Numerical studies of the flow and heat transfer in a typical low aspect ratio channel, simulating the trailing-edge cooling cavity of a gas turbine airfoil, were performed. The CFD models consist of two adjacent channels with trapezoidal cross-sections, separated by a partition with eleven racetrack-shaped holes that created the crossover jets. Roughened target surfaces with four rib geometries (0o, 45o, 90o and 135o rib) were analyzed with two exit flow arrangements - flow exiting axially from the tip of target channel and flow exiting from a row of cooling holes along the trailing edge. The numerical studies were carried out with the standard k-ε, realizable k-ε and k-ω with shear stress transport (SST) turbulence models and the results were compared with the test data. The three turbulence models were found to give reasonable predictions of the flow field, while the k-ω-SST turbulence model gave best prediction for the heat transfer coefficients.