Accordingtothecharacteristicsofdeepwatertoptensionedrisers,asimplifiedmodelispresentedtopredictthemulti-modalresponseofvortex-inducedvibration(VIV)innon-uniformflowbasedonenergyequilibriumtheoryandtheexperimentaldatafromVIVself-excitedandforcedoscillationsofrigidcylinders.Theresponseamplitudeofeachmodeisdeterminedbyabalancebetweentheenergyfedintotheriseroverthelock-inregionsandtheenergydissipatedbythefluiddampingovertheremainders.Comparedwiththepreviouspredictionmodels,thismethodcantakefullyaccountoftheintrinsicnatureofVIVforlowmassratiostructuresonlock-inregions,addedmassandnonlinearfluiddampingeffect,etc.Moreover,itisthefirsttimetoproposetheaccuratecalculatingprocedureforVIVamplitudecorrectionfactorbysolvingenergyequilibriumequationandaclosedformsolutionispresentedforthecaseofariserofuniformmassandcross-sectionoscillatinginauniformflow.ThepredictedvaluesshowareasonableagreementwithVIVexperimentsofrisermodelsinsteppedandshearedcurrents.
