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 a particle 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 from ANSYS FLUENT 14.0 Tutorial Guide, and that you are familiar with the ANSYS FLUENT navigation pane and menu structure. Some steps in the setup and solution procedure will not be shown explicitly. In this tutorial, you will use the Eulerian multiphase model and discrete phase model. For details about these models, see Sections 26.5 and 25.2 for Setting Up the Eulerian Model and Steps for Using the Discrete Phase Models respectively in ANSYS FLUENT 14.0 User s Guide. 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 height close to the inlet. The schematic of the setup is as shown in Figure 1. c ANSYS, Inc. March 7, 2012 1
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 of ANSYS FLUENT. For more information about FLUENT Launcher see Section 1.1.2, Starting ANSYS FLUENT Using FLUENT Launcher in ANSYS FLUENT 14.0 User s 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 Gravity and enter -9.81 m/s 2 for Y. 2 c ANSYS, Inc. March 7, 2012
3. Check the mesh (see Figure 2). General Check ANSYS FLUENT will perform various checks on the mesh and will report the progress in 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... (a) Select Eulerian from the Model list. (b) Enable Dense Discrete Phase Model. (c) Click OK to close Multiphase Model dialog box. c ANSYS, Inc. March 7, 2012 3
2. Define the discrete phase model. Models Discrete Phase Edit... (a) Ensure that Update DPM Sources Every Flow Iteration is enabled. (b) Enter 100 for Number of Continuous Phase Iterations per DPM Iteration. (c) Select Syamlal-OBrien from the Drag Law drop-down list. (d) Ensure that Unsteady Particle Tracking and Track with Fluid Flow Time Step are enabled. 4 c ANSYS, Inc. March 7, 2012
(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 Model dialog box. c ANSYS, Inc. March 7, 2012 5
Step 4: Injections Set the injection, solids-backfeed. Models Discrete Phase Edit... 1. Click on Injections... and click Create to open Set Injection Properties dialog box. (a) Enter solids-backfeed for Injection Name. (b) Select group from the Injection Type drop-down list. (c) Enter 20 for the Number of Particle Streams. (d) Select rosin-rammler from the Diameter Distribution drop-down list. 6 c ANSYS, Inc. March 7, 2012
(e) Enter the values for First 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 for Last Point as shown in the following table: Parameter Value X-Position (m) -0.0999 Y-Position (m) -0.95 X-Velocity (m) 1 (g) Select phase-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 OK to close Discrete Phase Model dialog box. Step 5: Materials Set the properties for anthracite. Materials anthracite Create/Edit... 1. Enter 2400 kg/m 3 for Density. 2. Click Change/Create and close Create/Edit Materials dialog box. c ANSYS, Inc. March 7, 2012 7
Step 6: Phases 1. Define the primary (gas) phase. Phases phase-1-primary Phase Edit... (a) Enter gas for Name. (b) Select air 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) Enable Granular. (c) Select gidaspow from the Granular Viscosity drop-down list. (d) Select lun-et-al from the Granular Bulk Viscosity drop-down list. (e) Click OK to close Discrete Phase dialog box. 8 c ANSYS, Inc. March 7, 2012
Step 7: Boundary Conditions 1. Set the boundary conditions at the inlet. Boundary Conditions inlet (a) Select gas from the Phase drop-down list and click Edit... c ANSYS, Inc. March 7, 2012 9
i. Enter 1.1 m/s for Velocity Magnitude. ii. Retain the other default settings. iii. Click OK to close the Velocity Inlet dialog box. (b) Select solids from the Phase drop-down list and click Edit... i. Ensure that Granular Temperature is 0.0001 m 2 /s 2. ii. Click OK to close the Velocity Inlet dialog box. 2. Set the boundary conditions at the outlet. Boundary Conditions outlet (a) Select mixture from the Phase drop-down list and click Edit... i. Click Momentum tab and ensure that Gauge Pressure is 0 pascal. ii. Click DPM tab and ensure that escape is selected from Discrete Phase BC Type drop-down list. iii. Click OK to close the Pressure Outlet dialog box. (b) Select solids from the Phase drop-down list and click Edit... Step 8: Solution i. Ensure that Backflow Granular Temperature is 0.0001 m 2 /s 2. ii. Click OK to close the Pressure Outlet dialog box. 1. Set the under-relaxation factors. Solution Controls (a) Enter 0.7 for Pressure and 0.3 for Momentum in the Under-Relaxation Factors group box. 10 c ANSYS, Inc. March 7, 2012
2. Initialize the solution. Solution Initialization 3. Enable autosaving of the data file after every 6000 time steps. Calculation Activities (a) Enter 6000 for Autosave Every (Time Steps). (b) Click Edit... to open Autosave dialog box. i. Enter an appropriate file name (riser.gz). ii. Click OK to 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) Enable Data Sampling for Time Statistics. (d) Set the Reporting 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) Enable Filled in the Options group box. (b) Select Unsteady Statistics... from the Contours of drop-down list. (c) Select solids from the Phase drop-down list and then select Mean Volume fraction from the Contours of drop-down list. (d) Click Display (see Figure 3). c ANSYS, Inc. March 7, 2012 11
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) Select Unsteady Statistics... from the Contours of drop-down list. (b) Select solids from the Phase drop-down list and then select Mean Velocity Magnitude from the Contours of drop-down list. (c) Click Display (see Figure 4). Figure 4: Contours of Mean Velocity Magnitude of Solid Phase 12 c ANSYS, Inc. March 7, 2012
3. Display the particle tracks colored by diameter. Graphics and Animations Particle Tracks Set Up... (a) Retain the default selection of point from the Style drop-down list. (b) Select Particle Variables... and Particle Diameter from the Color by drop-down list. (c) Select solids-backfeed from the Release from Injections list. (d) Click Display (see Figure 5). c ANSYS, Inc. March 7, 2012 13
Figure 5: Current Particle Positions Colored by Particle Diameter Summary This tutorial demonstrated the use of DDPM model to simulate a riser. 14 c ANSYS, Inc. March 7, 2012