[en] This report describes a series of tests to investigate fluid and thermal mixing in a transparent model of a PWR cold leg with high pressure injection and a downcomer. Test conditions were selected to approximate the mixing phenomena in a prototypical reactor geometry. Results include both transient temperature data and video movies of the cold leg mixing phenomena. Although the mixing phenomena in the cold leg vary substantially between the different tests, the temperature distribution on the pressure vessel side of the downcomer below the cold leg elevation is generally uniform