3,045 research outputs found

    Cavitating propeller flows predicted by RANS solver with structured grid and small reynolds number turbulence model approach

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    Within the EU research project VIRTUE, a propeller is investigated in uniform and nonuniform inflow conditions by means of a RANS equation solver, FINFLO. The analyses are made in wetted and cavitating conditions. The propeller analyzed in this paper is the INSEAN E779A propeller. The paper contains calculations at three different grid resolutions in wetted conditions and at the two finest grid resolutions in cavitating conditions in uniform inflow. The mediumsize grid is used for the propeller in nonuniform inflow simulations. The simulations are conducted on a model scale and the results are compared with the measurements and cavitation tests performed by INSEAN. The nonuniform inflow is generated by modeling the geometry of the artificial wake generator used in the cavitation tests in the calculation domain. The experimental results are published in several papers, for example in [1] and [2]. The predicted propeller open water thrust and torque are found to be within 5 % of the measured ones. The pressure peak at the leading edge of a blade is found to be sensitive to the grid resolution. The predicted cavitation behavior of the propeller blades is in reasonable accordance with the cavitation test observations. In uniform inflow the vaporized region is overpredicted. Contrastingly, the vaporized region is Underpredicted in the nonuniform inflow calculations. Side entrant jets could be identified in the cavity region in the nonuniform inflow simulations. The predicted vaporized regions in several blade positions together with photographs of the cavitating propeller are shown for comparison. The cavitation behavior trends seemed to be similar in the simulations and observations in nonuniform inflow, except that the rollup of detached sheet cavitation into a tip vortex could not be captured in the calculations. The total wake is measured between the propeller plane and the wake generator. The predicted wake is found to be too strong, but the width of the wake is relatively close to the measurements. The propeller loading history is shown over one propeller revolution. It shows qualitatively reasonable trends. The loading histories of the wetted and cavitating propeller are almost the same due to the relative small cavitating region in the investigated conditions. The pressure distributions at several blade positions on the suction side of the propeller are shown in wetted and cavitating conditions for comparison.http://deepblue.lib.umich.edu/bitstream/2027.42/84244/1/CAV2009-final45.pd

    Measurement of electroweak WZ boson production and search for new physics in WZ plus two jets events in pp collisions at root s=13 TeV

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    A measurement of WZ electroweak (EW) vector boson scattering is presented. The measurement is performed in the leptonic decay modes WZ -> l nu l'l', where l, l' = e, mu. The analysis is based on a data sample of proton-proton collisions at root s = 13 TeV at the LHC collected with the CMS detector and corresponding to an integrated luminosity of 35.9 fb(-1) . The WZ plus two jet production cross section is measured in fiducial regions with enhanced contributions from EW production and found to be consistent with standard model predictions. The EW WZ production in association with two jets is measured with an observed (expected) significance of 2.2 (2.5) standard deviations. Constraints on charged Higgs boson production and on anomalous quartic gauge couplings in terms of dimension-eight effective field theory operators are also presented. (C) 2019 The Author(s). Published by Elsevier B.V.Peer reviewe

    Study of jet quenching with isolated-photon plus jet correlations in PbPb and pp collisions at root s(NN)=5.02 TeV

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    Measurements of azimuthal angle and transverse momentum (p(T)) correlations of isolated photons and associated jets are reported for pp and PbPb collisions at root s(NN) = 5.02 TeV. The data were recorded with the CMS detector at the CERN LHC. For events containing a leading isolated photon with p(T)(gamma) > 40 GeV/c and an associated jet with p(T)(jet) > 30 GeV/c, the photon+jet azimuthal correlation and p(T) imbalance in PbPb collisions are studied as functions of collision centrality and p(T)(gamma). The results are compared to pp reference data collected at the same collision energy and to predictions from several theoretical models for parton energy loss. No evidence of broadening of the photon+jet azimuthal correlations is observed, while the ratio p(T)(jet)/p(T)(gamma) decreases significantly for PbPb data relative to the pp reference. All models considered agree within uncertainties with the data. The number of associated jets per photon with p(T)(gamma) > 80GeV/c is observed to be shifted towards lower p(T)(jet) in central PbPb collisions compared to pp collisions. (C) 2018 The Author. Published by Elsevier B.V.Peer reviewe

    Search for Z gamma resonances using leptonic and hadronic final states in proton-proton collisions at root s=13 TeV

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    A search is presented for resonances decaying to a Z boson and a photon. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), and collected with the CMS detector at the LHC in 2016. Two decay modes of the Z boson are investigated. In the leptonic channels, the Z boson candidates are reconstructed using electron or muon pairs. In the hadronic channels, they are identified using a large-radius jet, containing either light-quark or b quark decay products of the Z boson, via jet substructure and advanced b quark tagging techniques. The results from these channels are combined and interpreted in terms of upper limits on the product of the production cross section and the branching fraction to Z gamma for narrow and broad spin-0 resonances with masses between 0.35 and 4.0 TeV, providing thereby the most stringent limits on such resonances.Peer reviewe

    Combined search for electroweak production of charginos and neutralinos in proton-proton collisions at root s=13 TeV

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    A statistical combination of several searches for the electroweak production of charginos and neutralinos is presented. All searches use proton-proton collision data at A root s = 13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb(-1). In addition to the combination of previous searches, a targeted analysis requiring three or more charged leptons (electrons or muons) is presented, focusing on the challenging scenario in which the difference in mass between the two least massive neutralinos is approximately equal to the mass of the Z boson. The results are interpreted in simplified models of chargino-neutralino or neutralino pair production. For chargino-neutralino production, in the case when the lightest neutralino is massless, the combination yields an observed (expected) limit at the 95% confidence level on the chargino mass of up to 650 (570) GeV, improving upon the individual analysis limits by up to 40 GeV. If the mass difference between the two least massive neutralinos is approximately equal to the mass of the Z boson in the chargino-neutralino model, the targeted search requiring three or more leptons obtains observed and expected exclusion limits of around 225 GeV on the second neutralino mass and 125 GeV on the lightest neutralino mass, improving the observed limit by about 60 GeV in both masses compared to the previous CMS result. In the neutralino pair production model, the combined observed (expected) exclusion limit on the neutralino mass extends up to 650-750 (550-750) GeV, depending on the branching fraction assumed. This extends the observed exclusion achieved in the individual analyses by up to 200 GeV. The combined result additionally excludes some intermediate gaps in the mass coverage of the individual analyses.Peer reviewe

    Search for heavy resonances decaying to Z(őŬĮőĹ)V(q¬Įq‚Ä≤) in proton-proton collisions at ‚ąös=13‚ÄČ‚ÄČTeV

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    Publisher Copyright: ¬© 2022 CERN.A search is presented for heavy bosons decaying to Z(őŬĮőĹ)V(q¬Įq‚Ä≤), where V can be a W or a Z boson. A sample of proton-proton collision data at ‚ąös=13‚ÄČ‚ÄČTeV was collected by the CMS experiment during 2016‚Äď2018. The data correspond to an integrated luminosity of 137‚ÄČ‚ÄČfb‚ąí1. The event categorization is based on the presence of high-momentum jets in the forward region to identify production through weak vector boson fusion. Additional categorization uses jet substructure techniques and the presence of large missing transverse momentum to identify W and Z bosons decaying to quarks and neutrinos, respectively. The dominant standard model backgrounds are estimated using data taken from control regions. The results are interpreted in terms of radion, W‚Ä≤ boson, and graviton models, under the assumption that these bosons are produced via gluon-gluon fusion, Drell‚ÄďYan, or weak vector boson fusion processes. No evidence is found for physics beyond the standard model. Upper limits are set at 95%¬†confidence level on various types of hypothetical new bosons. Observed (expected) exclusion limits on the masses of these bosons range from 1.2 to 4.0 (1.1 to 3.7)¬†TeV.Peer reviewe

    Search for additional neutral MSSM Higgs bosons in the tau tau final state in proton-proton collisions at root s=13 TeV

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    A search is presented for additional neutral Higgs bosons in the tau tau final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into tau leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2TeV) for production in association with b quarks, assuming a narrow width resonance. In the m(h)(mod+) scenario these limits translate into a 95% CL exclusion of tan beta > 6 for neutral Higgs boson masses below 250 GeV, where tan beta is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6TeV for tan beta = 60.Peer reviewe

    Search for resonant t(t)over-bar production in proton-proton collisions at root s=13 TeV

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    A search for a heavy resonance decaying into a top quark and antiquark (tt) pair is performed using proton-proton collisions at p s = 13TeV. The search uses the data set collected with the CMS detector in 2016, which corresponds to an integrated luminosity of 35.9 fb. The analysis considers three exclusive fi nal states and uses reconstruction techniques that are optimized for top quarks with high Lorentz boosts, which requires the use of nonisolated leptons and jet substructure techniques. No signi fi cant excess of events relative to the expected yield from standard model processes is observed. Upper limits on the production cross section of heavy resonances decaying to a tt pair are calculated. Limits are derived for a leptophobic topcolor Z 0 resonance with widths of 1, 10, and 30%, relative to the mass of the resonance, and exclude masses up to 3.80, 5.25, and 6.65TeV, respectively. Kaluza-Klein excitations of the gluon in the Randall-Sundrum model are excluded up to 4.55TeV. To date, these are the most stringent limits on tt resonances.Peer reviewe

    Measurement of the energy density as a function of pseudorapidity in proton-proton collisions at root s=13 TeV

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    A measurement of the energy density in proton-proton collisions at a centre-of-mass energy of sTeV is presented. The data have been recorded with the CMS experiment at the LHC during low luminosity operations in 2015. The energy density is studied as a function of pseudorapidity in the ranges -6.6<<-5.2 and 3.15<||<5.20. The results are compared with the predictions of several models. All the models considered suggest a different shape of the pseudorapidity dependence compared to that observed in the data. A comparison with LHC proton-proton collision data at s=0.9 and 7 TeV confirms the compatibility of the data with the hypothesis of limiting fragmentation.Peer reviewe
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