{"id":31690,"date":"2021-10-22T07:35:52","date_gmt":"2021-10-22T11:35:52","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=31690"},"modified":"2026-03-26T06:21:51","modified_gmt":"2026-03-26T10:21:51","slug":"aeroacoustics-cfd-lighthill-wave-model","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/aeroacoustics-cfd-lighthill-wave-model\/","title":{"rendered":"Aeroacoustics CFD &#8211; crafting the sound of silence for HVAC systems"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">The sound of Motor Valley<\/h2>\n\n\n\n<p>I live in the heart of the&nbsp;<a href=\"https:\/\/motorvalley.it\/en\/\" target=\"_blank\" rel=\"noreferrer noopener\">Italian Motor Valley<\/a>.&nbsp;With several famous luxury car brands, motorcycle manufacturers, and internationally renowned race circuits, it\u2019s a motorsport fanatic heaven. The common denominator between all those machines is their sound \u2013 wait listen\u2026 do you have any goosebumps yet?<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"Supercars in Maranello 2020 - VOL. 5 (Zonda S, 488 Pista, Monza SP2, 812 GTS, Roma, 812 GTO, SF90)\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/89FvULwBUCU?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<p>You\u2019d be forgiven for not noticing these supercars any longer after a while, there are so many driving around. In fact, what turns heads in this part of the world is\u2026 little (silent \u2013 woosh) electric cars\u2026<\/p>\n\n\n\n<p>As an&nbsp;electric vehicle&nbsp;owner,&nbsp;you get used to&nbsp;the silence&nbsp;very quickly. You actually come to appreciate the reduced audio&nbsp;levels sooner than you would believe.&nbsp;But, as if your brain couldn\u2019t rest yet&nbsp;&#8211; or maybe it\u2019s&nbsp;just an&nbsp;engineer\u2019s hard-wired brain&nbsp;that works like that &#8211; you start noticing the&nbsp;next&nbsp;noisy items.&nbsp;Hence, the new philosophy has to be to <a href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/adopt-a-people-centric-approach-to-electric-vehicle-sound-engineering\/\" target=\"_blank\" rel=\"noreferrer noopener\">adopt a people-centric approach to electric vehicle sound engineering<\/a>.&nbsp;<\/p>\n\n\n\n<p>What was masked before by a regular constant engine sound becomes&nbsp;distinct.&nbsp;Besides from the electric motor&nbsp;and&nbsp;the tires, there is one thing in particular that will catch your audio attention.&nbsp;It is the&nbsp;contribution from the&nbsp;Heat,&nbsp;Ventilation and Air Conditioning&nbsp;(HVAC)&nbsp;system&nbsp;that is rather clear when the windows are shut. Now don\u2019t&nbsp;tell me you thought we&nbsp;always ran&nbsp;with&nbsp;our windows&nbsp;down&nbsp;in Italy. It\u2019s not always nice and sunny. In fact, today it\u2019s cloudy,&nbsp;cold,&nbsp;and gloomy as is often the case in&nbsp;autumn&nbsp;in&nbsp;Pianura&nbsp;Padana:&nbsp;&nbsp;<\/p>\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=\"the Pianura Padana&#039;s fog\" width=\"640\" height=\"480\" src=\"https:\/\/www.youtube.com\/embed\/in6QSQqqR-0?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<h2 class=\"wp-block-heading\">Aeroacoustics CFD simulation&nbsp;<\/h2>\n\n\n\n<p>Noise generated by the air handling components in&nbsp;HVAC&nbsp;systems&nbsp;is a&nbsp;large&nbsp;contributor to interior cabin sound levels.&nbsp;CFD\u2019s input&nbsp;to the engineering of&nbsp;quieter&nbsp;HVAC systems&nbsp;resides in its ability to&nbsp;simulate&nbsp;aeroacoustics. The latter is the science of modeling the aerodynamics&nbsp;contribution&nbsp;to the generation of sound.&nbsp;&nbsp;<\/p>\n\n\n\n<p>Typically,&nbsp;you can choose from two&nbsp;simulation&nbsp;approaches:&nbsp;&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>The first one is the&nbsp;expensive&nbsp;but&nbsp;accurate&nbsp;high-resolution&nbsp;approach of Direct Noise Calculation&nbsp;(DNC). DNC is an aeroacoustics CFD method that consists in solving the&nbsp;full compressible, unsteady,&nbsp;flow field. Here the sound field is part of the flow solution.&nbsp;&nbsp;<\/li><li>The second one is a more pragmatic and cost-effective approach. Hybrid methods, which solve an additional equation for the sound based on a source term from the flow.&nbsp;&nbsp;<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Silent efficiency with hybrid aeroacoustics CFD: The Lighthill Wave model&nbsp; <\/h2>\n\n\n\n<p>In Simcenter STAR-CCM+ 2021.3&nbsp;we introduce&nbsp;the&nbsp;new&nbsp;Lighthill Wave model, part of this&nbsp;hybrid aeroacoustics&nbsp;family of&nbsp;models. Using an Acoustic Analogy method, it neglects the effect of the flow field on sound propagation. The&nbsp;Lighthill Wave&nbsp;model&nbsp;lets&nbsp;simulation analysts attain better results, faster. It allows you to&nbsp;study noise in regions where the contribution of the turbulent fluctuations and the influence of convection is neglectable. Quite adequate&nbsp;for HVAC&nbsp;systems, where&nbsp;the human ear (receiver) is relatively far in the quiescent zone from the HVAC vents (noise source).&nbsp;&nbsp;<\/p>\n\n\n\n<figure class=\"wp-block-video aligncenter\"><video controls poster=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/HVAC_Aeroacoustics_Lighthigh-Wave-Model.png\" src=\"https:\/\/videos.mentor-cdn.com\/mgc\/videos\/5400\/6985c1cd-505e-4282-a3d8-614950fcb917-en-US-video.mp4\"><\/video><figcaption>Aeroacoustics CFD of an HVAC system using the Lighthill Wave model<\/figcaption><\/figure>\n\n\n\n<p>This model does not separate flow and acoustics: the Lighthill Pressure illustrated above represents the acoustic and the hydrodynamic pressure.&nbsp;&nbsp;<\/p>\n\n\n\n<p>The&nbsp;Lighthill Wave model brings&nbsp;significant performance&nbsp;improvements&nbsp;compared to&nbsp;the&nbsp;existing hybrid aeroacoustics model,&nbsp;Acoustic Wave:&nbsp;&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Reduced time to results thanks&nbsp;to&nbsp;a less sensitive model. You can use coarser meshes;&nbsp;there is no spurious noise at&nbsp;mesh transitions. The pressure doesn\u2019t need to be converged as accurately, leading to&nbsp;fewer&nbsp;inner iterations&nbsp;required&nbsp;per time step.&nbsp;&nbsp;&nbsp;<\/li><li>Increased productivity with&nbsp;a simpler set-up; the&nbsp;Noise Source Weighting&nbsp;treatment,&nbsp;previously&nbsp;required for the Acoustic Wave solver, is not&nbsp;necessary any longer.&nbsp;&nbsp;<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"725\" height=\"461\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/Aeroacoustic-Power-Spectrum.png\" alt=\"Aeroacoustics CFD Power Spectrum\" class=\"wp-image-31842\" srcset=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/Aeroacoustic-Power-Spectrum.png 725w, https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/Aeroacoustic-Power-Spectrum-600x382.png 600w\" sizes=\"auto, (max-width: 725px) 100vw, 725px\" \/><figcaption><em>Results from Aeroacoustics CFD on&nbsp;elbow duct&nbsp;case &#8211;&nbsp;AIAA 2008-2902 and AIAA 2009-3352<\/em>&nbsp;<\/figcaption><\/figure><\/div>\n\n\n\n<p>Simcenter STAR-CCM+ offers various&nbsp;ways&nbsp;to analyze&nbsp;the instantaneous source field, such as&nbsp;its root mean square&nbsp;(RMS)&nbsp;illustrated below: \u2018Dynamic RMS of Lighthill Source (dB)\u2019.&nbsp;<\/p>\n\n\n\n<figure class=\"wp-block-video\"><video controls src=\"https:\/\/videos.mentor-cdn.com\/mgc\/videos\/5400\/c2c0039f-f2f1-4a93-bcf7-ae8fb3bdede9-en-US-video.mp4\"><\/video><figcaption>Noise sources in an HVAC system from aeroacoustics CFD <\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Aeroacoustics CFD out of the box&nbsp;&nbsp;<\/h2>\n\n\n\n<p>Engineering quieter HVAC systems&nbsp;is&nbsp;now&nbsp;simpler than ever&nbsp;by&nbsp;coupling&nbsp;the&nbsp;Lighthill Wave model&nbsp;with&nbsp;the outstanding templating capabilities of Simcenter STAR-CCM+.&nbsp;&nbsp;<\/p>\n\n\n\n<p>The ability to&nbsp;script&nbsp;workflows with Java&nbsp;has always been&nbsp;a&nbsp;panacea&nbsp;to explore design possibilities quickly&nbsp;and establish best practices with Simcenter STAR-CCM+.&nbsp;Nowadays, however,&nbsp;the level of templating&nbsp;enabled with&nbsp;global parameters,&nbsp;tags, filters, dynamic queries&nbsp;(<a href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/Simcenter-STAR-CCM-2019-1-the-Automation-Awards\/\" target=\"_blank\" rel=\"noreferrer noopener\">The Automation Awards<\/a>),&nbsp;geometry&nbsp;and simulation operations&nbsp;(<a href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/simcenter-star-ccm-2019-2-if-you-love-coding-dont-read\/\" target=\"_blank\" rel=\"noreferrer noopener\">If you love coding, don\u2019t read<\/a>)&nbsp;lets you&nbsp;automate&nbsp;the&nbsp;most specialist&nbsp;applications without needing to know code.&nbsp;Automation is in the DNA of Simcenter STAR-CCM+!&nbsp;&nbsp;<\/p>\n\n\n\n<p>But don\u2019t take my word for it, \u2018the proof is in the pudding\u2019. It\u2019s on this basis that we put our new Lighthill Wave model to the test. Taking a set of 3 HVAC duct geometries from scratch, we placed those in our well-oiled simulation template machine and cranked up the gears\u2026 or rather clicked a button\u2026<\/p>\n\n\n\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=\"276\" height=\"268\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/image-3.png\" alt=\"\" data-id=\"31699\" data-full-url=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/image-3.png\" data-link=\"https:\/\/blogs.sw.siemens.com\/simcenter\/image-3-26\/\" class=\"wp-image-31699\"\/><\/figure><\/li><li class=\"blocks-gallery-item\"><figure><img loading=\"lazy\" decoding=\"async\" width=\"240\" height=\"266\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/image-2.png\" alt=\"\" data-id=\"31698\" data-full-url=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/image-2.png\" data-link=\"https:\/\/blogs.sw.siemens.com\/simcenter\/image-2-36\/\" class=\"wp-image-31698\"\/><\/figure><\/li><\/ul><\/figure>\n\n\n\n<p><em>Tags applied&nbsp;to Geometry Parts: an effective simulation template configuration<\/em>&nbsp;<\/p>\n\n\n\n<p>The&nbsp;HVAC&nbsp;ducts attained&nbsp;out of the box&nbsp;agreement with experimental Sound Pressure Levels&nbsp;up to the target frequency of 3&nbsp;kHz.&nbsp;&nbsp;&nbsp;<\/p>\n\n\n\n<p>We then pushed the simulation set-up for performance compared to the base set-up (already faster than the existing Acoustic Wave model methodology) and achieved 3x speedups while retaining the ability to perform a broadband ranking of the ducts.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The sound of silence<\/h2>\n\n\n\n<p>Electric vehicles coupled to progress in acoustics engineering is doing so well to reduce sound levels in our cities that some regulators had to introduce artificial sounds for safety reasons:&nbsp;&nbsp;&nbsp;<\/p>\n\n\n\n<p><a href=\"https:\/\/gwacars.com\/new-noise-systems-to-stop-silent-electric-cars\/\" target=\"_blank\" rel=\"noreferrer noopener\">New noise systems to stop \u2018silent\u2019 electric cars and improve safety &#8211; GOV.UK (www.gov.uk)<\/a>&nbsp;<\/p>\n\n\n\n<p>Maybe this will set electric vehicles\u00a0further\u00a0apart and spin heads around over here\u00a0in this part of Italy\u00a0for many more years to come!\u00a0\u00a0And while you enjoy the silence continue to&#8230;<\/p>\n\n\n\n<p class=\"has-white-color has-text-color has-background has-large-font-size\" style=\"background-color:#009999\"><strong><a href=\"https:\/\/blogs.sw.siemens.com\/simcenter\/simcenter-star-ccm-2021-3-released-whats-new\/\" target=\"_blank\" rel=\"noreferrer noopener\">Read more about all top new features of Simcenter STAR-CCM+ 2021.3<\/a><\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Simcenter STAR-CCM+ 2021.3 offers a fast and reliable method for hybrid aeroacoustics CFD simulations\u202fof HVAC systems\u202fusing\u202fthe\u202fLighthill wave model. <\/p>\n","protected":false},"author":35193,"featured_media":31827,"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":[],"product":[513],"coauthors":[17723,18394],"class_list":["post-31690","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-product-updates","tag-computational-fluid-dynamics-cfd","product-simcenter-star-ccm"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2021\/10\/Static-Image-e1634898056203.png","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/31690","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\/35193"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/comments?post=31690"}],"version-history":[{"count":4,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/31690\/revisions"}],"predecessor-version":[{"id":31904,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/31690\/revisions\/31904"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/media\/31827"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/media?parent=31690"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/categories?post=31690"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/tags?post=31690"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/industry?post=31690"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/product?post=31690"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/coauthors?post=31690"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}