Hendrik Willem Marie Hoeijmakers

Numerical Simulation of SLD Ice Accretions

In this study, computational methods are presented that compute ice accretion on multiple-element airfoils in specified icing conditions. The ?Droplerian? numerical simulation method used is based on an Eulerian method for predicting droplet trajectories and the resulting droplet catching efficiency on the surface of the configuration. Flow field and droplet catching efficiency form input for Messingers model for ice accretion. The droplet trajectory method has been constructed such that the solution of any flow-field simulation (e.g., potential-flow, Euler equations) can be used as input for the finite-volume solution method. On an unstructured grid the spatial distribution of droplet loading and droplet velocity are obtained. From these quantities the droplet catching efficiency is derived. Of special interest in this study are the Supercooled Large Droplets (SLD). The simulation of SLD requires a specific splashing model.For a single-element airfoil a good agreement is found with the Lagrangian method 2DFOIL-ICE and with experimental results. The comparison of the catching efficiency predicted by both simulation methods is good for the smaller droplets. For larger (SLD) droplets the splashing and rebound models are a significant improvement to the catching efficiency results when compared with the experimental results.

Simulation of Ice Accretion on Airfoils during Flight

In this study, a computational method is presented that computes ice accretion on airfoils in specified icing conditions. A good agreement is found with the ice shapes predicted by other computational methods. Agreement with the experimental ice shapes is fair. Also, the implementation and application of a mathematical model of a thermal anti-icing system in the ice accretion simulation code 2DFOIL-ICE is presented. The numerical code has proved to be able to calculate the main parameters of an airfoil anti-icing system, such as: solid surface temperatures (for the wetted region), runback water flow and convection heat transfer coefficient distributions along the external surface.

Modelling of Non-Spherical Particle Evolution for Ice Crystals Simulation with an Eulerian Approach

In this study a comparison is made between results from three Eulerian-based computational methods that predict the ice crystal trajectories and impingement on a NACA-0012 airfoil. The computational methods are being developed within CIRA (Imp2D/3D), ONERA (CEDRE/Spiree) and University of Twente (MooseMBIce). Eulerian models describing ice crystal transport are complex because physical phenomena, like drag force, heat transfer and phase change, depend on the particles sphericity. Few correlations exist for the drag of non-spherical particles and heat transfer of these particles. The effect or non-spherical particles on the collection efficiency will be shown on a 2D airfoil.

Synthetic jet actuation for load control

The reduction of wind turbine blade loads is an important issue in the reduction of the costs of energy production. Reduction of the loads of a non-cyclic nature requires so-called smart rotor control, which involves the application of distributed actuators and sensors to provide fast and local changes in aerodynamic performance. This paper investigates the use of synthetic jets for smart rotor control. Synthetic jets are formed by ingesting low-momentum fluid from the boundary layer along the blade into a cavity and subsequently ejecting this fluid with a higher momentum. We focus on the observed flow phenomena and the ability to use these to obtain the desired changes of the aerodynamic properties of a blade section. To this end, numerical simulations and wind tunnel experiments of synthetic jet actuation on a non-rotating NACA0018 airfoil have been performed. The synthetic jets are long spanwise slits, located close to the trailing edge and directed perpendicularly to the surface of the airfoil. Due to limitations of the present experimental setup in terms of performance of the synthetic jets, the main focus is on the numerical flow simulations. The present results show that high-frequency synthetic jet actuation close to the trailing edge can induce changes in the effective angle of attack up to approximately 2.9°.

Eulerian method for ice crystal icing with application to particle trajectories and accretion on a three-element airfoil

The aim of this study is to show the application of an Eulerian method for ice crystal icing to a three-element airfoil in high-lift configuration. The ice crystals have been modeled as non-spherical particles which are subject to convection and/or phase change along their trajectories. On impact with the airfoil surface the ice crystals will either stick to the surface or rebound from the airfoil unchanged or as a number of fragments. The evolution of the secondary cloud containing these rebounded or shattered fragments is computed as well. It is concluded that an Eulerian method is a convenient method to compute trajectories of (melting) ice crystals for a high-lift configuration such as a three-element airfoil if certain limitations with regard to the secondary cloud of particles are taken into account.

Computational Method for Ice Crystal Trajectories in a Turbofan Compressor

In this study the characteristics of ice crystals on their trajectory in a single stage of a turbofan engine compressor are determined. The particle trajectories are calculated with a Lagrangian method employing a classical fourth-order Runge-Kutta time integration scheme. The air flow field is provided as input and is a steady flow field solution governed by the Euler equations. The single compressor stage is represented using a cascaded grid. The grid consists of three parts of which the first and the last part are stator parts and the centre part is a rotor.nnEach particle is modelled as a non-rotating rigid sphere. The remaining model does allow the exchange of heat and mass to and from the particle resulting in a mass, temperature and phase change of the particle. The phase change is based on a perfectly concentric ice core-water film model and it is assumed that the particle is at uniform temperature.nnThe results for the collection efficiency, particle temperature and amount of evaporated mass will be shown for two extreme scenarios. The first simulation is carried out at standard conditions for a Boeing-747 at cruising conditions using the International Standard Atmosphere (ISA) at that altitude, i.e. at 10,650 m. The second simulation is carried out at lower altitude where the existence of supercooled liquid water is thought to be unlikely. Both simulations are carried out at two different temperatures and for either dry or saturated air. The range of particle diameters is set from 10 to 500 micrometres.

Splashing Model for Impact of Supercooled Large Droplets on a Thin Liquid Film

Compared to conventional icing additional droplet phenomena have to be accounted for in icing caused by supercooled large droplets (SLD) such as splashing, rebound, breakup and deformation. In this study the effect of the presence of a thin liquid film of water on the surface has been investigated. This liquid layer can arise when SLD droplets freeze only partially following impact on the airfoil. The effect of the liquid film is simulated by using the wall shear stress and by assuming a linear velocity profile in the liquid layer. The shear stress is calculated by coupling an integral boundary-layer method to a potential ow method. An improved splashing model has been implemented in the existing com-putational method. This splashing model consists of a deposition model that accounts for splashing during impact of droplets on a liquid layer. In an extension to this model different solidification models have been investigated to estimate the time of solidification of a liquid splat produced on the surface after impact. One is a planar solidification model which is described by the Stefan problem for heat conduction and which is mostly controlled by diffusion. The second model is based on dendritic solidification, which is rapid and gov-erned by kinetics. The results of the deposition model on SLD ice accretion are compared with data from experiments on a NACA-23012 airfoil and on a NACA-0012 airfoil. Good agreement is found.

Development of a Numerical Method for Simulating Transonic Multiphase Flows

A generally applicable numerical method has been developed to simulate the flow of a mixture of condensing real gases. The flow is described by the Euler equations of gasdynamics, whereas the thermodynamically non-equilibrium process of condensation is modeled by an integral description method, i.e. Hill’s method. The fluid considered, be in gaseous or liquid phase, may be a mixture of several different inert or condensing components. The development of an equation of state that accurately describes the behavior of a real gas (i.e. a gas at high pressure) is important, e.g. for natural gas applications. The developed equation of state satisfies Maxwell’s thermodynamic relations.

A High-Order Accurate Compact Finite Difference Algorithm for the Incompressible Navier-Stokes Equations

The present paper describes a newly developed Navier-Stokes solver of fourth-order global spatial accuracy and second-order accuracy in time. The algorithm uses an explicit discretisation for the convection terms and an implicit formulation for the viscous terms. Compact-differences are used in the spatial discretisation. They offer a combination of flexibility of boundary conditions and spectral-like resolution (Lele(1992)).

Eulerian Method for Ice Crystal Icing

In this study, an ice accretion method aimed at ice crystal icing in turbofan engines is developed and demonstrated for glaciated as well as mixed-phase icing conditions. The particle trajectories ...