57,293 research outputs found
An Analytical Criterion for Centrifugal Instability in Non-Axisymmetric Vortices
No full textNon-axisymmetric vortices are ubiquitous in nature; examples include polar vortices in planets, the giant red spot in Jupiter, tornadoes and cyclones on Earth, mesoscale eddies in the ocean. Turbulent flows are furthermore known to be dominated by small- and large-scale vortex structures. Owing to the wide range of applications, knowledge of conditions under which a given vortex becomes unstable is beneficial. Here, the centrifugal instability of two-dimensional, non-axisymmetric vortices in the presence of an axial flow and a background rotation is studied using the local stability approach. The local stability approach, based on geometric optics and similar in formulation to the rapid distortion theory \cite{bib:godeferd2001}, considers the evolution of shortwavelength perturbations along streamlines in the base flow. This approach, developed by Lifschitz Hameiri \cite{bib:lifschitz1991}, is particularly useful for base flows for which a global stability analysis is computationally expensive. A sufficient criterion for centrifugal instability in an axisymmetric vortex with and is first derived by analytically solving the local stability equations for wave vectors that are periodic upon evolution around a closed streamline. This criterion is then heuristically extended to non-axisymmetric vortices and written in terms of integral quantities on a streamline. The criterion is then shown to be accurate in describing centrifugal instability over a reasonably large range of parameters that specify Stuart vortices and Taylor-Green vortices
FINANCING COMMUNITY FACILITIES: A CASE STUDY OF THE PARKS AND RECREATIONAL GENERAL OBLIGATION BOND MEASURE OF SAN JOSE, CALIFORNIA
Get PDFThis study of the City of San Jose’s Parks and Recreation General Obligation (GO) Bond Measure seeks to identify the politics-, management-, and planning-related lessons learned by the City as it developed its community facilities using the GO bonds proceeds. The study finds that these lessons include: be conservative in what you promise the residents; be prepared for changes in economic environment by identifying supplementary funding sources should the primary source not yield adequate funds; make sure that the jurisdiction is organizationally capable of handling the increased workload; and prepare detailed project plans prior to the bond issuance.Community Infrastructure and Services; Municipal Bonds; Public Finance
A Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
Japanese Encephalitis Virus Latency Following Congenital Infection in Mice
Get PDFLatent Japanese encephalitis virus (JEV) infection was shown in inapparently congenitally infected Swiss albino mice after their mothers had been given JEV intraperitoneally during pregnancy. Only one of 37 (2-7%) of the baby mice showed persistence of infectious virus at 5 weeks of age. Reactivation of JEV in Swiss albino mice was demonstrated by stimulation with allogeneic spleen cells from Parks strain mice at 21 weeks of age; reactivation was demonstrated in 41 % of the inapparently infected mice. The spleen cells of congenitally infected mice had depressed [3H]thymidine uptake following stimulation with concanavalin A, and depressed ability to induce a graft-versus-host response. A persistent infection followed by a latent infection with Japanese encephalitis virus (JEV) has been observed in Swiss albino mice (Mathur et al., 1982). The latent virus could be activated by giving cyclophosphamide even 1 year after infection (Mathur et al., 1986). Abortion or congenital infection can occur when mice are infected with JEV during pregnancy (Mathur et al., 1981; Sugamata & Miura, 1982) and similar effects of JEV infection have been observed at different periods of gestation in human cases (Chaturvedi et al., 1980; Mathur et al., 1985)
Near Wall PIV-Measurements on the Windward Slope of a Hill
No full textThe turbulent flow over periodic hills was measured near to the wall, using planar Particle-Image-Velocimetry (PIV) at high spatial resolution. Our focus is on the near wall turbulence structure on the windward slope of the hill. For large-eddy simulation (LES) we suspect that, if this was not predicted accurately, it affects the prediction of the velocity profiles over the hill crest which in turn will affect the recirculation length downstream of the hill. Regarding the time averaged velocities, we were able to resolve the linear viscous region of the boundary layer. The velocity distribution and also the Reynolds stress does not comply with the law of the wall as it is valid for a turbulent boundary layer at equilibrium
Uncovering a novel role for FXR-SHP axis in liver physiology, diseases and beyond
Get PDFLiver performs a multitude of functions ranging from detoxification, metabolism and digestion. To execute these tasks, one of the mechanisms that the liver utilizes is nuclear receptor signaling, which in turn can transcriptionally regulate gene networks. My doctoral thesis focuses on studying the role of two nuclear receptors, FXR and SHP in maintaining liver function. Farnesoid X Receptor (FXR) and Small Heterodimer Partner (SHP) are well-known regulators of glucose, fat and bile acid homeostasis. Here, I uncover novel roles for FXR-SHP axis not only in the liver but also in extrahepatic organs, like heart. In Chapter 2, I discuss how hepatic loss of FXR and SHP results in increased glycosylation of liver proteins and structural defects in Golgi apparatus, and ultimately liver cancer. Chapter 3 focuses on comprehending how FXR-SHP ablation results in increased drug metabolic capacity of the liver. Finally, chapter 4 discusses how liver dysfunction, caused by loss of FXR and SHP, can induce metabolic and functional defects in heart. Taken together, these projects will help understand some of the FXR and SHP transcriptional networks under different physiological and pathological contexts and may open avenues for pharmacological manipulation to treat various diseases.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-08-01The student, Bhoomika Mathur, accepted the attached license on 2019-07-04 at 01:18.The student, Bhoomika Mathur, submitted this Dissertation for approval on 2019-07-04 at 01:31.This Dissertation was approved for publication on 2019-07-09 at 15:41.DSpace SAF Submission Ingestion Package generated from Vireo submission #14170 on 2019-11-26 at 13:04:27Made available in DSpace on 2019-11-26T20:49:21Z (GMT). No. of bitstreams: 3
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Previous issue date: 2019-07-09Embargo set by: Seth Robbins for item 112930
Lift date: 2021-11-26T20:49:41Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 112930 on 2021-11-27T10:15:09Z
Energy dissipation and flux laws for unsteady turbulence
No full textDirect Numerical Simulations of spatially periodic unsteady turbulence show that the high Reynolds number scalings of the instantaneous energy dissipation rate and interscale energy flux at intermediate wavenumbers are qualitatively different from the well-known cornerstone scalings of equilibrium turbulence where and are time-dependent rms velocity and integral length-scales. Instead, they both scale as where and are length and velocity scales characterizing initial/overall unsteady turbulence conditions
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Real-space Manifestations of Bottlenecks in Turbulence Spectra
No full textAn energy-spectrum bottleneck, a bump in the turbulence spectrum between the inertial and dissipation ranges, is shown to occur in the non-turbulent, one-dimensional, hyperviscous Burgers equation and found to be the Fourier-space signature of oscillations in the real-space velocity, which are explained by boundary-layer-expansion techniques. Pseudospectral simulations are used to show that such oscillations occur in velocity correlation functions in one- and three-dimensional hyperviscous hydrodynamical equations that display genuine turbulence
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