Spray Injection

Description

This project simulates a water spray issuing from a small circular inlet into a larger cubic enclosure, using ANSYS Fluent's Discrete Phase Model (DPM) as an introductory case for particle-tracking simulations. Unlike multiphase models that treat a second phase as continuous, DPM follows the Lagrangian approach, tracking individual droplets one by one through the surrounding air so their trajectory, velocity, and dispersion can be examined directly rather than inferred from a bulk phase-fraction field. The geometry is a rectangular cube with a circular inlet on the top wall, built in Design Modeler and meshed in ANSYS Meshing with an unstructured grid of 25,464 cells.

Methodology

Because the droplets move as discrete entities through a continuous air medium, the case couples a Lagrangian DPM formulation to the continuous Eulerian air flow, run transient so the spray's development in time can be captured. The core setup step is the injection definition: water is introduced as a surface injection from the inlet, with droplets treated as inert particles, meaning their size, position, and velocity at entry are specified directly and Fluent integrates each individual trajectory through the resolved flow field, in contrast to a multiphase model where phase behavior would instead be governed by shared momentum and volume-fraction equations.

Analysis

The results include velocity and mass-concentration contours of the water particles at the final time step, along with 3D particle tracks colored by speed and droplet diameter. These tracks confirm the injection is behaving as intended, with droplets dispersing discretely from the top inlet and spreading through the enclosure, the exact behavior relevant to tasks like sizing spray nozzles or predicting coverage patterns in a real application.