6,849 research outputs found
Fluid boundary of a viscoplastic Bingham flow for finite solid deformations
No full textThe modelling of viscoplastic Bingham fluids often relies on a rheological constitutive law based on a "plastic rule function" often identical to the yield criterion of the solid state. It is also often assumed that this plastic rule function vanishes at the boundary between the solid and fluid states, based on the fact that it is true in the limit of small deformations of the solid state or for simple yield criteria. We show that this is not the case for finite deformations by considering the example of a two state flow on a tilted plane where the solid state is described by a Neo-Hookean model with a Von Mises yield criterion. This opens new approaches for the modelling and the computation of the fluid state boundaries
Non-modal stability in Hagen-Poiseuille flow of a Bingham fluid
No full textLinear stability in Hagen-Poiseuille flow of a Bingham fluid is considered. Bingham fluid exhibits a yield stress in addition to a plastic viscosity. A Bingham number B, which describes the ratio of yield and viscous stresses, is used to characterize the behavior of Bingham-Hagen-Poiseuille flow. The effects of B on the stability are investigated using the energy method and the non-modal stability theory. The energy analysis shows that the non-axisymmetric disturbance has the lowest critical energy Reynolds number for all B. The global critical energy Reynolds number Re-g increases with B. At sufficient large B, Re-g has the order of B-1/2. For the non-modal stability, we focus on response to external excitations and initial conditions. The former is studied by examining the epsilon-pseudospectrum, and the latter is by examining the energy growth function G(t). For the problem of response to external excitations, the maximum response is achieved by non-axisymmetric and streamwise uniform disturbances at the frequency of omega = 0, with a possible choice of the azimuthal wavenumbers of n = 1, 2, or 3. For the problem of response to initial conditions, it is found that there can be a rather large transient growth even though the linear operator of the Bingham-Hagen-Poiseuille flow has no unstable eigenvalue. For small B, the optimal disturbance is in the form of streamwise uniform vortices and streaks. For large B, the optimal disturbance is in the form of oblique waves. The optimal energy growth decreases and the optimal azimuthal wavenumber increases with the increase of B. (C) 2014 AIP Publishing LLC
Estimation and simulation in directional and statistical shape models
No full textThis thesis is concerned with problems in two related areas of statistical shape analysis in two dimensional
landmarks data and directional statistics in various sample spaces.
Directional observations can be regarded as points on the circumference of a circle of unit radius in two
dimensions or on the surface of a sphere in three dimensions. Special directional methods and models are
required which take into account the structure of these sample spaces. Shape analysis involves methods
for the study of the shape of objects where location, scale and orientation are removed. Specifically, we
consider the situation where the objects are summarized by points on the object called landmarks. The
non-Euclidean nature of the shape space causes several problems when defining a distribution on it. Any
distribution which could be considered needs to be tractable and a realistic model for landmark data.
One aim of this thesis is to investigate the saddlepoint approximations for the normalizing constants of
some directional and shape distributions. In particular, we consider the normalizing constant of the CBQ
distribution which can be expressed as a one dimensional integral of normalizing constants for Bingham
distributions. Two new methods are explored to evaluate this normalizing constant based on saddlepoint
approximations namely the Integrated Saddlepoint (ISP) approximation and the Saddlepoint-Integration
(SPI) approximation.
Another objective of this thesis is to develop new simulation methods for some directional and shape
models. We propose an efficient acceptance-rejection simulation algorithm for the Bingham distribution on
unit sphere using an angular central Gaussian (ACG) density as an envelope. This envelope is justified using
inequalities based on concave functions. An immediate consequence is a method to simulate 3 x 3 matrix
Fisher rotation matrices. In addition, a new accept-reject algorithm is developed to generate samples from
the complex Bingham quartic (CBQ) distribution.
The last objective of this thesis is to develop a new moment method to estimate the parameters of the
wrapped normal torus distribution based on the sample sine and cosine moments
Beth R. Robinson, Lucille M. Kina, and Leone C. Bingham
No full textColor photo showing three women, identified as Beth R. Robinson, Lucille M. Kina, and Leone C. Bingham. Possibly friends of Byron A. Hunter. At least one, Leone Bingham, was part of the 50th Anniversary reunion in 1979
Remica Bingham-Risher, 40th Annual ODU Literary Festival
No full textRemica Bingham-Risher, a native of Phoenix, Arizona, is an alumna of Old Dominion University and Bennington College. She is a Cave Canem fellow and Affrilachian Poet. Among other journals, her work has been published in The Writer\u27s Chronicle, New Letters, Callaloo and Essence. She is the author of Conversion (Lotus, 2006) winner of the Naomi Long Madgett Poetry Award, What We Ask of Flesh (Etruscan, 2013) shortlisted for the Hurston/Wright Legacy Award and Starlight & Error (Diode, 2017) winner of the Diode Editions Book Award. She is the Director of Quality Enhancement Plan Initiatives at Old Dominion University and resides in Norfolk with her husband and children
Lubrication theory for Bingham plastics
No full textThe rheological behavior of many lubricants used in hydrodynamic bearings can reasonably be modeled using the Bingham plastic material model. This behavior is characterized by a strong discontinuity, from a pure solid state to a viscous fluid state depending on the local shear stress. In literature three methods have been presented to model a Bingham plastic lubricated film. A full CFD and thus expensive, numerical simulation has been used. A general Reynolds equation based simulation has been used, however with a less accurate numerical regularization of the material discontinuity. Or a general Reynolds equation based simulation has been used, but with a severe reduction of the geometric complexity. In this paper, an ’exact’ thin film lubrication simulation for a Bingham plastic fluid is presented. The model is said to be exact in the sense that it requires no additional approximations to those used in the derivation of the general Reynolds equation, and requires no numerical regularization of the Bingham plastic fluid model and can still be used on any lubricating film geometry. Simulations on both infinite and finite journal bearings shows that the results of this new method are in good accordance with literature, demonstrating the validity of the method.Mechatronic Systems Desig
Remica Bingham-Risher: 47th Annual ODU Literary Festival
No full textRemica Bingham-Risher, a native of Phoenix, Arizona, is a Cave Canem fellow and Affrilachian Poet. Her work has been published in The New York Times, The Writer’s Chronicle, Callaloo and Essence. She is the author of Conversion (Lotus, 2006), winner of the Naomi Long Madgett Poetry Award; What We Ask of Flesh (Etruscan, 2013), shortlisted for the Hurston/Wright Legacy Award; and Starlight & Error (Diode, 2017), winner of the Diode Editions Book Award and finalist for the Library of Virginia Book Award. Her memoir, Soul Culture: Black Poets, Books and Questions That Grew Me Up, was published by Beacon Press (2022). Her newest book, Room Swept Home, is a work of poems, historical and family photographs (Wesleyan University Press, 2024). She is the Director of Quality Enhancement Plan Initiatives at Old Dominion University in Norfolk, VA, where she resides with her husband and children
Remica Bingham-Risher,45th Annual ODU Literary Festival
No full textRemica Bingham-Risher, a native of Phoenix, Arizona, is a Cave Canem fellow and Affrilachian Poet. Her work has been published in The New York Times, The Writer\u27s Chronicle, Callaloo and Essence. She is the author of Conversion (Lotus, 2006) winner of the Naomi Long Madgett Poetry Award, What We Ask of Flesh (Etruscan, 2013) shortlisted for the Hurston/Wright Legacy Award and Starlight & Error (Diode, 2017) winner of the Diode Editions Book Award and finalist for the Library of Virginia Book Award. Her book Soul Culture: Black Poets, Books and Questions That Grew Me Up was published by Beacon Press In August 2022. She is the Director of Quality Enhancement Plan Initiatives at Old Dominion University in Norfolk, VA, where she resides with her husband and children
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