InthepresentpaperthevariationalsolutionofvelocityprofileforanincompressiblelaminarandfullydevelopedflowinisoscelestriangularductsisderivedbyapplyingtheKantovorichmethod.Thetheoreticalandexperimentalresultsofpressurelossarealsogiven.Thevelocitydistributionmodel,additionalpressurelosscoefficientandcalculatingmethodofinletlengthintheentranceregionofisoscelestriangularductsarealsoderived,whicharesuitableforvariouskindsofvertexangles.Thecalculationsandexperimentsarealsoperformedfortwomodels:theisoscelestriangularchannelswithvertexangles2α=45.1°and2α=60°.Comparisonsaremadebetweenthetheoreticalanalysisinthispaperandthoseoftheotherauthors.Itcanbeseenthatthepresentanalyticalresultisofhigh.accuracyandwidepracticability,andagreeswellwiththeauthors’experiment.
