Search results for "Choked flow"

Flow hydraulic characteristics determining the occurrence of either smooth or abrupt sewer pressurization

2014

Laboratory experiments showed that pipe pressurization consequent on a drastic reduction in the downstream discharge can occur either by a gradual rising of the free-surface (“smooth” pressurization) or by propagation of a front filling the whole cross-section (“abrupt” pressurization). This study examines the free-surface flow characteristics that determine smooth or abrupt pressurization pattern through a theoretical approach using dimensionless variables. A critical flow rate value, which separates the pressurization patterns, exists for any given pipe diameter. For flow rates higher than this specific value, only abrupt pressurization occurs. For lower flow rates, either smooth or abrup…

A High-Resolution Penalization Method for large Mach number Flows in the presence of Obstacles

2009

International audience; A penalization method is applied to model the interaction of large Mach number compressible flows with obstacles. A supplementary term is added to the compressible Navier-Stokes system, seeking to simulate the effect of the Brinkman-penalization technique used in incompressible flow simulations including obstacles. We present a computational study comparing numerical results obtained with this method to theoretical results and to simulations with Fluent software. Our work indicates that this technique can be very promising in applications to complex flows.

Examination of the shock wave regular reflexion phenomenon in a rarefied supersonic plasma flow

2005

The flow properties of a low-pressure weakly ionized supersonic argon plasma jet are examined using Fabry–Perot interferometry and laser induced fluorescence spectroscopy. The flow velocity and equilibrium temperature measured at the torch nozzle exit are in close agreement with computational fluid dynamics calculations. The model also predicts the plasma flow to be in a rarefied regime. Departure from thermal equilibrium is indeed observed behind the nozzle where the parallel temperature differs significantly from the perpendicular temperature. The development of the axial velocity component along the jet center stream line reveals the occurrence of the shock wave regular reflexion phenome…

Closure to “Theoretical End‐Depth‐Discharge Relationship for Free Overfall” by Vito Ferro

2000

Kinetic Monte Carlo Simulations of Flow-Assisted Polymerization

2012

We performed kinetic Monte Carlo simulations on a model of a polymerization process in the presence of a periodic oscillatory flow to explore the role of mixing in polymerization reactors. Application of an oscillatory flow field helps overcome the diffusive limitations that develop during a polymerization process due to an increase in the molecular weights of polymer chains, thereby giving rise to high rates of polymerization. A systematic increase in the flow strength results in a "dynamic" coil-stretch transition, leading to an elongation of polymer chains. Reactive ends of stretched (polymer) chains react more frequently than the reactive ends of coiled chains, which are screened by oth…