector nozzle is a dynamic area in regard of several technical aspects. At first, the internal flow influences the near-field spray characteristics via various phenomena such as cavitation and turbulence. However, these phenomena are not fully understood due to their extremely fast, complex and multiscale nature. Furthermore, it governs the spray targeting inside the combustion chamber. High-speed X-ray imaging of GDI injector nozzles is performed in this study. The experimental results presented are related to the internal flow and primary breakup of discharged liquid jets. The injectors used are equipped with nozzles made of aluminum which have been specially developed for these investigations to enhance optical accessibility. The visualization of the needle motion, in-nozzle flow and the primary breakup region provides several exciting observations. First, the needle lift tracking exhibits short overshooting right before the steady-state of the injection phase. This event leads to a short-term, however, significant change in the associated performance of the breakup. This phenomenon is found to be a consequence of the transient behavior of the in-nozzle flow. It is shown that under some circumstances hydraulic flip may occur during this overshooting period. The primary jet breakup region is visualized and evaluated by means of image processing. Thus, the transient behavior of liquid jet expansion is quantified in the vicinity of the nozzle. It is observed that the liquid jet direction deviates from the hole axis already at the nozzle outlet, which is caused by internal flow characteristics.

scholarly journals Terahertz response of monolayer and few-layer WTe_2 at the nanoscale

2020 ◽  
Author(s):  
Ran Jing ◽  
Yinming Shao ◽  
Zaiyao Fei ◽  
Chiu Fan Bowen Lo ◽  
Francesco Ruta ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Near Field ◽  
Transition Metal Dichalcogenide ◽  
Imaging Data ◽  
Metallic Behavior ◽  
Thermally Activated ◽  
Number Of Layers ◽  
Electromagnetic Behavior ◽  
Thz Range ◽  
Plasmon Polaritons

Abstract Tungsten ditelluride (WTe_2) is a transition metal dichalcogenide whose physical properties depend critically on the number of layers. In this paper, we use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies and cryogenic temperatures to identify distinct THz range electromagnetic behavior of WTe_2 mono-, bi- and tri-layer terraces in the same micro-crystals. We observed clear metallic behavior of the near-field signal on tri-layer regions. Our data are consistent with the existence of surface plasmon polaritons (SPP) in the THz range confined to tri-layer terraces in our specimens. The near-field signal on bi-layer regions surprisingly shows moderately metallicity, but with negligible temperature dependence. Subdiffractional THz imaging data together with theoretical calculations considering thermally activated carriers favor the semimetal scenario over the semiconductor scenario for bi-layer WTe_2. THz images for monolayer terraces uncovered weakly insulating behavior consistent with transport data.

scholarly journals PyNX: high-performance computing toolkit for coherent X-ray imaging based on operators

2020 ◽  
Vol 53 (5) ◽  
pp. 1404-1413
Author(s):  
Vincent Favre-Nicolin ◽  
Gaétan Girard ◽  
Steven Leake ◽  
Jerome Carnis ◽  
Yuriy Chushkin ◽  
...  
Keyword(s):  
High Performance Computing ◽  
High Performance ◽  
Near Field ◽  
Data Sets ◽  
Imaging Data ◽  
Multiple Gpus ◽  
X Ray ◽  
X Ray Imaging ◽  
Graphical Processing ◽  
Performance Computing

The open-source PyNX toolkit has been extended to provide tools for coherent X-ray imaging data analysis and simulation. All calculations can be executed on graphical processing units (GPUs) to achieve high-performance computing speeds. The toolkit can be used for coherent diffraction imaging (CDI), ptychography and wavefront propagation, in the far- or near-field regime. Moreover, all imaging operations (propagation, projections, algorithm cycles…) can be implemented in Python as simple mathematical operators, an approach which can be used to easily combine basic algorithms in a tailored chain. Calculations can also be distributed to multiple GPUs, e.g. for large ptychography data sets. Command-line scripts are available for on-line CDI and ptychography analysis, either from raw beamline data sets or using the coherent X-ray imaging data format.

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