In essence, aerodynamics is the interaction of air on an object [7]. In the case of high speed trains, the aerodynamics of the train depends on many factors: “aerodynamic drag, pressure variations inside train, train-induced flow, cross-wind effects, ground effects, pressure waves inside tunnel, impulse waves at the exit of tunnel, noise and vibration”. [8] Ultimately, finding solutions to these problems will result in a faster and smoother train ride, so it becomes imperative to identify the factors that affect each of these so one can manipulate them, if possible, to one's needs. However, having so many factors that affect the aerodynamics of a train, one can truly begin to see how complex this problem is for engineers since every change made to the train or the tracks could cost the companies owning them a huge amount of money for even the smallest of changes.
Specifically, the invention of the high speed train has revolutionized long distance ground transportation since it has provided people with a much faster way to travel, sometimes cutting a seven hour long trip to three hours! However, to reduce such a trip so significantly, the path from city to city (in this place Boston to Washington D.C.) must be as direct as possible [2]. This means that in some cases a tunnel must be built through a mountain to allow for a high speed train to pass through the mountain and get to its destination as quickly as possible.
In terms of high speed trains, there are many different types, each with its advantages and disadvantages. For example, the world renown TGV It has huge advantage in that it can use the same railroad lines as local trains so the cost of making railroad tracks is reduced. However, one of the disadvantages is that using these same train tracks, just the mere fact that the TGV uses the same tracks as local trains means that the TGV limits the size and specifications of local trains because the wake of the TGV causes a wind tunnel that affects the trains behind it. [1] [2]
In terms of what the future has in store, trains haven't even started to reach their limit. From regular train to the high speed train, the speed was increased. The TGV is an obvious example of this transition given that it broke the record for the fasted train, maxing out at 357 mph. The next step is along the lines of the Japanese Maglev; taking friction out of the equation, the Maglev has the ability to greatly reduce the drag and the vibration in the train, thus making the train that much faster. In the foreseeable future, there is a concept that would take the Maglev above and beyond its achievements so far: an “evacuated tube” is a massive vacuum in a tube stretching for miles and miles. Interestingly, if this method is designed and works, it may potentially reap the benefits since the beginning. This occurs because air drag takes such a significant amount of energy out of the system (the system being defined as the train) that minimizing it to a negligible level could immediately save millions upon millions of dollars [8] [9]. On the other hand, there are changes that have been made to the train itself rather than to the environment surrounding it.
The Japanese Hayabusa's nose is angled and sleek so it can eliminate tunnel boom, the sound of a train leaving a tunnel. Tunnel boom is caused by a fast train pressurizing the air in front of it as it goes through a tunnel until it comes out of the tunnel with the pressurized air and makes a very loud sound. Trains in the past had a smaller tunnel boom that occurred right before the train left the tunnel (the sound of a train coming from inside a tunnel); however, now that the trains are that much faster, they catch up to the pressurized air and come out together, creating constructive interference, to make a bigger sound [5]. Furthermore, the French Alstrom developed an upgraded TGV called the AGV. What was interesting about how the French upgraded the TGV is that they took the power system of the TGV and completely transformed it; now it has the capacity of generating higher speeds at a fraction of the original TGV energy consumption. Don't forget that the TGV was designed as an electric train, so to have a power system that can do more with less energy is a huge advancement! [5]
In conclusion, the fact remains that the fast paced society of today has geared people to want to do everything more quickly. Following this train of thought, it makes sense that high speed trains are the future in transportation. Throughout history, people have shown a want, a need for speed.
Works Cited
[1] Fox News. Associated Press. (accessed July 15th, 2012)
[2] Plumer, Brad. The Washington Post. (accessed July 15th, 2012)
[3] European Railway Server. TGVweb. (accessed July 17th, 2012)
[4]
[5] Railway-Technology.com. On Track. (accessed July 15th, 2012)
[6] James, Randy. Time U.S. (accessed July 16th, 2012)
[7] Bopp, Rudolf; Hagenah, Bernd. Gruner.
[8] Raghunathan, Raghu S.; Setoguchi, T. Progress in Aerospace Sciences. Aerodynamics of high-speed railway train
[9] Hoffman, Carl. Popsci: Trans-Atlantic Maglev.
