A RANS modelling approach for predicting powering performance of ships in waves

In this paper, a modelling technique for simulating self-propelled ships in waves is presented. The flow is modelled using a RANS solver coupled with an actuator disk model for the propeller. The motion of the ship is taken into consideration in the definition of the actuator disk region as well as the advance ratio of the propeller. The RPM of the propeller is controlled using a PID-controller with constraints added on the maximum permissible RPM increase rate. Results are presented for a freely surging model in regular waves with different constraints put on the PID-controller. The described method shows promising results and allows for the studying of several factors relating to selfpropulsion. However, more validation data is needed to judge the accuracy of the mode

Design and Control of a Flight-Style AUV with Hovering Capability

The small flight-style Delphin AUV is designed to evaluate the performance of a long range survey AUV with the additional capability to hover and manoeuvre at slow speed. Delphin’s hull form is based on a scaled version of Autosub6000, and in addition to the main thruster and control surfaces at the rear of the vehicle, Delphin is equipped with four rim driven tunnel thrusters. In order to reduce the development cycle time, Delphin was designed to use commercial-off-the-shelf (COTS) sensors and thrusters interfaced to a standard PC motherboard running the control software within the MS Windows environment. To further simplify the development, the autonomy system uses the State-Flow Toolbox within the Matlab/Simulink environment. While the autonomy software is running, image processing routines are used for obstacle avoidance and target tracking, within the commercial Scorpion Vision software. This runs as a parallel thread and passes results to Matlab via the TCP/IP communication protocol. The COTS based development approach has proved effective. However, a powerful PC is required to effectively run Matlab and Simulink, and, due to the nature of the Windows environment, it is impossible to run the control in hard real-time. The autonomy system will be recoded to run under the Matlab Windows Real-Time Windows Target in the near future. Experimental results are used to demonstrating the performance and current capabilities of the vehicle are presented

Numerical simulation of an ultrasonic vibratory cavitation device

Cavitation erosion prediction is one of the most important tasks in the ship propeller design. While predominantly qualitative methods are used such as paint tests or high speed video image analyses, there have been efforts to quantify such risks especially in the field of computational fluid dynamics (CFD).As an experimental quantitative method to assess erosion risk, the acoustic emission (AE) technique has been employed, for example, by Lloyds Register for more than a decade now to complement their borescopic cavitation observation at the ship scale. Boorsma and Fitzsimmons (2009) reported (see Fig. 1,) its correlation with borescope observed cavitation events appeared very positive and the location of cavitation impingement on the rudder (shown in the left image of Fig. 1) coincided with the estimated location by multiple synchronous measurements of AE at different locations. If it is possible to decipher how the AE connected with the pressure waves emitted from any given cavitation event, predicting the pressure waves we may be able to predict AE and eventually where and what intensity of cavitation events occur on any given propeller or ship structures. The transfer function can be useful for establishing quantitative correlations between CFD, full-scale trial data and with model test data.As the first step in being able to model this process and gain greater understanding in links between acoustic signal and type/location of cavitation, an open source Computational Fluid Dynamics programme openFOAM (version. 3.0.1) has been used to simulate ultrasonic cavitation on a sonotrode and hence to predict cavitation phenomena and pressure impact loads on a test specimen under the ultrasonic horn. The aim of the work is to evaluate the physical realism required and the limitations of current cavitation models

300 years of tropospheric ozone changes using CMIP6 scenarios with a parameterised approach

Tropospheric Ozone (O3) is both an air pollutant and a greenhouse gas. Predicting changes to O3 is therefore important for both air quality and near-term climate forcing. It is computationally expensive to predict changes in tropospheric O3 from every possible future scenario in composition climate models like those used in the 6th Coupled Model Intercomparison Project (CMIP6). Here we apply the different emission pathways used in CMIP6 with a model based on source-receptor relationships for tropospheric O3 to predict historical and future changes in O3 and its radiative forcing over a 300 year period (1750–2050). Changes in regional precursor emissions (nitrogen oxides, carbon monoxide and volatile organic compounds) and global methane abundance are used to quantify the impact on tropospheric O3 globally and across 16 regions, neglecting any impact from changes in climate. We predict large increases in global surface O3 (+8 ppbv) and O3 radiative forcing (+0.3 W m−2) over the industrial period. Nine different Shared Socio-economic Pathways are used to assess future changes in O3. Scenarios involving weak air pollutant controls and climate mitigation are inadequate in limiting the future degradation of surface O3 air quality and enhancement of near-term climate warming over all regions. Middle-of-the-road and strong mitigation scenarios reduce both surface O3 concentrations and O3 radiative forcing by up to 5 ppbv and 0.17 W m−2 globally, providing benefits to future air quality and near-term climate forcing. Sensitivity experiments show that targeting mitigation measures towards reducing global methane abundances could yield additional benefits for both surface O3 air quality and near-term climate forcing. The parameterisation provides a valuable tool for rapidly assessing a large range of future emission pathways that involve differing degrees of air pollutant and climate mitigation. The calculated range of possible responses in tropospheric O3 from these scenarios can be used to inform other modelling studies in CMIP6

Mid-level Illicit Drug Supply in a Small English City: Sellers’ Perspectives and Experiences

This article examines the experiences of eight mid-level drug suppliers operating in a small English city, through use of qualitative interviews. Building on the literature relating to social supply and drift into ‘real dealing’, we explore whether the mid-market for non-‘street’ drugs in this locale follows a continuation of these norms, or whether features that are prominent in recent explorations of UK drug distribution relating to increasingly aggressive marketing, and organised criminal gangs moving into markets in provincial towns, are present in the city’s market. Analysis encompasses suppliers’ experiences of ‘drift’ into commercial supply, pull factors for market involvement, approaches to marketing and customer service, ethical concerns in supply, and finally perceptions of market violence. We observe that the market, while retaining many features of social supply, nonetheless shows evidence of issues relating to emergent norms of altered distribution, notably market violence linked to establishing ‘lines’ in new locales

Click, click, buy: The market for novel synthetic peptide hormones on mainstream e-commerce platforms in the UK

In recent years there has been an increasing focus on the potential public health risks attached to human enhancement drugs (HEDs). While much work has explored the use and supply of HEDs, the market for these compounds is constantly evolving, with new substances being created and sold, and access becoming increasingly simplified through digital platforms. However, one area that has yet to receive scholarly attention is the availability of ‘grey market’ novel synthetic peptide hormones (SPH) through sellers on the mainstream e-commerce platforms Amazon, eBay, and Alibaba. This piece therefore sets out to uncover this burgeoning corner of the broader HEDs trade in the UK market. Findings indicate that SPH are readily accessible over these e-commerce sites, with sellers evading restrictions by claiming that the substances are ‘not for human consumption’ or ‘for research only’, while simultaneously advertising their products as wellbeing supplements. Labelling practices are further identified as a point of concern, since packaging is not necessarily reflective of product quality or true location of origin. Finally, discussion centres on the enhanced legitimacy offered by selling through mainstream sites like Amazon, the capacity for counterfeiting and misrepresentation, and the public health implications of this substantial grey market