ANSYS Icepak – Optimization Workflow

This article describes the workflow for performing Icepak optimization on Nimbix platform using Icepak CFD software and Workbench Design Explorer from ANSYS.

Icepak offers the capabilities of performing a parametric study of almost any type of input: object size, position, material, power, object status (active or inactive), etc.

To perform an Icepak optimization on NIMBIX, the following steps can be followed:

1. Start ANSYS Fluids from the Compute dashboard (stand-alone):

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NOTE: If the option (latest Ansys Fluid release or any other release) is not available in the first-page menu, press on “More” at the bottom of the page as shown in the image below:

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2. A splash window will open. Select the Icepak option as shown below:

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3. The cloud set-up screen opens and here you must choose some of your settings by clicking on the Tabs on the top of the window (General, Optional, etc) one tab at a time.

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UNDER GENERAL TAB

Under Machine type fly-down, when clicked, you have the choice of selecting the type of machine you want to run your job on. The decision on machine type selection is based on the size and complexity of your model and cost associated with the machine type (some machines will have higher RAM, others will only run the job on single CPU, others will have better graphics and therefore higher cost, etc).

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NOTE: When running interactive based applications, you’ll find that selecting an NC9 or any NC* machine types should offer significant visual performance over not selecting an NC machine type. By selecting an NC machine, this places a GPU on your head-node and offers better visual performance. Another thing to keep in mind is that when running interactively you can use a web browser, or in some cases for large models or you might consider using RealVNC.

2. Select the number of cores:

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The machine type you selected in the previous step, will dictate the increment in the number of cores that you can select. For a small model, you can leave default selection, which in this case would be “16” or move the scroll bar to the desired number of cores or simply type over “16” the number of cores you wish to run your job on (“default 16” in this case).

NOTE: Do not confuse number of cores with number of nodes (nodes represent the number of increment of cores that you selected. In the example above, 1 node represents 16 cores, 2 nodes represent 32 cores).

UNDER OPTIONAL TAB

Assign a JOB LABEL (give a name that will help you keep track on your running jobs. For example, Icepak_HS_Optimization):

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NOTE: Unless you have all the other information to fill in all other boxes such as Elastic License Server ID, etc., you can leave them blank and move on to the next Tab.

UNDER STORAGE TAB

Select vault type: Default vault is “drop.jarvice.com”

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The “drop.jarvice.com” vault is recommended for small to medium size jobs, such as Icepak projects, simple linear Mechanical Analysis project, some HFSS and simple Fluent projects (not multi-phase). For any complex and computationally heavy jobs, and where partitioning the job over the number of cores becomes challenging, the PREMIUM vault is strongly recommended. The PREMIUM vault can be found under the fly-down under “Select Vault” tab (NOTE: requires subscription and extra monthly payment to have access to PREMIUM vault).

Before submitting your job for running, you can preview your settings under the PREVIEW SUBMISSION tab.

ICEPAK PARAMETRIC STUDY USING WORKBENCH DESIGN EXPLORER OPTIMIZATION TOOL 

Icepak offers the capability of assigning a parameter to almost any input such as power value, object size, flowrate, object active or inactive, etc. These parameters can be defined using the Parameters and Optimization in Icepak (under Solve and select Run Optimization).

To assign a parameter to an input in your Icepak project, enter the “$” symbol before the name you wish to call your parameter (for example, $fin_count, for number of fins of a heat sink).

For each parameter, when assigned for the first time, you will need to provide an initial value for that parameter.

Here are the steps for setting up a parametric Icepak project:

  1. Create your geometry and assign material properties, boundary conditions, and setup your working domain (cabinet size, openings, etc)

For this example, we’ve created a geometry that consists of a printed circuit board, a heat source, a heat sink, a fan object which supply a constant airflow, and an opening for the exhaust air.

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2. Under the Solve tab select Define Trials and choose Parametric Trials and setup By Columns:

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3. Under Design Variables, setup your design variables (for more information on how and when you generate those names, please visit an Icepak parametric setup tutorial):

NOTE: In this example, we assigned some base value, range, end value and increment for fin count, fin thickness, and power value.

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4. Under the Functions tab you can define any function (such as a max limit, or a sum of output parameters, or thermal resistance, etc):

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5. If you would like to your trials or change the order in which the trials should be computed within Icepak, click on the Trials tab:

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6. At this point you can go ahead and mesh, run your Icepak model and the trials will be computed in the order shown under Trial Name.

For the example presented in this article, the Icepak model was meshed and ran prior to assigning any input parameters (it’s best to start by meshing and running your model to be sure the model converges and that is setup correctly) and the Input parameters were assigned after running the non-parametric model.

NOTE: The built-in optimizer in Icepak allows the user to predict the optimum values for the input parameters elected. However, it has some limitations regarding output parameter variation with respect to the input parameters selected, limited post-processing capabilities and does not permit complete optimization. To overcome this, Icepak parametric study can be launched within Workbench, where one can take advantage of the WB Design Explorer capabilities.

Steps for performing Icepak Design Optimization by using Workbench Design Explorer

1. Start ANSYS Workbench from NIMBIX Compute:

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2. Select machine type, number of cores, give a name (similar to the steps required to launch Ansys Fluids presented in detail at the beginning of this article)

3. After ANSYS Workbench Platform launched, drag an Icepak project in the Workbench Window as shown:

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4. Under Icepak Setup Tab, right click and you can select either Import Icepak Project from tzr (if you generated a tzr file of the previous Icepak model setup using the steps above) or Import Icepak Project (if you did not generate a tzr file):

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NOTE: When clicking on the Import Icepak Project, you will get a Browse Tab that will allow you to browse to where you saved your Icepak project created in the previous steps shown in detail above.

5. After importing the Icepak project, a new Icepak Window will open, and your model will show:

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6. Under Solve Tab on the toolbar you must click on Define Variables or Run Optimization, and you can see all variables that were setup in your Icepak model earlier, as shown in the image below:

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NOTE: You can see that in this Window, a new tab appeared called “Publish to WB” which will allow you to transfer the assigned input parameters and functions from the stand-alone Icepak to Workbench Design Modeler.

7. Click “Publish to WB” for selecting which of the input parameters and functions setup in Icepak project you would like to transfer to Workbench for being able to use Workbench Design Explorer optimization capabilities:

NOTE: For the example presented in this article, all variables have been selected (fin_count, fin_thickness, and power) as well as the heat_sink function (which allows us to calculate the heat sink thermal resistance). All of these variables were setup in stand-alone Icepak project and by clicking on Publish to WB, they will be transferred to Workbench Design Explorer.

8. After clicking on the Accept tab under Publish to WB window above and clicking Done, you can save and close your Icepak Window and note the Parameter Tab that will appear in your Workbench:

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9. Click the “Parameters” box under your Icepak project and you can see that all your input and output variables appear in the Workbench Parameter Window:

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NOTE: You can generate as many input combinations as you believe are plausible (given design constrains, heat sink weight, etc) and the software will calculate the output called “heat_sink” which represents here the heat sink’s thermal resistance.

See below an image of some of the input parameter sets that were tried for the example presented in this article:

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NOTE: To run all Design Points as defined by your combination of input parameters, you need to select all the design points and right-click on Update Selected Design Points and the software will run one by one each of the design points named here as DP 0, DP 1, DP 2, etc.

10. Additionally, Direct Optimization or Response Surface methodology can be used to further refine your model and generate transfer functions using ANSYS Design Explorer

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NOTE: Check your design points for completeness and correctness (use manufacturing values if needed, verify design limits, etc) as well as run optimization and Six Sigma analysis using objective functions based on your needs.

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