This article reports an analysis of the first detailed chemistry direct numerical simulation (DNS) of a high Karlovitz number laboratory premixed flame. The DNS results are first compared with those from laser-based diagnostics with good agreement. The subsequent analysis focuses on a detailed investigation of the flame area, its local thickness and their rates of change in isosurface following reference frames, quantities that are intimately connected. The net flame stretch is demonstrated to be a small residual of large competing terms: the positive tangential strain term and the negative curvature stretch term. The latter is found to be driven by flame speed–curvature correlations and dominated in net by low probability highly curved regions. Flame thickening is demonstrated to be substantial on average, while local regions of flame thinning are also observed. The rate of change of the flame thickness (as measured by the scalar gradient magnitude) is demonstrated, analogously to flame stretch, to be a competition between straining tending to increase gradients and flame speed variations in the normal direction tending to decrease them. The flame stretch and flame thickness analyses are connected by the observation that high positive tangential strain rate regions generally correspond with low curvature regions; these regions tend to be positively stretched in net and are relatively thinner compared with other regions. High curvature magnitude regions (both positive and negative) generally correspond with lower tangential strain; these regions are in net negatively stretched and thickened substantially.

The mechanical properties and internal friction (damping capacity) of Mg–Zn–Y alloys with a long-period stacking ordered (LPSO) structure at different Y/Zn atomic ratios (2/1, 3/2 or 4/3) in cast and extrusion were investigated. It was found that the as-cast Mg–Zn–Y alloys with different Y/Zn atomic ratios possess a single LPSO phase with the same stable 18R-type structure. Among the three alloys, the alloy with 3/2 atomic ratio yields the highest damping capacity in low- and high-strain amplitude stages. Two damping peaks particularly P1 and P2 are detected in the Mg–Zn–Y alloy with 3/2 atomic ratio at approximately 108 and 220 °C, respectively. These results may be attributed to few solute atoms in Mg matrix and grain boundaries. In addition, the studied alloy with 3/2 atomic ratio exhibits excellent comprehensive properties in as-cast and as-extruded states; this alloy yields an ultimate tensile strength of 346 MPa and maintains a certain damping capacity (Q−1 > 0.01) in extrusion.

Water infiltrated nanoporous glasses have a damping peak at about 1 Hz (4.6 nm pore size) and 6 Hz (8.8 nm pore size) at room temperature; their relaxation strengths are consistent with the damping mechanism in which water flows from the regions of compression to those of tension. However, the damping peaks disappear when water content is below 60% for the 4.6 urn pore size glass and 40% for the 8.8 urn pore size glass. These water contents correspond to about a 0.85 and 1.0 urn thick interfacial water layer on the internal surfaces of the nanoporous glasses. The adsorbed layer contributes only to the damping background. Finally, dependencies of relaxation time on sample thickness, bulk modulus and viscosity agree well with the predictions of the model.