# Chapter 15

# Shock Intersections or Shock—Shock Interferences

## 15.1. Introduction

Shock–shock interference phenomena are the result of the crossing or intersection of shock waves. This intersection causes the formation of waves whose presence affects the aerodynamic field around a body. If the crossing occurs near the vehicle, these waves can influence the aerothermodynamic loads to which its surface is subjected, or degrade its aerodynamic performance. Shock–shock interferences can occur in any supersonic flow where shock waves are generated either by a deflection produced by a wall (airfoil, control surface, compression ramp of air intake, and cowl) or a back pressure (interblade channel of a transonic cascade, separated nozzle). The shock–shock interferences to be feared are those in hypersonics where the shocks are, first, extremely intense, and second, highly inclined with respect to the upstream velocity (the shock angle *σ* is small). Thus, their intersection occurs near the vehicle and the resulting waves will strike almost inevitably its surface. In section 14.4, we have studied the intersection of two shock waves by considering the case where the configuration is symmetric; the problem is then equivalent to the reflection of a shock on a planar wall. Here, we will be investigating more complex situations where shocks have different intensities.

The first example of shock interference, presented in Figure 15.1a, is a vehicle of the *Space Shuttle* type. In the imagined situation, ...