The electroosmotic flow of Oldroyd-B fluids in a 90◦ curved tube with a rectangular section under a direct electric field is studied numerically. By introducing elastic forces into the force balance of viscous, elastic and centrifugal forces, another secondary flow pattern is found in addition to the stable state for Newtonian fluids, i.e., the periodic oscillation state. In this oscillating state, the position of the maximum velocity periodically moves from the centre to the position near the wall. Meanwhile, a symmetric vortex can be periodically observed in the streamline figures.The secondary flow oscillates when the Deborah number De or the dimensionless wall potential ψ is sufficiently large,and the oscillating frequency increases with a larger Deborah number De or a larger dimensionless wall potential ψ.A phase diagram of secondary flow as it depends on the Deborah number De and the dimensionless wall potential ψis presented. There is a critical Deborah number Decr for a given wall potential ψ, and the secondary flow become periodically oscillating at De > De_cr. The critical Deborah number De_cr decreases as the value of the dimensionlesswall potential |ψ| increases. Moreover, the critical Deborah number should be larger than 0.2 even though the wall potential |ψ| further increases, i.e., De_cr > 0.2. At De {less than or equal to} 0.2 the elastic forces are small, the secondary flow is stable rather than oscillating similar to the phenomena of Newtonian fluids.

Inspired by the recent multifluid system with thickness down to microscopic scale during thermal drawing for fiber fabrication, we perform the linear analysis of dewetting instability in multilayer planar sheets. The effects of various physical parameters on the dewetting instability have been extensively investigated, including van der Waals forces, viscosities, surface tensions, and thicknesses. As the thickness of the liquid sheet is reduced down to nanoscales, van der Waals forces become more prominent and lead to the dewetting instability. For the three-layer case ($N=3$), the “para-varicose” mode with larger thickness perturbations plays a dominant role. For the four-layer case ($N=4$), there are several more complicated unstable modes, and the maximum growth rate (${\mathrm{\Omega }}_m$) depends on both fluid properties, and the corresponding eigenamplitudes can switch among various modes. Particularly, a slowest growth rate (${\mathrm{\Omega }}_m^{\text{slow}}$) is identified at a critical thickness of the cladding layer ($H_{\text{cr}}$). Additionally, for the relevant applications of fiber drawing, by changing multilayer structure from $N=3$ to 4 through introducing an additional less viscous sheet, the instability can be enhanced, or, by choosing a suitable thickness of a less viscous sheet, the instability can be reduced. These results not only shed light on controlling the dewetting instability by material selection and structure design, but also provide guidance to achieve functional devices with sophisticated nanostructures either in a single fiber or in integrated fabrics for large-scale textiles.

The hydrodynamic pressure field and wake field generated by an advancing underwater vehicle are used as key factors for its detection and identification. In this paper, a numerical method is established based on the Reynolds-averaged Navier–Stokes equation. Following grid convergence verification for seven kinds of grids, the differences between the hydrodynamic pressure field and wake field are investigated using the gridding method and turbulence model. Subsequently, on a validation basis, the characteristics and correlation of the hydrodynamic pressure field and wake field for an underwater vehicle at different water depths are studied, showing that the SST turbulence model is applicable to underwater vehicle hydrodynamic pressure fields with low grid requirements. A high grid density and the LES turbulence model are needed to accurately capture information about the wake field’s flow field. As the underwater vehicle approaches the bottom, the hydrodynamic pressure field characteristics change significantly, and the wake field characteristics do not significantly change. In the region behind the hull, the influence of the wake field on the hydrodynamic pressure field is complex, but it has a short acting distance. The correlation in the area behind the hull is crucial for identifying, detecting, and tracking targets.

Effective fuel atomization remains a critical bottleneck for combustion stability and emissions control in aero-engines during low-power operations (e.g., cold start, idle), where conventional pressure-swirl atomizers (PSAs) suffer from deteriorated swirling intensity, prolonged primary breakup length, and coarse droplet spectra. To address this, we propose a novel plasma synthetic jet fuel injector (PSJFI), integrating a plasma synthetic jet actuator (PSJA) with a PSA to deliver high-momentum (>100 m/s) pulsed jets directly onto the liquid core near the atomizer orifice. Using high-speed schlieren imaging and LIF/Mie diagnostics, we quantitatively evaluate its atomization performance across a representative range of fuel injection pressures (0.05–0.3 MPa). Results demonstrate that PSJFI achieves significant, pressure-dependent atomization enhancement: at a fuel injection pressure of 0.05 MPa, it reduces primary breakup length by 32.2% and increases spray cone angle by 23.4%, while decreasing Sauter mean diameter (SMD) by up to 27.4%. Crucially, PSJ actuation drives a stage transition in atomization process, transforming the spray from the onion stage to the more developed tulip stage. The enhancement mechanism is attributed to the dual action of shock waves enhancing secondary breakup via turbulence intensification and jets accelerating primary liquid film disintegration. This work establishes PSJFI as a promising, lightweight, and controllable solution for wide-range adaptive operation of next-generation aero-engine combustors.

Recent progress on forming in-fiber nanostructures via filamentation instability during the thermal drawing process is reviewed. This review could motivate future work towards multifunctional fibers with multilayer and multimaterial nanostructures.