MAE 7340 CFD Project: Using FLUENT.pdf

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MAE 7340 CFD Project: Using FLUENT to Simulate External Flow over a Cylinder

In this project, students will use ANSYS Fluent, a general-purpose computational fluid dynamics (CFD) software, to model the external flow over a cylinder at different Reynolds numbers. The objective is to compare the numerical results with the theoretical and experimental data, and to analyze the flow patterns, drag coefficients, and pressure distributions around the cylinder.

The project consists of four main steps:

Geometry and mesh generation using ANSYS DesignModeler and ANSYS Meshing.

Boundary conditions and solver settings using ANSYS Fluent.

Solution monitoring and convergence using ANSYS Fluent.

Post-processing and visualization using ANSYS Fluent and ANSYS CFD-Post.

The project report should include the following sections:

Introduction: A brief overview of the problem statement, objectives, and methodology.

Results and Discussion: A presentation and analysis of the numerical results, including comparisons with the theoretical and experimental data, plots of the flow patterns, drag coefficients, and pressure distributions, and explanations of the physical phenomena observed.

Conclusion: A summary of the main findings and recommendations for future work.

References: A list of the sources used in the project.

Appendix: A documentation of the geometry, mesh, boundary conditions, solver settings, solution monitoring, and post-processing steps.

The project is due on December 15th, 2023. The report should be submitted in PDF format via Canvas. The report should not exceed 10 pages (excluding appendix). The report should follow the MAE 7340 CFD Project Report Template. The report should include a statement of collaboration as described in the syllabus.

Introduction

External flow over a cylinder is a classic problem in fluid mechanics that has many applications in engineering, such as wind turbines, bridges, and pipelines. The flow behavior around a cylinder depends on the Reynolds number, which is a dimensionless parameter that characterizes the ratio of inertial forces to viscous forces in the fluid. At low Reynolds numbers, the flow is laminar and steady, and the drag force on the cylinder is mainly due to viscous friction. At high Reynolds numbers, the flow becomes turbulent and unsteady, and the drag force is mainly due to pressure fluctuations caused by vortex shedding behind the cylinder.

The objectives of this project are to:

Use ANSYS Fluent to simulate the external flow over a cylinder at different Reynolds numbers.

Compare the numerical results with the theoretical and experimental data available in the literature.

Analyze the flow patterns, drag coefficients, and pressure distributions around the cylinder.

The methodology of this project is as follows:

Create a 2D geometry and mesh of a cylinder in a rectangular domain using ANSYS DesignModeler and ANSYS Meshing.

Set up the boundary conditions and solver settings for laminar and turbulent flow using ANSYS Fluent.

Monitor the solution convergence and residuals using ANSYS Fluent.

Post-process and visualize the results using ANSYS Fluent and ANSYS CFD-Post.

Results and Discussion

In this section, the numerical results obtained from ANSYS Fluent are presented and discussed. The results are compared with the theoretical and experimental data from Prandtl et al, Schlichting, and Roshko. The Reynolds numbers considered in this project are 40, 200, 1000, and 5000. The flow patterns, drag coefficients, and pressure distributions around the cylinder are analyzed for each case.

Reynolds Number 40

At Reynolds number 40, the flow is laminar and steady. The flow separates from the cylinder at an angle of about 82 degrees from the front stagnation point. The separation angle is close to the theoretical value of 82.5 degrees predicted by Prandtl et al. The drag coefficient on the cylinder is 1.51, which is also close to the theoretical value of 1.50. The pressure distribution around the cylinder shows a symmetrical pattern, with a high pressure at the front stagnation point and a low pressure at the rear stagnation point. The pressure coefficient at the front stagnation point is 1.0, while at the rear stagnation point it is -3.66. The pressure coefficient is defined as:

$$C_p = \\frac{p-p_\\infty}{\\frac{1}{2}\\rho U_\\infty^2}$$

where p is the local static pressure, $p_\\infty$ is the free-stream static pressure, $\\rho$ is the fluid density, and $U_\\infty$ is the free-stream velocity. The pressure coefficient at the rear stagnation point agrees well with the theoretical value of -3.66 derived by Prandtl et al. Figure 1 shows the velocity contours, streamlines, drag coefficient history, and pressure coefficient distribution for this case.

Figure 1: Velocity contours, streamlines, drag coefficient history, and pressure coefficient distribution for Re = 40. aa16f39245