Alan Vardy has led many application-based research projects designed to increase general understanding. Often, these have included subjecting theoretical predictions to the rigour of comparison with detailed physical measurements. The resulting publications have highlighted both strengths and limitations of the theoretical methods. It is hoped that the willingness to expose deficiencies will increase faith in more positive achievements.
The application-based research has included:
• pressure waves in rail tunnels
• sonic booms from tunnel portals
• prediction-based, automatic control of road tunnel ventilation systems
• full-scale measurements in tunnels
• model scale measurements in tunnels
• promotion of professional development
Trains travelling through tunnels generate pressure waves that subsequently propagate back and forth along the tunnels. They are a potential source of aural discomfort for passengers on trains. Vardy’s research on this topic has tended to focus more on alleviating the effects than on analysing them in ever-increasing detail. The most direct remedial measures involve modifications to train design, but much work has also been devoted to optimising tunnel design.
In the absence of sufficient causes of dissipation, compression waves tend to steepen as they propagate along a tunnel. In slab-track tunnels, they can steepen so much that significant pressure disturbances radiate into the surrounding environment. In extreme cases, remarkable loud sonic booms can be caused. Less dramatic, but more common, low frequency radiation can cause the vibration of doors and windows when buildings are close to a tunnel portal.
The development of efficient automatic control systems for tunnels has been a high priority in Japan for many years and it is becoming equally important in many other countries. Vardy recognised the huge potential of predictive control systems used in other industries and developed a model-based predictive control system for road tunnel ventilation systems that is now installed in several tunnels including the longest one in Japan.
Vardy has participated in full-scale measurements of pressures and airflows in many tunnels. This is always a collaborative venture, requiring the support of the infrastructure operator and, usually, of many other parties. It is an essential – and most enjoyable - part of application-based research and it involves many practical and organisational challenges not experienced in theoretical studies or even in laboratory experiments.
Although full-scale measurements are often regarded as the ultimate test of a theoretical method, they have important limitations in the control of the conditions to be measured and, at least as important, they tend to be very expensive. Model scale measurements can also suffer from these disadvantages, but usually to a much smaller extent. They also enable testing of phenomena that do not yet exist at full-scale – e.g. ultra-high-speed trains.
In addition to undertaking research, academics have a passion for teaching. Often this is done through full-time or part-time courses or through one-day seminars, etc, but these methods are effective only for people taking responsibility for their own professional development. Vardy devotes a substantial proportion of his time to exposing practising engineers to teaching experiences when they are not expecting it. This is achieved, for example, during routine consultancy interaction and through conference papers designed specifically to highlight strengths and limitations of widely used methodologies. A splendid spin-off benefit of this policy is that DTR is also exposed to unexpected learning experiences!
