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Publisher: Springer-Verlag   (Total: 2353 journals)

 Showing 1201 - 1400 of 2353 Journals sorted alphabetically J. of Clinical Geropsychology       (Followers: 1) J. of Clinical Immunology       (Followers: 14, SJR: 1.332, h-index: 75) J. of Clinical Monitoring and Computing       (Followers: 1, SJR: 0.661, h-index: 37) J. of Clinical Psychology in Medical Settings       (Followers: 13, SJR: 0.46, h-index: 34) J. of Cluster Science       (SJR: 0.416, h-index: 31) J. of Coal Science and Engineering (China)       (SJR: 0.188, h-index: 8) J. of Coastal Conservation       (Followers: 7, SJR: 0.474, h-index: 25) J. of Coatings Technology and Research       (Followers: 5, SJR: 0.425, h-index: 25) J. of Combinatorial Optimization       (Followers: 5, SJR: 1.093, h-index: 34) J. of Communications Technology and Electronics       (Followers: 2, SJR: 0.29, h-index: 16) J. of Community Genetics       (Followers: 1, SJR: 0.727, h-index: 14) J. of Community Health       (Followers: 8, SJR: 0.921, h-index: 44) J. of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology       (Followers: 8, SJR: 1.087, h-index: 74) J. of Comparative Physiology B : Biochemical, Systemic, and Environmental Physiology       (Followers: 4, SJR: 1.126, h-index: 59) J. of Compassionate Health Care       (Followers: 2) J. of Computational Analysis and Applications       (SJR: 0.291, h-index: 19) J. of Computational Electronics       (Followers: 4, SJR: 0.511, h-index: 20) J. of Computational Neuroscience       (Followers: 25, SJR: 1.068, h-index: 60) J. of Computer and Systems Sciences Intl.       (SJR: 0.27, h-index: 13) J. of Computer Science and Technology       (Followers: 5, SJR: 0.437, h-index: 31) J. of Computer Virology and Hacking Techniques       (Followers: 6, SJR: 0.151, h-index: 2) J. of Computer-Aided Molecular Design       (Followers: 2, SJR: 0.995, h-index: 78) J. of Computers in Education       (Followers: 11) J. of Computing in Higher Education       (Followers: 13, SJR: 0.363, h-index: 21) J. of Consumer Policy       (Followers: 7, SJR: 0.704, h-index: 30) J. of Contemporary Mathematical Analysis       (SJR: 0.237, h-index: 5) J. of Contemporary Physics (Armenian Academy of Sciences)       (Followers: 11, SJR: 0.197, h-index: 6) J. of Contemporary Psychotherapy       (Followers: 6, SJR: 0.397, h-index: 23) J. of Control Theory and Applications       (Followers: 2, SJR: 0.359, h-index: 19) J. of Control, Automation and Electrical Systems       (Followers: 10, SJR: 0.231, h-index: 9) J. of Crop Science and Biotechnology       (Followers: 7) J. of Cross-Cultural Gerontology       (Followers: 6, SJR: 0.631, h-index: 29) J. of Cryptographic Engineering       (Followers: 5, SJR: 0.989, h-index: 11) J. of Cryptology       (Followers: 3, SJR: 1.443, h-index: 55) J. of Cultural Economics       (Followers: 4, SJR: 0.539, h-index: 29) J. of Database Marketing & Customer Strategy Management       (Followers: 9, SJR: 0.149, h-index: 8) J. of Derivatives & Hedge Funds       (Followers: 8, SJR: 0.114, h-index: 5) J. of Developmental and Physical Disabilities       (Followers: 8, SJR: 0.574, h-index: 29) J. of Digital Imaging       (Followers: 10, SJR: 0.578, h-index: 35) J. of Direct Data and Digital Marketing Practice       (Followers: 8, SJR: 0.154, h-index: 6) J. of Dynamical and Control Systems       (Followers: 2, SJR: 0.4, h-index: 26) J. of Dynamics and Differential Equations       (SJR: 1.418, h-index: 31) J. of Earth Science       (Followers: 10, SJR: 0.483, h-index: 16) J. of Earth System Science       (Followers: 46, SJR: 0.448, h-index: 32) J. of East Asian Linguistics       (Followers: 6, SJR: 0.537, h-index: 20) J. of Echocardiography       (Followers: 4, SJR: 0.22, h-index: 3) J. of Ecology and Environment J. of Economic Growth       (Followers: 29, SJR: 3.273, h-index: 63) J. of Economic Interaction and Coordination       (SJR: 0.263, h-index: 12) J. of Economics       (Followers: 17, SJR: 0.418, h-index: 23) J. of Economics and Finance       (Followers: 6, SJR: 0.272, h-index: 19) J. of Educational Change       (Followers: 7, SJR: 0.961, h-index: 21) J. of Elasticity       (Followers: 6, SJR: 0.851, h-index: 45) J. of Electroceramics       (SJR: 0.577, h-index: 57) J. of Electronic Materials       (Followers: 5, SJR: 0.609, h-index: 75) J. of Electronic Testing       (Followers: 2, SJR: 0.372, h-index: 27) J. of Electronics (China)       (Followers: 4, SJR: 0.112, h-index: 9) J. of Elementary Science Education       (Followers: 9) J. of Elliptic and Parabolic Equations J. of Engineering Mathematics       (SJR: 0.347, h-index: 37) J. of Engineering Physics and Thermophysics       (Followers: 1, SJR: 0.288, h-index: 11) J. of Engineering Research       (Followers: 1, SJR: 0.145, h-index: 5) J. of Engineering Thermophysics       (Followers: 4, SJR: 0.763, h-index: 9) J. of Environmental Studies and Sciences       (Followers: 2) J. of Ethology       (Followers: 2, SJR: 0.609, h-index: 25) J. of Evolution Equations       (SJR: 0.826, h-index: 26) J. of Evolutionary Biochemistry and Physiology       (SJR: 0.145, h-index: 11) J. of Evolutionary Economics       (Followers: 9, SJR: 0.492, h-index: 52) J. of Experimental and Theoretical Physics       (Followers: 3, SJR: 0.458, h-index: 39) J. of Experimental Criminology       (Followers: 48, SJR: 1.445, h-index: 28) J. of Failure Analysis and Prevention       (Followers: 5, SJR: 0.261, h-index: 15) J. of Family and Economic Issues       (Followers: 6, SJR: 0.396, h-index: 32) J. of Family Violence       (Followers: 38, SJR: 0.639, h-index: 56) J. of Financial Services Marketing       (Followers: 3, SJR: 0.273, h-index: 10) J. of Financial Services Research       (Followers: 24, SJR: 0.572, h-index: 36) J. of Fixed Point Theory and Applications       (SJR: 0.644, h-index: 13) J. of Fluorescence       (Followers: 3, SJR: 0.465, h-index: 56) J. of Food Measurement and Characterization       (SJR: 0.307, h-index: 4) J. of Food Science and Technology       (Followers: 7, SJR: 0.441, h-index: 29) J. of Forest Research       (Followers: 3, SJR: 0.495, h-index: 27) J. of Forestry Research       (Followers: 4, SJR: 0.304, h-index: 14) J. of Fourier Analysis and Applications       (Followers: 1, SJR: 1.18, h-index: 42) J. of Friction and Wear       (Followers: 7, SJR: 0.373, h-index: 7) J. of Fusion Energy       (Followers: 3, SJR: 0.387, h-index: 19) J. of Gambling Studies       (Followers: 7, SJR: 1.171, h-index: 57) J. of Gastroenterology       (Followers: 12, SJR: 1.651, h-index: 88) J. of Gastrointestinal Cancer       (Followers: 4, SJR: 0.304, h-index: 39) J. of Gastrointestinal Surgery       (Followers: 7, SJR: 1.64, h-index: 99) J. of General Internal Medicine       (Followers: 17, SJR: 1.804, h-index: 134) J. of General Plant Pathology       (SJR: 0.554, h-index: 22) J. of Genetic Counseling       (Followers: 6, SJR: 0.902, h-index: 39) J. of Genetics       (Followers: 5, SJR: 0.458, h-index: 28) J. of Geodesy       (Followers: 8, SJR: 2.173, h-index: 56) J. of Geographical Sciences       (Followers: 1, SJR: 0.8, h-index: 23) J. of Geographical Systems       (Followers: 4, SJR: 0.822, h-index: 39) J. of Geometric Analysis       (Followers: 2, SJR: 1.491, h-index: 27) J. of Geometry       (Followers: 1, SJR: 0.272, h-index: 15) J. of Global Optimization       (Followers: 4, SJR: 0.992, h-index: 60) J. of Global Policy and Governance       (Followers: 11) J. of Grid Computing       (Followers: 1, SJR: 1.414, h-index: 37) J. of Happiness Studies       (Followers: 25, SJR: 0.881, h-index: 39) J. of Hematopathology       (Followers: 4, SJR: 0.2, h-index: 13) J. of Heuristics       (Followers: 5, SJR: 1.308, h-index: 50) J. of High Energy Physics       (Followers: 18, SJR: 1.052, h-index: 153) J. of Homotopy and Related Structures       (SJR: 0.232, h-index: 2) J. of Housing and the Built Environment       (Followers: 8, SJR: 0.648, h-index: 28) J. of Huazhong University of Science and Technology [Medical Sciences]       (SJR: 0.344, h-index: 19) J. of Ichthyology       (Followers: 3, SJR: 0.304, h-index: 10) J. of Immigrant and Minority Health       (Followers: 12, SJR: 0.759, h-index: 37) J. of Inclusion Phenomena and Macrocyclic Chemistry       (Followers: 1, SJR: 0.331, h-index: 46) J. of Indian Council of Philosophical Research J. of Indian Philosophy       (Followers: 12, SJR: 0.127, h-index: 12) J. of Industrial Microbiology and Biotechnology       (Followers: 16, SJR: 0.966, h-index: 80) J. of Industry, Competition and Trade       (Followers: 8, SJR: 0.327, h-index: 15) J. of Infection and Chemotherapy       (Followers: 1, SJR: 0.673, h-index: 46) J. of Information Technology       (Followers: 54, SJR: 1.474, h-index: 55) J. of Information Technology Teaching Cases       (Followers: 9) J. of Infrared, Millimeter and Terahertz Waves       (Followers: 2, SJR: 1.25, h-index: 36) J. of Inherited Metabolic Disease       (Followers: 2, SJR: 1.389, h-index: 77) J. of Inorganic and Organometallic Polymers and Materials       (Followers: 9, SJR: 0.338, h-index: 33) J. of Insect Behavior       (Followers: 8, SJR: 0.569, h-index: 39) J. of Insect Conservation       (Followers: 10, SJR: 0.872, h-index: 43) J. of Intelligent and Robotic Systems       (Followers: 3, SJR: 0.629, h-index: 43) J. of Intelligent Information Systems       (Followers: 1, SJR: 0.691, h-index: 43) J. of Intelligent Manufacturing       (Followers: 3, SJR: 1.397, h-index: 54) J. of Interventional Cardiac Electrophysiology       (SJR: 0.93, h-index: 43) J. of Intl. Business Studies       (Followers: 32, SJR: 4.208, h-index: 130) J. of Intl. Entrepreneurship       (Followers: 9, SJR: 0.549, h-index: 23) J. of Intl. Migration and Integration / Revue de l integration et de la migration internationale       (Followers: 13, SJR: 0.308, h-index: 13) J. of Intl. Relations and Development       (Followers: 20, SJR: 0.793, h-index: 22) J. of Labor Research       (Followers: 19, SJR: 0.394, h-index: 27) J. of Logic, Language and Information       (Followers: 7, SJR: 0.288, h-index: 25) J. of Low Temperature Physics       (Followers: 3, SJR: 0.531, h-index: 52) J. of Machinery Manufacture and Reliability       (Followers: 2, SJR: 0.203, h-index: 7) J. of Mammalian Evolution       (Followers: 5, SJR: 1.134, h-index: 37) J. of Mammary Gland Biology and Neoplasia       (Followers: 2, SJR: 2.252, h-index: 83) J. of Management and Governance       (Followers: 14, SJR: 0.805, h-index: 33) J. of Management Control       (Followers: 4, SJR: 0.605, h-index: 6) J. of Marine Science and Application       (Followers: 2, SJR: 0.439, h-index: 11) J. of Marine Science and Technology       (Followers: 3, SJR: 0.235, h-index: 19) J. of Maritime Archaeology       (Followers: 21, SJR: 0.228, h-index: 8) J. of Market-Focused Management       (Followers: 2) J. of Marketing Analytics       (Followers: 4) J. of Material Cycles and Waste Management       (Followers: 3, SJR: 0.449, h-index: 22) J. of Materials Engineering and Performance       (Followers: 22, SJR: 0.544, h-index: 40) J. of Materials Science       (Followers: 21, SJR: 0.836, h-index: 123) J. of Materials Science : Materials in Electronics       (Followers: 5) J. of Materials Science : Materials in Medicine       (Followers: 5) J. of Mathematical Biology       (Followers: 11, SJR: 1.011, h-index: 71) J. of Mathematical Chemistry       (Followers: 4, SJR: 0.497, h-index: 45) J. of Mathematical Fluid Mechanics       (Followers: 7, SJR: 1.22, h-index: 22) J. of Mathematical Imaging and Vision       (Followers: 5, SJR: 0.901, h-index: 53) J. of Mathematical Modelling and Algorithms       (Followers: 2, SJR: 0.414, h-index: 23) J. of Mathematical Sciences       (SJR: 0.272, h-index: 23) J. of Mathematics Teacher Education       (Followers: 17, SJR: 1.062, h-index: 20) J. of Maxillofacial and Oral Surgery       (Followers: 3) J. of Mechanical Science and Technology       (Followers: 6, SJR: 0.589, h-index: 26) J. of Medical and Biological Engineering       (Followers: 1, SJR: 0.387, h-index: 18) J. of Medical Humanities       (Followers: 22, SJR: 0.299, h-index: 18) J. of Medical Systems       (Followers: 1, SJR: 0.717, h-index: 44) J. of Medical Toxicology       (Followers: 6, SJR: 0.874, h-index: 28) J. of Medical Ultrasonics       (Followers: 2, SJR: 0.18, h-index: 13) J. of Medicine and the Person J. of Membrane Biology       (Followers: 2, SJR: 0.738, h-index: 82) J. of Micro-Bio Robotics       (SJR: 0.28, h-index: 3) J. of Microbiology       (Followers: 8, SJR: 0.741, h-index: 43) J. of Mining Science       (Followers: 4, SJR: 0.317, h-index: 16) J. of Molecular Evolution       (Followers: 9, SJR: 0.952, h-index: 108) J. of Molecular Histology       (Followers: 4, SJR: 0.755, h-index: 48) J. of Molecular Medicine       (Followers: 14, SJR: 2.165, h-index: 113) J. 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h-index: 65) J. of Ornithology       (Followers: 24) J. of Orofacial Orthopedics / Fortschritte der Kieferorthopädie       (SJR: 0.574, h-index: 33)
 Experiments in Fluids   [SJR: 1.088]   [H-I: 82]   [13 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1432-1114 - ISSN (Online) 0723-4864    Published by Springer-Verlag  [2353 journals]
• Large-scale volumetric flow measurement in a pure thermal plume by dense
tracking of helium-filled soap bubbles
• Authors: Florian Huhn; Daniel Schanz; Sebastian Gesemann; Uwe Dierksheide; Remco van de Meerendonk; Andreas Schröder
Abstract: Abstract We present a spatially and temporally highly resolved flow measurement covering a large volume (~0.6 m3) in a pure thermal plume in air. The thermal plume develops above an extended heat source and is characterized by moderate velocities (U ~ 0.35 m/s) with a Reynolds number of $$\text{Re} \sim 500$$ and a Rayleigh number of $${\text{Ra}}\sim 10^{6}$$ . We demonstrate the requirements and capabilities of the measurement equipment and the particle tracking approach to be able to probe measurement volumes up to and beyond one cubic meter. The use of large tracer particles (300 μm), helium-filled soap bubbles (HFSBs), is crucial and yields high particle image quality over large-volume depths when illuminated with arrays of pulsed high-power LEDs. The experimental limitations of the HFSBs—their limited lifetime and their intensity loss over time—are quantified. The HFSBs’ uniform particle images allows an accurate reconstruction of the flow using Shake-The-Box particle tracking with high particle concentrations up to 0.1 particles per pixel. This enables tracking of up to 275,000 HFSBs simultaneously. After interpolating the scattered data onto a regular grid with a Navier–Stokes regularization, the velocity field of the thermal plume reveals a multitude of vortices with a smooth temporal evolution and a remarkable coherence in time (see animation, supplementary data). Acceleration fields are also derived from interpolated particle tracks and complement the flow measurement. Additionally, the flow map, the basis of a large class of Lagrangian coherent structures, is computed directly from observed particle tracks. We show entrainment regions and coherent vortices of the thermal plume in the flow map and compute fields of the finite-time Lyapunov exponent.
PubDate: 2017-08-03
DOI: 10.1007/s00348-017-2390-2
Issue No: Vol. 58, No. 9 (2017)

• Evaluation of the topological characteristics of the turbulent flow in a
‘box of turbulence’ through 2D time-resolved particle image
velocimetry
• Authors: Huan Lian; Nikolaos Soulopoulos; Yannis Hardalupas
Abstract: Abstract The experimental evaluation of the topological characteristics of the turbulent flow in a ‘box’ of homogeneous and isotropic turbulence (HIT) with zero mean velocity is presented. This requires an initial evaluation of the effect of signal noise on measurement of velocity invariants. The joint probability distribution functions (pdfs) of experimentally evaluated, noise contaminated, velocity invariants have a different shape than the corresponding noise-free joint pdfs obtained from the DNS data of the Johns Hopkins University (JHU) open resource HIT database. A noise model, based on Gaussian and impulsive Salt and Pepper noise, is established and added artificially to the DNS velocity vector field of the JHU database. Digital filtering methods, based on Median and Wiener Filters, are chosen to eliminate the modeled noise source and their capacity to restore the joint pdfs of velocity invariants to that of the noise-free DNS data is examined. The remaining errors after filtering are quantified by evaluating the global mean velocity, turbulent kinetic energy and global turbulent homogeneity, assessed through the behavior of the ratio of the standard deviation of the velocity fluctuations in two directions, the energy spectrum of the velocity fluctuations and the eigenvalues of the rate-of-strain tensor. A method of data filtering, based on median filtered velocity using different median filter window size, is used to quantify the clustering of zero velocity points of the turbulent field using the radial distribution function (RDF) and Voronoï analysis to analyze the 2D time-resolved particle image velocimetry (TR-PIV) velocity measurements. It was found that a median filter with window size 3 × 3 vector spacing is the effective and efficient approach to eliminate the experimental noise from PIV measured velocity images to a satisfactory level and extract the statistical two-dimensional topological turbulent flow patterns.
PubDate: 2017-08-03
DOI: 10.1007/s00348-017-2395-x
Issue No: Vol. 58, No. 9 (2017)

• Determination of heat transfer into a wedge model in a hypersonic flow
using temperature-sensitive paint
• Authors: Steffen Risius; Walter H. Beck; Christian Klein; Ulrich Henne; Alexander Wagner
Abstract: Abstract Heat loads on spacecraft traveling at hypersonic speed are of major interest for their designers. Several tests using temperature-sensitive paints (TSP) have been carried out in long duration shock tunnels to determine these heat loads; generally paint layers were thin, so that certain assumptions could be invoked to enable a good estimate of the thermal parameter ρck (a material property) to be obtained—the value of this parameter is needed to determine heat loads from the TSP. Very few measurements have been carried out in impulse facilities [viz. shock tunnels such as the High Enthalpy Shock Tunnel Göttingen (HEG)], where test times are much shorter. Presented here are TSP temperature measurements and subsequently derived heat loads on a ramp model placed in a hypersonic flow in HEG (specific enthalpy h 0  = ~3.3 MJ kg−1, Mach number M = 7.4, temperature T ∞  = 277 K, density ρ ∞  = 11 g m−3). A number of fluorescence intensity images were acquired, from which, with the help of calibration data, temperature field data on the model surface were determined. From these the heat load into the surface was calculated, using an assumption of a 1D, semi-infinite heat transfer model. ρck for the paint was determined using an insitu calibration with a Medtherm coaxial thermocouple mounted on the model; Medtherm ρck is known. Finally presented are sources of various measurement uncertainties, arising from: (1) estimation of ρck; (2) intensity measurement in the chosen interrogation area; (3) paint time response.
PubDate: 2017-08-03
DOI: 10.1007/s00348-017-2393-z
Issue No: Vol. 58, No. 9 (2017)

• Stable detonation characteristics of premixed C 2 H 4 /O 2 gas in narrow
gaps
• Authors: Yuejin Zhu; Zhenhua Pan; Penggang Zhang; Jianfeng Pan
Abstract: Abstract The detonation initiation and propagation characteristics of premixed gas in a confined channel are greatly influenced by some external factors, such as the channel size and the initial pressure. The influences of different gap height and initial pressure of stoichiometric C2H4/O2 combustible premixed gas on the detonation characteristics were investigated using the self-made narrow gaps. The flame propagation processes were captured by the high-speed photography and the detonation trajectories were recorded by the soot-foil technology. The results show that the gap height is found to be proportional to $$P_{0}^{ - 1.493}$$ of the dividing lines, which are used to distinguish the three different detonation states. The detonation initiation process can be accelerated by either decreasing the gap height or increasing the initial pressure. Furthermore, the detonation velocity deficit is closely related to the gap height and the initial pressure, and the relation can be expressed as $$d_{\text{V}} \propto H^{ - 0.8} P_{0}^{ - 0.5}$$ .
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2399-6
Issue No: Vol. 58, No. 9 (2017)

• Skin-friction measurements in a turbulent boundary layer under the
influence of free-stream turbulence
• Authors: Luis Blay Esteban; Eda Dogan; Eduardo Rodríguez-López; Bharathram Ganapathisubramani
Abstract: Abstract This experimental investigation deals with the influence of free-stream turbulence (FST) produced by an active grid on the skin friction of a zero-pressure-gradient turbulent boundary layer. Wall shear stress is obtained by oil-film interferometry. In addition, hot-wire anemometry was performed to obtain wall-normal profiles of streamwise velocity. This enables the skin friction to be deduced from the mean profile. Both methods show remarkable agreement for every test case. Although skin friction is shown to increase with FST, the trend with Reynolds number is found to be similar to cases without FST. Furthermore, once the change in the friction velocity is accounted for, the self-similarity of the logarithmic region and below (i.e. law of the wall) appears to hold for all FST cases investigated.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2397-8
Issue No: Vol. 58, No. 9 (2017)

• Background-oriented schlieren imaging of flow around a circular cylinder
at low Mach numbers
• Authors: Hannes Stadler; André Bauknecht; Silvan Siegrist; Robert Flesch; C. Christian Wolf; Nils van Hinsberg; Markus Jacobs
Abstract: Abstract The background-oriented schlieren (BOS) imaging method has, for the first time, been applied in the investigation of the flow around a circular cylinder at low Mach numbers ( $$M<0.1$$ ). The measurements were conducted in the high pressure wind tunnel, Göttingen, with static pressures ranging from 0.1 MPa to 6.0 MPa and covered a range of the Reynolds numbers of $$0.1\times 10^6 \le Re \le 6.0\times 10^6$$ . Even at ambient pressure and the lowest Reynolds number investigated, density gradients associated with the flow around the cylinder were recorded. The signal-to-noise ratio of the evaluated gradient field improved with increasing stagnation pressure. The separation point could easily be identified with this non-intrusive measurement technique and corresponds well to simultaneous surface pressure measurements. The resulting displacement field is in principle of qualitative nature as the observation angle was parallel to the cylinder axis only in a single point of the recorded images. However, it has been possible to integrate the density field along the surface of the cylinder by successive imaging at incremental angular positions around the cylinder. This density distribution has been found to agree well with the pressure measurements and with potential theory where appropriate.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2398-7
Issue No: Vol. 58, No. 9 (2017)

• Characterization of the external and internal flow structure of an
aerated-liquid injector using X-ray radiography and fluorescence
• Authors: Scott J. Peltier; Kuo-Cheng Lin; Campbell D. Carter; Alan L. Kastengren
Abstract: Abstract In the present study, the internal flowfield of aerated-liquid fuel injectors is examined through X-ray radiography and X-ray fluorescence. An inside–out injector, consisting of a perforated aerating tube within an annular liquid stream, sprays into a quiescent environment at a fixed mass flow rate of water and nitrogen gas. The liquid is doped with bromine (in the form of NaBr) to create an X-ray fluorescence signal. This allows for reasonable absorption and fluorescence signals, and one or both diagnostics can be used to track the liquid distribution. The injector housing is fabricated from beryllium (Be), which allows the internal flowfield to be examined (as Be has relatively low X-ray attenuation coefficient). Two injector geometries are compared, illustrating the effects of aerating orifice size and location on the flow evolution. Time-averaged equivalent pathlength and line-of-sight averaged density ρ(y) reveal the formation of the two-phase mixture, showing that the liquid film thickness along the injector walls is a function of the aerating tube geometry, though only upstream of the nozzle. These differences in gas and liquid distribution (between injectors with different aerating tube designs) are suppressed as the mixture traverses the nozzle contraction. The averaged liquid velocity (computed from the density and liquid mass flow rate) reveals a similar trend. This suggests that at least for the current configurations, the plume width, liquid mass distribution, and averaged liquid velocity for the time-averaged external spray are insensitive to the aerating tube geometry.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2380-4
Issue No: Vol. 58, No. 9 (2017)

• Comparison between two-phase and one-phase SLIPI for instantaneous imaging
of transient sprays
• Authors: Yogeshwar Nath Mishra; Elias Kristensson; Matthias Koegl; Joakim Jönsson; Lars Zigan; Edouard Berrocal
Abstract: Abstract Imaging through optically dense sprays is challenging due to the detection of multiple light scattering, which blurs the recorded images and limits visibility. Structured laser illumination planar imaging (SLIPI) is a technique that is capable of reducing the intensity contribution that stems from multiple scattering in a light sheet imaging configuration. The conventional SLIPI approach is based on recording three modulated sub-images successively, each having a different spatial phase, and has, therefore, been mostly used for temporally averaged imaging. To circumvent this limitation and image spray dynamics, ‘instantaneous’ two-phase (2p) and single-phase (1p) SLIPI approaches have recently been developed. The purpose of the work presented here is to compare these two approaches in terms of optical design, image post-processing routines, multiple scattering suppression ability, and spatial resolution. The two approaches are used to image a transient direct-injection spark-ignition ethanol spray, for both liquid laser-induced fluorescence and Mie scattering detection. The capabilities of the approaches for multiple scattering suppression and image formation have also been numerically modeled by means of Monte Carlo simulation. This article shows that both approaches efficiently suppress the contribution from multiple light scattering, providing images with an intensity profile close to the corresponding single scattering case. Experimentally, this suppression renders both an improvement in image contrast and the removal of undesired stray light components that could be interpreted as signal. However, while 2p-SLIPI preserves most of the initial spatial resolution, 1p-SLIPI results in a loss of spatial resolution, where high-frequency image information is not visible anymore. Thus, there is a trade-off between preserving the most detailed information of the spray structure—with 2p-SLIPI—and being able to record an SLIPI image from a single modulated image only—with 1p-SLIPI. The comparison and technical overview of these two methods presented in this paper can facilitate in selecting which approach is the most suitable for a given application for spray visualization.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2396-9
Issue No: Vol. 58, No. 9 (2017)

• A review of solid–fluid selection options for optical-based measurements
in single-phase liquid, two-phase liquid–liquid and multiphase
solid–liquid flows
• Authors: Stuart F. Wright; Ivan Zadrazil; Christos N. Markides
Abstract: Abstract Experimental techniques based on optical measurement principles have experienced significant growth in recent decades. They are able to provide detailed information with high-spatiotemporal resolution on important scalar (e.g., temperature, concentration, and phase) and vector (e.g., velocity) fields in single-phase or multiphase flows, as well as interfacial characteristics in the latter, which has been instrumental to step-changes in our fundamental understanding of these flows, and the development and validation of advanced models with ever-improving predictive accuracy and reliability. Relevant techniques rely upon well-established optical methods such as direct photography, laser-induced fluorescence, laser Doppler velocimetry/phase Doppler anemometry, particle image/tracking velocimetry, and variants thereof. The accuracy of the resulting data depends on numerous factors including, importantly, the refractive indices of the solids and liquids used. The best results are obtained when the observational materials have closely matched refractive indices, including test-section walls, liquid phases, and any suspended particles. This paper reviews solid–liquid and solid–liquid–liquid refractive-index-matched systems employed in different fields, e.g., multiphase flows, turbomachinery, bio-fluid flows, with an emphasis on liquid–liquid systems. The refractive indices of various aqueous and organic phases found in the literature span the range 1.330–1.620 and 1.251–1.637, respectively, allowing the identification of appropriate combinations to match selected transparent or translucent plastics/polymers, glasses, or custom materials in single-phase liquid or multiphase liquid–liquid flow systems. In addition, the refractive indices of fluids can be further tuned with the use of additives, which also allows for the matching of important flow similarity parameters such as density and viscosity.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2386-y
Issue No: Vol. 58, No. 9 (2017)

• Mitigation of whistling in vertical corrugated pipes by liquid addition
• Authors: A. C. van Eckeveld; J. Westerweel; C. Poelma
Abstract: Abstract When a corrugated pipe is subject to a dry gas flow, high amplitude sound can be produced (so-called ‘whistling’). It was shown previously that liquid addition to corrugated pipe flow has the ability to reduce sound production. Small amounts of liquid are sufficient to mitigate whistling entirely. One of the mitigation mechanisms, cavity filling, is studied experimentally. Acoustic measurements are combined with a planar laser-induced fluorescence technique to measure the liquid accumulation in the cavities of a corrugated pipe. Using this technique, it is shown that the amount of filling of the cavities with liquid increases with increasing liquid injection rate and with reducing gas flow rate. The reduction in whistling amplitude caused by the liquid injection is closely related to the cavity filling. This indicates that the geometric alteration of the pipe wall, caused by the accumulation of liquid inside the cavities, is an important factor in the reduction in whistling amplitude.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2391-1
Issue No: Vol. 58, No. 9 (2017)

• The three-dimensional characteristics of the unsteady wall-pressure in a
low-Mach-number rectangular cavity flow with Rossiter model oscillation
• Authors: Jin Xu; Jiang Lei; Junmei Wu; Ke Zhang
Abstract: Abstract This study is focused on examining the three-dimensional characteristics of the unsteady wall-pressure in a low-Mach-number rectangular cavity with Rossiter model oscillation. The effect of cavity width on the resonance is investigated as well. It is observed that not only the resonance magnitude but also the resonance frequency could be altered when the cavity width changes. As the cavity becomes narrow to W/L ≈1, the resonance frequency decreases substantially comparing to that for W/L >1. While for the narrowest cavity with W/L <1, the resonance frequency is the same as that for the wide cavity. Low-frequency disturbances grow stronger as approaching to the side walls. Instantaneous velocity magnitude measurement simultaneously with the unsteady wall-pressure shows the propagation of flow disturbances highly correlated with the pressure resonance. It is observed that for the cavity with W/L ≈1, the pressure resonance is highly correlated with a local propagation of disturbances near the cavity aft wall. The downstream convecting disturbances in the shear layer are found to be weaken in the cases of W/L ≈1. Meanwhile the convection velocity of shear-layer disturbances is decreased, which results in a decrease of the resonance frequency.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2388-9
Issue No: Vol. 58, No. 9 (2017)

• Imaginary particle tracking accelerometry based on time-resolved velocity
fields
• Authors: Zhongyi Wang; Qi Gao; Chong Pan; Lihao Feng; Jinjun Wang
Abstract: Abstract An accurate calculation of material acceleration is important for particle image velocimetry-based pressure reconstruction. Therefore, an imaginary particle tracking accelerometry (IPTA) approach based on time-resolved velocity fields is described in this paper for a better determination of acceleration. Multi-velocity fields and a least squares polynomial fitting of the velocity along imaginary particle trajectories are introduced to improve the acceleration accuracy. The process of imaginary particle tracking is operated iteratively until a convergence condition is satisfied. Then the Lagrangian acceleration (or the material acceleration in the Eulerian coordinates) is acquired by the first-order time derivation of the fitting polynomial. In addition, the sensitivity of the IPTA approach to different levels of noise and parameters that affect its performance is investigated. A criterion is proposed to determine these parameters when using IPTA to calculate the acceleration. Performance of the IPTA method is compared with other velocity-based accelerometry methods, including both Eulerian and Lagrangian methods. Assessments are conducted in a synthetic solid body rotation flow, a synthetic flow of a vortex ring, and an experimental jet flow. The results show that IPTA is a robust method for experimental acceleration determination that can both improve the accuracy of acceleration and provide better physical characteristics of the flow field.
PubDate: 2017-08-02
DOI: 10.1007/s00348-017-2394-y
Issue No: Vol. 58, No. 9 (2017)

• Separation control with fluidic oscillators in water
• Authors: H. -J. Schmidt; R. Woszidlo; C. N. Nayeri; C. O. Paschereit
Abstract: Abstract The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet’s exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.
PubDate: 2017-08-01
DOI: 10.1007/s00348-017-2392-0
Issue No: Vol. 58, No. 8 (2017)

• Erratum to: Application of structured illumination to gas phase
thermometry using thermographic phosphor particles: a study for averaged
imaging
• Authors: Florian Zentgraf; Michael Stephan; Edouard Berrocal; Barbara Albert; Benjamin Böhm; Andreas Dreizler
PubDate: 2017-07-26
DOI: 10.1007/s00348-017-2389-8
Issue No: Vol. 58, No. 8 (2017)

• An experimental study of icing control using DBD plasma actuator
• Authors: Jinsheng Cai; Yongqiang Tian; Xuanshi Meng; Xuzhao Han; Duo Zhang; Haiyang Hu
Abstract: Abstract Ice accretion on aircraft or wind turbine has been widely recognized as a big safety threat in the past decades. This study aims to develop a new approach for icing control using an AC-DBD plasma actuator. The experiments of icing control (i.e., anti-/de-icing) on a cylinder model were conducted in an icing wind tunnel with controlled wind speed (i.e., 15 m/s) and temperature (i.e., $$-10\,^{\circ }$$ C). A digital camera was used to record the dynamic processes of plasma anti-icing and de-icing whilst an infrared imaging system was utilized to map the surface temperature variations during the anti-/de-icing processes. It was found that the AC-DBD plasma actuator is very effective in both anti-icing and de-icing operations. While no ice formation was observed when the plasma actuator served as an anti-icing device, a complete removal of the ice layer with a thickness of 5 mm was achieved by activating the plasma actuator for $$\sim$$ 150 s. Such information demonstrated the feasibility of plasma anti-/de-icing, which could potentially provide more effective and safer icing mitigation strategies.
PubDate: 2017-07-07
DOI: 10.1007/s00348-017-2378-y
Issue No: Vol. 58, No. 8 (2017)

• PIV anisotropic denoising using uncertainty quantification
• Authors: B. Wieneke
Abstract: Abstract Recently, progress has been made to reliably compute uncertainty estimates for each velocity vector in planar flow fields measured with 2D-or stereo-PIV. This information can be used for a post-processing denoising scheme to reduce errors by a spatial averaging scheme preserving true flow fluctuations. Starting with a 5 × 5 vector kernel, a second-order 2D-polynomial function is fitted to the flow field. Vectors just outside will be included in the filter kernel if they lie within the uncertainty band around the fitted function. Repeating this procedure, vectors are added in all directions until the true flow field can no longer be approximated by the second-order polynomial function. The center vector is then replaced by the value of the fitted function. The final shape and size of the filter kernel automatically adjusts to local flow gradients in an optimal way preserving true velocity fluctuations above the noise level. This anisotropic denoising scheme is validated first on synthetic vector fields varying spatial wavelengths of the flow field and noise levels relative to the fluctuation amplitude. For wavelengths larger than 5–7 times the spatial resolution, a noise reduction factor of 2–4 is achieved significantly increasing the velocity dynamic range. For large noise levels above 50% of the flow fluctuation, the denoising scheme can no longer distinguish between true flow fluctuations and noise. Finally, it is shown that the procedure performs well for typical experimental PIV vector fields. It provides an effective alternative to more complicated adaptive PIV algorithms optimizing interrogation window sizes and shapes based on seeding density, local flow gradients, and other criteria.
PubDate: 2017-07-07
DOI: 10.1007/s00348-017-2376-0
Issue No: Vol. 58, No. 8 (2017)

• Visualization of the contact line during the water exit of flat plates
• Authors: A. Tassin; T. Breton; B. Forest; J. Ohana; S. Chalony; D. Le Roux; A. Tancray
Abstract: Abstract We investigate experimentally the time evolution of the wetted surface during the lifting of a body initially floating at the water surface. This phenomenon is referred to as the water exit problem. The water exit experiments were conducted with transparent (PMMA) mock-ups of two different shapes: a circular disc and a square flat plate. Two different lighting systems were used to diffuse light in the mock-up material: a central high-power LED light normal to the surface and an edge-lighting system featuring an array of LED lights. These setups make it possible to illuminate the contact line, which delimits the surface of contact between the mock-up and the water. The characteristic size of the mock-ups is about 20 cm and the acceleration of the mock-up oscillates between 0 and 25 m/ $$\mathrm{s}^2$$ . We show that the central light setup gives satisfactory results for the circular disc and that the edge lighting technique makes it possible to follow a contact line with a time-evolving complex shape (strong changes of convexity) up to 1000 fps. The observations presented in the paper support the possibility of extending this promising technique to more general three-dimensional bodies with arbitrary motion (e.g., including pitch motion).
PubDate: 2017-07-07
DOI: 10.1007/s00348-017-2383-1
Issue No: Vol. 58, No. 8 (2017)

• Sizing of sand and ash particles using their speckle pattern: influence of
particle opacity
• Authors: Sara González Ruiz; Jeroen van Beeck
Abstract: Abstract A speckle pattern is an interference pattern produced by coherent light scattered from an irregular particle. This pattern is observed in the out-of-focus plane of the particle and it can be used to obtain information about the particle size. When the particle is observed in focus, several bright spots known as glare points are observed on its surface. They correspond to the points from which the light is scattered in the direction of observation. Previous studies using the speckle pattern to obtain the size of irregular particles are based on the hypothesis that the glare points are distributed homogeneously over the whole surface of the particle. The research presented in this paper shows that in the case of opaque particles (such as ash particles), only the areas illuminated by the laser light are covered with glare points. This results in an underestimation of the particle size when characterizing opaque particles using their speckle pattern. In this paper, the speckle pattern is used to perform sizing measurements of translucent and opaque particles, and the results are compared with the ones obtained by image processing of their in-focus images.
PubDate: 2017-07-07
DOI: 10.1007/s00348-017-2384-0
Issue No: Vol. 58, No. 8 (2017)

• Shock wave propagation past a gap in a pipeline
• Authors: Russell Hall; Simbarashe Kapfudzaruwa; Beric Skews; Randall Paton
Abstract: Abstract This study numerically and experimentally examines the resulting flow field of a shock wave passing through a pipe gap. The effects of gap geometry and shock Mach number variation are investigated. Incident shock Mach numbers of 1.3, 1.4, and 1.5 and gap widths of 25 and 50 mm were used, which correspond to 0.5 and 1.0 pipe inner diameters, respectively. For both cases, the incident shock wave propagated into the downstream pipe at much reduced strength. A strong expansion propagated into the upstream pipe causing a significant pressure drop from the initial post-shock pressure. Expansion waves at the outflow resulted in supersonic speeds as the flow entered the gap for Mach 1.4 and 1.5. A notable feature was the formation of a standing shock at the inlet to the downstream pipe for the higher two Mach numbers in both cases. Decreasing the gap width moved the standing shock closer to the downstream pipe. For the lowest Mach number of 1.3, no standing shock system was set up. The propagation conditions in the downstream pipe showed that the pressure is initially unsteady, but becomes more uniform, controlled by the developed wave system in the gap. For the flanged gap case, the flow within the gap is confined for much longer and hence produces more intense and complex flow feature interactions and an earlier transition to turbulence. The induced shock strength in the downstream pipe is independent of gap geometry and separation distance examined in this paper as verified by experimental pressure traces.
PubDate: 2017-07-07
DOI: 10.1007/s00348-017-2372-4
Issue No: Vol. 58, No. 8 (2017)

• Fast volume reconstruction for 3D PIV
• Authors: Abhishek Bajpayee; Alexandra H. Techet
Abstract: Abstract Presented is a memory-efficient and highly parallelizable method for reconstructing volumes, based on a homography fit synthetic aperture refocusing method. This technique facilitates rapid processing of very large amounts of data, such as that recorded using high-speed cameras, for the purpose of conducting 3D particle imaging velocimetry and particle tracking velocimetry.
PubDate: 2017-07-07
DOI: 10.1007/s00348-017-2373-3
Issue No: Vol. 58, No. 8 (2017)

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