Description

This project simulates gravity-driven tank discharge in ANSYS Fluent using a two-phase VOF model. The domain comprises three interconnected tanks linked by pipes.

Geometry & Mesh

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  2D geometry (DesignModeler):

  
  
  
  
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    Tank 1: 229.4 × 157.7 mm rectangle

    
    
  
  
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    Tank 2: octagon, side length 51.3 mm

    
    
  
  
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    Tank 3: 229.4 × 100 mm rectangle

    
    
  
  
  
  


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  Mesh (ANSYS Meshing): unstructured, 15,310 elements.

  
  

CFD Setup

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  Flow: incompressible, transient

  
  


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  Gravity: −9.81 m/s² on the Y axis

  
  

Models & Properties

Multiphase (VOF)

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  Homogeneous, implicit formulation with implicit body force

  
  


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  2 Eulerian phases: primary air, secondary water

  
  


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  Interface: Sharp with Interfacial Anti-Diffusion

  
  

Viscous model

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  Laminar

  
  

Materials

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  Air: ρ = 1.225 kg/m³, μ = 1.7894×10⁻⁵ kg/(m·s)

  
  


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  Water (liquid): ρ = 998.2 kg/m³, μ = 0.001003 kg/(m·s)

  
  

Numerics

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  Pressure–velocity coupling: SIMPLE

  
  


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  Discretization: Pressure PRESTO!; Momentum Second-order upwind; Volume fraction Compressive

  
  

Cell Registers (monitor region)

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  X: 0.08 → 0.379 m

  
  


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  Y: 0.2264246 → 0.33 m

  
  

Initialization & Run

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  Initialization: Standard

  
  


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  Patch: set water volume fraction = 1 in Region_0 (Phase2)

  
  


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  Time advancement: Adaptive

  
  
  
  
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    Initial Δt = 1×10⁻⁵ s

    
    
  
  
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    Δt min = 1×10⁻⁵ s, Δt max = 1×10⁻³ s

    
    
  
  
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    (Run targets 10,000 time steps)

    
    
  
  
  
  

Results

Post-processing includes contours of volume fraction, pressure, velocity, and streamlines. Water drains from the primary tank into the second, which cannot hold the entire volume; subsequently, flow proceeds into the third tank via the connecting pipe. Dedicated vents enable air circulation between tanks—visible in the velocity and streamline plots—facilitating continuous discharge and level equalization.