Computational fluid dynamic simulations on liquid film behaviors at flooding in an inclined pipe

The complex liquid film behaviors at flooding in an inclined pipe were investigated with computational fluid dynamic(CFD) approaches. The liquid film behaviors included the dynamic wave characteristics before flooding and the transition of flow pattern when flooding happened. The influences of the surface tension and liquid viscosity were specially analyzed. Comparisons of the calculated velocity at the onset of flooding with the available experimental results showed a good agreement. The calculations verify that the fluctuation frequency and the liquid film thickness are almost unaffected by the superficial gas velocity until the flooding is triggered due to the Kelvin–Helmholtz instability. When flooding triggered at the superficial liquid velocity larger than0.15 m·s-1, the interfacial wave developed to slug flow, while it developed to entrainment flow when it was smaller than 0.08 m·s-1. The interfacial waves were more easily torn into tiny droplets with smaller surface tension, eventually evolving into the mist flow. When the liquid viscosity increases, the liquid film has a thicker holdup with more intensive fluctuations, and more likely developed to the slug flow.

A Numerical Scheme for the Quantum Fokker-Planck-Landau Equation Efficient in the Fluid Regime

We construct an efficient numerical scheme for the quantum Fokker-Planck-Landau(FPL)equation that works uniformly from kinetic to fluid regimes.Such a scheme inevitably needs an implicit discretization of the nonlinear collision operator,which is difficult to invert.Inspired by work[9]we seek a linear operator to penalize the quantum FPL collision term QqFPL in order to remove the stiffness induced by the small Knudsen number.However,there is no suitable simple quantum operator serving the purpose and for this kind of operators one has to solve the complicated quantum Maxwellians(Bose-Einstein or Fermi-Dirac distribution).In this paper,we propose to penalize QqFPL by the”classical”linear Fokker-Planck operator.It is based on the observation that the classicalMaxwellian,with the temperature replaced by the internal energy,has the same first five moments as the quantum Maxwellian.Numerical results for Bose and Fermi gases are presented to illustrate the efficiency of the scheme in both fluid and kinetic regimes.

Advantage of surgical intensive care unit(SICU)predominant by cardiothoracic surgeons in multiple trauma management in a primary hospital

Purpose It is a challenge for the primary hospitals to manage multiple trauma patients.In this article,we explored the advantage of establishing a surgical intensive care unit(SICU)predominant by cardiothoracic surgeons in the early management of multiple trauma.Methods This was a retrospective study and patients with multiple trauma in our hospital were collected and divided into two groups,based on time period and treat modes:group A(retrospective observation group)where patients were treated with the traditional treatment mode from January 2017 to December 2017 and group B(study group)where patients were treated in the SICU predominant by cardiothoracic surgeons from January 2018 to December 2018.Clinical data including demographics,injury severity score(ISS),causes of injury,time intervals from reception to entering SICU or operating room and mortality three days after injuries were collected.Data were analyzed by SPSS 20.0 software.Categorical variables were presented as number and/or frequency and continuous variables as mean±SD.Results Altogether 406 patients were included in this study,including 217 patients in group A and 189 patients in group B.General data between the two groups revealed no significant difference:mean age(years)(35.51±12.97 vs.33.62±13.61,p=0.631),gender distribution(mean/female,130/87 vs.116/73,p=0.589)and ISS(15.92±7.95 vs.16.16±6.89,p=0.698).Fall from height were the dominant mechanism of injury,with 135 cases in group A(71.4%)and 121 cases in group B(55.8%),followed by traffic accidents.Injury mechanism showed no significant differences between two groups(p=1.256).Introduction of the SICU significantly improved the care of trauma patients,regarding speed and mortality.Time intervals between reception and entering SICU or operating room was(108.23±6.72)min and(45.67±7.96)min in group A and B,respectively(p=0.001).Mortality three days after injuries was 13.89%and 5.53%in group A and B,respectively(p=0.005).Conclusion Establishing a SICU predominant by cardiothoracic surgeons can reduce the early mortality rates in multiple trauma patients.

STABILITY OF GENERALIZED JACKSON NETWORKS WITH INFINITE SUPPLY OF WORK

A general Jackson network （GJN） with infinite supply of work is considered. By fluid limit model, the author finds that the Markov process describing the dynamics of the GJN with infinite supply of work is positive Harris recurrent if the corresponding fluid model is stable. Furthermore, the author proves that the fluid model is stable if the usual traffic condition holds.

Recovering Navier–Stokes Equations from Asymptotic Limits of the Boltzmann Gas Mixture Equation

This paper is devoted to the derivation of macroscopic fluid dynamics from the Boltzmann mesoscopic dynamics of a binary mixture of hard-sphere gas particles.Specifically the hydrodynamics limit is performed by employing different time and space scalings.The paper shows that,depending on the magnitude of the parameters which define the scaling,the macroscopic quantities(number density,mean velocity and local temperature)are solutions of the acoustic equation,the linear incompressible Euler equation and the incompressible Navier–Stokes equation.The derivation is formally tackled by the recent moment method proposed by[C.Bardos,et al.,J.Stat.Phys.63(1991)323]and the results generalize the analysis performed in[C.Bianca,et al.,Commun.Nonlinear Sci.Numer.Simulat.29(2015)240].