MAPPING SPATIAL DISTRIBUTION OF FLUID FLOWS

THE VELOCITY OF SOUND IN A FLUID IS INFLUENCED BY TEMPERATURE, DENSITY, AND FLUID VELOCITY. THE RECENTLY DEVELOPED TECHNIQUE OF ULTRASONIC TOMOGRAPHY CAN PROVIDE A TWO-DIMENSIONAL MEASUREMENT OF THE ULTRASONIC VECTOR VELOCITY DISTRIBUTION IN A PLANE DEFINED BY A RING OF TRANSDUCERS ENCLOSING THE FLOW. THE TIME-OF-FLIGHT (TOF) IN THE PLANE OF INTEREST IS MEASURED ALONG ALL POSSIBLE PATHS AND INVERTED BY A COMPUTER TO FORM THE VELOCITY MAP. BY PLACING A SECOND RING OF TRANSDUCERS DOWNSTREAM FROM THE FIRST RING, AND MEASURING THE TOF BETWEEN ALL TRANSDUCER PAIRS, IT IS POSSIBLE TO RECONSTRUCT THE THREE-DIMENSIONAL VECTOR VELOCITY FIELD IN A MOVING FLUID. FURTHERMORE, IT IS POSSIBLE TO SEPARATE THE INTRINSIC LOCAL PROPAGATION VELOCITY FROM THE VECTOR VELOCITY OF THE FLUID. SINCE THE LOCAL VELOCITY CAN BE RELATED TO FLUID DENSITY, IT SHOULD BE POSSIBLE TO CALCULATE MASS FLOW ON A LOCAL AS WELL AS GLOBAL BASIS. INCLUSION OF CONSTRAINTS SUCH AS CONSERVATION OF ENERGY, MOMENTUM, MASS AND CONTINUITY PROVIDE MEANS FOR INCREASING THE ACCURACY OF SUCH RECONSTRUCTIONS. IF THE FLUID IS KNOWN TO BE HOMOGENEOUS, ANY VARIATION IN LOCAL SPEED OF SOUND MAY BE RELATED TO TEMPERATURE. IT IS, THEREFORE, POSSIBLE TO PROVIDE A COMPLETE THREE-DIMENSIONAL TEMPERATURE DISTRIBUTION IN ADDITION TO THE VECTOR VELOCITY OF THE FLUID.