本算例采用的是气液两相流，想要给空气相加一个速度边界条件，而水相不加这个边界条件，下面给出的这个边界条件是空气相的，是依时的边界条件，按照网站上相似的做法编了以下，但是始终出现如下错误。请各位老师同学有时间帮忙解答一下，非常感谢！
下面是边界条件：
下面是报错的内容：
--> FOAM FATAL ERROR: request for volVectorField U from objectRegistry region0 failed available objects of type volVectorField are 8 ( HbyA.air U.air U.water U.air_0 KdUByA.air U.water_0 KdUByA.water HbyA.water ) From function const Type& Foam::objectRegistry::lookupObject(const Foam::word&) const [with Type = Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh>] in file /home/dyfluid/OpenFOAM/OpenFOAM-8/src/OpenFOAM/lnInclude/objectRegistryTemplates.C at line 211. FOAM aborting #0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::error::abort() at ??:? #2 Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> const& Foam::objectRegistry::lookupObject<Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> >(Foam::word const&) const in "/home/dyfluid/OpenFOAM/OpenFOAM-8/platforms/linux64GccDPInt32Opt/bin/multiphaseEulerFoam" #3 Foam::totalPressureFvPatchScalarField::updateCoeffs() at ??:? #4 Foam::fvMatrix<double>::fvMatrix(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::dimensionSet const&) in "/home/dyfluid/OpenFOAM/OpenFOAM-8/platforms/linux64GccDPInt32Opt/bin/multiphaseEulerFoam" #5 ? in "/home/dyfluid/OpenFOAM/OpenFOAM-8/platforms/linux64GccDPInt32Opt/bin/multiphaseEulerFoam" #6 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #7 ? in "/home/dyfluid/OpenFOAM/OpenFOAM-8/platforms/linux64GccDPInt32Opt/bin/multiphaseEulerFoam" Aborted (core dumped)