A rack assembly includes a rack body and a jet generating device. The rack body is configured to hold a plurality of servers that are displaced from each other by a passageway. The jet generating device is disposed in the passageway and includes a partition wall, a proximal barrier, and a distal barrier. The partition wall is disposed to define an inflow path and an outflow path. When cooling air is drawn into the inflow path, the cooling air is blocked by the distal barrier such that the cooling air is forced to flow into the outflow path through internal ports of the partition wall to generate a plurality of cooling air jets, which impinge on and cool one of the servers.