A doubt with the time step size while running icoFoam to solve flow over a flat plate
 

I am trying to model the flow over a flat plate using icoFOAM. I have used blockMesh with no grading present to get initial results. I have been trying different time steps and have been getting Continuity errors on having a very low time step size. For example, I am able to obtain results if I use a time step of 0.005s, but I get the continuity error on having a time step of 0.0005s.


Could someone please explain the reason behind this.