There is no doubt that the travelling public wants to travel faster and railway companies are convinced that shaving just a few minutes off a given trip will produce a profitable increase in passenger numbers. Eric Russell looks at the latest developments in high speed trains.

The problem with high speed trains is that high speed means high cost and the total sums mentioned for any high speed rail project are always compared by the detractors with what could be achieved by spending that amount on other forms of transport.
Besides the benefits of reducing the largely wasted time that business people have to endure while travelling, shorter journey times mean less pollution is injected into the atmosphere - provided that the reduced travel time does not mean that excessive amounts of energy are consumed.
The environmental aspect of high speed travel is Canada's concern. Its transport minister hopes a high speed rail (HSR) link in central Canada will become a reality in five or six years using money earmarked to meet commitments to reduce greenhouse gases. The plan is to improve the Quebec City-Montreal-Toronto-Windsor corridor. But the costs of funding such schemes, and the legal issues involved in imposing them on the population and environment, may need the support of radical legislation.
The so-called Via Rail concept in Canada may require legislation that vetoes rail mergers and requires larger airlines to provide services to smaller competitors, for example. But future governments may take a diametrically opposed view and the situation has to be enshrined in law so the project, the associated companies and the public know where they stand on the issue for the relatively long term.
While the anti-HSR lobby says people will never be parted from their cars, the principle remains that powering one engine to transport hundreds of people is better economically and environmentally than powering a car that mostly carries one person. And there is plenty of global activity to support that view. In the USA, bids have been requested to build a high-speed train to run between Orlando and Tampa. One of the four respondents, Bombardier, sees it as an opportunity to raise the profile of its jet train.
In Switzerland, Bombardier Transportation is delivering 10 seven-car electric high speed trains with tilting technology to Swiss Federal Railways. And in Australia, a private group wants to move people and freight across the continent at high speed while opening up the trading and mining country of the inland eastern states. The train would travel from Melbourne to Darwin in 24 hours.

In the UK, Virgin Trains is firmly convinced of the future for tilting trains and it plans to start running them from Edinburgh to London by 2005. Pendolino trains have already made their first test run through the city successfully.
The tilting trains, which are capable of speeds of up to 250kph, would provide new services over the route and this is expected to be approved by the UK's Strategic Rail Authority. Each train costs £11million and is limited to around 200kph until the track infrastructure has been checked so it can tilt on curves, when a top speed around 225kph will be possible.
Virgin Trains is also preparing to achieve another milestone when it introduces Pendolinos on the 640km West Coast route between London and Glasgow. In the meantime, the company is bringing more tilting trains into use on other lines.

Pendolino principle

The Pendolino concept is based on the way a motorcyclist combats centrifugal forces by leaning into a bend. For trains, the idea originated at the end of the 1960s and was tested in Italy, a country whose mountainous geography means roads and railway tracks often have to follow tortuous routes.
The first prototype of the train, the Y0160 built in 1967, quickly earned the nickname Pendolino, and that has stuck ever since. The Italian State Railways started running the Fiat Ferroviaria ETR450 version of the tilting train in 1988 and soon had 15 in service.
Pendolino's top, straight-line speed is 250kph. While this is not as high as the 300kph or so reached by the French TGV and the Italian ETR500, for which Fiat Ferroviaria designed and built the carriages, it is still far faster than traditional trains. The Pendolino also has the advantage of being able to run on standard tracks.
Journey times have been dramatically reduced by the Pendolino because of its high straight-line speed and faster travel around bends, and while conventional high speed trains may be viable on some busy routes, the level of investment required in track makes them impractical for most.
Today's Pendolino makes use of a load bearing body made of aluminium based alloys from the aeronautical industry which minimises the train's weight. Reducing the weight even further will also mean less wear and tear on the rails. A Superpendolino is on the drawing board at the moment, promising speeds of 300kph on high speed sections of track.

Aerodynamics

High speed trains bring unique design problems. One concerns the unsteady air flow behind such a train. The solution can be reached using computational fluid dynamics software (CFD) which models flows of liquids and gases.
Fluent is a leader in this field and a study by Dr Christoph Heine and Gerd Matschke of Deutsche Bahn AG, Munich, Germany, says the problem partially arises because modern trains are lighter than those of past years.
This is due in part to the replacement of a power car at the rear of the train with an unpowered driving trailer. This change has meant lower axle loads, reduced wear on ballast, and increased passenger capacity, since the end car can now be filled with seats.
For a light-bodied driving trailer, the unsteady aerodynamic loads may become significant for the running behaviour, and this effect has become a concern for a number of railway operators in Europe.
In the EU-funded BriteEuram research project RAPIDE (Railway Aerodynamics of Passing and Interaction with Dynamic Effects), the partners have joined forces to investigate the boundary layer development along a modern high-speed train and the wake flow characteristics behind the end car using CFD.
The CFD investigation was divided into three parts, corresponding to three sections of a moving train: the front car, the midcars, and the trailing car. The boundary layer grows in thickness from the front to the trailing car, and when this thick boundary layer separates behind the trailing car, the points of separation on the train surface can periodically shift. This gives rise to aerodynamic oscillations about the longitudinal axis, which can cause discomfort to the passengers riding in the trailing car.
The European organisations MIRA and SNCF performed boundary layer development calculations on the front and midcar sections. Their results were then used by Deutsche Bahn to simulate the unsteady flow around and behind the German ICE2 end car.
The end section modelled was 40m in length. A volumetric mesh of tetrahedral and prismatic cells was used to divide the model into cells. The profiles along the sides and on top of the train generated by the other partners in the project were used as inlet boundary conditions. The data from these conditions was then transferred across the cells, with a calculation in each cell to show the changing pattern across the model. The ground under the train was given a uniform speed equal to that of the moving train.
A steady-state simulation using a standard turbulence model was initially performed on multiple processors. The symmetric solution showed low pressure on the shoulder areas of the end car and a high pressure region on the back face that results from the onset of separation. A transient calculation was then initiated using the steady solution as a starting point. Using time steps of up to 0.01 second, unsteady flow developed with a period of oscillation on the order of 1Hz. This frequency was found to be in good agreement with measurements reported by a Japanese railway company.

Further runs were done using smaller time steps and a higher order turbulence model, which yielded identical oscillations in the flow. Based on the CFD results, the aerodynamic coefficients were calculated. These forces and moments served as an input for Multi Body Systems calculations performed by Bombardier Transportation, and the running comfort was evaluated.
The oscillations were found to be far too weak to cause vehicle movements, so they would not cause any passenger discomfort. But the exercise showed up the potential problems that arise as running speeds increase.
One factor that will encourage the introduction of high speed trains is the wealth of technical developments that has been created over the past two decades. Today, companies are focusing on how to implement these inventions and developments instead of researching ever newer ideas and this will show in improved train designs - and speeds.