Ship Resistance – KCS(KRISO Container Ship)

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Introduction

wave height

This example is a validation problem for the resistance of a ship with a free surface. The resistance of KCS and is compared to the results in the paper below. The interFoam solver is used for the free surface simulation, a steady-state calculation using the Local Time Step (LTS) technique, and the turbulence model is $SST$ $k-omega$.

Measurement of flows around modern commercial ship models, Kim,W J.Kim, Van, S H, Kim, D H, Experiments in Fluids, 2001

Simulation and experiment conditions are as follows

  • speed : 2.196 $m/s$
  • reference area(wetted surface area) : 9.5121 $m^2/s$
  • draft : 0.3418 $m$ (z coordinate at mesh is 0)

Start BaramFlow and load mesh

Run the program and select ‘New Case’ from the launcher. In the launcher, select [Pressure-based] for [Solver Type] and [Volume of Fluid] for [Multiphase Model].

Use the given polyMesh folder. In the top tab, click [File]-[Load Mesh]-[OpenFOAM] in that order and select the polyMesh folder.


launcher

General

Set Time as Steady.

Set Gravity as (0 0 -9.81).


General

Models

For this example, we’ll use $SST$ $k-omega$ model for turbulence.


Turbulence Model

Materials

Since this example is two phase flow, two fluids are required. You can add a fluid by pressing the (+) in the top right corner of the Material Configuration section. Add water-liquid and rename it to water.

Set the properties for each fluid as follows

  • water
    • density : 1000
    • viscosity : 0.001
  • air
    • density : 1.225
    • viscosity : 1.79e-5


Materials

Cell zone Conditions

In Cell Zone Conditions, there is region0 (when multi-region, multiple regions are displayed). Set the fluid of the region. Double-click region0 to open the setting window. Specify air as the primary material and water as the secondary material.

Use 0 for Surface Tension.


Cell Zone Conditions

Boundary Conditions

Set the boundary type and values as shown below.

  • far_inlet
    • type : Velocity Inlet
    • Umag : 2.196
    • turbulentIntensity : 1
    • viscosityRatio : 10
    • alpha.liquid : 0

  • far_outlet
    • type : Open Channel Outlet
    • Umean : 2.196
    • turbulentIntensity : 1
    • viscosityRatio : 10

  • far_top
    • type : Pressure Outlet
    • totalPressure : 0
    • inflow turbulentIntensity : 1
    • inflow viscosityRatio : 10
    • inflow alpha.liquid : 0

  • KCS_dummy_hub, KCS_hub_aft, KCS_hub_cap, KCS_hull, KCS_transom, KCS_deck
    • type : wall


wall

  • centerplane, far_side, far_bottom
    • type : symmetry

Reference Values

Set the Reference Value for the hydrodynamic force coefficient calculation as follows.

  • Area : 4.75605(half of wetted area, because we use symmetry condition)
  • Density : 1000
  • Length : 7.2786
  • Velocity : 2.196


Reference Values

Numerical Conditions

In this example, we’ll change the settings as shown below.

  • Pressure-Velocity Coupling Scheme : SIMPLE
  • Use Momentum Predictor : Off
  • Discretization Schemes : Pressure는 Momentum Weighted Reconstruct, Second Order Upwind for the rest
  • Under-Relaxation Factors : 1 for all
  • Improve Stability : Off
  • Max Iteration per Time Step : 1
  • Number of Correctors : 2
  • Multiphase and Convergence Criteria : default values for all


Numerical Conditions

Monitor

Monitor the force coefficient.

Click [Monitor]-[Add]-[Forces] and set values as follows

  • Lift Direction : (0 0 1)
  • Drag Direction : (-1 0 0)
  • Center of Rotation : (0 0 0)
  • Boundaries : KCS_dummy_hub, KCS_hub_aft, KCS_hub_cap, KCS_hull, KCS_transom, KCS_deck


Monitors

Initialization

Set values as follows

  • velocity : (-2.196 0 0)
  • Pressure : 0
  • Scale of Velocity : 2.196
  • Turbulent Intensity : 1
  • Turbulent Viscosity Ratio : 10
  • Volume Fraction – water : 0


initial conditions

To initialize the water, click [Initialization]-[Advanced]-[Section]-[Create] and select [Section Type] as Hex. Enter the range and values as shown below.

  • Min.point : (-999 -999 -999)
  • Max.point : (999 999 0)
  • Volume Fraction – water : 1

Activate [Override Boundary Value] option to change boundary value also.


Section initialize

Run

Set [Number of Iterations] as 2000.

Selct [Parallel]-[Environment] in menu. Set Number of Cores as you want and select [Local Machine] for [Parallel Type].

Click [Start Calculation] button.


Parallel environment

When the calculation is started, you can see the graphs of Residuals and Force monitor as shown below.

Post-processing

Click the parview button in [External tools] to open the paraview.

Change the [Case Type] to [Decomposed Case].

Select boundaries of ship and change [Coloring] to alpha.water.