plan for today (two exercises) 1: cad, cfd, fem · numerical methods in aerodynamics lecture 3:...

Numerical Methods in Aerodynamics

Lecture 3: Exercise CAD, CFD, FEM, Indoor

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Plan for today (two exercises)

1: CAD, CFD, FEM

Fluid-Structure interaction (FSI)

http://www.ansys.com/solutions/fluid-dynamics.asp

http://www-harwell.ansys.com/demoroom/details.php?id=11,112

Create an object in SolidWorks (CAD)

Transfer the object to ANSYS Workbench

Generate a wind tunnel inclosure

Generate a fluid flow mesh

Apply boundary conditions

Apply initial conditions

Solve the flow around the object

Generate flow results

Solve the structural model

mesh, material, supports, pressure load from the fluid solution

Change the system and update the solution

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Create room with mechanical inlet

Define variables for the inlet properties

Generate a fluid mesh of the room

Apply boundary conditions

Apply initial conditions

Solve the flow in the room

Generate flow results

Change the boundary conditions

Plan for today (two exercises)

2: Indoor environmental

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Problem 1: Combining CAD, CFD and FEM

Solve the deformations due to flow pressure

Change the width of the structural element

Fixed support

Inflowsteel part

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Create object in Solidworks

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ANSYS Workbench an overview of the various parts in the

project

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Wind tunnel enclosure in DesignModeler

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Generating the mesh for the fluid flow applying boundary

conditions in CFX Pre

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Solve the fluid flow i CFX Solver

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Illustrate flow results in CFX Post

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Pressure result on boundary

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Transfer pressure from CFX to ANSYS structural solver and

solve for deformations

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Solution of structural analysis

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Change the system

Change the CAD model

Update the geometry in CFX

Update the mesh

Adopt the boundary conditions from previous simulation

Solve for pressure

Update the geometry in the FEM model

Import the updated pressure

Solve the structural system

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Problem 2: Indoor environmental solution

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Create the model

Start SolidWorks (SW)

Create a new "part"

Chose "Top plane"

press "Sketch"

press "rectangle"

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Create rectangle

Create a rectangle from the origo

press "smart dimension", click on the right and top side of the

rectangle and enter dimension=1m

press "zoom to fit"

Close the sketch and accept by clicking in the upper right corner

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Extrude

press "features" and mark the sketch, press "Extruded Boss"

Extrude 5m and accept

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Camfer the roof

Press "Features" and "Chamfer"

Chose top face of extruded shape

D=0.3m, angle = 45 degrees, accept

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Save and transfer to Workbench

Save the part as "test1"

> ANSYS 11.0 > Workbench

NB! SolidWorks should be installed first in order to have the ANSYS

menu bar. Rerun the ANSYS installation and include the Solidworks

geometry interface, if it is missing

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ANSYS Workbench

Open an empty project

Link to Active CAD Geometry

test1.SLDRT

New Geometry (This is already done if transfered directly from SW)

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DesignModeler “New Geometry”

Press "Generate" to import the

SW part

Choose Attach1 >tools>freeze

For the tunnel part not to merge

with the element

Create a wind tunnel inclosure

ZXPlane

Sketching

Make rectangle (any size)

The rectangle should have a

corner in each quadrant

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Set dimensions of the enclosure

Choose dimensions, Length/distance

L1 (positive x-direction) 20000 mm

L2 (negative x-direction) 10000 mm

L3 (positive z-direction) 10000 mm

L4 (negative z-direction) 10000 mm

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Extrude the tunnel and cut out the body Extrude FD = 10000 mm (Generate to see result)

Cut out the body to leave just the region of interest for the CFD

Choose create>Body operations

Set Type to cut material and bodies to "test1" (select in the tree view or

box select)

Generate to see result

Save and return to "project" tab

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Generate the mesh (CFX-Mesh)

Generate regions

Right-click on regions>insert>composite 2D regions

Name Inlet (YZ low x), name outlet (YZ high X), name Free (top and two sides,

use ctrl to mark several surfaces), name building is the body (choose with box

select), name wall (XZ low Y)

outlet

WallBuilding

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Setting up the mesh

Define a maximum spacing

Default body spacing, maximum

spacing = 1600mm

Finer mesh around the body

Right-click spacing>insert>Face

Spacing

Select the body, apply

Face Spacing Type: constant

Constant edge length: 200 mm

Boundary layer around body and

Right-click

inflation>insert>inflated boundary

choose body and wall (hold ctrl)

set Maximum thickness: 50 mm

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Previewing the mesh, generate the mesh

Right-click on preview>insert>Preview group

Choose Free, Wall, Body > apply

Right-click on the preview>generate this surface mesh

Click on "generate the volume mesh for the current problem"

Return to the "Project" tab

Inflation layer

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Start the Advanced CFD (CFX-pre)

Create a domain "test1"

General option:

Domain models>pressure>reference pressure : 1 atm

Fluid models:

Heat Transfer Model>option Isothermal: Fluid temperature: 25 C

Turbulence model>option: shear stress transport

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Creating the boundary conditions

Click "create boundary condition": Inlet

Basic settings

Boundary type: Inlet

Location: Inlet

Boundary details

Mass and Momentum>Normal speed: 15 m/s

Turbulence>option: Intensity and length scale

Turbulence>medium turbulence intensity

Click "create boundary condition": Outlet

Basic settings

Boundary type: Outlet

Location: Outlet

Boundary details

Mass and Momentum>Option: Static pressure

Mass and Momentum>Relative Pressure: 0 Pa

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Click "create boundary condition": Free

Basic settings

Boundary type: Wall

Location: Free

Boundary details

Wall Influence on Flow>Option: Free Slip

Click "create boundary condition": Wall

Basic settings

Boundary type: Wall

Location: Wall

Boundary details

Wall Influence on Flow>Option: No Slip

Click "create boundary condition": Building

Basic settings

Boundary type: Wall

Location: Building

Boundary details

Wall Influence on Flow>Option: No Slip

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Setting initial values, solver control, and start the solver

Click "Define the global initial conditions":

Cartesian Velocity components>option: Automatic with value

U = 15 m/s

V = 0 m/s

W = 0 m/s

Turbulence Eddy Dissipation: select

Click "Define the solver control criteria":

Convergence control

Timescale control: automatic timescale

Timescale factor: 1 s

Max. iterations: 100

Click "Write solver file":

Operation: Start solver manager

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Viewing results

Choose "CFX Post", load result (*.res file)

Creating a sample plane, click location>plane

Definition: points and normal, point (1.5, 3, -0.5), normal (1, 0, 0)

Plane bounds: rectangular (x-size=6 m, y-size=3 m)

Plane type, sample (x-sample=50, y-sample=20)

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Vector plot of velocities, etc.

Click "create vector plot"

Location: plane 1

Variable: velocity

Same approach for other planes try "contour" or "streamline"

To see pressure on body create a new contour, location: building

For an animation click "show animation editor"

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Structural analysis

Create a new project link to active CAD geometry (Part1) and press

"New simulation"

Run the structural simulation Wizard

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Export body pressure to finite element model

Stress analysis > static structural

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Structural loads

Mark the building (not the bottom)

CFX loads > CFX pressure (browse for the res-file)

Apply supports (fixed at bottom)

Right-click on solution and insert “deformation>total”

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Viewing the results

Click "total deformations"

Choose a scale factor 5xauto

Choose edges>show undeformed model

Click animation fan for animation of the result

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Change the model in SW

Double-click on the sketch

Double-click on the z-dimension

change to 2 m

Update by clicking "rebuild"

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Update the CFX-designModeler

Open the DesignModeler

Choose the attached geometry

Refresh>Using DesignModeler parameter values

Click "generate"

The new geometry is now included in the model

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Update the CFX-mesh

Click "update the geometry from its original source"

Look at the preview group (right-click and generate)

Generate a new volume mesh

save as "test2"

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Update the CFX-pre

Press the "project" tab. Choose the CFX-pre file (building.cfx)

Re-read mesh file, file to load "building2.gtm"

Click "Write solver file":

Operation: Start solver manager

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Update the CFX-post

Open the CFX-post (*.cst)

Load results (test2_001.res)

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Update and solve the finite element model

Open the structural simulation

Update the geometry

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Update and solve the finite element model

Update the pressure

choose define as>CFX Results

Correct the filename to "building_002.res"

"Solve"

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Thank you for your attention

plan for today (two exercises) 1: cad, cfd, fem · numerical methods in aerodynamics lecture 3:...

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