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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Introduction

The purpose of this tutorial is to demonstrate the setup of a dense discrete phase model(DDPM) with the example of 2D riser. DDPM is used for the secondary phase that has aparticle size distribution.

This tutorial demonstrates how to do the following:

Use Eulerian multiphase model.

Set up and use DDPM.

Solve the case using appropriate solver settings.

Postprocess the resulting data.

Prerequisites

This tutorial is written with the assumption that you have completed Tutorial 1 fromANSYS FLUENT 13.0 Tutorial Guide, and that you are familiar with the ANSYS FLUENTnavigation pane and menu structure. Some steps in the setup and solution procedure willnot be shown explicitly.

In this tutorial, you will use the Eulerian multiphase model and discrete phase model. Fordetails about these models, see Sections 26.5 and 25.2 for Setting Up the Eulerian Modeland Steps for Using the Discrete Phase Modelsrespectively in ANSYS FLUENT13.0 UsersGuide.

Assuming that you are using a quad core single processor machine with a clock speed of 3.80

GHz, this tutorial will take approximately 25 hours for the calculation.

Problem Description

A vertical riser has an air inlet at bottom. Particles are injected from a side at some heightclose to the inlet. The schematic of the setup is as shown in Figure 1.

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Figure 1: Schematic

Setup and Solution

Preparation

1. Copy the files (riser.msh.gz) to your working folder.

2. Use FLUENT Launcher to start the 2DDP version ofANSYS FLUENT.

For more information aboutFLUENT Launcher see Section1.1.2, StartingANSYS FLUENT Using FLUENT Launcher inANSYS FLUENT 13.0 Users Guide.

Step 1: Mesh

1. Read the mesh file (riser.msh).

File Read Mesh...

As the mesh file is read, ANSYS FLUENT will report the progress in the console.

Step 2: General Settings

1. Define the solver settings.

General Transient

2. Enable Gravityand enter -9.81 m/s2 for Y.

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

3. Check the mesh (see Figure2).

General Check

ANSYS FLUENT will perform various checks on the mesh and will report the progressin the console. Make sure the minimum volume reported is a positive number.

Figure 2: Mesh Display

Step 3: Models

1. Select the Eulerian multiphase model.

Models Multiphase Edit...

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

(a) SelectEulerian from the Model list.

(b) Enable Dense Discrete Phase Model.

(c) Click OK to close Multiphase Model dialog box.

2. Define the discrete phase model.Models Discrete Phase Edit...

(a) Ensure thatUpdate DPM Sources Every Flow Iteration is enabled.

(b) Enter 100forNumber of Continuous Phase Iterations per DPM Iteration.

(c) SelectSyamlal-OBrien from the Drag Law drop-down list.

(d) Ensure that Unsteady Particle Tracking and Track with Fluid Flow Time Step areenabled.

(e) Click Numerics tab.

i. Disable Accuracy Control in the Options group box.

ii. Select implicit from the Tracking Scheme drop-down list.

(f) Click OK to close the Discrete Phase Modeldialog box.

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Step 4: Injections

Set the injection, solids-backfeed.

Models Discrete Phase Edit...

1. Click onInjections... and click Create to open Set Injection Properties dialog box.

(a) Entersolids-backfeed for Injection Name.

(b) Selectgroupfrom the Injection Type drop-down list.

(c) Enter 20for the Number of Particle Streams.

(d) Selectrosin-rammler from the Diameter Distribution drop-down list.

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

(e) Enter the values forFirst Point as shown in the following table:

Parameter Value

X-Position (m) -0.0999

Y-Position (m) -0.95

X-Velocity(m) 1

Stop Time (s) 1000

Total Flow Rate (kg/s) 0.4

Min. Diameter (m) 9e-05

Max. Diameter (m) 0.00016

Mean Diameter (m) 0.00013

Spread Parameter 9.6

(f) Enter the values forLast Point as shown in the following table:

Parameter Value

X-Position (m) -0.0999

Y-Position (m) -0.95

X-Velocity(m) 1

(g) Selectphase-2 from the Discrete Phase Domain drop-down list.

(h) Click OK to close Set Injection Properties dialog box.

2. Close Injections dialog box.

3. Click OKto close Discrete Phase Modeldialog box.

Step 5: Materials

Set the properties for anthracite.

Materials anthracite Create/Edit...

1. Enter 2400 kg/m3 forDensity.

2. Click Change/Create and close Create/Edit Materials dialog box.

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Step 6: Phases

1. Define the primary (gas) phase.

Phases phase-1-Primary Phase Edit...

(a) Enter gasforName.

(b) Selectair from the Phase Material drop-down list.

(c) Click OK to close the Primary Phase dialog box.

2. Define the secondary (solids) phase.

Phases phase-2-Secondary Phase Edit...

(a) Enter solids for the Name.

(b) EnableGranular.

(c) Selectgidaspowfrom the Granular Viscosity drop-down list.

(d) Selectlun-et-al from the Granular Bulk Viscosity drop-down list.

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

(e) Click OK to close Discrete Phase dialog box.

Step 7: Boundary Conditions

1. Set the boundary conditions at theinlet.

Boundary Conditions inlet

(a) Selectgas from the Phase drop-down list and clickEdit....

i. Enter 1.1m/s for Velocity Magnitude.

ii. Retain the other default settings.

iii. Click OKto close the Velocity Inlet dialog box.

(b) Select solids from the Phase drop-down list and clickEdit....

i. Ensure that Granular Temperature is 0.0001m2/s2.

ii. Click OKto close the Velocity Inlet dialog box.

2. Set the boundary conditions at theoutlet.

Boundary Conditions outlet

(a) Selectmixture from the Phase drop-down list and click Edit....

i. Click Momentumtab and ensure that Gauge Pressure is 0pascal.

ii. Click DPM tab and ensure that escape is selected from Discrete Phase BCType drop-down list.

iii. Click OKto close the Pressure Outletdialog box.

(b) Select solids from the Phase drop-down list and clickEdit....

i. Ensure that Backflow Granular Temperature is 0.0001m2/s2.

ii. Click OKto close the Pressure Outletdialog box.

Step 8: Solution

1. Set the under-relaxation factors.

Solution Controls

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

(a) Enter 0.7 for Pressure and 0.3 for Momentum in the Under-Relaxation Factorsgroup box.

2. Initialize the solution.

Solution Initialization

3. Enable autosaving of the data file after every 6000 time steps.

Calculation Activities

(a) Enter 6000for Autosave Every (Time Steps).

(b) Click Edit... to open Autosave dialog box.

i. Enter an appropriate file name (riser.gz).

ii. Click OKto close the Autosave dialog box.

4. Start the calculation.

Run Calculation

(a) Enter 0.001 for Time Step Size.

(b) Enter 30000 for Number of Time Steps.

(c) EnableData Sampling for Time Statistics.

(d) Set theReporting Interval to 5.

(e) Click Calculate.

5. Save the case and data files (riser-final.cas.gz).

Step 9: Postprocessing

1. Display filled contours of mean volume fraction.

Graphics and Animations Contours Set Up...

(a) EnableFilled in the Options group box.

(b) SelectUnsteady Statistics... from the Contours ofdrop-down list.

(c) Selectsolidsfrom thePhasedrop-down list and then select Mean Volume fractionfrom the Contours ofdrop-down list.

(d) Click Display(see Figure3).

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Figure 3: Contours of Mean Volume Fraction of Solid Phase

2. Display filled contours of mean velocity magnitude.

Graphics and Animations Contours Set Up...

(a) SelectUnsteady Statistics... from the Contours ofdrop-down list.

(b) Selectsolidsfrom thePhasedrop-down list and then select Mean Velocity Magni-tudefrom the Contours ofdrop-down list.

(c) Click Display(see Figure4).

Figure 4: Contours of Mean Velocity Magnitude of Solid Phase

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Figure 5: Current Particle Positions Colored by Particle Diameter

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Tutorial: Riser Simulation Using Dense Discrete Phase Model

Summary

This tutorial demonstrated the use of DDPM model to simulate a riser.

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