Unpredictable polymeric flow dynamics with reaction between HPAM and Al³⁺ by comparison between pre- and...

Area of Science:

• Polymer Science
• Fluid Dynamics
• Chemical Engineering

Background:

• Chemical reactions alter fluid properties and flow dynamics.
• Evaluating these changes typically involves comparing pre- and post-reaction fluid properties.
• Previous work showed this comparison is insufficient for certain polymeric reacting flows.

Purpose of the Study:

• To investigate unpredictable flow dynamics in a reacting polymeric system.
• To explore the influence of pH and aluminum nitrate concentration on flow behavior.
• To elucidate the mechanisms behind the transient appearance and disappearance of the Weissenberg effect.

Main Methods:

• Experiments involving partially hydrolyzed polyacrylamide (HPAM) solutions reacting with aluminum nitrate (Al(NO3)3).
• Simultaneous measurement of pH and stirring torque.
• Identification of dominant aluminum aqua complexes using the Henderson-Hasselbalch equation.

Main Results:

• The Weissenberg effect was observed to appear and disappear transiently under specific pH and Al(NO3)3 concentrations.
• Two distinct mechanisms for the disappearance of the Weissenberg effect were proposed.
• One mechanism is consistent with previous findings (Fe(NO3)3), while the other is novel for Al(NO3)3.

Conclusions:

• The study highlights the complexity of polymeric reacting flows where pre- and post-reaction property comparisons are inadequate.
• Novel mechanisms contributing to unpredictable flow dynamics were identified for aluminum nitrate systems.
• Findings advance the understanding of conditions leading to complex behaviors in reacting fluid systems.