MEC2181 Mechanical Simulation - Week2.pdf

SIT Internal 1 MEC2181 Mechanical Simulation 11 or 12 September 2024 Mesh dependence analysis Transient thermal analysis Introduction to processing tools in ANSYS thermal analysi...

SIT Internal 1 MEC2181 Mechanical Simulation 11 or 12 September 2024 Mesh dependence analysis Transient thermal analysis Introduction to processing tools in ANSYS thermal analysis By: Elisa Ang Email: [email protected]  SIT Internal Mesh dependence study 2  SIT SITInternal Internal Lets recap Week 1 Steady State Analysis of 2D flat plate 3  SIT SITInternal Internal Recall we chose a mesh size of 0.001 3. Next click on element size and enter 0.001 (1mm element size) 𝜕𝜕 2 𝑇𝑇 𝜕𝜕 2 𝑇𝑇 But how do we know this is correct? + =0 Remember that when we discretize, the larger 𝜕𝜕𝑥𝑥 2 𝜕𝜕𝑦𝑦 2 ∆𝑥𝑥/∆𝑦𝑦 is, the larger is the error for the approximation 𝜕𝜕2 𝑇𝑇 𝑇𝑇(𝑥𝑥+∆𝑥𝑥,𝑦𝑦)−2𝑇𝑇(𝑥𝑥,𝑦𝑦)+𝑇𝑇(𝑥𝑥−∆𝑥𝑥,𝑦𝑦) 𝜕𝜕 2 𝑇𝑇 𝑇𝑇(𝑥𝑥, 𝑦𝑦 + ∆𝑦𝑦) − 2𝑇𝑇(𝑥𝑥, 𝑦𝑦) + 𝑇𝑇(𝑥𝑥, 𝑦𝑦 − ∆𝑦𝑦) ≈ ≈ 𝜕𝜕𝑥𝑥 2 ∆𝑥𝑥 2 𝜕𝜕𝑦𝑦 2 ∆𝑦𝑦 2 4  SIT SITInternal Internal Tradeoff between accuracy of results and computational time required Less accurate, More accurate, Fast to solve Slow to solve 5  SIT SITInternal Internal Mesh dependence study 6  SIT SITInternal Internal Lets apply this to our 2D flat plat analysis We are going to test mesh size varying from 0.05 to 0.00075 Mesh size (mm) Average temperature Temperature at the of the plate (℃) midpoint (℃) 0.005 0.0025 0.001 0.00075 Student license limit 7  SIT SITInternal Internal Lets apply this to our 2D flat plat analysis Open up Week1_Lab.wbpj. Rename the analysis system meshsize=0.001mm 8  SIT SITInternal Internal Lets apply this to our 2D flat plat analysis Duplicate the workbench 3x, and rename the analysis system based on meshsize Click on the down arrow here and select Duplicate 9  SIT SITInternal Internal Mesh dependence Study Click on the system for meshsize=0.001mm (which we solved for in week1) – click on Solution: 10  SIT SITInternal Internal Mesh dependence Study Note down the average T of the flat plate Mesh size Average Temperature (mm) temperature at the of the plate midpoint (℃) (℃) 0.0025 0.001 92.762 0.0005 0.00025 11  SIT SITInternal Internal Mesh dependence Study Next insert a coordinate system at the centre of mass 1. Right click on Coordinate System 2. Select coordinate system at centre of mass 3. New coordinate system at the midpoint of the plate created 12  SIT SITInternal Internal Mesh dependence Study 1. Insert a temperature probe 13  SIT SITInternal Internal Mesh dependence Study 2. Select Coordinate System 14  SIT SITInternal Internal Mesh dependence Study 3. Select the Coordinate System we just created 15  SIT SITInternal Internal Mesh dependence Study 4. Right click on Temperature Probe and Click on Evaluate all results 16  SIT SITInternal Internal Mesh dependence Study Note down the temperature at midpoint of the flat plate. Close Ansys Mechanical Mesh size Average Temperature (mm) temperature at the of the plate midpoint (℃) (℃) 0.0025 0.001 92.762 93.75 0.0005 0.00025 17  SIT SITInternal Internal Mesh dependence Study Next open up meshsize=0.005 system, click on Setup 18  SIT SITInternal Internal Mesh dependence Study Change the mesh size to 0.005 19  SIT SITInternal Internal Mesh dependence Study Add the coordinate system at Centre of Mass and add the thermal probe Then click solve 20  SIT SITInternal Internal Mesh dependence Study Fill in the values in the mesh dependence study table Mesh size Average Temperature (mm) temperature at the of the plate midpoint (℃) (℃) 0.005 78.872 108.29 0.0025 0.001 92.762 93.75 0.00075 21  SIT SITInternal Internal Mesh dependence Study Repeat for the other two systems to complete the table: Mesh size Average Temperature (mm) temperature at the of the plate midpoint (℃) (℃) 0.005 78.872 108.29 0.0025 88.696 93.916 0.001 92.762 93.75 0.00075 93.225 93.75 22  SIT SITInternal Internal Mesh dependence Study Plot out the points: what can be concluded? MESH DEPENDENCE STUDY Average temperature of the plate (℃) Temperature at the midpoint (℃) Mesh size Average Temperature 120 (mm) temperature at the 100 TEMPERATURE (℃) of the plate midpoint (℃) 80 (℃) 60 0.005 78.872 108.29 40 0.0025 88.696 93.916 20 0.001 92.762 93.75 0 0.00075 93.225 93.75 0 0.001 0.002 0.003 0.004 0.005 0.006 MEHS SIZE (MM) 23  SIT SITInternal Internal Transient Thermal Analysis 24  SIT SITInternal Internal Difference between steady state and transient thermal Transient thermal Steady state thermal 25  SIT SITInternal Internal Transient 3D heat transfer analysis In week 1, we looked at the steady state analysis of a rectangular fin Today’s lab, we will do the same problem, but transient analysis Start up workbench and select transient thermal 26  SIT SITInternal Internal Part 2A: Heat transfer analysis of a rectangular fin Some tips to get you started  Selecting copper alloy material Found under “General Materials” in the engineering data for materials in ANSYS  During model setup you will need to assign this material to the geometry 27  SIT SITInternal Internal Part 2A: Heat transfer analysis of a rectangular fin Some tips to get you started  Geometry -> using “pull” to create the fin 28  SIT SITInternal Internal Part 2A: Heat transfer analysis of a rectangular fin Some tips to get you started  Geometry -> using “pull” to create the fin Press spacebar and you can then enter how much to pull (say 100mm) 29  SIT SITInternal Internal Part 2A: Heat transfer analysis of a rectangular fin Some tips to get you started  Modeling the boundary conditions 30  SIT SITInternal Internal Part 2A: Heat transfer analysis of a rectangular fin Some tips to get you started  Modeling the boundary conditions 31  SIT SITInternal Internal Part 2A: Heat transfer analysis of a rectangular fin Some tips to get you started  Modeling the boundary conditions 32  SIT SITInternal Internal Transient thermal analysis Follows the same setup Only differences are  Need to assign initial conditions for e.g. in this case, initial condition of the rod 33 SIT SITInternal Internal Follows the same setup Only differences are  Need to assign initial conditions for e.g. in this case, initial condition of the rod  Also need to modify analysis settings for time step and transient sim end time 34  SIT SITInternal Internal Temperature solution is a time varying temperature profile from the prescribed initial conditions Pressing the play button plays the animation of the temperature variation with time 35