tut 08 supersonic wing

CFX-5 Tutorials 87

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CFX-5 Tutorials

Tutorial 8

Supersonic Flow Over aWing

Sample files used in this tutorial can be copied to your workingdirectory from <CFXROOT>/examples. See Working Directory (p. 2)and Sample Files (p. 3) for more information.

Sample files referenced by this tutorial include:

• WingSPS.pre

• WingSPSMesh.out

Supersonic Flow Over a Wing—Introduction

Page 188 CFX-5 Tutorials


8.A: Introduction

8.A.1: Features explored in this tutorial

Introduction: This tutorial addresses the following features of CFX-5.

You learn about:

• setting up a supersonic flow simulation

• using the Shear Stress Transport turbulence model to accurately resolveflow around the wing surface

• defining custom vector variables for use in visualising pressuredistribution

Component Feature Details

CFX-Pre User Mode Quick Setup Wizard

Simulation Type Steady State

Fluid Type Ideal Gas

Domain Type Single Domain

Turbulence Model Shear Stress Transport

Heat Transfer Total Energy

Boundary Conditions Inlet (Supersonic)

Outlet (Supersonic)

Symmetry Plane

Wall: No-Slip

Wall: Adiabatic

Wall: Free-Slip

Domain Interfaces Fluid-Fluid (No FrameChange)

Timestep Auto Timescale

CFX-Solver Manager n/a n/a

CFX-Post Plots Contour

Default Locator

Vector

Other Variable Editor

Supersonic Flow Over a Wing—Introduction

CFX-5 Tutorials Page 189


8.A.2: Before beginning this tutorial

Introduction: It is necessary that you have a working directory and thatsample files have been copied to that directory. This procedure is detailedin "Introduction to the CFX-5 Tutorials" on page 1.

Unless you review the introductory materials and perform required stepsincluding setting up a working directory and copying related sample files,the rest of this tutorial may not work correctly. It is recommended that youperform the tasks in Tutorial 1, Tutorial 2 and Tutorial 3 before working withother tutorials as these three tutorials detail specific procedures that aresimplified in subsequent tutorials.

8.A.3: Overview of the problem to solve

This example demonstrates the use of CFX-5 in simulating supersonic flowover a symmetric NACA0012 airfoil at 0o angle of attack. A 2D section of thewing is modelled. A 2D hexahedral mesh is provided that is imported intoCFX-Pre.

air speedu= 600 m/s

wing surface

outlet

70 [m]

30 [m]

1.25 [m]

Supersonic Flow Over a Wing—Defining the Simulation in CFX-Pre



8.B: Defining the Simulation in CFX-Pre

This section describes the step-by-step definition of the flow physics inCFX-Pre. If you wish, you can use the session file Wing.pre to completethis section for you and continue from Obtaining a Solution (p. 196). Thissession file sets up the model to produce an initial guess. See one of the firstfour tutorials for instructions on how to do this.

8.B.1: Creating a New Simulation

1. Start CFX-Pre and create a new simulation named Wing using the

General Mode.

8.B.2: Importing the Mesh

Tip: While we provide a mesh to use with this tutorial, you may want todevelop your own in the future. Instructions on how to create this meshin CFX-Mesh are available from the CFX Community Site. Please see"Mesh Generation" on page 3 for details.

1. Copy the mesh file WingSPSMesh.out, located in the examples

directory (<CFXROOT>/examples), to your working directory.

2. Click the Mesh tab to access the Mesh workspace.

3. Right-click in the Mesh Selector and select Import.

4. In the Mesh Workspace, on the Definition panel, set:

a. Mesh Format to PATRAN Neutral

b. File to WingSPSMesh.out

5. Click OK to import the mesh.

The mesh will appear in the viewer.

6. Click Isometric View (Y up) from the Viewer toolbar.

8.B.3: Creating the Domain

Creating a newdomain

1. Click Domain .

2. Enter Wing in the Name box and click OK.




3. On the General Options panel:

a. Set Location to Assembly, Assembly 2 and Assembly 3.(Use the <Ctrl> key to select more than one region.)

b. Leave Domain Type set to Fluid Domain.

c. Set Fluids List to Air Ideal Gas.

d. Leave Coord Frame set to Coord 0.

e. Set Ref. Pressure to 1 [atm].When using an Ideal Gas, it is important to set an appropriatereference pressure since some properties depend on the absolutepressure level. See "Setting a Reference Pressure" on page 10 in thedocument "CFX-5 Solver Modelling" for details.

f. Under Buoyancy, leave Option set to Non Buoyant.

g. Under Domain Motion leave Option set to Stationary.

4. Click the Fluid Models tab.

a. Under Heat Transfer Model, set Option to Total Energy.The Total Energy model is appropriate for high speed flows since itincludes kinetic energy effects.

b. Under Turbulence Model, set Option to Shear Stress Transport.

c. Set Turbulent Wall Functions to Automatic.

d. Leave Reaction or Combustion Model and Thermal RadiationModel set to None.

The Initialisation panel sets domain specific initial conditions, which are notused in this tutorial. Global initialisation will be set later in the tutorial.

5. Click OK to create the domain.

8.B.4: Creating the Boundary Conditions

Creating theInlet BoundaryCondition

1. Create a boundary condition named Inlet.

2. On the Basic Settings panel, set:

a. Boundary Type to Inlet

b. Location to INLET




3. Click the Boundary Details tab, then:

a. Under Flow Regime set Option to Supersonic.

b. Under Mass and Momentum set:

• Option to Cart. Vel. & Pressure

• U = 600 [m/s]

• V = 0 [m/s]

• W = 0 [m/s]

• Relative Static Pressure to 0 [Pa]

c. Under Turbulence, set Option to Intensity and Length Scale,Fractional Intensity to 0.01, and Eddy Len. Scale to 0.02 [m].

d. Under Heat Transfer, set Option to Static Temperature and StaticTemperature to 300 [K].

4. Click OK to create the boundary condition.

Creating theOutletBoundaryCondition

1. Create a boundary condition named Outlet.


a. Boundary Type to Outlet

b. Location to OUTLET

3. Click the Boundary Details tab, then, under Flow Regime set Option

to Supersonic.


Creating theRequiredSymmetryPlaneBoundaryConditions

1. Create a boundary condition named SymP1.


a. Boundary Type to Symmetry

b. Location to SIDE1


4. Create two more symmetry planes in the same way, using the names

and locations given below:

a. SymP2, at the location SIDE2.

b. Bottom, at the location BOTTOM.

Creating a FreeSlip BoundaryCondition forthe Top of theDomain

Create a free slip wall at the location TOP.




Creating aWall BoundaryCondition forthe Wing

1. Create a boundary condition named WingSurface.


a. Boundary Type to Wall

b. Location to WING

3. Click the Boundary Details tab, then:

a. Under Wall Influence On Flow, leave Option set to No Slip.

b. Under Heat Transfer, leave Option set to Adiabatic.


8.B.5: Creating Domain Interfaces

The imported mesh contains three regions which will be connected withdomain interfaces. To ensure a one-to-one connection between the threeregions, a translational periodic interface (with a zero translation in thiscase) will be created. See "One-to-one Connections" on page 127 in thedocument "CFX-5 Solver Modelling" for details.

1. Click Domain Interface .

2. Accept the default name by clicking OK.

3. Set Interface Type to Periodic.

4. Set Connection Type to Automatic.

5. Set Periodic Type to Translational.

6. For Side 1, leave Domain (Filter) set to -- All Domains --.

7. Set Region List 1 to Assembly 3D A External.


9. Set Region List 2 to Assembly 3D B External A.

10. Click OK to create the domain interface.

The second domain interface is set up in a similar way:

1. Click Domain Interface .

2. Accept the default name by clicking OK.

3. Set Interface Type to Periodic.

4. Set Connection Type to Automatic.

5. Set Periodic Type to Translational.





7. Set Region List 1 to Assembly 3D B External B.


9. Set Region List 2 to Assembly 3D C External.

10. Click OK to create the domain interface.

8.B.6: Setting Initial Values

For high speed compressible flow, the CFX-Solver usually requires sensibleinitial conditions to be set for the velocity field.

1. Click Global Initialisation from the main toolbar.

2. Leave Velocity Type set to Cartesian.

3. Under Cartesian Velocity Components, set:

a. Option to Automatic with Value

b. U = 600 [m/s]

c. V = 0 [m/s]

d. W = 0 [m/s]

4. Under Temperature, set Option to Automatic with Value and

Temperature to 300 [K].

5. Use Automatic for all other variables.

6. Turn on Turbulence Eddy Dissipation and leave Option set to

Automatic

7. Click OK to set the initialisation details.

8.B.7: Setting Solver Control

1. Click Solver Control .

2. Under Advection Scheme, set Option to High Resolution.

The residence time for the fluid is approximately:

70 [m] / 600 [m s^-1] = 0.117 [s]

In the next step, you will start with a conservative timescale that graduallyincreases towards the fluid residence time as the residuals decrease. A userspecified maximum timescale can be combined with an Auto Timescale inCFX-Pre.




3. Under Convergence Control:

a. Set Timescale Control to Auto Timescale.

b. Set Max. No. Iterations to 100.

c. Set Length Scale Option to Conservative.

d. Turn on Maximum Timescale and set Maximum Timescale to0.1[s].

4. Under Convergence Criteria, set:

a. Residual Type to RMS

b. Residual Target to 1.0e-05

5. Click OK to set the solver control parameters.

8.B.8: Writing the Solver (.def) File

1. Click Write Solver (.def) File .

2. Leave Operation set to Start Solver Manager.

3. Turn on Report Summary of Interface Connections.

4. Click OK.

Since this tutorial uses domain interfaces and the Report Summary ofInterface Connections toggle was enabled, an information window isdisplayed that informs you of the connection type used for each domaininterface; see "Connection Types" on page 127 in the document "CFX-5Solver Modelling" for details.

5. Click OK in the information window.

6. Select File > Quit.

7. Click Yes when asked if you want to save the CFX file.

Supersonic Flow Over a Wing—Obtaining a Solution



8.C: Obtaining a Solution

When CFX-Pre has shut down, and the CFX-Solver Manager has started,obtain a solution to the CFD problem by following the instructions below.

1. Click Start Run.

When it has finished:

2. Click OK.

3. When the CFX-Solver has finished, click OK in the message window.

4. Click Post-Process Results .

5. When Start CFX-Post appears, turn on Shut down Solver Manager

then click OK.

Supersonic Flow Over a Wing—Viewing the Results



8.D: Viewing the Results

The following Plots are recommended:

1. Create a Contour plot on the SymP2 boundary.

a. Set the Variable to Mach Number.

b. Use a User Specified Range with a Min of 1 and Max of 2.

c. Set the # of Contours to 21.

You will see that the bulk of the flow has a Mach number which is very closeto the maximum. The velocity goes to zero on the wing surface.

Figure 1: Mach Number on SymP2




2. Another recommended view of the results is a plot of Pressure on

SymP2, with a global range. You will be able to see that a bow wave has

formed, and the highest value of pressure is at the leading edge.

Figure 2: Pressure on SymP2

3. You can confirm that a significant energy loss occurs around the wing

leading edge by plotting Temperature on SymP2. The temperature at

the wing tip is approximately 180 K higher than the inlet temperature.

Figure 3: Temperature on SymP2




You can also try creating a user vector variable to show the pressuremagnitude and direction acting on points along the airfoil:

1. Select Create > Variable.

2. Accept the default name and click OK.

3. Turn on the Vector toggle, then enter the following expressions:

• X Expression: (Pressure+101325[Pa])*Normal X

• Y Expression: (Pressure+101325[Pa])*Normal Y

• Z Expression: (Pressure+101325[Pa])*Normal Z

4. Click Apply.

5. Click Create Vector Plot and accept the default name.

6. Set Locations to WingSurface and Variable to Variable 1.

7. Click the Symbol tab and set:

a. Symbol to Line Arrow

b. Symbol Size to 0.04

8. Click Apply.

The resulting vector plot shows the pressure acting against the surfaceof the wing.

Figure 4: Pressure acting on the Wing

When you have finished, quit CFX-Post.




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tut 08 supersonic wing

Documents

basic settings panel

boundary details tab

set interface type

set periodic type

set connection type

leave option set

click domain interface

boundary type