Classic Tutorial - Flow over cylinder in Ansys Fluent

on

In today's post, I would like to show you a classic tutorial with which beginners in CFD modeling should start. It is an analysis of the gas flow around the cylinder based on one laminar flow model.

Laminar flow over cylinder in Fluent 

At the beginning, I would like to introduce you  the boundary conditions that will be defined for the geometric model. Classically, we will deal with Inlet and Outlet. The geometry will be constrained by the walls and the obstacle in the form of a cylinder. You can see the arrangement of all BC's in the picture below.

BC's for flow over cylinder in Ansys Fluent

Our analysis is carried out in the transient mode, i.e. our parameters will change over time. Due to the low flow velocities (below Mach 0.3), we leave the Pressure-Based solver.

Solver and type of simulation definition in Ansys Fluent 

To make our problem as simple as possible (after all, this tutorial is dedicated to beginners), we set the flow as laminar (red frame). We also define our gas as linear, assuming a constant density independent of external factors (blue frame).

Viscosity model nad material properties definition 

We leave the definition of the boundary conditions in the default position for the cylinder and walls. So they will not be moving and there will be friction caused by the flowing gas (1, 4). For an inlet, we define an initial flow velocity of 80 m / s. Direction of gas movement perpendicular to the plane of the definition of this condition (2). We define an outlet using a pressure of 1 atm ABS. We might as well apply the outflow condition here for even more linearization of the problem (3).

BC's definition in Ansys Fluent 

In Solution Methods, we leave all simulation parameters unchanged. For such a simplified analysis, we do not need to use First Order for some solvers (1). As for the step size, due to the fact that we are dealing here with a fairly dynamic flow, we define the step size at 0.01 s. We set the number of iterations to 250, i.e. the total time of the analyzed flow phenomenon will be 2.5 s (2).

Simulation Settings in Ansys Fluent 

Below you can see the gas velocity distribution in the cylinder zone. As you can see, the "tail" behind the cylinder is quite straight. You can do a little experiment and do this analysis for the SST-k omega model, then your "tail" should start to ripple.

Velocity Distribution on Cylinder Zone - Ansys Fluent 

Below you can see the speed value at the reference point (it is marked in the second figure from the top). As you can see, the speed decreases with time. If we assume a sufficiently long simulation time, this value should start to stabilize for a small range of values.

Velocity Value at reference point (in function of time)  - Chart in Fluent 

If U want to read about more CFD tips and tutorials go links below 

https://howtooansys.blogspot.com/2021/11/investigation-of-influence-of_37.html

https://howtooansys.blogspot.com/2021/11/thermal-analysis-of-baffles-in-ansys.html

https://howtooansys.blogspot.com/2021/10/radiator-game-episode-3-modern-wall-cht.html




Comments

Post a Comment

Popular POSTS

Image

💥💥💥 How to handle with complex geometries (models) in Ansys Fluent?

ANSYS Fluent is a powerful software for simulating fluid dynamics and heat transfer problems. It can handle complex geometries (models) by using different meshing methods and workflows. Meshing is the process of dividing the geometry into small elements that can be used for numerical calculations. Depending on the type and quality of the geometry, you may need to use different meshing tools and techniques. One of the meshing methods available in ANSYS Fluent is the Watertight Geometry Workflow. This workflow is suitable for clean and watertight geometries, which means that there are no gaps, overlaps, or errors in the geometry. The Watertight Geometry Workflow can automatically generate a high-quality mesh for complex geometries, such as aircraft, cars, or turbines. You can also customize the mesh settings and refine the mesh in specific regions. To learn more about the Watertight Geometry Workflow, you can watch this video or take this course . Another meshing method available in ANS
Image

How to... fix "gui-domain-label: no domain selected" in Ansys Fluent and MEMERR in CFX

In today's post, we will deal with another error that may occur during the analysis. The error that is described below concerns Fluent and the wrong definition of user monitors that are displayed during simulation. These can be monitors concerning the average velocity in the domain volume, the values of the maximum temperatures of the solid domains, the average values of the heat transfer coefficient from the defined planes of the model, etc. Generally speaking, today's entry is about how to correctly define monitors and how to transfer them between subsequent analyzes. Example of "gui-domain-label" error in Fluent 
Image

Types of supports and examples - Ansys Static Structural

Supports are used to represent parts that are not present in the model but are interacting with it. Supports help truncate the domain, which helps in efficiently obtaining numerically accurate results without modeling parts of the geometry that are not of primary interest. There are different types of support available, among which you need to choose the appropriate one for your analysis. Here are some of the common types of supports and their explanations: - **Fixed Support**: This type of support constrains all the degrees of freedom of the selected entity (body, face, or edge). It means that the entity cannot move or rotate in any direction. Fixed support is equivalent to applying zero displacement to all directions. Fixed support is useful for modeling rigid connections or supports that do not allow any movement. For example, you can use fixed support to model a bolted joint or a clamped beam. - **Displacement Support**: This type of support specifies a zero or non-zero displacemen
Image

How to solve below problem in Ansys Fluent Divergence detected in AMG solver: temperature?

 The error message "Divergence detected in AMG solver: temperature" in Ansys Fluent indicates that the solver is having difficulty converging on a solution for the temperature field. Here are some steps you can take to address this issue: **Understanding the Errors:** * **Limited Absolute Pressure:**  The message "absolute pressure limited to 5.000000e+10 in 32400 cells on zone 2" suggests that the pressure values in some cells (zone 2) are reaching a very high limit. This could be due to an incorrect pressure boundary condition or a physical inconsistency in your model. * **Limited Turbulent Viscosity:**  The message "turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 2150 cells" indicates that the turbulent viscosity is being limited in some cells. This could be happening due to very high or low velocity gradients in those cells. **Troubleshooting Steps:** 1. **Check Boundary Conditions:**  Double-check your pressure boundary conditions fo