{"id":23085,"date":"2019-12-19T10:45:48","date_gmt":"2019-12-19T10:45:48","guid":{"rendered":"https:\/\/www.simscale.com\/?post_type=epkb_post_type_1&#038;p=23085"},"modified":"2025-07-22T11:17:44","modified_gmt":"2025-07-22T11:17:44","slug":"flow-volume-extraction","status":"publish","type":"epkb_post_type_1","link":"https:\/\/www.simscale.com\/knowledge-base\/flow-volume-extraction\/","title":{"rendered":"How To Create Flow Volume Extraction?"},"content":{"rendered":"\n\t\t<div id=\"eckb-article-page-container-v2\" class=\"eckb-article-page-content-counter eckb_ap_active_theme_simscale \" data-mobile_breakpoint=\"768\">    \t\t\t\t<a href=\"#eckb-article-content\" class=\"eckb-skip-link eckb-screen-reader-text\">Skip to main content<\/a>   <div id=\"eckb-article-header\" ><\/div>\n\t\t\t<div id=\"eckb-article-body\">  <div id=\"eckb-article-left-sidebar\" ><\/div>\n\t\t        <article id=\"eckb-article-content\" tabindex=\"-1\" data-article-id=\"23085\" >                        <div id=\"eckb-article-content-header-v2\" ><div id=\"eckb-article-content-header-row-3\"><div class=\"eckb-article-content-header-row-left-group\">\n\t\t<div class=\"eckb-article-content-created-date-container\">\t\t<span class=\"eckb-meta-data-feature-icon epkbfa epkbfa-calendar\"><\/span><span class=\"eckb-meta-data-feature-text\">Created On<\/span><span class=\"eckb-meta-data-feature-value\"><time class=\"entry-date\" datetime=\"2019-12-19T10:45:48+00:00\">December 19, 2019<\/time><\/span>\t\t<\/div> \n\t\t<div class=\"eckb-article-content-author-container\">\t\t<span class=\"eckb-meta-data-feature-icon epkbfa epkbfa-user\"><\/span><span class=\"eckb-meta-data-feature-text\">by<\/span><span class=\"eckb-meta-data-feature-value\">Sebastian Guenther<\/span>\t\t<\/div> <\/div><\/div><\/div><div id=\"eckb-article-content-body\" >\n<p class=\"wp-block-paragraph\">The simulation domain for a fluid dynamics simulation is the region occupied by the fluid (gas or liquid).&nbsp;However, in many cases, the original CAD model will initially not contain the fluid volume. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In such cases you can extract the fluid region, using the <em>Flow volume extraction<\/em> feature within SimScale&#8217;s <a href=\"https:\/\/www.simscale.com\/docs\/cad-preparation\/cad-mode\/\">CAD Edit<\/a> tool. We call this process Fluid Volume Extraction.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/entering-the-cad-editing-environment-in-simscale.png\"><img loading=\"lazy\" decoding=\"async\" width=\"755\" height=\"343\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/entering-the-cad-editing-environment-in-simscale.png\" alt=\"entering the cad editing tool in simscale\" class=\"wp-image-98873\" style=\"width:661px;height:auto\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/entering-the-cad-editing-environment-in-simscale.png 755w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/entering-the-cad-editing-environment-in-simscale-300x136.png 300w\" sizes=\"auto, (max-width: 755px) 100vw, 755px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 1: Select a geometry of interest and click on the <strong>&#8216;Edit a copy&#8217;<\/strong> button to enter the CAD editing environment.<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">To illustrate the objective further, see the basic use case of a flow simulation through a pipe below.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2019\/12\/flow-volume-extraction-example.jpg\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" width=\"1314\" height=\"503\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2019\/12\/flow-volume-extraction-example.jpg\" alt=\"example of how flow volume extraction works\" class=\"wp-image-23084\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2019\/12\/flow-volume-extraction-example.jpg 1314w, https:\/\/frontend-assets.simscale.com\/media\/2019\/12\/flow-volume-extraction-example-300x115.jpg 300w, https:\/\/frontend-assets.simscale.com\/media\/2019\/12\/flow-volume-extraction-example-1024x392.jpg 1024w, https:\/\/frontend-assets.simscale.com\/media\/2019\/12\/flow-volume-extraction-example-768x294.jpg 768w\" sizes=\"auto, (max-width: 1314px) 100vw, 1314px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 2: <strong>Left:<\/strong> Pipe geometry. The goal is to simulate the fluid flow through this pipe intersection. The model only contains the walls of the pipe. <strong>Right:<\/strong> The extracted flow volume through the pipe. This is the region that the fluid occupies and is required as input geometry for the simulation.<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">The two main flow volume extraction modes available within SimScale are:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Internal Flow Volume<\/li>\n\n\n\n<li>External Flow Volume<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-options-in-cad-editing.png\"><img loading=\"lazy\" decoding=\"async\" width=\"608\" height=\"398\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-options-in-cad-editing.png\" alt=\"flow volume creation options in the cad editing tool\" class=\"wp-image-98875\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-options-in-cad-editing.png 608w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-options-in-cad-editing-300x196.png 300w\" sizes=\"auto, (max-width: 608px) 100vw, 608px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 3: When hovering over the <em>Flow volume<\/em> operation, options for internal and external flow volumes will appear.<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">Depending on your geometry, you may use one of two modes to extract the fluid volume. Below are examples for each type.<\/p>\n\n\n\n<div class=\"hw-block hw-note hw-note--success hw-note\">\n    <div class=\"hw-note__title\">\n        <p class=\"hw-note__titleText\"><i class=\"fa fa-exclamation-circle\" aria-hidden=\"true\"><\/i>Did you know?<\/p>\n    <\/div>\n    <div class=\"hw-note__body\">\n        <p>The third flow volume operation, <i>Internal caps<\/i>, is specific to conjugate heat transfer IBM simulations. Visit <a href=\"https:\/\/www.simscale.com\/docs\/cad-preparation\/cad-mode\/#internal-caps\">this page<\/a> for more details.<\/p>\n    <\/div>\n<\/div>\n\n\n\n<h2 id='1-internal-flow-volume' class=\"wp-block-heading\" id=\"internal-flow-volume\">1. Internal Flow Volume<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This operation generates an internal flow volume. For instance, the example below shows how to generate the internal flow volume of the heat exchanger from <a href=\"https:\/\/www.simscale.com\/docs\/tutorials\/cht-heat-exchanger\/\">this tutorial<\/a>. The heat exchanger has two openings for each fluid. Extract one of the flow volumes as follows:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Select an &#8216;<strong>Internal<\/strong>&#8216; flow volume operation<\/li>\n\n\n\n<li>Select one internal <a href=\"https:\/\/www.simscale.com\/knowledge-base\/what-is-a-seed-face\/\">Seed face<\/a> (blue)<\/li>\n\n\n\n<li>Select the <em>Boundary faces<\/em> that lie between the external environment and the internal (highlighted in pink)<\/li>\n\n\n\n<li>If your geometry contains <a href=\"https:\/\/www.simscale.com\/knowledge-base\/how-to-create-cell-zones\/#what-is-a-cell-zone-and-why-we-need-them\">cell zones<\/a>, such as porous media and momentum sources, assign them to <em>Excluded parts<\/em>. If not, leave this definition empty<\/li>\n\n\n\n<li>Hit&nbsp;<strong>\u2018Apply\u2019<\/strong>&nbsp;to run the operation<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/internal-flow-volume-creation.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1441\" height=\"805\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/internal-flow-volume-creation.png\" alt=\"internal flow volume creation\" class=\"wp-image-98876\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/internal-flow-volume-creation.png 1441w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/internal-flow-volume-creation-300x168.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/internal-flow-volume-creation-1024x572.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/internal-flow-volume-creation-768x429.png 768w\" sizes=\"auto, (max-width: 1441px) 100vw, 1441px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 4: Creating an internal flow volume in a heat exchanger that has two openings<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">This will result in a geometry that contains both the fluid volume and the outer wall geometry as two separate parts. However, for a simple fluid flow simulation, you need only a single fluid volume. Keep the outer wall geometry (solid body) only in case of a <a href=\"https:\/\/www.simscale.com\/docs\/analysis-types\/conjugate-heat-transfer-analysis\/\">conjugate heat transfer<\/a> simulation, in which heat transfer between the solid parts and the fluid domain is simulated. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If you are going to perform a single region analysis like <a href=\"https:\/\/www.simscale.com\/docs\/analysis-types\/incompressible-fluid-flow-analysis\/\">incompressible<\/a>, <a href=\"https:\/\/www.simscale.com\/docs\/analysis-types\/compressible-fluid-flow-analysis\/\">compressible<\/a>, or <a href=\"https:\/\/www.simscale.com\/docs\/analysis-types\/convective-heat-transfer-analysis\/\">convective heat transfer<\/a>, you need to delete the solid body as follows:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/deleting-a-solid-part.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1128\" height=\"778\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/deleting-a-solid-part.png\" alt=\"deleting parts of a geometry in simscale\" class=\"wp-image-98877\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/deleting-a-solid-part.png 1128w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/deleting-a-solid-part-300x207.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/deleting-a-solid-part-1024x706.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/deleting-a-solid-part-768x530.png 768w\" sizes=\"auto, (max-width: 1128px) 100vw, 1128px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 5: If you are going to run single region simulations, such as incompressible and compressible simulations, you have to delete the solid parts of the geometry<\/figcaption><\/figure>\n<\/div>\n\n\n<ol class=\"wp-block-list\">\n<li>Choose the <strong>&#8216;Delete&#8217;<\/strong> operation under <em>BODY<\/em><\/li>\n\n\n\n<li>Pick the solid volume that needs to be removed. In this example, it is the <em>Shell<\/em> of the heat exchanger<\/li>\n\n\n\n<li>Hit <strong>&#8216;Apply&#8217;<\/strong><\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">After all the operations are concluded exit CAD mode by clicking on <strong>&#8216;Save&#8217;<\/strong>. This will save the new version of the geometry in the Workbench for you to use.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-a-cad-from-the-editing-tool.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1225\" height=\"749\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-a-cad-from-the-editing-tool.png\" alt=\"exporting a new cad model from the cad editing tool\" class=\"wp-image-98878\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-a-cad-from-the-editing-tool.png 1225w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-a-cad-from-the-editing-tool-300x183.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-a-cad-from-the-editing-tool-1024x626.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-a-cad-from-the-editing-tool-768x470.png 768w\" sizes=\"auto, (max-width: 1225px) 100vw, 1225px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 6: Click on the save button in the upper right corner to use the new version of the CAD model for simulations.<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">Note that the definition of boundary faces is optional for internal flow volume operations. This is because some CAD models do not have any openings, leading to no boundary faces.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the following image, you see the walls and ducting system of the theatre model highlighted in <a href=\"https:\/\/www.simscale.com\/docs\/tutorials\/thermal-comfort\/\">this tutorial<\/a>. This theater room does not have any openings on the walls or duct system.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1213\" height=\"825\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation.png\" alt=\"theater room geometry without flow volume\" class=\"wp-image-98879\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation.png 1213w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation-300x204.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation-1024x696.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation-768x522.png 768w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-cad-model-flow-volume-creation-368x250.png 368w\" sizes=\"auto, (max-width: 1213px) 100vw, 1213px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 7: Original theater geometry without a flow volume<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">If this is the case, the only mandatory definition for an internal flow volume creation is a seed face. By hiding some of the external faces of the theater you will be able to select a seed face on the inside of the model.<\/p>\n\n\n\n<ol id=\"block-6d073fdc-c0ab-4e35-8ff4-313e0a9ac21f\" class=\"wp-block-list\">\n<li>Create an &#8216;<strong>Internal<\/strong>&#8216; flow volume operation<\/li>\n\n\n\n<li>Hide some external faces of the geometry and select one internal <em><a href=\"https:\/\/www.simscale.com\/knowledge-base\/what-is-a-seed-face\/\">Seed face<\/a><\/em> (blue)<\/li>\n\n\n\n<li>Leave the <em>Boundary faces<\/em> empty<\/li>\n\n\n\n<li>In case there are cell zones in your model, assign them to <em>Excluded parts<\/em>. If not, leave it empty.<\/li>\n\n\n\n<li>Hit&nbsp;<strong>\u2018Apply\u2019<\/strong>&nbsp;to run the operation<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1571\" height=\"834\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater.png\" alt=\"flow volume creation no boundary faces\" class=\"wp-image-98880\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater.png 1571w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater-300x159.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater-1024x544.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater-768x408.png 768w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/flow-volume-creation-theater-1536x815.png 1536w\" sizes=\"auto, (max-width: 1571px) 100vw, 1571px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 8: Any face that will be in contact with the flow region, such as a chair in the example above, can be assigned as a seed face<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">After the flow volume extraction, you can delete the solid bodies to perform a convective heat transfer analysis. Finally, export the model to the Workbench by clicking on the <strong>&#8216;Save&#8217;<\/strong> button in the upper right corner.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-room-flow-volume.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1387\" height=\"758\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-room-flow-volume.png\" alt=\"theater room resulting flow region\" class=\"wp-image-98881\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-room-flow-volume.png 1387w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-room-flow-volume-300x164.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-room-flow-volume-1024x560.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/theater-room-flow-volume-768x420.png 768w\" sizes=\"auto, (max-width: 1387px) 100vw, 1387px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 9: Result of the flow volume extraction operation for the theater room<\/figcaption><\/figure>\n<\/div>\n\n\n<h2 id='2-external-flow-volume' class=\"wp-block-heading\" id=\"external-flow-volume\">2. External Flow Volume<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Above all, this option is often suitable for external flow problems. First, you need to size the external flow volume, and then run the operation. For instance, the example below shows how to generate a half-symmetrical air domain for the car geometry from <a href=\"https:\/\/www.simscale.com\/docs\/tutorials\/aerodynamic-simulation-vehicle\/\">this tutorial<\/a>.<\/p>\n\n\n\n<ol id=\"block-59e70a96-d8df-4b1e-a328-091e6f3c3918\" class=\"wp-block-list\">\n<li>After entering the CAD editing tool, select an &#8216;<strong>External<\/strong>&#8216; flow volume operation<\/li>\n\n\n\n<li>Define the <em>External flow volume<\/em> size by adjusting the minimum and maximum coordinates of the flow domain box<\/li>\n\n\n\n<li>The <a href=\"https:\/\/www.simscale.com\/knowledge-base\/what-is-a-seed-face\/\">seed face<\/a> definition is optional. If you leave this field blank, SimScale assumes that you are interested in creating a flow region external to the CAD model<\/li>\n\n\n\n<li>In case there are cell zones in your model, assign them to <em>Excluded parts<\/em>. If not, leave it empty<\/li>\n\n\n\n<li>Hit&nbsp;<strong>\u2018Apply\u2019<\/strong>&nbsp;to run the operation<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1579\" height=\"905\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car.png\" alt=\"external flow volume creation simscale\" class=\"wp-image-98882\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car.png 1579w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car-300x172.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car-1024x587.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car-768x440.png 768w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/external-flow-volume-creation-car-1536x880.png 1536w\" sizes=\"auto, (max-width: 1579px) 100vw, 1579px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 10: In this example, the external flow volume will act as a virtual wind tunnel<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">In addition, delete the solid parts to be able to use the model in an analysis type that requires a single fluid region:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Pick the&nbsp;<strong>\u2018Delete\u2019&nbsp;<\/strong>operation under&nbsp;<em>BODY<\/em><\/li>\n\n\n\n<li>Select the solid parts<\/li>\n\n\n\n<li>Hit&nbsp;<strong>\u2018Apply\u2019<\/strong><\/li>\n\n\n\n<li>Click&nbsp;<strong>\u2018Save\u2019<\/strong>&nbsp;to export the new CAD version to your Workbench<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1655\" height=\"859\" src=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume.png\" alt=\"exporting external flow domain to workbench\" class=\"wp-image-98883\" srcset=\"https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume.png 1655w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume-300x156.png 300w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume-1024x531.png 1024w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume-768x399.png 768w, https:\/\/frontend-assets.simscale.com\/media\/2025\/01\/exporting-external-flow-volume-1536x797.png 1536w\" sizes=\"auto, (max-width: 1655px) 100vw, 1655px\" \/><\/a><figcaption class=\"wp-element-caption\">Figure 11: Deleting the solid parts of the CAD model is necessary for single-region analysis types, such as incompressible simulations<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">When creating the external flow domain, pay attention to the box size. The size of the flow domain box should be large enough that the turbulent wake behind the model as well as the pressure region in front of the model does not reach the boundaries of the box. On the other hand, a large domain will likely increase the simulation expenses. Therefore, use your engineering judgment and\/or best practices to size the flow domain.<\/p>\n\n\n\n<div class=\"hw-block hw-note hw-note--warning hw-note\">\n    <div class=\"hw-note__title\">\n        <p class=\"hw-note__titleText\"><i class=\"fa fa-exclamation-circle\" aria-hidden=\"true\"><\/i>Running into errors<\/p>\n    <\/div>\n    <div class=\"hw-note__body\">\n        <p>If the above steps are not followed properly you may run into errors. The possible reasons for these errors are elaborated <a href=\"https:\/\/www.simscale.com\/knowledge-base\/why-do-geometry-operations-fail\/#flow-volume-extraction\">here<\/a>.<\/p>\n    <\/div>\n<\/div>\n\n\n\n<div class=\"hw-block hw-note hw-note--info hw-note\">\n    <div class=\"hw-note__title\">\n        <p class=\"hw-note__titleText\"><i class=\"fa fa-exclamation-circle\" aria-hidden=\"true\"><\/i>Note<\/p>\n    <\/div>\n    <div class=\"hw-note__body\">\n        <p>If none of the above suggestions solve your problem, then please post the issue on our <a href=\"https:\/\/www.simscale.com\/forum\/\">forum<\/a> or <a href=\"mailto:support@simscale.com\">contact us<\/a>.<\/p>\n    <\/div>\n<\/div>\n<\/div><div id=\"eckb-article-content-footer\" ><div class=\"eckb-tag-container\"  ><span class=\"eckb-tag-description\">Tags:  <\/span><ul class=\"eckb-tag-list\"><li><a href=\"https:\/\/www.simscale.com\/knowledge-base\/tag\/cad\/\" rel=\"tag\">CAD<\/a><\/li><li><a href=\"https:\/\/www.simscale.com\/knowledge-base\/tag\/flow-volume-extraction\/\" rel=\"tag\">Flow Volume Extraction<\/a><\/li><\/ul><\/div><\/div>\n\t\t        <\/article><!-- \/#eckb-article-content -->     <div id=\"eckb-article-right-sidebar\" ><\/div>\n\t\t\t<\/div><!-- \/#eckb-article-body -->              <div id=\"eckb-article-footer\" ><\/div>\n\t\t<\/div><!-- \/#eckb-article-page-container-v2 -->\n\n\t\t<style id=\"eckb-article-styles\" type=\"text\/css\">@media only screen and (min-width:768px){#eckb-article-page-container-v2 #eckb-article-body #eckb-article-content #eckb-article-content-header-v2 #eckb-article-content-header-row-1,#eckb-article-page-container-v2 #eckb-article-body #eckb-article-content #eckb-article-content-header-v2 #eckb-article-content-header-row-2,#eckb-article-page-container-v2 #eckb-article-body #eckb-article-content #eckb-article-content-header-v2 #eckb-article-content-header-row-3,#eckb-article-page-container-v2 #eckb-article-body #eckb-article-content #eckb-article-content-header-v2 #eckb-article-content-header-row-4,#eckb-article-page-container-v2 #eckb-article-body #eckb-article-content #eckb-article-content-header-v2 #eckb-article-content-header-row-5{flex-direction:row;}}#eckb-article-content-header-row-3{margin-bottom:32px;}#eckb-article-content-header-row-3 .eckb-article-content-header-row-left-group,#eckb-article-content-header-row-3 .eckb-article-content-header-row-right-group{align-items:flex-end;}<\/style>   ","protected":false},"excerpt":{"rendered":"<p>Learn how to create a Flow Volume Extraction on the SimScale platform. Users will learn about the three...","protected":false},"author":5,"featured_media":45399,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_crdt_document":"","inline_featured_image":false,"footnotes":""},"epkb_post_type_1_category":[1774],"epkb_post_type_1_tag":[1728,1733],"class_list":["post-23085","epkb_post_type_1","type-epkb_post_type_1","status-publish","has-post-thumbnail","hentry","epkb_post_type_1_category-fluid-analysis","epkb_post_type_1_tag-cad","epkb_post_type_1_tag-flow-volume-extraction"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/epkb_post_type_1\/23085","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/epkb_post_type_1"}],"about":[{"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/types\/epkb_post_type_1"}],"author":[{"embeddable":true,"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/comments?post=23085"}],"version-history":[{"count":0,"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/epkb_post_type_1\/23085\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/media\/45399"}],"wp:attachment":[{"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/media?parent=23085"}],"wp:term":[{"taxonomy":"epkb_post_type_1_category","embeddable":true,"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/epkb_post_type_1_category?post=23085"},{"taxonomy":"epkb_post_type_1_tag","embeddable":true,"href":"https:\/\/www.simscale.com\/wp-json\/wp\/v2\/epkb_post_type_1_tag?post=23085"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}