Two-phase annular flow in vertical pipes is one of the most common and important flow regimes in fluid mechanics, particularly in the field of building drainage systems where discharges to the vertical pipe are random and the flow is unsteady. With the development of experimental techniques and analytical methods, the understanding of the fundamental mechanism of the annular two-phase flow has been significantly advanced, such as liquid film development, evolution of the disturbance wave, and droplet entrainment mechanism. Despite the hundreds of papers published so far, the mechanism of annular flow remains incompletely understood. Therefore, this paper summarizes the research on two-phase annular flow in vertical pipes mainly in the last two decades. The review is mainly divided into two parts, i.e., the investigation methodologies and the advancement of knowledge. Different experimental techniques and numerical simulations are compared to highlight their advantages and challenges. Advanced underpinning physics of the mechanism is summarized in several groups including the wavy liquid film, droplet behaviour, entrainment and void fraction. Challenges and recommendations are summarized based on the literature cited in this review.

National design guides provide essential guidance for the design of building drainage systems, which primarily ensure the basic objectives of preventing odor ingress and cross-transmission of disease through water-trap seal retention. Current building drainage system design guides only extend to buildings of 30 floors, while modern tall buildings frequently extend to over 100 floors, exceeding the predictive capability of current design guides in terms of operating system conditions. However, the same design guides are being used for tall buildings as would be used for low-rise buildings. A complicating factor is the historic roots of current design guides and standards (including the interpretation of the governing fluid mechanics principles and margins of safety), causing many design differences to exist for the same conditions internationally, such as minimum trap seal retention requirements, stack-to-vent cross-vent spacing, and even stack diameter. The design guides also differ in the size and scale of the systems they cover, and most make no allowance for the specific building drainage system requirements of tall buildings. This paper assesses the limitations of applying current building drainage system design guides when applied to the case of tall buildings. Primarily, the assessments used in this research are based on codes from Europe, the USA and Australia/New Zealand as representative of the most common approaches and from which many other codes and standards are derived. The numerical simulation model, AIRNET, was used as the analysis tool. Our findings confirm that current design guides, which have been out of date for a number of decades, are now in urgent need of updating as code-compliant systems have been shown to be susceptible to water-trap seal depletion, a risk to cross-transmission of disease, which is a major public health concern, particularly in view of the current COVID-19 pandemic.

In marketing, as in many other academic disciplines, new scholars are often taught a simple formula for the achievement of professional success: the single-minded pursuit of “A”-level journal publications. Although the goal of producing high-quality research that is ultimately published in top level journals is certainly worthwhile, the attainment of true prominence or “eminence” in the discipline may draw on a more complex formula. Anecdotal evidence suggests that the most prolific scholars may not always be the most eminent. Taking a personal brand-building perspective, this study examines a wide range of factors that may influence the attainment of scholarly eminence in the marketing discipline. Using a sample of 297 marketing academicians, this study finds that although a raw volume of publications influences eminence, publishing top-tier publications is even more significant. Perhaps most interestingly, this work highlights several different professional paths that can lead to scholarly eminence, including a tradeoff between publishing sole-authored pieces and “A”-level volume, and the eminence-enhancing effects of various professional activities. These findings suggest that a single-minded model of the path to scholarly eminence is supported but not necessarily complete.

There is an established body of research on water use by the domestic and agricultural sectors, but very little peer-reviewed literature have been published on industrial water use. This has been attributed to the commercially competitive and complex nature of the industrial sector, and the attendant difficulties in collecting requisite data for any analysis (Reynaud, 2003). Consequent upon this, there is a growing concern over the sustainability of water-related industrial practices and processes. To this end, focusing on key water-intensive industrial subsectors, the food and drink sector which according to DEFRA (2007) and the Environment Agency 2013 has the highest rate of water use in the industrial sector, was chosen for this performance assessment, the aim being to clearly understand how various food and drink firms use water, relative to other “comparable” firms, and against industry standards or benchmarks. For the analyses, data on water use were collected from 53 dairy companies, for a 5-year (minimum) period, and covering three water-intensive dairy products—liquid milk, butter and cheese. Thus, data were collected from 27 liquid milk-producing companies, 13 butter- and 13 cheese-processing companies. Based on the findings, of the 53 benchmarked companies, 17 companies’ water use performance were ranked “excellent”; 26 companies, “average”; while the remaining 10 companies’ performance were “poor”. These results emphasise the need for creation of more comprehensive water management schemes and conservation clubs within the food and drink sector. From this study, benchmarking, a performance assessment and improvement process, has been established as a veritable strategy for driving behavioural change in water use by industry, and enhancing the sustainability credential of the UK industrial sector, in terms of fresh water use.

A model is presented which allows steady-state pressure profiles in high-rise wastewater drainage networks to be related to intake air flowrates and discharge water flowrates. This model is developed using data taken from academic literature, and is based on experimental observations which suggest that a vertical annular downflow develops over distance such that the pressure gradient in the wet stack may be expressed as the sum of junction components and developed flow components. The model is used to analyse a simplified ‘medium rise’ primary vented system of height 40 m, hosting two inflow junctions, crossvents and Air Admittance Valves (AAVs). The model illustrates how the air supply configuration affects the airflow rates within the stack and the vents, and how the configuration affects the steady-state hydraulic pressure profile. The model offers the possibility of an alternative approach to the design of high-rise wastewater drainage networks, compared to existing design codes. These codes generally do not explain the role that the air admitted into the network has upon its performance.

Blockages in sewers and drains often result in overflows and flooding that cause significant environmental pollution and public health risks, particularly in hospitals, where the consequences can be catastrophic. Due to their low “visibility”, sewers and drains are inherently difficult to monitor and maintain, resulting in a reactive management approach whereby maintenance or repair is carried out only after a system failure has occurred. This paper investigates the feasibility of applying the reflected wave technique, a unique sonar-like monitoring approach capable of identifying changes in the geometry of closed-pipe conduits, as a means of proactive system monitoring. The technique uses a 10 Hz sinusoidal air pressure wave which is transmitted into the drainpipe. When the pressure wave encounters a system boundary, a reflection is generated which alters the measured test pressure response. Analysis of the reflections generated by a changed system boundary, such as the formation of a blockage, can provide information related to the location of that boundary within the system. An experimental setup was developed to simulate a horizontal drain using standard pipework of 100 mm diameter and 70 m length. The technique was able to detect applied blockages with cross-sectional coverage of 30% and 75%, and lengths ranging from 30 mm to 3000 mm. Accuracy was improved when the pressure sensor was positioned closer to the blockage. When the sensor was 3.4 m from the blockage, location estimates were very accurate (−2% to 3% error). At a 14 m distance from the blockage, the error increased to between 4% and 33%. The accuracy of blockage detection and location improved with increasing blockage cross-sectional area and length. Overall, the reflected wave technique could provide a potentially continuous monitoring solution for blockage detection in sewers and drains.