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Publisher: Springer-Verlag (Total: 2351 journals)

 Showing 1201 - 1400 of 2349 Journals sorted alphabetically J. of Clinical Monitoring and Computing       (Followers: 1, SJR: 0.661, h-index: 37) J. of Clinical Psychology in Medical Settings       (Followers: 14, 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: 5, 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: 6, SJR: 1.093, h-index: 34) J. of Communications Technology and Electronics       (Followers: 2, SJR: 0.29, h-index: 16) J. of Community Genetics       (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: 9, SJR: 1.087, h-index: 74) J. of Comparative Physiology B : Biochemical, Systemic, and Environmental Physiology       (Followers: 5, SJR: 1.126, h-index: 59) J. of Compassionate Health Care       (Followers: 3) 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: 3, SJR: 0.995, h-index: 78) J. of Computers in Education       (Followers: 12) J. of Computing in Higher Education       (Followers: 12, 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: 10, SJR: 0.197, h-index: 6) J. of Contemporary Psychotherapy       (Followers: 5, 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: 9, SJR: 0.231, h-index: 9) J. of Crop Science and Biotechnology       (Followers: 3) J. of Cross-Cultural Gerontology       (Followers: 6, SJR: 0.631, h-index: 29) J. of Cryptographic Engineering       (Followers: 4, SJR: 0.989, h-index: 11) J. of Cryptology       (Followers: 3, 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: 10, 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: 7, SJR: 0.574, h-index: 29) J. of Digital Imaging       (Followers: 6, 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: 1, SJR: 0.4, h-index: 26) J. of Dynamics and Differential Equations       (SJR: 1.418, h-index: 31) J. of Earth Science       (Followers: 9, SJR: 0.483, h-index: 16) J. of Earth System Science       (Followers: 49, SJR: 0.448, h-index: 32) J. of East Asian Linguistics       (Followers: 6, SJR: 0.537, h-index: 20) J. of Echocardiography       (Followers: 5, SJR: 0.22, h-index: 3) J. of Ecology and Environment       (Followers: 1) J. of Economic Growth       (Followers: 21, SJR: 3.273, h-index: 63) J. of Economic Interaction and Coordination       (SJR: 0.263, h-index: 12) J. of Economics       (Followers: 12, SJR: 0.418, h-index: 23) J. of Economics and Finance       (Followers: 5, SJR: 0.272, h-index: 19) J. of Educational Change       (Followers: 6, 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: 4, 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 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       (Followers: 1, SJR: 0.145, h-index: 11) J. of Evolutionary Economics       (Followers: 7, 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: 50, 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: 3, SJR: 0.396, h-index: 32) J. of Family Violence       (Followers: 41, 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: 6, SJR: 0.441, h-index: 29) J. of Forest Research       (Followers: 2, SJR: 0.495, h-index: 27) J. of Forestry Research       (Followers: 3, 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: 11, SJR: 1.651, h-index: 88) J. of Gastrointestinal Cancer       (Followers: 3, SJR: 0.304, h-index: 39) J. of Gastrointestinal Surgery       (Followers: 10, 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: 10) J. of Grid Computing       (Followers: 1, SJR: 1.414, h-index: 37) J. of Happiness Studies       (Followers: 26, SJR: 0.881, h-index: 39) J. of Hematopathology       (Followers: 3, SJR: 0.2, h-index: 13) J. of Heuristics       (Followers: 4, SJR: 1.308, h-index: 50) J. of High Energy Physics       (Followers: 17, 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: 7, 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: 2, 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: 9, 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: 2, 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: 10) 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: 10, SJR: 0.338, h-index: 33) J. of Insect Behavior       (Followers: 7, 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: 37, SJR: 4.208, h-index: 130) J. of Intl. Entrepreneurship       (Followers: 12, SJR: 0.549, h-index: 23) J. of Intl. Migration and Integration / Revue de l integration et de la migration internationale       (Followers: 14, 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: 6, 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: 6, 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: 9, SJR: 0.805, h-index: 33) J. of Management Control       (Followers: 5, 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: 17, SJR: 0.228, h-index: 8) J. of Market-Focused Management       (Followers: 2) J. of Marketing Analytics       (Followers: 5) J. of Material Cycles and Waste Management       (Followers: 2, SJR: 0.449, h-index: 22) J. of Materials Engineering and Performance       (Followers: 23, SJR: 0.544, h-index: 40) J. of Materials Science       (Followers: 22, SJR: 0.836, h-index: 123) J. of Materials Science : Materials in Electronics       (Followers: 4) J. of Materials Science : Materials in Medicine       (Followers: 4) J. of Mathematical Biology       (Followers: 9, SJR: 1.011, h-index: 71) J. of Mathematical Chemistry       (Followers: 3, SJR: 0.497, h-index: 45) J. of Mathematical Fluid Mechanics       (Followers: 8, 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: 1, SJR: 0.414, h-index: 23) J. of Mathematical Sciences       (SJR: 0.272, h-index: 23) J. of Mathematics Teacher Education       (Followers: 16, SJR: 1.062, h-index: 20) J. of Maxillofacial and Oral Surgery       (Followers: 3) J. of Mechanical Science and Technology       (Followers: 5, SJR: 0.589, h-index: 26) J. of Medical and Biological Engineering       (Followers: 3, SJR: 0.387, h-index: 18) J. of Medical Humanities       (Followers: 22, SJR: 0.299, h-index: 18) J. of Medical Systems       (SJR: 0.717, h-index: 44) J. of Medical Toxicology       (Followers: 5, 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: 8, SJR: 0.741, h-index: 43) J. of Mining Science       (Followers: 4, SJR: 0.317, h-index: 16) J. of Molecular Evolution       (Followers: 6, SJR: 0.952, h-index: 108) J. of Molecular Histology       (Followers: 4, SJR: 0.755, h-index: 48) J. of Molecular Medicine       (Followers: 11, SJR: 2.165, h-index: 113) J. of Molecular Modeling       (Followers: 4, SJR: 0.466, h-index: 50) J. of Molecular Neuroscience       (Followers: 11, SJR: 0.988, h-index: 69) J. of Mountain Science       (Followers: 2, 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: 1) J. of Nephrology       (Followers: 4, 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: 2, SJR: 1.274, h-index: 90) J. of Neuroimmune Pharmacology       (Followers: 1, SJR: 1.662, h-index: 45) J. of Neurology       (Followers: 16, 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       (SJR: 1.887, h-index: 42) J. of Nonverbal Behavior       (Followers: 5, SJR: 0.723, h-index: 47) J. of Nuclear Cardiology       (SJR: 1.024, h-index: 68) J. of Nutrition, Health and Aging       (Followers: 24, SJR: 0.919, h-index: 60) J. of Obstetrics and Gynecology of India       (Followers: 4, SJR: 0.214, h-index: 6) J. of Occupational Rehabilitation       (Followers: 16, SJR: 0.811, h-index: 51) J. of Ocean Engineering and Marine Energy       (Followers: 3) J. of Ocean University of China (English Edition)       (Followers: 1, SJR: 0.237, h-index: 11) J. of Oceanography       (Followers: 10, 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: 4) J. of Optics       (Followers: 8, SJR: 0.214, h-index: 8) J. of Optimization Theory and Applications       (Followers: 5, SJR: 0.898, h-index: 65) J. of Ornithology       (Followers: 23) J. of Orofacial Orthopedics / Fortschritte der Kieferorthopädie       (SJR: 0.574, h-index: 33) J. of Orthopaedic Science       (Followers: 4, SJR: 0.708, h-index: 48) J. of Paleolimnology       (Followers: 5, SJR: 0.984, h-index: 64)
 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  [2351 journals]
• Applying 2D-2cLIF-EET thermometry for micro-droplet internal temperature
imaging
• Authors: Johannes Palmer; Manuel A. Reddemann; Valeri Kirsch; Reinhold Kneer
Abstract: A new measurement system called “pulsed 2D-2cLIF-EET” has been developed to study temperature fields inside micro-droplets. Pulsed fluorescence excitation allows motion blur suppression and thus simultaneous measurement of droplet size and temperature. Occurrence of morphology-dependent resonances and subsequent stimulated dye emission are accounted for by using “enhanced energy transfer”. The energy transfer requires a second dye that allows re-absorption of stimulated emission and thus enables a shift of dye-lasing to higher wavelengths. However, records of the droplet’s internal temperature field reveal a nonphysical inhomogeneity that is based on locally changing dye excitation intensity and locally changing efficiency of the energy transfer. Dynamics of the inhomogeneity effect are studied extensively by imaging and spectroscopy. Results are used for method optimization.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2506-3
Issue No: Vol. 59, No. 3 (2018)

• On combining linear stochastic estimation and proper orthogonal
decomposition for flow reconstruction
• Authors: Bérengère Podvin; Sylvain Nguimatsia; Jean-Marc Foucaut; Christophe Cuvier; Yann Fraigneau
Abstract: We present an estimation method combining Proper Orthogonal Decomposition (POD) and Linear Stochastic Estimation (LSE). The method is based on a direct mapping of the POD amplitudes from the measurement space to the state space. The method is tested in the turbulent boundary layer for a numerical simulation as well as for experimental data. The goal is to recover the full velocity field on a fine grid from coarse measurements of a single (longitudinal) velocity component. A significant fraction of the turbulent kinetic energy for each component is captured by the estimation. A scale-by-scale analysis shows that lower order modes corresponding to large scales are recovered accurately. Although exact reproduction is not possible at small scales, examination of the spatial and temporal content of the estimated field shows a good statistical agreement with the real field at all scales.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2513-4
Issue No: Vol. 59, No. 3 (2018)

• Error analysis of 3D-PTV through unsteady interfaces
• Authors: Yulia Akutina; Laurent Mydlarski; Susan Gaskin; Olivier Eiff
Abstract: The feasibility of stereoscopic flow measurements through an unsteady optical interface is investigated. Position errors produced by a wavy optical surface are determined analytically, as are the optimal viewing angles of the cameras to minimize such errors. Two methods of measuring the resulting velocity errors are proposed. These methods are applied to 3D particle tracking velocimetry (3D-PTV) data obtained through the free surface of a water flow within a cavity adjacent to a shallow channel. The experiments were performed using two sets of conditions, one having no strong surface perturbations, and the other exhibiting surface gravity waves. In the latter case, the amplitude of the gravity waves was 6% of the water depth, resulting in water surface inclinations of about $$0.2^{\circ }$$ . (The water depth is used herein as a relevant length scale, because the measurements are performed in the entire water column. In a more general case, the relevant scale is the maximum distance from the interface to the measurement plane, H, which here is the same as the water depth.) It was found that the contribution of the waves to the overall measurement error is low. The absolute position errors of the system were moderate (1.2% of H). However, given that the velocity is calculated from the relative displacement of a particle between two frames, the errors in the measured water velocities were reasonably small, because the error in the velocity is the relative position error over the average displacement distance. The relative position error was measured to be 0.04% of H, resulting in small velocity errors of 0.3% of the free-stream velocity (equivalent to 1.1% of the average velocity in the domain). It is concluded that even though the absolute positions to which the velocity vectors are assigned is distorted by the unsteady interface, the magnitude of the velocity vectors themselves remains accurate as long as the waves are slowly varying (have low curvature). The stronger the disturbances on the interface are (high amplitude, short wave length), the smaller is the distance from the interface at which the measurements can be performed.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2509-0
Issue No: Vol. 59, No. 3 (2018)

• Single calibration multiplane stereo-PIV: the effect of mitral valve
orientation on three-dimensional flow in a left ventricle model
• Authors: Hicham Saaid; Patrick Segers; Matteo Novara; Tom Claessens; Pascal Verdonck
Abstract: The characterization of flow patterns in the left ventricle may help the development and interpretation of flow-based parameters of cardiac function and (patho-)physiology. Yet, in vivo visualization of highly dynamic three-dimensional flow patterns in an opaque and moving chamber is a challenging task. This has been shown in several recent multidisciplinary studies where in vivo imaging methods are often complemented by in silico solutions, or by in vitro methods. Because of its distinctive features, particle image velocimetry (PIV) has been extensively used to investigate flow dynamics in the cardiovascular field. However, full volumetric PIV data in a dynamically changing geometry such as the left ventricle remain extremely scarce, which justifies the present study. An investigation of the left ventricle flow making use of a customized cardiovascular simulator is presented; a multiplane scanning-stereoscopic PIV setup is used, which allows for the measurement of independent planes across the measurement volume. Due to the accuracy in traversing the illumination and imaging systems, the present setup allows to reconstruct the flow in a 3D volume performing only one single calibration. The effects of the orientation of a prosthetic mitral valve in anatomical and anti-anatomical configurations have been investigated during the diastolic filling time. The measurement is performed in a phase-locked manner; the mean velocity components are presented together with the vorticity and turbulent kinetic energy maps. The reconstructed 3D flow structures downstream the bileaflet mitral valve are shown, which provides additional insight of the highly three-dimensional flow.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2504-5
Issue No: Vol. 59, No. 3 (2018)

• Effects of free-stream turbulence intensity on transition in a laminar
separation bubble formed over an airfoil
• Authors: Mark S. Istvan; Serhiy Yarusevych
Abstract: The laminar-to-turbulent transition process in a laminar separation bubble formed over a NACA 0018 airfoil is investigated experimentally. All experiments are performed for an angle of attack of 4 $$^{\circ }$$ , chord Reynolds numbers of 80,000 and 125,000, and free-stream turbulence intensities between 0.06 and 1.99%. The results show that increasing the level of free-stream turbulence intensity leads to a decrease in separation bubble length, attributed to a downstream shift in mean separation and an upstream shift in mean reattachment, the later ascribed to an upstream shift in mean transition. Maximum spatial amplification rates of disturbances in the separated shear layer decrease with increasing free-stream turbulence intensity, implying that the larger initial amplitudes of disturbances are solely responsible for the upstream shift in mean transition and as a result mean reattachment. At the baseline level of turbulence intensity, coherent structures forming in the aft portion of the bubble are characterized by strong spanwise coherence at formation, and undergo spanwise deformations leading to localized breakup in the vicinity of mean reattachment. As the level of free-stream turbulence intensity is increased, the spanwise coherence of the shear layer rollers is reduced, and spanwise undulations in the vortex filaments start to take place at the mean location of roll-up. At the highest level of turbulence intensity investigated, streamwise streaks originating in the boundary layer upstream of the separation bubble are observed within the bubble. These streaks signify an onset of bypass transition upstream of the separation bubble, which gives rise to a highly three-dimensional shear layer roll-up. A quantitative analysis of the associated changes in salient characteristics of the coherent structures is presented, connecting the effect of elevated free-stream turbulence intensity on the time-averaged and dynamic characteristics of the separation bubble.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2511-6
Issue No: Vol. 59, No. 3 (2018)

• Pressure spectra from single-snapshot tomographic PIV
• Authors: Jan F. G. Schneiders; Francesco Avallone; Stefan Pröbsting; Daniele Ragni; Fulvio Scarano
Abstract: The power spectral density and coherence of temporal pressure fluctuations are obtained from low-repetition-rate tomographic PIV measurements. This is achieved by extension of recent single-snapshot pressure evaluation techniques based upon the Taylor’s hypothesis (TH) of frozen turbulence and vortex-in-cell (VIC) simulation. Finite time marching of the measured instantaneous velocity fields is performed using TH and VIC. Pressure is calculated from the resulting velocity time series. Because of the theoretical limitations, the finite time marching can be performed until the measured flow structures are convected out of the measurement volume. This provides a lower limit of resolvable frequency range. An upper limit is given by the spatial resolution of the measurements. Finite time-marching approaches are applied to low-repetition-rate tomographic PIV data of the flow past a straight trailing edge at 10 m/s. Reference results of the power spectral density and coherence are obtained from surface pressure transducers. In addition, the results are compared to state-of-the-art experimental data obtained from time-resolved tomographic PIV performed at 10 kHz. The time-resolved approach suffers from low spatial resolution and limited maximum acquisition frequency because of hardware limitations. Additionally, these approaches strongly depend upon the time kernel length chosen for pressure evaluation. On the other hand, the finite time-marching approaches make use of low-repetition-rate tomographic PIV measurements that offer higher spatial resolution. Consequently, increased accuracy of the power spectral density and coherence of pressure fluctuations are obtained in the high-frequency range, in comparison to the time-resolved measurements. The approaches based on TH and VIC are found to perform similarly in the high-frequency range. At lower frequencies, TH is found to underestimate coherence and intensity of the pressure fluctuations in comparison to time-resolved PIV and the microphone reference data. The VIC-based approach, on the other hand, returns results on the order of the reference.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2507-2
Issue No: Vol. 59, No. 3 (2018)

• From drop impact physics to spray cooling models: a critical review
• Authors: Jan Breitenbach; Ilia V. Roisman; Cameron Tropea
Abstract: Spray–wall interaction is an important process encountered in a large number of existing and emerging technologies and is the underlying phenomenon associated with spray cooling. Spray cooling is a very efficient technology, surpassing all other conventional cooling methods, especially those not involving phase change and not exploiting the latent heat of vaporization. However, the effectiveness of spray cooling is dependent on a large number of parameters, including spray characteristics like drop size, velocity and number density, the surface morphology, but also on the temperature range and thermal properties of the materials involved. Indeed, the temperature of the substrate can have significant influence on the hydrodynamics of drop and spray impact, an aspect which is seldom considered in model formulation. This process is extremely complex, thus most design rules to date are highly empirical in nature. On the other hand, significant theoretical progress has been made in recent years about the interaction of single drops with heated walls and improvements to the fundamentals of spray cooling can now be anticipated. The present review has the objective of summarizing some of these recent advances and to establish a framework for future development of more reliable and universal physics-based correlations to describe quantities involved in spray cooling.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2514-3
Issue No: Vol. 59, No. 3 (2018)

• Helium-filled soap bubbles tracing fidelity in wall-bounded turbulence
• Authors: David Engler Faleiros; Marthijn Tuinstra; Andrea Sciacchitano; Fulvio Scarano
Abstract: The use of helium-filled soap bubbles (HFSB) as flow tracers for particle image velocimetry (PIV) and particle tracking velocimetry (PTV) to measure the properties of turbulent boundary layers is investigated in the velocity range from 30 to 50 m/s. The experiments correspond to momentum thickness-based Reynolds numbers of 3300 and 5100. A single bubble generator delivers nearly neutrally buoyant HFSB to seed the air flow developing over the flat plate. The HFSB motion analysis is performed by PTV using single-frame multi-exposure recordings. The measurements yield the local velocity and turbulence statistics. Planar two-component-PIV measurements with micron-sized droplets (DEHS) conducted under the same conditions provide reference data for the quantities of interest. In addition, the behavior of air-filled soap bubbles is studied where the effect of non-neutral buoyancy is more pronounced. The mean velocity profiles as well as the turbulent stresses obtained with HFSB are in good agreement with the flow statistics obtained with DEHS particles. The study illustrates that HFSB tracers can be used to determine the mean velocity and the turbulent fluctuations of turbulent boundary layers above a distance of approximately two bubble diameters from the wall. This work broadens the current range of application of HFSB from external aerodynamics of large-scale-PIV experiments towards wall-bounded turbulence.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2502-7
Issue No: Vol. 59, No. 3 (2018)

• Optical investigation of the interaction of an automotive spray and thin
films by utilization of a high-pressure spin coater
• Authors: Kevin Seel; Manuel A. Reddemann; Reinhold Kneer
Abstract: Although the interaction of automotive sprays with thin films is of high technical relevance for IC engine applications, fundamental knowledge about underlying physical mechanisms is still limited. This work presents a systematic study of the influence of the film’s initial thickness—homogeneously spread over a flat wall before the initial spray impingement—on film surface structures and thickness after the interaction. For this purpose, interferometric film thickness measurements and complementary high-speed visualizations are used. By gradually increasing the initial film thickness on a micrometer scale, a shift from a regime of liquid deposition (increasing film thickness with respect to initial film thickness) to a regime of liquid removal (decreasing film thickness with respect to initial film thickness) is observed at the stagnation zone of the impinging spray. This transition is accompanied by the formation of radially propagating surface waves, transporting liquid away from the stagnation zone. Wavelengths and amplitudes of the surface waves are increased with increasing initial film thickness.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2505-4
Issue No: Vol. 59, No. 3 (2018)

• Fuel film thickness measurements using refractive index matching in a
stratified-charge SI engine operated on E30 and alkylate fuels
• Authors: Carl-Philipp Ding; Magnus Sjöberg; David Vuilleumier; David L. Reuss; Xu He; Benjamin Böhm
Abstract: This study shows fuel film measurements in a spark-ignited direct injection engine using refractive index matching (RIM). The RIM technique is applied to measure the fuel impingement of a high research octane number gasoline fuel with 30 vol% ethanol content at two intake pressures and coolant temperatures. Measurements are conducted for an alkylate fuel at one operating case, as well. It is shown that the fuel volume on the piston surface increases for lower intake pressure and lower coolant temperature and that the alkylate fuel shows very little spray impingement. The fuel films can be linked to increased soot emissions. A detailed description of the calibration technique is provided and measurement uncertainties are discussed. The dependency of the RIM signal on refractive index changes is measured. The RIM technique provides quantitative film thickness measurements up to 0.9 µm in this engine. For thicker films, semi-quantitative results of film thickness can be utilized to study the distribution of impinged fuel.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2512-5
Issue No: Vol. 59, No. 3 (2018)

• Application of laser-induced fluorescence technique in a duct flow with
one heated wall
• Authors: Henrik Rochlitz; Peter Scholz
Abstract: The laser-induced fluorescence technique has been widely used for temperature measurements in liquids. It is based on the temperature dependence of fluorescence intensity of organic dyes like Rhodamines. The fluorescence emissions of Rhodamine B (RhB) and Rhodamine 110 (Rh110) are investigated using a 532 nm pulsed laser. Temperature and dye concentrations as well as optical filters are varied. A setup is qualified for a ratiometric two-color/two-dye (2c/2d) approach and applied in a highly forced convective duct flow with water as the fluid and with one heated wall. The experimental setup is described and results are presented. The two-color/two-dye technique, as compared to a one-color/one-dye technique, was found to give twice as high-temperature sensitivity and approximately one tenth of pulse-to-pulse variations. The technique is used to analyze temperature fields in a turbulent duct flow with one heated wall. Temperature profiles including the thermal boundary layer for varying boundary conditions are presented and analyzed in terms of, e.g., the size of thermal eddies.
PubDate: 2018-02-26
DOI: 10.1007/s00348-018-2508-1
Issue No: Vol. 59, No. 3 (2018)

• Global instability in a laminar boundary layer perturbed by an isolated
roughness element
• Authors: Dominik K. Puckert; Ulrich Rist
Abstract: Roughness-induced boundary-layer instabilities are investigated by means of hot-film anemometry in a water channel to provide experimental evidence of a global instability. It is shown that the roughness wake dynamics depends on extrinsic disturbances (amplifier) at subcritical Reynolds numbers, whereas intrinsic, self-sustained oscillations (wavemaker) are suspected at supercritical Reynolds numbers. The critical Reynolds number, therefore, separates between two different instability mechanisms. Furthermore, the critical Reynolds number from recent theoretical results is successfully confirmed in this experiment, supporting the physical relevance of 3-d global stability theory.
PubDate: 2018-02-13
DOI: 10.1007/s00348-018-2510-7
Issue No: Vol. 59, No. 3 (2018)

• Experimental investigation of the microscale rotor–stator cavity flow
with rotating superhydrophobic surface
• Authors: Chunze Wang; Fei Tang; Qi Li; Xiaohao Wang
Abstract: The flow characteristics of microscale rotor–stator cavity flow and the drag reduction mechanism of the superhydrophobic surface with high shearing stress were investigated. A microscale rotating flow testing system was established based on micro particle image velocimetry (micro-PIV), and the flow distribution under different Reynolds numbers (7.02 × 103 ≤ Re ≤ 3.51 × 104) and cavity aspect ratios (0.013 ≤ G ≤ 0.04) was measured. Experiments show that, for circumferential velocity, the flow field distributes linearly in rotating Couette flow in the case of low Reynolds number along the z-axis, while the boundary layer separates and forms Batchelor flow as the Reynolds number increases. The separation of the boundary layer is accelerated with the increase of cavity aspect ratio. The radial velocities distribute in an S-shape along the z-axis. As the Reynolds number and cavity aspect ratio increase, the maximum value of radial velocity increases, but the extremum position at rotating boundary remains at Z* = 0.85 with no obvious change, while the extremum position at the stationary boundary changes along the z-axis. The model for the generation of flow disturbance and the transmission process from the stationary to the rotating boundary was given by perturbation analysis. Under the action of superhydrophobic surface, velocity slip occurs near the rotating boundary and the shearing stress reduces, which leads to a maximum drag reduction over 51.4%. The contours of vortex swirling strength suggest that the superhydrophobic surface can suppress the vortex swirling strength and repel the vortex structures, resulting in the decrease of shearing Reynolds stress and then drag reduction.
PubDate: 2018-02-12
DOI: 10.1007/s00348-018-2499-y
Issue No: Vol. 59, No. 3 (2018)

• A detailed comparison of single-camera light-field PIV and tomographic PIV
• Authors: Shengxian Shi; Junfei Ding; Callum Atkinson; Julio Soria; T. H. New
Abstract: This paper conducts a comprehensive study between the single-camera light-field particle image velocimetry (LF-PIV) and the multi-camera tomographic particle image velocimetry (Tomo-PIV). Simulation studies were first performed using synthetic light-field and tomographic particle images, which extensively examine the difference between these two techniques by varying key parameters such as pixel to microlens ratio (PMR), light-field camera Tomo-camera pixel ratio (LTPR), particle seeding density and tomographic camera number. Simulation results indicate that the single LF-PIV can achieve accuracy consistent with that of multi-camera Tomo-PIV, but requires the use of overall greater number of pixels. Experimental studies were then conducted by simultaneously measuring low-speed jet flow with single-camera LF-PIV and four-camera Tomo-PIV systems. Experiments confirm that given a sufficiently high pixel resolution, a single-camera LF-PIV system can indeed deliver volumetric velocity field measurements for an equivalent field of view with a spatial resolution commensurate with those of multi-camera Tomo-PIV system, enabling accurate 3D measurements in applications where optical access is limited.
PubDate: 2018-02-10
DOI: 10.1007/s00348-018-2500-9
Issue No: Vol. 59, No. 3 (2018)

• Robust control of drag and lateral dynamic response for road vehicles
exposed to cross-wind gusts
• Authors: Jens Pfeiffer; Rudibert King
Abstract: A robust closed-loop active flow control strategy for road vehicles under unsteady cross-wind conditions is presented. It is designed based on black-box models identified from experimental data for a 3D bluff body equipped with Coanda actuators along the rear edges. The controller adjusts the blowing rates of the actuators individually, achieving a drag reduction of about $$15\%$$ while simultaneously improving cross-wind sensitivity. Hereby, the lateral vehicle dynamics and driver behavior are taken into account and replicated in the wind tunnel via a novel model support system. The effectiveness of the control strategy is demonstrated via cross-wind gust experiments.
PubDate: 2018-02-09
DOI: 10.1007/s00348-017-2479-7
Issue No: Vol. 59, No. 3 (2018)

• Mixing characterization of highly underexpanded fluid jets with real gas
expansion
• Authors: Felix J. Förster; Steffen Baab; Christoph Steinhausen; Grazia Lamanna; Paul Ewart; Bernhard Weigand
Abstract: We report a comprehensive speed of sound database for multi-component mixing of underexpanded fuel jets with real gas expansion. The paper presents several reference test cases with well-defined experimental conditions providing quantitative data for validation of computational simulations. Two injectant fluids, fundamentally different with respect to their critical properties, are brought to supercritical state and discharged into cold nitrogen at different pressures. The database features a wide range of nozzle pressure ratios covering the regimes that are generally classified as highly and extremely highly underexpanded jets. Further variation is introduced by investigating different injection temperatures. Measurements are obtained along the centerline at different axial positions. In addition, an adiabatic mixing model based on non-ideal thermodynamic mixture properties is used to extract mixture compositions from the experimental speed of sound data. The concentration data obtained are complemented by existing experimental data and represented by an empirical fit.
PubDate: 2018-02-09
DOI: 10.1007/s00348-018-2488-1
Issue No: Vol. 59, No. 3 (2018)

• Correction to: Design and implementation of a hot-wire probe for
simultaneous velocity and vorticity vector measurements in boundary layers

• Authors: S. Zimmerman; C. Morrill-Winter; J. Klewicki
Abstract: It has been discovered that the original manuscript presented data that had a sign error associated with the application of Taylor’s frozen turbulence hypothesis.
PubDate: 2018-02-08
DOI: 10.1007/s00348-018-2503-6
Issue No: Vol. 59, No. 3 (2018)

• Measurements in discrete hole film cooling behavior with periodic
freestream unsteadiness
• Authors: Danyang Fan; Daniel D. Borup; Christopher J. Elkins; John K. Eaton
Abstract: Magnetic resonance imaging (MRI) techniques were used to investigate a discrete, $$30^{\circ }$$ -inclined round jet in crossflow subjected to periodic freestream unsteadiness. The freestream perturbations were generated by an oscillating airfoil upstream of the jet. The experiment operated at a Strouhal number of 0.014, channel Reynolds number of 25,000, hole Reynolds number of 2900, and jet blowing ratio of unity. 3D phase locked velocity measurements were obtained over the entire channel using magnetic resonance velocimetry (MRV). 3D time-averaged temperature measurements were acquired using magnetic resonance thermometry (MRT), along with phase-locked temperature measurements in the 2D centerplane of the channel and jet. The freestream flow just upstream of the jet was characterized by streamwise velocities ranging from $$0.88 U_\text {bulk}$$ to $$1.23 U_\text {bulk}$$ and wall-normal velocities from $$-0.11 U_\text {bulk}$$ to $$0.02 U_\text {bulk}$$ . Flow inside the hole was observed to be insensitive to the freestream fluctuations, as velocities and temperatures in the hole remained largely unchanged throughout the cycle. Outside the hole, changes to the streamwise velocity produced an oscillating jet blowing ratio that led to the lengthening and shortening of the counter-rotating vortex pair (CVP) as well as a varying degree of coolant separation from the film cooled wall. During one portion of the cycle, downwashing freestream flow (i.e., flow with negative wall-normal velocities) promoted strong re-attachment and lateral spreading of the jet. Mean, spanwise-averaged film cooling effectiveness values were compared to those of an earlier experiment with a steady freestream and identical geometry, Reynolds number, and blowing ratio. Film cooling performance in the near-hole region was higher with steady freestream flow. However, at downstream locations, the downward transport of coolant by the periodic downwashing flow led to a higher mean surface effectiveness than in the steady case.
PubDate: 2018-02-08
DOI: 10.1007/s00348-018-2493-4
Issue No: Vol. 59, No. 3 (2018)

• Examination of the effect of blowing on the near-surface flow structure
over a dimpled surface
• Authors: C. G. Borchetta; A. Martin; S. C. C. Bailey
Abstract: The near surface flow over a dimpled surface with flow injection through it was documented using time-resolved particle image velocimetry. The instantaneous flow structure, time-averaged statistics, and results from snapshot proper orthogonal decomposition were used to examine the coherent structures forming near the dimpled surface. In particular, the modifications made to the flow structures by the addition of flow injection through the surface were studied. It was observed that without flow injection, inclined flow structures with alternating vorticity from neighboring dimples are generated by the dimples and advect downstream. This behavior is coupled with fluid becoming entrained inside the dimples, recirculating and ejecting away from the surface. When flow injection was introduced through the surface, the flow structures became more disorganized, but some of the features of the semi-periodic structures observed without flow injection were preserved. The structures with flow injection appear in multiple wall-normal layers, formed from vortical structures shed from upstream dimples, with a corresponding increase in the size of the advecting structures. As a result of the more complex flow field observed with flow injection, there was an increase in turbulent kinetic energy and Reynolds shear stress, with the Reynolds shear stress representing an increase in vertical transport of momentum by sweeping and ejecting motions that were not present without flow injection.
PubDate: 2018-02-08
DOI: 10.1007/s00348-018-2498-z
Issue No: Vol. 59, No. 3 (2018)

• Planar measurements of spray-induced wall cooling using phosphor
thermometry
• Authors: Plamen Dragomirov; Aldo Mendieta; Christopher Abram; Benoît Fond; Frank Beyrau
Abstract: The wall cooling induced by spray impingement is investigated using phosphor thermometry. Thin coatings of zinc oxide (ZnO) phosphor were applied with a transparent chemical binder onto a steel surface. Instantaneous spatially resolved temperatures were determined using the spectral intensity ratio method directly after the injection of UV-grade hexane onto the surface using a commercial gasoline injector. The investigations showed that 2D temperature measurements with high spatial and shot-to-shot precision of, respectively, 0.5 and 0.6 K can be achieved, allowing the accurate resolution of the cooling induced by the spray. The presence of a liquid film over the phosphor coating during measurements showed no noticeable influence on the measured temperatures. However, in some cases a change in the intensity ratio at the spray impingement area, in the form of a permanent “stain”, could be observed after multiple injections. The formation of this stain was less likely with increasing annealing time of the coating as well as lower plate operating temperatures during the injection experiments. Finally, the experimental results indicate a noticeable influence of the thickness of the phosphor coating on the measured spray-induced wall cooling history. Hence, for quantitative analysis, a compromise between coating thickness and measurement accuracy needs to be considered for similar applications where the heat transfer rates are very high.
PubDate: 2018-02-08
DOI: 10.1007/s00348-017-2480-1
Issue No: Vol. 59, No. 3 (2018)

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