mulit phase 3

STAR-CCM+ User Guide Particle-Laden Flow Tutorial 4101

Version 4.04.011

Use the mouse controls to adjust the view approximately as shown below.

It can be seen that the particle impacts are concentrated on the outer radiusof the bend. In a realistic modeling exercise, a considerably larger numberof particles tracks would be needed to increase confidence in the results.

Displaying Particle Tracks

The particle tracks recorded by the Track File model will now be displayed.Start by creating a new track file.


Version 4.04.011

The particle tracks are now colored according to the velocity of the particles.

• Save the simulation.

Using Tracks In Field Functions and Derived Parts

In simulations where a large number of particle tracks are present, it is likelythat only a small number are required for plotting in a graphics scene.Plotting a reduced number of tracks can be achieved in STAR-CCM+through creating a field function to filter the available tracks andsubsequently applying the filter in a derived part.

A field function will be created that returns the Track Parcel Index numberfor every eighth track. The function name for the Track Parcel Index isTrackParcelId (which can be found from the Function Name property of theTrack: Parcel Index node in Tools > Field Functions).

• Right-click the Tools > Field Functions node and select New from the


Version 4.04.011

Summary

This tutorial introduced the following STAR-CCM+ features:

• Starting the code and creating a new simulation.

• Importing the mesh and saving the simulation.

• Plotting geometry and scalar scenes.

• Selecting models for a Lagrangian phase.

• Setting up an injector for Lagrangian Multiphase modeling.

• Defining material properties required for the selected models.

• Defining boundary conditions.

• Setting solver parameters.

• Initializing and running the solver until the residual magnitudes aresufficiently small.

• Analyzing results using the visualization facilities.

• Displaying particle tracks.

• Creating a field function and derived part based on particle tracks.

STAR-CCM+ User Guide Solid Particle Erosion Tutorial 4117

Version 4.04.011

Particle Phase

The particle loading by mass is 0.39%. The particle properties are as follows:

• Density: 2650.0 kg/m3

• Diameter: 2.75 x 10–4 m

• Initial axial velocity: 12.901 m/s

Importing the Mesh and Naming the Simulation

Start up STAR-CCM+ in a manner that is appropriate to your workingenvironment and select the New Simulation option from the menu bar.

Continue by importing the mesh and naming the simulation. Athree-dimensional polyhedral cell mesh has been prepared for this analysis.The grid has been saved in the .ccm file format which contains all therequired cell, vertex and boundary information for the problem geometry.

• Select File > Import... from the menu bar. In the Open dialog, navigate tothe doc/tutorials/multiphase subdirectory of your STAR-CCM+

Property Value Units

Fluid Density 997.561 kg/m3

Fluid Viscosity 8.8871e-4 Pa⋅s

Inlet Velocity 12.901 m/s

Turbulence Intensity 0.029

Turbulent Length Scale 0.037 m


Version 4.04.011

Setting up the Models

Several models are required in this tutorial as there is not only a turbulentcontinuous phase to consider, but also the particle motion within thecontinuous phase. Two different strategies are employed withinSTAR-CCM+ to simulate these phases. The continuous fluid phase ismodelled using an Eulerian formulation whereby fluid properties areobtained at fixed points throughout the fluid domain. The particulate phaseis modelled using a Lagrangian method where the trajectories ofrepresentative particles are tracked throughout the continuous phase.

STAR-CCM+ permits two-way coupling between the continuous fluidphase and dispersed particulate phases. For this tutorial, however, thecoupling will not be considered to reduce the amount of simulation timerequired.

Only one region for the continuous phase is required for this analysis. Bydefault, the continuum Physics 1 is automatically created when the mesh isimported. The continuum should be edited so that appropriate physicalmodels are selected for the water fluid region.

• Open the Continua node, right-click the Physics 1 node and select itemSelect models...


Version 4.04.011

Open the Physics 1 > Models node. The selected models now appear withinthat node.


Setting Lagrangian Phase Models

The Lagrangian Multiphase model requires the selection of further modelsrepresenting the characteristics of the Lagrangian phase. ThePhase Model Selection dialog will guide you through the model selectionprocess.

First the new phase must be created.

• Open the Continua > Physics 1 > Models > Lagrangian Multiphase node

• Right-click on the Lagrangian Phases node and select New from the


Version 4.04.011


Setting Material Properties

Continuous Phase

The default properties for water are acceptable for the continuous phase inthis simulation. These properties can be checked by opening the Continua >Physics 1 > Models > Liquid > H2O > Material Properties node in the object tree.

• To check the values of Density and Dynamic Viscosity, select the respectiveConstant nodes and look at the values in the Properties window.

Lagrangian Phase

Sand particles are entrained in the liquid flow in this simulation and so thedensity of the Lagrangian phase must be set to the density of sand.

• In the Continua > Physics 1 > Models > Lagrangian Multiphase >Lagrangian Phases > Phase 1 node, open the Models > Solid > Al >


Version 4.04.011

• Right-click the Al node and select Rename... from the pop-up menu.

• Change the name to Sand in the Rename dialog.

• Click OK.

Setting Lagrangian Phase Model Properties

The Drag Force Model will use the default method for the Drag Coefficient,which is the Schiller-Naumann correlation.

Quantities that should be written to the Track file are chosen as follows:


Version 4.04.011

list.

• Click Close.

Setting Lagrangian Phase Boundary Conditions

The Lagrangian Phase Boundary Conditions are used to define the behaviorof particles and droplets when they hit a solid boundary. Impact behaviorcan be defined for the following boundary types:

1. Baffle

2. Contact (interface)

3. Wall

In this simulation it is only necessary to define the boundary interactionmodels for the Wall boundary types, as there are no baffles or contactinterfaces present. It should be noted that parameters for the Erosion modelare made in this section.

• Continuing within the Physics 1 continuum, open theLagrangian Multiphase > Lagrangian Phases > Phase 1 >


Version 4.04.011

• In the Properties window, select the Oka model for the Method property.

• Select the Erosion Ratio > Oka node and review the model properties inthe Properties window.


Setting Continuous Phase Boundary Conditions

The default continuous phase boundary conditions for the wall boundariesare sufficient for this analysis, and there are no user-definable parametersfor the symmetry planes. The inlet and outlet boundaries must be modifiedas follows:

• Open the Regions > Fluid > Boundaries > Inflow > Physics Conditions node


Version 4.04.011

Turbulence Intensity > Constant node.

• In the Properties window set the Value to 0.029.

• Select the Turbulent Length Scale > Constant node.

• In the Properties window set the Value to 0.0037 m.

This completes the setting of continuous phase boundary conditions.


Setting up the Injector

The particles of the dispersed Lagrangian phase are introduced into thesolution domain using an injector. The injector defines the initial state of theparticles and their spatial distribution. In this tutorial particles will beintroduced near the inlet with a velocity matching that of the continuousphase.

A new derived part based on a presentation grid will be created to definethe injection points, as this will improve the distribution of particles acrossthe pipe section.

• Right-click the Derived Parts node and select New Part > Probe >


Version 4.04.011

set the Value to 0.027787 kg/s.

• Select the Parcel Streams node and in the Properties window set the Valueto 5.

• Select the Particle Diameter > Constant node and in the Properties windowset the Value to 2.75E-4 m.


Setting Solver Parameters and Stopping Criteria

In a Lagrangian multiphase simulation it is important to set the maximumtime for which a particle will be tracked, as it is possible for particles tobecome trapped within a fluid region (such as a stagnant zone) and remainthere indefinitely.

• Select the Solvers > Lagrangian Multiphase > Steady node.

• In the Properties window, leave the Update Frequency as 1 and set theMaximum Residence Time to 0.1 s. The Maximum Sub-Steps propertycan be left at the default value of 20000.

New stopping criteria will be created based on the monitors that appearedwhen the segregated flow solver was selected. The goal is to achieve aresidual of 1.0E-4 for the continuity and momentum quantities beforestopping the solution.

• Open the Monitors node.


Version 4.04.011

• In the Properties window set the Logical Rule property to And.

• Select the Continuity Criterion > Minimum Limit node; press and hold the<Ctrl> key; select the Minimum Limit nodes for X-momentum Criterion,Y-momentum Criterion and the Z-momentum Criterion.

• In the Properties window set the Minimum Value to 0.001.


Visualizing the Simulation

The pressure distribution on the symmetry planes will be observed as thesolution develops.


Version 4.04.011

• Set the Function property to Pressure in the Properties window.

• Use the mouse buttons to orient Scalar Scene 1 as shown below.

Reporting and Plotting Pressure Drop

Experimental measurements are available for the pressure drop across theflow restrictor when the flowrate is 28.09 liters/s. These can be compared tothe prediction of pressure drop for this simulation to give some estimate of


Version 4.04.011


Initializing and Running the Simulation

The simulation will be run in two stages. A steady state solution for the fluidphase in the absence of particles will be obtained first, and then the particletracks will be obtained with a single additional iteration. This is areasonable approach as two-way coupling has not been activated for theLagrangian phase.

Fluid Phase

• To deactivate the Lagrangian solver while the fluid phase solution isobtained, first select the Solvers > Lagrangian Multiphase node.

• Tick the Solver Frozen property within the Expert section in the Propertieswindow.

To initialize the solution and run the analysis:

• Click on the (Initialize Solution) button in the Solution toolbar or usethe Solution > Initialize Solution menu item.

• Click on the (Run) button in the Solution toolbar to run the analysis.


Version 4.04.011

• Click on the (Step) button in the Solution toolbar to perform a singleiteration. Note that it could take several minutes for the solver tocompute all the particle tracks.

• When the particle tracking is complete, save the simulation.

Visualizing the Results

The main result of interest in this tutorial is the erosion rate across therestrictor surface. A scalar scene can be created showing this profile.

• Right-click on the Scenes node and select New Scene > Scalar from thepop-up menu.

• Open the Scenes > Scalar Scene 2 node and select the Displayers >Scalar 1 > Parts node.

• Click the right half of the Parts property in the Properties window.

• In the Select Objects dialog, use the > button to move Fluid: Restrictor tothe Selected list. Click Close.

• Continuing within the same Displayers > Scalar 1 node, select the


Version 4.04.011

on the eroded restrictor surface as shown below.

The plot shows where the maximum erosion rates may be expected.

Estimating the Overall Erosion Rate

To obtain an estimate of the erosion rate in g/hr for the whole restrictor, itis necessary to create a field function that will multiply the computederosion rate in each boundary face by the face area.

• Right-click the Tools > Field Functions node and select New.

• Rename the newly created User Field Function 1 node toOverall Erosion Rate.

• In the Properties window, open the (Custom Editor) for the Dimensions


Version 4.04.011

running the report:

The predicted quantity is for a quarter annulus only: to get the full erosionrate for the real case it is necessary to multiply by 4. This gives a predictederosion rate of 0.56 g/hr for the whole component.

Comparison with Experimental Data

Pressure Drop

For flow tests conducted at a flowrate of 28.09 liters/s, the pressure dropacross the restrictor was found to be 5.44 bar. This compares favorably withthe predicted pressure drop of 5.99 bar at 28.57 liters/s obtained with therelatively coarse mesh used in this tutorial.

Erosion Rate

An erosion test for the restrictor device considered in this tutorial gave anaverage erosion rate of 0.58 g/hr over a 14 hour period. The flowrate andsand concentration used in this tutorial match those of the erosion test, andthe predicted erosion rate using the Oka model is 0.56 g/hr.

Implementing Alternative Functions for Erosion Ratio

As erosion equations are often tuned for a particular material/sandcombination it is likely that some users will wish to implement their ownmodels based on experimental testing. In this section, we will implementthe model developed by Zhang et al. [5] at the Erosion/Corrosion ResearchCentre in Tulsa as an example. The model given by Zhang et al. [5] is:

(6)

(7)

ER C BH( ) 0.59–FsV p

nF θ( )=

F θ( ) 5.40θ 10.11θ2– 10.93θ36.33θ4– 1.42θ5+ +=


Version 4.04.011

below.

With the new field function in place it is only necessary to run a singleiteration to obtain a further prediction of erosion.

• Click on the (Step) button in the Solution toolbar to perform a singleiteration. Note that this could it could take several minutes for thesolver to compute all the particle tracks.

• Run the Overall Erosion Rate report to obtain the mass loss rate from thenew result:

The erosion rate for the whole annulus is four times the predicted amount,which is 0.365 g/hr for the Zhang erosion model.

References[2] McCulloch, S., 2005. United States Patent No. US 6,886,598 B2, “Choke

Restrictor Devices and Methods”.[3] Wallace, M.S., 2001. “CFD-based erosion modelling of simple and

complex geometries.” PhD Thesis, University of Strathclyde.

STAR-CCM+ User Guide 4179

Version 4.04.011

Eulerian Multiphase Tutorial

The purpose of this tutorial is to study the acceleration of the dispersedphase due to the drag force of the continuous phase. In this case thecontinuous phase is air flowing at 5 m/s, and the dispersed phase is waterparticles flowing at 1 m/s. The geometry used in this case is shown below.

The tutorial introduces the phase interaction tool which allows the user todefine how the multiple phases interact. In this case, the particle phase isaccelerated by the drag force that is exerted by the air flow.

Importing the Mesh and Naming the Simulation

Start up STAR-CCM+ in a manner that is appropriate to your workingenvironment and select the New Simulation option from the menu bar.

Continue by importing the mesh and naming the simulation. Athree-dimensional, trimmed cell mesh has been prepared for this analysis.

• Select File > Import... from the menus

• In the Open dialog, navigate to the doc/tutorials/multiphasesubdirectory of your STAR-CCM+ installation directory and select file

Inlet Outlet

Air 99%Particles 1%

STAR-CCM+ User Guide Eulerian Multiphase Tutorial 4182

Version 4.04.011

Converting to a Two-Dimensional Mesh

We wish to carry out a two-dimensional analysis, however the importedgeometry is three-dimensional. The mesh will therefore be converted totwo-dimensions by using the Convert to 2D option. There are specialrequirements in STAR-CCM+ for three-dimensional meshes that will beconverted to two dimensions. These are:

• The grid must be aligned with the X-Y plane.

• The grid must have a boundary plane at the Z = 0 location.

The mesh imported for this tutorial was built with these requirements inmind. Had the grid not met the above conditions, it would have beennecessary to realign the region using the transformation and rotationfacilities in STAR-CCM+.

• Select Mesh > Convert to 2D....

• In the Convert Regions to 2D dialog that appears, make sure thecheckbox of the Delete 3D regions after conversion option is ticked, and


Version 4.04.011

Splitting Boundary by Angle

We will split the boundary by angle to separate the four bounding walls.These will later be defined as the pipe inlet, outlet, top and bottom.

• In the object tree, expand the Regions > Default_Fluid 2D > Boundariesnode.

• Right-click on the Default_Boundary_Region node and selectSplit By Angle....

• The Split Boundaries by Angle dialog will appear. TheDefault_Boundary_Region has already been selected, and is shown in theSelected box. Set the Angle to 90 degrees.


Version 4.04.011

When you have done this, the object tree will appear as follows:

Setting up the Physics Models

The models define the primary variables of the simulation, includingpressure, temperature, velocity, and what mathematical formulation will beused to generate the solution. In this example, a simple laminar flow is setup in which water particles are accelerated by the flow of air. We will usethe multiphase mixture option to allow us to define the two phases and thesegregated multiphase option to define how the two phases will interact.

• Expand the Continua > Physics 1 node. Right-click on the Models nodeand select Select models....

• The Physics Model Selection dialog will appear. Ensure that the


Version 4.04.011

The Physics Model Selection dialog should appear as follows when you aredone.

• Click Close.

• Save the simulation by clicking on the (Save) button.

Creating Phases and Selecting Phase Models

We will now create two new phases and specify them as air and water. Oncethe phase models have been selected we will be able to set the materialproperties for each phase.

• Expand the Continua > Physics 1 > Models > Eulerian Multiphase node.


Version 4.04.011

• In the Properties window, set the Value to 1.0 kg/m^3.

• Select the Dynamic Viscosity > Constant node and set the Value to1.0E-5 Pa-s.

• Expand the Eulerian Phases > Particle > Models > Liquid > H2O >Material Properties node.

• Using the method described previously, do the following:

• Set the Density to 2000 kg/m^3.

• Set the Dynamic Viscosity to 1.0E-5 Pa-s.

Define Phase Interaction

Using the Multiphase Interaction model we can define the interaction of theair and particle phases. The air phase will be specified as continuous, andthe particle phase as dispersed.

• Expand the Continua > Physics 1 > Models > Multiphase Interaction node.Right-click on the Phase Interactions node and select New.

• A new phase interaction node has been created, PhasePair 1. Change the


Version 4.04.011

• Finally, set the Interaction Length Scale to 5.0E-4 m.

In this tutorial we are interested in the acceleration of the dispersed particlesdue to the drag force exerted by the continuous phase. For this we will needto use the drag force multiphase interaction model with a constant dragforce value. These settings are the default for any phase interaction, so nomodifications are necessary in this case.

• To check the default settings, expand the Air-Particle > Models node. Wecan see the the selected model is Drag Force.

• Expand the Drag Force node. We can see that the Drag Coefficient is set toConstant. The default value of 0.44 is appropriate for this tutorial.

Setting Model Properties

For most cases, the default model properties will be appropriate, and it isrecommended that these are only changed by experienced users. In this casewe will change the default properties of the Multiphase Segregated Flow


Version 4.04.011

• In the Properties window, set the Value to 0.0 Pa.

Setting Boundary Conditions

Here we will set the boundary conditions for the Inlet and Outlet boundaries.First we will specify the velocity and volume fraction for each phase at theinlet. These will be set to the same values as the initial conditions in order tosatisfy the continuity constraint.

• Select the Regions > Fluid > Boundaries > Inlet node.

• In the Properties window, set the Type to Velocity Inlet.


Version 4.04.011

• Save the simulation

Setting Under-Relaxation Factors

We will specify a custom under-relaxation factor for the volume fractionsolver.

• Select the Solvers > Volume Fraction node.

• In the Properties window, set the Under-Relaxation Factor to 0.5.

Setting Stopping Criteria

The simulation will be run for 100 iterations, and we will use the maximumsteps stopping criterion to specify this.

• Select the Stopping Criteria > Maximum Steps node.


Version 4.04.011

• Select the Scalar 1 node.

• Set the Contour Style to Smooth Filled.

• Save the simulation

Running the simulation

We are ready to run the simulation.

• Click on the (Run) button in the Solution toolbar.


Version 4.04.011

• Use the mouse buttons to zoom in on the scene.

Summary

This tutorial has introduced the following STAR-CCM+ features:

• Importing the surface mesh and naming the simulation.

• Converting to a two-dimensional mesh.

• Splitting boundary by angle.

• Renaming regions, continua and boundaries.

• Setting up the physics models.

• Creating phases and selecting phase models.

• Defining phase interaction.

• Setting model properties.

• Setting initial conditons and reference values.

• Setting boundary conditions.

• Setting under-relaxation factors.

• Setting stopping criteria.

mulit phase 3

Documents