Numerical study of the effect of geometric parameters on jet tab based TVC system

Jet tabs are a type of thrust vector control mechanism which operates by inserting a physical obstacle i.e. tab, into the nozzle exhaust stream to induce a strong normal shock just upstream of the tab and an oblique shock further upstream at the point of separation from the wall. The adverse pressure gradient along the nozzle wall which accompanies this complex shock-shock boundary layer interaction provides the required side force. In this study, a CFD study is carried out on commercial code Fluent to study the flow structures as well as the geometric parameters that may affect the performance of jet tab such as; area ratio, tab-nozzle gap and tab-nozzle angle. The study validates the experimental results that show that the blockage area ratio directly affects the force while the gap b/w nozzle exit plane and jet tab adversely affects the force value. It was found that the angle P between nozzle divergent section and jet tab face adversely affects the force at small gap but as the gap is increased the dependence of force on P angle reduces.