Sloshing Simulation in Cylindrical Water Storage Tanks: An Abaqus Modeling Framework

2.3. PROJECT PROCEDURES

The tank sloshing simulation is performed in Abaqus CAE, without the need for Python scripts or Fortran subroutines. To do so, we have created a standard/Explicit model database. Then, we performed the tank sloshing simulation, step-by-step.

In summary, the tank sloshing simulation procedure is as follows:

• Setting up the software environment and choosing Abaqus units
• Creating the parts
• Defining the material and section properties
• Making an instance of the model in the Assembly module
• Creating a step, choosing the outputs, and applying the ALE adaptive meshing settings
• Defining the interactions
• Applying the boundary conditions and loads
• Generating elements and assigning element types
• Submitting the job

It was the general tank sloshing simulation procedure that you must execute. However, liquid sloshing is a complex problem that you need to consider some important aspects during the modeling procedure, as we have discussed in the following.

• Simulation of Water Behavior: One of the main challenges is modeling the behavior of water in a simplified manner. To address this, we have used the Us-Up model in Abaqus CAE, where the water is assumed to be incompressible for simplification. This assumption has a negligible effect on the results of tank sloshing simulation, as discussed in many published papers. A large number of these papers have assumed water to be incompressible, while others have assigned a very low value for viscosity. In this project, we have discussed the consideration of both inviscid and low-viscosity scenarios for water in Abaqus.
• The ALE Adaptive Meshing Technique: During an earthquake, the liquid inside a tank may undergo significant deformations. This can present a challenge for the numerical tank sloshing simulation, as mesh quality may be decreased during the solution. The issue is more critical for cylindrical tanks compared to rectangular ones, due to the irregular element shapes. This issue can impact results or even stop the solution due to poor mesh quality. One way to address this concern is by using the Arbitrary Lagrangian-Eulerian (ALE) adaptive meshing technique in Abaqus. This approach automatically enhances mesh quality during the solution. In this project, we have guided you through utilizing the ALE technique in Abaqus for the tank sloshing simulation.
• Utilizing Hourglass Controls: Water is a low-viscosity or even an inviscid liquid. When defining a low-viscosity material in Abaqus, the hourglass forces are insufficient to prevent hourglass modes. Therefore, we must utilize hourglass controls when defining the elements. This allows for the addition of stiffness to prevent hourglass modes. In this project, we have guided you step-by-step to utilize hourglass controls in Abaqus for the liquid sloshing simulation in a water tank.
• The Overall Procedure: We have discussed some challenges, that you will face up during the tank sloshing simulation. However, you may encounter additional complexities, including difficulties in defining fluid-structure interactions, loading, and applying boundary conditions. Therefore, we have included a workshop in this package to provide a step-by-step guide for Abaqus sloshing simulation in a ground-supported water tank. The tank is analyzed under the horizontal acceleration of the El-Centro earthquake. We hope it will be helpful for you.

3. Workshop (Video file): A Step-by-step Guide on the Simulation of Liquid Sloshing

In the workshop, we selected a cylindrical ground-supported water tank under the horizontal acceleration of the El-Centro earthquake. The workshop provides a full step-by-step guide through a video to simplify the simulation of liquid sloshing.

In the video, we used a dynamic explicit step and defined all the necessary outputs for the liquid sloshing. Then, the Adaptive Meshing technique was employed to improve mesh quality. Following this, we defined the interactions between the fluid and structure in a reasonably simple way. Then we applied the boundary conditions and loads, such as earthquake acceleration, gravity acceleration, and hydrostatic pressure. Moreover, the workshop guides you through the meshing process, considering the utilization of hourglass controls.

We verified the Abaqus sloshing simulation to ensure the accuracy of the modeling procedure. For verification, we have analyzed the behavior of a water tank and extracted the liquid sloshing height over time. As in the reference paper, just the horizontal component of the El-Centro earthquake is considered for the Tank sloshing simulation. We have compared the obtained results with the ANSYS APDL solution in the paper titled “Parametric study on dynamic behavior of cylindrical ground-supported tanks”. The paper is one of the well-known research projects that performed the sloshing simulation in cylindrical tanks.

It would be helpful to see Abaqus Documentation to understand how it would be hard to start an Abaqus simulation without any Abaqus tutorial.

One note, when you are simulating in Abaqus, be careful with the units of values you insert in Abaqus. Yes! Abaqus don’t have units but the values you enter must have consistent units. You can learn more about the system of units in Abaqus.