Ricerc@Sapienza

The relative weight of convective and radiative wall heat transfer in liquid rocket engine thrust chambers is estimated by means of dedicated computational fluid dynamics tools. In particular, although the convective wall heat flux is directly evaluated from the solution of the flowfield, an appropriate computational tool, based on the discrete transfer method, is developed to evaluate the radiative wall heat flux. Numerical results are compared against experimental data from the literature, concerning sub-scale thrust chambers fed with either oxygen/methane or oxygen/hydrogen.

Numerical analysis of hybrid rocket internal ballistics is carried out with a Reynolds-averaged Navier-Stokes solver integrated with a customized gas-surface interaction wall boundary condition and coupled with a radiation code based on the discrete transfer method. The fuel grain wall boundary condition is based on species, mass, and energy conservation equations coupled with thermal radiation exchange and finite-rate kinetics for fuel pyrolysis modeling.

The aim of this work is to optimize iron nanoparticle production in stirred tank reactors equipped with two classical impellers: Rushton and four-pitched blade turbines, which are largely used in batch industrial synthesis and efficient scale-up. The main operative parameters of nanoparticle synthesis are the precursor initial concentration, reducing agent/precursor molar ratio, impeller–tank clearance, and impeller rotational velocity.

In a thin-volume photobioreactor where a concentrated suspension of microalgae is circulated throughout the established spatial irradiance gradient, microalgal cells experience a time-variable irradiance. Deploying this feature is the most convenient way of obtaining the so-called flashing light effect, improving biomass production in high irradiance. This work investigates the light flashing features of sloping wavy photobioreactors, a recently proposed type, by introducing and validating a computational fluid dynamics (CFD) model.

This numerical study investigated the effects of a vegetation patch on the flow of a channel. The numerical approach consisted of a CFD, 3-D model that applied the RANS equations to simulate the flow field, and the VOF model to represent the free surface. The patch altered the initial flow by inducing regions of reduced velocity in the patch wake (approximately 40% reduction), and regions of enhanced velocity around of the patch (approximately 16% increase), and these regions extended throughout the water depth.