simman tut 01 backstep

8/4/2019 SimMan Tut 01 Backstep

1/20

T01-SM-01 CFD-Simulation Manager Tutorials 1-13/20/02

Tutorial 1 Parametric Study of

Flow Over a BackwardFacing Step

Problem Description

In this Tutorial we present an automated parametric study of laminar flow over a backward facing

step. Based on a table of input values, Simulation Manager calls CFD-GEOM to update model

geometry and grid, changes boundary conditions, then runs the CFD-ACE+ solver for each case.

In this Tutorial, we vary the dimensions of the step, h ands, and the value of x-direction velocity on

the inlet boundary (see Figure 1-1). There are three steps in performing this parametric study:

1. Create original geometry and grid in CFD-GEOM2. Define the model in CFD-ACEU

3. Run the parametric study in Simulation Manager

These steps are described in detail in this tutorial.

Figure 1-1. Problem Geometry


2/20

Tutorial 1: Parametric Study of Flow Over a Backward Facing Step

1-2 CFD-Simulation Manager Tutorials T01-SM-01

Step A: Create the Geometry and Journal File

In the following steps we prepare the geometry and structured grid for the backward facing step.Before creating the geometry, you will activate the CFD-GEOM journaling option. This tells CFD-

GEOM to create a journal file, or recipe, containing instructions for re-creating the geometry and

grid. The journal file will contain definitions of parameters that will be controlled by Simulation

Manager.

1. Start CFD-GEOM.

2. Create parameters for the model.

Start CFD-GEOM.

Select SettingPreferences Geometry

Ensure that the Journaling checkbox is

selected.

Select OK to close the Preferences panel.

Note If, in the previous step, the Journaling checkbox was not already active when you opened

the Geometry panel, you must restart CFD-GEOM after selecting the Journaling check-

box.

In this step we create parameters using the parameter creation tool in CFD-GEOM. These parame-

ters are changed during the parametric study to create different designs.


3/20


T01-SM-01 CFD-Simulation Manager Tutorials 1-3

3. Create points for the geometry.

Create parameters:

Choosing: Tools Parameters

Click the New Field button three times to

create three rows of data entry fields.

Enter the data as shown below:

Click Apply and OK to close the Parameterspanel.

Select GeometryPoint CreationPoint. The Point->Create panel appears as shown here:


4/20



4. Create line segments joining the points created.

Enter the following points being sure to select

the Apply button after entering each point:

The points should appear as shown in figure 1-2.

Note that several points hide behind each

other. It will be necessary to zoom in on the

areas where cluster of points are, and hover over

the point. This will display the points XYZ

coordinates.

Figure 1-2. Geometry points

Select GeometryLine CreationLine. To draw the lines for this step it is necessary to

zoom and hover over points to insure the correct

one is selected.This is illustrated in the

figure shown here. Note

thatLabel Numbercorre-

sponds to the order in

which the points were cre-

ated. In this case,Label

Number: 1 is P1 (cre-

ated in the previous step) .

Point X Value Y Value Z Value

P1 0 0 0

P2 0 s 0

P3 -0.04 s 0

P4 -0.04 m 0

P5 0 m 0

P6 0.2 0 0

P7 0.2 s 0

P8 0.2 m 0
http://-/?-http://-/?-


5/20



Select the following points in the order shown

being sure to press Apply after selecting each

pair of points.

P1-P2

P2-P3

P3-P4

P4-P5

P6-P7

P7-P8

P5-P8 P2-P5

P1-P6

After all lines are created, the geometry should

appear as shown in figure 1-3.

Figure 1-3. Created Line Segments
http://-/?-http://-/?-


6/20



5. Create edges on the lines created.

Create edges by choosing the tool: Grid Struc-

tured Edge OptionsCreate (Edit) StructuredEdge.

The Edge->Create panel appears as shown here.


7/20



According to the table shown below and figure 1-4, enter the specified parameters to create all

edges. Click the Apply button after entering the parameters for each edge.

Figure 1-4. Edges

EdgeNumberof Points Distribution delta-s 1 delta-s 2

PowerLawPower

1 81 Hyperbolic Tan 0.02 0.0005 -

2 81 Hyperbolic Tan 0.0005 0.02 -

3 21 Hyperbolic Tan 0.0005 0.005 -

4 21 Hyperbolic Tan 0.005 0.0005 -

5 11 Power Law - - Forward




http://-/?-http://-/?-


8/20



6. Create faces on the geometry.

Create two faces by choosing the tool: Grid

Structured Face OptionsCreate StructuredFace.

The Face->Create panel appears as shown here.

Create Face 1 using edges 3, 4, 5, and 6 being sure to

click the middle mouse button after selecting each edge.

In a similar manner, create Face 2 using edges 1, 2, 6, 7, 8, and 9. Note that edges 6 and 7, mustbe entered as one set, therefore do not press the middle mouse button after selecting edge 6, but

after select 6 and 7. (This also applies to edges 8 and 9).


9/20



7. Create 2D blocks.

Create blocks by choosing the Tool: Grid

Structured Block OptionsCreate Structured2D Block.

The status line prompts you to select faces to

create a 2D block.

Select Face 1 and press the middle mouse button

to create Block .

In a similar manner create Block 2 using Face 2.


10/20



8. Set Boundary Conditions.

To activate the BC/VC editor:

Click on the collapse bar located above the entity bar .

From the panel that opens,

click on the BC/VC Editor

tab.

In the 2D/3D section of

the BC/VC editor panel,

select the 2D

ModelBoundary.

In the viewer window, select Edge 5.

In the BC/VC Editor, select Inlet from theType menu and enter Inlet in the Name

field.

Click Apply.


11/20



9. Save the model.

Step B: Setup and Run the Simulation in CFD-GUI

If you are already comfortable with CFD-GUI/ACE(U) operations, then you may follow these

quick start instructions to quickly set up the simulation. If you have difficulties performing these

steps then it is recommended that you stop here and go through CFD-ACEU Tutorial 1, "Laminar

Flow Past a Backward Facing Step", located in Volume 2 of the CFD-ACE Tutorial Manual.

1. Load the DTF File and Title the Simulation.Select File -> Open and read backstep.DTF

2. Specify the Problem Type Settings.PT -> Modules

Activate Flow


In the BC/VC Editor, select Outlet from

the Type menu and enter Outlet in theName field.

Click Apply.


In the BC/VC Editor, select Outlet from

the Type menu and enter Outlet in the

Name field.

Click Apply.

From the File menu:

Select Save As DTF and click OK to save

the file as backstep.DTF.

Select Save As and save the model as

backstep. GGD

When the GGD file is created, the journal file

(backstep.py) is automatically created. We will

set up the DTF file for the CFD-ACE+ solver inthe next part of this tutorial.
http://../Tutorials/AceV6.6/T99-A-02/doc/T99-A-02.pdfhttp://../Tutorials/AceV6.6/T99-A-02/doc/T99-A-02.pdfhttp://../Tutorials/AceV6.6/T99-A-02/doc/T99-A-02.pdfhttp://../Tutorials/AceV6.6/T99-A-02/doc/T99-A-02.pdf


12/20



3. Specify the Model Options.MO -> Shared

Polar: non-axisymmetric

Time Dependence = Steady

Gravity: off

Rotation: off

MO -> Flow

Simple Flow Model: off

Reference Pressure = 100000 N/m2

4. Specify the Volume Condition Properties.

VC -> PropertiesSelect All VCs (2) Group

Fluid Properties:

Density (Constant) 1.15 kg/m3

Viscosity (Constant Kinematic) = 1.5e-5 m2/s

5. Specify the Boundary Condition Values.BC -> General

Inlets(1)

Flow ->Fix.Vel.(Cartesian)-> U=0.2885 V=0 P=0 T=300

Outlets(2) Group

Flow ->Fixed Pressure-> P=0 T=300

6. Specify the Initial Condition Settings.IC -> Initial Conditions: For All Volumes

IC Sources: Constant

Flow -> U=0.2 V=0 P=0 T=300

7. Specify the Solver Control Settings.SC -> Max. Iterations = 100

SC -> Spatial Differencing

Velocity: Central 0.01 blending

Density: Central 0.01 blending

SC -> Solvers

Velocity: CGS+Pre, 50 sweeps, 0.0001 criteria

Pressure Correction: CGS+Pre, 500 sweeps, 0.0001 criteria

SC -> Relaxation


13/20



Velocities 0.1

P Correction 0.1

Pressure 1.0

Density 1.0Viscosity 1.0

8. Specify the Output Options.SC -> Output

Output Results: End of Simulation

SC -> Print

Mass Flow Summary: on

SC -> Graphics

Velocity Vector: on

Static Pressure: on

Stream Function: on

9. Save DTF FileFile->Save

Step C: Parametric Study Using SimManager

1. Start Simulation Manager.

Start Simulation Manager by typing SimMan-

ager from the command line prompt; or if you

using Windows, use the Start Menu to bring it

up as follows.

Start ProgramsCFDRCSimulation Man-

ager.

The Simulation Manager interface is launched

(figure 1-5).
http://-/?-http://-/?-


14/20



2. Run the Simulation Manager.

Figure 1-5. Simulation Manager Main Window

From the toolbar of Simulation Managers inter-

face, click the icon Parametric Studies using

CFD-GEOM and CFD-ACEUA Solver parame-ters (see figure 1-5).

The window shown in figure 1-6 opens.
http://-/?-http://-/?-http://-/?-http://-/?-


15/20



Figure 1-6. Specify CFD-GEOM and Solver Parameters Panel

Next to the DTF file text box, click

Browse and locate the file back-

step.DTF in the tutorials directory.

Select Use CFD-GEOM Parameters check

button.

Next to the CFD-GEOM script file text

box, click Browse and locate the file

backstep.py in the tutorials directory.


16/20



Make sure that option Import Parametric Table

from Text File is selected.

The lower portion of the panel appears as shown

here:

Click the Browse button and open the file

backstep_parameter.txt.

This text file was created using MS Excel. The

file backstep_parameter.txt must be in the for-

mat, specified in the manual. This file defines

the step dimensions and inlet velocity valuesthat will be used in this parametric study.

Click the Next button.

Information about optional collecting CFD-

ACEU Solver Output data and using previous

run for Initial Condition appears on these input

fields. You can ignore this data for this tutorial.

Click the Next button.

Table with the parameters for your case appears

on the screen. Any parametric value in this tablecan be selected and modified.


17/20



3. View the Residuals

Click Run All to begin the parametric study. When the simulation starts, CFD-GEOM is

called (in background mode) to run the journal

file. After new geometry and grid are created

using the CFD-GEOM parameters (h and s), theboundary condition value (velocity) is updated.

CFD-ACEU is then called to solve the flow in

the model. This process repeats until all three

combinations of the parameters have been ana-

lyzed. Each case produces a different DTF file

named backstep.0000n.DTF, where n is the

case number. File backstep.rst is also created

and contains information to restart the paramet-

ric study.

You can view the CFD-ACEU solution residuals

of each case while the parametric study is run-

ning or after it. One way to view the residuals is

to select View Residuals from the Tools menu,

or click the corresponding icon on the toolbar.

Another way is to select the corresponding para-metric case in the table and select option View

Residuals for the Parametric Studies window.

The residual plot shown in figure 1-7 appears.

The residuals give us an idea of the convergence

of the solution.
http://-/?-http://-/?-


18/20



4. Post-Process the Results Using CFD-VIEW

Figure 1-7. Residual Plotter

Close the residual plotter by selecting Close

under the plotters File menu.

Start CFD-VIEW.

To import a DTF file select Import DTF or

PLOT 3D from the File menu, browse to locate

backstep.00001.DTF, and click Accept.


19/20



From the Visualization panel select U from

the Primary Variable pull-down menu then click

the Surface On icon.

The contours of x-direction velocity are dis-

played.

Figure 1-8. Model Display in CFD-VIEW

To View the next model, select New

Model under the File menu then import the

file named backstep.00001.DTF.

Repeat the above step for all three DTF files

created during the parametric study.


20/20



5. This tutorial is now finished.

From the Windows menu, select Tile Horizon-

tally to view the three models in one screen as

shown in figure 1-8.

The variation of step dimensions and inlet veloc-

ity is evident in the velocity contour plots.
http://-/?-http://-/?-

simman tut 01 backstep

Documents