Multi-Phase Flow, Advanced: CFD Simulation Training Course — Ep 01
Venturi Flow in a Tube for Air Suction CFD Simulation
- Episode
- 01
- Run Time
- 15m 16s
- Published
- Oct 23, 2024
- Topic
- Multi-Phase Flow
- Course Progress
- 0%
Description
This project performs a two-phase CFD simulation in ANSYS Fluent to study airflow in a Venturi and explicitly track air bubbles as a separate phase within water. As the pipe narrows, continuity increases velocity and, by energy conservation, static pressure drops—the Venturi effect. The 3D geometry is created in SOLIDWORKS and imported into DesignModeler. Meshing is done in ICEM with a structured hexahedral grid (193,932 cells). Because the physics are time-dependent, a transient solver is used.
Venturi Methodology
A VOF multiphase model resolves the air–water interface and bubble entrainment. At the main inlet, a mixed stream enters with a water volume fraction of 0.7 (70%). As this flow accelerates through the throat, pressure falls, drawing additional air through a hole at the Venturi throat (modeled as a pressure inlet on the top boundary). All inlets and outlets are set to 30 bar total pressure.
VOF solves a single set of momentum equations for all phases plus a volume-fraction transport equation for each phase to capture the interface. To sharpen and robustly track the free surface, VOF coupled with a Level-Set method (VOF + Level-Set) is applied, improving interface resolution for immiscible phases with distinct boundaries.
The Venturi has two inlets:
Main inlet: air–water mixture (70% water by volume).
Throat/top inlet: air drawn in by the low pressure at the bottleneck.
As air is entrained, the air volume fraction increases downstream of the throat and discrete bubbles appear within the water phase.
Conclusion
Post-processing yields 2D fields of velocity, pressure, air/water volume fraction, and streamlines across the domain. Results show that acceleration in the throat creates a local vacuum (low pressure), which sucks air into the primary stream; the entrained air mixes with the water, forming a turbulent air–water flow with visible bubbles. Fluent output also provides a time history of the sucked-air flow rate at the air inlet, quantifying entrainment over the transient.