Effects of activation energy on the instability of oblique detonation surfaces

Oblique detonation waves (ODWs) are simulated using the inviscid Euler equations with one-step irreversible Arrhenius chemistry model to study effects of activation energy E_a on ODW surface instability. Numerical results demonstrate two types of cellular structures, one is featured by a single group of transverse waves traveling upstream, referred to as LRTW (left-running transverse waves), and the other is featured by additional RRTW (right-running transverse waves). To quantify the two destabilized processes, the first and second instability lengths are defined by the lengths of smooth surface and LRTW surface, respectively. It is found out that when E_a increases from 30 to 50, the first length decreases first and then keeps almost constant, while the second length decrease monotonically. By analyzing the flow structure, these variations are attributed into the change of overdriven degree. Generally, high E_a makes the surface unstable, but increasing E_a between 40 and 50, the overdriven degree increases so makes the surface stable. These two effects are opposite and then the first instability length keeps almost constant in this regime.