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452470312612Computer Tips:Install Exceed on your laptop for convenienceLarger screens are beneficial – plan to use school computers when working on multiple models or to keep models & instructions side-by-side00Computer Tips:Install Exceed on your laptop for convenienceLarger screens are beneficial – plan to use school computers when working on multiple models or to keep models & instructions side-by-sideRFDL Swirl ProjectCOMSOL Acoustic Modeling on HammerObtaining a Hammer AccountOpening COMSOLCreating a New ModelTroubleshooting GuideAudience: This guide is intended for engineering majors with general technical knowledge and ability to recognize basic terms and to learn new programs. The example given is for the acoustics module of COMSOL Multiphysics software, but can be used as a starting guide to any of COMSOL’s packages (fluid flow, heat transfer, etc.).4531995157432Learning COMSOL:Google search tutorials & the COMSOL User’s Guide for the version you’re using (4.4, etc.)00Learning COMSOL:Google search tutorials & the COMSOL User’s Guide for the version you’re using (4.4, etc.)Obtaining a Hammer AccountEmail rcc@rcc.psu.eduRequest access to Hammer clusterInclude name, PSU usernameRequest access to RFDL group folder4537075489860Choosing Configuration:Gnome Desktop, a full desktop setup connecting you to the Hammer system, has more visible options, such as internet and management of files from the desktopSeamless Mode, in which only a terminal (window used to open programs) appears, is easier to use with other programs. Windows can be open side-by-side and icons will still be visible at the bottom of the screen because you are still on your desktopIf a gray screen remains for more than 10 seconds, open the task manager and end your session00Choosing Configuration:Gnome Desktop, a full desktop setup connecting you to the Hammer system, has more visible options, such as internet and management of files from the desktopSeamless Mode, in which only a terminal (window used to open programs) appears, is easier to use with other programs. Windows can be open side-by-side and icons will still be visible at the bottom of the screen because you are still on your desktopIf a gray screen remains for more than 10 seconds, open the task manager and end your sessionUse a school computer (MNE not included) or install Exceed On Demand on your personal laptopOpening COMSOLOpen Exceed On DemandEnter username and passwordChoose a configuration and desktop typeDesktop_Mode_Full_Screen.cfgSeamless Mode.cfgChoose a desktop typeGnome_Desktop.xs should work for eitherTerminal.xs works for Seamless ModeClick “Run”-473075-37451Ending or Suspending a SessionIf not already visible (as in Seamless Mode), bring up the Exceed iconHit the Windows button at the bottom of your keyboard (Windows 7)Hit Alt-Tab (Windows 7 or 8)Ctrl-Alt-Delete locate the Exceed icon in the Task ManagerRight-click the Exceed iconHit “Close Window”Your session will now be suspendedThe session can be named, but will save the time of suspension and IP address regardlessExceed can be re-opened to end the sessionSessions in progress should come up immediately upon logging in0Ending or Suspending a SessionIf not already visible (as in Seamless Mode), bring up the Exceed iconHit the Windows button at the bottom of your keyboard (Windows 7)Hit Alt-Tab (Windows 7 or 8)Ctrl-Alt-Delete locate the Exceed icon in the Task ManagerRight-click the Exceed iconHit “Close Window”Your session will now be suspendedThe session can be named, but will save the time of suspension and IP address regardlessExceed can be re-opened to end the sessionSessions in progress should come up immediately upon logging in 457200044143Creating Shortcuts in Desktop Mode:Right-click the existing icon for “Terminal” under “Applications Accesories”Select “Add this launcher to Panel” to add to the top panel, as shown, or add it to the desktop00Creating Shortcuts in Desktop Mode:Right-click the existing icon for “Terminal” under “Applications Accesories”Select “Add this launcher to Panel” to add to the top panel, as shown, or add it to the desktopWithin a few seconds, you will be connected to the Hammer systemDesktop mode: a red desktop appearsAt the top of the screen, click “Applications” and mouse over “Accessories”Click “Terminal”45720001628140Accessing Internet:Since files are only saved to Hammer, internet may be usefulSelect one of the internet browsers under “Internet” under “Applications Accesories”If one browser does not work, try another. If issues persist, contact RCC00Accessing Internet:Since files are only saved to Hammer, internet may be usefulSelect one of the internet browsers under “Internet” under “Applications Accesories”If one browser does not work, try another. If issues persist, contact RCCSeamless Mode: a Terminal window appearsIn the Terminal window, type the prompt shown belowSubstitute the latest version of COMSOL for 4.4Hit “enter” before re-typing “comsol”4572000662305Alternate Windows:At the bottom right in Desktop Mode, there are 4 rectangles. Each is a different desktop. Comparing models side-by-side can be easier using different windowsOpening COMSOL in one window then switching to another will result in COMSOL opening in the window you are in00Alternate Windows:At the bottom right in Desktop Mode, there are 4 rectangles. Each is a different desktop. Comparing models side-by-side can be easier using different windowsOpening COMSOL in one window then switching to another will result in COMSOL opening in the window you are inHitting the up arrow brings up every command you have typed in terminal, starting from the most recent – use this to open COMSOL in the future COMSOL will open in about 5-10 secondsCreating a New ModelSelect “Model Wizard”Select “3D”Click the arrow to the left of “Acoustics” to display options; do the same for “Pressure Acoustics”Click “Add”At the bottom of the page are green arrows giving the option to move forward or back – move on to “Study”Select a StudyMultiple studies can be added, and multiple steps to a studyEigenfrequency = eigenfrequencies of the system; dependent on geometry, materials, and boundary conditionsFrequency Domain = forced response at user-defined frequencies; dependent on geometry, materials, and boundary conditions4599030109855Changing Units:Right-click “Component 1” in the left-hand window. Under “Component Settings Unit System”, choose units (SI, IPS, etc.)00Changing Units:Right-click “Component 1” in the left-hand window. Under “Component Settings Unit System”, choose units (SI, IPS, etc.)Build GeometryRight-clicking the “Geometry” in the left-hand “Model Builder” window gives you options of various shapes and operationsEach object can be defined by coordinates for its base as well as angles of rotationDefine MaterialsRight-click “Materials”; select “Add Material”4612943104167Geometry Tips:Re-used variables can be defined under “Definitions Parameters” – name a parameter and input it into the shape’s dimensions; algebraic operators (+ - / *) can also be used in with numbersUse “rotate” to create duplicates of selected shapes around an axis at specified anglesCreating other shapes in, on, or around a shape can allow you to delete entities or to select portions of a face in later steps00Geometry Tips:Re-used variables can be defined under “Definitions Parameters” – name a parameter and input it into the shape’s dimensions; algebraic operators (+ - / *) can also be used in with numbersUse “rotate” to create duplicates of selected shapes around an axis at specified anglesCreating other shapes in, on, or around a shape can allow you to delete entities or to select portions of a face in later steps“Built-In” materials include water, air, many metals, and more; you can define your own material but many material properties are requiredSet Initial / Boundary ConditionsDefine hard wall, pressure (such as P=0, or open to atmospheric pressure), and acceleration (such as caused by a speaker) boundary conditionsCreate a meshShould be fine enough to accurately define each shape for accurate computations – see example below, can try finer/coarser variations and check similarity of solutionsFine enough mesh:461391038735Material Error:If a small red “x” appears next to your material, define whatever property is missing. Most can be found online00Material Error:If a small red “x” appears next to your material, define whatever property is missing. Most can be found onlineQuestionably accurate mesh on round cone-shaped tubes:-327546109864Running a Parametric Sweep for Mesh ConvergenceTo ensure that your mesh is adequately fine, create variables for your minimum element size (and maximum, if you like) under “Global Definitions variables”When entering “Custom Size” parameters, use this ….Right-click “Study 1” and select “Parametric Sweep”Enter your variable(s) by hitting the + button below the table of parameter names and values, then enter varied valuesRun; collect results by checking eigenfrequencies and pressure plots outputted as results0Running a Parametric Sweep for Mesh ConvergenceTo ensure that your mesh is adequately fine, create variables for your minimum element size (and maximum, if you like) under “Global Definitions variables”When entering “Custom Size” parameters, use this ….Right-click “Study 1” and select “Parametric Sweep”Enter your variable(s) by hitting the + button below the table of parameter names and values, then enter varied valuesRun; collect results by checking eigenfrequencies and pressure plots outputted as results464023922832Result Plots – Section View:Right-click “Acoustic Pressure” under “Results” and select “Slice” Enter 1 under “Planes” and plot; if plot doesn’t work, plot in a new window by right-clicking “Slice 1”00Result Plots – Section View:Right-click “Acoustic Pressure” under “Results” and select “Slice” Enter 1 under “Planes” and plot; if plot doesn’t work, plot in a new window by right-clicking “Slice 1”Multiple sizes of mesh can be used on one model – under “Free Tetrahedral”, select Size 1 and select what to mesh at a different size (domain, boundary, edge, or point), then define a new sizeClick “Build All”To execute one of your solvers, right-click “Solve” and select “Compute”ResultsEigenfrequency study: Pressure plots at system eigenmodesFrequency Domain study: Pressure plots - forced solution at user-inputted frequenciesTroubleshooting GuideCOMSOL won’t openHammer has 20 nodes. For error “cannot reserve enough space on Java Virtual Machine” switch nodes by putting a number from 1 to 20 immediately after “hammer” in ExceedToo many users wait til later“Cannot reserve enough space for object heap”: you may have errors stored in system – these are very large. Type “ls” and hit enter to display everything in your account. Anything beginning with “core” or “Hss_err” is an error. Remove by typing “rm” then hit enterModel won’t runToo big of a mesh may lead to too many degrees of freedom for Hammer. Make the mesh coarser. Generally, about 300,000 degrees of freedom will still solve. If you have fewer, try re-opening an old model and re-buildingModel running very slowly, “cannot reserve enough space on Java Virtual Machine” switch nodesOther error – work from a previous model, re-build to current pointMesh guide:Size can be checked for accurate computations by running a parametric study (see blue box instructions on page 6)Adding another “Size” is possible if it needs to be finer – edit “Size” under “Free Tetrahedral” and select either boundaries or domains to mesh at a new sizeCurvature refers to how big a mesh element can be along a curved boundary ( smaller curvature = finer)Resolution controls how many mesh elements are present in finer regions (higher resolution = finer)Can’t email a file / want to save as a smaller file size – can clear all meshes and solutions (Edit Clear All) Material errorIf a small red “x” appears next to your material, define whatever property is missing. Most can be found online ................
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