Supersonic Jet Ramped Intake

Supersonic Jet Ramped Intake Simulation, ANSYS Fluent CFD Training

Description

This project simulates a supersonic jet ramped intake using ANSYS Fluent. With the development of jet engines and the resulting ability of aircraft to travel at supersonic speeds, engineers faced the challenge of designing intakes capable of supplying the airflow required by the engine across a wide operating envelope, while delivering high-pressure recovery and low flow distortion.

These design demands grew significantly more complex as aircraft speeds increased toward Mach 3.0 and Mach 3.2 — the design points for the XB-70 and SR-71, respectively. The intake forms part of either the fuselage or the engine nacelle.

Ramped, or angled, intakes are specifically designed so that their angled surfaces generate shock waves, allowing uniform, undisturbed flow to enter the channel and reach the engine. The cross-sectional geometry changes progressively along the channel to shape the flow accordingly.

This project models a ramped intake based on the geometry of the F-15 intake, placed within a supersonic flow at Mach 1.4, examining the resulting changes in velocity, pressure, and velocity profile along the channel.

The 3D geometry was designed in Design Modeler, with the domain including a velocity inlet, pressure outlet, wall boundaries for the intake surface, and far-field boundaries along the sides. The model was meshed in ANSYS Meshing using an unstructured grid totaling 1,278,343 elements.

Methodology

The simulation used a density-based solver, with turbulence modeled using the k-omega SST model. The intake was simulated at its operational design point, with an inflow velocity of Mach 1.4.

Conclusion

The Mach number contour clearly reveals the formation of oblique shock waves and expansion fans both at the intake entrance and within the intake channel. These shock waves decelerate the flow to subsonic speeds near the inlet and promote flow uniformity, while the channel itself behaves similarly to a converging-diverging nozzle — an effect also reflected in the pressure and temperature contour results.

Velocity contours across different regions of the intake further illustrate how the channel's wall geometry progressively uniformizes the flow speed along its length. The pressure contour along the intake shows a characteristic pressure drop at the opening, followed by gradual recovery through the channel — a behavior that keeps the engine operating under ideal conditions and helps prevent compressor stall.