How to improve Velocity magnitude
 

Hi there, I have a 2d model of an open-channel flow. The max velocity predicted is 0.465 m/s but the experimental value is 0.4 m/s how can i improve this? Grid adaption? My inlet BC is velocity inlet and in the 'initialize'-'compute from' box i have input 0.2m/s for X and Y initial velocity, since this is the average velocity could this be changed to improve the velocity. Last thought, how about 'relaxation factor' under second-order discretization, would that help?