for Journals by Title or ISSN for Articles by Keywords help

Publisher: Springer-Verlag   (Total: 2335 journals)

 Showing 1201 - 1400 of 2335 Journals sorted alphabetically 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: 7, 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: 1) J. of Computational Analysis and Applications       (SJR: 0.291, h-index: 19) J. of Computational Electronics       (Followers: 3, SJR: 0.511, h-index: 20) J. of Computational Neuroscience       (Followers: 19, 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: 7, SJR: 0.151, h-index: 2) J. of Computer-Aided Molecular Design       (Followers: 4, SJR: 0.995, h-index: 78) J. of Computers in Education       (Followers: 7) J. of Computing in Higher Education       (Followers: 12, SJR: 0.363, h-index: 21) J. of Consumer Policy       (Followers: 5, 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: 1, SJR: 0.197, h-index: 6) J. of Contemporary Psychotherapy       (Followers: 4, 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: 7, SJR: 0.231, h-index: 9) J. of Crop Science and Biotechnology       (Followers: 7) J. of Cross-Cultural Gerontology       (Followers: 3, SJR: 0.631, h-index: 29) J. of Cryptographic Engineering       (Followers: 5, SJR: 0.989, h-index: 11) J. of Cryptology       (Followers: 2, SJR: 1.443, h-index: 55) J. of Cultural Economics       (Followers: 2, SJR: 0.539, h-index: 29) J. of Database Marketing & Customer Strategy Management       (Followers: 8, SJR: 0.149, h-index: 8) J. of Derivatives & Hedge Funds       (Followers: 7, 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: 8, SJR: 0.578, h-index: 35) J. of Direct Data and Digital Marketing Practice       (Followers: 7, 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: 8, SJR: 0.483, h-index: 16) J. of Earth System Science       (Followers: 40, SJR: 0.448, h-index: 32) J. of East Asian Linguistics       (Followers: 5, SJR: 0.537, h-index: 20) J. of Echocardiography       (Followers: 4, SJR: 0.22, h-index: 3) J. of Economic Growth       (Followers: 23, SJR: 3.273, h-index: 63) J. of Economic Interaction and Coordination       (SJR: 0.263, h-index: 12) J. of Economics       (Followers: 9, 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: 5, SJR: 0.851, h-index: 45) J. of Electroceramics       (SJR: 0.577, h-index: 57) J. of Electronic Materials       (Followers: 3, 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: 8) 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       (SJR: 0.145, h-index: 5) J. of Engineering Thermophysics       (Followers: 1, 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: 8, SJR: 0.492, h-index: 52) J. of Experimental and Theoretical Physics       (Followers: 4, SJR: 0.458, h-index: 39) J. of Experimental Criminology       (Followers: 31, 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: 17, 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: 16, 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: 5, SJR: 0.441, h-index: 29) J. of Forest Research       (Followers: 3, SJR: 0.495, h-index: 27) J. of Forestry Research       (Followers: 6, 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: 6, SJR: 0.373, h-index: 7) J. of Fusion Energy       (Followers: 3, SJR: 0.387, h-index: 19) J. of Gambling Studies       (Followers: 4, SJR: 1.171, h-index: 57) J. of Gastroenterology       (Followers: 12, SJR: 1.651, h-index: 88) J. of Gastrointestinal Cancer       (Followers: 3, SJR: 0.304, h-index: 39) J. of Gastrointestinal Surgery       (Followers: 5, SJR: 1.64, h-index: 99) J. of General Internal Medicine       (Followers: 13, SJR: 1.804, h-index: 134) J. of General Plant Pathology       (SJR: 0.554, h-index: 22) J. of Genetic Counseling       (Followers: 4, SJR: 0.902, h-index: 39) J. of Genetics       (Followers: 4, 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: 3, SJR: 0.822, h-index: 39) J. of Geometric Analysis       (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: 8) J. of Grid Computing       (SJR: 1.414, h-index: 37) J. of Hand and Microsurgery       (Followers: 1) J. of Happiness Studies       (Followers: 15, SJR: 0.881, h-index: 39) J. of Hematopathology       (Followers: 3, SJR: 0.2, h-index: 13) J. of Heuristics       (Followers: 5, SJR: 1.308, h-index: 50) J. of High Energy Physics       (Followers: 5, 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: 6, 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: 4, SJR: 0.304, h-index: 10) J. of Immigrant and Minority Health       (Followers: 8, SJR: 0.759, h-index: 37) J. of Inclusion Phenomena and Macrocyclic Chemistry       (Followers: 1, SJR: 0.331, h-index: 46) J. of Indian Philosophy       (Followers: 11, SJR: 0.127, h-index: 12) J. of Indian Prosthodontic Society       (SJR: 0.164, h-index: 7) J. of Industrial Microbiology and Biotechnology       (Followers: 12, SJR: 0.966, h-index: 80) J. of Industry, Competition and Trade       (Followers: 6, SJR: 0.327, h-index: 15) J. of Infection and Chemotherapy       (Followers: 1, SJR: 0.673, h-index: 46) J. of Information Technology       (Followers: 49, SJR: 1.474, h-index: 55) J. of Information Technology Teaching Cases       (Followers: 7) J. of Infrared, Millimeter and Terahertz Waves       (Followers: 1, 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: 7, SJR: 0.338, h-index: 33) J. of Insect Behavior       (Followers: 9, 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: 2, SJR: 0.629, h-index: 43) J. of Intelligent Information Systems       (Followers: 1, SJR: 0.691, h-index: 43) J. of Intelligent Manufacturing       (Followers: 4, SJR: 1.397, h-index: 54) J. of Interventional Cardiac Electrophysiology       (SJR: 0.93, h-index: 43) J. of Intl. Business Studies       (Followers: 27, SJR: 4.208, h-index: 130) J. of Intl. Entrepreneurship       (Followers: 8, SJR: 0.549, h-index: 23) J. of Intl. Migration and Integration / Revue de l integration et de la migration internationale       (Followers: 12, 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: 15, 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: 2, 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: 1, SJR: 2.252, h-index: 83) J. of Management and Governance       (Followers: 12, 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: 3, 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: 3) J. of Material Cycles and Waste Management       (Followers: 3, SJR: 0.449, h-index: 22) J. of Materials Engineering and Performance       (Followers: 24, SJR: 0.544, h-index: 40) J. of Materials Science       (Followers: 19, SJR: 0.836, h-index: 123) J. of Materials Science : Materials in Electronics       (Followers: 3) J. of Materials Science : Materials in Medicine       (Followers: 4) J. of Mathematical Biology       (Followers: 12, SJR: 1.011, h-index: 71) J. of Mathematical Chemistry       (Followers: 5, SJR: 0.497, h-index: 45) J. of Mathematical Fluid Mechanics       (Followers: 5, SJR: 1.22, h-index: 22) J. of Mathematical Imaging and Vision       (Followers: 3, 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: 13, SJR: 1.062, h-index: 20) J. of Maxillofacial and Oral Surgery       (Followers: 2) J. of Mechanical Science and Technology       (Followers: 5, 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: 19, SJR: 0.299, h-index: 18) J. of Medical Systems       (Followers: 1, SJR: 0.717, h-index: 44) J. of Medical Toxicology       (Followers: 4, 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: 1, SJR: 0.738, h-index: 82) J. of Micro-Bio Robotics       (SJR: 0.28, h-index: 3) J. of Microbiology       (Followers: 7, SJR: 0.741, h-index: 43) J. of Mining Science       (Followers: 5, SJR: 0.317, h-index: 16) J. of Molecular Evolution       (Followers: 9, SJR: 0.952, h-index: 108) J. of Molecular Histology       (Followers: 2, SJR: 0.755, h-index: 48) J. of Molecular Medicine       (Followers: 15, SJR: 2.165, h-index: 113) J. of Molecular Modeling       (Followers: 4, SJR: 0.466, h-index: 50) J. of Molecular Neuroscience       (Followers: 9, SJR: 0.988, h-index: 69) J. of Mountain Science       (Followers: 3, SJR: 0.418, h-index: 15) J. of Muscle Research and Cell Motility       (Followers: 1, SJR: 1.264, h-index: 55) J. of Nanoparticle Research       (Followers: 3, SJR: 0.583, h-index: 84) J. of Natural Medicines       (SJR: 0.602, h-index: 28) J. of Near-Death Studies       (Followers: 2) J. of Nephrology       (Followers: 5, SJR: 0.689, h-index: 55) J. of Network and Systems Management       (SJR: 0.466, h-index: 26) J. of Neural Transmission       (Followers: 2, SJR: 1.034, h-index: 86) J. of Neuro-Oncology       (Followers: 3, SJR: 1.274, h-index: 90) J. of Neuroimmune Pharmacology       (Followers: 1, SJR: 1.662, h-index: 45) J. of Neurology       (Followers: 13, SJR: 1.429, h-index: 105) J. of NeuroVirology       (Followers: 1, SJR: 0.979, h-index: 69) J. of Nondestructive Evaluation       (Followers: 9, SJR: 0.863, h-index: 27) J. of Nonlinear Science       (Followers: 1, SJR: 1.887, h-index: 42) J. of Nonverbal Behavior       (Followers: 3, SJR: 0.723, h-index: 47) J. of Nuclear Cardiology       (SJR: 1.024, h-index: 68) J. of Nutrition, Health and Aging       (Followers: 18, SJR: 0.919, h-index: 60) J. of Obstetrics and Gynecology of India       (Followers: 7, SJR: 0.214, h-index: 6) J. of Occupational Rehabilitation       (Followers: 12, SJR: 0.811, h-index: 51) J. of Ocean Engineering and Marine Energy       (Followers: 1) J. of Ocean University of China (English Edition)       (Followers: 1, SJR: 0.237, h-index: 11) J. of Oceanography       (Followers: 7, SJR: 0.796, h-index: 52) J. of Ocular Biology, Diseases, and Informatics       (SJR: 0.183, h-index: 11) J. of Optical and Fiber Communications Reports       (Followers: 3) J. of Optics       (Followers: 5, SJR: 0.214, h-index: 8) J. of Optimization Theory and Applications       (Followers: 3, SJR: 0.898, h-index: 65) J. of Ornithology       (Followers: 22) J. of Orofacial Orthopedics / Fortschritte der Kieferorthopädie       (SJR: 0.574, h-index: 33) J. of Orthopaedic Science       (Followers: 5, SJR: 0.708, h-index: 48) J. of Paleolimnology       (Followers: 5, SJR: 0.984, h-index: 64) J. of Parasitic Diseases       (Followers: 2, SJR: 0.298, h-index: 9) J. of Pediatric Neuropsychology       (Followers: 1) J. of Pest Science       (Followers: 2, SJR: 1.341, h-index: 28) J. of Pharmaceutical Health Care and Sciences J. of Pharmaceutical Innovation       (Followers: 8, SJR: 0.524, h-index: 17) J. of Pharmaceutical Investigation       (Followers: 1, SJR: 0.331, h-index: 6) J. of Pharmacokinetics and Pharmacodynamics       (Followers: 21, SJR: 0.708, h-index: 46) J. of Phase Equilibria and Diffusion       (Followers: 19, SJR: 0.433, h-index: 36) J. of Philosophical Logic       (Followers: 8, SJR: 0.704, h-index: 26)
 Experiments in Fluids   [SJR: 1.088]   [H-I: 82]   [10 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1432-1114 - ISSN (Online) 0723-4864    Published by Springer-Verlag  [2335 journals]
• Direct measurement of wall slip and slip layer thickness of non-Brownian
hard-sphere suspensions in rectangular channel flows
• Authors: Steffen Jesinghausen; Rene Weiffen; Hans-Joachim Schmid
Abstract: Abstract Wall slip is a long-known phenomenon in the field of rheology. Nevertheless, the origin and the evolution are not completely clear yet. Regarding suspensions, the effect becomes even more complicated, because different mechanisms like pure slip or slip due to particle migration have to be taken into account. Furthermore, suspensions themselves show many flow anomalies and the isolation of slip is complicated. In order to develop working physical models, further insight is necessary. In this work, we measured experimentally the wall slip velocities of different highly filled suspensions in a rectangular slit die directly with respect to the particle concentration and the particle size. The slip velocities were obtained using a particle image velocimetry (PIV) system. The suspensions consisting of a castor oil–cinnamon oil blend and PMMA particles were matched in terms of refractive indexes to appear transparent. Hereby, possible optical path lengths larger than 15 mm were achieved. The slip velocities were found to be in a quadratic relation to the wall shear stress. Furthermore, the overall flow rate as well as the particle concentration has a direct influence on the slip. Concerning the shear stress, there seem to be two regions of slip with different physical characteristics. Furthermore, we estimated the slip layer thickness directly from the velocity profiles and propose a new interpretation. The PIV technique is used to investigate the viscosity and implicit the concentration profile in the slit die. It is shown that the particle migration process is quite fast.
PubDate: 2016-09-12
DOI: 10.1007/s00348-016-2241-6
Issue No: Vol. 57, No. 9 (2016)

• Design and testing of temperature tunable de Laval nozzles for
applications in gas-phase reaction kinetics
• Authors: A. Canosa; A. J. Ocaña; M. Antiñolo; B. Ballesteros; E. Jiménez; J. Albaladejo
Abstract: Abstract A series of three de Laval nozzles initially designed to generate uniform supersonic flows in helium at 23 and 36 K and in argon at 50 K have been used with either pure nitrogen or mixtures of nitrogen with helium or argon in order to make a sequence of pulsed supersonic flows working at different temperatures. For this, a computer homemade program has been used to design de Laval nozzles contours for gas mixtures in order to determine the theoretical pressure P and temperature T in these supersonic flows. Spatial evolution of T along the flow axis downstream of the nozzle exit has been characterized with a fast response Pitot tube instrument newly developed. Twenty-eight different gas mixture conditions have been tested, indicating a very good agreement with the corresponding calculated flow conditions. The length of uniformity ΔL of the supersonic flows have been found to be >30 cm in more than 80 % of the situations and >50 cm for more than 50 % of the tested conditions. Fine temperature tunability was achieved in the range 22–107 K with very small fluctuations of the mean temperature along ΔL. Advantages and limits of these new developments for studies of gas-phase reaction kinetics are discussed.
PubDate: 2016-09-07
DOI: 10.1007/s00348-016-2238-1
Issue No: Vol. 57, No. 9 (2016)

• FFT integration of instantaneous 3D pressure gradient fields measured by
Lagrangian particle tracking in turbulent flows
• Authors: F. Huhn; D. Schanz; S. Gesemann; A. Schröder
Abstract: Abstract Pressure gradient fields in unsteady flows can be estimated through flow measurements of the material acceleration in the fluid and the assumption of the governing momentum equation. In order to derive pressure from its gradient, almost exclusively two numerical methods have been used to spatially integrate the pressure gradient until now: first, direct path integration in the spatial domain, and second, the solution of the Poisson equation for pressure. Instead, we propose an alternative third method that integrates the pressure gradient field in Fourier space. Using a FFT function, the method is fast and easy to implement in programming languages for scientific computing. We demonstrate the accuracy of the integration scheme on a synthetic pressure field and apply it to an experimental example based on time-resolved material acceleration data from high-resolution Lagrangian particle tracking with the Shake-The-Box method.
PubDate: 2016-09-02
DOI: 10.1007/s00348-016-2236-3
Issue No: Vol. 57, No. 9 (2016)

• An experimental study on the aeromechanics and wake characteristics of a
novel twin-rotor wind turbine in a turbulent boundary layer flow
• Authors: Zhenyu Wang; Wei Tian; Ahmet Ozbay; Anupam Sharma; Hui Hu
Abstract: Abstract The aeromechanic performance and wake characteristics of a novel twin-rotor wind turbine (TRWT) design, which has an extra set of smaller, auxiliary rotor blades appended in front of the main rotor, was evaluated experimentally, in comparison with those of a conventional single-rotor wind turbine (SRWT) design. The comparative study was performed in a large-scale wind tunnel with scaled TRWT and SRWT models mounted in the same incoming turbulent boundary layer flow. In addition to quantifying power outputs and the dynamic wind loadings acting on the model turbines, the wake characteristics behind the model turbines were also measured by using a particle image velocimetry system and a Cobra anemometry probe. The measurement results reveal that, while the TRWT design is capable of harnessing more wind energy from the same incoming airflow by reducing the roots losses incurred in the region near the roots of the main rotor blades, it also cause much greater dynamic wind loadings acting on the TRWT model and higher velocity deficits in the near wake behind the TRWT model, in comparison with those of the SRWT case. Due to the existence of the auxiliary rotor, more complex vortex structures were found to be generated in the wake behind the TRWT model, which greatly enhanced the turbulent mixing in the turbine wake, and caused a much faster recovery of the velocity deficits in the turbine far wake. As a result, the TRWT design was also found to enable the same downstream turbine to generate more power when sited in the wake behind the TRWT model than that in the SRWT wake, i.e., by mitigating wake losses in typical wind farm settings.
PubDate: 2016-09-02
DOI: 10.1007/s00348-016-2233-6
Issue No: Vol. 57, No. 9 (2016)

• A new method of dynamic and static stall detection using infrared
thermography
• Authors: A. D. Gardner; C. C. Wolf; M. Raffel
Abstract: Abstract A new method of detecting flow separation for static and pitching airfoils is described, with application to the generation of stall maps for helicopter rotors. An airfoil is heated using a lamp, and a high-speed infrared camera monitors the surface temperature. Subtracting consecutive images and performing a spatial standard deviation over a region of interest yields a single $$\sigma \hbox {DIT}$$ value which is used to detect boundary layer separation on the airfoil. The data can be analysed to identify attached flow (low values of $$\sigma \hbox {DIT}$$ ) and separated flow (high values of $$\sigma \hbox {DIT}$$ ). Although appropriate filtering can significantly improve the signal-to-noise ratio, the method is robust regarding the exact method of analysis and the unfiltered data are sufficiently clear to be analysed without additional processing. For the test airfoil used, stall was measured up to a pitching frequency of 5 Hz, and signal-to-noise ratios indicate that it should be possible to measure stall for a pitching frequency of 20 Hz for a carbon-fibre surface with the thermal properties used.
PubDate: 2016-09-01
DOI: 10.1007/s00348-016-2235-4
Issue No: Vol. 57, No. 9 (2016)

• Three-dimensional inspiratory flow in a double bifurcation airway model
• Authors: Sahar Jalal; Andras Nemes; Tristan Van de Moortele; Sebastian Schmitter; Filippo Coletti
Abstract: Abstract The flow in an idealized airway model is investigated for the steady inhalation case. The geometry consists of a symmetric planar double bifurcation that reflects the anatomical proportions of the human bronchial tree, and a wide range of physiologically relevant Reynolds numbers (Re = 100–5000) is considered. Using magnetic resonance velocimetry, we analyze the three-dimensional fields of velocity and vorticity, along with flow descriptors that characterize the longitudinal and lateral dispersion. In agreement with previous studies, the symmetry of the flow partitioning is broken even at the lower Reynolds numbers, and at the second bifurcation, the fluid favors the medial branches over the lateral ones. This trend reaches a plateau around Re = 2000, above which the turbulent inflow results in smoothed mean velocity gradients. This also reduces the streamwise momentum flux, which is a measure of the longitudinal dispersion by the mean flow. The classic Dean-type counter-rotating vortices are observed in the first-generation daughter branches as a result of the local curvature. In the granddaughter branches, however, the secondary flows are determined by the local curvature only for the lower flow regimes (Re ≤ 250), in which case the classic Dean mechanism prevails. At higher flow regimes, the field is instead dominated by streamwise vortices extending from the daughter into the medial granddaughter branches, where they rotate in the opposite direction with respect to Dean vortices. Circulation and secondary flow intensity show a similar trend as the momentum flux, increasing with Reynolds number up to Re = 2000 and then dropping due to turbulent dissipation of vorticity. The streamwise vortices interact both with each other and with the airway walls, and for Re > 500 they can become stronger in the medial granddaughter than in the upstream daughter branches. With respect to realistic airway models, the idealized geometry produces weaker secondary flows, suggesting that realistic anatomical features may generate more lateral dispersion than canonical symmetric models.
PubDate: 2016-08-27
DOI: 10.1007/s00348-016-2234-5
Issue No: Vol. 57, No. 9 (2016)

• Bouncing antibubbles
• Authors: Jun Zou; Wei Wang; Chen Ji
Abstract: Abstract The behavior of antibubbles bouncing on a gas–liquid interface is studied using a high-speed video camera. The dimensionless bounce time is found to be independent of the impacting velocity of the antibubbles over a wide range of velocities. Whether the drop bounces off the liquid surface or not is sensitive to the Weber number We, and the critical We is presented based on experimental results.
PubDate: 2016-08-25
DOI: 10.1007/s00348-016-2229-2
Issue No: Vol. 57, No. 9 (2016)

• A wavelet-based intermittency detection technique from PIV investigations
in transitional boundary layers
• Authors: Daniele Simoni; Davide Lengani; Roberto Guida
Abstract: Abstract The transition process of the boundary layer growing over a flat plate with pressure gradient simulating the suction side of a low-pressure turbine blade and elevated free-stream turbulence intensity level has been analyzed by means of PIV and hot-wire measurements. A detailed view of the instantaneous flow field in the wall-normal plane highlights the physics characterizing the complex process leading to the formation of large-scale coherent structures during breaking down of the ordered motion of the flow, thus generating randomized oscillations (i.e., turbulent spots). This analysis gives the basis for the development of a new procedure aimed at determining the intermittency function describing (statistically) the transition process. To this end, a wavelet-based method has been employed for the identification of the large-scale structures created during the transition process. Successively, a probability density function of these events has been defined so that an intermittency function is deduced. This latter strictly corresponds to the intermittency function of the transitional flow computed trough a classic procedure based on hot-wire data. The agreement between the two procedures in the intermittency shape and spot production rate proves the capability of the method in providing the statistical representation of the transition process. The main advantages of the procedure here proposed concern with its applicability to PIV data; it does not require a threshold level to discriminate first- and/or second-order time-derivative of hot-wire time traces (that makes the method not influenced by the operator); and it provides a clear evidence of the connection between the flow physics and the statistical representation of transition based on theory of turbulent spot propagation.
PubDate: 2016-08-24
DOI: 10.1007/s00348-016-2231-8
Issue No: Vol. 57, No. 9 (2016)

• On the correspondence between flow structures and convective heat transfer
augmentation for multiple jet impingement
• Authors: Alexandros Terzis
Abstract: Abstract The correspondence between local fluid flow structures and convective heat transfer is a fundamental aspect that is not yet fully understood for multiple jet impingement. Therefore, flow field and heat transfer experiments are separately performed investigating mutual–jet interactions exposed in a self-gained crossflow. The measurements are taken in two narrow impingement channels with different cross-sectional areas and a single exit design. Hence, a gradually increased crossflow momentum is developed from the spent air of the upstream jets. Particle image velocimetry (PIV) and liquid crystal thermography (LCT) are used in order to investigate the aerothermal characteristics of the channel with high spatial resolution. The PIV measurements are taken at planes normal to the target wall and along the centreline of the jets, providing quantitative flow visualisation of jet and crossflow interactions. Spatially resolved heat transfer coefficient distributions on the target plate are evaluated with transient techniques and a multi-layer of thermochromic liquid crystals. The results are analysed aiming to provide a better understanding about the impact of near-wall flow structures on the convective heat transfer augmentation for these complex flow phenomena.
PubDate: 2016-08-24
DOI: 10.1007/s00348-016-2232-7
Issue No: Vol. 57, No. 9 (2016)

• Effects of short splitter plates on vortex shedding and sound generation
in flow past two side-by-side square cylinders
• Authors: Ressa Octavianty; Masahito Asai
Abstract: Abstract Effects of short splitter plates on vortex shedding and sound generation in a low subsonic flow past two side-by-side square cylinders were examined experimentally at Reynolds numbers $${{{Re}}} = 1.0 - 3.3 \times 10^4$$ . The experiment was mainly conducted with the center-to-center distance between the two cylinders of 3.6d (d is the side length of a square cylinder) where vortex shedding from the two cylinders was synchronized with anti-phase relation, generating a quadrupole-like sound source that radiated in-phase sound in the far field. The results showed that the attachment of short splitter plates whose length (c) was ≤0.5d could reduce the sound pressure level of Aeolian tone significantly. Even with the shortest splitter plates of $$c{/}d=0.1$$ , SPL was reduced by 6 dB at Mach number $$M_{\infty }=0.15$$ . This was in contrast to the case of a single square cylinder, for which the attachment of a short splitter plate <0.2d led to no noticeable noise reduction. It was also shown that even when short splitter plates with a spanwise length as long as or less than the correlation length of shed vortices were attached on the two cylinders in a staggered array, the anti-phase vortex shedding and the corresponding in-phase sound radiation were still dominant.
PubDate: 2016-08-20
DOI: 10.1007/s00348-016-2227-4
Issue No: Vol. 57, No. 9 (2016)

• Drag reduction by means of dimpled surfaces in turbulent boundary layers
• Authors: M. van Nesselrooij; L. L. M. Veldhuis; B. W. van Oudheusden; F. F. J. Schrijer
Abstract: Abstract Direct force measurements and particle image velocimetry (PIV) were used to investigate the drag and flow structure caused by surfaces with patterns of shallow spherical dimples with rounded edges subject to turbulent boundary layers. Drag reduction of up to 4 % is found compared to a flat surface. The largest drag reduction was found at the highest tested Reynolds number of 40,000 (based on dimple diameter). A favorable trend promises further improvements at higher Reynolds numbers. PIV revealed the absence of significant separation inside the dimples but did show the existence of a converging/diverging flow in the upstream and downstream dimple half, respectively. This leads to the rejection of theories proposed by other authors concerning the mechanism responsible for drag reduction. Instead, a fundamental dependence on pattern orientation is observed. Furthermore, preliminary Reynolds-averaged Navier–Stokes (RANS) simulations have been compared with the PIV data. Although the large-scale mean flows show good agreement, the numerical simulation predicts no drag reduction. As the RANS approach is inherently incapable of resolving effects on the behavior of small-scale turbulence structure, the origin of drag reduction is attributed to effects on the small-scale turbulence, which is not resolved in the simulations. It is argued that dimples, when placed in well-designed patterns to create the necessary large-scale flow structure, lead to drag reduction by affecting the turbulent structures in the boundary layer, possibly in a way similar to spanwise oscillations of the wall.
PubDate: 2016-08-20
DOI: 10.1007/s00348-016-2230-9
Issue No: Vol. 57, No. 9 (2016)

• Transient wall-jet flowing over a circular cylinder
• Authors: Ron Danon; James W. Gregory; David Greenblatt
Abstract: Abstract The transient flow of a two-dimensional wall-jet over a circular cylinder, following rapid initiation and termination, was investigated experimentally. Unsteady surface pressures and unsteady pressure-sensitive paint were used to gain a basic understanding of the flow physics. Jet initiation produced a starting vortex, upstream of which the Coandă flow developed, producing a large low-pressure peak. Immediately following jet termination, the pressure increased over the first quarter of the circumference, while the downstream separation region remained virtually unaffected. Simplifying analyses and dimensional arguments were used to show that the timescales characterizing the transient development of the integrated loads depend only on the square of the slot height and the kinematic viscosity and are thus independent of the jet velocity. Following jet initiation, the resulting loads varied according to a linear transient model, while small nonlinearities were observed following jet termination. Unsteady pressure-sensitive paint showed that the starting jet emerges from the slot in a two-dimensional manner and that streamwise streaks, identified as Görtler vortices, form well before the flow reaches steady state. During termination, the streamwise structures dissipate downstream initially, with the dissipation propagating upstream.
PubDate: 2016-08-19
DOI: 10.1007/s00348-016-2226-5
Issue No: Vol. 57, No. 9 (2016)

• Quantified infrared imaging of ignition and combustion in a supersonic
flow
• Authors: Timothy Ombrello; David L. Blunck; Michael Resor
Abstract: Abstract The utility of quantified infrared radiation imaging was evaluated through interrogating ignition and burning processes within a cavity-based flameholder in supersonic flows. Two ignition techniques, spark discharge and pulse detonation, along with quasi-steady cavity burning were used to assess the sensitivities of measurements of radiation intensities in the infrared. The shedding of ignition kernels from the spark discharge was imaged, showing that sufficient signal-to-noise ratios can be achieved even with weak radiation emission levels. The ignition events using a pulse detonator were captured with time-resolved measurements of the plume evolution, including the barrel shock, Mach disk, and shock diamonds. Radiation emissions from subsequent firings of the pulse detonator increased, indicating that heat loss to the tube walls occurred in the early pulses. Imaging of the quasi-steady burning within the cavity demonstrated that the highest burning flux (visible broadband chemiluminescence) and radiation from hydrocarbons (3.4 µm) do not coincide with each other for the fueling strategy used. Numerical simulations provided insight into the species distributions that caused the infrared emissions. Overall, infrared radiation measurements have been shown to be feasible through combustor windows in the harsh combustion environments that were interrogated, and offer a new avenue for rapid and quantitative measurements of reactive flow.
PubDate: 2016-08-18
DOI: 10.1007/s00348-016-2210-0
Issue No: Vol. 57, No. 9 (2016)

• Dense velocity reconstruction from tomographic PTV with material
derivatives
• Authors: Jan F. G. Schneiders; Fulvio Scarano
Abstract: Abstract A method is proposed to reconstruct the instantaneous velocity field from time-resolved volumetric particle tracking velocimetry (PTV, e.g., 3D-PTV, tomographic PTV and Shake-the-Box), employing both the instantaneous velocity and the velocity material derivative of the sparse tracer particles. The constraint to the measured temporal derivative of the PTV particle tracks improves the consistency of the reconstructed velocity field. The method is christened as pouring time into space, as it leverages temporal information to increase the spatial resolution of volumetric PTV measurements. This approach becomes relevant in cases where the spatial resolution is limited by the seeding concentration. The method solves an optimization problem to find the vorticity and velocity fields that minimize a cost function, which includes next to instantaneous velocity, also the velocity material derivative. The velocity and its material derivative are related through the vorticity transport equation, and the cost function is minimized using the limited-memory Broyden–Fletcher–Goldfarb–Shanno (L-BFGS) algorithm. The procedure is assessed numerically with a simulated PTV experiment in a turbulent boundary layer from a direct numerical simulation (DNS). The experimental validation considers a tomographic particle image velocimetry (PIV) experiment in a similar turbulent boundary layer and the additional case of a jet flow. The proposed technique (‘vortex-in-cell plus’, VIC+) is compared to tomographic PIV analysis (3D iterative cross-correlation), PTV interpolation methods (linear and adaptive Gaussian windowing) and to vortex-in-cell (VIC) interpolation without the material derivative. A visible increase in resolved details in the turbulent structures is obtained with the VIC+ approach, both in numerical simulations and experiments. This results in a more accurate determination of the turbulent stresses distribution in turbulent boundary layer investigations. Data from a jet experiment, where the vortex topology is retrieved with a small number of tracers indicate the potential utilization of VIC+ in low-concentration experiments as for instance occurring in large-scale volumetric PTV measurements.
PubDate: 2016-08-16
DOI: 10.1007/s00348-016-2225-6
Issue No: Vol. 57, No. 9 (2016)

• Reconstructing three-dimensional wake topology based on planar PIV
measurements and pattern recognition analysis
• Authors: C. Morton; S. Yarusevych
Abstract: Abstract The present study presents a new technique for reconstructing the salient aspects of three-dimensional wake topology based on time-resolved, planar, two-component particle image velocimetry data collected in multiple orthogonal planes. The technique produces conditionally averaged flow field reconstructions based on a pattern recognition analysis of velocity fields. It is validated on the wake of a low-aspect ratio dual step cylinder geometry, consisting of a large diameter cylinder (D) with small aspect ratio (L/D) attached to the mid-span of a small diameter cylinder (d). For a dual step cylinders with D/d = 2, and L/D = 1, numerical and experimental data are considered for ReD = 150 (laminar wake) and for ReD = 2100 (turbulent wake). The results show that the proposed technique successfully reconstructs the dominant periodic wake vortex interactions and can be extended to a wide range of turbulent flows.
PubDate: 2016-09-17
DOI: 10.1007/s00348-016-2240-7
Issue No: Vol. 57, No. 10 (2016)

• Measurement and characterization of fully transient diesel fuel jet
processes in an optical engine with production injectors
• Authors: Nicholas Neal; David Rothamer
Abstract: Abstract The effects of transient rate-of-injection profiles on high-pressure diesel fuel jets have been studied in an optically accessible internal combustion engine. High-speed optical imaging measurements were applied over a range of ambient conditions, fuel types, and injection parameters. This paper demonstrates that during the early part of the injection, while the liquid core is disintegrating, the penetration is functionally linked to the inviscid orifice exit velocity up until a downstream distance hypothesized to be the jet breakup length. The jets then transitioned to a mixing dominated penetration behavior afterward. Therefore, for cases that exhibit transient rate-of-injection profiles, quasi-steady penetration analytical solutions for penetration have poor agreement with the empirical data. The development of an adaptive edgefinding algorithm for accurately detecting jets in engines is detailed. These findings indicate that empirical correlations widely used throughout the engine community for estimating jet penetration do not accurately represent actual injection parameters under transient conditions.
PubDate: 2016-09-14
DOI: 10.1007/s00348-016-2239-0
Issue No: Vol. 57, No. 10 (2016)

• Velocity field measurements in the wake of a propeller model
• Authors: R. Mukund; A. Chandan Kumar
Abstract: Abstract Turboprop configurations are being revisited for the modern-day regional transport aircrafts for their fuel efficiency. The use of laminar flow wings is an effort in this direction. One way to further improve their efficiency is by optimizing the flow over the wing in the propeller wake. Previous studies have focused on improving the gross aerodynamic characteristics of the wing. It is known that the propeller slipstream causes early transition of the boundary layer on the wing. However, an optimized design of the propeller and wing combination could delay this transition and decrease the skin friction drag. Such a wing design would require the detailed knowledge of the development of the slipstream in isolated conditions. There are very few studies in the literature addressing the requirements of transport aircraft having six-bladed propeller and cruising at a high propeller advance ratio. Low-speed wind tunnel experiments have been conducted on a powered propeller model in isolated conditions, measuring the velocity field in the vertical plane behind the propeller using two-component hot-wire anemometry. The data obtained clearly resolved the mean velocity, the turbulence, the ensemble phase averages and the structure and development of the tip vortex. The turbulence in the slipstream showed that transition could be close to the leading edge of the wing, making it a fine case for optimization. The development of the wake with distance shows some interesting flow features, and the data are valuable for flow computation and optimization.
PubDate: 2016-09-14
DOI: 10.1007/s00348-016-2237-2
Issue No: Vol. 57, No. 10 (2016)

• X-ray fluorescence measurements of dissolved gas and cavitation
• Abstract: Abstract The dynamics of dissolved gas and cavitation are strongly coupled, yet these phenomena are difficult to measure in-situ. Both create voids in the fluid that can be difficult to distinguish. We present an application of X-ray fluorescence in which liquid density and total noncondensible gas concentration (both dissolved and nucleated) are simultaneously measured. The liquid phase is doped with 400 ppm of a bromine tracer, and dissolved air is removed and substituted with krypton. Fluorescent emission at X-ray wavelengths is simultaneously excited from the Br and Kr with a focused monochromatic X-ray beam from a synchrotron source. We measure the flow in a cavitating nozzle 0.5 mm in diameter. From Br fluorescence, total displacement of the liquid is measured. From Kr fluorescence, the mass fraction of both dissolved and nucleated gas is measured. Volumetric displacement of liquid due to both cavitation and gas precipitation can be separated through estimation of the local equilibrium dissolved mass fraction. The uncertainty in the line of sight projected densities of the liquid and gas phases is 4–6 %. The high fluorescence yields and energies of Br and Kr allow small mass fractions of gas to be measured, down to 10−5, with an uncertainty of 8 %. These quantitative measurements complement existing optical diagnostic techniques and provide new insight into the diffusion of gas into cavitation bubbles, which can increase their internal density, pressure and lifetimes by orders of magnitude.
PubDate: 2016-09-28

• Image processing using proper orthogonal and dynamic mode decompositions
for the study of cavitation developing on a NACA0015 foil
• Abstract: Abstract The purpose of the present study is to get a better understanding of the hydrodynamic instabilities of sheet cavities which develop along solid walls. The main objective is to highlight the spatial and temporal behavior of such a cavity when it develops on a NACA0015 foil at high Reynolds number. Experimental results show a quasi-steady, periodic, bifurcation domain, with aperiodic cavity behavior corresponding to σ/2α values of 5.75, 5, 4.3 and 3.58. Robust mathematical methods of signal postprocessing (proper orthogonal decomposition and dynamic mode decomposition) were applied in order to emphasize the spatio-temporal nature of the flow. These new techniques put in evidence the 3D effects due to the reentrant jet instabilities or due to propagating shock wave mechanism at the origin of the shedding process of the cavitation cloud.
PubDate: 2016-09-21

• Application of Tomo-PIV in a large-scale supersonic jet flow facility
• Abstract: Abstract Particle imaging velocimetry (PIV) has been used extensively at NASA GRC over the last 15 years to build a benchmark data set of hot and cold jet flow measurements in an effort to understand acoustic noise sources in high-speed jets. Identifying the noise sources in high-speed jets is critical for ultimately modifying the nozzle hardware design/operation and therefore reducing the jet noise. Tomographic PIV (Tomo-PIV) is an innovative approach for acquiring and extracting velocity information across extended volumes of a flow field, enabling the computation of additional fluid mechanical properties not typically available using traditional PIV techniques. The objective of this work was to develop and implement the Tomo-PIV measurement capability and apply it in a large-scale outdoor test facility, where seeding multiple flow streams and operating in the presence of daylight presents formidable challenges. The newly developed Tomo-PIV measurement capability was applied in both a subsonic M 0.9 flow and an under-expanded M 1.4 heated jet flow field. Measurements were also obtained using traditional two-component (2C) PIV and stereo PIV in the M 0.9 flow field for comparison and validation of the Tomo-PIV results. In the case of the M 1.4 flow, only the 2C PIV was applied to allow a comparison with the Tomo-PIV measurement. The Tomo-PIV fields-of-view covered 180 × 180 × 10 mm, and the reconstruction domains were 3500 × 3500 × 200 voxels. These Tomo-PIV measurements yielded all three components of vorticity across entire planes for the first time in heated supersonic jet flows and provided the first full 3D reconstruction of the Mach disk and oblique shock intersections inside of the barrel shocks. Measuring all three components of vorticity across multiple planes in the flow, potentially reduces the number of measurement configurations (streamwise and cross-stream PIV) required to fully characterize the mixing-enhanced nozzle flows routinely studied in aeroacoustics research.
PubDate: 2016-08-23
DOI: 10.1007/s00348-016-2228-3

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327

Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs