-
Oscillating Plate with Two-Way
Fluid-Structure Interaction
ANSYS-China
Introduction
This
tutorial includes:
?
Features
*
Overview of the
Problem to Solve
?
Setti ng up the Solid Physics in
Simulatio n (ANSYS Workbe nch)
?
Setti ng up the
Fluid Physics and ANSYS Multi-field Setti ngs in
ANSYS CFX-Pre
?
Obta ining a Solution using ANSYS CFX-
Solver Ma nager
?
Viewi ng
Results in ANSYS CFX-Post
If this is
the first tutorial you are working with, it is
important to review the following topics before
begi nning:
*
Sett ing the Worki ng Directory
*
Cha nging the Display
Colors
Uni ess you pla n on running a
sessi on file, you should copy the sample files
used in this tutorial
from the in
stallati on folder for your software
(
This preve nts you from overwriti ng
source files provided with your in stallatio n. If
you pla n to use a
sessi on file,
please refer to Play ing a Sessi on File.
Sample files refere need by this
tutorial in clude:
*
Oscillati
*
Oscillati
*
Oscillat in
*
Oscillati ngPlate.i np
1.
Features
This tutorial
addresses the followi ng features of ANSYS CFX.
Component
ANSYS
CFX-Pre
Feature
User Mode
General Mode
Details
Component
Feature
Transient
Simulation Type
ANSYS Multi-
field
Fluid Type
Domain Type
Turbulence Model
Heat
Transfer
General Fluid
Single Domain
Laminar
None
Monitor Points
Output Control
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 lear n about:
?
Moving mesh
*
*
*
Fluid-solid
in teract ion (in cludi ng modeli ng solid
deformati on using ANSYS)
Running an
ANSYS Multi-field (MFX) simulatio n
Post-process ing two results files
simulta neously.
2.
Overview
of the Problem to Solve
This tutorial
uses a simple oscillat ing plate example to dem on
strate 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 soluti on to model the in
teract ion betwee n fluid and solid as time
progresses, and the framework for the
coupli ng is provided by the ANSYS Multi-field
solver, using
the MFX setup.
The geometry con sists of a 2D closed
cavity. A thin plate is an chored to the bottom of
the
cavity as show n below:
An in itial
pressure of 100 Pa is applied to one side of the
thin plate for 0.5 sec onds 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 resp
onds to the
moti on of the plate, and
the ANSYS Solver calculates how the plate deforms
as a result of both the
in itial
applied pressure and the pressure result ing from
the prese nee of the fluid. Coupli ng betwee
n the two solvers is required si nee
the solid deformati on affects the fluid soluti
on, 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 Simulati on
(withi n ANSYS Workbe nch) and the
setup of the fluid physics and
ANSYS
Multi-field sett ings in ANSYS CFX-Pre. If you do
n ot have ANSYS Workbe nch, the n you
can use the provided ANSYS in put file
to avoid the n eed for Simulatio n.
3.
Setting up the Solid Physics in
Simulation (ANSYS Workbench)
This secti
on describes the step-by-step defi niti on of the
solid physics in Simulati on with in
ANSYS Workbe nch that will result in
the creation of an ANSYS in put file Oscillati
ngPlate.i np. If you
prefer, you can in
stead use the provided Oscillati ngPlate.i np file
and continue from Sett ing up the
Fluid
Physics and ANSYS Multi-field Setti ngs in ANSYS
CFX-Pre.
Creating
a New
Simulatio n
1.
If required,
lau nch ANSYS Workbe nch.
2.
Click
Empty
Project
. The
Project
page appears displaying an unsaved
project.
3.
Select
File
>
Save
or click Save butt on.
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.
Un der
File name
, type Oscillat in
gPlate.
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-
ha nd taskbar.
Creati ng the Solid Material
1.
When Simulatio n ope ns,
expa nd Geometry in the project tree at the left
hand side of the
Simulatio n win dow.
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 ope
ns, right-click New Material from the tree view
and ren ame it to Plate.
乱
i i i
ii-.i
1
ir - 11 j
j|
-|^i y
IH
AW
-
T* . EE/wiBBriniiiX |
-
-
丙
Ffe UrWi T^i
*
Malff
Q
冠
SbiUcHMl 5
诟
*
工
L
on
vwMani
{Ip
Agridiri
AM
匕■曲亡■■
1
t
Hwt&riw
期
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
simulati on, and that the un its for these
values are implied by the global un its
in Simulati on.
6.
Click the
Simulation
tab near the top
of the Workbench window to return to the simulatio
n.
Basic An alysis Sett ings
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 An alysis Setti ngs 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 sett in
g.
Inserting Loads
Loads are
applied to an FEA an alysis as the equivale nt of
boun dary con diti ons in ANSYS
CFX. In
this sect ion, you will set a fixed support, a
fluid-solid in terface, 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
butt on so that the bottom (low-y) face
of the
solid is visible, then select
Face
囲
and click
the low-y face.
That face should be
highlighted to in dicate selecti on.
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
butt on appear (if n
ecessary). Click
Apply
to
set the fixed support.
Fluid-Solid Interface
It is
n ecessary to defi ne the regi on in the solid
that defi nes the in terface betwee n the fluid in
CFX and the solid in ANSYS. Data is
excha nged across this in terface duri ng the
executi on of the
simulatio n.
1.
Right-click Flexible
Dynamic in the tree and select
the
shortcut menu.
2.
Using the
same face-selection procedure described earlier,
select the three faces of the
geometry
that form the in terface betwee n the solid and
the fluid (low-x, high-y and high-x
faces) by holding down
give n an in terface nu
mber of 1.
Pressure
Load
The pressure
load provides the in itial additi onal pressure of
100 [Pa] for the first 0.5 sec onds of
the simulati on .It is defi ned using a
step function.
1.
Right-
click Flexible Dyn amic in the tree and select
Insert
>
Pressure
from the shortcut
menu.
Insert
>
Fluid Solid Interface
from
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 n eed to add two new rows to
the table. This can be done by typi ng 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.
.Tabular Data
Steps
Time
1
1
2
1
3
1
4
1
F
|
ioo
:
0
a 499
100
0.5
a
5
a.
w
This gives a step function
for pressure that can be see n in the chart to the
left of the table.
Writi ng the ANSYS
In put File
The Simulation settings are
now complete. An ANSYS Multi-field run cannot be
launched from
with in Simulati on, so
the
Solve
butt ons cannot be
used to obta in a soluti on.
1.
In stead, 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 gen erated as part of this process.
If you want to exam ine 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 follow ing sett ings
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
Coupling Time Control > Coupling Time
Steps > Timesteps
Simulation Type >
Option
Simulation Type > Time Duration
> Option
Simulation Type > Time Steps >
Option
Simulation Type > Initial Time >
Option
5 [s]
Timesteps
0.1 [s]
Transient
Coupling Time Duration
Coupling Time Steps
Coupling
Initial Time
呵
This file is located in your working
directory.
3.
Click
OK
.
Note
：
You may see a physics validation
message related to the differenee in the units
used in
ANSYS CFX-Pre and the units con
tai ned withi n the ANSYS in put file. While it is
importa nt 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 un its and
there is no heat tran sfer in this case.
Therefore, this specific tutorial will
not be affected by the physics message.
Creat ing the Fluid
A custom
fluid is created with user-specified properties.
1.
Click Material
因
.
2.
Set the n ame of the new material to
Fluid.
3.
Apply the follow
ing sett ings
Tab
Option
Basic Settings
Thermodynamic State
Thermodynamic State > Thermodynamic
State
Setting
Value
Pure
Substance
(Selected)
Liquid
1 [kg kmol
A
-1]
Material Properties
Equation
of State > Molar Mass