<p>The interaction and behavior of detonation waves propagating in a linear detonation combustor (LDC) were studied to identify the coupled thermoacoustic-chemical phenomenon responsible for self-generated and self-sustained detonation waves. The LDC was operated with natural gas and gaseous oxygen over a wide range of equivalence ratios and optically observed with OH*-chemiluminescence, schlieren, and broadband imaging in addition to high-frequency pressure transducers and photomultiplier tubes. Counter-propagating, self-sustained detonation waves were observed in the semi-bounded combustor to accelerate and amplify consistently from the closed-boundary to the open-boundary. The incident waves then reflect off of the open-boundary and transition into weaker waves that propagate acoustically relative to the burned products before being reflected by the closed-boundary and accelerating to dominancy once again. The combustor was then modified to have symmetric boundary conditions with both ends closed. For closed cases, the detonation waves experienced similar acceleration and amplification processes. The incident waves accelerate until they are reflected by a closed boundary into a flow field for which the fuel-injectors have yet to recover. For this reason, the reflected waves propagate through burned products until they encounter fresh reactants and accelerate again. The closed boundary conditions also caused the direction of dominance to periodically alternate. This study indicates that the local mixing field between open and closed boundary conditions affects the strength and speed of the reflected wave and demonstrates the impact of combustor geometry on coupled thermoacoustic-chemical phenomenon in RDEs.</p>