Wake closure conditions in plug nozzle flowfields
The aerospike, of plug, nozzle is being proposed for future space launch vehicle applications. The design of the nozzle involves complex wake structures that directly affect engine performance. In particular, the closed or open wake condition of the flow determines the dependence of the base pressure on the ambient environment, and therefore affects overall thrust. An experimental, numerical, and analytical investigation characterized the transition of the wake between closed and numerical, and analytical investigation characterized the transition of the wake between closed and open conditions in order to determine the physical mechanism leading to wake closure. A common feature between different modes of wake closure was the presence of a shock structure that forced changes to the wake critical point. Wake closure is defined as the limiting condition at which external pressure gradients change the properties and location of the critical point. Changes to critical point directly influence the nozzle base pressure due to the critical point's uniqueness property. Supersonic wake methods can determine wake closure trends for mission optimization. Increased wake closure nozzle pressure ratios and closed wake pressures can be achieved through design Mach Number, nozzle size, length and ramp shape.