Tall buildings introduce a range of unique issues when detailing the design and specification of the waste water drainage and vent systems. Research has shown a clear link between the height of a building and the dynamic response of the connected waste pipes. Furthermore, the consequences of, for example, a reduction in w.c flush volume or the use of a range of detergents in such systems are far reaching. In today’s climate where sustainability and water conservation are key, it is vital that designers have access to the tools required to be able to specify an optimal drainage system that ensures waste is safely and quickly removed from the habitable space with minimum water consumption whilst ensuring trap seal retention through the provision of well designed ventilation incurring minimum material, space and maintenance costs. A coherent programme of research undertaken by the Drainage Research Group at Heriot-Watt University, Scotland has led to the development of a suite of tools, designed to aid building drainage system designers, based upon the simulation and mathematical modelling of unsteady fluid flows. These unique models have been developed using extensive laboratory and site data, and have shown that it is possible to predict the performance of multi-storey building drainage systems under a range of design formats and varying operational criteria. The group was established in 1988 and has maintained an international reputation for work in this area that has had considerable implications for water conservation, building drainage, building drainage standards, system component design and performance testing. This paper presents a brief overview of the group’s work to date and reports recent research investigations that have clear implications for the future design and specification of drainage systems for high-rise buildings.

The transient analysis of the fluid services associ ated with building operation is necessary due to the growing complexity of the built environment, an d the need to both simplify system design and accommodate climate change. The prevention of od ur ingress and cross contamination between habitable spaces via the drainage network i s essential. It is also vital to ensure that siphonic roof drainage systems are dynamically bala nced and that pressures do not drop to dangerously low levels. In these cases, transient a nalysis can be employed to improve system design and to determine the causes of operational p rob ems and system failures.

Pressure transients are inevitable in any fluid transportation system. Changes in fluid flow conditions can generate undesired negative and positive pressure transients. These propagate through a system until they are brought under control by some form of pressure equalization device, are reduced by frictional damping or released by either, a compromising of the integrity of the system or encountering an open termination. Building drainage and vent systems (DVS) are no exception. Negative pressure transients, generated by increases in appliance water flow, and positive pressure transients caused by surcharges at the base of the stack or at offsets, both compromise the integrity of water trap seals which can lead to foul air entering a habitable space. This paper describes a radical new approach to the alleviation of positive air pressure transients in DVS. A new positive air pressure attenuator device, the PAPA, designed specifically for use in building drainage systems is shown to be effective at protecting water trap seals against unwanted positive transients.

The finite difference based method of characteristics model for unsteady partially filled pipe flow was extended to include the model for the stack to horizontal drain entry boundary condition.The conditions at drain entry are defined in terms of the energy of the terminal annular flow velocity in the stack, together with an appropriate loss coefficient function at the entry.The hydraulic solutions link the branch drains, fittings, vertical soil stack, and building drain.The analysis permits any combination of drainage load patterns from simultaneous, overlapping, or sequence of discharge events.Preliminary simulations utilizing this model indicate that the modeling technique extends the existing horizontal network analysis program for determination of multistory building drainage systems.The sizing procedure provides the hydraulic capacity of drains for specified pipe sizes, pipe pitch, and wall roughness factors.

Fairly well-defined and generally accepted regions of the (first formant frequency)—(second formant frequency) plane (referred to as the F1F2 plane) can be associated with each speech vowel sound. Delineation of the boundaries of these regions may be based on analysis of spoken vowels or on perception of synthesized vowels; in either case, the data are derived from the study of isolated vowels or monosyllables, and the resulting two sets of regions prove to be roughly the same. An alternative study, described in the paper, can be made, however, based instead on the vowel sounds occurring in “connected” or “conversational” speech. In this case the density of distribution of points within the F1F2 plane shows that there is little or no clustering of stationary points within the original (“monosyllable”) vowel regions and certainly permits neither identification of old, nor definition of new, regions. A set of tracks can be constructed, however, to correspond to the almost continuously moving F1F2 points and from these can be derived, by suitable processing, a new set of regions of simple shape, one region for each vowel sound as before. The differences between the set of regions for “monosyllable” vowels, i.e., the generally accepted set, and the set for “conversational” vowels, which may be reasonably regarded as the set in normal use, are striking. Two differences are (a) the set of vowel regions is now clustered very much more closely together than before and (b) for a given speaker the positions of “monosyllable” vowels do not even lie within the regions of the corresponding “conversational” vowels.