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Publisher: Springer-Verlag   (Total: 2335 journals)

 Showing 1201 - 1400 of 2335 Journals sorted alphabetically 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: 2) J. of Computational Analysis and Applications       (SJR: 0.291, h-index: 19) J. of Computational Electronics       (Followers: 4, SJR: 0.511, h-index: 20) J. of Computational Neuroscience       (Followers: 24, 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: 8) J. of Computing in Higher Education       (Followers: 13, SJR: 0.363, h-index: 21) J. of Consumer Policy       (Followers: 7, SJR: 0.704, h-index: 30) J. of Contemporary Mathematical Analysis       (SJR: 0.237, h-index: 5) J. of Contemporary Physics (Armenian Academy of Sciences)       (Followers: 11, SJR: 0.197, h-index: 6) J. of Contemporary Psychotherapy       (Followers: 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: 7) J. of Cross-Cultural Gerontology       (Followers: 5, 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: 4, 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: 9, SJR: 0.114, h-index: 5) J. of Developmental and Physical Disabilities       (Followers: 8, SJR: 0.574, h-index: 29) J. of Digital Imaging       (Followers: 10, SJR: 0.578, h-index: 35) J. of Direct Data and Digital Marketing Practice       (Followers: 8, SJR: 0.154, h-index: 6) J. of Dynamical and Control Systems       (Followers: 2, SJR: 0.4, h-index: 26) J. of Dynamics and Differential Equations       (SJR: 1.418, h-index: 31) J. of Earth Science       (Followers: 8, SJR: 0.483, h-index: 16) J. of Earth System Science       (Followers: 43, 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: 27, SJR: 3.273, h-index: 63) J. of Economic Interaction and Coordination       (SJR: 0.263, h-index: 12) J. of Economics       (Followers: 17, SJR: 0.418, h-index: 23) J. of Economics and Finance       (Followers: 6, SJR: 0.272, h-index: 19) J. of Educational Change       (Followers: 7, SJR: 0.961, h-index: 21) J. of Elasticity       (Followers: 6, SJR: 0.851, h-index: 45) J. of Electroceramics       (SJR: 0.577, h-index: 57) J. of Electronic Materials       (Followers: 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: 9) 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: 2, 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: 3, SJR: 0.458, h-index: 39) J. of Experimental Criminology       (Followers: 44, 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: 36, 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: 22, 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: 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: 7, SJR: 0.373, h-index: 7) J. of Fusion Energy       (Followers: 3, SJR: 0.387, h-index: 19) J. of Gambling Studies       (Followers: 6, 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: 6, SJR: 1.64, h-index: 99) J. of General Internal Medicine       (Followers: 16, SJR: 1.804, h-index: 134) J. of General Plant Pathology       (SJR: 0.554, h-index: 22) J. of Genetic Counseling       (Followers: 5, 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: 4, 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: 9) J. of Grid Computing       (Followers: 1, SJR: 1.414, h-index: 37) J. of Hand and Microsurgery       (Followers: 1) J. of Happiness Studies       (Followers: 23, SJR: 0.881, h-index: 39) J. of Hematopathology       (Followers: 4, SJR: 0.2, h-index: 13) J. of Heuristics       (Followers: 5, SJR: 1.308, h-index: 50) J. of High Energy Physics       (Followers: 19, 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: 3, SJR: 0.304, h-index: 10) J. of Immigrant and Minority Health       (Followers: 11, 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: 12, SJR: 0.127, h-index: 12) J. of Indian Prosthodontic Society       (Followers: 1, SJR: 0.164, h-index: 7) J. of Industrial Microbiology and Biotechnology       (Followers: 15, SJR: 0.966, h-index: 80) J. of Industry, Competition and Trade       (Followers: 8, SJR: 0.327, h-index: 15) J. of Infection and Chemotherapy       (Followers: 1, SJR: 0.673, h-index: 46) J. of Information Technology       (Followers: 54, SJR: 1.474, h-index: 55) J. of Information Technology Teaching Cases       (Followers: 8) J. of Infrared, Millimeter and Terahertz Waves       (Followers: 2, SJR: 1.25, h-index: 36) J. of Inherited Metabolic Disease       (Followers: 2, SJR: 1.389, h-index: 77) J. of Inorganic and Organometallic Polymers and Materials       (Followers: 9, SJR: 0.338, h-index: 33) J. of Insect Behavior       (Followers: 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: 3, SJR: 1.397, h-index: 54) J. of Interventional Cardiac Electrophysiology       (SJR: 0.93, h-index: 43) J. of Intl. Business Studies       (Followers: 30, SJR: 4.208, h-index: 130) J. of Intl. Entrepreneurship       (Followers: 9, SJR: 0.549, h-index: 23) J. of Intl. Migration and Integration / Revue de l integration et de la migration internationale       (Followers: 13, SJR: 0.308, h-index: 13) J. of Intl. Relations and Development       (Followers: 20, SJR: 0.793, h-index: 22) J. of Labor Research       (Followers: 17, SJR: 0.394, h-index: 27) J. of Logic, Language and Information       (Followers: 7, SJR: 0.288, h-index: 25) J. of Low Temperature Physics       (Followers: 3, SJR: 0.531, h-index: 52) J. of Machinery Manufacture and Reliability       (Followers: 2, SJR: 0.203, h-index: 7) J. of Mammalian Evolution       (Followers: 5, SJR: 1.134, h-index: 37) J. of Mammary Gland Biology and Neoplasia       (Followers: 2, SJR: 2.252, h-index: 83) J. of Management and Governance       (Followers: 13, 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: 4) J. of Material Cycles and Waste Management       (Followers: 3, SJR: 0.449, h-index: 22) J. of Materials Engineering and Performance       (Followers: 22, SJR: 0.544, h-index: 40) J. of Materials Science       (Followers: 20, SJR: 0.836, h-index: 123) J. of Materials Science : Materials in Electronics       (Followers: 5) J. of Materials Science : Materials in Medicine       (Followers: 5) J. of Mathematical Biology       (Followers: 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: 6, SJR: 1.22, h-index: 22) J. of Mathematical Imaging and Vision       (Followers: 4, 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: 14, SJR: 1.062, h-index: 20) J. of Maxillofacial and Oral Surgery       (Followers: 2) J. of Mechanical Science and Technology       (Followers: 6, SJR: 0.589, h-index: 26) J. of Medical and Biological Engineering       (Followers: 1, SJR: 0.387, h-index: 18) J. of Medical Humanities       (Followers: 22, SJR: 0.299, h-index: 18) J. of Medical Systems       (Followers: 1, SJR: 0.717, h-index: 44) J. of Medical Toxicology       (Followers: 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: 2, SJR: 0.738, h-index: 82) J. of Micro-Bio Robotics       (SJR: 0.28, h-index: 3) J. of Microbiology       (Followers: 8, SJR: 0.741, h-index: 43) J. of Mining Science       (Followers: 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: 11, SJR: 0.988, h-index: 69) J. of Mountain Science       (Followers: 4, 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: 15, 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: 5, SJR: 0.723, h-index: 47) J. of Nuclear Cardiology       (SJR: 1.024, h-index: 68) J. of Nutrition, Health and Aging       (Followers: 20, SJR: 0.919, h-index: 60) J. of Obstetrics and Gynecology of India       (Followers: 6, SJR: 0.214, h-index: 6) J. of Occupational Rehabilitation       (Followers: 15, SJR: 0.811, h-index: 51) J. of Ocean Engineering and Marine Energy       (Followers: 2) 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: 3) J. of Optics       (Followers: 8, SJR: 0.214, h-index: 8) J. of Optimization Theory and Applications       (Followers: 4, 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: 6, 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: 3) 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: 18, SJR: 0.708, h-index: 46) J. of Phase Equilibria and Diffusion       (Followers: 18, SJR: 0.433, h-index: 36) J. of Philosophical Logic       (Followers: 8, SJR: 0.704, h-index: 26) J. of Physiology and Biochemistry       (Followers: 3, SJR: 0.87, h-index: 33)
 Experiments in Fluids   [SJR: 1.088]   [H-I: 82]   [11 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1432-1114 - ISSN (Online) 0723-4864    Published by Springer-Verlag  [2335 journals]
• Turbulent spots in hypervelocity flow
• Authors: Joseph S. Jewell; Ivett A. Leyva; Joseph E. Shepherd
Abstract: Abstract The turbulent spot propagation process in boundary layer flows of air, nitrogen, carbon dioxide, and air/carbon dioxide mixtures in thermochemical nonequilibrium at high enthalpy is investigated. Experiments are performed in a hypervelocity reflected shock tunnel with a 5-degree half-angle axisymmetric cone instrumented with flush-mounted fast-response coaxial thermocouples. Time-resolved and spatially demarcated heat transfer traces are used to track the propagation of turbulent bursts within the mean flow, and convection rates at approximately 91, 74, and 63% of the boundary layer edge velocity, respectively, are observed for the leading edge, peak, and trailing edge of the spots. A simple model constructed with these spot propagation parameters is used to infer spot generation rates from observed transition onset to completion distance. Spot generation rates in air and nitrogen are estimated to be approximately twice the spot generation rates in air/carbon dioxide mixtures.
PubDate: 2017-03-20
DOI: 10.1007/s00348-017-2317-y
Issue No: Vol. 58, No. 4 (2017)

• Shock wave interactions with liquid sheets
• Authors: H. Jeon; V. Eliasson
Abstract: Abstract Shock wave interactions with a liquid sheet are investigated by impacting planar liquid sheets of varying thicknesses with a planar shock wave. A square frame was designed to hold a rectangular liquid sheet, with a thickness of 5 or 10 mm, using plastic membranes and cotton wires to maintain the planar shape and minimize bulge. The flat liquid sheet, consisting of either water or a cornstarch and water mixture, was suspended in the test section of a shock tube. Incident shock waves with Mach numbers of $$M_\mathrm{s} = 1.34$$ and 1.46 were considered. A schlieren technique with a high-speed camera was used to visualize the shock wave interaction with the liquid sheets. High-frequency pressure sensors were used to measure wave speed, overpressure, and impulse both upstream and downstream of the liquid sheet. Results showed that no transmitted shock wave could be observed through the liquid sheets, but compression waves induced by the shock-accelerated liquid coalesced into a shock wave farther downstream. A thicker liquid sheet resulted in a lower peak overpressure and impulse, and a cornstarch suspension sheet showed a higher attenuation factor compared to a water sheet.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2300-7
Issue No: Vol. 58, No. 4 (2017)

• Quasi-DC electrical discharge characterization in a supersonic flow
• Authors: Alec Houpt; Brock Hedlund; Sergey Leonov; Timothy Ombrello; Campbell Carter
Abstract: Abstract A Quasi-DC (Q-DC) electrical discharge generates a highly transient filamentary plasma in high-speed airflow. Major specific properties of this type of discharge are realized due to a strong coupling of the plasma to the moving gas. The plasma, supplied by a DC voltage waveform, demonstrates a pulsed-periodic pattern of dynamics significantly affecting the flow structure. In this study, the dynamics and plasma parameters of the Q-DC discharge are analyzed in the Supersonic Test Rig (SBR-50) at the University of Notre Dame at Mach number M = 2, stagnation pressure P 0 = (0.9–2.6) × 105 Pa, stagnation temperature T 0 = 300 K, unit Reynolds number ReL = 7–25 × 106 m−1, and plasma power W pl = 3–21 kW. The plasma parameters are measured with current–voltage probes and optical emission spectroscopy. An unsteady pattern of interaction is depicted by high-speed image capturing. The result of the plasma-flow interaction is characterized by means of pressure measurements and schlieren visualization. It is considered that the Q-DC discharge may be employed for active control of duct-driven flows, cavity-based flow, and for effective control of shock wave–boundary layer interaction.
PubDate: 2017-03-18
DOI: 10.1007/s00348-016-2295-5
Issue No: Vol. 58, No. 4 (2017)

• Mixing layer development in compound channel flows with submerged and
emergent rigid vegetation over the floodplains
• Authors: Victor Dupuis; Sébastien Proust; Céline Berni; André Paquier
Abstract: Abstract This laboratory study aims at investigating the longitudinal development of a mixing layer in a compound open-channel (two-stage geometry with a main channel and adjacent floodplains). The floodplains are covered with two roughness types: either a bed roughness representing a submerged dense meadow or emergent roughness elements (cylinders) representing an alluvial forest. The theoretical background used for plane mixing layers is adapted to the highly three-dimensional mixing layer that develops at the main channel/floodplain interface. The mixing layer width is divided into two parts on either side of the interface. For the wooded floodplain, the mixing layer width on the floodplain side levels off downstream much more rapidly than for the grassed floodplain. The lateral profiles of normalised velocity and turbulence quantities are found to be self-similar in the longitudinal direction for a fixed elevation. However, shallowness effects prevented the normalised lateral profiles of velocity and turbulence quantities from coinciding at different elevations. The respective contributions of lateral Reynolds stresses and secondary currents to the lateral exchange of momentum are estimated. At the main channel/floodplain interface, the momentum exchange is driven by Reynolds stresses. In the main channel, both Reynolds stresses and secondary currents contribute to the lateral flux of momentum. Secondary currents are stronger with emergent macro-roughness elements than with bed-roughness only on the floodplains. Large-scale turbulent coherent structures are investigated based on two-point space-time correlations of velocity. These structures are found to span the entire floodplain flow depth, and their convection velocity is close to the depth-averaged longitudinal velocity at the interface. The coherent fluctuations of the longitudinal and lateral velocities have different Strouhal number values, similar to those found in plane mixing layers.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2319-9
Issue No: Vol. 58, No. 4 (2017)

• Resolving vorticity and dissipation in a turbulent boundary layer by
tomographic PTV and VIC+
• Authors: Jan F. G. Schneiders; Fulvio Scarano; Gerrit E. Elsinga
Abstract: Abstract The existing time-resolved tomographic particle image velocimetry (PIV) measurements by Jodai and Elsinga (J Fluid Mech 795:611–633; Jodai, Elsinga, J Fluid Mech 795:611–633, 2016) in a turbulent boundary layer (Re θ  = 2038) are reprocessed using tomographic particle tracking velocimetry (PTV) and vortex-in-cell-plus (VIC+). The resulting small-scale flow properties, i.e. vorticity and turbulence dissipation, are compared. The VIC+ technique was recently proposed and uses the concept of pouring time into space to increase reconstruction quality of instantaneous velocity. The tomographic PTV particle track measurements are interpolated using VIC+ to a dense grid, making use of both particle velocity and Lagrangian acceleration. Comparison of the vortical structures by visualization of isosurfaces of vorticity magnitude shows that the two methods return similar coherent vortical structures, but their strength in terms of vorticity magnitude is increased when using VIC+, which suggests an improvement in spatial resolution. Further statistical evaluation shows that the root mean square (rms) of vorticity fluctuations from tomographic PIV is approximately 40% lower in comparison to a reference profile available from a DNS simulation, while the VIC+ technique returns rms vorticity fluctuations to within 10% of the reference. The dissipation rate is heavily underestimated by tomographic PIV with approximately 50% damping, whereas the VIC+ analysis yields a dissipation rate to within approximately 5% for y + > 25. The fact that dissipation can be directly measured by a volumetric experiment is novel. It differs from existing approaches that involve 2d measurements combined with isotropic turbulence assumptions or apply corrections based on sub-grid scale turbulence modelling. Finally, the study quantifies the spatial response of VIC+ with a sine-wave lattice analysis. The results indicate a twofold increase of spatial resolution with respect to cross-correlation interrogation.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2318-x
Issue No: Vol. 58, No. 4 (2017)

• Proper orthogonal decomposition truncation method for data denoising and
order reduction
• Authors: Melissa C. Brindise; Pavlos P. Vlachos
Abstract: Abstract Proper orthogonal decomposition (POD) is used widely in experimental fluid dynamics for reducing noise in a measured flow field. The efficacy of POD is governed by the selection of modes used for the velocity field reconstruction. Currently, the determination of which or how many modes to keep is a user-defined subjective choice, where an arbitrary amount of energy to retain in the reconstruction, such as 99% cumulative energy, is chosen. Here, we present a novel, fully autonomous, and objective mode-selection method, which we term the entropy-line fit (ELF) method. The ELF method computes the Shannon entropy of the spatial discrete cosine transform of the eigenmodes, and using a two-line fit of the entropy mode spectrum, distinguishes between the modes carrying meaningful signal and those containing noise. We compare the ELF and existing methods using the analytical Hama flow field, synthetic PIV velocity fields derived from DNS turbulent channel flow data, and experimental particle image velocimetry vortex ring data. Overall, the ELF method improves the effectiveness of POD at removing noise from experimentally measured flow fields and subsequently the accuracy of post-processing calculations.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2320-3
Issue No: Vol. 58, No. 4 (2017)

• Anisole fluorescence spectroscopy for temperature measurements with a Hg
(Xe) arc lamp excitation
• Authors: P. Guibert; S. S. Kanumuri; J. Bonnety; K.-H. Tran; B. Serio; D. Bonnet; J. Luc; M. Lavayssiere
Abstract: Abstract The main contribution of this study is to propose time-resolved measurements to determine temperature with a novel source of continuous excitation for an induced fluorescence technique with laser diagnosis based on tracer-induced fluorescence, which has become a major tool for experimental studies of fluid dynamics in reaction flows. We use a Hg (Xe) arc lamp as a continuous light source that has a wide range of emissions in wavelength. With this setup, one can reach high spatial and temporal resolution (temperature, pressure, species concentration, and velocity) to acquire quantitative data for the control of fluid thermal systems, such as engines, combustion chambers, furnaces, and reactors. A fluorescence study was performed on various tracers and their configurations. We focus on an anisole tracer using a broad wavelength of excitations. We propose a calibration to achieve temperature measurements in the range of 493–773 K and from 0.2 to 3.5 MPa of pressure. The temperature-dependent fluorescence is based on a two-line technique. The results give a better understanding of the influence of temperature and pressure in a nitrogen bath gas on the fluorescence photophysics in the UV domain. High temporal resolution was acquired using a high-speed intensified camera setup. The application of the photomultipliers manages the time-scale evolution of the flow in continuous emission and this eliminates the signal-to-noise ratio impact.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2302-5
Issue No: Vol. 58, No. 4 (2017)

• On the motion of linked spheres in a Stokes flow
• Authors: F. Box; E. Han; C. R. Tipton; T. Mullin
Abstract: Abstract The results of an experimental investigation into the motion of linked spheres at low Reynolds number are presented. Small permanent magnets were embedded in the spheres and torques were generated by application of an external magnetic field. Pairs of neutrally buoyant spheres, connected by either glass rods or thin elastic struts, move in a reciprocal orbit when driven by an oscillatory field. An array of three spheres linked by elastic struts buckles in a periodic, non-reciprocal manner. The induced magneto-elastic buckling propels the elemental swimmer and we find that the geometrical asymmetry of the device, introduced by the struts of different lengths, determines the swimming direction. We propose that this novel method of creating movement remotely is suitable for miniaturization.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2321-2
Issue No: Vol. 58, No. 4 (2017)

• PIV measurements of isothermal plane turbulent impinging jets at moderate
Reynolds numbers
• Authors: A. Khayrullina; T. van Hooff; B. Blocken; G. J. F. van Heijst
Abstract: Abstract This paper contains a detailed experimental analysis of an isothermal plane turbulent impinging jet (PTIJ) for two jet widths at moderate Reynolds numbers (7200–13,500) issued on a horizontal plane at fixed relative distances equal to 22.5 and 45 jet widths. The available literature on such flows is scarce. Previous studies on plane turbulent jets mainly focused on free jets, while most studies on impinging jets focused on the heat transfer between the jet and an impingement plane, disregarding jet development. The present study focuses on isothermal PTIJs at moderate Reynolds numbers characteristic of air curtains. Flow visualisations with fluorescent dye and 2D particle image velocimetry (PIV) measurements have been performed. A comparison is made with previous studies of isothermal free turbulent jets at moderate Reynolds numbers. Mean and instantaneous velocity and vorticity, turbulence intensity, and Reynolds shear stress are analysed. The jet issued from the nozzle with higher aspect ratio shows more intensive entrainment and a faster decay of the centreline velocity compared to the jet of lower aspect ratio for the same value of jet Reynolds number. The profiles of centreline and cross-jet velocity and turbulence intensity show that the PTIJs behave as a free plane turbulent jet until 70–75% of the total jet height. Alongside the information obtained on the jet dynamics, the data will be useful for the validation of numerical simulations.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2315-0
Issue No: Vol. 58, No. 4 (2017)

• Effect of instantaneous stirring process on mixing between initially
distant scalars in turbulent obstacle wakes
• Authors: F. Shoaei; J. P. Crimaldi
Abstract: Abstract A two-channel planar laser-induced fluorescence technique is used to study mixing and reactions between two initially distant scalars in the turbulent wake of a cylindrical obstacle. The scalars are released continuously and isokinetically upstream of the cylinder, with a lateral separation that initially impedes mixing between them. The effect of the turbulent wake on mixing and reaction enhancement is determined by measuring the segregation parameter for cases with and without the cylinder obstruction. Results indicate that scalar mixing and reaction rates (in the low-Damkohler limit) increase significantly in the presence of the cylinder wake. The study also shows that the dominant contribution of total reaction derives from the scalar covariance associated with instantaneous flow processes, and depends strongly on streamwise location within the wake. The results have broad implications for mixing processes in engineering and ecology.
PubDate: 2017-03-18
DOI: 10.1007/s00348-017-2303-4
Issue No: Vol. 58, No. 4 (2017)

• Flow around a semicircular cylinder with passive flow control mechanisms
• Authors: A. M. Hamed; J. Vega; B. Liu; L. P. Chamorro
Abstract: Abstract Wind tunnel experiments were performed to study the effect of passive flow control strategies on the wake and drag of a semicircular cylinder of infinite aspect ratio. High-resolution planar particle image velocimetry was used to obtain flow statistics around the semicircular cylinder at Reynolds number $$Re\approx 3.2\times 10^4$$ based on the cylinder diameter. The control mechanisms under consideration include rigid flaps of various lengths placed at the edges of the structure and a small slot along the symmetry plane of the cylinder. Mean velocity fields reveal the distinctive effects of each passive mechanism on the flow, such as velocity recovery, size of the recirculation bubble and location of the reattachment point. The distributions of turbulence kinetic energy and kinematic shear stress show the modulation of each passive control mechanism on the wake, including the onset and location of the maximum turbulence levels. Instantaneous and mean fields of swirling strength further highlight the role of the passive mechanisms in the vortex dynamics. Drag coefficient for the various cases was estimated indirectly from the flow measurements using a momentum balance. This approach shows that long flaps and slot were able to reduce drag with respect to the base case. The rigid flaps with length coincident with the diameter of the cylinder offered the best performance with drag reduction of $$\sim$$ 25 $$\%$$ .
PubDate: 2017-02-27
DOI: 10.1007/s00348-017-2309-y
Issue No: Vol. 58, No. 3 (2017)

• Dynamics of an unsteady stagnation vortical flow via dynamic mode
decomposition analysis
• Authors: Chong Pan; Jianjie Wang; Jinjun Wang; Mao Sun
Abstract: Abstract The dynamics of a large-scale stagnation vortex pair in an axisymmetric stagnation flow subject to a laminar wake disturbance is measured by time-resolved two-dimensional particle image velocimetry, and then quantitatively characterized by both the Eulerian velocity/vorticity fields and the Lagrangian finite-time Lyapunov exponents fields. This vortex pair is found to be the result of the forced response of the stagnation flow to the upstream shearing disturbances, and presents a dynamical evolution of quasi-periodic shedding due to short-wave elliptical instability. Dynamic mode decomposition analysis of both the Eulerian measure and the Lagrangian measure is taken for a quantitative description of this process. The sparsity-promoting scheme (Jovanović et al. Phys Fluids 26(2):024,103, 2014), which integrates the mode identification and truncation as a whole, is used to distinguish those modes with dynamical significance from irrelevant ones with transient behavior. The superiority of this scheme is evidenced by the facts that it avoids the eigenvalue contamination problem, and credits higher priority to the sub-dominant modes directly associated with the system dynamics. It is found that the energetic mode with a frequency of 0.177 Hz, or about 10% of the maximum shear rate of the upstream wake, determines the quasi-periodical vortex formation process. Its half-order harmonic represents the vortex shedding event along one fixed direction. High-order even-quarter harmonics jointly contribute to the circular pattern of the vortex tube. In addition, a set of low-frequency odd-quarter harmonics are highlighted as the elliptical instability and the following vortex deformation process. Based on this finding, a reduce-order representation with 8 Eulerian modes or 56 Lagrangian modes is proposed to characterize the dominant dynamics of this unsteady vortical stagnation flow. In addition, the Eulerian measure seems to be more efficient than the Lagrangian measure in terms of reduced-order representation.
PubDate: 2017-02-27
DOI: 10.1007/s00348-017-2306-1
Issue No: Vol. 58, No. 3 (2017)

• Damping insert materials for settling chambers of supersonic wind tunnels
• Authors: Jie Wu; Rolf Radespiel
Abstract: Abstract This study describes the application of a novel damping insert material for reducing the flow fluctuations in a tandem nozzle supersonic wind tunnel. This new damping material is composed of multi-layer stainless steel wired meshes. The influences of the multi-layer mesh, such as the quantity of the mesh layer and the installed location in the settling chamber, to the freestream quality have been investigated. A Pitot probe instrumented with a Kulite pressure sensor and a hot-wire probe are employed to monitor the flow fluctuation in the test section of the wind tunnel. Thereafter, a combined modal analysis is applied for the disturbance qualification. Additionally, the transient Mach number in the test section is measured. The disturbance qualification indicates that the multi-layer mesh performs well in providing reduction of vorticity reduction and acoustic fluctuations. Comparable flow quality of the freestream was also obtained using a combination of flexible damping materials. However, the life-span of the new damping materials is much longer. The time transient of the Mach number measured in the test section indicates that the mean flow is rather constant over run time. Furthermore, the time-averaged pressure along the settling chamber is recorded and it shows the distribution of pressure drop by settling chamber inserts.
PubDate: 2017-02-22
DOI: 10.1007/s00348-017-2310-5
Issue No: Vol. 58, No. 3 (2017)

• Authors: David E. Rival; Bas van Oudheusden
Abstract: Abstract In a large variety of fluid-dynamic problems, it is often impossible to directly measure the instantaneous aerodynamic or hydrodynamic forces on a moving body. Examples include studies of propulsion in nature, either with mechanical models or living animals, wings, and blades subjected to significant surface contamination, such as icing, sting blockage effects, etc. In these circumstances, load estimation from flow-field data provides an attractive alternative method, while at the same time providing insight into the relationship between unsteady loadings and their associated vortex-wake dynamics. Historically, classical control-volume techniques based on time-averaged measurements have been used to extract the mean forces. With the advent of high-speed imaging, and the rapid progress in time-resolved volumetric measurements, such as Tomo-PIV and 4D-PTV, it is becoming feasible to estimate the instantaneous forces on bodies of complex geometry and/or motion. For effective application under these conditions, a number of challenges still exist, including the near-body treatment of the acceleration field as well as the estimation of pressure on the outer surfaces of the control volume. Additional limitations in temporal and spatial resolutions, and their associated impact on the feasibility of the various approaches, are also discussed. Finally, as an outlook towards the development of future methodologies, the potential application of Lagrangian techniques is explored.
PubDate: 2017-02-22
DOI: 10.1007/s00348-017-2304-3
Issue No: Vol. 58, No. 3 (2017)

• A comprehensive statistical investigation of schlieren image velocimetry
(SIV) using high-velocity helium jet
• Authors: Sayan Biswas; Li Qiao
Abstract: Abstract A detailed statistical assessment of seedless velocity measurement using Schlieren Image Velocimetry (SIV) was explored using open source Robust Phase Correlation (RPC) algorithm. A well-known flow field, an axisymmetric turbulent helium jet, was analyzed near and intermediate region $$(0\le x/d\le 20)$$ for two different Reynolds numbers, Re d = 11,000 and Re d = 22,000 using schlieren with horizontal knife-edge, schlieren with vertical knife-edge and shadowgraph technique, and the resulted velocity fields from SIV techniques were compared to traditional Particle Image Velocimetry (PIV) measurements. A novel, inexpensive, easy to setup two-camera SIV technique had been demonstrated to measure high-velocity turbulent jet, with jet exit velocities 304 m/s (Mach = 0.3) and 611 m/s (Mach = 0.6), respectively. Several image restoration and enhancement techniques were tested to improve signal to noise ratio (SNR) in schlieren and shadowgraph images. Processing and post-processing parameters for SIV techniques were examined in detail. A quantitative comparison between self-seeded SIV techniques and traditional PIV had been made using correlation statistics. While the resulted flow field from schlieren with horizontal knife-edge and shadowgraph showed excellent agreement with PIV measurements, schlieren with vertical knife-edge performed poorly. The performance of spatial cross-correlations at different jet locations using SIV techniques and PIV was evaluated. Turbulence quantities like turbulence intensity, mean velocity fields, Reynolds shear stress influenced spatial correlations and correlation plane SNR heavily. Several performance metrics such as primary peak ratio (PPR), peak to correlation energy (PCE), the probability distribution of signal and noise were used to compare capability and potential of different SIV techniques.
PubDate: 2017-02-17
DOI: 10.1007/s00348-017-2305-2
Issue No: Vol. 58, No. 3 (2017)

• Effect of slotted exit orifice on performance of plasma synthetic jet
actuator
• Authors: Haohua Zong; Marios Kotsonis
Abstract: Abstract This study experimentally investigates the influence of exit orifice shape on the performance characteristics of a three-electrode plasma synthetic jet actuator. High-speed Schlieren imaging system and phase-locked two-component PIV measurements are used for flowfield characterisation in quiescent conditions. Two actuator configurations with the same exit area but different exit orifice shape (round orifice and slot orifice) are studied. Results indicate a close correspondence between the shapes of the starting vortex ring with the shapes of the respective exit orifices. For the slot orifice, the elongated starting vortex ring gradually expands during propagation, while its ends become warped. A distinct K–H instability structure is observed, inducing continuous oscillation of the high-speed jet. Compared with the jet from the round orifice, the slot jet has a higher entrainment rate of surrounding air, thus resulting in a lower propagation velocity of the jet front. The exit velocity of PSJA within one period initially shows a rapid increase, then persists at a relatively high level (100–130 m/s), and finally drops with some small-scale oscillations. The oscillation amplitude is less than 10 m/s, and the oscillation period is approximately 600 µs. Under conditions of same exit area, orifice shape has little influence on the variation of the exit velocity.
PubDate: 2017-02-16
DOI: 10.1007/s00348-016-2299-1
Issue No: Vol. 58, No. 3 (2017)

• Statistical calibration via Gaussianization in hot-wire anemometry
• Authors: Igal Gluzman; Jacob Cohen; Yaakov Oshman
Abstract: Abstract A statistical method is introduced, that is based on Gaussianization to estimate the nonlinear calibration curve of a hot-wire probe, relating the input flow velocity to the output (measured) voltage. The method uses as input a measured sequence of voltage samples, corresponding to different unknown flow velocities in the desired operational range, and only two measured voltages along with their known (calibrated) flow velocities. The method relies on the conditions that (1) the velocity signal is Gaussian distributed (or has another known distribution), and (2) the measured signal covers the desired velocity range over which the sensor is to be calibrated. The novel calibration method is validated against standard calibration methods using data acquired by hot-wire probes in wind-tunnel experiments. In these experiments, a hot-wire probe is placed at a certain region downstream of a cube-shaped body in a freestream of air flow, properly selected, so that the central limit theorem, when applied to the random velocity increments composing the instantaneous velocity in the wake, roughly holds, and renders the measured signal nearly Gaussian distributed. The statistical distribution of the velocity field in the wake is validated by mapping the first four statistical moments of the measured signals in different regions of the wake and comparing them with corresponding moments of the Gaussian distribution. The experimental data are used to evaluate the sensitivity of the method to the distribution of the measured signal, and the method is demonstrated to possess some robustness with respect to deviations from the Gaussian distribution.
PubDate: 2017-02-11
DOI: 10.1007/s00348-016-2298-2
Issue No: Vol. 58, No. 3 (2017)

• Three-dimensional microscopic light field particle image velocimetry
• Authors: Tadd T. Truscott; Jesse Belden; Rui Ni; Jonathon Pendlebury; Bryce McEwen
Abstract: Abstract A microscopic particle image velocimetry ( $$\mu \text {PIV}$$ ) technique is developed based on light field microscopy and is applied to flow through a microchannel containing a backward-facing step. The only hardware difference from a conventional $$\mu$$ PIV setup is the placement of a microlens array at the intermediate image plane of the microscope. The method combines this optical hardware alteration with post-capture computation to enable 3D reconstruction of particle fields. From these particle fields, we measure three-component velocity fields, but find that accurate velocity measurements are limited to the two in-plane components at discrete depths through the volume (i.e., 2C-3D). Results are compared with a computational fluid dynamics simulation.
PubDate: 2017-02-11
DOI: 10.1007/s00348-016-2297-3
Issue No: Vol. 58, No. 3 (2017)

• Spanwise boundary layer modulations using finite discrete suction for
transition delay
• Authors: Sohrab S. Sattarzadeh; Jens H. M. Fransson
Abstract: Abstract Discrete suction is deployed in a flat plate boundary layer to create spanwise mean velocity gradients (SVG) with the goal of delaying the onset of laminar-to-turbulent transition. It is shown that finite boundary layer suction through a set of holes in a spanwise oriented array in the flat plate is successful in setting up steady and robust streamwise streaks in the boundary layer. Today, the SVG method for transition control is known to attenuate the growth of Tollmien–Schlichting (TS) waves and delay the transition to turbulence. In this investigation, low-amplitude forced TS waves are attenuated with the implication of extending the laminar flow by at least 120% for a discrete suction of 0.8% of the free-stream velocity. The control technique is also tested successfully for natural transition, with a resulting transition delay of 30%.
PubDate: 2017-02-07
DOI: 10.1007/s00348-017-2301-6
Issue No: Vol. 58, No. 3 (2017)

• Surfactant-laden drop jellyfish-breakup mode induced by the Marangoni
effect
• Authors: Hui Zhao; Wen-Bin Zhang; Jian-Liang Xu; Wei-Feng Li; Hai-Feng Liu
Abstract: Abstract Drop breakup is a familiar event in both nature and technology. In this study, we find that the bag breakup mode can be replaced by a new breakup mode: jellyfish breakup, when the surfactant concentration of a surfactant-laden drop is high. This new breakup mode has a morphology resembling a jellyfish with many long tentacles. This is due to the inhomogeneous distribution of surfactant in the process of drop deformation and breakup. The thin film of liquid can remain stable as a result of the Marangoni effect. Finally, we propose that the dimensionless surfactant concentration can serve as a criterion for breakup mechanisms.
PubDate: 2017-02-06
DOI: 10.1007/s00348-016-2296-4
Issue No: Vol. 58, No. 3 (2017)

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