Acoustically controlled rheological valve for thixotropic fluid flow control

A method for controlling a flow of a thixotropic fluid through a fluid conduit, comprising:

• providing a constriction in said fluid conduit, said constriction having a smooth bore channel with no mechanical member configured to move within the smooth bore channel to open or close the smooth bore channel;
• filling said smooth bore channel with said thixotropic fluid having a yield stress and selecting a smooth bore length and diameter and an available driving pressure in the fluid conduit such that a wall shear stress at the smooth bore produced by the available driving pressure is less than the yield stress in the absence of applied acoustic energy, thereby blocking flow through the bore channel in a normally-closed state;
• selectively applying focused acoustic energy to the thixotropic fluid within said bore channel at an intensity sufficient to generate local shear rates exceeding a yield-stress threshold of the thixotropic fluid having a yield stress, thereby transitioning the fluid within at least a portion of the bore channel from a gel state to a liquid state of substantially reduced viscosity and enabling flow through the bore channel under the available driving pressure without movement of any mechanical member within the bore;
• and
• selectively removing the applied acoustic energy, whereby the thixotropic fluid within the bore channel passively recovers from the liquid state to the gel state through thixotropic restructuring and flow through the bore channel is again blocked to restore the normally-closed state.

A fluid processing system comprising:

• a plurality of fluid processing chambers arranged in a series flow path;
• a plurality of acoustic chokes, each acoustic choke positioned between adjacent ones of said processing chambers and each comprising a smooth bore constriction having no mechanical member configured to move within the smooth bore channel to open or close the smooth bore channel and one or more ultrasonic transducer elements positioned to direct focused acoustic energy into a thixotropic fluid within the smooth bore channel;
• and
• a control system connected to the ultrasonic transducer elements of each of said acoustic chokes and configured to apply acoustic energy selectively to individual ones of said acoustic chokes to control flow of the thixotropic fluid through the series flow path;
• wherein the thixotropic fluid flows between adjacent fluid processing chambers only when acoustic energy is applied to the intervening acoustic choke at sufficient intensity to transition the thixotropic fluid within the bore from a gel state to a liquid state and thereby permit flow under an available driving pressure, and flow is blocked when the focused acoustic energy is absent through passive gel-state recovery of the thixotropic fluid within the bore to provide a normally-closed state without movement of any mechanical member in the smooth bore channel.