A turbine rotor blade with a cooling air channel formed in a mid-chord region, the channel includes a number of rows of semi-circular shaped ribs that extend across the channel and open toward the blade tip. Adjacent ribs form metering and impingement passages that discharge a jet of cooling air against the rib above it. The open ends of the ribs form vortex generating passages in which the impingement cooling air flows into to form a vortex flow pattern in the cooling air.