Introductory FLUENT Training-Centrifugal Pump

Introduction

The Purpose of the tutorial is to model fluid flow in a centrifugal pump, which involves the use of rotation model.

Problem consists of a five blade centrifugal pump operating at 2160 rpm. The working fluid is water and flow is assumed to be steady and incompressible.

Due to rotational periodicity a single blade passage will be modeled.

Starting Fluent in Workbench

1. Open the Workbench (Start > Programs > ANSYS 12.0 > ANSYS Workbench)
2. Drag FLUENT into the project schematic
3. Change the name to Duct
4. Double click on Setup
5. Choose 3D and Double Precision under Options and retain the other default settings

Import Mesh

This starts a new Fluent session and the first step is to import the mesh that has already been created:

1. Under the File menu select Import> Mesh
2. Select the file tfa-pump-lite-cav-300k.msh and click OK to import the mesh
3. After reading the mesh, check the grid using Mesh>Check option

or by using Check under Problem Setup>General

Setting up the Models

1. Select Pressure Based, Steady state solver Problem Setup>General>Solver
2. Specify Turbulence model

Problem Setup > Models > Viscous

Double click and Select k-epsilon (2 eqn) under Model and Realizable under k-epsilon model and retain the default settings for the other parameters

1. Make sure that the Energy Equation is disabled

Problem Setup > Models> Energy

Materials

Define the materials.

Problem Setup > Materials

1. Click on air to open Create/Edit Materials panel
2. Change Name to water and Density and Viscosity to 1000 kg/m3 and 0.001 kg/(m-s) respectively
3. Click on Change/Create
4. Click on Yes, on being asked for Change/Create mixture and Overwrite air

Fluid Zone Conditions

Under Problem Setup >Cell Zone Conditions (operating conditions are also in BC panel) double click on Fluid

– Select Material Name : water

– Select Motion Type: Moving Reference Frame

– Specify Rotational Velocity : 2160 rpm

– Click on OK

Operating Conditions

Under Problem Setup >Cell Zone Conditions (operating conditions are also in BC panel)

Click on Operating Conditions… and set the Operating Pressure (Pascal) to 0

Boundary Conditions

Under Problem Setup > Boundary Conditions

1. Select inlet under Zone and choose velocity-inlet from the drop down menu under Type
2. Now double click on inlet under Zone

Input all the parameters in Momentum tab as shown below

Under Problem Setup > Boundary Conditions

1. Select outlet under Zone and choose pressure-outlet from the drop down menu under Type
2. Now double click on outlet under Zone

Input all the parameters in Momentum tab as shown below

http://www.cadfamily.com/html/Article/Introductory%20FLUENT%20Training-Centrifugal%20Pump_890_1.htm

http://www.cadfamily.com/html/Article/Introductory%20FLUENT%20Training-Centrifugal%20Pump_890_2.htm

Modeling of Catalytic Convertor

Introduction

-A workshop to demonstrate how to model porous media in FLUENT

-Workshop models a catalytic convertor. Nitrogen flows in though inlet with an uniform velocity 22.6 m/s, passes through a ceramic monolith substrate with square shaped channels, and then exits through the outlet.

-Substrate is impermeable in Y and Z directions, which is modeled by specifying loss coefficients 3 order higher than in X direction

 

Starting Fluent in Workbench

1. Open the Workbench (Start > Programs > ANSYS 12.0 > ANSYS Workbench)
2. Drag FLUENT into the project schematic
3. Change the name to Catalytic
4. Double click on Setup
5. Choose 3D and Double Precision under Options and retain the other default settings

Import Mesh

This starts a new Fluent session and the first step is to import the mesh that has already been created:

1. Under the File menu select Import> Mesh
2. Select the file catalytic_converter_125k.msh.gz and click OK to import the mesh
3. After reading the mesh, check the grid using Mesh>Check option

or by using Check under Problem Setup>General

Setting up the Models

1. Select Pressure Based, Steady state solver Problem Setup>General>Solver
2. Specify Turbulence model

Problem Setup > Models > Viscous

Double click and select k-epsilon (2 eqn) under Model and Realizable under k-epsilon model and retain the default settings for the other parameters

1. Make sure that the Energy Equation is disabled

Problem Setup > Models> Energy

Materials

Define the materials.

Problem Setup > Materials

1. Click on air to open Create/Edit Materials panel
2. Click on FLUENT Database…> Select nitrogen(n2) from the list > Copy
3. Click on Change/Create

Fluid Zone Conditions

Under Problem Setup >Cell Zone >Double click on part-in under Zone

– Select Material Name : nitrogen

– Default values for other settings

– Click to OK

Similarly, visit to part-out Zone and select the same settings as above

 

Fluid Zone Conditions (2)

Under Problem Setup ->Cell Zone ->Double click on part-catalyst under Zone

– Select Material Name : nitrogen

– Select and click on Porous Zone

– Under Direction-1 Vector, specify as: 1, 0, 0

– Under Direction-2 Vector, specify as: 0, 1, 0

– Specify as per GUI under Viscous Resistance and Inertia Resistance

– Default values under Power law Model and Porosity

http://www.cadfamily.com/html/Article/Modeling%20of%20Catalytic%20Convertor_891_1.htm

http://www.cadfamily.com/html/Article/Modeling%20of%20Catalytic%20Convertor_891_2.htm

Introductory FLUENT Training-Tank Flushing

Introduction

-In this workshop, you will model the filling and emptying of a water tank. The transient problem is solved as a multiphase (air/water) simulation using the volume of fluid (VOF) multiphase model.

-An initial water level is set in the tank. The water supply is turned on for the first second of the simulation and then shut off for the rest of the simulation. The water level rises until water flows out the U-tube generating a siphoning effect which effectively empties the tank.

Mesh Import

Start a new 3D FLUENT session

Read or import the mesh file tankflush.msh.gz

Click General in the outline tree.

– Scale the mesh to units of centimeters.

– Set View Length Unit In to cm to have FLUENT display lengths in centimeters.

– Verify the domain extents:
–11.1 < x < 20 cm
–19.8 < y < 27.9 cm
0 < z < 1 cm

– Set the working units
of length to centimeters.

– Check the mesh.

– Display the mesh.

Define Simulation Type

In the General panel, under Solver, set Time to Transient.

Enable Gravity and set Gravitational Acceleration to –9.81 m/s2 in the y direction.

Enable Turbulence Model

1. Activate Models in the outline tree.

– Double-click Viscous-Laminar in the central pane under Models.

– In the Viscous Model panel, select k-epsilon (2 eqn).

– Under k-epsilon model, select Realizable.

– Retain defaults for all other settings.

– Click OK.

VOF Multiphase Model Setup

Enable the VOF multiphase model.

– Activate Models in the outline tree.

– Double-click on Multiphase.

– In the panel that opens, enable Volume of Fluid.

– Set Number of Eulerian Phases to 2.

– Ensure that Scheme is set to Explicit.

– Enable Implicit Body Force

– Click OK.

Define the materials.

– Activate Materials in the outline tree.

– Click Create/Edit…

– In the Materials panel, click FLUENT Database…

– Select water-liquid from the FLUENT Fluid Materials list, click Copy and then click Close.

Phases

Define the phases.

– Activate Phases in the outline tree.

– Double-click phase1-Primary Phase.

– In the Primary Phase panel, change the Name to water.

– Ensure that air is selected under Phase Material.

– Click OK.

– Double-click phase2-Secondary Phase.

– In the Secondary Phase panel, change the Name to air.

– Select water-liquid under Phase Material.

– Click OK.

Multiphase Model Setup

Define phase interactions

– Click the Interaction button.

– In the Phase Interaction panel that opens, activate the Surface Tension
tab.

– Select constant in the pull-down list and enter 0.072 N/m for the Surface Tension Coefficient. Click OK.

http://www.cadfamily.com/html/Article/Introductory%20FLUENT%20Training-Tank%20Flushing_892_1.htm

http://www.cadfamily.com/html/Article/Introductory%20FLUENT%20Training-Tank%20Flushing_892_2.htm

http://www.cadfamily.com/html/Article/Introductory%20FLUENT%20Training-Tank%20Flushing_892_3.htm

Transonic Flow over a NACA 0012 Airfoil Part B

Case Check

Check the case file and make sure there are no reported issues.

– Use Run Calculation > Check Case

– Any potential problems with the case setup will be raised in the case check panel if there are no problems this panel will not appear. In this case there is a recommendation to check the reference values for the force monitors. Since we have already set these we can ignore this warning.

Save the case file.

– File > Save Project (if running under workbench)

Run Calculation

-Although the calculation is ready to compute, It is good practice (but not strictly necessary) to run the FMG and then check the coarse FMG solution before starting the main calculation iterations.

-Set the number of requested iterations to zero, and press ‘Calculate’.

-Check the pressure and velocity contours to make sure that no spurious values are predicted.

-Go to ‘Graphics and Animations in the LHS tree, choose ‘Contours’ and ‘Set Up’

-Choose Contours of Pressure > Static Pressure and ‘Filled’

-Display. If you need to autoscale the display press <control> A

-Zoom in as required.

-Examine the min and max reported values.

-Repeat for Contours of Velocity> Mach Number.

-There are no spurious results from the FMG, so proceed to the main calculation.

-Return to ‘Run Calculation’ in the LHS tree.

-Change the number of windows to three (for the residual, drag and lift monitors that we set up earlier).

-Request 900 iterations.

-‘Calculate’

After 900 iterations the calculation has fully converged.

– Note that the CFL has been updated during the calculation in a number of stages, ramping up from 5 to 200 as we requested. This can be seen in the CFL window and the effect on the residuals is also evident. By the end of the calculation the residuals have converged well and are no longer changing. The drag and lift monitors are also stable.

Post Processing [FLUENT]

Select ‘Graphics and Animations’ in the LHS menu

Examine the contours of static pressure.

– Turn off ‘Filled’ to just display the contour lines.

– Adjust the Levels to increase the number of contour lines.

The contour will display in the active window (click a window to activate). Alternatively, use the drop down menu to return the display to a single window as shown here

Plot contours of Velocity > Mach Number and notice that the flow is now locally supersonic.

Select ‘Plots’ in the LHS menu.

Plot Pressure Coefficient along the top and bottom airfoil surfaces.

Compare experimental pressure coefficient plots which we can import and plot here alongside the numerical prediction.

Click on ‘Load File’ and browse for the files in your directory.

Once loaded, plot the CFD and experimental Cp plots together.

A good agreement can be seen.

http://www.cadfamily.com/html/Article/Transonic%20Flow%20over%20a%20NACA%200012%20Airfoil%20Part%20B_885_1.htm

Electronics Cooling with Natural Convection and Radiation Part B

Comments on Solver controls

-The solver settings are tuned for an overall robust solution of most situations. In this model we require the Body Force Weighted pressure scheme to account for the natural convection effects.

-Once the solution has begun to (or has) converge the momentum and energy equations should be switched to second order to improve the accuracy of the solution. You may wish to do this later if time permits.

-The momentum within the model is relatively low so reducing the momentum under-relaxation factor is also recommended.

-Solution initialization is used to provide the first guess prior to the first solver iteration; and it should be as close to the final solution as practical.

Quick post-processing

Check overall heat and mass balances.

– Reports > Fluxes > Set Up

– Select the Inlet and Outlet surfaces, then click Compute.

The net imbalance mass flux is shown under Net Results.

Note that the net imbalance is very small.

– Switch to Total Heat Transfer Rate. Select all walls, the inlet, and the outlet and click Compute.

Note that the difference roughly equals the energy source input to the package (75W).

If the model were fully converged, this value would be exact.

 

Create a user-defined surface:

– Create a surface in the midplane of the channel (x = 0) for post-processing:

(From top menu bar) Surface > Isosurface

Select Mesh and X-coordinate

Leave iso-value at x=0 m

Specify the name (zz-x-midplane).

Ensure that no items are selected under From Surface and/or From Zones.

Click Create.

Create Contour plot:

(Graphics and Animations > Contours > Setup)

-Select the user surface zz-x-midplane

-Check Filled

-Select contours of Temperature…Static Temperature

-Select Display

-Zoom in with the mouse to see the result

-Repeat changing the plot variable to Velocity…Velocity Magnitude

-Optional step:

– To change the number format use

Display > Colormap from the top menu, and change to float

Save Case and Data Files for Later Use

The purpose of the Workbench structure is to simplify the file structure, and reduce the risk of stray files on the hard drive.

Part of this workshop is to allow the comparison of the results both with and without radiation active. To retain this set of results use the top menu to:

– If using FLUENT standalone

File àWrite à Case & Data…

– If using FLUENT under Workbench

File àExport à Case & Data…

– Change to the working directory and label the
file logically

TIP

– Adding the .gz extension will compress the case and data files, reducing hard
disk usage!

– You do not need to uncompress the files when opening them later.

Setup Radiation Model

The temperature difference across the air space is minimal, and therefore heat transfer via thermal radiation may be significant.

Go to the Models tree item and select radiation.

– Enable the Surface-to-Surface (S2S) model.

Set Partial Enclosure temperature to 45 °C

– Click the Set button to define model parameters.

Manual Options

100 Faces Per Cluster

Apply to All Walls

Ray Tracing

OK

In the Radiation model panel Compute/Write the
S2S calculation. Enter a filename. (Calculating the view factors will take a few minutes).

Click OK when the S2S view factor calculation is complete.

Comments on S2S Radiation model

The model uses a ray tracing method, and this calculation is completed prior to the main solution. Thus whist the set-up may take slightly longer (due to view factor calculation time) than the alternatives the overall solution time is reduced.

The method determines the view factor from each wall (or boundary) surface facet (mesh cell) to every other facet. Clustering is then used to reduce the number of facet calculations needed in the actual solution. Here neighbouring facets are grouped together based on the number set and geometric factors.

The User documentation contains full details of the model.

Revise Boundary Conditions

-The surfaces surrounding the fluid region now also require an emissivity value for the radiation model.

-Open the wall_left boundary condition and under the thermal tab change the Internal Emissivity to 0.9.

-Click the Copy button and copy the boundary conditions to wall_right and wall_top.

http://www.cadfamily.com/html/Article/Electronics%20Cooling%20with%20Natural%20Convection%20and%20Radiation%20Part%20B_887_1.htm

Electronics Cooling with Natural Convection and Radiation Part A

Goals

In this workshop, you will model the heat dissipation from a hot electronics component fitted to a printed circuit board (PCB) via a finned heat sink.

The PCB is fitted into an enclosure which is open at the top and bottom.

Initially only the heat transfer via convection and conduction will be calculated. The effect of thermal radiation will then be included as a later stage.

Mesh Import (Workbench)

This workshop can be done either inside or outside of ANSYS Workbench.
If working outside of Workbench, you should skip this page.

Open a new Workbench session and select a new FLUENT session from Component Systems

Use Save As to save the session.

Import the the mesh file.

– Right-click on the Setup cell.

– Change Files of Type to Fluent
Mesh File

– Select the mesh file heatsink.msh

– Click Open.

Launch FLUENT using the default options.

Mesh Import (Stand-alone)

Start a 3D FLUENT session from the icon or from the Windows Start menu

Select either

– File ? Read ? Mesh from the top
menu

– Open File icon from toolbar

Open the file heatsink.msh

Check the grid to verify that there are no errors in the mesh.

View the model:

Display the mesh and color the faces by ID:

– Select Graphics and Animations

– Highlight Mesh, then Setup just below

Set Faces to on, and Edges to Feature

Deselect all currently selected faces

Select Surface Types Wall, Pressure Outlet and Velocity Inlet (note effect on Surfaces list)

Select Colors and Color by ID.

Display

– Select the Lights button, and turn on headlight.

– Make the outer walls transparent

Use Scene button

Select wall_left, wall_right and wall_top

Select Display and set transparency to roughly 50

Apply and close Display Property panel

Apply and close Scene Description panel

– Redisplay the image (Use Setup and Display buttons as above)

Model setup

1. Display the mesh and adjust the display settings.

a) Highlight Mesh and click Setup.

i. Select Feature and Edges. Set Edge Type to Feature.

ii. Deselect all currently selected faces

iii. Select Surface Types Wall, Pressure Outlet and Velocity Inlet (note effect on Surfaces list)

iv. Select Colors and Color by ID.

v. Click Display

1. Change temperature units to °C Define ? Units

1. Select Temperature as a Quantity
2. Select c as the temperature units.
3. Close the panel.

3. Enable the energy equation.

a.Select the Models tree item

b.Double-click on Energy and enable the equation.

Comments on Model setup

General

– It is good practice to display the grid after import to check for any boundary zone misassignment and that you have opened the correct model.

– Workbench uses SI units (meters, kg etc) but if importing a mesh from another source check the scale and dimensions are correct.

– Check mesh is used to confirm the mesh is suitable for use in a CFD simulation.

– Report Quality is a backup to the quality tools available within the meshing application.

By default the energy equation is not solved to reduce CPU load because many problems are isothermal. In this case, temperature must be calculated so the energy equation needs to be enabled.

The onset of turbulence is specified by the Reynolds Number (pipe flow) or Rayleigh Number (natural convection). Calculating these numbers using boundary conditions indicates that the flow will be laminar.

Material properties

The air density needs to change with temperature (but not pressure)

– Select Materials à Air à Create/Edit

– Change density to incompressible
ideal gas

– All other properties remain unchanged

– Click Change / Create then close the fluid materials window.

Define two additional solid materials (for the board and the heat sink).

– Select Materials à Solid à Create/Edit

– Click the FLUENT Database button.

– Change Type to Solid

– Select Copper

– Copy then close the database window

Modify the copper material to produce two different materials.

– The PCB is made of material Fr-4.

Change Name to fr-4

Delete the chemical formula

All other properties remain unchanged

Click Change/Create.

Click No when prompted to overwrite copper.

– Selecting No will create a new material Fr-4, but copper remains in the material list.

– Selecting Yes will overwrite the copper material for the current case only.

http://www.cadfamily.com/html/Article/Electronics%20Cooling%20with%20Natural%20Convection%20and%20Radiation%20Part%20A_886_1.htm