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Though ubiquitous in many engineering applications, including drug delivery, the compound droplet hydrodynamics in confined geometries have been barely surveyed. For the first time, this study thoroughly investigates the hydrodynamics of a ferrofluid compound droplet (FCD) during its migration in a microchannel under the presence of a pressure-driven flow and a uniform external magnetic field (UEMF) to manipulate its morphology and retard its breakup. Finite difference and phase-field multiple-relaxation time lattice Boltzmann approaches are coupled to determine the magnetic field and ternary flow system, respectively. First, the influence of the magnetic Bond number (
${Bo}_m$) on the FCD morphology is explored depending on whether the core or shell is ferrofluid when the UEMF is applied along 
$\alpha =0^\circ$ and 
$\alpha =90^\circ$ relative to the fluid flow. It is ascertained that imposing the UEMF at 
$\alpha =0^\circ$ when the shell is ferrofluid can postpone the breakup. Intriguingly, when the core is ferrofluid, strengthening the UEMF enlarges the shell deformation. Afterwards, the effects of the capillary number (
${Ca}$), density ratio, viscosity ratio, radius ratio and surface tension coefficients are scrutinised on the FCD deformation and breakup. The results indicate that augmenting the core-to-shell viscosity and density ratios accelerates the breakup process. Additionally, surface tension between the core and shell suppresses the core deformation. Moreover, increasing the 
${Ca}$ intensifies the viscous drag force exerted on the shell, flattening its rear side, which causes a triangular-like configuration. Ultimately, by varying 
${Bo}_m$ and 
${Ca}$, five distinct regimes are observed, whose regime map is established.
Micro-UAV systems used for metric purposes are highly capable of capturing relatively high-resolution, chromatically stable aerial images at low altitudes. In micro-UAV-based aerial imaging-based structure-from-motion (a-SfM) applications, the flight mission planning problem can be customised to achieve different objectives. The requirement for minimising the time spent in the air, which is crucial for energy conservation, can be achieved by designing the shortest possible flight path. Spatial resolution in the captured aerial images can be significantly preserved by maintaining the ground sampling distance (GSD) value within a 95
${\rm{\% }}$ confidence interval throughout the flight path. Fuel efficiency can be improved by minimising the number of turning manoeuvers required to follow the flight path during the flying mission. In this paper, four distinct flight mission planning processes are delineated to enable the energy-efficient and effective implementation of aerial imaging missions, with their associated parameters optimised using the colony-based search algorithm (CSA). The obtained experimental results demonstrate that the proposed flight mission planning processes are highly successful in the energy-efficient and effective execution of aerial imaging missions.
We explored the dynamics of Taylor–Couette flows within square enclosures, focusing primarily on the turbulence regime and vortex behaviour at varying Reynolds numbers. Laboratory experiments were conducted using particle image velocimetry for Reynolds numbers 
$Re_{\varDelta }\in [0.23, 4.6]\times 10^3$ based on the minimum gap 
$\varDelta /d = 1/16$, 
$1/8$ and 
$1/4$, where 
$d$ is the cylinder diameter, or 
$Re\in [1.8, 9.8]\times 10^3$ based on 
$d/2$. At lower 
$Re$, the flow was dominated by well-defined Taylor and Görtler vortices, while higher 
$Re$ led to a turbulent state with distinct motions. Space–time radial velocity analysis revealed persistent Taylor vortices at lower 
$Re$, with larger gaps but increased turbulence, and irregular motions at higher 
$Re$, with smaller gaps. Velocity spectra reveal that the energy distribution is maintained at frequencies lower than the integral-type frequency 
$f_I$ across varying 
$\varDelta$ due to the dominance of large vortices. However, there is a monotonic increase in energy at higher frequencies beyond 
$f_I$. The reduced characteristic frequency 
$f_I\varDelta /\omega _ir_i \sim 1/10$ indicates that these motions scale linearly with angular velocity, and inversely with the gap. Proper orthogonal decomposition (POD) and spectral POD were used to distinguish between Taylor and Görtler vortices, showing the effects of gap size and the associated energy cascade. Linear stability analysis included as complementary support revealed primary instability of the Taylor vortex, which is similar to the circular enclosure, along with multiple corner modes that are unique to the geometry.
