Size Effects on the Transition in Dual-Bell Nozzles

Dual bell nozzle permits two different operating modes which provide higher performance than conventional bell nozzles when applied to rocket engines operating in a varying ambient pressure environment. The most critical aspects of dual bell nozzles are the possible side loads that may occur during the separated flow operations and, especially, during the transition between the two operating modes. The present study addresses the subscale and full-scale nozzles by a numerical analysis of the transition behavior for varying Reynolds number. The results are of particular interest to extend the value of data measured in subscale experiments to full-scale applications.