Introductory FLUENT Training-Tank Flushing

Introduction

-In this workshop, you will model the filling and emptying of a water tank. The transient problem is solved as a multiphase (air/water) simulation using the volume of fluid (VOF) multiphase model.

-An initial water level is set in the tank. The water supply is turned on for the first second of the simulation and then shut off for the rest of the simulation. The water level rises until water flows out the U-tube generating a siphoning effect which effectively empties the tank.

Mesh Import

Start a new 3D FLUENT session

Read or import the mesh file tankflush.msh.gz

Click General in the outline tree.

– Scale the mesh to units of centimeters.

– Set View Length Unit In to cm to have FLUENT display lengths in centimeters.

– Verify the domain extents:
–11.1 < x < 20 cm
–19.8 < y < 27.9 cm
0 < z < 1 cm

– Set the working units
of length to centimeters.

– Check the mesh.

– Display the mesh.

Define Simulation Type

In the General panel, under Solver, set Time to Transient.

Enable Gravity and set Gravitational Acceleration to –9.81 m/s2 in the y direction.

Enable Turbulence Model

1. Activate Models in the outline tree.

– Double-click Viscous-Laminar in the central pane under Models.

– In the Viscous Model panel, select k-epsilon (2 eqn).

– Under k-epsilon model, select Realizable.

– Retain defaults for all other settings.

– Click OK.

VOF Multiphase Model Setup

Enable the VOF multiphase model.

– Activate Models in the outline tree.

– Double-click on Multiphase.

– In the panel that opens, enable Volume of Fluid.

– Set Number of Eulerian Phases to 2.

– Ensure that Scheme is set to Explicit.

– Enable Implicit Body Force

– Click OK.

Define the materials.

– Activate Materials in the outline tree.

– Click Create/Edit…

– In the Materials panel, click FLUENT Database…

– Select water-liquid from the FLUENT Fluid Materials list, click Copy and then click Close.

Phases

Define the phases.

– Activate Phases in the outline tree.

– Double-click phase1-Primary Phase.

– In the Primary Phase panel, change the Name to water.

– Ensure that air is selected under Phase Material.

– Click OK.

– Double-click phase2-Secondary Phase.

– In the Secondary Phase panel, change the Name to air.

– Select water-liquid under Phase Material.

– Click OK.

Multiphase Model Setup

Define phase interactions

– Click the Interaction button.

– In the Phase Interaction panel that opens, activate the Surface Tension
tab.

– Select constant in the pull-down list and enter 0.072 N/m for the Surface Tension Coefficient. Click OK.

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