how to do drivenLinearMotion set in pointDisplacement
 

Hi everyone，in short can anyone give an example of drivenLinearMotion？
below is its source code .H:
public solidBodyMotionFunction
{
// Private data

//- Name of the meshObject to dum CofG velocity
word CofGvelocity_;

//- Normal plane direction to restrict movement on a plane
vector normal_;

//- Uniform vector to follow
uniformDimensionedVectorField CofGvel_;

//- Last displacement
mutable vector displacement_;

and here is its .C:
Foam::septernion
Foam::solidBodyMotionFunctions::drivenLinearMotion ::transformation() const
{
scalar deltaT = time_.deltaT().value();

vector velocity = CofGvel_.value();

// Take out normal component
if (mag(normal_) > SMALL)
{
velocity = CofGvel_.value() - ((CofGvel_.value() & normal_)*normal_);
}

DebugInFunction << "Vel on plane :" << velocity << endl;

// Translation of centre of gravity with constant velocity
//const vector displacement = velocity*t;
displacement_ += velocity*deltaT;

my understanding is CofGvel is the object moving velocity and displacement is calculated each moment by +=velocity*deltaT，but when i set it and use pimpleFoam it report error like this：
--> FOAM FATAL ERROR:
Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Total flux : 1e-300
Specified mass inflow : 5.60342e-28
Specified mass outflow : 4.12536e-28
Adjustable mass outflow : 0


From bool Foam::adjustPhi(Foam::surfaceScalarField&, const volVectorField&, Foam::volScalarField&)
in file cfdTools/general/adjustPhi/adjustPhi.C at line 110.
and here‘s my setting of pointdisplacement：
cylinder
{
type solidBodyMotionDisplacement;
solidBodyMotionFunction drivenLinearMotion;
CofGvelocity haak;
normal (0 0 1);
CofGvel (this->db().time().value() this->db().time().value() 0);
displacement (0 0 0);
}
my purpose is to make the object move with velocity （t,t,0），can anyone tell how should i set it or please give me an example of it？there’s no such example in tutorial files.Other parts are ok，if i set it like this the whole case run without problem：
cylinder
{
type solidBodyMotionDisplacement;
solidBodyMotionFunction linearMotion;
velocity (1 2 0);
}
So anyone help plz..:confused: