FTLecture-2A-2B

nullLecture 2ALecture 2ABuild, Solve and Analyse a Simple Case Five steps to build a modelFive steps to build a modelStep 1 – Define what to model Step 2 – Create geometry Step 3 – Add grid Step 4 – Solve the model Step 5 – Analyse the resultsDefine what to modelDefine what to modelStart Simple Electronics Box Chassis Model with an enclosure Components Model with a heat source Vents Model with perforated plates Define what to ModelDefine what to ModelAmount of “the world” to include in model is given by the Solution Domain. Must include all geometrical and thermal / flow features needed to define the model. Defined using position and size Right-Click on the System NodeAmbient ConditionsAmbient ConditionsConditions outside our Solution Domain are set using Ambients: Right-Click on the System Node Select Ambients nullAmbient Conditions By default, the ambient conditions are those set in the Global System Settings Dialog, that is, the datum pressure, fluid temperature and temperature of a remote radiating source. The ambient conditions can be further refined for a particular face of the solution domain by attaching an ambient attribute. Ambient attributes are defined using the Ambient Attribute Dialog Name: Identifies the ambient attributes Gauge Pressure: Sets the pressure for the fluid external to the domain face, relative to the Datum Pressure. Temperature: Sets the temperature for the fluid external to the selected domain face. Radiant Temperature: Sets the temperature of a remote radiating source. Heat Transfer Coefficient:Sets the Heat Transfer Coefficient for any solid surfaces coincident with the selected domain face. If you are using the KE turbulence model, you can also set Turbulent Kinetic Energy and Turbulent Dissipation Rate. External Velocity: Sets the ambient wind velocity for the fluid external to the selected domain or cutout face. Managing ProjectsManaging ProjectsProject / Save As Creates a new project with given name in selected Solution Directory. Add Notes Allows description to be added to a project. Could be used to track changes. Can be displayed from Project / Load dialogue nullSaving projects To save the current project, use Project / Save or the save icon. This overwrites the current project on disk. It saves the full project data set to the projects directory. Note that if the project has never been saved or was originally saved by another user, the Save Project Dialog is displayed so that you can identify the appropriate project name, directory and other ancillary information. To save the current project under a new name, use Project / Save As. This will launch the Project Save Dialog: nullProject Save Dialog Project Name Sets the name the project data set is to be saved under. The project name appears in the status bar near the bottom of the application window. If you enter the name of an existing project you will be prompted to confirm the save which will overwrite the named project. Class Identifies the project class type, e.g. department name. Sub-Class Identifies the project sub-class type, e.g. client name. Title Sets the project title intended to later help identify the project. The title for the active project always appears in the status bar near the bottom of the window. [Notes...] Calls the Edit Notes Dialog to attach reference information to the project. Project Solution Directory Indicates the directory to hold the project data and results. To change the directory, click [Browse...] to display a file browser to choose the required directory. Save As Template Requests the project is saved as a template and assigned to the Category indicated. You can change this Category by either choosing it from the pop-up list or typing in your own. nullLoading Projects To load an existing project into the project manager, use Project / Load. This will launch the Project Load Dialog: nullProject Load Dialog The Project Load Dialog comprises a list of all the projects of the classification selected in the Filter Project dialog. By default, the list is filtered by your username. To load a project, select it in the list and click [Load]. To help you check you have selected the right project, the project title appears below the list, and using [Notes] you can display any attached project notes. [Filter...] Calls the Filter Project dialog to allow you to confine the scroll list to particular categories of project files, i.e. by class, sub-class, username, before date or after date. [Delete] Removes the selected project and its related solution data from the list and the current project directory. You cannot delete a project while it is currently loaded in program memory. If you want to delete the current project, you will have to either load in a different project or start a new one first. Also, you cannot delete a project that was not saved under your own username [Unlock] Allows you to unlock a project after a system failure. But, as FLOTHERM also locks projects in current use, before unlocking a project check that you are not using it in another program session, and in a multi-user system, it is not being used by someone else. [Pack...] Calls the Pack Project selection dialog to save the highlighted project in a compressed format of both model and solution data ready for archiving or transfer to Flomerics customer support. You choose the file name and destination with the default file extension being .pack. Note: As FLOTHERM identifies packed projects by the .pack filename extension, when naming the packed project ensure you keep the default .pack extension. nullProject Load Dialog (cont.) [Unpack...] Calls the Unpack Project selection dialog so that you can choose a packed file (see Pack above) and import into the system. By default, the filter searches for .pack files. When unpacked, the name of the project is added to the scroll list. As the project name may not be the same as its original file name, the imported unpacked project is highlighted by a colored background. Note: You cannot unpack a project into the same project directory that it was packed from due to conflicts between the two projects. You must first delete the original project before unpacking the packed version, or change the Project Solution Directory setting. Title Displays the title of the project currently highlighted in the scroll list. Project Solution Directory Sets the directory from which to load your projects. The initial default setting is set-up during the installation procedure. Use the [Browse...] button to call a file browser to locate the directory. Any change made here is reset if the dialog is cancelled. To save the project in another directory, you must use the Project Save dialog ([Project/Save As...]). [Catalog] Catalogs all the FLOTHERM projects held in the solution sub-directory and displays them in the dialog selection list. Use [Catalog] when it is known that there are projects copied or moved into the directory using the operating system, but they are not listed in the dialog. Alternatively, use the key sequence with the Project Manager open, before calling the Load Project Dialog. nullProject Load Dialog (cont.) [Notes...] Calls the Notes dialog to display any notes attached to the project currently highlighted in the scroll list. [Load] Loads the project selected in the project list. [Cancel] Cancels the load and any solution directory selection change. Managing ProjectsManaging ProjectsProject / Save ( ) Overwrites currently loaded project. If no valid name uses “Save As” dialogue. Edit Notes and title… Allows notes and / or title without changing the project name.Managing ProjectsManaging ProjectsImport / Export Entire Project via right click on top nodeFormats Pdml/Pack V2/V3 *.project V1.4 files Plus Export only of MCAD files.nullImporting / Exporting Projects can be imported and exported to share with other users. The PDML file contains all the project information, but does not contain any results. Export: Right-Click on the project name at the top of the project manager tree, then choose Export Project, then PDML. Import: Right-Click on the project name at the top of the project manager tree, then choose Import. Choose Flomerics File, then PDML. How do I create geometry?How do I create geometry?Select appropriate item Set its size Position it correctly Define the materialChassis StructureChassis StructureTo model a hollow box, use the Enclosure SmartPart Select Enclosure from the PM geometry palette – default enclosure is created Select Enclosure in the DB geometry palette – now draw the enclosure Setting SizeSetting SizeSelect Enclosure Right-Click to activate Enclosure Menu Select Construction Type appropriate size Type appropriate thickness Walls can be thin (collapsed) or thick (non-collapsed) Setting LocationSetting LocationSelect Enclosure Right-Click to activate Enclosure Menu Select Location Type appropriate location Setting Size & LocationSetting Size & LocationAlternatively, size and location can be set in DB Select the Enclosure Move handles to resize Move Enclosure to reposition Move object Re-size in one direction Re-size in two directionsnullEnclosure SmartPart It’s possible to build a box using cuboids, but it’s better to use the enclosure smartpart. The enclosure smartpart consists of a hollow cuboid-shaped box with six solid walls, each of which can be: Optionally removed Treated as thick or thin Holed by one or more resistances or other materials The Enclosure Dialog sets the basic specification for the enclosure, that is, its overall size and thickness of all the walls. But for setting the individual side details (e.g. its existence or different thickness), the Side of Enclosure Dialog is used. nullSizing the Enclosure SmartPart Set the size of the enclosure by right-clicking on the enclosure, then selecting Construction. Alternatively, resize the enclosure in the Drawing Board.Positioning the Enclosure SmartPart Position the enclosure by right-clicking on the enclosure, then selecting Location. Alternatively, move the enclosure in the Drawing Board. Attaching MaterialAttaching MaterialOpen Library Manager Select Material Drag it onto Enclosure Or: Right-Click on Enclosure Select Material Attach Material from ListAttaching MaterialAttaching MaterialTo view Material properties Right-Click on Enclosure Select Material Select the attached material from list Click EditnullMaterial The thermal and electromagnetic properties of an object are controlled by the material attribute attached to it. The material properties can be viewed and edited in the Material Property Dialog. The most significant thermal property is the conductivity, which sets the thermal conductivity for the material according to three options: i Constant - Sets a constant value for all three directions. ii Temperature Dependent Conductivity - Sets the conductivity to vary according to a linear function of temperature: Conductivity = Value + Coeff (Temperature - Reference Temperature) where the Value you enter is the conductivity at the Reference Temperature and Temperature is the temperature of the solid material. iii Orthotropic Conductivity - Sets the conductivity values separately in each direction for the material. This option allows you to define different conductivity values in the three coordinate directions of X, Y and Z Density and Specific Heat are required for Transient simulations. How do I add heat?How do I add heat?Select appropriate item (Source) Set its size Position it correctly Define the power (Source Attribute)Setting Size & LocationSetting Size & LocationSelect Source Right-Click to activate Source Menu Select Location Alternatively, size and location can be set in DBAdding PowerAdding PowerSelect Source Right-Click to activate Source Menu Select Source Create New Source Attach Source from ListAdding PowerAdding PowerSource Power is controlled by the Source Attribute For a thermal source, choose Applies To: Temperature Set the PowernullSource Activate Activates the dialog options. When de-activated, the effects of the source are removed. By default, all sources are de-activated. Source/Volume Only active for volume sources. For ‘temperature’, this option sets the source (positive) or sink (negative) of heat per unit volume. Source/Area Only active for planar sources. For ‘temperature’, this option sets the source (positive) or sink (negative) of heat per unit area of the plane. Total Source Option For ‘temperature’, this option sets the total source of heat applied over the defined plane or volume which the program will distribute uniformly over the plane or volume. Fixed Value Option For ‘temperature’, this option fixes the temperatures to the set value. If it is a planar source, then the temperature is set in the cells adjoining the plane on the selected side of the plane. The figure below is an example of high side attachments. nullSource (cont.) Linear Source Option (for Temperature) For ‘temperature’, the linear source of heat per unit area of the planar region is given by (for each grid cell on the high side): source = coefficient x (value – temperature) where temperature is that in the grid cell in the fluid on the high side. The program calculates temperature, whereas the user sets coefficient and value. [Transient Attribute...] Only available for transient simulations. It allows you to apply a transient function describing the variation of the source output with time. Pressing [Transient Attribute...] results in the display of the Transient Function Attribute Dialog so you can either select an existing transient function or create a new one. How do I add vents?How do I add vents?A vent is often a complex series of small holes.Need to represent the effect without modelling the exact dimensions and layout of the holes.How do I add Vents?How do I add Vents?The effect is a Pressure drop which can be defined as…Where: f = loss coefficient v = velocityHow do I add VentsHow do I add VentsSources of Pressure drop vs. velocity data: Text books (e.g. Fried & Idelchik) Wind tunnel experiments (both physical and numerical). These will provide the loss coefficient. How do I add Vents?How do I add Vents?Approach VelocityDevice Velocity =Free Area Ratio (b)Approach Velocity(Velocity Calculated by FLOTHERM)Loss Coefficient can be based on Approach or device velocity…If using device velocity, program must know the free area ratio, b.How do I add Vents?How do I add Vents?FLOTHERM offers two options: Resistance Primitive (uses basic formula) Perforated Plate SmartPart (can be defined using actual construction data)To help: Library of Resistance attributes for various grilles Automatic calculation in Perforated Plate SmartPart based on construction data How do I add vents?How do I add vents?Select appropriate item (Perforated Plate SmartPart) Set its size Position it correctly Define the loss coefficientSetting SizeSetting SizeSelect Perforated Plate Right-Click to activate Perforated Plate Menu Select Construction Type appropriate sizeSetting LocationSetting LocationSelect Perforated Plate Right-Click to activate Perforated Plate Menu Select Location Type appropriate position Setting Size & LocationSetting Size & LocationAlternatively, size and location can be set in DB Select the Perforated Plate Move handles to resize Move Perforated Plate to reposition Move object Re-size in one direction Re-size in two directionsSetting Loss CoefficientSetting Loss CoefficientThe pressure drop characteristics of the Perforated Plate are set in the Construction Dialog Enter a hole pattern Or enter a free area ratio Choose Resistance Model nullPerforated Plate SmartPart Hole Type and Size Sets the shape and size of the hole. You can have square, round or hexagonal holes. The holes will cut through the full thickness of the plate. Coverage Defines the free area ratio (the ratio of the holes to the total area across the plate). By default, the program calculates the free area ratio from the pattern of holes specified. The pitch sets the spacing between the objects. It is the distance between the start edges of each object in the given direction. Alternatively, you can enter the free area ratio directly. Resistance Model Sets the resistance model to one of three options: Standard This option should be used when you know the loss coefficient for this particular perforated plate and the flow is fully turbulent. Advanced This option should be used when you know the loss coefficient for this perforated plate and the flow is transitional or laminar. Automatic This option automatically selects the correct coefficients in the resistance formula based on the free are ratio provided by the hole calculation or manual setting in the dialog. Straighten Flow Sets the two air velocity components parallel to the plate on either its high or low side (as indicated by the checked box) to zero. The figure below shows the flow straightened for the high side of the plate.Define GridDefine GridThe solution domain is split into a number of finite volumes (or grid cells) The governing equations are solved at each cellDefine GridDefine GridWhy do we need grid? Allows equations to be solved at discrete points More grid = more points to capture overall picture = more precise results nullGrid Definition The finer the grid used (i.e. the greater the number of grid cells) the closer the algebraic equations approximate to the differential equations from which they originated. Normally more grid is used in regions of the domain where gradients of the variables are expected to be greatest. However, grid-independence of the solution alone is not enough to ensure that the solution obtained simulates what in reality occurs because other modeling assumptions (e.g. the accuracy of the boundary condition information supplied, the adequacy of the turbulence model) may be determining factors in the agreement of the simulation with physical reality. Consequently, the outcome of a CFD simulation must be inspected carefully with a view to assessing the physical realism of the results obtained. Lecture 5 describes gridding techniques in more detail.Refining GridRefining GridWhy do we need grid? Courtesy of frogstore.comAs we refine the grid, more detail is apparent Define GridDefine GridHow do we add grid? Geometry provides keypoints for gridGrid lines automatically appear along edges of all objectsDefine GridDefine GridHow do we add grid? Grid can be generated automatically to four default levels N.B. None = Keypoint grid Define GridDefine GridEffect of presets… SolvingSolvingGoverning equations are solved within domain Attach ambients to describe conditions outside the domain SolvingSolvingThe governing equations are solved iteratively Error in system is measured When this error is low enough, results can be acceptedAnalyze ResultsAnalyze ResultsView Planes Temperature plane Velocity planeFlomotionFlomotionCreation of a Plane Plot: Using Tool Bar Select Variable Select Direction Create Plane FlomotionFlomotion Use Manipulator to Move Press “w” to display in wireframe FlomotionFlomotion Alternatively select geometry (use shift to multi-select) And Hide using Function Key F12 FlomotionFlomotionPlane can be animated: Press Play on Tool Bar Plane can be animated: Control using settings dialogue Lecture 2BLecture 2BBuild, Solve and Analyse a Simple CaseWhat type of result do we want?What type of result do we want?What type of results were we trying to get? Are we looking for general air flow, board temperatures, or junction temperatures? To get those results, why did we model the Chassis, vents and total power? Initially, we were only looking for general air flow through the vents, and temperature rise. Was the grid sufficient?Was the grid sufficient?Was the grid sufficient to get