The behaviour of shock waves propagating in a gas has been studied for more than a century, experimentally, theoretically and numerically. It was established, in particular, that the thickness of a shock wave (the layer, in which parameters of the medium vary rapidly in space) is of the order of several mean free paths of the gas molecules, provided that the shock is of moderate intensity. Distributions of the parameters of the medium inside the shock resemble the hyperbolic tangent function. The necessary condition for the above to be fulfilled is that the gas is dilute, which means that its molecules interact (collide) with only one neighbour at a time, and between collisions they move with constant speed along straight lines (concept of a mean free path – the average distance travelled this way). Duration of a single collision is negligibly short as compared to the time of free flight (mean free time). In dilute gas the mean free path of the molecules is much larger than the diameter of the molecule and larger than their average separation distance (Figure 1 – left).
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- Structure of Shock Waves in Dense Media
Z. A. Walenta
- Springer Berlin Heidelberg
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