Flow in a double-film-fed fluid bead between contra-rotating rolls, Part 2: bead break and flooding

Two-dimensional flow is considered in a fluid bead located in the gap between a pair of contra-rotating cylinders and bounded by two curved menisci. The stability of such bead flows with two inlet films, and hence no contact line, are analysed as the roll speed ratio S is increased. One of the inlet films can be regarded as an ‘input flux’ whilst the other is a ‘returning film’ whose thickness is specified as a fraction [zeta] of the outlet film on that roll. The flow is modelled via lubrication theory and for Ca [double less-than sign] 1, where Ca represents the capillary number, boundary conditions are formally developed that account for S [not equal] 1 and the non-constant gap. It is shown that there is a qualitative difference in the results between the single and double inlet film models unless small correction terms to the pressure drops at the interfaces are taken into account. Futhermore, it is shown that the inclusion of these small terms produces an O(1) effect on the prediction of the critical value of S at which bead break occurs. When the limits of the returning film fraction are examined it is found that as [zeta] [rightward arrow] 0 results are in good agreement with those for the single inlet film. Further it is shown for a fixed input flux that as [zeta] [rightward arrow] 1 a transition from bead break to upstream flooding of the nip can occur and multiple two-dimensionally stable solutions exist. For a varying input flux and fixed and ‘sufficiently large’ values of [zeta] there is a critical input flux &[lambda]macr;([zeta]) such that as S is increased from zero: (i) bead break occurs for [lambda] < &[lambda]macr;; (ii) upstream flooding occurs for [lambda] > &[lambda]macr;; (iii) when [lambda] = &[lambda]macr; the flow becomes neutrally stable at a specific value of S beyond which there exist two steady solutions (two-dimensionally stable) leading to bead break and upstream flooding, respectively

A model for deformable roll coating with negative gaps and incompressible compliant layers

A soft elastohydrodynamic lubrication model is formulated for deformable roll coating involving two contra-rotating rolls, one rigid and the other covered with a compliant layer. Included is a finite-strip model (FSM) for the deformation of the layer and a lubrication model with suitable boundary conditions for the motion of the fluid. The scope of the analysis is restricted to Newtonian fluids, linear elasticity/viscoelasticity and equal roll speeds, with application to the industrially relevant highly loaded or 'negative gap' regime. Predictions are presented for coated film thickness, interroll thickness, meniscus location, pressure and layer deformation as the control parameters - load (gap), elasticity, layer thickness and capillary number, Ca - are varied. There are four main results: \ud (i) Hookean spring models are shown to be unable to model effectively the deformation of a compliant layer when Poisson's ratio nu --> 0.5. In particular, they fall to predict the swelling of the layer at the edge of the contact region which increases as v - 0.5; they also fail to locate accurately the position of the meniscus, X-M, and to identify the presence, close to the meniscus, of a 'nib' (constriction in gap thickness) and associated magnification of the sub-ambient pressure loop. (ii) Scaling arguments suggest that layer thickness and elasticity may have similar effects on the field variables. It is shown that for positive gaps this is true, whereas for negative gaps they have similar effects on the pressure profile and flow rate yet quite different effects on layer swelling (deformation at the edge of the contact region) and different effects on X-M. (iii) For negative gaps and Ca similar to O(1), the effect of varying either viscosity or speed and hence Ca is to significantly alter both the coating thickness and X-M. This is contrary to the case of fixed-gap rigid roll coating. (iv) Comparison between theoretical predictions and experimental data shows quantitive agreement in the case of X-M and qualitive agreement for flow rate. It is shown that this difference in the latter case may be due to viscoelastic effects in the compliant layer

Baryons in Partially-Quenched Chiral Perturbation Theory

I discuss the inclusion of baryons into partially-quenched chiral perturbation theory and describe one-loop calculations that have been performed.Comment: Lattice2002(matrixel) : talk presented at Lattice 2002, 7 page

Modelling daily net radiation of open water surfaces using land-based meteorological data

Accurate quantification of net irradiance of open water (Rn water) is of paramount importance for the estimation&nbsp; of open water evaporation, which is critical for the efficient management of water resources. Alternatively,&nbsp; model estimates of Rn water are often used when quality measurements of Rn water are not readily available&nbsp; for the water storage of interest. A Daily Penman, Monteith, Equilibrium Temperature Hargreaves-Samani (DPMETHS) model has been developed for the estimation of Rn water using land-based meteorological data. The DPMETHS model is a spreadsheet-based iterative procedure that computes Rn water using daily landbased meteorological measurements of solar irradiance (Rs land), minimum and maximum air temperatures (Tmin and Tmax), minimum and maximum relative humidity (RHmin and RHmax) and average wind speed (Uland). In this study, the DPMETHS model was evaluated using daily Rn water in-situ measurements acquired from 5 sites in both hemispheres, representing very different climatic conditions. Results showed reasonable model performance at all 5 sites, with the coefficient of determination (r2) values greater than 0.85 and root mean square error (RMSE) values ranging from 0.60 MJ∙m-2 for Stratus Ocean (East Pacific Ocean) to 1.89 MJ∙m-2 for Midmar Dam (South Africa). The results of this study suggested that the DPMETHS model can be reliably used to estimate Rn water for a wide range of climatic conditions. The performance of the DPMETHS model depends on the representativeness of the land-based meteorological data to the weather conditions above the open water surface. The DPMETHS model is user-friendly with minimal computational and data requirements that allows easy data handling and visual inspection

SU(3) Predictions for Weak Decays of Doubly Heavy Baryons -- including SU(3) breaking terms

We find expressions for the weak decay amplitudes of baryons containing two b quarks (or one b and one c quark -- many relationship are the same) in terms of unknown reduced matrix elements. This project was originally motivated by the request of the FNAL Run II b Physics Workshop organizers for a guide to experimentalists in their search for as yet unobserved hadrons. We include an analysis of linear SU(3) breaking terms in addition to relationships generated by unbroken SU(3) symmetry, and relate these to expressions in terms of the complete set of possible reduced matrix elements.Comment: 49 page

The linewidth of a non-Markovian atom laser

We present a fully quantum mechanical treatment of a single mode atom laser including pumping and output coupling. By ignoring atom-atom interactions, we have solved this model without making the Born-Markov approximation. We find substantially less gain narrowing than is predicted under that approximation.Comment: 4 pages, 1 encapsulated postscript figur

The Magnetic Moments of the Octet Baryons in Quenched Chiral Perturbation Theory

We compute the magnetic moments of the octet baryons up to two orders in quenched chiral perturbation theory. In addition to the $\sim\sqrt{m_q}$ contributions that arise in QCD, there are lower-order contributions of the form $M_0^2\log m_q$ from loop diagrams involving hairpin interactions.Comment: 18 pages, 3 figures, late

Parity violation in nuclear systems

Parity violation in nuclear systems is reviewed. A few ingredients relevant to the description of the parity-violating nucleon-nucleon force in terms of meson exchanges are reminded. Effects in nuclear systems are then considered. They involve pp scattering, some complex nuclei and the deuteron system.Comment: 4 pages, to be published in the proceedings of the worksho

Two-Body Cabibbo-Suppressed Charmed Meson Decays

Singly-Cabibbo-suppressed decays of charmed particles governed by the quark subprocesses $c \to s u \bar s$ and $c \to d u \bar d$ are analyzed using a flavor-topology approach, based on a previous analysis of the Cabibbo-favored decays governed by $c \to s u \bar d$. Decays to $PP$ and $PV$, where $P$ is a pseudoscalar meson and $V$ is a vector meson, are considered. We include processes in which $\eta$ and $\eta '$ are produced.Comment: 18 pages, latex, 2 figures, to be submitted to Phys. Rev.

Charmless Two-body Baryonic B Decays

We study charmless two-body baryonic B decays in a diagramatic approach. Relations on decay amplitudes are obtained. In general there are more than one tree and more than one penguin amplitudes. The number of independent amplitudes can be reduced in the large m_B limit. It leads to more predictive results. Some prominent modes for experimental searches are pointed out.Comment: 15 pages, 2 figures. To appear in Phys. Rev.