that there are no short circuit flows or dead spots in the circulation pattern 21 within the tub interior 14 the tub or container bottom surface 22 may be sloped upwards slightly between a front wall 23 and the back wall 24 the angle of the bottom surface 22 may increase incrementally as the bottom surface 22 approaches the back wall 24 from the front wall 23 best seen in fig2 b the geometry of the container bottom surface 22 and interior 14 in combination with the placement of the injection nozzles 16 and discharge 20 creates the circulation flow or pattern 21 that rotates generally around an axis such as a substantially horizontal axis indicated by an arrow 26 the circulation pattern 21 has been discovered through simulation and experiments to activate the entire slurry volume and creates a strong flow at the tub walls of the interior portion 14 and advantageously produces the desired flow pattern 21 for a wide range of slurry 17 levels within the interior 14 advantageously providing consistent performance for a wide range of resident slurry volumes the range of slurry volumes may be a predetermined range of slurry volumes the circulation pattern 21 preferably allows the mix tub 10 to be substantially self cleaning in that few dead.