{"id":3073,"date":"2023-04-04T08:37:00","date_gmt":"2023-04-04T08:37:00","guid":{"rendered":"https:\/\/rosim-dff8c4e9aqhwepgs.norwayeast-01.azurewebsites.net\/?p=3073"},"modified":"2025-12-01T12:10:23","modified_gmt":"2025-12-01T12:10:23","slug":"sammenlikning-cw-doppler-og-krysskorrelasjon-vannforing","status":"publish","type":"post","link":"https:\/\/rosim.no\/en\/sammenlikning-cw-doppler-og-krysskorrelasjon-vannforing\/","title":{"rendered":"Sammenlikning CW doppler og krysskorrelasjon vannf\u00f8ringsm\u00e5lere"},"content":{"rendered":"<div data-elementor-type=\"wp-post\" data-elementor-id=\"3073\" class=\"elementor elementor-3073\">\n\t\t\t\t<div class=\"elementor-element elementor-element-261f40a60 e-flex e-con-boxed wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no e-con e-parent\" data-id=\"261f40a60\" data-element_type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-10d766c1 e-flex e-con-boxed wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no e-con e-child\" data-id=\"10d766c1\" data-element_type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-d3c54c6 elementor-widget elementor-widget-heading\" data-id=\"d3c54c6\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Rosim \u2013 Insights<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-36352869 elementor-widget elementor-widget-heading\" data-id=\"36352869\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Sammenlikning CW doppler og krysskorrelasjon vannf\u00f8ringsm\u00e5lere <\/h2>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-7c4c5aaf e-flex e-con-boxed wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no e-con e-parent\" data-id=\"7c4c5aaf\" data-element_type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-f6359a9 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no e-con e-child\" data-id=\"f6359a9\" data-element_type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-36d235e elementor-widget-divider--view-line elementor-widget elementor-widget-divider\" data-id=\"36d235e\" data-element_type=\"widget\" data-widget_type=\"divider.default\">\n\t\t\t\t\t\t\t<div class=\"elementor-divider\">\n\t\t\t<span class=\"elementor-divider-separator\">\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e2ef874 elementor-widget elementor-widget-image\" data-id=\"e2ef874\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"768\" height=\"310\" src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika1-2.webp\" class=\"attachment-large size-large wp-image-3693\" alt=\"Sammenligning CW Doppler\" srcset=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika1-2.webp 768w, https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika1-2-300x121.webp 300w\" sizes=\"(max-width: 768px) 100vw, 768px\" title=\"\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-bedf875 elementor-widget elementor-widget-text-editor\" data-id=\"bedf875\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>The Norwegian Water Resources and Energy Directorate (NVE) has published a guidance document for those who need measurement data for the planning, modelling, and design of stormwater measures.<\/p>\n<p>You can find the guide here:<br \/><a href=\"https:\/\/publikasjoner.nve.no\/veileder\/2023\/veileder2023_01.pdf\" target=\"_blank\" rel=\"noopener nofollow\">https:\/\/publikasjoner.nve.no\/veileder\/2023\/veileder2023_01.pdf<\/a><\/p>\n<p>Lothar D\u00f6ren is one of the co-authors of the guide. He previously headed the instrumentation and metering department and served as Head of Water and Wastewater (VA) for the City of Bielefeld in Germany, before moving to Norway and joining Rosim in 2018. At Rosim from 2018 to 2020, he helped develop Rosim\u2019s instrumentation and metering methods and solutions. As a senior engineer at NVE, he works on stormwater and urban hydrology.<\/p>\n<p>Among mobile cross-correlation flow meters, NIVUS offers the PCM4 and the newer NivuFlow Mobile 750. In connection with the work on the guide, a PCM4 flow meter was loaned by Rosim to NVE.<\/p>\n<p>NVE has tested the measuring equipment, and the guide describes the measurement principles and summarises the advantages and disadvantages.<\/p>\n<p>The principle of a continuous-wave (CW) Doppler meter is that the sensor emits sound waves at a constant frequency. The waves are reflected by particles and air bubbles in the water, producing a frequency shift that is used to determine the flow velocity.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-436f5a0 elementor-widget elementor-widget-image\" data-id=\"436f5a0\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"327\" height=\"222\" src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika7.webp\" class=\"attachment-large size-large wp-image-3704\" alt=\"\" srcset=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika7.webp 327w, https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika7-300x204.webp 300w\" sizes=\"(max-width: 327px) 100vw, 327px\" title=\"\" loading=\"lazy\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-12c1e1e elementor-widget elementor-widget-text-editor\" data-id=\"12c1e1e\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>The figure above shows a typical velocity profile for flow in a pipe. The velocity is lower near the pipe invert due to friction between the pipe and the water, then increases higher up in the water column. As the figure indicates, with a CW Doppler you cannot know which of the red particles is being measured\u2014the one with the lower velocity or the one with the higher velocity.<\/p><p><em>With a CW Doppler, it is not possible to determine where within the flow cross-section the particle reflecting the sound wave is located. <\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3498c6f elementor-widget elementor-widget-image\" data-id=\"3498c6f\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"1017\" height=\"650\" src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika5.webp\" class=\"attachment-large size-large wp-image-3702\" alt=\"Sammenlign med Figur 7-23.\" srcset=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika5.webp 1017w, https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika5-300x192.webp 300w, https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika5-768x491.webp 768w\" sizes=\"(max-width: 1017px) 100vw, 1017px\" title=\"\" loading=\"lazy\">\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-397c6e7 elementor-widget elementor-widget-text-editor\" data-id=\"397c6e7\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>The figure above, from NVE\u2019s guide, illustrates the principle of cross-correlation (digital pattern recognition). An ultrasonic pulse causes particles and air bubbles in the water to return a characteristic echo pattern. By repeating this at intervals of a few milliseconds, changes in particle position and their flow velocity can be determined at different levels (depths). Using this method yields a vertical velocity profile of the flow.<\/p><p>This is what makes cross-correlation, as described by NVE, deliver \u201csignificantly lower uncertainty than CW Doppler.\u201d<\/p><p>It is also noted that the CW Doppler meter is \u201cparticularly prone to error under surcharging or accelerated flow.\u201d NVE\u2019s guide further specifies that calibration is required for the CW Doppler measurement principle.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-1e405a90 e-flex e-con-boxed wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no e-con e-child\" data-id=\"1e405a90\" data-element_type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-2e8e97a7 e-flex e-con-boxed wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no e-con e-child\" data-id=\"2e8e97a7\" data-element_type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-69165c7e elementor-widget elementor-widget-heading\" data-id=\"69165c7e\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Latest posts<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-12df2214 elementor-widget-divider--view-line elementor-widget elementor-widget-divider\" data-id=\"12df2214\" data-element_type=\"widget\" data-widget_type=\"divider.default\">\n\t\t\t\t\t\t\t<div class=\"elementor-divider\">\n\t\t\t<span class=\"elementor-divider-separator\">\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5aae8883 wpr-grid-columns-1 wpr-grid-columns--tablet2 wpr-grid-columns--mobile1 wpr-item-styles-inner elementor-widget elementor-widget-wpr-grid\" data-id=\"5aae8883\" data-element_type=\"widget\" data-widget_type=\"wpr-grid.default\">\n\t\t\t\t\t<ul class=\"wpr-grid-filters elementor-clearfix wpr-grid-filters-sep-right\"><li class=\"wpr-pointer-none wpr-pointer-line-fx wpr-pointer-fx-none\"><span  data-filter=\"*\" class=\"wpr-grid-filters-item wpr-active-filter\">All Posts<\/span><em class=\"wpr-grid-filters-sep\"><\/em><\/li><li class=\"wpr-pointer-none wpr-pointer-line-fx wpr-pointer-fx-none\"><span   data-ajax-filter=\"[\"category\",\"hva-foregar\"]\" data-filter=\".category-hva-foregar\">What\u2019s happening?<\/span><em class=\"wpr-grid-filters-sep\"><\/em><\/li><li class=\"wpr-pointer-none wpr-pointer-line-fx wpr-pointer-fx-none\"><span   data-ajax-filter=\"[\"category\",\"innsikt\"]\" data-filter=\".category-innsikt\">Insights<\/span><em class=\"wpr-grid-filters-sep\"><\/em><\/li><\/ul><section class=\"wpr-grid elementor-clearfix\" 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data-advanced-filters=\"no\"><article class=\"wpr-grid-item elementor-clearfix post-3219 post type-post status-publish format-standard has-post-thumbnail hentry category-hva-foregar tag-hydraulisk-modellering tag-nedbormaler tag-nedborsmaler tag-nedborsmalere tag-vannforingsmaler tag-vannforingsmalere tag-vannforingsmalinger\"><div class=\"wpr-grid-item-inner\"><div class=\"wpr-grid-media-wrap wpr-effect-size-medium\" data-overlay-link=\"yes\"><div class=\"wpr-grid-image-wrap\" data-src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika1-3-1-1.webp\" data-img-on-hover=\"\"  data-src-secondary=\"\"><img decoding=\"async\" data-no-lazy=\"1\" src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/slika1-3-1-1.webp\" alt=\"Instrumentering av overl\u00f8p og nedb\u00f8rm\u00e5lere i samarbeid med Milj\u00f8- og Fluidteknikk (MFT)\" class=\"wpr-anim-timing-ease-default\" title=\"\"><\/div><div class=\"wpr-grid-media-hover wpr-animation-wrap\"><div class=\"wpr-grid-media-hover-bg  wpr-overlay-fade-in wpr-anim-size-large wpr-anim-timing-ease-default wpr-anim-transparency\" data-url=\"https:\/\/rosim.no\/en\/instrumentering-av-overlop-og-nedbormalere-i-samarbeid\/\"><\/div><\/div><\/div><div class=\"wpr-grid-item-below-content elementor-clearfix\"><h2 class=\"wpr-grid-item-title elementor-repeater-item-a1b13d0 wpr-grid-item-display-block wpr-grid-item-align-left wpr-pointer-none wpr-pointer-line-fx wpr-pointer-fx-fade\"><div class=\"inner-block\"><a target=\"_self\" href=\"https:\/\/rosim.no\/en\/instrumentering-av-overlop-og-nedbormalere-i-samarbeid\/\">Instrumentation of overflow structures and rain gauges, in collaboration with Milj\u00f8- og Fluidteknikk (MFT).<\/a><\/div><\/h2><\/div><\/div><\/article><article class=\"wpr-grid-item elementor-clearfix post-3517 post type-post status-publish format-standard has-post-thumbnail hentry category-innsikt tag-hydraulisk-modellering tag-nedbormaler tag-nedborsmaler tag-nedborsmalere tag-vannforingsmaler tag-vannforingsmalere tag-vannforingsmalinger\"><div class=\"wpr-grid-item-inner\"><div class=\"wpr-grid-media-wrap wpr-effect-size-medium\" data-overlay-link=\"yes\"><div class=\"wpr-grid-image-wrap\" data-src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/Picture1.png\" data-img-on-hover=\"\"  data-src-secondary=\"\"><img decoding=\"async\" data-no-lazy=\"1\" src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/Picture1.png\" alt=\"Bruk av blokkregn\" class=\"wpr-anim-timing-ease-default\" title=\"\"><\/div><div class=\"wpr-grid-media-hover wpr-animation-wrap\"><div class=\"wpr-grid-media-hover-bg  wpr-overlay-fade-in wpr-anim-size-large wpr-anim-timing-ease-default wpr-anim-transparency\" data-url=\"https:\/\/rosim.no\/en\/bruk-av-blokkregn\/\"><\/div><\/div><\/div><div class=\"wpr-grid-item-below-content elementor-clearfix\"><h2 class=\"wpr-grid-item-title elementor-repeater-item-a1b13d0 wpr-grid-item-display-block wpr-grid-item-align-left wpr-pointer-none wpr-pointer-line-fx wpr-pointer-fx-fade\"><div class=\"inner-block\"><a target=\"_self\" href=\"https:\/\/rosim.no\/en\/bruk-av-blokkregn\/\">Use of Block Rainfall<\/a><\/div><\/h2><\/div><\/div><\/article><article class=\"wpr-grid-item elementor-clearfix post-3209 post type-post status-publish format-standard has-post-thumbnail hentry category-innsikt tag-hydraulisk-modellering tag-modellering\"><div class=\"wpr-grid-item-inner\"><div class=\"wpr-grid-media-wrap wpr-effect-size-medium\" data-overlay-link=\"yes\"><div class=\"wpr-grid-image-wrap\" data-src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/post1-e1751352511615.webp\" data-img-on-hover=\"\"  data-src-secondary=\"\"><img decoding=\"async\" data-no-lazy=\"1\" src=\"https:\/\/rosim.no\/wp-content\/uploads\/2025\/07\/post1-e1751352511615.webp\" alt=\"CFD modellering av overl\u00f8p\" class=\"wpr-anim-timing-ease-default\" title=\"\"><\/div><div class=\"wpr-grid-media-hover wpr-animation-wrap\"><div class=\"wpr-grid-media-hover-bg  wpr-overlay-fade-in wpr-anim-size-large wpr-anim-timing-ease-default wpr-anim-transparency\" data-url=\"https:\/\/rosim.no\/en\/cfd-modellering-av-overlop\/\"><\/div><\/div><\/div><div class=\"wpr-grid-item-below-content elementor-clearfix\"><h2 class=\"wpr-grid-item-title elementor-repeater-item-a1b13d0 wpr-grid-item-display-block wpr-grid-item-align-left wpr-pointer-none wpr-pointer-line-fx wpr-pointer-fx-fade\"><div class=\"inner-block\"><a target=\"_self\" href=\"https:\/\/rosim.no\/en\/cfd-modellering-av-overlop\/\">CFD modelling of overflow structures<\/a><\/div><\/h2><\/div><\/div><\/article><\/section>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4ff4f8e0 elementor-widget elementor-widget-heading\" data-id=\"4ff4f8e0\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Category<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7e1806e1 elementor-widget-divider--view-line elementor-widget elementor-widget-divider\" data-id=\"7e1806e1\" data-element_type=\"widget\" data-widget_type=\"divider.default\">\n\t\t\t\t\t\t\t<div class=\"elementor-divider\">\n\t\t\t<span class=\"elementor-divider-separator\">\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-23dfd11 elementor-icon-list--layout-traditional elementor-list-item-link-full_width elementor-widget elementor-widget-icon-list\" data-id=\"23dfd11\" data-element_type=\"widget\" data-widget_type=\"icon-list.default\">\n\t\t\t\t\t\t\t<ul class=\"elementor-icon-list-items\">\n\t\t\t\t\t\t\t<li class=\"elementor-icon-list-item\">\n\t\t\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/rosim.no\/en\/hva-foregar\/\">\n\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-icon-list-icon\">\n\t\t\t\t\t\t\t<svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-check\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M173.898 439.404l-166.4-166.4c-9.997-9.997-9.997-26.206 0-36.204l36.203-36.204c9.997-9.998 26.207-9.998 36.204 0L192 312.69 432.095 72.596c9.997-9.997 26.207-9.997 36.204 0l36.203 36.204c9.997 9.997 9.997 26.206 0 36.204l-294.4 294.401c-9.998 9.997-26.207 9.997-36.204-.001z\"><\/path><\/svg>\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-icon-list-text\">What\u2019s happening?<\/span>\n\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<\/li>\n\t\t\t\t\t\t\t\t<li class=\"elementor-icon-list-item\">\n\t\t\t\t\t\t\t\t\t\t\t<a href=\"https:\/\/rosim.no\/en\/innsikt\/\">\n\n\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-icon-list-icon\">\n\t\t\t\t\t\t\t<svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-check\" viewbox=\"0 0 512 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M173.898 439.404l-166.4-166.4c-9.997-9.997-9.997-26.206 0-36.204l36.203-36.204c9.997-9.998 26.207-9.998 36.204 0L192 312.69 432.095 72.596c9.997-9.997 26.207-9.997 36.204 0l36.203 36.204c9.997 9.997 9.997 26.206 0 36.204l-294.4 294.401c-9.998 9.997-26.207 9.997-36.204-.001z\"><\/path><\/svg>\t\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t\t<span class=\"elementor-icon-list-text\">Insights<\/span>\n\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t<\/li>\n\t\t\t\t\t\t<\/ul>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"<p>Rosim &#8211; Innsikt Sammenlikning CW doppler og krysskorrelasjon vannf\u00f8ringsm\u00e5lere NVE har kommet ut med en veileder for de som har behov for m\u00e5ledata i forbindelse med planlegging, modellering og prosjektering av overvannstiltak. Du finner veilederen her:https:\/\/publikasjoner.nve.no\/veileder\/2023\/veileder2023_01.pdf Lothar D\u00f6ren er en av medforfatterne til veilederen. Han ledet i en periode m\u00e5leteknisk avdeling og var VA sjef i Bielefeld kommune i Tyskland f\u00f8r han kom til Norge og begynte \u00e5 jobbe i Rosim i 2018. I Rosim fra 2018 til 2020 var han med \u00e5 utvikle Rosim\u2019s m\u00e5letekniske metoder og l\u00f8sninger. Som senior ingeni\u00f8r i NVE arbeider han med overvann og urbanhydrologi. Av mobile vannf\u00f8ringsm\u00e5lere med krysskorrelasjon har NIVUS modellene PCM4 og den nyere versjonen NivuFlow Mobile 750. I forbindelse med arbeidet med veilederen ble det l\u00e5nt en PCM4 vannf\u00f8ringsm\u00e5ler fra Rosim til NVE. NVE har testet m\u00e5leutstyr og veilederen beskriver m\u00e5leprinsipper og oppsummerer fordeler og ulemper. Prinsippet for en CW (Continuous Wave) doppler m\u00e5ler er at sensoren sender ut lydb\u00f8lger med konstant frekvens. Lydb\u00f8lgene reflekteres fra partikler og luftbobler i vannet, og det gir et frekvensskift som benyttes til \u00e5 bestemme str\u00f8mningshastighet. Figuren over viser et typisk hastighetsprofil for vannstr\u00f8mmen i et r\u00f8r. Hastigheten er lavere n\u00e6rmere r\u00f8rbunn pga. friksjon mellom r\u00f8ret og vannet. S\u00e5 stiger hastigheten i vannet h\u00f8yere i vannprofilet. Som figuren viser, kan en med CW doppler ikke vite hvilken av de r\u00f8de partiklene en m\u00e5ler, den med lavere eller den med h\u00f8yere hastighet. Med CW doppler er det ikke mulig \u00e5 fastsl\u00e5 hvor i str\u00f8mtverrsnittet partikkelen som reflekterer lydb\u00f8lgen er. Figuren over fra NVE\u2019s veileder, viser prinsippet for krysskorrelasjon eller digital m\u00f8nstergjenkjenning. En ultralydpuls f\u00e5r partikler og luftbobler i vannet til \u00e5 returnere et karakteristisk ekkom\u00f8nster. Ved \u00e5 repetere dette med f\u00e5 millisekunder kan endring i partiklers posisjon og deres str\u00f8mningshastighet bestemmes i ulike niv\u00e5er. Med denne metoden f\u00e5r en da m\u00e5lt et vertikalt hastighetsprofil i vannstr\u00f8mmen. Det er dette som gj\u00f8r at krysskorrelasjon, som NVE beskriver det, gir \u00abbetydelig lavere usikkerhet enn CW Doppler\u00bb. Det beskrives ogs\u00e5 at CW Doppler m\u00e5leren blir \u00abspesielt feilutsatt ved oppstuing eller akselerert str\u00f8mning\u00bb. For CW Doppler m\u00e5leprinsippet er det ogs\u00e5 i NVE\u2019s veileder angitt at kalibrering kreves. Nyeste innlegg All Posts Hva foreg\u00e5r Innsikt Instrumentering av overl\u00f8p og nedb\u00f8rm\u00e5lere i samarbeid med Milj\u00f8- og Fluidteknikk (MFT) Bruk av blokkregn CFD modellering av overl\u00f8p Kategori Hva foreg\u00e5r Innsikt<\/p>","protected":false},"author":1,"featured_media":3079,"comment_status":"closed","ping_status":"open","sticky":false,"template":"elementor_header_footer","format":"standard","meta":{"_acf_changed":false,"site-sidebar-layout":"no-sidebar","site-content-layout":"","ast-site-content-layout":"full-width-container","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[13],"tags":[21,19,20,25,26,16,17,18],"class_list":["post-3073","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-innsikt","tag-nedbormaler","tag-nedborsmaler","tag-nedborsmalere","tag-nivuflow-750","tag-nivus","tag-vannforingsmaler","tag-vannforingsmalere","tag-vannforingsmalinger"],"acf":[],"_links":{"self":[{"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/posts\/3073"}],"collection":[{"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/comments?post=3073"}],"version-history":[{"count":39,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/posts\/3073\/revisions"}],"predecessor-version":[{"id":6247,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/posts\/3073\/revisions\/6247"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/media\/3079"}],"wp:attachment":[{"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/media?parent=3073"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/categories?post=3073"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rosim.no\/en\/wp-json\/wp\/v2\/tags?post=3073"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}