Topic
Velocity gradient
About: Velocity gradient is a research topic. Over the lifetime, 3013 publications have been published within this topic receiving 77120 citations.
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TL;DR: In this paper, numerical methods are presented for interpolating a velocity profile and evaluating the ray integrals which avoid discontinuities in the velocity gradient and anomalous geometrical ray amplitudes.
Abstract: The usual methods of interpolating velocity-depth profiles cause discontinuities in the velocity gradient and anomalous geometrical ray amplitudes. Numerical methods are presented for interpolating a velocity profile and evaluating the ray integrals which avoid these difficulties. They allow smooth amplitude curves to be calculated directly. An example is given for the Herrin P velocity profile.
25 citations
TL;DR: In this article, a finite element simulation was developed for the compression molding of thin and thick parts based on Barone and Caulk's model and a generalized variational functional.
Abstract: Based on Barone and Caulk's model and a generalized variational functional, a finite element simulation was developed for the compression molding of thin and thick parts. For solving the u-v-p type equations, an element-based penalty method and a mixed formulation were implemented. Numerical results show that the new model gives better accuracy in velocity and velocity gradient than the Hele-Shaw formulation for cases where both models are appropriate. Predictions of velocity and its gradient by the model are compared with other FEM results and BEM solutions. Using a fixed base mesh that covers the mold cavity, a new technique was developed for tracking the moving flow front. Temporary elements and nodes are generated for the filled part of elements intersected by the flow front. This method allows a smooth representation of the flow front and has exact boundary conditions on the flow front. The scheme is demonstrated for compression molding of an elliptical and an L-shaped charge.
25 citations
TL;DR: Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction.
Abstract: A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.
25 citations
TL;DR: In this paper, the effect of free-stream velocity profiles on the transition from laminar to turbulent flow on a flat plate was studied experimentally and numerically and it was shown that a recirculation region of the flow occurred near the flat plate wall that led to transition dominated by the boundary layer separation.
25 citations
TL;DR: In this paper, the authors presented a theoretical solution for the three-dimensional velocity field into a flanged circular hood, and compared the results with velocity contours obtained by DallaValle.
Abstract: The empirically derived equation for the centerline velocity gradient of a flanged circular inlet, obtained by DallaValle in the 1930s, is still used today as a basis for local exhaust design This paper presents a theoretical solution for the three-dimensional velocity field into a flanged circular hood, and compares the results with velocity contours obtained by DallaValle A simple and easily-used equation is derived for computing the velocity at any point under the influence of the hood
25 citations