Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

Direct numerical simulation of an evaporating turbulent diluted jet-spray at moderate reynolds number

The fluid-structure interaction phenomenon is often encountered in the ocean engineering field. In the present work, a non-local numerical model is developed for the simulations of weakly compressible viscous fluid and elastic structure interactions. The peridynamic theory is adopted for both the structure and fluid modelling. The elastic structure is described by using the ordinary state-based peridynamics, while the fluid is modelled by utilizing the peridynamic differential operator. Furthermore, the updated Lagrangian description is adopted for the fluid including the relative deformation gradient expressed by the peridynamic differential operator. The fluid-structure interface and its normal direction are calculated via the gradient of a colour function, which varies with the fluid motion and structure deformation. Besides, the interaction force exerted from fluid to structure is constrained to be always perpendicular to the moving interface. Hence the fluid motion and structural deformation are predicted simultaneously. The validation of the developed model is conducted through the simulation of a water dam break with a rubber gate. The good agreement between the peridynamic and the experiment results demonstrates the capability of the current model for solving fluid-elastic structure interaction problems.

Fluid-elastic structure interaction simulation by using ordinary state-based peridynamics and peridynamic differential operator

PeriPy - A high performance OpenCL peridynamics package

In a wide range of applications, the estimate of droplet evaporation time is based on the classical D 2-law, which, assuming a fast mixing and fixed environmental properties, states that the droplet surface decreases linearly with time at a determined rate. However, in many cases the predicted evaporation rate is overestimated. In this Letter, we propose a revision of the D 2-law capable of accurately determining droplet evaporation rate in dilute conditions by a proper estimate of the asymptotic droplet properties. Besides a discussion of the main assumptions, we tested the proposed model against data from direct numerical simulations finding an excellent agreement for predicted droplet evaporation time in dilute turbulent jet-sprays.

Revisiting D 2 -law for the evaporation of dilute droplets

The effects of swirled inflows on the evaporation of dilute acetone droplets dispersed in turbulent jets are investigated by means of direct numerical simulation. The numerical framework is based on a hybrid Eulerian–Lagrangian approach and the point-droplet approximation. Phenomenological and statistical analyses of both phases are presented. An enhancement of the droplet vaporization rate with increasing swirl velocities is observed and discussed. The key physical drivers of this augmented evaporation, namely dry air entrainment and swirl-induced centrifugal forces acting on the droplets, are isolated with the aid of additional simulations in which the inertial properties of the droplets are neglected. The correlation between swirl and dry air entrainment rate is found to be responsible for the increase of the global evaporation rate and the spray penetration length reduction, while swirl-induced centrifugal forces are found to be effective only in the jet shear layer, close to the injection orifice, for the analyzed cases.

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Direct Numerical Simulations of the Evaporation of Dilute Sprays in Turbulent Swirling Jets

Hydraulic fracturing is a non-linear and multi-physics problem involving the break up of a solid medium due to the action of hydrodynamic forces. Fluid and solid mechanics are involved at the same time together with fracture mechanics. Despite its relevance in many scientific and engineering fields, the theoretical and numerical description of hydraulic fracturing remains a challenging matter and the capabilities of existing models for applications are still limited. In this context, we propose a novel numerical approach to the Direct Numerical Simulation of hydraulic fracturing based on the Navier–Stokes equations coupled with peridynamic theory of solid mechanics through a multi-direct Immersed Boundary Method. The main advantage of this approach consists in the reliable crack-detection and tracking capabilities of peridynamics together with the capability of the Immersed Boundary Method of managing no-slip and no-penetration boundary conditions on complex and time-evolving interfaces. A massive-parallel solver based on this model has been implemented. We present a detailed theoretical description of the proposed methodology as well as the results of an extensive validation campaign for the new solver. Different benchmarking tests are provided together with the qualitative results of a simulation reproducing the fracture of a solid structure in a laminar, unsteady flow.

A Novel Approach for Direct Numerical Simulation of Hydraulic Fracture Problems

A fluid-structure interaction model based on peridynamics and Navier-Stokes equations for hydraulic fracture problems

Evaporation of dispersed droplets within a turbulent flow is of crucial importance in several applications (Jenny et al, Prog Energy Combust Sci 38(6):846–887, 2012, [1]). A typical example consists in designing innovative internal combustion engines, capable to increase combustion efficiency and reduce pollutants emission levels. These goals are directly related to the accurate control of the vaporization process which, in turns, affects the mixing homogeneity. In particular, turbulent sprays are complex multiphase flows in which liquid evaporating droplets are dispersed within a turbulent gaseous phase. The evaporation process occurs via mass, momentum and energy exchanges between the two phases causing the spray dynamics to be a challenging modeling task due to the presence of unsteady, multi-scale and multiphase processes.

F. Dalla Barba

Papers

Revisiting D 2 -law for the evaporation of dilute droplets

Direct Numerical Simulations of the Evaporation of Dilute Sprays in Turbulent Swirling Jets

A Novel Approach for Direct Numerical Simulation of Hydraulic Fracture Problems

A fluid-structure interaction model based on peridynamics and Navier-Stokes equations for hydraulic fracture problems

Evaporation Dynamics in Dilute Turbulent Jet Sprays