The Physical Origins of Side Loads in Rocket Nozzles

The side loads that typically occur during the start-up and shut-down transients of rocket nozzles are not yet a fully understood phenomenon. Despite the great practical interest to avoid structural problems to the engine, only few clean data are available, because of the difficulties and the high costs of both experimental and numerical tests. Trying to fill this lack of knowledge, previous numerical studies of transient solutions by the authors are re-examined and compared with numerical steady-state solutions at different ambient conditions. Moreover, the numerical and experimental data published in the meantime are discussed and compared with the present numerical simulations. The analysis allows to establish the main features of these flowfields, and to indicate important differences between steady and transient flow configurations.