Design of a Rheometer for Time-Dependent Gel Rheology

Simulation of time-dependent rheological behavior in an advanced Computational Fluid Dynamics (CFD) environment revealed that inclusion of a structural parameter within a modified empirical power law expression is capable of predicting the flowcharacteristics of thixotropic gels. Validation of the CFD based predictions was completed using a combination of published AMCOM test data and thixotropic flow measurements within the open literature. To fully quantify the time-dependent properties ofgelled propellants, a pressure drop/flow rate rheometer capable of evaluating all possible gel-propulsion flow system components will be designed, fabricated, and operated during Phase II. Current gel rheological models will be refined and validated forgel flows between -40¿C and 70¿C and shear rates from 5,000 sec-1 to 200,000 sec-1. All gel propellant rheological tests will be conducted at the AMCOM Propulsion Directorate. The final empirical correlations will be: 1) implemented in a systemfluid-flow network solver in use by leading propulsion manufacturers and 2) compiled for publication in JANNAF proceedings. High fidelity numerical simulations will be utilized throughout Phase II to precisely account for temperature, Reynolds number,shear rate and geometric effects on the thixotropic behavior of gelled propellants in future tactical missile, DACS, upper stage and in-space propulsion systems.Once the rheology of gelled propellants is fully documented, programmatic development riskassociated with future DoD and NASA operational systems that could utilize gel propulsion will be significantly reduced. CFDRC has received significant interest from some of our food, cosmetic and chemical industry clients regarding application of theproposed rheometer and rheological models to address and possibly exploit thixotropic behavior exhibited within their production processes.