{"id":9462,"date":"2020-03-25T08:27:00","date_gmt":"2020-03-25T12:27:00","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=9462"},"modified":"2026-03-26T06:20:19","modified_gmt":"2026-03-26T10:20:19","slug":"may-the-magnetic-force-be-with-you","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/may-the-magnetic-force-be-with-you\/","title":{"rendered":"May the (magnetic) Force be with you"},"content":{"rendered":"\n<p>While you were watching the last episode of the<em> Star Wars<\/em> saga, I am sure you were wondering whether the notorious <em>Force<\/em> was a manifestation of electromagnetism. And I know you started wondering how to easily quantify the motion induced by magnetic forces on ferromagnetic bodies. Then you indulged in the thought that the mathematical description of those phenomena has in fact an elegant and compact form, however only trivial and overly simplified cases can be solved analytically. After all &#8211; you concluded, a bit irritated &#8211; simulating real life applications requires a numerical approach, <em>but which one?<\/em> This question haunted you during the whole movie and you could not fully enjoy the experience. I know, I&#8217;ve been there. Now listen.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Which applications?<\/h2>\n\n\n\n<p>It is indeed true that one of the most interesting manifestations of electromagnetism is the motion that a magnetic field induces on ferromagnetic bodies. Think of your fridge magnets and how they irresistibly stick onto the fridge once they are close enough to its surface. Think of a compass and how it is slowly hones in on the&nbsp;magnetic north pole no matter how you hold it. Or think of that science demonstration you might have seen at school, where iron filings&nbsp;stubbornly follow the magnetic field lines induced by a magnet.&nbsp; <\/p>\n\n\n\n<div class=\"wp-block-group\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<figure class=\"wp-block-gallery columns-2 is-cropped wp-block-gallery-1 is-layout-flex wp-block-gallery-is-layout-flex\"><ul class=\"blocks-gallery-grid\"><li class=\"blocks-gallery-item\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"413\" height=\"519\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/03\/256A-1_horseshoe-magnet-red-silver-iron-filings-AHD-1-1.jpg\" alt=\"Magnetic field horseshoe magnet\" data-id=\"10505\" data-full-url=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/03\/256A-1_horseshoe-magnet-red-silver-iron-filings-AHD-1-1.jpg\" data-link=\"https:\/\/blogs.sw.siemens.com\/simcenter\/?attachment_id=10505\" class=\"wp-image-10505\"\/><figcaption class=\"blocks-gallery-item__caption\">A classic horseshoe magnet attracting irons filings.<\/figcaption><\/figure><\/li><li class=\"blocks-gallery-item\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"718\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Ironpowder_on_magnet.jpg\" alt=\"\" data-id=\"9467\" data-full-url=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Ironpowder_on_magnet.jpg\" data-link=\"https:\/\/blogs.sw.siemens.com\/simcenter\/?attachment_id=9467\" class=\"wp-image-9467\" srcset=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Ironpowder_on_magnet.jpg 1024w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Ironpowder_on_magnet-600x421.jpg 600w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Ironpowder_on_magnet-768x539.jpg 768w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"blocks-gallery-item__caption\">Iron filings are a great way to visualize the 3D shape of magnetic field lines.<\/figcaption><\/figure><\/li><\/ul><\/figure>\n<\/div><\/div>\n\n\n\n<p>There is a plethora of industrial applications of magnetic-induced motion.  One of the earliest examples in history was long-distance telegraphy. Loudspeakers, magnetic door locks and actuators are more modern examples. Those devices share the same working principle: a current induces a magnetic field that acts on a ferromagnetic piece. As a result, the piece vibrates\/moves accordingly. So one can use this motion to send a signal \/ shut a door \/ switch a circuit on or off.  <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Why simulations?<\/h2>\n\n\n\n<p>Manufacturers want these devices to be reliable and robust (I suspect you want to be able to properly lock the door of your washing machine). Yet they need to cope with the cost of materials and the weight, size and inertia of the movable component. On top of that, they need to design a device that has a predictable behavior when driven with the right current and that fails in a predictable manner (e.g. when a large current is applied). To make things more complicated &#8211; due to&nbsp;motion-induced voltage &#8211;&nbsp;the current flowing through the device is influenced by the motion of the movable component. Which in turn depends on the current flowing through the device\u2026 How do you&nbsp;honor&nbsp;all those conflicting requirements? You won\u2019t go that far using good, old pencil and paper.&nbsp; <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Okay, but which tool?<\/h2>\n\n\n\n<p>Which brings me to your original question:&nbsp;<em>which numerical approach?<\/em>&nbsp;Since <a aria-label=\" (opens in a new tab)\" rel=\"noreferrer noopener\" href=\"https:\/\/www.plm.automation.siemens.com\/global\/en\/products\/simcenter\/STAR-CCM.html\" target=\"_blank\">versi<\/a><a aria-label=\"o (opens in a new tab)\" href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/star-ccm-2020-1\/\" target=\"_blank\" rel=\"noreferrer noopener\">on 2020.1<\/a>, Simcenter STAR-CCM+ can help&nbsp;you&nbsp;account for rigid motion induced by electromagnetic forces in a user-friendly way, including the back-reaction (i.e. motion-induced voltage). In <a href=\"https:\/\/community.sw.siemens.com\/s\/article\/Simcenter-STAR-CCM-2021-1-released-What-s-new\" target=\"_blank\" rel=\"noreferrer noopener\">version 2021.1<\/a> our electromagnetic offering has been <a href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/the-electric-circuit-editor-an-ancient-art-now-in-simcenter-star-ccm\/\">further improved<\/a>.<\/p>\n\n\n\n<p>The coupling between electromagnetic quantities and motion is now readily realized via the Dynamic Fluid-Body Interaction (DFBI) model. Some of you&nbsp;Simcenter&nbsp;STAR-CCM+ users may be already familiar with the DFBI model, which allows you to simulate the 6-DOF motion of solid bodies in response to forces exerted by surrounding continua (e.g. fluid pressure) or other additional forces like springs or gravity.<\/p>\n\n\n\n<p> Last, but not least, Simcenter STAR-CCM+ uses a vectorial finite element discretization of the electromagnetic equations. This is done in order to correctly model the spatial discontinuity of the magnetic permeability introduced by the ferromagnetic components (see also <a aria-label=\"this post (opens in a new tab)\" rel=\"noreferrer noopener\" href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/Thunders-circuit-breakers-and-the-challenges-of-multiphysics\/?repeat=w3tc\" target=\"_blank\">this blog post<\/a>).<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">An exemplary case<\/h2>\n\n\n\n<p>A <em>clapper type relay<\/em> is simulated below.  This kind of relay&nbsp;makes&nbsp;use of a clapper (armature) to displace the position of a movable contact. It can be used to open\/close a circuit and it works in the following way: An excitation coil induces a magnetic field. This acts on the armature, which moves. At the same time, a spring opposes this motion. Thus, when no pull is active, the spring brings the armature to its initial position.  In this way the relay can switch a circuit on (or off) by simply bringing together (or apart) the two contacts.  The YouTube animation below thoroughly explains the underlying working principle.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"645\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Relay_Parts.jpg\" alt=\"magnetic force clapper type relay example geometry \n\" class=\"wp-image-9482\" srcset=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Relay_Parts.jpg 1024w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Relay_Parts-600x378.jpg 600w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/1024px-Relay_Parts-768x484.jpg 768w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption><em>A simple clapper type relay. The coil induces a pulling force on the armature and displaces it.<\/em><\/figcaption><\/figure>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-4-3 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"working of electromagnetic relay\" width=\"640\" height=\"480\" src=\"https:\/\/www.youtube.com\/embed\/cunddFiQzrk?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<figure class=\"wp-block-video\"><video controls src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/01\/ClappingWithEddyCurrentsNoClippingLonger.mp4\"><\/video><figcaption><em>Half geometry of the clapper relay. Left: Electric current density magnitude<\/em>. <em>Right: Magnetic flux density magnitude<\/em>. <em>The magnetic motion induced voltage in the coil affects the time development of the coil current (see evolution of vector field color).<\/em> <em>Animation by Stefan Holst.<\/em><\/figcaption><\/figure>\n\n\n\n<p>The simple 1-DOF motion in the Simcenter STAR-CCM+ simulation above accounts for the following effects: electromagnetic forces, a torsional spring and gravity.  Similar geometries have been extensively studied in literature (see for instance <a rel=\"noreferrer noopener\" href=\"https:\/\/ieeexplore.ieee.org\/document\/105037\" target=\"_blank\">Kawase, Y., H. Kikuchi, and S. Ito.&nbsp;<em>IEEE transactions on magnetics<\/em>&nbsp;27.5 (1991): 4238-4241<\/a>).  <\/p>\n\n\n\n<p>The simulation shows how the voltage,  induced by the armature motion onto the excitation coil, affects the time development of the coil current. When the flap reaches its final, closed position, the induced voltage stops (due to lack of motion) and the coil current saturates to a DC level, as expected.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Helping simulation experts<\/h2>\n\n\n\n<p>It is interesting to&nbsp;study&nbsp;the&nbsp;effect&nbsp;that&nbsp;eddy-currents&nbsp;in the yoke&nbsp;have on&nbsp;the&nbsp;closing time.&nbsp;The simulations show that suppressing eddy-currents has a tangible effect on the closing time of the flap.&nbsp;When eddy-currents are included, the flap closes in&nbsp;5.14&nbsp;ms,&nbsp;otherwise&nbsp;in&nbsp;4.57&nbsp;ms.&nbsp;Eddy-currents&nbsp;make the motion&nbsp;slower, as expected, and this can be quantified.&nbsp;Moreover,&nbsp;after many switching operations,&nbsp;they can&nbsp;have a&nbsp;thermal impact. This might limit how often&nbsp;one&nbsp;can use the&nbsp;device.&nbsp;With the help of&nbsp;simulations, simulation engineers can decide&nbsp;for instance&nbsp;to change the material of the yoke in order to contain eddy-currents. Or they could design some form of lamination in order to suppress them.&nbsp;Or quantify the thermal impact of eddy-currents and decide they can live with that.<\/p>\n\n\n\n<p>I know your next question. The answer is: Yes, the results of&nbsp;this&nbsp;simulation show a very good match with the reference.&nbsp; <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Conclusions<\/h2>\n\n\n\n<p>Here you are, now you have the answer you were seeking. From now on you will be able to enjoy all future episodes of the <em>Star Wars<\/em> universe. Without being distracted by computational technicalities. You are welcome. <\/p>\n\n\n\n<p>PS: For you Computational Electromagnetics enthusiasts, feel free to watch our on-demand Webinar <a href=\"https:\/\/www.plm.automation.siemens.com\/global\/en\/webinar\/traction-motor-thermal-analysis\/70215\" target=\"_blank\" rel=\"noreferrer noopener\">Traction motor design using an integrated approach<\/a> and learn how the Simcenter Portfolio can help you design next generation electric machines.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>One of the most interesting manifestations of magnetic phenomena is the motion that a magnetic field induces on some bodies and materials. This effect is used in several industrial applications, but are you able to compute it?<\/p>\n","protected":false},"author":7209,"featured_media":10498,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[179],"tags":[242],"industry":[145],"product":[513],"coauthors":[1821],"class_list":["post-9462","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-product-updates","tag-computational-fluid-dynamics-cfd","industry-electronics-semiconductors","product-simcenter-star-ccm"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/03\/bb8-2558879_1920.jpg","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/9462","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/users\/7209"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/comments?post=9462"}],"version-history":[{"count":5,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/9462\/revisions"}],"predecessor-version":[{"id":26440,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/9462\/revisions\/26440"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/media\/10498"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/media?parent=9462"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/categories?post=9462"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/tags?post=9462"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/industry?post=9462"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/product?post=9462"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/coauthors?post=9462"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}