Rocket Engine Nozzle

Description

This simulation examines flow through a rocket engine nozzle in ANSYS Fluent, a compressible flow problem central to propulsion design. A rocket nozzle works by converting the internal energy of hot propellant gases into directed kinetic energy, producing a high-velocity exhaust jet; the gases enter subsonic, are forced to accelerate as the passage narrows toward the throat, and reach sonic velocity exactly at that minimum cross-section. Beyond the throat, the diverging section allows the gas to keep expanding and accelerating, pushing the flow to supersonic exit speeds. The geometry is built as a 2D convergent-divergent nozzle in Design Modeler, capturing the interior flow path through the throat and diverging sections, and meshed in ANSYS Meshing with an unstructured grid of 69,342 cells.

Methodology

Because the flow is compressible and spans subsonic-to-supersonic regimes across the nozzle, the density-based solver is used, with gas density computed from the ideal gas law rather than treated as constant. The nozzle inlet is set to a gauge pressure of 2,268,000 Pa, and the outlet to 39,365 Pa, a large pressure ratio that drives the expansion and acceleration through the throat.

Analysis

The solution produces 2D contours of temperature, pressure, velocity, density, and enthalpy, along with streamlines through the nozzle. These fields confirm the expected compressible-flow behavior: the gas accelerates sharply as it passes through the throat, and this acceleration is accompanied by a corresponding pressure drop as the cross-sectional area shrinks, consistent with the physics of convergent-divergent nozzle flow.