The first two parts of this study showed by experiment and by large-eddy simulation that, in mixing layers formed of processions of spanwise-oriented vortex structures, there is a fundamental change in the dynamics of the large-structure growth at what has been called the ‘mixing’ transition. This third part examines the relationship of the post-transition ‘organised’ flow to the mixing layer of classical turbulence theory. Further large-eddy simulations are presented which, like some of the experiments reported in Part 1, have captured the mixing layer in both its classical and organised turbulent states, thereby allowing them to be characterised separately. The simulation results are then used to calibrate model-free integral analyses of the dynamics of the mixing layer's spatial growth. It is shown that the organised and classical flows are alternative self-preserving turbulent flow states involving fundamentally different exchanges of mass, momentum and energy, one or other of which emerges naturally in particular realisations depending on the initial conditions.

Scholars of various backgrounds have noted how societies across the globe have come to rely on more and more policing and incarceration since the late 1970s. To date, however, detailed analyses of the causes and consequences of this “punitive turn” have been limited to the Global North, with the vast majority of studies focused on the expansion of states’ capacity for violence. This article offers a corrective to the global study of the punitive turn by tracing the rise of South Africa’s private security industry from its inception in the late apartheid period to its current position as one of the largest of its kind in the world. Using newspaper reports, archival material from the apartheid state’s security apparatus, and ethnographic interviews of former and current members of the security industry, it shows how counterinsurgency doctrine, civil war, and deindustrialization shaped South Africa’s punitive turn, precipitating a process where violence was devolved from the state to private actors, including local militias, vigilante groups, and private security firms. This process, it is argued, is far from anomalous, and should be seen as a paradigm for the way the post-1970s punitive turn has unfolded in the majority of the world.

The internal flow within an evaporating sessile droplet has intriguing fluid mechanics important to various microfluidics applications. In the present study, a phenomenon is observed through numerical methods wherein the buoyancy-driven flow structure inside a droplet on a non-wetting substrate transitions from an axisymmetric toroidal vortex flow to a non-axisymmetric single vortex flow with increase in the substrate temperature. As the axisymmetric nature of the droplet flow field and evaporation characteristics are broken, the internal velocity accelerates significantly. The transition, which is attributed to a flow instability inside the droplet, is more prone to occur as the droplet volume or the contact angle increases. The onset of the flow transition is analysed as the amplification of a small perturbation, thereby establishing a correlation between the flow instability and the Rayleigh number (Ra). Specifically, when Ra exceeds some critical value, the onset of the flow transition is observed, which explains the effects of substrate temperature and droplet volume on the internal flow. Next, the influence of the droplet contact angle on the critical Ra was investigated, and the underlying reasons were analysed. Finally, we discuss the heat transfer efficiency within the droplet and analyse why the internal flow tends to transition to a non-axisymmetric flow pattern from an energy minimization perspective.

Before World War I, the Ottoman Empire ruled the southwestern region of the Arabian Peninsula. However, unlike other Ottoman territories in Eastern Europe and the Middle East, the fate of this region was not decided during the Paris Peace Conference. This created a vacuum of power that allowed the local elites of Arabia to engage in a lengthy process of conflict, negotiations, peace talks, and the exchange of ideas to resolve issues of legitimacy, sovereignty, borders, and cultural differences. This article argues that these local elites of Arabia developed an alternative model of statehood and sovereignty that persisted until the outbreak of the Gulf War in 1990. The immediate result of this new model was the separation of al-Mikhlāf al-Sulaimānī region and the transformation of the people of the Najrān region into a sectarian group.

Synthetic textiles, such as polyester, are resistant to natural degradation and constitute approximately 65% of global circulating textile fibers, posing a significant environmental challenge due to their persistence in ecosystems. The global textile industry is responsible for nearly 10% of total global carbon emissions annually and increasing environmental waste. One emerging solution to the industry’s negative environmental impacts is bio-based textile materials that are biodegradable and low-carbon to reduce dependencies on petroleum oil. This paper presents the evolutionary design journey and novel development of earth- and bio-based wearable textiles, coined as BioMud Fabrics, which consist entirely of geo- and bio-based materials. The qualitative and quantitative research-by-design methodological toolkit includes material characterization analysis, microstructural analysis using scanning electron microscopy (SEM) and macro-scale structural characterization using tearing tests following ASTM D5587. The developed fabrics were then applied in a series of speculative design demonstrations with fashion design serving as a central case study. This research uniquely combines material science and engineering with exploratory fashion design and architectural practices with the goal of offering radically innovative biomaterials in an effort to shift towards a more circular material paradigm.

An experimental study has been conducted on the near wake of a 6 : 1 spheroid, in both uniform and stratified backgrounds. The pitch angle, $\theta$, was varied from $0^\circ \text { to }20^\circ$. When $\theta = 0^\circ$, stratification decreases the characteristic wake element spacing so a characteristic Strouhal number ($St$) increases from 0.32 to 0.4. However, a similar measure scaled on wake momentum thickness shows the wake spacing to converge on those measured for other bluff and streamlined bodies. There is an apparent effect of Reynolds number, which changes the location of separation lines and hence the initial wake thickness. When $\theta > 0^\circ$, the wake is a combination of the usual drag wake together with a collection of streamwise vortices that have separated from the body, and this wake geometry can evolve in ways that are measurably different from the zero incidence case. These differences may be limited to the near wake, as the later evolution appears to converge with previous bluff- and streamlined bodies, with normalised wake height, $L_V = 0.5$ and centreline velocity, $\bar {u}_0 = 0.3$ at $Nt = 10$, as the early wake enters the non-equilibrium regime with similar values to previously studied stratified wakes. In the presence of density stratification, the inclined wake itself generates large-scale internal wave undulations with time scale $2{\rm \pi} /N$, even when the background stratification is not strong and a body-based Froude number is $O(10)$. The geometry and strengths of the primary streamwise vortices are not symmetric, mirroring previous results from experiments and computations in the literature.