LS-DYNA TUTORIAL 18: Sphere Drop on Water with ALE method

Introduction

This tutorial guides you through modeling fluid-structure interactions using the Arbitrary Lagrangian-Eulerian (ALE) method in LS-DYNA. Inspired by the work of Bisagni and Pigazzini (2017), we will simulate a sphere dropping on water, focusing on creating a quarter model, modifying sphere density, applying boundary conditions, and more. This step-by-step guide will help you set up and run your simulation effectively.

Step 1: Create Fluid and Domain Parts with ALE Formulation

• Open your LS-DYNA software and start a new project.
• Define the fluid part:
  • Use the ALE formulation to represent water.
  • Set the Material Type for water using MAT_NULL and specify the equation of state (EOS) for fluid behavior.
• Define the domain:
  • Create a vacuum part to represent the domain for fluid interactions.

Step 2: Modify Sphere Density

• Create a solid sphere model for the simulation.
• To achieve the desired mass:
  • Adjust the sphere's density parameters.
  • Ensure the density is set correctly to match the intended physical properties of the sphere.
  • Note: The viscosity (MU) for water should be set to 1e-9.

Step 3: Create Quarter Model

• Since the problem is symmetrical, only model a quarter of the entire simulation.
• Ensure that the geometry reflects this symmetry in both the fluid and sphere parts.

Step 4: Apply Plane Symmetric Boundary Conditions

• Use the SPC (Single Point Constraint) set to implement plane symmetric boundary conditions.
• Ensure that the boundaries are correctly constrained to maintain the symmetry during the simulation.

Step 5: Define Interaction Between Lagrange and ALE

• Establish the coupling mechanisms between the Lagrangian (solid) and ALE (fluid) components.
• This ensures proper interaction and behavior between the sphere and the fluid during the drop event.

Step 6: Set Up d3plot Intervals

• Determine the total number of plots needed for your analysis.
• Configure the d3plot intervals to facilitate data visualization and analysis.

Step 7: Display Overlay Graph

• After running the simulation, use the post-processing tools to display overlay graphs.
• This will help visualize the interaction between the sphere and the water effectively.

Step 8: Plot the Fluid-Structure Interaction Database

• Access the relevant data from the simulation results.
• Plot the FSI (Fluid-Structure Interaction) database to analyze the results of the interaction.

Conclusion

In this tutorial, you learned how to set up a simulation of a sphere dropping on water using the ALE method in LS-DYNA. Key steps included creating fluid and domain parts, modifying the sphere density, applying symmetric boundary conditions, and visualizing the results. For further exploration, consider looking into the references provided in the video description for more advanced applications of the ALE method.