The connection between the drag and vorticity dynamics for viscous flow over a bluff body is explored using the Josephson–Anderson (J–A) relation for classical fluids. The instantaneous rate of work on the fluid, associated with the drag force, is related to the vorticity flux across the streamlines of a background potential flow. The vorticity transport itself is examined by aid of the Huggins vorticity-flux tensor. The analysis is performed for three flows: flow over a sphere at Reynolds numbers $Re=200,3700$, and flow over a prolate spheroid at $Re=3000$ and $20^{\circ }$ incidence. In these flows, the vorticity transport shifts the flow away from and towards the ideal potential flow, with a net balance towards the former effect thus making an appreciable contribution to the drag. The J–A relation is first demonstrated for the flow over a sphere at $Re=200$. The drag power injection is related to the viscous flux of azimuthal vorticity from the wall into the fluid, and the advection of vorticity by the detached shear layer. In the wake, the azimuthal vorticity is advected towards the wake centreline and is annihilated by viscous effects, which contributes a reduction in drag. The analysis of the flow over a sphere at $Re=3700$ is reported for the impulsively started and stationary stages, with emphasis on the effects of unsteady two-dimensional separation and turbulent transport in the transitional wake. The turbulent flux in the wake enhances the transport of mean azimuthal vorticity towards the wake centreline, and is the main driver of the recovery of enthalpy between the rear point of the sphere and far downstream. The rate of work on the fluid by the drag force for a prolate spheroid is mostly due to the transport of vorticity along the separated boundary layers. Primary and secondary separation contribute oppositely to the power injection by the drag force, while the large-scale vortices only re-distribute vorticity without a net contribution. A mechanism for secondary separation is proposed based on the theory of vortex-induced separation.

Amateur and professional athletes often consume protein supplements to accelerate muscle gain; however, it has been suggested that these products not only are associated with risks when consumed excessively. Several recent reports have indicated that certain products are contaminated with heavy metals. Therefore, in this study, we aimed to investigate protein powders in Hungary for heavy metal contamination. A total of 22 commercially available protein powders (including whey, vegan, and beef based) were purchased on the internet for testing. We analysed the samples using laser-induced breakdown spectroscopy (LIBS) and inductively coupled plasma mass spectrometry (ICP-MS) to assess heavy metal contamination. The products were analysed for the presence of 16 elements (Be, Al, Cr, Mn, Co, Ni, Cu, As, Se, Rb, Cd, Sb, Cs, Ba, Hg, and Pb). The LIBS spectral analysis revealed the characteristics of the protein elements (C, C2, H, N, and O) and alkaline metals (Ca, Na, K, and Mg), which were consistent with the previous results. Neither LIBS nor ICP-MS measurements detected significant heavy metal content in the investigated samples above the limit specified in the regulations. Heavy metal contamination of protein supplements can be a serious health threat. Based on the varied results of the previous studies, it is prudent to include testing for heavy metals as part of the routine and mandatory quality control of these products.

This study investigates the interactions between flexural-gravity waves and interfacial waves in a two-layer fluid, focusing on wave blocking. Both liquid layers are of finite depth bounded on top by a viscoelastic thin plate. Both liquids are incompressible and inviscid, and their flows are two-dimensional and potential. Linear wave theory and a linear equation of a thin floating viscoelastic plate of constant thickness are used. We analyse the phenomenon of wave blocking and Kelvin–Helmholtz (KH) instability in a two-layer fluid with a discontinuous background mean flow. A quartic dispersion relation for frequency as a function of wavenumber and other parameters of the problem is derived. Two cases of uniform current and layers moving with different velocities are studied. Wave blocking occurs when roots of the dispersion relation coalesce without accounting for plate viscosity, leading to zero group velocity. Our findings indicate that wave blocking can occur for both flexural-gravity and interfacial waves under various frequency and current speed conditions, provided that plate viscosity is absent. The role of different parameters and the flow velocities of the upper and lower layers are investigated in the occurrence of wave blocking and KH instability. The loci of the roots of the dispersion relation involving plate viscosity depict that no root coalescence occurs irrespective of the values of wavenumber and frequency in the presence of plate viscosity. The amplitude ratio of the interfacial wave elevation to that of floating viscoelastic plate deflection exhibits the dead-water phenomenon as a density ratio approaches unity.

Reconstructing Quaternary-timescale environmental change in drylands provides insights into styles and rates of change in response to direct insolation forcing and variations in global temperature, ice volume and sea level. Changes to the relatively inhospitable environments presented by drylands are also central to debates about the migration and adaptability of hominin species. This review outlines approaches used for reconstructing past environments, which use dated sequences of environmental proxies – the properties of physical sediments, chemical precipitates and biological materials. In addition, climate model simulations can explore responses to known climatic forcing factors. Advances in both approaches remain situated within conceptual frameworks about dryland responses to: (i) cyclical changes in the Earth’s orbit around the sun, either mediated via the global cryosphere during glacial–interglacial cycles (~100 ka periodicity during the last ~0.9 Ma), or mediated via the response of the global monsoon with ~23 ka periodicity (precession) and (ii) millennial-scale climatic shifts, which are thought to originate outside drylands, within the North Atlantic.

In this review, three examples are outlined to demonstrate areas of emerging consensus and remaining contradictions: (1) speleothem and tufa growth records that span hundreds of thousands of years (ka), (2) conditions at the last glacial maximum (LGM) and (3) proxies recording millennial-scale events. Precessional-scale forcing of the monsoon is not always observed, with apparent mediating roles from glacial boundary conditions in parts of the northern hemisphere (NH) and from interglacial boundary conditions in parts of the southern hemisphere (SH). The LGM in drylands was initially conceptualised as experiencing pluvial (wet) conditions, which shifted to a glacial aridity paradigm, and is again shifting to a pattern of global heterogeneity, in which some drylands were wetter-than-present and others drier. However, there remain contradictions between environmental proxies and model simulations, and spatial heterogeneity is observed within many drylands. Dryland proxies that record millennial-scale events demonstrate clearly the importance of climatic teleconnections across the globe in influencing dryland hydroclimate. The records of Quaternary dryland change across a range of timescales get used alongside simulations of ecosystem response through time, hominin habitat and even hominin physiology to better understand likely hominin dispersals through dryland regions.

A numerical study is presented on flow-induced vibration of a circular cylinder, under the effect of a downstream stationary cylinder-induced proximity interference. The interference-induced various types of gap-flow regimes and characteristics of vibration and gap-flow rate $Q^*_g$ are presented, by considering various non-dimensional gaps $G^* = 0.1{-}2.5$ and reduced velocities $U^* = 3{-}20$ at a constant Reynolds number $Re = 100$, mass ratio $m^*= 2$ and damping ratio $\zeta = 0.005$. Decreasing $G^*$ or increasing proximity leads to the four gap-flow regimes: bi-directional gap flow at $G^* \geqslant 1.0$, uni-directional non-orthogonal gap flow at $G^* = 1.5{-}1.0$, uni-directional orthogonal gap flow at $G^* \leqslant 0.5$ and uni-directional one-sided gap flow at $G^* \leqslant 0.3$. Further, the respective regimes at larger $U^*$ are associated with proximity-induced modified vortex-induced vibration (PImVIV), proximity-induced galloping (PIG), transitional PImVIV–PIG, and proximity-induced staggered vibration (PISV). Quantitative presentation of maximum gap-flow rate $Q^*_{{g,max}}$, phase $ \phi _g$ (between $Q^*_{g}$ and displacement $y^*$) and phase portraits ($Q^*_{g}$ versus $y^*$) provides clear demarcation between the various gap-flow regimes. Flow mechanisms are presented for the PImVIV, PIG and PISV responses. For the PIG, the mechanism is presented for the first time on generation of galloping instability, asymptotically increasing $A^*$ and existence of optimum gap $G^* = 0.5$ for the maximum amplitude. This work is significant as it provides new insights into the proximity interference-induced gap-flow dynamics between two cylinders, associated flow mechanism for both vibration mitigation and enhancement and promising potential applications for energy harvesting.