“…Numerical methods for FSI problem have been intensively studied during the past decades. Based upon mesh types, the FSI numerical methods can be broadly categorised into fitted-mesh methods (Heil 2004;Hecht and Pironneau 2017;Tanaka and Kashiyama 2006) and unfittedmesh methods (Peskin 2002;Zhang et al 2004;Baaijens 2001;Boffi and Gastaldi 2016;Kreissl and Maute 2012); based upon solving strategies, these numerical methods include partitioned/segregated methods (Küttler and Wall 2008;Degroote et al 2009Degroote et al , 2013Bazilevs et al 2013) and monolithic/fully coupled methods (Heil 2004(Heil , 2008Muddle et al 2012;Wang et al 2017Wang et al , 2020; and based upon solving variables, there are one-field (one velocity) methods (Wang et al 2017(Wang et al , 2019aHecht and Pironneau 2017) and multi-field (velocity, displacement and Lagrange multiplier) methods (Muddle et al 2012;Boffi et al 2015Boffi et al , 2016. In a recent study (Wang et al 2020), we proposed an energystable one-field monolithic method based on an ALE fitted mesh, which is adopted to derive the optimality condition for the FSI control formulation in this article.…”