Ansys manual v 13 ejercicio

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Tutorial: Fuel Tank Sloshing

Introduction
The purpose of this tutorial is to investigate the free surface movement of liquid fuel in a tank under varying acceleration scenarios and to determine the most suitable configuration of the fuel tank to ensure continuous fuel supply through the pick-up pipe. Two configurations of the fuel tank are considered—tank with internal baffles and tank withoutinternal baffles. You will compare the two configurations on the basis of liquid interface and velocity vector plots generated for each case. This tutorial demonstrates how to do the following: • Set up and solve a transient problem using the pressure-based solver and the VOF model. • Define parameters specific to the Non-Iterative Time Advancement (NITA) scheme. • Create a journal file to track the liquidinterface with time. • Request automatic execution of commands to create images for postprocessing. • Compare the two configurations on the basis of liquid interface and velocity vector plots generated.

Prerequisites
This tutorial assumes that you are familiar with the FLUENT interface and have a good understanding of the basic setup and solution procedures. Some steps will not be shown explicitly.In this tutorial, you will use the volume of fluid (VOF) model. This tutorial does not cover the mechanics of using this model. Instead, it focuses on the application of the model to this case. If you have not used the VOF model before, refer to Section 23.10: Setting Up the VOF Model in the FLUENT 6.3 User’s Guide and Tutorial 17: Using the VOF Model in the FLUENT 6.3 Tutorial Guide.

c FluentInc. January 29, 2007

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Fuel Tank Sloshing

Problem Description
The tutorial considers two configurations of the fuel tank for comparison. Figure 1 shows the tank with internal baffles. Figure 2 shows the tank without baffles. The tank undergoes an acceleration of 9.81 m/s2 in the positive X direction. Recall that if the tank accelerates in the +X direction, the liquid experiences an equal andopposite reaction in the −X direction. After 1.5 seconds, the acceleration in the X direction stops and only gravity (in the −Z direction) acts on the liquid in the tank. A prior analysis indicates that the pick-up pipe might not be completely submerged after 0.45 seconds of acceleration and after 1.25 seconds of acceleration. An analysis of both tank designs will be compared after 0.45 seconds and 1.25seconds to confirm that the pickup pipe in the tank without baffles is not submerged in fuel while the tank with baffles will be analyzed to see if the baffles fix the problem and keep the pick-up pipe completely submerged in fuel. The tank with baffles will be analyzed first. Then, the baffles will be switched from wall boundaries to interior boundaries and the tank without baffles will be analyzed under thesame conditions as the tank with baffles.

Figure 1: Schematic of Tank with Baffles

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c Fluent Inc. January 29, 2007

Fuel Tank Sloshing

Figure 2: Schematic of Tank without Baffles

Preparation
1. Copy the mesh file ft11.msh.gz to the working folder. 2. Start the 3D (3d) version of FLUENT.

Setup and Solution for Configuration with Baffles
Step 1: Grid 1. Read the mesh file (ft11.msh.gz). 2. Scale the gridusing a scale factor of 0.01 in the X, Y , and Z directions. 3. Check and display the grid (Figure 3).

c Fluent Inc. January 29, 2007

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Fuel Tank Sloshing

Y Z X

Grid

FLUENT 6.3 (3d, pbns, lam)

Figure 3: Grid Display

4. Reorder the domain until the bandwidth reduction is of the order of 1.0. Grid −→ Reorder −→Domain Step 2: Models 1. Define the solver settings. (a) Select Unsteady from theTime list and retain the default Unsteady Formulation of 1st-Order Implicit. (b) Enable Non-Iterative Time Advancement in the Transient Controls group box. (c) Select Green-Gauss Node Based from the Gradient Option list. (d) Click OK to close the Solver panel. 2. Define the multiphase model. (a) Select Volume of Fluid from the Model list. (b) Enable the Implicit Body Force formulation. (c) Click...
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