Multi-Phase Flow: Pouring Water out of a Bottle

Pouring Water Out of a Bottle — ANSYS Fluent CFD Simulation

This project simulates water pouring out of a bottle using ANSYS Fluent. The two-phase flow field is modeled using the Eulerian multiphase approach, which allows multiple distinct but interacting phases—liquid, gas, or solid, in nearly any combination—to be solved simultaneously.

Geometry and Mesh

The 2-D geometry was created in SpaceClaim and meshed in ANSYS Meshing using an unstructured mesh across the entire domain, totaling 150,642 elements.

Setup and Assumptions

Given the incompressible nature of the flow, a pressure-based solver is used, with the simulation run as transient and gravity set to -9.81 m/s² along the Y-axis.

The multiphase model is set to Eulerian with the Multi-Fluid VOF formulation, involving two phases—air as the primary phase and water as the secondary phase—using sharp interface modeling and explicit formulation. Turbulence is handled with the standard k-epsilon model and standard wall functions.

Air is defined with a density of 1.225 kg/m³ and viscosity of 1.7894×10⁻⁵ kg/m·s, while water-liquid has a density of 998.2 kg/m³ and viscosity of 0.001003 kg/m·s. A pressure outlet boundary condition is applied at the outlet.

The SIMPLE scheme is used for pressure-velocity coupling, with PRESTO! for pressure and second-order upwind discretization for momentum, turbulent kinetic energy, and turbulent dissipation rate. The volume fraction is solved using a compressive scheme. The domain is initialized using the hybrid method, with the water region patched to a volume fraction of 1.

The simulation runs with a time step size of 0.0025 s, a maximum of 20 iterations per time step, and a total of 3,708 time steps.

Results

Upon completion, contours of water velocity, pressure, water volume fraction, and eddy viscosity are extracted. The results show that, under the influence of gravity, water flows out of the bottle and discharges into an adjacent empty container, gradually filling it.