1,053 research outputs found
Large scale horizontal cylinder forces in waves and currents
No full textThis paper describes laboratory measurements of forces and pressures on smooth and rough horizontal cylinders of diameters 0.21m and 0.5m beneath waves of heights up to 1.9m, in the presence of currents up to Im/s in either direction. Drag and inertia coefficients evaluated on a wave-by-wave basis exhibited very wide scatter, but average values over all Keulegan Carpenter numbers were found insensitive to currents and gave predictions of the largest peak horizontal forces to within 16% of the measurements in 90% of cases in irregular waves. Vertical forces deviated much more strongly from Morison predictions owing to vortex shedding, and to slowly-varying forces due to the Magnus effect associated with wave-induced circulation.<br/
Loading on a vertical cylinder near mean water level in long-and-short-crested waves
No full textThis paper presents the results of an experimental investigation on wave forces on a vertical cylinder in the splash zone. The cylinder was subjected to long- and short-crested waves corresponding to JONSWAP spectra, and sectional loads were measured on force sleeves up to mean water level. Ambient particle velocities were measured by means of perforated ball velocity metres whose performance in intermittent flow was checked with reference to a Laser Doppler Anemometer. Maximum Keulegan-Carpenter numbers were about 24, and maximum Reynolds numbers about 8.5 x 104. Analysis of the measurements concentrated on determining the effect of wave directionality on loading at mean water level. Comparison with earlier results for the submerged part of the cylinder suggests that in the splash zone directionality leads to stronger attenuation of loading than at lower elevations. The changes in loading are rather greater than those predicted by Dean's (1977) hybrid theory
Loading on a vertical cylinder in multidirectional waves
No full textThis paper presents laboratory measurements of local and total loading on an isolated vertical cylinder in irregular unidirectional and multidirectional waves. Maximum Keulegan-Carpenter numbers in individual waves were about 16, and maximum Reynolds numbers about 3 × 104. It is shown that in these conditions, existing theoretical and numerical models underestimate the reduction in loading on a cylinder due to wave spreading. Besides the changes that are predicted when Morison's equation is used with constant coefficients, there are hydrodynamic influences that contribute further force reductions. Comparisons with Dean's (1977) hybrid approach suggest that in the present conditions these reductions are in the region of 3 and 6 percent for a spreading function cos2s , with s = 8 and s = 2, respectively. Larger reductions can be expected at higher Keulegan-Carpenter numbers, though scale effects are likely to become more important in the drag-dominated regime
Local forces on a vertical cylinder in regular and irregular waves
No full textThis paper presents results from an experimental investigation on the loading on a rigid slender vertical circular cylinder in undirectional regular and irregular waves. The ambient flow was measured directly, so that the derived results would not be subject to additional uncertainties associated with the use of wave theories. Morison drag, inertia and lift coefficients are computed from forces measured at one force sleeve and compared with data obtained at the same Reynolds and Keulegan Carpenter numbers, but under uniform flow conditions in a U-tube. In regular waves, the results show the importance of the non-uniformity of wave-induced flow, and in irregular waves it is clear that the loading is much influenced by the history of the flow.NRC publication: Ye
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
No full textThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
First observation of the decay Bs0→K*0K*0
No full textThe first observation of the decay B0s→K∗0K∗0 is reported using 35 pb−1 of data collected by LHCb in proton–proton collisions at a centre-of-mass energy of 7 TeV. A total of 49.8±7.5 B0s→(K+π−)(K−π+) events are observed within ±50 MeV/c2 of the B0s mass and 746 MeV/c2 < mKπ < 1046 MeV/c2, mostly coming from a resonant B0s→K∗0K∗0 signal. The branching fraction and the CP-averaged K∗0 longitudinal polarization fraction are measured to be B(B0s→K∗0K∗0)=(2.81±0.46(stat.)±0.45(syst.)±0.34(fs/ fd))×10−5 and fL =0.31±0.12(stat.)±0.04(syst.)
Author Correction: COVID-19 vaccine guidance for patients with cancer participating in oncology clinical trials
No full textIn the original version of this Perspective, the name of the author Giuseppe Curigliano was incorrectly written as Guiseppe Curigiliano. The affiliations have been corrected in the HTML and PDF versions of the manuscrip
Observation of the suppressed ADS modes B± → [π±K-/+ π+π-]D K± and B± → [π± K-/+π+π-]Dπ±
No full textAn analysis of and B± → DK± and B± → Dπ±
decays is presented where the D meson is reconstructed in the four-body final state K± π-/+π+π-. Using LHCb data corresponding to an integrated luminosity of 1.0 fb-1, first observations are made of the suppressed ADS modes B± →[π± K-/+π+π-]DK± and B± → [π± K-/+π+π-]Dπ± with a significance of 5.1 sigma and greater than 10 sigma, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B± → DK ± amplitudes is determined to be rKB = 0.097 ± 0.011
- …
