Modeling of finite-size droplets and particles in multiphase flows

The conventional point-particle approach for treating the dispersed phase in a continuous flowfield is extended by taking into account the effect of finite particle size, using a Gaussian interpolation from Lagrangian points to the Eulerian field.The inter-phase exchange terms in the conservation equations are distributed over the volume encompassing the particle size, as opposed to the Dirac delta function generally used in the point-particle approach.The proposed approach is benchmarked against three different flow configurations in a numerical framework based on large eddy simulation（LES） turbulence closure.First, the flow over a circular cylinder is simulated for a Reynolds number of 3900 at 1 atm pressure.Results show good agreement with experimental data for the mean streamwise velocity and the vortex shedding frequency in the wake region.The calculated flowfield exhibits correct physics, which the conventional point-particle approach fails to capture.The second case deals with diesel jet injection in quiescent environment over a pressure range of 1.1–5.0 MPa.The calculated jet penetration depth closely matches measurements.It decreases with increasing chamber pressure, due to enhanced drag force in a denser fluid environment.Finally, water and acetone jet injection normal to air crossflow is studied at1 atm.The calculated jet penetration and Sauter mean diameter of liquid droplets compare very well with measurements.

Antileishmanial potential of a marine sponge Haliclona oculata against experimental visceral leishmaniasis

Objective:To evaluate the antileishmanial activity of a marine spongeHaliclona oculata.Methods:The crude methanol extract was prepared from the freshly collected sponge and its three fractions were also prepared by maceration method.The antileishmanial activity of these extract and fractions was tested againstLeishmania donovani.Results:The antileishmanial activity was tested bothin vitroand in vivo.The crude methanol extract exerted almost complete inhibition of promastigotes(81.0%±6.9%)and 78.8%±5.2%inhibition of intracellular amastigotes at 100μg/mL with IC_(50)values of 29.5μg/mL and 40.6μg/mL,respectively.The treatment of 500 mg/kg(p.o.)of the crude methanol extract for 5 d for Leishmania donovani infected hamsters resulted in 78.35%±10.20%inhibition of intracellular amastigotes.At a lower dose(250 mg/kg),it exhibited poor efficacy.Among the fractions,highestin vitro(>75%)and in vivo(84.3%±10.2%)antileishmanial activity was observed in n-chloroform fraction with IC_(50)values of 54.2μg/mL and 61μg/mL against promastigotes and intracellular amastigotes,respectively.Hexane fraction andn-butanol(both insoluble and soluble)fractions were found inactivein vitroand in vivo.Conclusions:Our findings indicate that this marine sponge has the potential to provide new insight toward development of an effective antileishmanial agent and,hence,more exhaustive studies are needed for exploiting the vast marine resources of the world to combat the scourge of several parasitic diseases.