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Chemical Reactions

Acid Base Neutralization: HCl + NaOH --> NaCl

FLOW-3D has a chemical reaction model where multiple components can create a new concentration. For instance, in this example, 20 liters of 1M Hydrochloric Acid (HCl is mixed  with 2 milliliters of Sodium Hydroxide (NaOH) to make NaCL, or salt.

The mixing is accelerated with a rotating stirrer at 4 pi radians/sec (120 rpm). The images on the left display the concentrations of the acid (HCl), the base (NaOH) and the product (NaCl), respectively, while the image on the right is a 3D view of the base concentration. The stirrer is rotating at 4 radians per second. Simulation post-processed with FlowSight, coming soon in FLOW-3D v11.

Mixing & Chemical Reactions: Acid Base Neutralization: With and Without Stirrer

The simulation shown below with an active stirrer was compared against passive mixing (or diffusion only). Run passively, the reaction takes 437 seconds to reach a pH of 7. The stirrer accelerates the process to where it only takes 20 seconds at a rotation rate of 4 pi radians per second. The General Moving Object model was used to simulate the rotating mixer and the chemical reaction model was used to simulate the reactions. A time-dependent mass/momentum source introduces the base substance into the chamber.

With Stirrer

Without Stirrer


A stirrer accelerates the mixing to only 20 seconds at a rotation speed of 4 radians per second.

Simulation showing an acid-base chemical reaction that takes 2mL of NaOH and 20L of HCl 437 seconds to reach a pH of 7.