3 Results
The measured crater diameters and depths for all of our iSALE/CTH simulations are shown in Table 4. We consider the spatial resolution (cell size) the error for the simulations and propagate to include error from the measurements (i.e., digital caliper and height gauge precision) when computing the relative crater depths and diameters between simulations and experiments (Figures 4 and 5). Both the simulated and experimental crater dimensions are measured from the pre-impact surface (y=0). In one case, in simulation #2.04, which is of the smallest size impactor at very low target temperature and very high velocity (end member scenarios for all three variables) that became unstable, producing dramatic numerical artifacts. To address this problem, we performed simulations for experiment # 2.04 at +1 K, +5 K and with a finer resolution. The values reported in this work are from the simulation at 119 K (+1 K).
Our simulations reproduce the crater dimensions reported in Marchi et al. (2020) on average within ~15% of the experimental values, with better precision when using laboratory-derived JC parameters for the Fe-Ni ingots (Figure 4). Notably, our iSALE simulations reproduce the crater diameters measured from our experiments into ingot targets on average with ~98.2% accuracy (denoted by the circular markers in Figure 4). Crater diameters into Gibeon targets are on average 9.2 ± 2.7% larger than the experiments. Crater depths are reproduced with iSALE within 3.5 ± 1.5% of the experimental values for ingots and within 11.6 ± 3.5% for Gibeon targets.
Both #2.06 and #2.11 impact experiments were into material I-90 (b), with the latter target being at room temperature and the former cooled. When comparing CTH output to iSALE, the crater depth for #2.06 is ~3.8 mm in CTH versus ~3.65 mm in iSALE and for #2.11 is ~5.9 mm versus ~6.35 mm in SALE. The CTH-produced crater diameters are larger (13.0 and 15.8 mm for #2.06 and #2.11) than in iSALE, and both are larger than the experiments. Given the coarser resolution in our CTH simulations, there is a bit more error in the CTH simulations than the iSALE simulations. Both iSALE and CTH show similar trends that cooled targets tend to overestimate crater diameters and depths more than room-temperature targets.