Influence Of Break Up And Coalescence Models In A Bubbly Flow

Three-dimensional gas-liquid simulations in a cylindrical bubble reactor with an external loop were performed. The effects of average bubble size, bubble size distribution and gas inlet plate geometry were evaluated. The population balance models of Luo and Svendsen [6] and Prince and Blanch [9] were used in order to simulate the breakup and coalescence effects, respectively. The drag force was modeled using the Ishii-Zuber model, which takes into account bubble deformation effects. The k-epsilon turbulence model was applied only for the continuous phase and the dispersed one was considered laminar. Lift, Magnus and added mass forces were neglected. Simulations at different superficial gas velocities were performed using two different inlets: a uniform and a perforated plate entrance. Breakup and coalescence effects were studied only for the uniform gas inlet geometry and the particle size distribution was obtained using a probability density function. Results show that the approach used in this work provided physically consistent results with transient effects in the column. Good agreement of the time-averaged gas holdup with experimental data on gas holdup available in the literature was obtained. It was found that the simulation approach used in this work was able to capture the complex transient fluid dynamics in bubbly flows.Cassanello, M., Larachi, F., Kemoun, A., Al-Dahhan, M.H., Dudukovic, M.P., Inferring liquid chaotic dynamics in bubble columns (2001) Chemical Engineering Science, 56 (21-22), pp. 6125-6134. , DOI 10.1016/S0009-2509(01)00218-4, PII S0009250901002184, Fifth International Conference on Gas-Liquid nd Gas-Liquid-Solid Reactor EngineeringChen, P., Sanyal, J., Dudukovic, M.P., Numerical simulation of bubble columns flows: Effect of different breakup and coalescence closures (2005) Chemical Engineering Science, 60 (4), pp. 1085-1101. , DOI 10.1016/j.ces.2004.09.070, PII S000925090400733XKrishna, R., Van Baten, J.M., Urseanu, M.I., Ellenberger, J., A scale up strategy for bubble column slurry reactors (2001) Catalysis Today, 66, pp. 199-207Krishna, R., Van Baten, J.M., Urseanu, M.I., Three-phase Eulerian simulations of bubble columns reactors operating in the churn-turbulent regime: A scale up strategy (2004) Chemical Engineering Science, 55, pp. 4483-4493Luo, H., Svendsen, H.F., Theoretical Model for Drop and Bubble Breakup in Turbulent Dispersions (1996) AIChE Journal, 42 (5), pp. 1225-1233Maretto, C., Krishna, R., Modelling of a bubble column slurry reactor for Fischer-Tropsch synthesis (1999) Catalysis Today, 52 (2-3), pp. 279-289. , PII S0920586199000826, Kinetics and Modelling of Catalytic Reactions: from Laboratory to Industrial ReactorMatonis, D., Gidaspow, D., Bahary, M., CFD simulation of flow and turbulence in a slurry bubble column (2002) AIChE Journal, 48 (7), pp. 1413-1429. , DOI 10.1002/aic.690480706Prince, M.J., Blanch, H.W., Bubble coalescence and break-up in air-sparged bubble columns. (1990) AICHE J., 36, pp. 1485-1499. , 10 OctSantos, C.M., Dionísio, R.P., Cerqueira, H.S., Sousa-Aguiar, E.F., Mori, M., D́Avila, M.A., Three-dimensional gas-liquid CFD simulations in cylindrical bubble columns (2007) The International Journal of Chemical Reactor Engineering, 5, pp. A90Van Baten, J.M., Krishna, R., CFD modeling of a bubble column reactor carrying out a consecutive A -> B -> C reaction (2004) Chemical Engineering and Technology, 27 (4), pp. 398-406. , DOI 10.1002/ceat.200401968Lin, J., Han, M., Wang, T., Zhang, T., Wang, J., Jin, Y., Influence of the gas distributor on the local hydrodynamic behavior of an external loop airlift reactor (2004) Chemical Engineering Journal, 102 (1), pp. 51-59. , DOI 10.1016/j.cej.2004.01.023, PII S1385894704000804Wiemann, D., Mewes, D., Prediction of backmixing and mass transfer in bubble columns using a multifluid model (2005) Industrial and Engineering Chemistry Research, 44 (14), pp. 4959-4967. , DOI 10.1021/ie049163

Measurement of singly Cabibbo-suppressed decays D0 → π0π0π0, π0π0η, π0ηη and ηηη

Using a data sample of e+e− collision data corresponding to an integrated luminosity of 2.93 fb−1 collected with the BESIII detector at a center-of-mass energy of s=3.773GeV, we search for the singly Cabibbo-suppressed decays D0→π0π0π0, π0π0η, π0ηη and ηηη using the double tag method. The absolute branching fractions are measured to be B(D0→π0π0π0)=(2.0±0.4±0.3)×10−4, B(D0→π0π0η)=(3.8±1.1±0.7)×10−4 and B(D0→π0ηη)=(7.3±1.6±1.5)×10−4 with the statistical significances of 4.8σ, 3.8σ and 5.5σ, respectively, where the first uncertainties are statistical and the second ones systematic. No significant signal of D0→ηηη is found, and the upper limit on its decay branching fraction is set to be B(D0→ηηη)<1.3×10−4 at the 90% confidence level

Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII

The electromagnetic process is studied with the initial-state-radiation technique using 7.5 fb−1 of data collected by the BESIII experiment at seven energy points from 3.773 to 4.600 GeV. The Born cross section and the effective form factor of the proton are measured from the production threshold to 3.0 GeV/ using the invariant-mass spectrum. The ratio of electric and magnetic form factors of the proton is determined from the analysis of the proton-helicity angular distribution

Study of the processes χcJ → Ξ−Ξ¯+ and Ξ0Ξ¯0

Using 448.1 × 106 ψ(3686) decays collected with the BESIII detector at the BEPCII e+e− storage rings, the branching fractions and angular distributions of the decays χcJ → Ξ−Ξ¯¯¯¯+ and Ξ0Ξ¯¯¯¯0 (J = 0, 1, 2) are measured based on a partial-reconstruction technique. The decays χc1 → Ξ0Ξ¯¯¯¯0 and χc2 → Ξ0Ξ¯¯¯¯0 are observed for the first time with statistical significances of 7σ and 15σ, respectively. The results of this analysis are in good agreement with previous measurements and have significantly improved precision

Search for an axion-like particle in radiative J/ψ decays

We search for an axion-like particle (ALP) a through the process ψ(3686)→π+π−J/ψ, J/ψ→γa, a→γγ in a data sample of (2.71±0.01)×109 ψ(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/ψ→γa and the ALP-photon coupling constant gaγγ are set at 95% confidence level in the mass range of 0.165≤ma≤2.84GeV/c2. The limits on B(J/ψ→γa) range from 8.3×10−8 to 1.8×10−6 over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165≤ma≤1.468GeV/c2

Anticoagulant selection in relation to the SAMe-TT2R2 score in patients with atrial fibrillation: The GLORIA-AF registry

Aim: The SAMe-TT2R2 score helps identify patients with atrial fibrillation (AF) likely to have poor anticoagulation control during anticoagulation with vitamin K antagonists (VKA) and those with scores &gt;2 might be better managed with a target-specific oral anticoagulant (NOAC). We hypothesized that in clinical practice, VKAs may be prescribed less frequently to patients with AF and SAMe-TT2R2 scores &gt;2 than to patients with lower scores. Methods and results: We analyzed the Phase III dataset of the Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation (GLORIA-AF), a large, global, prospective global registry of patients with newly diagnosed AF and 651 stroke risk factor. We compared baseline clinical characteristics and antithrombotic prescriptions to determine the probability of the VKA prescription among anticoagulated patients with the baseline SAMe-TT2R2 score &gt;2 and 64 2. Among 17,465 anticoagulated patients with AF, 4,828 (27.6%) patients were prescribed VKA and 12,637 (72.4%) patients an NOAC: 11,884 (68.0%) patients had SAMe-TT2R2 scores 0-2 and 5,581 (32.0%) patients had scores &gt;2. The proportion of patients prescribed VKA was 28.0% among patients with SAMe-TT2R2 scores &gt;2 and 27.5% in those with scores 642. Conclusions: The lack of a clear association between the SAMe-TT2R2 score and anticoagulant selection may be attributed to the relative efficacy and safety profiles between NOACs and VKAs as well as to the absence of trial evidence that an SAMe-TT2R2-guided strategy for the selection of the type of anticoagulation in NVAF patients has an impact on clinical outcomes of efficacy and safety. The latter hypothesis is currently being tested in a randomized controlled trial. Clinical trial registration: URL: https://www.clinicaltrials.gov//Unique identifier: NCT01937377, NCT01468701, and NCT01671007