SP6 High IWC Tools and Simulation Development – 2nd year progress
The majority of the SP6 objectives set for the second year of the project have been achieved.
In what follows the significant results of each WP of SP6 are presented.
WP63 : Ice particles trajectory model
Melting Experiment
In the figure below, the evolution of the projected area during melting of an ice particle, suspended in an acoustic levitator, is shown, including pictures of the melting ice particle. The ice particle rotates (3) before the start of the melting process due to asymmetrical acoustic forces acting on the irregular particle. The melting process (2) is started 0.1 s after the start of the video recording (1). Within some milliseconds after the start of the melting process, the first changes in the particle shape can be observed due to the build-up of meltwater films on its surface. After few more seconds, the ice particle stops its rotational movement due to the predominant aerodynamic forces and shows either almost no movement or some shaking movements (4). When the first spherical shape is reached (5) and the ice core is completely surrounded by meltwater, the ice core starts to rotate and its diameter continuously decreases until the particle is fully melted (6). After the melting process, the projected area decreases linearly with time.
These experiments will contribute to the modelling of the melting process of irregular ice particles.
For further information:
Hauk, T., Roisman, I., and Tropea, C., “Investigation of the Melting Behaviour of Ice Particles in an Acoustic Levitator,” 2014, AIAA 2014-2261, 11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 16-20 June 2014, Atlanta, GA.
WP64 : Ice particles impingement model
Impact Experiment
The following two sequences show so-called catastrophic fragmentation of ice particles on impact. A polished aluminum surface was used as impact surface. In the first figure, an irregular particle with a maximum dimension of approx. 362 µm and an impact velocity of 48 m/s fragments into several small particles. A small leftover sticks to the surface at the impact location. In the second figure, an almost spherical particle with a diameter of approx. 956 µm impacts at a velocity of 36 m/s.
These experiments will contribute to the modelling of ice particle impact processes.
For further information:
Hauk, T., Roisman, I., and Tropea, C., “Investigation of the Impact Behaviour of Ice Particles,” 2014, AIAA 2014-3046, 6th AIAA Atmospheric and Space Environments Conference, 16-20 June 2014, Atlanta, GA.
WP65 : Ice particles accretion model
Micro-scale modeling of ice layer accretion, melting and shedding
Under certain conditions a porous ice/water layer builds up on hot surfaces in aircraft engines or on heated probes and eventually leads to their malfunction. In this study a numerical algorithm for the computation of heat and mass fluxes within and over the system boundaries of such a porous ice/water layer is developed. The code predicts the amount of liquid in the porous layer, which potentially can help to model ice shedding. This solver accounts for phase transitions between the solid, liquid and gaseous state as well as for the heat fluxes in the substrate on which the ice accretes and in the porous ice/water layer. A verification of the code is carried out using test cases for which analytical or experimental data are available. These cases encompass all the physical mechanisms which eventually lead to ice accretion and shedding. Numerically predicted results show excellent agreement with available data in all the test cases. Existing accretion experiments are well reproduced by means of the code and yield insight into the governing physical processes. Moreover, an analysis of parameters of high influence on the accretion reveals limits for icing.
To view the progress performed within SP6 the first, third and fourth year of the project please follow the related links.
For further information:
D. M. Kintea, M. Schremb, I. V. Roisman and C. Tropea “Numerical investigation of ice particle accretion on heated surfaces with application to aircraft engines,” 2014, AIAA 2014-2820, 11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 16-20 June 2014, Atlanta, GA.
