As part of our comprehensive ANSYS FLUENT Course for Beginners, this second case study investigates the classical problem of flow over a flat plate, serving as a fundamental benchmark for understanding boundary layer phenomena and validating Computational Fluid Dynamics (CFD) simulations with analytical solutions. Following our the original modules, this research focuses on external flow characteristics over a flat plate, a well-documented example from Cengel’s fluid mechanics textbook [1] that highlights the actual application of CFD principles. Students will learn to validate numerical simulations against theoretical predictions by examining important parameters including boundary layer thickness (δ) and local skin friction coefficient (Cf). This builds on their basic knowledge of ANSYS FLUENT. This validation study not only reinforces fundamental fluid dynamics ideas, but it also gives students hands-on experience comparing CFD findings to analytical solutions, making it an excellent learning example for computational fluid dynamics beginners.

• Reference [1]: Cengel, Yunus, and John Cimbala. Ebook: Fluid mechanics fundamentals and applications (si units). McGraw Hill, 2013.

Figure 1: Transition of the laminar boundary layer on a flat plate into a fully turbulent boundary layer [1]

Simulation Process

The methodology focuses on simulating laminar flow over a flat plate using ANSYS FLUENT, following dimensions specified in Cengel’s textbook. The computational domain features a structured mesh with progressive refinement near the wall to accurately capture boundary layer phenomena. The simulation maintains laminar flow conditions, characterized by the Reynolds number equation:

Two key parameters are validated: the boundary layer thickness, calculated using ​:

and the local skin friction coefficient, determined by :

Figure 2: Structured grid over Flat plate for CFD Simulation

Post-processing

The comparison of CFD simulation results to analytical solutions shows great agreement, confirming the accuracy of our numerical approach. The CFD simulation produced a value of 0.000878034 for the local skin friction coefficient (Cf), which is just 1.6% different than the analytical respond of 8.64E-04. This little difference defends the mesh refinement approach used in the wall region, as well as the correct capture of velocity gradients within the boundary layer. The velocity contour display clearly depicts the progressive growth of the boundary layer along the flat plate, with typical velocity profiles visible via color gradients ranging from blue (low velocity) along the wall to red (free stream velocity) in the outer flow region.

Furthermore, the boundary layer thickness (δ) comparison reveals similarly encouraging results, with the CFD-predicted thickness of 7.25mm closely matching the analytical value of 7.7mm, representing a difference of approximately 5.8%. The velocity contour plot effectively demonstrates this boundary layer development, showing the gradual thickening of the boundary layer from the leading edge of the plate. The smooth transition in velocity profiles and the consistent growth of the boundary layer thickness along the plate length indicate proper resolution of the flow physics, particularly in the critical near-wall region where viscous effects dominate. These results confirm that our computational setup, including mesh density and solver settings, successfully captures the fundamental characteristics of laminar flow over a flat plate.

Figure 3: Boundary Layer establishment over a flat plate CFD Simulation