Estimation of the concentration boundary layer adjacent to a flat surface using computational fluid dynamics.

Area of Science:

• Pharmacokinetics and Drug Metabolism
• Computational Fluid Dynamics
• Preclinical Drug Development

Background:

• Dissolution-permeation (D/P) experiments are crucial for preclinical drug development, offering better predictability than traditional methods.
• Comparing in vitro drug absorption across different D/P setups is challenging due to inconsistent reporting of apparent permeability.
• A standardized method is needed to accurately characterize D/P devices and improve inter-study comparability.

Purpose of the Study:

• To develop and validate a computational fluid dynamics (CFD) approach for predicting the concentration boundary layer in D/P experiments.
• To enable accurate characterization of complex D/P apparatuses where analytical solutions are unavailable.
• To improve the predictability and comparability of in vitro drug absorption data.

Main Methods:

• Solving Navier-Stokes and continuity equations in 2D using MATLAB and COMSOL v6.1.
• Utilizing finite element methods to predict momentum and concentration boundary layers.
• Developing a MATLAB algorithm to calculate boundary layer edges based on Blasius boundary layer flow analysis.

Main Results:

• The developed methodology accurately estimated momentum and concentration boundary layers for high Schmidt numbers (Sc ~ 1000).
• Results showed good agreement with the Blasius solution (within 14%) and accepted Schmidt number correlations (within 6.6%).
• The CFD approach provides a reliable method for analyzing D/P devices.

Conclusions:

• The proposed CFD-based methodology enables precise characterization of concentration boundary layers in D/P experiments.
• This approach facilitates more accurate and comparable in vitro drug absorption assessments in preclinical development.
• The study provides a valuable tool for researchers working with complex D/P apparatuses.