Is it obligatory to repeat the Dhuhr prayer if secretions are found after returning home, knowing that ablution was performed before leaving for university and it was not possible to repeat it?

If you see the discharge during the Asr time, it is attributed to the nearest time it is likely to have exited. If it is probable that it exited after the Dhuhr prayer, then your prayer is valid, and you are not required to repeat it. This is because the default for every new occurrence is to estimate it at the nearest time, unless you are absolutely certain that it exited before or during the prayer.