Close and Far Views of the Oblique Shock

In many cases, the close proximity view provides a continuous turning of the deflection angle, $\delta$ . Yet, the far view shows a sharp transition. The traditional approach to reconcile these two views is by suggesting that the far view shock is a collection of many small weak shocks (see Figure 13.11). At the local view close to the wall, the oblique shock is a weak ``weak oblique'' shock.

Figure: A local and a far view of the oblique shock.

From the far view, the oblique shock is an accumulation of many small (or again weak) ``weak shocks.'' However, these small ``shocks'' are built or accumulate into a large and abrupt change (shock). In this theory, the boundary layer (B.L.) does not enter into the calculation. In reality, the boundary layer increases the zone where a continuous flow exists. The boundary layer reduces the upstream flow velocity and therefore the shock does not exist at close proximity to the wall. In larger distance from the wall, the shock becomes possible.