SIMLAB CFD For ACUSOLVE, Day 1 PDF

© Altair Engineering Inc. Proprietary and Confidential. All rights reserved. SIMLAB CFD FOR ACUSOLVE, DAY 1  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Agenda Day 1...

© Altair Engineering Inc. Proprietary and Confidential. All rights reserved. SIMLAB CFD FOR ACUSOLVE, DAY 1  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Agenda Day 1 Day 2 Introduction to CFD Workshop 5: Blower Steady State CFD theoretical background Moving Reference Frame (MRF) Turbulence modelling Using Groups Workshop 1: Manifold Flow Simulation Workshop 6: Blower Transient CFD complete workflow for simple manifold flow Mesh motion Comparing results side-by-side Workshop 2: Mixing Elbow - Steady State CHT Solid/Fluid meshing for Conjugate Heat Transfer Workshop 7: Heat Transfer in Headlamp Mesh Controls Natural Convection Thermal radiation modelling Workshop 3: Mixing Elbow - Transient Frozen Flow​ Boussinesq approximation Mapping results from another solution Animation Extraction Workshop 4: Mixing Elbow - Thermal FSI​ Setting up one-way coupled simulation  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. INTRODUCTION TO CFD  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Fluid Mechanics Definition Fluid mechanics is the branch of physics that studies fluids (liquids, gases, plasmas) and the forces acting on them. FLUID MECHANICS “Fluid” : a substance that deforms “Mechanics” : the branch of applied mathematics continuously when acted on by a that deals with both stationary and moving bodies shearing stress of any magnitude under the influence of forces Statics Dynamics ΣF = 0 ΣF ≠ 0  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Flow Solution Approaches Fluid Flow can be studied in three ways: Analytical Experimental Numerical Approach Approach Approach Theoretical Experimental CFD: Computational Fluid Dynamics Fluid Dynamics Fluid Dynamics  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Analytical Approach Overview Analytical Solution can be obtained by resolving the mathematical equations governing the physics of phenomena under study. A general solution for all physical problems is an insurmountable task because of the complexity of the equations This approach is feasible in some simple flow cases with certain approximations in geometry, dimensionality and compressibility of the flow. Examples of such flows are Couette flow, Hagen – Poiseuille flow, Convergent – Divergent Nozzle 𝑣 = 𝑣0 𝑣 = 𝑣0  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Experimental Approach Overview Experimental Solution can be obtained by the study of a prototype of a device in an appropriate test facility. Measurement of fluid properties (i.e., temperature & pressure) using measuring equipment. Hot wire anemometry measuring the rapidly varying velocities at a point Pitot tubes, mass flow meters, etc. Flow visualization techniques to understand the fluid behavior. Surface flow visualization with colored oil. Particle tracer methods (i.e., smoke, laser light)  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Numerical Approach Overview Numerical Solution can be obtained with the help of digital computers by producing quantitative predictions of fluid-flow phenomena based on the conservation laws (mass, momentum & energy) governing fluid motion. Fluid region of interest is divided into finite regions Complex governing equations are discretized to obtain a set of algebraic equations that are advanced in time and space using computers. End result of the CFD analysis is a complete description of the fluid flow within the region of interest. 𝑎11 ⋯ 𝑎1𝑛 𝑥1 𝑏1 ⋮ ⋱ ⋮ ⋮ = ⋮ 𝑎𝑚1 ⋯ 𝑎𝑚𝑛 𝑥𝑚 𝑏𝑚  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Advantages Overview Evaluation of performance before modifying or installing a system. Detailed information of the variables on the complete domain. Possibility to have variety of post-processing giving deeper insight of results. Costs much less than experiments with lesser turn-around times. Simulation of dangerous / too expensive scenarios that cannot be carried out in experimental tests.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Advantages Simulation Driven Design Concept Design Physical Prototype Experiment Final Product Redesign Virtual CFD Final Concept Design Prototype Simulation Product Cost and time savings Redesign  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Generic Process Overview Model Preparation: Mesh Setup and Meshing: Convert geometries to watertight volumes Define mesh settings for surface and volume appropriate for CFD analysis meshing Simulation Setup: Run meshing Select physics models, material properties, body Solver Run, Monitoring and Post forces, heat sources Processing: Assign boundary conditions Run CFD simulation Monitor while running Post process results after simulation is finished Solver Run, Mesh Model Simulation Monitoring Setup and Preparation Setup and Post Meshing Processing  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. PHYSICS - GOVERNING EQUATIONS  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Physics Governing Equations Governing equations for an incompressible, viscous, heat conducting fluid. Transport of three conserved quantities for a local system: mass, momentum and energy. Equations can be derived either for a fluid particle that is moving with the flow (Lagrangian) or for a fluid element that is stationary in space (Eulerian). Fluid flows are usually described in the Eulerian perspective wherein fluid's quantities are studied at a fixed point in space as time processes. The Lagrangian approach is widely used in solid mechanics, focusing on the motion of each individual particle. Lagrangian Eulerian Pathline Fluid streamlines Particle Control Volume  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Governing Equations Overview Analysis of any physical problem, in general, is governed by a set of basic governing equations. Basic equations governing the motion of fluids are the Navier-Stokes Equations (developed 150 years ago). 𝜕𝜌 Continuity Equation: + 𝛻 ⋅ (𝜌𝑼) = 0 𝜕𝑡 Set of coupled partial 𝜕𝑼 differential equations Momentum Equation: 𝜌 + 𝜌𝑼 ⋅ 𝛻 𝑼 = −𝛻𝑝 + 𝜌𝑏 + 𝜇𝛻 2 𝐔 𝜕𝑡 𝐷𝑇 𝐷𝑝 Describe the relation Energy Equation: 𝜌 𝑐𝑝 = + 𝛻 ⋅ 𝑘𝛻𝑇 + 𝛻𝑼 ⋅ 𝝉 + 𝑆 among the flow 𝐷𝑡 𝐷𝑡 properties like pressure, temperature, velocity  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Governing Equations Momentum Equation 𝜕𝑼 𝜌 + 𝜌𝑼 ⋅ 𝛻 𝑼 = −𝛻𝑝 + 𝜌𝑏 + 𝜇𝛻 2 𝐔 I: Local change in momentum with time 𝜕𝑡 II: Momentum Convection I II III IV V III: Surface force IV: External (Source) force V: Molecular dependent momentum exchange (diffusion)  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Governing Equations Energy Equation Temperature (for a calorically perfect gas) 𝐷𝑇 𝐷𝑝 𝜌 𝑐𝑝 = + 𝛻 ⋅ 𝑘𝛻𝑇 + 𝛻𝑼 ⋅ 𝝉 + S I: Change in energy of the fluid particle in motion 𝐷𝑡 𝐷𝑡 II: Pressure work I II III IV V III: Heat flux IV: Irreversible transfer of mechanical energy into heat V: Energy sources (potential, reactions, etc.)  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. TURBULENCE - PHYSICS OF TURBULENCE  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Turbulence Definition Definition: Pope, S.B., 2000, “Turbulent Flows” “An essential feature of turbulent flows is that the fluid velocity field varies significantly and irregularly in both position and time.” Turbulent Flows in our everyday lives Rivers, ocean currents, cyclones, bush fires Flows over bodies (cars, aircrafts, buildings, etc.) Internal flows in pipelines, turbines and engines  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Turbulence Characteristics of Turbulence Irregularity Non-repetition Three-dimensional, unsteady eddies with different scales Energy Diffusivity injection Dissipation and energy cascade Amplification of flow disturbances Property of the flow, not a fluid Energy property cascade Sensitivity to flow disturbances Energy dissipation  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Turbulence Reynolds Number inertial force 𝜌𝑢𝐿 Re = = viscous force 𝜇 Where: ρ → Fluid density (kg/m3) u → Flow velocity (m/s) L → Characteristic length (m) μ → Dynamics viscosity of the fluid (kg/m-s) Useful for the characterization of the flow patterns (laminar or turbulent flow) and the determination of dynamic similitude between two different flow cases.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Turbulence Critical Reynolds Number The critical Reynolds Number (Recr) at which the flow changes from laminar to turbulent. For pipe flow, 2300 < Recr_d < 4000, where Recr_d based on the pipe diameter For flow over a flat plate, Recr_x ~ 500000, where Recr_x based on the distance from the leading edge For an obstacle in cross flow, Recr_d ~ 20000, where Recr_d based on the obstacle diameter  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Turbulent Flow vs. Laminar Flow Comparison Laminar Flow At low Reynolds number → inertial force < viscous force Turbulent Layered velocity vectors Transition Turbulent Flow At high Reynolds number → Inertial force > viscous force Irregular flow patterns Laminar Mixing due to chaotic eddies  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Turbulence Challenges in Simulating Turbulent Flows Three-dimensional time-dependent flow Irregular and chaotic nature Non-repetitive Vast range of length and time scales Length scale reduction with increasing Reynolds Number Sensitive to boundary and initial conditions  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. TURBULENCE - MODELING OF TURBULENCE  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Modeling of Turbulence Methods Comparison  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. RANS Reynolds Decomposition Instantaneous velocity decomposed into the time-averaged component and fluctuating component 𝑢𝑖 = 𝑢ഥ𝑖 + 𝑢𝑖′ 𝑢𝑖 : instantaneous velocity 1 𝑡+∆𝑡 𝑢ഥ𝑖 = ∆𝑡 ‫𝑡׬‬ 𝑢𝑖 𝑑𝑡 : time-averaged velocity over ∆𝑡 ′ 𝑢𝑖 : velocity fluctuation Time-averaging velocity fluctuations: The time average of fluctuating one 𝑢ഥ𝑖′ = 0 The time average of variance 𝑢𝑖′ 𝑢𝑖′ ≠ 0 Time history of the velocity Reynolds decomposition for derivation of the Reynolds-Averaged Navier-Stokes equation.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. RANS Reynolds-Averaged Navier-Stokes (RANS) Equation 𝜕𝑢 𝑇𝑒𝑛𝑠𝑜𝑟 𝑁𝑜𝑡𝑎𝑡𝑖𝑜𝑛 𝜕𝑢𝑖 𝜕𝑢𝑖 𝜕𝑝 𝜕 2 𝑢𝑖 𝜌 + ∇ ⋅ 𝑼 ⋅ 𝑼 = −∇𝑃 + 𝜌𝒈 + 𝜇∇2 𝑼 𝜌 + 𝑢𝑗 =− + 𝜌𝑔𝑖 + 𝜇 𝜕𝑡 𝜕𝑡 𝜕𝑥𝑗 𝜕𝑥𝑖 𝜕𝑥𝑖 𝜕𝑥𝑗 𝜕𝑢𝑖 𝑢𝑗 ′ ′ 𝜕𝑢𝑖 𝜕𝑢𝑖 𝜕𝑝 𝜕 2 𝑢𝑖 𝑅𝑒𝑦𝑛𝑜𝑙𝑑𝑠 𝐷𝑒𝑐𝑜𝑚𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝜕𝑢ത 𝑖 𝜕𝑢ത 𝑖 𝜕𝑝 𝜕 2 𝑢ത 𝑖 𝜌 + 𝑢𝑗 =− + 𝜌𝑔𝑖 + 𝜇 𝜌 + 𝑢ത𝑗 =− + 𝜌𝑔𝑖 + 𝜇 −𝜌 𝜕𝑡 𝜕𝑥𝑗 𝜕𝑥𝑖 𝜕𝑥𝑖 𝜕𝑥𝑗 𝜕𝑡 𝜕𝑥𝑗 𝜕𝑥𝑖 𝜕𝑥𝑖 𝜕𝑥𝑗 𝜕𝑥𝑗 𝑢′2 𝑢′ 𝑣 ′ 𝑢′ 𝑤 ′ Reynolds Stress Tensor : 𝝉𝒊𝒋 = −𝜌𝑢𝑖′ 𝑢𝑗′ = 𝑣 ′ 𝑢′ 𝑣 ′2 𝑣 ′𝑤 ′ 𝑤 ′ 𝑢′ 𝑤 ′𝑣 ′ 𝑤 ′2 The Reynolds stresses are unknowns introduced by the Reynolds-averaging procedure. Turbulence models are needed for these stresses to close the governing equations.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. RANS General Form of Turbulence Models 𝜕 𝜌𝜙 𝜕 𝜌𝑢ത𝑗 𝜙 𝜕 𝜇𝑡 𝜕𝜙 + = 𝜇+ + 𝑃 ด𝜙 + 𝐷 ด𝜙 𝜕𝑡 𝜕𝑥𝑗 𝜕𝑥𝑗 𝜎 𝜕𝑥𝑗 Unsteady term Production term Dissipation term Convection term Diffusion term Where 𝜙 → turbulent variables Unsteady term: time-dependence of turbulent variables Convective term: rate of change of turbulent variables due to convection by the mean flow Diffusion term: transport of turbulent variables due to the summation of material viscosity and eddy viscosity Production term: production rate of turbulent variable from the mean flow gradient Dissipation term: dissipation rate of turbulent variable due to viscous stresses  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. RANS Turbulence models Comments Low computing costs because of 1-equation No need for length scale calculation for local shear layer thickness Spalart-Allmaras Natural incorporation of near wall effects Good for flows with mild separation Bad for free shear flows and flows with strong separation Widely-used turbulence models for industrial applications k-ε Needs wall functions or near wall damping term for near-wall region Poor performance for flows with strong separation and large pressure gradient, and swirling flows High accuracy for the predictions of the spreading rate of both planar and round jets Realizable k-ε Suitable for flows involving rotation, boundary layers under adverse pressure gradient, separation and recirculation Natural incorporation of near wall effects k-ω Superior performance for wall-boundary flows and free shear flows compared to k-ε Sensitive to the initial condition and inlet condition Not sensitive to the inlet condition like k-ω Shear Stress Similar performance as k-ω and thus well suited as a general-purpose model Transport (SST) k-ω Good for flows with adverse pressure gradient and separation Bad for complex 3-D flows with strong streamline curvature, swirl and rotation 37  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Near-wall Turbulence Law of the Wall The law of the wall is a semi-empirical expression relating velocity to distance from the wall in a turbulent wall-bounded flow. Turbulence near that boundary is a function only of the flow conditions pertaining at that wall and is independent of the flow conditions further away. After dimensional analysis, the law of the wall is derived: 𝑈 𝜌𝑢𝜏 𝑦 𝜏𝑤 𝑢+ = =𝑓 = 𝑓 𝑦+ , 𝑢𝜏 = 𝑢𝜏 𝜇 𝜌 𝑢+ dimensionless velocity 𝑈, mean velocity 𝑢𝜏 , friction velocity 𝜏𝑤 , shear stress near wall 𝑦 + , dimensionless wall distance 𝑦, wall distance  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Near-wall Turbulence Y+ Y+ is the nondimensionalized distance from the wall It represents the ratio between turbulent and laminar effects within a computational cell. It is often used in computational fluid mechanics modelling as a criterion for selecting the density of the mesh near the solid boundaries, i.e. the first layer height of the boundary layer mesh.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Near-wall Turbulence Boundary Layer Regions 1) Viscous/Laminar sublayer (𝑦 + < 5) Turbulent eddying motion stops very close to the wall because of the no-slip condition. Viscous shear stresses dominate this flow region. 𝑢+ = 𝑦 + 1) Buffer Layer(5 < 𝑦 + < 30) A transitional zone between the laminar and logarithmic sublayers in which velocity gradients are high but the flow is strongly turbulent. Complex velocity profile 2) Logarithmic Layer (30 < 𝑦 + < 300) 1 1 𝑢+ = 𝑙𝑛 𝑦 + + 𝐵 = 𝑙 𝑛 𝐸𝑦 + 𝜅 𝜅  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Near-wall Turbulence Boundary Layer Resolving Approaches An appropriate computational mesh in the near-wall region must be constructed to ensure the correct resolution of the flow phenomena within the boundary layer. 1) Full boundary layer resolution Large number of cells to capture steep near-wall gradients Center of the first cell ~y+=1 2) Wall function Empirical non-linear relationships used to interpret the physics of flow near walls. The center of the first cell must be placed in the region of the logarithmic law y+>30  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. NUMERICAL METHODS  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. FEM (AcuSolve) vs FVM (Legacy Codes) Comparison FVM FEM Surface based discretization Volume based discretization Each surface has uniform physical values Each surface has linear physical values (velocity, (velocity, pressure etc.) pressure etc.) Hence requires relatively fine mesh for capturing steep gradients  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. FEM (AcuSolve) vs FVM (Legacy Codes) Comparison FEM has rich expression powers at near wall Wall velocity = 0 can never be satisfied with FVM. Wall velocity = 0 can always be satisfied with FEM. Real FVM FEM  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. FEM (AcuSolve) vs FVM (Legacy Codes) Comparison FEM has rich expression powers between interfaces Moving interface and fixed interface velocities cannot be satisfied with FVM. Continuities can always be satisfied with FEM. Real FEM  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. WORKSHOP 1: MANIFOLD FLOW SIMULATION  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Workshop 1: Manifold Flow Simulation Problem Description: This tutorial introduces to the workflow for setting up a Computational Fluid Dynamics (CFD) analysis using Altair SimLab The model consists of a manifold pipe, analogous to an inlet manifold of an engine Ideally in an inlet manifold used in an engine, the manifold design is such that it ensures near-equal distribution of flow among all passages  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Simulation Workflow Import CAD Meshing Setup Solution Results 50  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. SOLUTION SETUP  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Import Manifold_Fluid.xmt_txt Open Database 52  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 2D Mesh 53  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Ignore BL on inlet and outlets 3D Mesh 54  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select the arrow and move it -130mm 3 2 Mesh Inspection 1 55  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Verify element size don’t harshly change from one to another Mesh Inspection 56  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Select Fluid Mesh 2 Create Fluid Solution 57  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 3 Set Normal velocity: 2m/s Change Units to 1 MKS Assign Inlet 58  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Create a separate Outlet boundary 1 condition for each face 2 Assign Outlet 59  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. If no material shows 2 3 up, you can load it from the database 1 Assign Material 60  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. RUN SOLUTION  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Save as Flow_Solution Save Database 62  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Run Solution 63  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Once the solution 2 starts you can visualize the log file 1 View Solver Log 64  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Simulation Convergence 65  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 First select Plot None on Residual Ratio then Plot All on Solution Ratio Final Simulation Convergence 66  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. POST-PROCESSING  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Multiphysics Post-Processing 68  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Velocity Results 69  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select the arrow and 3 move it -0.13m 2 Velocity Results 1 70  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set the view on the XY plane and hide moving tools 2 1 Velocity Results 71  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Velocity Vector Results 72  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select “Cut layer” to visualize the vectors Velocity Vector Results 73  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Change to Pressure Pressure Results 74  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select Contour Pressure Results 75  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Hide the edges by selecting “Face Edges” Pressure Results 76  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. MORE ABOUT CFD VOLUME MESHING  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. B.L. CFD Volume Meshing CFD Mesh tool is used to generate the boundary layers (B.L.) from TET Mesh the fluid wall faces and TET elements for the interior of the bodies. Input to CFD mesh are surface mesh bodies. Fluid bodies: Select the surface mesh bodies that will be modeled as fluids. B.L. mesh will be generated on the faces of these bodies. Ignore BL creation on faces: Select faces of fluid bodies on which B.L. generation needs to be ignored. Example: Inlets, Outlets do not require a B.L. Solid bodies: Select bodies to generate TET mesh. The bodies modeled as solids in the simulation does not require the boundary layer. Note: Refer to SimLab 2022.3 Help > Mesh > 3D Mesh to get more details!  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Volume Meshing Boundary Layer Parameters Constant: Constant thickness for the entire first layer of the B.L. Chosen based on desired Y+. Usually aiming for Y+ = 100. Fraction of Surface Mesh Size: First layer height equals the local surface mesh element size multiplied by the given factor. Useful when surface mesh size varies significantly. Common choice is 0.1. Total Number of Layers: Common choice for many Acusolve applications is 5-8 Layers. Note: Refer to SimLab 2022.3 Help > Mesh > 3D Mesh to get more details!  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Volume Meshing Boundary Layer Parameters 𝒉𝒊 𝒉 Growth rate = 𝒉𝒊+𝟏 𝒉𝒊+𝟏 𝒊 Recommended range: 1.2-1.3 Growth Method: Constant: This will determine boundary layer growth based on a constant ratio such as growth rate. Variable: This will be used to define the growth of BL beyond certain number of layers. An initial growth rate and number of layers with initial growth rate must be defined. Match Outer Layer: First few layers from the wall grow based on growth rate and remaining layers will be adjusted such that the final BL size matches with the core volume mesh size. Note: Refer to SimLab 2022.3 Help > Mesh > 3D Mesh to get more details!  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Volume Meshing Tet Core: Settings of the TET mesh of the inner domain – outside the B.L. Internal Grading: Growth rate from one Tet element to another. Recomennded range: 1.2 – 1.3 Note: Refer to SimLab 2022.3 Help > Mesh > 3D Mesh to get more details!  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. CFD Volume Meshing B.L. Element type: Prism or Tetra. Prism offer greater accuracy especially for thermal applications. Tetra offer faster mesh generation and run times. Note: Refer to SimLab 2022.3 Help > Mesh > 3D Mesh to get more details!  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. WORKSHOP 2: MIXING ELBOW STEADY STATE CHT  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Workshop 2 – Mixing Elbow Steady State CHT Problem Description Outflow This is a typical industrial example of a mixing pipe Water is entering from two inlets of a steel pipe Hot water is entering from the small inlet and cold water is entering from the large inlet. This is a Conjugate Heat transfer (CHT) simulation, i.e. heat transfer is modeled in both the fluid(water) and the solid(pipe). Small Inlet Large Inlet 1.2 m/s 0.4 m/s T = 320 K T = 295 K 84  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Simulation Workflow Import CAD Create Fluid Domain Meshing Setup Solution Results 85  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. GEOMETRY SETUP  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 4 3 Import MixingElbow.x_b with following attributes Enable MMKS 1 Units Import CAD 87  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Use Measure tool to verify overall 2 dimension Dimension Check 88  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Use Radius Measure to verify an essential dimension 2 Dimension Check 89  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Set: Name: Flow_Steady Solution type: Steady State Enable Heat Transfer Create Flow Solution 90  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Select any inner face as wetted face Fluid Domain 91  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select all bodies 1 2 Combine Bodies 95  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Save file with different names after each important section Save 96  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. MESHING  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 3 Using Cylindrical face 4 select one face of the small inlet and set Radius to 25si Region Mesh Control 98  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Select circular face of the region and then the arrow 3 Select vertex 2 Select snap to vertex Region Mesh Control 99  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set Average element size: 2mm 100 Region Mesh Control  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 2D Mesh 101  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 You can create multiple meshes in different assemblies 2 3 Multiple Mesh 102  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Use body with 2 surface mesh of 6mm 1 Transfer Control Mesh 103  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Set: From bodies: Elbow CAD To bodies: Elbow Mesh They need to be visible to be selected Transfer Control Mesh 104  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 Newly created control mesh for the FEM body 1 Verify Transfer 105  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Unmerge Bodies 106  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Select both inlet 3 faces from solid body Change Layers 107  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Set: Numbers of tet layers: 3 2 Volume Layer Mesh Control 108  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set: 1 Average element 2 size: 2mm Quality 1: Stretch 3 3D Solid Mesh 109  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Ignore BL on inlets and outlet 3D Fluid Mesh 110  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Verify element size don’t harshly change from one to another 3 1 Mesh Inspection 2 111  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Change Specification 2 to CFD 1 112 3 Save as Elbow_Mesh Mesh Inspection  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. SOLUTION SETUP  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 Open Flow_Steady 3 1 Change Units to MKS 114 Edit Solution  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Set: Average velocity: 0.4m/s Temperature: 295K Select Large Inlet face 115 Assign Boundary Condition: Inlet  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Select Small Inlet face Set: Average velocity: 1.2m/s Temperature: 320K Assign BC: Inlet 116  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Select Outlet face Assign BC: Outlet 117  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Select all the outer faces of the Elbow Solid 3 Set: Name: Outer_Wall Type: Convection Heat transfer coefficient: 100 W/(m^2*K) Reference temperature: 302.6 K Assign BC: Wall 118 with Convection  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Under Fluid load Water 2 Under Solid load Steel Load Materials 119  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Select Elbow_Fluid 2 Assign Water 120  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. You can also assign a material by using the 1 drop-down menu 2 Save as Elbow_Solution Assign Steel 121  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. RUN SOLUTION  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Run Solution 123  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Once the solution 2 starts you can visualize the log file 1 View Solver Log 124  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Check Simulation Convergence 125  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 First select Plot None on Residual Ratio then Plot All on Solution Ratio Check Simulation Convergence 126  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. MORE ABOUT RESIDUAL AND SOLUTION RATIOS  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Converged Residual & Solution Ratios Residual ratio What is the residual ratio? The residual measures the local imbalance of a conserved variable (velocity, pressure etc). Thus, it is a measure of how accurately we solve the Navier-Stokes equations. An Acusolve simulation is considered as converged when: ✓ Pressure,Velocity & Temperature Residual ratios fall below 1e-3. Diverged ✓ Turbulence Variables Residual ratios fall below 1e-2. In most applications Acusolve manages to converge within the first 50 timesteps. Acusolve default maximum timesteps for Steady-State: 100 timesteps. If Residual ratios exhibit large values and do not converge boundary conditions and meshing are the first things to review.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Converged Residual & Solution Ratios Solution ratio What is the Solution ratio? Solution ratio is the ratio of the solution increment to solution field of the previous timestep. Thus, it gives us an indication of how much are the field variables change from timestep to timestep. An Acusolve simulation is considered as converged when both Residual & Solution ratios fall below the convergence tolerance: Diverged ✓ Pressure,Velocity & Temperature Solution ratios below 1e-2. ✓ Turbulence Variables Residual ratios below 1e-1. If Solution ratios exhibit large values and do not converge boundary conditions and meshing are the first things to review.  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. POST-PROCESSING  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Post-Processing 131  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Temperature Results Results 132  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Cut on the “Z” plane 2 1 Cutting Plane 133  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select the icon to hide the move tools 1 2 Cutting Plane 134  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Velocity Results Results 135  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Set Plot to Vector Select cut layer to only 2 visualize vectors Cutting Plane - Vector 136  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Set Number of 3 seeds: 100 4 Create Rake Select Large 2 Inlet Face Streamlines 137  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set Number of 2 seeds: 50 3 Create Rake Select Small 1 Inlet Face Streamlines 138  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Create Streamlines for both rakes Streamlines 139  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 You can change the color of Elbow_Fluid and hide Elbow to better visualize the streamlines 1 Streamlines 140  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Uncheck the rakes to hide the streamlines Streamlines 141  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. WORKSHOP 3: MIXING ELBOW TRANSIENT CHT  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Workshop 3 – Mixing Elbow Transient CHT Problem Description Outflow The same model as Workshop 2 is considered. Water is now entering with variable temperature from the two inlets. Since the water temperature at the inlets is variable in time, a transient simulation will be needed. The flow solution of the steady-state simulation of Workshop 1 will be used as initial conditions. Frozen Flow: The flow solver is disabled and Acusolve is solving only for heat transfer. Large Inlet Small Inlet 0.4 m/s 1.2 m/s Variable Temperature Variable Temperature  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Simulation Workflow Edit Steady-State CFD Solution Results 144  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Hide Results 145  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Duplicate Solution 146  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Change Analysis Type 147  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Open Flow_Steady_copy Set: Name: Flow_Transient Time step size: 0.1s Final time: 5s Edit Solution 148  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 Define Inlet Temp 3 Set: 1 Open Small_Inlet Multiplier Function Name: Multiplier_Small_Inlet Type: Piecewise Linear 4 Edit Small Inlet 149  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 Create the small inlet multiplier curve 150 Import the csv table located in Input_Files Edit Small Inlet  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Define Inlet Temp 3 Set: 1 Open Large_Inlet 2 Multiplier Name: Multiplier_Large_Inlet Function Type: Piecewise Linear 4 151 Edit Large Inlet  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Create the large inlet multiplier curve Import the csv table located in Input_Files Edit Inlet 152 mp_large_inlet.csv  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set Initial conditions for Temperature, Velocity, Pressure and Eddy Viscosity from Flow_Steady Define Initial Conditions 153  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Set Flow: False 2 Set Turbulence: False Flow is frozen – solve for Temperature only Edit Solver Settings: 154 Frozen Flow  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 Set Number of Processors 1 depending on availability Edit Execute Settings 155  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Set: Output frequency: 1 3 Save as Elbow_Transient Edit Result Settings 156  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Run Solution 157  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Open Log File 158  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Under Surface Output plot temperature for Large and 2 Small Inlet 1 159 Verify Temperature on Inlet  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Under Surface Output plot temperature for Outlet 160 Plot Temperature on Outlet  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Results 161  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Cut on the “Z” plane and align view on XY 2 plane 3 1 Results 162  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set: Max Temp: 320K Min Temp: 240K Lock on Set limits 163  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 164 Play Animation  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Set the recording settings, then record and save the video Export Animation 165 1 2  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. WORKSHOP 4: THERMAL FSI MIXING ELBOW  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Workshop 4 – Thermal FSI Mixing Elbow Problem Description The aim of this workshop is to exhibit the simplicity of setting up a Multiphysics simulation in Simlab. The mixing elbow model from workshop 2 & 3 will be employed. Temperature and Pressure loads are mapped from the CFD simulation of Workshop 2 on the structural mesh. This is a one-way coupled simulation Pressure Temperature  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Simulation Workflow Setup Structural Solution Results 168  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Hide Results 169  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Hide Fluid and only select Elbow 1 2 Create Solution 170  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select one bolt hole using cylinder selection 1 2 Create Constraints 171  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Create Constraints 172  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 Enable all 2 constraints Create Constraints 173  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Select one inner face Pressure Mapping 174  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 1 Pressure Mapping 175  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 1 2 To return to original model after mapping> >Hide Results Pressure Mapping 176  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Temperature Mapping 177  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. To return to original model after mapping> >Hide Contour Review Mapping 178  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. 2 Set Checkel to No 1 3 Save as Elbow_FSI Solver Settings 179  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Run Solution 180  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Stress Results 181  © Altair Engineering Inc. Proprietary and Confidential. All rights reserved. Displacement Results 182 THANK YOU altair.com #ONLYFORWARD DISCOVER CONTINUOUSLY. ADVANCE INFINITELY. 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