facing high courant number while running the case in OpenFOAM

Hi,
I am trying to simulate the incompressible flow of water through a cylinder.The cylinder at its base have many small circular openings.I have made the mesh of required geometry through gmesh.But while executing the file in OpenFoam the courant number is becoming high.My pressure and velocity fields are as follows:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.x |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 2 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{ bottom
{
type fixedValue;
value uniform 1.4715;

}
top
{
type fixedValue;
value uniform 0;
}
wall1
{
type zeroGradient;
}
wall2
{
type zeroGradient;
}
wall3
{
type zeroGradient;
}
wall4
{
type zeroGradient;
}
}

// ************************************************************************* //

U FILE:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.x |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
bottom
{
type fixedValue;
value uniform (0 0 -.000004);
}

top
{
type fixedValue;
value uniform (0 0 0);
}

wall1
{
type zeroGradient;

}
wall2
{
type zeroGradient;
}
wall3
{
type zeroGradient;
}
wall4
{
type zeroGradient;
}
}

// ************************************************************************* //