i am getting reverse flow at the outlet boundary.what should i do?does it affect the result?

Hi,

if your bound is not too close to what you study, it will not affect the results. So enlarge your domain of study or change of boundary type if possible.

if your outlet BC is pressure-outlet note that you do not need to set a BC since it's asked for backflow pressure i.e. a flow inter from the outlet which is the source of reverse flow.

Right!my outlet BC is pressure-outlet.u mean there is no need of setting outlet BC.

exactly