how to get reynolds number in a 2-D case
 

Hi'
how to get reynolds number in a 2-D case?
for example,a 3-d case ,I just want to simulate a cross section of it,use the K-EPSILON model ,which paramer could I used? when I use this formula DENSITY*VELOCITY*LENGTH/VISCOSITY ,just the length.

thank you!

Can you be more specific? Is the flow external or internal? In general you use a length scale that is appropriate to the case you are solving. You should typically know the characteristic length (the most important dimension of the calculation) no matter the case is 2D or 3D.

thank you for your reply.
It is a internal flow.the vessel and the mesh is in the enclosure.
how to fix 'the most important dimension of the calculation'? the sapce step in the direction of flow?or normal to it?
Yesterday,I found a method to slove this problem,the L=SQRT(DX*DX+DY*DY) DXand DY is the space step in XandY axis.