The idealized wave structure during shock wave experiments is illustrated in Fig. Steady test times of shock tubes are usually terminated by the arrival of rarefaction wave from the driven section or reflected waves from the shock–contact surface interaction, depending on the test condition and geometry of the shock tube.
Shocked95 rec tube driver#
On reaching the end wall of the shock tube, this incident shock wave reflects from the wall and propagates back toward the driver section, stagnating and further compressing and heating the test gas to its initial prereaction temperature and pressure. An incident shock wave quickly forms and travels rapidly ahead of the driver gas into the driven section, increasing the temperature and pressure of the test gas behind it. During a shock wave experiment the driven (low-pressure) section of the shock tube is filled with the test gas mixture, and the driver section is overpressured with gas, often helium or a helium mixture, until the diaphragm bursts. The dissociation of N 2O 4 to NO 2, where the NO 2 is coloured, is conveniently followed by measuring the absorption of mercury radiation at 400 mμ.Ī shock tube in its simplest form is a long tube with closed ends separated into two sections, namely, the driver section and the driven section, usually by a diaphragm. The gas in the low-pressure compartment was ∼1% N 2O 4 in nitrogen at one atmosphere, and using nitrogen at two atmospheres as the driver gas, a 25° rise in temperature was obtained. One of the earliest reactions to be studied by shock-tube experiments using light absorption techniques was the dissociation of dinitrogen tetroxide. At higher temperatures still, ionization can occur, and rates of ionization and recombination can be measured. With stronger shock waves, temperatures are reached at which the diatomic molecule begins to dissociate into radicals, and since this is a relatively slow process, rates can often be measured. The gas is suddenly heated to a new temperature, but it takes many collisions before the molecular rotations and vibrations come to thermal equilibrium with the translational motion. Starting with a weak shock wave, travelling only a little faster than sound, changes in rotational and vibrational energies can be observed.
![shocked95 rec tube shocked95 rec tube](https://img.youtube.com/vi/mfSQW6UOytg/hqdefault.jpg)
If the low-pressure section contains a diatomic gas, other things can happen. With an inert gas, the shock wave produces a heating effect and then thermal ionization. Apparatus used in shock-tube experiments.