An experimental and numerical investigation into flow phenomena leading to wastewater centrifugal pump blockage

The work covered in this paper had the objective of investigating key factors in single vane pump impeller blockage using both CFD and experimental analysis. Single vane centrifugal pumps can be found in wastewater applications, where suspended solids, fibers and other flexible material can build up on the pump impeller and cause blockage and failure. It is in the pump manufacturer’s interest to design blockage resistant components while still maintaining hydraulic efficiency. Testing was conducted on a large variety of centrifugal wastewater pumps at different operating points in a purpose built test rig with suitable test material. A pump which had varying blockage performance depending on operating point was chosen for further study with CFD. Transient simulations with the SA-DDES turbulence model were carried out with the same operating conditions as in the experimental analysis. CFD has been used to highlight flow features likely to lead to such blockage, while experiments provided some insight into the significance of certain key parameters. An analysis of the CFD results showed a significant correlation between pump blockage performance and radial velocity components within the fluid domain, specifically in the impeller region. Sensitivity to blockage was found to vary with the head required of the pump. This sensitivity was further explained when applying the hypothesis of the impact of velocity components on the likelihood of pump blockage.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

A coupled lattice boltzmann - immersed boundary method to model the behaviour of thin flexible structures in fluids

This article presents a computational model to simulate the fluid interaction with moving flexible thin structures. The model is based on a combination of three numerical approaches, (i) a Lattice-Boltzmann solver for the flow equations, (ii) a finite difference method to solve the solid equation, and (iii) an Immersed Boundary Method (IBM) to model the coupling between the fluid and the solid. The present IBM, based on a direct-forcing approach, preserves the no-slip boundary condition at the interface fluid-solid, and allows using Cartesian uniform lattice encompassing both fluid and solid domains. The flexible solid is modelled as an elastic structure. The resulting governing equation involves thus tension and bending forces as internal forces, the inertial and gravity forces and finally the action of the fluid represented by the IBM forcing. The method is first validated with reference to an academic test case dealing with numerical simulations of a flapping flag in a free stream. The model shows results in good agreement with the published academic test case. The validation extends to the free motion of rag in a water tunnel and a qualitative comparison is available against experimental data performed with Digital Image Correlation (DIC). Finally, the present method is used to simulate the behaviour of flexible rags in the presence of highly rotating flows at high Reynolds number, as it is the case in stirred tanks.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

The WITCH experiment: completion of a set-up to investigate the structure of weak interactions with a Penning trap

The WITCH experiment aims to study a possible admixture of a scalar or tensor type interaction in beta decay by determining the beta-neutrino angular correlation from the shape of the recoil energy spectrum. The installation period was completed and intensive commissioning of the set-up was performed already. The lay-out of the WITCH set-up and results of commissioning tests performed until now are described here, showing that the full set-up up to the spectrometer is now operational, although several efficiencies are still to be improved. Due to its feature of being able to measure the energy spectrum for recoil ions, the WITCH experiment also opens possibilities for other observables.Comment: 31 pages, 18 figures. International Journal of Mass Spectrometry, in pres

ATL9, a RING Zinc Finger Protein with E3 Ubiquitin Ligase Activity Implicated in Chitin- and NADPH Oxidase-Mediated Defense Responses

Pathogen associated molecular patterns (PAMPs) are signals detected by plants that activate basal defenses. One of these PAMPs is chitin, a carbohydrate present in the cell walls of fungi and in insect exoskeletons. Previous work has shown that chitin treatment of Arabidopsis thaliana induced defense-related genes in the absence of a pathogen and that the response was independent of the salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) signaling pathways. One of these genes is ATL9 ( = ATL2G), which encodes a RING zinc-finger like protein. In the current work we demonstrate that ATL9 has E3 ubiquitin ligase activity and is localized to the endoplasmic reticulum. The expression pattern of ATL9 is positively correlated with basal defense responses against Golovinomyces cichoracearum, a biotrophic fungal pathogen. The basal levels of expression and the induction of ATL9 by chitin, in wild type plants, depends on the activity of NADPH oxidases suggesting that chitin-mediated defense response is NADPH oxidase dependent. Although ATL9 expression is not induced by treatment with known defense hormones (SA, JA or ET), full expression in response to chitin is compromised slightly in mutants where ET- or SA-dependent signaling is suppressed. Microarray analysis of the atl9 mutant revealed candidate genes that appear to act downstream of ATL9 in chitin-mediated defenses. These results hint at the complexity of chitin-mediated signaling and the potential interplay between elicitor-mediated signaling, signaling via known defense pathways and the oxidative burst

Fundamental weak interaction studies using polarised nuclei and ion traps

Two experiments to search for new physics beyond the standard model for electroweak interactions by measuring correlations between different spin and momentum vectors in nuclear beta -decay are discussed. In the first experiment the correlation between the emission asymmetry and the longitudinal polarisation of positrons emitted by polarised nuclei is determined. This type of measurement is sensitive to the presence of right-handed currents but also to possible scalar and tensor-type currents in the weak interaction. The aim of the second experiment is to determine the beta nu -correlation in beta -decay by measuring the energy spectrum of the recoil ions, using a Penning trap and a retardation spectrometer. In this case the focus is on the search for scalar currents in the weak interaction. The results of the experiments presented here are complementary to results from experiments in muon decay and at high-energy colliders

WITCH: A Penning trap retardation spectrometer combination for precision studies of the weak interaction

The Weak Interaction Trap for CHarged particles (WITCH) setup is being installed at the ISOLDE-facility (CERN) to test the Standard Model of the electroweak interaction. This will be done by searching for scalar and tensor admixtures in nuclear beta decay. The beta-neutrino angular correlation is an excellent probe to determine the possible strength of those non-Standard Model contributions. The WITCH setup combines the unique storage features of a Penning trap to produce a scattering free radioactive source with a retardation spectrometer to measure the recoil energy spectrum of the daughter nuclei after beta decay with high precision. Physics beyond the Standard Model would lead to deviations from the expected spectral shape

Magnetic moment of Ag-104(m) and the hyperfine magnetic field of Ag in Fe using nuclear magnetic resonance on oriented nuclei

Nuclear magnetic resonance (NMR/ON) measurements with beta- and gamma-ray detection have been performed on oriented Ag-104(g,m) nuclei with the NICOLE He-3-He-4 dilution refrigerator setup at ISOLDE/CERN. For Ag-104(g) (I-pi = 5(+)) the gamma-NMR/ON resonance signal was found at nu = 266.70(5) MHz. Combining this result with the known magnetic moment for this isotope, the magnetic hyperfine field of Ag impurities in an Fe host at low temperature (< 1 K) is found to be vertical bar B-hf(AgFe)vertical bar = 44.709(35) T. A detailed analysis of other relevant data available in the literature yields three more values for this hyperfine field. Averaging all four values yields a new and precise value for the hyperfine field of Ag in Fe; that is, vertical bar B-hf(AgFe)vertical bar = 44.692(30) T. For Ag-104(m) (I-pi = 2(+)), the anisotropy of the beta particles provided the NMR/ON resonance signal at nu = 627.7(4) MHz. Using the new value for the hyperfine field of Ag in Fe, this frequency corresponds to the magnetic moment mu(Ag-104m) = +3.691(3) mu(N), which is significantly more precise than previous results. The magnetic moments of the even-A Ag102 -110 isotopes are discussed in view of the competition between the (pi g(9/2))(7/2+)(-3)(nu d(5/2)nu g(7/2))(5/2+) and the (pi g(9/2))(9/2+)(-3)(nu d(5/2)nu g(7/2))(5/2+) configurations. The magnetic moments of the ground and isomeric states of Ag-104 can be explained by an almost complete mixing of these two configurations

Search for new physics in beta-neutrino correlations with the WITCH spectrometer

The WITCH (Weak Interaction Trap for CHarged particles) experiment is a retardation spectrometer coupled to a Penning trap and measures the beta-neutrino angular correlation via the shape of the recoil energy spectrum. The present form of the Standard Model describes weak processes in terms of vector and axial-vector type interactions, but the possible presence of scalar and tensor interactions is not yet ruled out. The main aim of this experiment is a test of the Standard Model for possible admixture of scalar and tensor currents. (C) 2002 Elsevier Science B.V. All rights reserved