A Numerical Study of Droplet Impingement for In-Flight Ice Accretion Prediction

2016 ◽  
Author(s):  
Hao Zhang ◽  
Chihyung Wen ◽  
Junwei Su
Keyword(s):  
Collection Efficiency ◽  
Numerical Study ◽  
Three Dimensional ◽  
Ice Accretion ◽  
Eulerian Model ◽  
Droplet Impingement ◽  
Basic Module ◽  
Wide Range ◽  
Subsonic Regime ◽  
Finite Volume Approach

Droplet impingement is the basic module in both ice accretion and anti-icing numerical calculation. A three dimensional finite volume approach with the capacity of modeling the in-flight droplet impingement on a wide range of subsonic regime is therefore established in this research, using OpenFOAM®. The Eulerian model is applied to estimate the droplet flow field with the same computational grid sets as those of the air flow calculation. The roughness effect caused by ice accretion is considered in the wall function modeling. Thus, the collection efficiency could be investigated for further icing numerical simulations. This approach is validated on both cylinder and sphere benchmark cases. The results are compared with the corresponding experimental and LEWICE (LEWis ICE accretion program) simulation data.

scholarly journals Drops bouncing off macro-textured superhydrophobic surfaces

2017 ◽  
Vol 824 ◽  
pp. 866-885 ◽  
Author(s):  
Ali Mazloomi Moqaddam ◽  
Shyam S. Chikatamarla ◽  
Iliya V. Karlin
Keyword(s):  
Contact Time ◽  
Numerical Study ◽  
Three Dimensional ◽  
Superhydrophobic Surfaces ◽  
Nonlinear Behaviour ◽  
Textured Surfaces ◽  
Texture Density ◽  
Wide Range ◽  
Quantitative Manner ◽  
The Impact

Recent experiments with droplets impacting macro-textured superhydrophobic surfaces revealed new regimes of bouncing with a remarkable reduction of the contact time. Here we present a comprehensive numerical study that reveals the physics behind these new bouncing regimes and quantifies the roles played by various external and internal forces. For the first time, accurate three-dimensional simulations involving realistic macro-textured surfaces are performed. After demonstrating that simulations reproduce experiments in a quantitative manner, the study is focused on analysing the flow situations beyond current experiments. We show that the experimentally observed reduction of contact time extends to higher Weber numbers, and analyse the role played by the texture density. Moreover, we report a nonlinear behaviour of the contact time with the increase of the Weber number for imperfectly coated textures, and study the impact on tilted surfaces in a wide range of Weber numbers. Finally, we present novel energy analysis techniques that elaborate and quantify the interplay between the kinetic and surface energy, and the role played by the dissipation for various Weber numbers.

Numerical Simulation of Icing on the Rotating Blade

2015 ◽  
Author(s):  
Wei Dong ◽  
JianJun Zhu ◽  
Rui Wang ◽  
Yong Chen
Keyword(s):  
Collection Efficiency ◽  
Numerical Study ◽  
High Fidelity ◽  
Ice Accretion ◽  
Blade Surface ◽  
Physical Processes ◽  
Ansys Fluent ◽  
Rotating Blade ◽  
Process Simulations ◽  
Ice Shapes

The physical processes involved in ice accretion on the rotating blade are complex. It is important to develop high fidelity numerical method and simulate the icing process on the blade under icing conditions. This paper presents a numerical study on the icing process on the rotating blade. The flow field around the blade is obtained using ANSYS FLUENT. The trajectories of supercooled water droplets and the collection efficiency are calculated by Eulerian approach. Heat and mass balance on the rotating blade surface is taken into account in icing process simulations. The NASA Rotor 67 blade is chosen as the computational model. The collection efficiency on the blade surface is computed and the impingement characteristics are analyzed. The 3D icing accretion on Rotor 67 blade is predicted at design point. The ice shapes of accretion time of 5s, 10s and 15s are simulated and the ice shapes at different span positions of the rotating blade are compared.

Fluid Flow and Lateral Fluid Dispersion in Bounded Granular Beds

2002 ◽  
Author(s):  
Azita Soleymani ◽  
Eveliina Takasuo ◽  
Piroz Zamankhan ◽  
William Polashenski
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Numerical Results ◽  
Transition To Turbulence ◽  
Wide Range

Results are presented from a numerical study examining the flow of a viscous, incompressible fluid through random packing of nonoverlapping spheres at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), spanning a wide range of flow conditions for porous media. By using a laminar model including inertial terms and assuming rough walls, numerical solutions of the Navier-Stokes equations in three-dimensional porous packed beds resulted in dimensionless pressure drops in excellent agreement with those reported in a previous study (Fand et al., 1987). This observation suggests that no transition to turbulence could occur in the range of Reynolds number studied. For flows in the Forchheimer regime, numerical results are presented of the lateral dispersivity of solute continuously injected into a three-dimensional bounded granular bed at moderate Peclet numbers. Lateral fluid dispersion coefficients are calculated by comparing the concentration profiles obtained from numerical and analytical methods. Comparing the present numerical results with data available in the literature, no evidence has been found to support the speculations by others for a transition from laminar to turbulent regimes in porous media at a critical Reynolds number.

Study of arching behaviour and strength of concrete masonry infills under out-of-plane loading

2019 ◽  
Vol 46 (10) ◽  
pp. 896-908 ◽  
Author(s):  
Ehsan Nasiri ◽  
Yi Liu
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Contributing Factors ◽  
Concrete Frames ◽  
Masonry Infills ◽  
Concrete Masonry ◽  
Wide Range ◽  
Out Of Plane ◽  
Three Dimensional Finite Element

A numerical study using a three-dimensional finite element model was conducted to investigate the arching behaviour and strength of concrete masonry infills bounded by reinforced concrete frames subjected to out-of-plane loading. Physical specimens were concurrently tested to provide results for validation of the model as well as evidence of directional characteristics of arching behaviour of masonry infills. A subsequent parametric study using the model included a wide range of infilled frame geometric properties. The results showed in detail the difference in one-way and two-way arching in terms of both strength and failure mechanism, and the contributing factors to this difference. Evaluation of the two main design equations for out-of-plane strength of masonry infills led to proposal of modifications to provide a more rational consideration of directional behaviour of concrete masonry infills. A comparison study using the available test results showed a marked improvement of strength prediction based on the proposed modification.

A Eulerian Method for Water Droplet Impingement by Means of an Immersed Boundary Technique

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Francesco Capizzano ◽  
Emiliano Iuliano
Keyword(s):  
Water Droplet ◽  
Numerical Solutions ◽  
Experimental Testing ◽  
Three Dimensional ◽  
Immersed Boundary ◽  
Test Cases ◽  
Ice Accretion ◽  
Droplet Impingement ◽  
Protection Systems ◽  
Numerical Approaches

The estimation of water droplet impingement is the first step toward a complete ice accretion assessment. Numerical approaches are usually implied to support the experimental testing and to provide fast responses when designing ice protection systems. Basically, two different numerical methodologies can be found in literature: Lagrangian and Eulerian. The present paper describes the design and development of a tool based on a Eulerian equation set solved on Cartesian meshes by using an immersed boundary (IB) technique. The tool aims at computing the evolution of a droplet cloud and the impingement characteristics onto the exposed surfaces of an aircraft. The robustness of the methodology and the accuracy of the approach are discussed. The method is applying to classical two- and three-dimensional test cases for which experimental data are available in literature. The results are compared with both experiments and body-fitted numerical solutions.

Prediction of Ice Accretion on Wind Turbine with Numerical Method

2012 ◽  
Vol 512-515 ◽  
pp. 754-757
Author(s):  
Xian Yi ◽  
Kai Chun Wang ◽  
Hong Lin Ma
Keyword(s):  
Wind Turbine ◽  
Numerical Method ◽  
Collection Efficiency ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Ice Accretion ◽  
Horizontal Axis Wind Turbine ◽  
Blade Tip ◽  
Computer Codes ◽  
Multiple Reference

A three dimensional numerical method and its computer codes, which are suitable to predict the process of horizontal axis wind turbine icing, are presented. The method is composed of the Multiple Reference Frame (MRF) method to calculate flowfield of air, an Eulerian method to compute collection efficiency and a three dimensional icing model companying with an iterative arithmetic for solving the model. Ice accretion on a 1.5 MW horizontal axis wind turbine is then computed with the numerical method, and characteristics of droplet collection efficiency and ice shape/type are obtained. The results show that ice on the hub and blade root is slight and it can be neglected comparing with ice near blade tip. From blade tip to root, ice becomes thinner and glaze ice may changes into rime ice.

Numerical Study of Impact Penetration Shearing Employing Finite Strain Viscoplasticity Model Incorporating Adiabatic Shear Banding

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Patrice Longère ◽  
André Dragon ◽  
Xavier Deprince
Keyword(s):  
Damage Mechanics ◽  
Numerical Study ◽  
Shear Banding ◽  
Three Dimensional ◽  
Adiabatic Shear ◽  
Deformation Model ◽  
Viscoplastic Material ◽  
Predictive Tool ◽  
Adiabatic Shear Banding ◽  
Wide Range

This work brings forward a twofold contribution relevant to the adiabatic shear banding (ASB) process as a part of dynamic plasticity of high-strength metallic materials. The first contribution is a reassessment of a three-dimensional finite deformation model starting from a specific scale postulate and devoted to cover a wide range of dissipative phenomena, including ASB-related material instabilities (strong softening prefailure stage). The model, particularly destined to deal with impacted structures was first detailed by (Longère et al. 2003, “Modelling Adiabatic Shear Banding Via Damage Mechanics Approach,” Arch. Mech., 55, pp. 3–38; 2005, “Adiabatic Shear Banding Induced Degradation in a Thermo-Elastic/Viscoplastic Material Under Dynamic Loading,” Int. J. Impact Eng., 32, pp. 285–320). The second novel contribution concerns numerical solution of a genuine ballistic penetration problem employing the above model for a target plate material. The ASB trajectories are shown to follow a multistage history and complex distribution pattern leading finally to plugging failure mechanism. The corresponding analysis and related parametric study are intended to put to the test the pertinency of the model as an advanced predictive tool for complex shock related problems.

scholarly journals Water transport and absorption in pharmaceutical tablets – a numerical study

Meccanica ◽  
2019 ◽  
Vol 55 (2) ◽  
pp. 421-433 ◽  
Author(s):  
Povilas Vaitukaitis ◽  
Dario Maggiolo ◽  
Johan Remmelgas ◽  
Susanna Abrahmsén-Alami ◽  
Diana Bernin ◽  
...  
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Coating Process ◽  
Droplet Impingement ◽  
Pharmaceutical Tablets ◽  
Pharmaceutical Tablet ◽  
Capillary Spreading ◽  
Spreading Time ◽  
Good Agreement

AbstractThe quality of a coated pharmaceutical tablet can be strongly affected by the interactions of water droplets with the porous substrate during processes such as coating process. Three different mechanisms co-exist in the coating process: water spreading, absorption and evaporation. Disentangling the fundamental understanding of these phenomena can therefore be crucial for achieving a higher quality of the products (e.g. a longer shelf-life of the tablets) and for controlling the efficiency of the process. This paper aims to investigate the spreading and absorption mechanisms after droplet impingement on a tablet using a Lattice-Boltzmann methodology. Our numerical results (droplet height and spreading, penetration depth and absorbed volume) are in a good agreement with experimental data and numerical simulations available in the literature. In particular, the spreading phase is characterised by the capillary spreading time scale, as confirmed by previous studies. In contrast to previous studies, we find that the absorption process begins at times shorter than the capillary spreading time but with a different power-law in the absorbed volume. We explain this behaviour through a modified Washburn law that takes into account three-dimensional effects. Our data can be used as a benchmark to test novel mathematical models.

Simulation of Fluid Flow Through a Granular Bed

2006 ◽  
Author(s):  
Arezou Jafari ◽  
S. Mohammad Mousavi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Packed Bed ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Wide Range ◽  
Duct Geometry ◽  
Flow Through

Numerical study of flow through random packing of non-overlapping spheres in a cylindrical geometry is investigated. Dimensionless pressure drop has been studied for a fluid through the porous media at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), and numerical solution of Navier-Stokes equations in three dimensional porous packed bed illustrated in excellent agreement with those reported by Macdonald [1979] in the range of Reynolds number studied. The results compare to the previous work (Soleymani et al., 2002) show more accurate conclusion because the problem of channeling in a duct geometry. By injection of solute into the system, the dispersivity over a wide range of flow rate has been investigated. It is shown that the lateral fluid dispersion coefficients can be calculated by comparing the concentration profiles of solute obtained by numerical simulations and those derived analytically by solving the macroscopic dispersion equation for the present geometry.

A numerical study of the thermally induced stress distribution in a rotating hollow disc heated by a moving heat source acting on one of the side surfaces

2009 ◽  
Vol 223 (8) ◽  
pp. 1877-1887 ◽  
Author(s):  
M S Genç ◽  
G Özşik ◽  
H Yapicr
Keyword(s):  
Thermal Stress ◽  
Heat Source ◽  
Stress Ratio ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Surface ◽  
Angular Speed ◽  
Moving Heat Source ◽  
Ambient Conditions ◽  
Wide Range

This study presents the effects of a moving heat source (MHS) on a rotating hollow steel disc heated from its one side surface under stagnant ambient conditions. As the disc rotates around the z-axis with a constant angular speed Ω, the heat source moves along from one radial segment to the next radial segment in the radial direction on the processed surface at the end of each revolution of the disc. Three-dimensional (3D) numerical calculations are performed individually for a wide range of thermal conductivity λ of steel and for different Ωs. In order to obtain the thermal stress per heat flux intensity q0, it is assumed that the thermo-physical properties of the disc do not change with temperature. The maximum effective thermal stress ratio varies in the range of 22–134 °C depending on λ and Ω. While the MHS passes from one radial segment to the next radial segment, it causes an additional steeping of the effective thermal stress. However, when the values of λ and Ω are increased, the maximum effective thermal stress ratio can be reduced by a considerable amount.

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