Picking on vulnerable migrants: precarity and the mushroom industry in Northern Ireland

This article examines precarious employment in the context of the mushroom industry in Northern Ireland. Migrant workers engaged in mushroom picking were interviewed in the context of wider research investigating forced labour in Northern Ireland. The research found that, while the boundaries between exploitation and forced labour are complex and difficult to discern, there was some evidence of borderline forced labour, according to ILO definitions. However, workers found themselves on a ‘continuum of exploitation’, where initial engagement with the prospect of decent work was superseded by increasing endurance of exploitative practices, brought about by unequal power relationships with employers originating in immigration status. This is examined in the wider theoretical context of precarity, of which precarious employment comprises a part.

Optimising power take-off of an oscillating wave surge converter using high fidelity numerical simulations

Oscillating wave surge converters are a promising technology to harvest ocean wave energy in the near shore region. Although research has been going on for many years, the characteristics of the wave action on the structure and especially the phase relation between the driving force and wave quantities like velocity or surface elevation have not been investigated in detail. The main reason for this is the lack of suitable methods. Experimental investigations using tank tests do not give direct access to overall hydrodynamic loads, only damping torque of a power take off system can be measured directly. Non-linear computational fluid dynamics methods have only recently been applied in the research of this type of devices. This paper presents a new metric named wave torque, which is the total hydrodynamic torque minus the still water pitch stiffness at any given angle of rotation. Changes in characteristics of that metric over a wave cycle and for different power take off settings are investigated using computational fluid dynamics methods. Firstly, it is shown that linearised methods cannot predict optimum damping in typical operating states of OWSCs. We then present phase relationships between main kinetic parameters for different damping levels. Although the flap seems to operate close to resonance, as predicted by linear theory, no obvious condition defining optimum damping is found.