{"id":92679,"date":"2025-03-18T10:36:23","date_gmt":"2025-03-18T10:36:23","guid":{"rendered":"https:\/\/www.valrom.ro\/pipe-failure-gravitational-flow-calculation-algorithm\/"},"modified":"2025-09-02T11:33:36","modified_gmt":"2025-09-02T11:33:36","slug":"pipe-failure-gravitational-flow-calculation-algorithm","status":"publish","type":"page","link":"https:\/\/www.valrom.ro\/en\/pipe-failure-gravitational-flow-calculation-algorithm\/","title":{"rendered":"PIPE FAILURE \u2013 GRAVITATIONAL FLOW calculation algorithm"},"content":{"rendered":"

PIPE FAILURE – GRAVITATIONAL FLOW<\/h3><\/div>
Calculation of head loss in partially filled pipes (gravitational), using the Gauckler\u2013Manning\u2013Strickler equation<\/h6><\/div>

The pipe failure during gravity flow through a partially (or completely) full pipe occurs due to the internal friction of the fluid (viscosity) and with the wall. The algorithm is applicable for water or liquids with kinematic viscosity equal to it. <\/p>\n

Gauckler\u2013Manning\u2013Strickler Ecuation(*):<\/p>\n

where
\nv: average flow velocity in the section, [m\/s]\nk: conversion factor, its value is 1 when the equation has SI units, [m1\/3]\nn: Manning coefficient \u2013 \u200b\u200bdimensionless
\nRH: hydraulic radius, [m]\nSH: hydraulic slope \u2013 dimensionless
\nThe Manning coefficient is determined empirically and depends on the shape of the flow section, the nature of the wall material, the sinuosity of the route, etc. Usual values(**) for circular flow sections and straight routes, for different materials from which the pipe is made: <\/p>\n\n\n\n\n\n\n\n\n\n\n\n
\n

Material<\/b><\/p>\n<\/td>\n

\n

n<\/b><\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n

\n

Polyethylene (thermoplastic material)1<\/sup><\/a><\/p>\n<\/td>\n

\n

0,009\u00f70,015<\/p>\n<\/td>\n<\/tr>\n

\n

Cast iron<\/p>\n<\/td>\n

\n

0,012<\/p>\n<\/td>\n<\/tr>\n

\n

Co<\/span>rrugated steel<\/p>\n<\/td>\n

\n

0,022<\/p>\n<\/td>\n<\/tr>\n

\n

Cement<\/p>\n<\/td>\n

\n

0,012<\/p>\n<\/td>\n<\/tr>\n

\n

Ceramics<\/p>\n<\/td>\n

\n

0,014<\/p>\n<\/td>\n<\/tr>\n

\n

Brick and <\/span>mortar<\/p>\n<\/td>\n

\n

0,015<\/p>\n<\/td>\n<\/tr>\n

\n

Wood<\/p>\n<\/td>\n

\n

0,012<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\n

1) Valid value for clean water. For waste water the value used is 0.01 <\/span><\/p>\n<\/div>\n

The hydraulic radius is calculated with the formula:<\/p>\n

 <\/p>\n

where:
\nA: area of \u200b\u200bthe flow section, [m2]\nP: wetted perimeter of the flow section, [m]\nThe area of \u200b\u200bthe flow section and the wetted perimeter of the flow section are a function of the degree of filling and are calculated with the calculation formulas corresponding to the circle segment.
\nThe hydraulic slope is:<\/p>\n

 <\/p>\n

where:
\nSH: hydraulic slope, dimensionless
\nhi: pipe height at the beginning of flow, [m]\nhf: pipe height at the end of flow, [m]\nL: flow length, [m]<\/p>\n

If we take into account that the flow rate is a function of the flow velocity:<\/p>\n

 <\/p>\n

we can calculate the flow rate with the formula:<\/p>\n

 <\/p>\n

where:
\nQ: flow rate, [m3\/s]<\/p>\n

(*)
\nhttp:\/\/en.wikipedia.org\/wiki\/Manning_equation)
\nHandbook of PE pipe (http:\/\/plasticpipe.org\/publications\/pe_handbook.html), cap. 6, pag. 186
\n(**)
\nhttp:\/\/www.engineeringtoolbox.com\/mannings-roughness-d_799.html<\/p>\n<\/div><\/div><\/div><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":3,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"100-width.php","meta":{"inline_featured_image":false,"footnotes":""},"class_list":["post-92679","page","type-page","status-publish","hentry"],"yoast_head":"\nPIPE FAILURE \u2013 GRAVITATIONAL FLOW calculation algorithm - Valrom Industrie<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.valrom.ro\/en\/pipe-failure-gravitational-flow-calculation-algorithm\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"PIPE FAILURE \u2013 GRAVITATIONAL FLOW calculation algorithm\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.valrom.ro\/en\/pipe-failure-gravitational-flow-calculation-algorithm\/\" \/>\n<meta property=\"og:site_name\" content=\"Valrom Industrie\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/ValromIndustrie\/\" \/>\n<meta property=\"article:modified_time\" content=\"2025-09-02T11:33:36+00:00\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"6 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.valrom.ro\\\/en\\\/pipe-failure-gravitational-flow-calculation-algorithm\\\/\",\"url\":\"https:\\\/\\\/www.valrom.ro\\\/en\\\/pipe-failure-gravitational-flow-calculation-algorithm\\\/\",\"name\":\"PIPE FAILURE \u2013 GRAVITATIONAL FLOW calculation algorithm - 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