This paper describes ongoing research efforts in the scramjet community on
cavity flame holders, a concept for flame holding and stabilization in supe
rsonic combustors. During the last few years, cavities have gained the atte
ntion of the scramjet community as a promising flame-holding device, owing
to results obtained in Right tests and to feasibility demonstrations in lab
oratory-scale supersonic combustors, However, comprehensive studies are nee
ded to determine the optimal configuration that will yield the most effecti
ve flame-holding capability with minimum losses. The flowfield characterist
ics of cavities and research efforts related to cavities employed in low- a
nd high-speed flows are summarized. Open questions impacting the effectiven
ess of the cavities as flame holders in supersonic combustors are discussed
.