Building Engineering Programs from the INTERACT Project
Dr Ruth Thomas
The INTERACT Project funded under the TLTP initiative has produced a suite of building engineering simulations. This article outlines three such systems, Waterhammer, Drain Net and Airnet.

Overview
Overview

Introduction

 The goal of the INTERACT, TLTP, project has been to make some of the large body of software used in engineering design and research more widely available for teaching. A major factor in the relatively slow uptake of such applications to date has been due to the poor quality of the user interface. An interface which suits the researcher may be text or file based and unsuited to undergraduate teaching for which a robust graphical user interface is more appropriate. Using existing computational models, the I NTERACT project has produced a number of engineering system simulations which address this problem. This article outlines a suite of applications of interest to building service engineers concerned with unsteady flow in pipe networks together with an over view of their use within multimedia courseware delivered via the World Wide Web.
Overview

Subject Area

 Unsteady flow conditions arise whenever the operating conditions of a fluid network are changed by design, or inadvertently through system failure. The rate of change of the network boundary conditions determines the severity of any transient. It is impor tant that students appreciate the interrelationships that determine transient propagation so that control systems may be introduced into network design. Though transients arise in any fluid network, three particular cases have been looked at within buildi ng engineering. These are traditional water hammer, free surface wave attenuation in open channels and partially filled pipe flows and low amplitude transients in ventilation systems and tunnels. The INTERACT simulation programs allow students to identify the effect of a range of design parameters ranging from wave speed, pipe elasticity and line pressure for water hammer to channel cross- sectional shape in open channel applications.

The suite of building engineering programs are based on models written by Professor John Swaffield, Heriot Watt University. Further information can be found in Pressure Surge in Pipe and Duct Systems (Swaffield and Boldy, May 1993).

Overview

The Water Hammer Effect

 The generation of pressure transient within any fluid carrying network by changes in the boundary conditions of the system is a normal event and occurs in all areas of fluid engineering. Applications range from civil engineering hydroelectric schemes and water distribution networks to installations such as domestic central heating systems, fuel systems and air pressure transients within tunnels. They may all be treated by a basic analysis of the propagation of pressure transients. The objective of such an analysis must be the control of transients rather than their eradication, as transients arise as a normal by-product of changes in any system’s steady state condition. Students should be given the opportunity to understand the factors which affect transi ent generation. The water hammer simulation examines the effects of wave speed, pipe elasticity, line pressure, air content, vapour pressure levels, valve closure times and trapped air volumes upon the transients generated within the system by valve closu res.

The objective of the software simulations is to give students a full understanding of the parameters that affect and control the generation of transients within fluid engineering networks. The understanding of transient propagation is important as it allo ws engineers to define the control and suppression devices which are likely to be effective.

Overview

Drainnet - Simulation of a Building Drainage System

 Surface waves generated by changes in flow to either open channels or partially filled pipes, attenuate as they progress along the length of the conduit. This attenuation becomes important in the design of partially filled pipe flow networks when junction s are included. In the case of drainage and sewer networks, severe problems of solid deposition and maintenance can occur if no allowance is made for the attenuation of waves as they move towards a junction. The oversizing of partially filled pipes is, c ontrary to most engineering applications, a bad thing as it results in an unduly low depth of flow, a low fluid velocity and therefore a higher probability of deposition within the network. This concept is difficult to explain to students without recourse to a combination of simulations and laboratory demonstration.

The objective of the software is to give students an understanding of the parameters that determine wave attenuation in partially filled and open channel flows. Factors include pipe slope and roughness, junctions in a network, whether level invert or top entry, and also the effect of full bore surcharging that may occur if the system is overloaded.

Overview

Airnet - Simulation of Airflow in a Building Drainage System

 The objective of this software is to give students an understanding of the effects of the parameters that determine air pressure transient propagation in ventilation systems and tunnels. These factors include the rate of change of boundary conditions and the presence of air relief valves which modify conditions within the network. In building drainage systems, the interrelationship between the unsteady nature of the water flow in the system and the associated induced air flows is particularly important.
Overview

Integration into Courseware Material

 The use of simulation in teaching traditionally requires a great deal of preparation and instructor involvement. Using the tools developed by the INTERACT project, simulations are integrated with multimedia. Thus, where one might provide a picture to assi st in an explanation, one can instead include a simulation with the relevant parameters. The state and form of the simulation can be controlled by the teacher and serves as a starting point from which the student can conduct further exploration in a guide d manner. INTERACT simulations should be seen as a resource for teachers to utilise in whatever form they require be it lectures, demonstrations, laboratory exercises, tutorials or courseware.
Overview

Availability

 The simulations are freely available to higher education institutions. Details can be found on the INTERACT Web site.

The applications run on any Unix workstation (Hewlett Packard, DEC or Sun), PC platforms running Linux or Macs running A/UX. An Internet connection is required to use the simulation in conjunction with a World Wide Web browser.

Dr Ruth Thomas

Department of CEE
Heriot Watt University
Riccarton
Edinburgh
EH14 4AS
Tel: 0131 449 5111 ex 4187
Fax: 0131 451 328323
Email: rct@eng.cam.ac.uk

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