ansys workbench 流固耦合计算实例

Oscillating Plate with Two-Way Fluid- Structure Interaction

Introduction

This tutorial includes:

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Features

Overview of the Problem to Solve

Setting up the Solid Physics in Simulation (ANSYS Workbench)

Setting up the Fluid Physics and ANSYS Multi-field Settings in ANSYS CFX-Pre

Obtaining a Solution using ANSYS CFX-Solver Manager

Viewing Results in ANSYS CFX-Post

If this is the first tutorial you are working with, it is important to review the following topics

before beginning:

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Setting the Working Directory

Changing the Display Colors

Unless

you

plan

on

running

a

session

file,

you

should

copy

the

sample

files

used

in

this

tutorial from the installation folder for your software (/examples/) to your working

directory. This prevents you from overwriting source files provided with your installation. If you

plan to use a session file, please refer to Playing a Session File.

Sample files referenced by this tutorial include:

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1.

Features

This tutorial addresses the following features of ANSYS CFX.

Component

Feature

User Mode

ANSYS CFX-Pre

Simulation Type

ANSYS Multi- field

General Mode

Transient

Details

Component

Feature

Fluid Type

Domain Type

Turbulence Model

Heat Transfer

Output Control

General Fluid

Single Domain

Laminar

None

Monitor Points

Details

Transient Results File

Wall: Mesh Motion = ANSYS MultiField

Boundary Details

Wall: No Slip

Wall: Adiabatic

Timestep

Transient

Animation

ANSYS CFX-Post

Plots

Contour

Vector

In this tutorial you will learn about:

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Moving mesh

Fluid-solid interaction (including modeling solid deformation using ANSYS)

Running an ANSYS Multi-field (MFX) simulation

Post-processing two results files simultaneously.

2.

Overview of the Problem to Solve

This tutorial uses a simple oscillating plate example to demonstrate how to set up and run a

simulation

involving

two-way

Fluid-Structure

Interaction,

where

the

fluid

physics

is

solved

in

ANSYS CFX and the solid physics is solved in the FEA package ANSYS. Coupling between the

two solvers is required throughout the solution to model the interaction between fluid and solid as

time progresses, and the framework for the coupling is provided by the ANSYS Multi-field solver,

using the MFX setup.

The geometry consists of a 2D closed cavity. A thin plate is anchored to the bottom of the

cavity as shown below:

An initial pressure of 100 Pa is applied to one side of the thin plate for 0.5 seconds in order to

distort it. Once this pressure is released, the plate oscillates backwards and forwards as it attempts

to regain its equilibrium (vertical) position. The surrounding fluid damps the oscillations, which

therefore

have

an

amplitude

that

decreases

in

time.

The

CFX

Solver

calculates

how

the

fluid

responds to the motion of the plate, and the ANSYS Solver calculates how the plate deforms as a

result of both the initial applied pressure and the pressure resulting from the presence of the fluid.

Coupling between the two solvers is required since the solid deformation affects the fluid solution,

and the fluid solution affects the solid deformation.

The

tutorial

describes

the

setup

and

execution

of

the

calculation

including

the

setup

of

the

solid physics in Simulation

(within ANSYS Workbench) and the setup of the

fluid physics and

ANSYS Multi-field settings in ANSYS CFX-Pre. If

you do not have ANSYS Workbench, then

you can use the provided ANSYS input file to avoid the need for Simulation.

3.

Setting up the Solid Physics in Simulation (ANSYS Workbench)

This

section

describes

the

step-by-step

definition

of

the

solid

physics

in

Simulation

within

ANSYS Workbench that will result in the creation of an ANSYS input file . If

you prefer, you can instead use the provided file and continue from Setting up

the Fluid Physics and ANSYS Multi-field Settings in ANSYS CFX-Pre.

Creating

a New Simulation

1.

If required, launch ANSYS Workbench.

2.

Click

Empty Project

. The

Project

page appears displaying an unsaved project.

3.

Select

File

>

Save

or click

Save

button.

4.

If required, set the path location to a different folder. The default location is your working

directory. However, if you have a specific folder that you want to use to store files created

during this tutorial, change the path.

5.

Under

File name

, type OscillatingPlate.

6.

Click

Save

.

7.

Under

Link to Geometry File

on the left hand task bar click

Browse

. Select the provided

file and click

Open

.

8.

Make sure that is highlighted and click

New simulation

from the

left- hand taskbar.

Creating the Solid Material

1.

When Simulation opens, expand Geometry in the project tree at the left hand side of the

Simulation window.

2.

Select Solid, and in the

Details

view below, select

Material

.

3.

Use

the

arrow

that

appears

next

to

the

material

name

Structural

Steel

to

select

New

Material

.

4.

When the

Engineering Data

window opens, right-click New Material from the tree view

and rename it to Plate.

5.

Enter 2.5e06 for

Young's Modulus

, 0.35 for

Poisson's Ratio

and 2550 for

Density

.

Note that the other properties are not used for this simulation, and that the units for these

values are implied by the global units in Simulation.

6.

Click

the

Simulation

tab

near

the

top

of

the

Workbench

window

to

return

to

the

simulation.

Basic Analysis Settings

The ANSYS Multi-field simulation is a transient mechanical analysis, with a timestep of 0.1 s

and a time duration of 5 s.

1.

Select

New Analysis

>

Flexible Dynamic

from the toolbar.

2.

Select Analysis Settings from the tree view and in the

Details

view below, set

Auto Time

Stepping

to Off.

3.

Set

Time Step

to 0.1.

4.

Under

Tabular

Data

at

the

bottom

right

of

the

window,

set

End

Time

to

5.0

for

the

Steps

= 1 setting.

Inserting Loads

Loads are applied to an FEA analysis as the equivalent of boundary conditions in ANSYS

CFX. In this section, you will set a fixed support, a fluid-solid interface, and a pressure load.

Fixed

Support

The fixed support is required to hold the bottom of the thin plate in place.

1.

Right-click

Flexible

Dynamic

in

the

tree

and

select

Insert

>

Fixed

Support

from

the

shortcut menu.

2.

Rotate

the

geometry

using

the

Rotate

solid is visible, then select

Face

button

so

that

the

bottom

(low-y)

face

of

the

and click the low-y face.

That face should be highlighted to indicate selection.

3.

Ensure

Fixed Support

is selected in the

Outline

view, then, in the

Details

view, select

Geometry

and click 1 Face to make the

Apply

button appear (if necessary). Click

Apply

to set the fixed support.

Fluid-Solid Interface

It is necessary to define the region in the solid that defines the interface between the fluid in

CFX and the solid in ANSYS. Data is exchanged across this interface during the execution of the

simulation.

1.

Right-click Flexible Dynamic in the tree and select

Insert

>

Fluid Solid Interface

from

the shortcut menu.

2.

Using

the

same

face- selection

procedure

described

earlier,

select

the

three

faces

of

the

geometry that form the interface between the solid and the fluid (low-x, high-y and high-x

faces)

by

holding

down

to

select

multiple

faces.

Note

that

this

load

is

automatically given an interface number of 1.

Pressure

Load

The pressure load provides the initial additional pressure of 100 [Pa] for the first 0.5 seconds

of the simulation. It is defined using a step function.

1.

Right-click Flexible Dynamic in the tree and select

Insert

>

Pressure

from the shortcut

menu.

2.

Select the low-x face for

Geometry

.

3.

In the

Details

view, select

Magnitude

, and using the arrow that appears, select

Tabular

(Time)

.

4.

Under

Tabular Data

, set a pressure of 100 in the table row corresponding to a time of 0.

Note:

The

units

for

time

and

pressure

in

this

table

are

the

global

units

of

[s]

and

[Pa]

,

respectively.

5.

You now need to add two new rows to the table. This can be done by typing the new time

and

pressure

data

into

the

empty

row

at

the

bottom

of

the

table,

and

Simulation

will

automatically re-order the table in order of time value. Enter a pressure of 100 for a time

value of 0.499, and a pressure of 0 for a time value of 0.5.

This gives a step function for pressure that can be seen in the chart to the left of the table.

Writing the ANSYS Input File

The

Simulation

settings

are

now

complete.

An

ANSYS

Multi-field

run

cannot

be

launched

from within Simulation, so the

Solve

buttons cannot be used to obtain a solution.

1.

Instead,

highlight

Solution

in

the

tree,

select

Tools

>

Write

ANSYS

Input

File

and

choose to write the solution setup to the file .

2.

The mesh is automatically

generated as part of this process. If

you want to examine it,

select Mesh from the tree.

3.

Save the Simulation database, use the tab near the top of the Workbench window to return

to the

Oscillating Plate [Project]

tab, and save the project itself.

4.

Setting up the Fluid Physics and ANSYS Multi-field Settings in ANSYS CFX-Pre

This section describes the step-by-step definition of the flow physics and ANSYS Multi-field

settings in ANSYS CFX-Pre.

Playing a Session File

If you want to skip past these instructions and to have ANSYS CFX-Pre set up the simulation

automatically, you can select

Session

>

Play Tutorial

from the menu in ANSYS CFX-Pre, then

run

the

session

file:

.

After

you

have

played

the

session

file

as

described

in

earlier

tutorials

under

Playing

the

Session

File

and

Starting

ANSYS

CFX-Solver

Manager,

proceed to Obtaining a Solution using ANSYS CFX-Solver Manager.

Creating a New Simulation

1.

Start ANSYS CFX-Pre.

2.

Select

File

>

New Simulation

.

3.

Select

General

and click

OK

.

4.

Select

File

>

Save Simulation As

.

5.

Under

File name

, type OscillatingPlate.

6.

Click

Save

.

Importing the Mesh

1.

Right-click Mesh and select

Import Mesh

.

2.

Select the provided mesh file, and click

Open

.

Note

：

The file that was just created in Simulation, , will be used as an

input file for the ANSYS Solver.

Setting the Simulation Type

A transient ANSYS Multi-field run executes as a series of timesteps. The

Simulation Type

tab is used both to enable an ANSYS Multi-field run and to specify the time-related settings for it

(in the

External Solver Coupling

settings). The ANSYS input file is read by ANSYS CFX-Pre so

that it knows which Fluid Solid Interfaces are available.

Once the timesteps and time duration are specified for the ANSYS Multi-field run (coupling

run), ANSYS CFX automatically picks up these settings and it is not possible to set the timestep

and time duration independently. Hence the only option available for

Time Duration

is Coupling

Time Duration, and similarly for the related settings Time Step and Initial Time.

1.

Click

Simulation Type

.

2.

Apply the following settings

Tab

Setting

External Solver Coupling > Option

Value

ANSYS MultiField

External Solver Coupling > ANSYS Input File

[

a

]

Coupling

Time

Control

>

Coupling

Time

Duration

>

Total

Time

Basic

Settings

Coupling Time Control > Coupling Time Steps > Option

5 [s]

Timesteps

Coupling Time Control > Coupling Time Steps > Timesteps

0.1 [s]

Simulation Type > Option

Simulation Type > Time Duration > Option

Simulation Type > Time Steps > Option

Simulation Type > Initial Time > Option

[

a

]

Transient

Coupling Time Duration

Coupling Time Steps

Coupling Initial Time

This file is located in your working directory.

3.

Click

OK

.

Note

：

You may see a physics validation message related to the difference in the units used in

ANSYS CFX-Pre and the units contained within the ANSYS input file. While it is important to

review

the

units

used

in

any

simulation,

you

should

be

aware

that,

in

this

specific

case,

the

message is not crucial as it is related to temperature units and there is no heat transfer in this case.

Therefore, this specific tutorial will not be affected by the physics message.

Creating the Fluid

A custom fluid is created with user- specified properties.

1.

Click

Material

.

2.

Set the name of the new material to Fluid.

3.

Apply the following settings

Tab

Option

Basic Settings

Thermodynamic State

Thermodynamic State > Thermodynamic State

Material Properties

Equation of State > Molar Mass

Setting

Value

Pure Substance

(Selected)

Liquid

1 [kg kmol^-1]