Numerical Study on the Influence of Inflow Conditions on the Performance of Vortex Generator in a Serpentine Air Intake Duct

Abstract

Serpentine air intake system is an essential requirement in modern combat aircraft. Flow control techniques are used to achieve the desired performance of flow uniformity and pressure recovery. Mechanical vane type vortex generator designed in the previous work is considered as a flow control technique. The performance of vortex generator at various off-design conditions of different subsonic throat Mach numbers and three different altitudes are of interest to this present study. Numerical simulations were performed for throat Mach numbers from 0.45 to 0.7 in the increment of 0.05, with and without vortex generator at sea level static inflow condition. Flow non-uniformity and pressure losses were found to increase with increase in Mach number. However, flow uniformity is better with vortex generators for all Mach numbers with slight reduction in total pressure recovery at sea level condition. In order to check the effect of increasing altitude, duct with VG was simulated for 6 km and 11 km altitudes. All the simulations are conducted with reducing the inlet total pressure from sea level to represent the altitude and varying the exit static pressure to arrive at the desired throat Mach number. In general, Reynolds number decreases with increasing altitudes and promotes the possibility of flow separation. While reduced pressure recovery was seen, DC-60 was lower at 6 km altitude for all the Mach numbers. Higher value of DC-60 at sea level condition is primarily due to the dynamic pressure at AIP. Generally, a threshold value of DC-60 is to be given as a design requirement. Present design of vortex generator has reduced DC-60 value from 29.7 to 20.7 at 0.65 Mach number and sea level condition with a maximum of 25 from all the other conditions, thereby proving its benefits.