The resultant data provide a quantitative assessment of the effects of these perforate, single-layer liner parameters on the acoustic impedance of the liner. Similar liners were tested in the NASA Langley Research Center grazing incidence tube to determine their response in the presence of grazing flow. Normal incidence acoustic impedances were determined for eight acoustic liners, consisting of punched aluminum facesheets bonded to hexcell honeycomb cavities.

Hexcells and by the name I mean all three games in the trilogy as one super-game, like a Transformer of puzzling perfection is not only the best puzzle game on sale, but it’s the best puzzle. In a far larger scale than even that implies. Is a thing I’ve said before, and maintain. The current report provides the results of a parametric study, in which a finite element method was used to assess the effects of variations of the following geometric parameters on liner impedance, with and without the presence of grazing flow: percent open area, sheet thickness, sheet thickness-to-hole diameter ratio and cavity depth. Hexcells is the best puzzle game ever made. Recent efforts have provided advances in impedance eduction methodologies that offer more accurate determinations of acoustic liner properties in the presence of grazing flow.

Numerous models have been developed to predict the acoustic impedance of these liners in the presence of grazing flow, and to use that information with aeroacoustic propagation codes to assess nacelle liner noise suppression. The second game, Hexcells Plus, arrived in December, after we’d already decided the original deserved a spot in our top games of 2013. The original Hexcells appeared from nowhere in my inbox in September, and I fell instantly in love. Current aircraft engine nacelles typically contain acoustic liners consisting of perforated sheets bonded onto honeycomb cavities. I wasn’t subtle about how much I enjoyed Hexcells last year.

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