The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Richard M. Lueptow - One of the best experts on this subject based on the ideXlab platform.
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Velocity field for Taylor–Couette flow with an axial flow
Physics of Fluids, 1999Co-Authors: Steven T. Wereley, Richard M. LueptowAbstract:The flow in the gap between an inner rotating cylinder concentric with an outer stationary cylinder with an imposed pressure-driven axial flow was studied experimentally using particle image velocimetry (PIV) in a Meridional Plane of the annulus. The radius ratio was η=0.83 and the aspect ratio was Γ=47. Velocity vector fields for nonwavy toroidal and helical vortices show the axial flow winding around vortices. When the axially averaged axial velocity profile is removed from the velocity field in a Meridional Plane, the velocity field looks much like it would with no imposed axial flow except that the vortices translate axially and the distortion of the azimuthal velocity contours in Meridional Plane related to the vortices is shifted axially by the axial flow. The velocity vector fields for wavy vortices also show axial flow winding around the vortices. Again, removing the axial velocity profile results in a flow that appears similar to that with no axial flow. The path of the vortices is generally axial, but the vortices periodically move retrograde to the imposed axial flow due to the waviness of the vortices. The axial velocity of helical vortices, both nonwavy and wavy, is twice the rotational frequency of the inner cylinder indicating a coupling between the axial translation of the vortices and the cylinder rotation. Little fluid transport between vortices occurs for nonwavy vortices, but there is substantial transport between vortices for wavy vortex flow, much like supercritical cylindrical Couette flow with no axial flow.
Marie Oshima - One of the best experts on this subject based on the ideXlab platform.
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Experimental study on swirling flow of dilute surfactant solution with deformed free-surface
Experimental Thermal and Fluid Science, 2008Co-Authors: Yong Dong, Yasuo Kawaguchi, Marie OshimaAbstract:Abstract An experimental investigation was performed on a swirling flow of dilute surfactant solution with deformed free-surface in a cylindrical container driven by the constantly rotating bottom wall. The purpose of the experiment was to estimate weak viscoelasticity in the tested surfactant solutions as well as to investigate the flow characteristics. The tested fluid was an aqueous solution of CTAC (CTAC: cetyltrimethyl ammonium chloride), which is a cationic surfactant. Water, 40 ppm, 60 ppm and 200 ppm CTAC solution flows were tested at Froude numbers ranging from 2.59 to 16.3. Particle image velocimetry (PIV) was used to measure the secondary velocity field in the Meridional Plane. The deformed free-surface level was extracted from the PIV images. At a similar Froude number, the depth of the dip formed at the center region of the free surface was decreased for CTAC solution flow compared with water flow. The inertia-driven vortex at the up-right corner in the Meridional Plane becomes more and more weakened with increase of the solution concentration or viscoelasticity. Through analyzing the overall force balance compared with water flow, the first normal stress difference characterizing the viscoelasticity was estimated for the dilute CTAC solution flows. The result supports the viscoelasticity-based turbulent drag-reduction mechanism of surfactant solution flow.
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Experimental Study of Swirling Flow of a Viscoelastic Fluid With Deformed Free Surface
Volume 1: Symposia Parts A and B, 2006Co-Authors: Masamichi Oishi, Yasuo Kawaguchi, Nobuyuki Oshima, Marie OshimaAbstract:An experimental investigation was performed on the swirling flow of viscoelastic fluid with deformed free surface in a cylindrical container driven by the constantly rotating bottom wall. The tested fluid was an aqueous solution of CTAC (cetyltrimethyl ammonium chloride), which is a cationic surfactant. Water, 40ppm, 60ppm and 200ppm CTAC solution flows were tested at Froude numbers ranging from 2.59 to 16.3. PIV was used to measure the secondary velocity field in the Meridional Plane and the deformed free-surface level was extracted from the PIV images. At a similar Froude number, the depth of the dip formed at the center region of the free surface was decreased for CTAC solution flow compared with water flow. The inertia-driven vortex at the up-right corner in the Meridional Plane becomes more and more weakened with increase of the solution concentration or viscoelasticity. Through analyzing the overall force balance compared with water flow, the first normal stress difference or the weak viscoelasticity was estimated for the dilute CTAC solution flows.Copyright © 2006 by ASME
Philip L. Marston - One of the best experts on this subject based on the ideXlab platform.
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Bistatic specular reflection by a rigid cone.
Journal of the Acoustical Society of America, 2008Co-Authors: Philip L. MarstonAbstract:It is possible to gain some insight into the high‐frequency scattering of sound by objects in water by considering the presence or absence of rays constructed from geometric considerations. This presentation concerns the evolution of rays reflected from the sides of a vertical rigid cone for the case of illumination by a Plane wave at an arbitrary grazing angle. The grazing angle with respect to a horizontal Plane is usually taken to be small. The direction of the reflected rays depends on where the incident ray contacts the cone as specified by an azimuthal angle viewed from above. Define the Meridional Plane as that Plane which contains the incident wave vector and the axis of the cone. Incident rays offset from the Meridional Plane can be reflected with relatively small vertical components in their wave vector. This analysis has implications for how bistatic hydrophones may be deployed to detect specular glints from cone‐shaped objects. There may also be implications for understanding the high‐frequenc...
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Bistatic specular reflection by a rigid cone.
The Journal of the Acoustical Society of America, 2008Co-Authors: Philip L. MarstonAbstract:It is possible to gain some insight into the high‐frequency scattering of sound by objects in water by considering the presence or absence of rays constructed from geometric considerations. This presentation concerns the evolution of rays reflected from the sides of a vertical rigid cone for the case of illumination by a Plane wave at an arbitrary grazing angle. The grazing angle with respect to a horizontal Plane is usually taken to be small. The direction of the reflected rays depends on where the incident ray contacts the cone as specified by an azimuthal angle viewed from above. Define the Meridional Plane as that Plane which contains the incident wave vector and the axis of the cone. Incident rays offset from the Meridional Plane can be reflected with relatively small vertical components in their wave vector. This analysis has implications for how bistatic hydrophones may be deployed to detect specular glints from cone‐shaped objects. There may also be implications for understanding the high‐frequency scattering by conical seamounts in deep water. [Research supported by ONR.]
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Scattering enhancements for penetrable tilted circular cylinders in water: The computed evolution away from the Meridional Plane
The Journal of the Acoustical Society of America, 1999Co-Authors: Philip L. Marston, Florian J. BlonigenAbstract:Significant contributions to the high‐frequency backscattering by penetrable bluntly truncated solid circular cylinders include Meridional leaky Rayleigh waves [K. Gipson, Ph.D. thesis, Washington State University (1998)] and the caustic merging transition [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. 102, 3088 (1997)]. The latter is important for plastic objects (where Rayleigh waves become subsonic relative to water) and is associated with merging transmitted and internally reflected rainbow rays. One way to explore the dependence of these processes on tilt is to compute the exact scattering by infinite circular cylinders away from the Meridional Plane. The Meridional Rayleigh‐wave feature for infinite metallic cylinders is a dip in the total scattering and a peak in the background‐subtracted scattering [P. L. Marston, J. Acoust. Soc. Am. 102, 358–369 (1997)]. We find it evolves in a way bounded by the locus of those rays reflected with their local angle of incidence matching the Rayleigh‐wave coupling angle. In the caustic merging case, the evolution of the rainbow enhancement is similar to optical observations [Mount et al., Appl. Opt. 37, 1534–1539 (1998)]. [Supported by the Office of Naval Research.]
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bravais effective refractive index for tilted plastic cylinders and the caustic merging transition in the Meridional Plane demonstration of an optical analogy
Journal of the Acoustical Society of America, 1997Co-Authors: Philip L. Marston, Catherine M. Mount, David B. ThiessenAbstract:Some solid scatterers in water such as plastic cylinders do not support leaky Rayleigh waves because the shear wave velocity of the solid is less than the speed of sound in water. The high‐frequency scattering from such objects is generally weak. In that case the ray diagram for transmitted shear waves is analogous to the refraction of light by an object in air. For a tilted cylindrical object, the projection of rays on a base Plane may be determined by ignoring the tilt by replacing the true refractive index n by the Bravais value (n2−sin2γ)1/2/cosγ where γ is the tilt. For a circular cylinder, when the Bravais value reaches 2, the rainbow caustics merge in the Meridional Plane defined by the incident wave vector and the cylinder’s axis [C. M. Mount and P. L. Marston, in Light and Color in the Open Air (OSA, Washington, DC, 1997), pp. 14–16]. The merged caustics greatly enhance the scattering because of the far‐field focusing of a cusp point. The analysis is also relevant to light scattering by icicles a...
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Bravais effective refractive index for tilted plastic cylinders and the caustic‐merging transition in the Meridional Plane: Demonstration of an optical analogy
The Journal of the Acoustical Society of America, 1997Co-Authors: Philip L. Marston, Catherine M. Mount, David B. ThiessenAbstract:Some solid scatterers in water such as plastic cylinders do not support leaky Rayleigh waves because the shear wave velocity of the solid is less than the speed of sound in water. The high‐frequency scattering from such objects is generally weak. In that case the ray diagram for transmitted shear waves is analogous to the refraction of light by an object in air. For a tilted cylindrical object, the projection of rays on a base Plane may be determined by ignoring the tilt by replacing the true refractive index n by the Bravais value (n2−sin2γ)1/2/cosγ where γ is the tilt. For a circular cylinder, when the Bravais value reaches 2, the rainbow caustics merge in the Meridional Plane defined by the incident wave vector and the cylinder’s axis [C. M. Mount and P. L. Marston, in Light and Color in the Open Air (OSA, Washington, DC, 1997), pp. 14–16]. The merged caustics greatly enhance the scattering because of the far‐field focusing of a cusp point. The analysis is also relevant to light scattering by icicles a...
Steven T. Wereley - One of the best experts on this subject based on the ideXlab platform.
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Velocity field for Taylor–Couette flow with an axial flow
Physics of Fluids, 1999Co-Authors: Steven T. Wereley, Richard M. LueptowAbstract:The flow in the gap between an inner rotating cylinder concentric with an outer stationary cylinder with an imposed pressure-driven axial flow was studied experimentally using particle image velocimetry (PIV) in a Meridional Plane of the annulus. The radius ratio was η=0.83 and the aspect ratio was Γ=47. Velocity vector fields for nonwavy toroidal and helical vortices show the axial flow winding around vortices. When the axially averaged axial velocity profile is removed from the velocity field in a Meridional Plane, the velocity field looks much like it would with no imposed axial flow except that the vortices translate axially and the distortion of the azimuthal velocity contours in Meridional Plane related to the vortices is shifted axially by the axial flow. The velocity vector fields for wavy vortices also show axial flow winding around the vortices. Again, removing the axial velocity profile results in a flow that appears similar to that with no axial flow. The path of the vortices is generally axial, but the vortices periodically move retrograde to the imposed axial flow due to the waviness of the vortices. The axial velocity of helical vortices, both nonwavy and wavy, is twice the rotational frequency of the inner cylinder indicating a coupling between the axial translation of the vortices and the cylinder rotation. Little fluid transport between vortices occurs for nonwavy vortices, but there is substantial transport between vortices for wavy vortex flow, much like supercritical cylindrical Couette flow with no axial flow.
Tony Wilson - One of the best experts on this subject based on the ideXlab platform.
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real time slit scanning microscopy in the Meridional Plane
Optics Letters, 2009Co-Authors: Edward J Botcherby, Martin J Booth, R Juskaitis, Tony WilsonAbstract:The standard microscope architecture around which confocal microscopes are built imposes fundamental restrictions on the speed with which images (three-dimensional data sets) can be obtained. Commercially available slit scanning confocal microscopes are able to produce optically sectioned images at frame rates well in excess of 100 Hz. However only the focal (x−y) Plane can be imaged at this speed. To image a volume specimen it is necessary to physically change the distance between the objective lens and the specimen. This refocusing process is often necessarily slow and represents a bottleneck to the speed of image acquisition. We describe the construction of a slit scanning confocal microscope based on what we know to be a novel microscope architecture, which permits images of other Planes and, particular, the Meridional (x−z) Plane to be acquired in real time.