Modelling the growth of large rime ice accretions

An investigation into empirical ice density formulations for dry ice growth on cylinders

“…Based on the comparison of the results between the MVD approximation and full droplet distribution spectrum, it can be seen that the MVD approximation works well for higher values of droplet inertia parameter. This agrees with statements by (Makkonen et al, 2018) and (ISO, 2001) that the current icing parameterization is applicable for the range of the overall collision efficiency of 0.07 < E < 0.63 and that for E < 0.1 the icing parameterization using MVD approximation will underestimate the ice accretion, respectively.…”

“…The interest in modeling ice accretion on cylindrical objects primarily comes from preventing structural damage or collapse of objects such as overhead transmission lines or communication masts due to the accreted ice mass leading to dynamical instabilities. The theoretical modelling of icing is covered by ISO 12494, where the icing theory framework is valid for the droplet overall collision efficiency range of 0.07 < E < 0.63 (Makkonen et al, 2018), though, the ISO 12494 model framework scope is rather limited when it comes to the long term modeling of the in-cloud icing events on the power lines and structures. Such long-term icing events can lead to significant ice loads over longer timeframes, where the ice can accrete in multiple "stages" under different operating conditions.…”

Droplet distribution spectrum effects on dry ice growth on cylinders

“…Moreover, other factors, not accounted for in this study, such as surface roughness, sublimation and deposition, viscous and boundary layer effects may become prominent in cases where the inertia parameter is sufficiently low. However, the usage of the CFD tools as with this work, in addition to some recent results (Makkonen et al, 2018) show the CFD simulations are well suited for modeling of the ice accretion at the low values of K. As an example, a graphical comparison of the overall collision efficiency values in the analytical and numerical results is given in Figure 7. The practical meaning of Figure 7 is to display the difference in relative ice accretion values between the analytical and the numerical model in a concise manner.…”

“…al model has a tendency to under estimate the overall collision efficiency for cases, when E < 0.10. Recently, (Makkonen et al, 2018) shown that modern Computational Fluid Dynamics (CFD) tools can achieve good results in modeling of ice accretion on cylinders for cases when E < 0.10, granted full droplet distribution spectrum is used. When it comes to estimating the cloud impingement parameters of ice accretion, X(K, φ), those parameters depend on the droplet inertia parameter (K) and Langmuir parameter φ, which are defined as (ISO, 2001):…”

“…Recently, (Makkonen et al, 2018) performed a series of CFD simulations using the full droplet distribution spectrum.…”