ME 566 Computer Lab ANSYS–CFX Tutorial Oct. 5, 2009 2:30 – 4:30 pm Wedge E2-1302B 1

ANSYS CFX Student User Manual The manual can be downloaded from UW-ACE In the tutorial, you will be working on the Duct Bend Example (Sec. 2.2, pages 13-29) in the manual Two mesh generation methods are presented in the manual: ANSYS Mesh Generation (pages 17-19) CFX Mesh Generation (pages 27-29) You should focus on the CFX Mesh Generation method in the tutorial

Overview of ANSYS–CFX DesignModeler Create geometry CFX-Mesh Generate mesh ANSYS Workbench CFX-Pre Pre-processing CFX-Solver Solve equations CFX-Post Post-processing

ANSYS–CFX DesignModeler: CFX-Mesh: CFX-Pre: CFX-Solver: CFX-Post: Define geometry dimensions Name the faces of the solid body (e.g., inlet, outlet, wall, symmetry) CFX-Mesh: Specify mesh properties (e.g., mesh spacing, inflated boundary thickness) CFX-Pre: Specify fluid properties (e.g., density, viscosity) Set simulation type (e.g., steady) Select turbulence model (e.g., k- model, wall functions) Specify boundary conditions (e.g., speed, turbulence intensity and length scale) Select advection scheme (e.g., upwind) Define convergence criterions (e.g., number of iterations, residual target) CFX-Solver: Solve system of partial differential equations CFX-Post: Analyze results and create plots (e.g., vector plot)

Duct Bend Example 0.25 m 0.1 m 1 m 0.1 m The radius of the inner wall bend is 0.025 m The average speed of the water flow through the duct is 3 m/s 0.1 m

DesignModeler Create a solid body geometry

DesignModeler – continued Name the faces of the solid body to make it easy to apply boundary conditions In the duct bend example, six faces of the solid body are named as: Front, Back, Inflow, Outflow, InnerWall, OuterWall Back OuterWall Outflow Front InnerWall Inflow

CFX–Mesh Mesh generation methods ANSYS Mesh Generation (pp. 17-19): generates a structured mesh CFX Mesh Generation (pp. 27-29): generates an unstructured mesh You will use CFX Mesh Generation for Assignment #1 structured mesh unstructured mesh

CFX–Pre Fluid type and properties Simulation type Fluid models Type: water/air Properties: density, dynamic viscosity Simulation type Steady/transient Fluid models Turbulence model (e.g., k- model/shear stress transport model) Turbulent wall functions (e.g., scalable)

CFX–Pre continued Specify boundary conditions Advection scheme Wall: smooth/rough, stationary/translating/rotating Inlet: fluid speed/mass flow rate/pressure Outlet: fluid speed/mass flow rate/pressure Symmetry: Advection scheme Upwind/High Resolution Timescale control Auto Timescale/Physical Timescale Convergence criterions Number of iterations Residual target

CFX–Pre continued Estimation of Physical Timescale The physical timescale is calculated using approximately 30% of the average residence time for a fluid parcel to move across the flow domain (see pages 47 and 48 of the student user manual for reference). For the duct bend case Fluid travel length (average): Flow speed: Average residence time: Physical timescale: 0.125 m 0.025 m 0.25 m 0.1 m 0.1 m

CFX–Post Flow visualization and analysis of results

Physical Geometry of Duct Bend

Who Wants to Be a CFD Expert? For the given physical geometry of the duct bend, which of the following solution domain is the best choice for modeling the duct bend flow? Choice #1: Use a full physical geometry Choice #2: Use a half physical geometry Choice #3: Use a thin slice of physical geometry Choice #1 Choice #2 Choice #3 14

Solution Domain Choice #1: Full physical geometry wall wall 0.1 m 0.1 m wall wall

Solution Domain Choice #2: Half physical geometry wall 0.1 m symmetry wall 0.1 m wall

Solution Domain Choice #3: A thin slice of physical geometry wall 0.1 m symmetry symmetry 0.1 m wall