Session A18: Industrial Applications: General & Propulsion

Mathematical model to predict cracking in drying polymer film

Thin films of polymer coatings find applications in several areas such as pharmaceutical products, personal care products, paints, etc. for functional and protection purposes. These coatings are initially cast as polymer solution where the concentration of the polymer increases as the solvent evaporates leading to the solidified film. During this process, the film can freely shrink from the thickness direction, however, the shrinkage is contained in the plane of coating as it strongly adheres with the substrate. Due to constraint shrinkage, the film comes under tension and it may lead to crack if tension exceeds a critical value. The formation of cracks makes the drying process very complex, and it is important to understand the mechanism to obtain the crack-free films. A model has been developed to predict the critical stress and the critical thickness for cracking in polymer films by equating the elastic energy to the surface energy. The model predictions show that cracking can be avoided if the initial film thickness is low, films are soft and the substrate is stiffer. In other words, for a film to crack on stiff substrates, the initial film thickness should be made large. The model predictions show good agreement with measurements.   

Numerical simulation of wax deposition in gas-liquid flow complemented by a thin film model

A methodology is developed for simulation of wax deposition in industrial devices, with a coupled solution of the bulk flow and a thin film model. The versatility and simplicity of the model allow for simulation of phenomena in a large range of timescales, with the possible presence of multiple phases, complex geometries or other phenomena. The model is implemented in OpenFOAM, and validated with experimental measurements of deposit thickness for single-phase and two-phase flows from the literature. A one-dimensional formulation is also implemented in a general-purpose multiphase transient pipe simulator, applicable to industrial conditions.   

Experimental and numerical modelling of mass transfer in a metallurgical ladle

Mass transfer between liquid steel and slag is an important physical phenomenon during secondary metallurgy for prediction of the chemical reaction rate and adjustment of liquid steel composition. We study this phenomenon at ambient temperature with a water experiment and perform Direct Numerical Simulations, aiming to reproduce an argon-gas bottom-blown ladle. First, we measure the evolution of the time-averaged open-eye area as a function of the air flow rate. Both simulation and experiment agree relatively well and are close to other water experiments in the literature. Secondly, the mass transfer of thymol between water and oil is investigated. The experimental results show that two mass transfer regimes can be observed. The regime change coincides with atomization of the oil layer resulting in the continuous formation of oil droplets in the water whenever the air flow rate rises above a critical value. The numerical results for the mass-transfer rate or Sherwood number are obtained at small Schmidt numbers and are then extrapolated to the high Schmidt number of the experiment. A good agreement with experiment is observed although with large error bars. The Sherwood numbers between the two largest simulated flow rates show a steep increase.   

Three-Dimensional Electronic Microfliers Inspired by Wind-Dispersed Seeds

Miniaturized, wireless, battery-free electronic devices may provide the basis of future systems for environmental monitoring, population surveillance, disease management and other applications that require coverage over large spatial scales. This work shows that wind-dispersed seeds can serve as the bio-inspiration for unusual aerial schemes to distribute components in natural environments or city settings via controlled, passive flight. State-of-the-art fabrication/production techniques for electronic, optoelectronic, microfluidic and microelectromechanical technologies that align with mechanically guided assembly of three-dimensional (3D) mesostructures provide access to miniature, 3D fliers optimized for such purposes. We demonstrate a range of 3D macro-, meso- and microscale fliers produced in this manner with sample functionalities that incorporate active electronic and colorimetric payloads. Experimental studies of the aerodynamics of high-performance structures of this type establish a set of fundamental considerations in bio-inspired design, focusing on 3D fliers that exhibit controlled rotational kinematics and low terminal velocities.   

Computational Modeling of Wave Bioreactors via Open-Source CFD Software

Rocking wave bioreactors were developed in the late 1990s as a means of culturing cells in a low-shear stress environment. More recently, this class of reactors have been considered for use in the production of cultivated meat. Here we present the results of modelling and multi-physics computational fluid dynamics simulations of a rocking wave bioreactor developed in the open-source package Basilisk (http://basilisk.fr). We use a centered finite volume Navier-Stokes solver and a volume-of-fluid (VOF) interface reconstruction method, with adaptive mesh refinement capabilities. The simulations also solve the advection-diffusion equation for a tracer representing oxygen transport through the growth medium. Our results are compared to prior experimental and computational studies of fluid motion and mixing timescales in rocking wave bioreactors. We finally discuss future extensions of this work, focusing on the needs of the burgeoning cultivated meat industry.   

Integrated platform for simulations and machine learning

Recent advances in computing and data storage have spurred a trend of machine-learning democratisation. Nowadays, data are hailed as the new transformative commodity, however, some researchers are sceptical whether machine learning alone is sufficient to tackle complex problems.  On the other hand, the coupling of machine-learning methods with physics-based simulation approaches has grown in popularity in recent years in both scientific and industrial settings. Nevertheless, the data-centric engineering paradigm lacks a common, easy-to-use solution framework to help researchers and industry practitioners couple machine-learning and simulations. In this work, we develop a cloud native integrated platform that couples first-principles, physics-based simulation approaches to machine learning pipelines, within a standardised, low-code solution framework. We showcase the ability of the platform to run fluid flow simulations, developed using OpenFoam, on a scalable cloud cluster programmatically and also through a user interface. We show how simulation metadata and outputs are automatically logged and used for downstream machine-learning pipelines. The solution platform is generic, easily extensible, and can handle different data-centric engineering algorithms like calibration, optimisation, and risk analytics, among others.   

CFD study of a container ships nominal wake fields in oblique regular waves

Accurate estimation of the actual nominal wake behind the ship in waves is important for propeller design. The present CFD study investigates the nominal wake fields of the Kriso Container Ship (KCS) ship in regular waves with wavelength equal to the ship length with five different headings. The ship is sailing at design speed and the wave steepness is 1/60. The results show that when sailing in the studied waves, the nominal wake fraction fluctuate up to 39% of the mean nominal wake fraction. The mean nominal wake is higher than in calm water for all headings besides head sea waves. The heading with maximum mean nominal wake fraction is the stern quartering sea waves, with a 16% higher mean nominal wake fraction than in calm water. It is found that the transient bilge vortex and shadow from the skeg have a significant influence on the nominal wake field. It is estimated that the angle of attack on some points on the r/R=0.7 circle in the propeller plane varies up to 5 degrees.