Compressible Flow Analysis in Curved Pipe Geometry - ANSYS Fluent CFD Training

Project Overview

This advanced CFD simulation examines compressible fluid dynamics within a curved pipe configuration, with particular emphasis on shock wave phenomenon analysis. The study involves air flow at 5°C entering the pipe inlet at Mach 0.9, creating significant pressure gradients that generate shock wave formations. To accurately resolve these high-gradient flow regions, adaptive mesh refinement techniques are employed using ANSYS Fluent’s gradient adaptation capabilities.

Geometry and Mesh Generation

Geometric Modeling

The three-dimensional pipe geometry was developed using Design Modeler software, featuring a curved pipe configuration with a 30mm internal diameter. The bent geometry design creates the necessary conditions for compressible flow effects and shock wave development.

Computational Grid Development

Initial mesh generation was performed using ANSYS Meshing software, producing an unstructured tetrahedral grid containing 191,479 computational elements. Following the implementation of gradient-based mesh adaptation techniques, the refined grid expanded to 1,450,983 elements, providing enhanced resolution in critical flow regions with steep gradients.

Simulation Methodology

Solver Configuration

The analysis employs a density-based computational approach specifically designed for compressible flow applications. The simulation is executed in transient mode to capture the temporal evolution of shock wave phenomena and pressure wave propagation through the curved pipe geometry.

Turbulence Modeling

The K-Omega SST viscous model is implemented to accurately predict fluid behavior, particularly in near-wall regions where viscous effects become significant in compressible flow conditions.

Results and Analysis

Flow Conditions and Shock Formation

Air enters the pipe system at Mach 0.9 velocity and 5°C temperature, encountering severe pressure reduction at the pipe curvature. This phenomenon manifests as shock wave formation, requiring high-resolution computational grids for accurate simulation.

Mesh Quality Considerations

While optimal y-plus values below unity are recommended for accurate near-wall flow resolution, the initial coarse tetrahedral mesh configuration could not satisfy this criterion. Consequently, gradient adaptation techniques were implemented to refine mesh density in regions exhibiting elevated y-plus values.

Pressure Distribution Results

The simulation results demonstrate approximately 120 kPa pressure reduction along the flow path, creating substantial variable distribution throughout the pipe geometry. The pressure contours clearly illustrate the shock wave structure and its impact on the overall flow field characteristics.