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ANSYS TutorialLaminar and Turbulent Flow Analysis in a 2-D Duct

This tutorial models the air flow in a two-dimensional duct.

Dimension & Properties ValueInlet Length 4 inInlet Height 1 inTransition Length 2 inOutlet Height 2.5 inInitial Outlet Length 4 inAdded Outlet Length 30 inAir Density 1.21x10 -7 lbf-s 2/in4 Air Viscosity 2.642x10 -9 lbf-s/in 2 Inlet Velocity 1 in/s (50 in/s on restart)Outlet Pressure 0 psi

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The following is the step-by-step procedure for the beam deflection problem using the ANSYS GUI(Graphic User Interface) environment. Using the left button of the mouse, click on everything that istyped bold and type everything that is italicized below.

(Go To ANSYS/Faculty Utility Menu)File

Change Jobname then type Air Flow

(GoTo Utility Menu)PlotCtrls

Numbering(Go to Keypoints and click) OFF (then OFF will be toggled to ON)(Go to Lines and click) OFF (then OFF will be toggled to ON)OK

LAMINAR FLOW ANALYSIS

(GoTo Main Menu)Preferences

Click the FLOTRAN CFD option & OK

Preprocessor Element Type

Add/Edit/DeleteAdd

FLOTRAN CFD & 2D FLOTRAN 141 & OKClose Element Type window

ModelingCreate

AreasRectangle

By Dimensions(X1, X2) 0 & 4 (Y1, Y2) 0 & 1 & Apply

By Dimensions(X1, X2) 6 & 10 (Y1, Y2) 0 & 2.5 & OK

LinesLines

Tan to 2 Lines(Pick first line) Click on Line 3 & OK (Pick tangency end of first line) Click on keypoint 3 & OK (Pick second line) Click on Line 7 & OK (Pick tangency end of second line) Click on keypoint 8 & OK

AreasArbitrary

Through KPs(Pick in counter-clockwise order) keypoints 3, 2, 5, 8 & OK

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(GoTo Utility Menu)Plot

Lines

(Ansys Main Menu)Preprocessor

MeshingMesh Tool

Click on the Lines SET button(Pick Lines 2, 4, 8, & 6) & OK

(Click the NDIV box) 10 (Click the SPACE box) -2 & Apply

(Pick Lines 1 & 3) & OK(Click the NDIV box) 15 (Click the SPACE box) -2 & Apply

(Pick Lines 9 & 10) & OK(Click the NDIV box) 12 (Click the SPACE box) 1 & Apply

(Pick Lines 5 & 7) & OK(Click the NDIV box) 15 (Click the SPACE box) 3 & Apply

Click on the Lines Flip buttonChoose the Line 7 & OK

Click on the Mapped Mesh buttonClick the Mesh Button

(Pick All) & OK

(Ansys Main Menu)Solution

LoadsDefine Loads

ApplyFluid/CFD

VelocityOn Lines

(Pick Line 4) & OK(VX) 1.0 (VY) 0.0 & OK

On Lines(Pick Lines 1, 3, 5, 7, 9, & 10) & OK

(VX) 0.0 (VY) 0.0 & OK

Pressure DOFOn Lines

(Pick Line 6) & OK(Pressure value) 0.0 (Set Endpoints) set to YES & OK

Solution

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FLOTRAN Set UpFluid Properties

Density: Choose AIR-IN Viscosity: Choose AIR-IN & OK & OK

Execution CtrlGlobal Iterations: 40 & OK

Flow EnvironmentRef Conditions

Reference Pressure: 14.7 Nominal temperature: 70 Stagnation Temperature: 70 Reference Temperature: 70 Temp offset from ABS zero: 460 & OK

Run FLOTRAN

(Ansys Main Menu)General Postproc

Read ResultsLast Set

Plot ResultsVector Plot

PredefinedChoose DOF and Velocity V & OK

Contour PlotNodal Solu

Choose Other Quantities & Total Pressure PTOT & OK

Flow TraceDefi Trace Pt

Pick 3 points around the inlet and 2 points in the recirculation region & OK

(Ansys Utility Menu)PlotCtrls

AnimateParticle Flow

Choose DOF Solution and Velocity VX & OK After viewing, click Close on the animation controller

(Ansys Main Menu)General Postproc

Path OperationsDefine Path

By NodesPick the top and bottom point along the outlet & OK Define Path Name: OUTLET & OK Close the PDEF Command Window

Map onto Path

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Label: VELOCITY Choose DOF Solution and Velocity VX & OK

Plot Path ItemOn Graph

Choose VELOCITY & OK

LAMINAR FLOW ANALYSIS - INCREASED INLET VELOCITY

(GoTo Utility Menu)Plot

Lines

(Ansys Main Menu)Solution

LoadsDefine Loads

ApplyFluid/CFD

VelocityOn Lines

(Pick Line 4) & OK(VX) 50.0 (VY) 0.0 & OK

Run FLOTRANClick OK to remove the error message.

FLOTRAN SetupRelax/Stab/Cap

MIR StabilizatioMomentum Equation: 0.1 & OK

Run FLOTRAN

Repeat the analysis steps outlined above.

LAMINAR FLOW ANALYSIS - INCREASED DUCT LENGTH

(Ansys Main Menu)Solution

LoadsDefine Loads

DeleteFluid/CFD

Pressure DOFOn Lines

Pick All

Preprocessor Modeling

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CreateAreas

RectangleBy Dimensions

(X1, X2) 10 & 40 (Y1, Y2) 0 & 2.5 & OK

Numbering CtrlsMerge Items

Choose All for Type of items to be merged & OK

(GoTo Utility Menu)Plot

Lines

(Ansys Main Menu)Preprocessor

MeshingMesh Tool

Click on the Lines SET button(Pick Lines 1 & 2) & OK

(Click the NDIV box) 10 (Click the SPACE box) -2 & Apply

(Pick Lines 11 & 13) & OK(Click the NDIV box) 20 (Click the SPACE box) 3 & OK

Click on the Lines Flip buttonChoose the Line 13 & OK

Click the Mesh Button(Pick Area 4) & OK

(GoTo Utility Menu)Plot

Lines

(Ansys Main Menu)Solution

LoadsDefine Loads

ApplyFluid/CFD

VelocityOn Lines

(Pick line 11 & 13) & OK(VX) 0.0 (VY) 0.0 & OK

Pressure DOFOn Lines

(Pick line 12) & OK(Pressure value) 0.0

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(Set Endpoints) set to YES & OK

(Ansys Utility Menu)File

FileFile Operations

DeletePick AirFlow.rfl & OK

(Ansys Main Menu)Solution

Run FLOTRAN

Repeat the analysis steps outlined above.

Calculate the Reynolds number using the velocity results.

h DV =Re

where = density = 1.21e-7; V = velocity = 50; D h = hydraulic diameter = 2*inlet height = 2; and =Viscosity = 2.642e-9.

Re = 4600, which is turbulent.

TURBULENT FLOW ANALYSIS - INCREASED DUCT LENGTH

(Ansys Main Menu)Solution

FLOTRAN Set UpSolution Options

Choose Turbulent option & OK

Execution CtrlGlobal Iterations: 80 & OK

Run FLOTRAN

Repeat the analysis steps outlined above.