💥💥💥 How to speed up convergence for steady state analysis in Ansys Fluent - 5 tips

There are several factors that can affect the convergence speed for steady state analysis in ANSYS Fluent, such as the mesh quality, the solver settings, the initial conditions, the boundary conditions, and the physical models. Here are some general tips that may help you to speed up your convergence¹²³:

• Check your mesh quality and refine it if necessary. A good mesh should have a high element quality, a low aspect ratio, and a smooth transition between different sizes. You can use the mesh adaption feature to refine the mesh in regions of high gradients or curvature.
• Choose the appropriate solver settings for your problem. For example, if you are simulating natural or mixed convection, you may need to use a lower convergence criteria for the energy equation (e.g., 1e-12) and turn on gravity and radiation models. You may also need to use a small velocity in the direction opposite to gravity as an initial condition for steady state problems. You can also adjust the under-relaxation factors (URF) for different equations to improve stability and convergence. A common choice is to use 0.7 for pressure and 0.3 for momentum.
• Use a good initial guess for your solution. You can use the patching feature to specify different values for different regions of your domain. You can also use a previous solution from a similar case or a coarser mesh as an initial guess. A good initial guess can reduce the number of iterations needed to reach convergence.
• Check your boundary conditions and make sure they are consistent and realistic. For example, if you are using a pressure outlet boundary condition, you may need to specify a backflow temperature or use an outflow boundary condition instead. You can also use a mass flow inlet boundary condition instead of a velocity inlet boundary condition if you have compressible flow or variable density flow.
• Choose the appropriate physical models for your problem. For example, if you are simulating turbulent flow, you may need to use a turbulence model that can capture the effects of buoyancy and wall functions. You can also use a coupled pressure-velocity solver instead of a segregated solver if you have high-speed flow or high-pressure gradients.

I hope these tips can help you to speed up your convergence for steady state analysis in ANSYS Fluent. 😊

What are the mechanics of how relaxation factors work in Ansys Fluent?

The relaxation factors in Ansys Fluent are parameters that control the update of the computed variables at each iteration. They are used to improve the stability and convergence of the solution process. The relaxation factors are based on the following formula:

xk+1 = w.xcal + (1-w).xk

where xk is the value of the variable at iteration k, xcal is the value calculated from the equation, and w is the relaxation factor. The relaxation factor can range from 0 to 2, but usually it is between 0 and 1. A relaxation factor of 1 means that the variable is fully updated with the calculated value, while a relaxation factor of 0 means that the variable is not updated at all. A relaxation factor between 0 and 1 means that the variable is partially updated with a weighted average of the previous and calculated values.

The relaxation factors can affect the speed and accuracy of the solution. A higher relaxation factor can increase the convergence rate, but it can also cause instability or divergence if it is too high. A lower relaxation factor can increase the stability, but it can also slow down the convergence or cause oscillations if it is too low. Therefore, choosing appropriate relaxation factors for different equations and problems is important for obtaining a good solution.

Ansys Fluent provides default values for the relaxation factors that are suitable for most cases. However, some problems may require adjusting the relaxation factors to achieve better convergence or stability. For example, some turbulent flows or high-Rayleigh-number natural-convection problems may need lower relaxation factors for pressure, momentum, energy, and turbulence equations. Conversely, some flows with constant density or weak coupling between temperature and momentum may allow higher relaxation factors for temperature equation.

You can set or change the relaxation factors for each equation in the Solution Controls task page under Under-Relaxation Factors. You can also click the Default button to restore the default values. For more details about how to specify solution controls in Ansys Fluent, you can refer to this course or this user’s guide. You can also watch some video tutorials (https://www.youtube.com/watch?v=gZc7eS1xcFU) (https://www.youtube.com/watch?v=PrSpOf-TXiE) on how to model different types of flows in Ansys Fluent. I hope this helps you understand how relaxation factors work in Ansys Fluent. 😊

💥💥💥 How to improve residuals in steady state simulation ( Ansys Fluent ) - 4 steps

 Residuals are the errors in the numerical solution of the governing equations for each variable, such as continuity, momentum, energy, and species. Residuals indicate how well the solution is converging to a steady state. Lower residuals mean a more accurate and stable solution¹.

There are several factors that can affect the residuals and the convergence of a steady state simulation in ANSYS Fluent, such as the mesh quality, the boundary conditions, the solver settings, and the physical models. Here are some general guidelines on how to improve residuals in steady state ANSYS Fluent ¹²:

• Check and improve the mesh quality: The mesh quality is very important for the accuracy and stability of the solution. You should use a fine mesh near the regions with high gradients, such as walls, corners, and curved surfaces. You should also use a smooth mesh transition between different regions and avoid skewed or distorted cells. You can use ANSYS Meshing or ANSYS Fluent Meshing to generate and check the mesh quality¹.
• Check and adjust the boundary conditions: The boundary conditions define the values or fluxes of the variables at the boundaries of the domain. You should use appropriate boundary conditions for your problem and make sure they are consistent with each other. For example, if you have a pressure inlet boundary condition, you should also have a pressure outlet boundary condition. You should also avoid specifying conflicting or unrealistic boundary conditions, such as a high velocity at a wall or a negative pressure at an outlet¹.
• Check and modify the solver settings: The solver settings control how ANSYS Fluent solves the governing equations for each variable. You should use appropriate solver settings for your problem and make sure they are compatible with each other. For example, if you have a compressible flow or a flow with large density variations, you should use a density-based solver instead of a pressure-based solver. You should also adjust the discretization schemes, the under-relaxation factors, and the convergence criteria to improve the accuracy and stability of the solution¹.
• Check and select the physical models: The physical models define how ANSYS Fluent accounts for the effects of turbulence, heat transfer, multiphase flow, chemical reactions, and other phenomena on the fluid flow. You should use appropriate physical models for your problem and make sure they are calibrated and validated with experimental or theoretical data. For example, if you have a turbulent flow or a flow with large Reynolds number, you should use a suitable turbulence model, such as k-epsilon or k-omega model¹.

I hope these tips help you to improve residuals in steady state ANSYS Fluent. If you want to learn more about residuals and convergence in ANSYS Fluent, you can read these chapters¹² in the user’s guide and theory guide. You can also watch these videos³⁴ to see some examples of improving residuals in ANSYS Fluent. Have a nice day! 😊

💥💥💥 What is time scale factor in Ansys Fluent for steady state analysis

The time scale factor is a parameter that controls the size of the time step used in the pseudo-transient approach for steady state simulations. The pseudo-transient approach is a method that stabilizes the numerics by adding a time derivative term to the governing equations and marching the solution in time until a steady state solution is reached¹.

The time scale factor can be either specified by the user or computed automatically by ANSYS Fluent. By default, ANSYS Fluent will compute the time scale factor based on the representative length scale and velocity scale of the flow, as well as the Courant number. The Courant number is a dimensionless number that measures the ratio of the physical time required for a fluid particle to cross a cell to the numerical time step².

The choice of the time scale factor depends on the type and characteristics of your fluid flow, such as the density variation, the flow regime, and the convergence criteria. Here are some general guidelines for choosing the time scale factor ²:

• If you have a constant-density flow or a flow with small density variations, you can use the default value that ANSYS Fluent computes for you. You can also adjust the Courant number to increase or decrease the time step size.
• If you have a variable-density flow or a flow with large density variations, such as natural convection or compressible flow, you should specify the time scale factor based on the outside pressure and temperature conditions. You can also use the Boussinesq approximation or the ideal gas law to calculate the time scale factor as a function of temperature and pressure.
• If you have a multiphase flow or a flow with multiple gas species and chemical reactions, you should specify the time scale factor based on the mass-weighted average of the time scales of each phase or species.

You can find more details about the time scale factor and its effects on different types of fluid flows in Chapter 13 of ANSYS Fluent Theory Guide². You can also watch some videos of ANSYS Fluent simulations using different values of time scale factor ³ . 

How to specify time scale factor for multiflows (multiphase) ? - for mass - weighted average 

The time scale factor is a parameter that controls the size of the time step used in the pseudo-transient approach for steady state simulations. The pseudo-transient approach is a method that stabilizes the numerics by adding a time derivative term to the governing equations and marching the solution in time until a steady state solution is reached¹.

To specify the time scale factor based on the mass-weighted average of the time scales of each phase or species, you need to follow these steps:

1. In the Solution panel, select Time Step Size and then click Edit… to open the Time Step Size dialog box.
2. In the Time Step Size dialog box, select Physical Timescale under Method. This will enable you to specify the time scale factor manually.
3. In the Physical Timescale field, enter the value of the time scale factor that you want to use in your problem. You can calculate the value of the time scale factor based on the mass-weighted average of the time scales of each phase or species using this formula ¹:

$$\text{<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhDvjNVGsBA8pjK4qDx2jAE7ONRUsCa1vvVZ43O6uThhwirRm8euRbjh-d4xmwUU2cjf6FdQTX8\_n5tK388PgAIaSNHNo9eWjoxgEZRvt-Cl2Him4hRoCMM\_F7\_jEjH-LZnuwcg7QuQcygJGTJ46r2c8ZMCn2gxpKDb8uyA2nz0-YO9yn5sWLvgn60XVvae" style="margin-left: 1em; margin-right: 1em;"><img data-original-height="217" data-original-width="544" height="205" src="https://blogger.googleusercontent.com/img/a/AVvXsEhDvjNVGsBA8pjK4qDx2jAE7ONRUsCa1vvVZ43O6uThhwirRm8euRbjh-d4xmwUU2cjf6FdQTX8\_n5tK388PgAIaSNHNo9eWjoxgEZRvt-Cl2Him4hRoCMM\_F7\_jEjH-LZnuwcg7QuQcygJGTJ46r2c8ZMCn2gxpKDb8uyA2nz0-YO9yn5sWLvgn60XVvae=w512-h205" width="512"></a></div>}$$

4. Click OK in the Time Step Size dialog box. ANSYS Fluent will use the specified time scale factor to calculate the size of the time step for your simulation.

You can find more details about the time scale factor and its effects on different types of fluid flows in Chapter 13 of ANSYS Fluent Theory Guide¹. You can also watch some videos of ANSYS Fluent simulations using different values of time scale factor ²³. 

💥💥💥 What is species model in Ansys Fluent and what is use for ? 🧐

Species model in Ansys Fluent is a feature that allows you to model the mixing and transport of chemical species by solving conservation equations describing convection, diffusion, and reaction sources for each component species¹. You can use this model to simulate non-reacting or reacting flows, with reactions occurring in the bulk phase, on wall or particle surfaces, or in the porous region². You can also choose different reaction mechanisms and rate formulations to suit your problem³.

Some examples of applications that use species model in Ansys Fluent are:

- Combustion modeling using finite-rate chemistry²

- Chemical vapor deposition (CVD) processes²

- Fuel cell modeling

- Electrochemical reactions

Source:

(1) ANSYS FLUENT 12.0 User's Guide - 33.3.17 Species Model Dialog Box - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node1036.htm.

(2) ANSYS FLUENT 12.0 User's Guide - 15. Modeling Species Transport and .... https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node512.htm.

(3) ANSYS FLUENT 12.0 Theory Guide - 7. Species Transport and Finite ... - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node126.htm.

How to define species model in Ansys ? 

To model species transport and finite-rate chemistry in Ansys Fluent, you need to follow these steps:

- Enable the **Species Transport** model in the **Species Model** dialog box. You can also choose the **Non-Premixed Combustion** model if you want to simulate turbulent reacting flow using the non-premixed combustion model¹.

- Define the **species** that are involved in your problem. You can add or remove species from the list of available species in the **Boundary Species** section of the **Species Model** dialog box¹.

- Define the **reactions** that occur in your problem. You can choose from different reaction mechanisms and rate formulations in the **Reactions** section of the **Species Model** dialog box¹. You can also specify the **reaction zones**, where the reactions take place, and the **reaction orders**, which determine how the reaction rates depend on the species concentrations².

- Define the **boundary conditions** for your problem. You can specify the **species mass fractions**, **temperature**, and **reaction rates** at the inlet, outlet, wall, or other boundaries².

- Initialize and run the calculation. You can monitor the **species mass fractions**, **temperature**, and **reaction rates** during the solution process².

Source: 

(1) ANSYS FLUENT 12.0 User's Guide - 33.3.17 Species Model Dialog Box - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node1036.htm.

(2) 15. Modeling Species Transport and Finite-Rate Chemistry - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node512.htm.

(3) 15. Modeling Species Transport and Finite-Rate Chemistry - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node512.htm.

(4) #Ansys Fluent Tutorial | Modeling Species Transport and Gaseous .... https://www.youtube.com/watch?v=HcX1t9EDpSs.

What are differences between species model and Euler model in Ansys Fluent

The species model and the Euler model are two different approaches for modeling multiphase flows in Ansys Fluent. The species model is used to model the mixing and transport of chemical species by solving conservation equations describing convection, diffusion, and reaction sources for each component species³. The Euler model is used to model the interpenetrating continua of different phases by solving a set of momentum and continuity equations for each phase².

Some of the differences between the species model and the Euler model are:

- The species model is suitable for non-reacting or reacting flows, with reactions occurring in the bulk phase, on wall or particle surfaces, or in the porous region³. The Euler model is suitable for granular (fluid-solid) flows or nongranular (fluid-fluid) flows, with coupling achieved through the pressure and interphase exchange coefficients².

- The species model shares a single set of momentum equations by the fluids, and tracks the volume fraction of each of the fluids in each computational cell³. The Euler model solves a separate set of momentum equations for each phase, and accounts for the phasic volume fractions that sum up to one².

- The species model requires the definition of species, reactions, reaction zones, and reaction orders³. The Euler model requires the definition of interphase drag, lift, wall lubrication, turbulent dispersion, and virtual mass forces².

Source: 

(1) ANSYS FLUENT 12.0 User's Guide - 15. Modeling Species Transport ... - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node512.htm.

(2) ANSYS FLUENT 12.0 Theory Guide - 16.2.1 Approaches to Multiphase Modeling. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node293.htm.

(3) ANSYS FLUENT 12.0 User's Guide - 33.3.17 Species Model Dialog Box - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node1036.htm.

😊😊😊 How to change workspace in Ansys Workbench (Design Modeler)? 😊😊😊

 If U want to change, for example background in Ansys Design Modeler, U only need follow two simple steps. Below You can find short instruction how to do it. 

1. First U need to open Ansys Workbench Workspace 

2. Click on Tools (red frame)  - and pick Options (1) 

3. Next click on Apperance  - Then U can change Graphic Style 

I think , that after changes, your workflow will be more efficient. 

Below U can find other instructions how to change workspace in Ansys Workbench

To change the workspace in DesignModeler ANSYS, you can follow these steps:

• Open Workbench and create a new project or open an existing one.
• Right-click on the Geometry cell and select DesignModeler as the geometry editor. If DesignModeler is not listed, you may need to install it separately from the ANSYS Student website.
• Double-click on the Geometry cell to launch DesignModeler. You will see a default workspace with a 3D view and a tree outline on the left.
• To customize the workspace, you can use the View menu to change the display options, such as grid, axes, units, etc. You can also use the Tools menu to access various tools, such as sketching, modeling, parameters, etc.
• To save the workspace settings, you can use the File menu and select Save Settings As. You can also load a previously saved workspace by selecting Load Settings.
• To exit DesignModeler and return to Workbench, you can use the File menu and select Exit.

I hope this helps you with your question. If you need more information, you can check out these web search results . 😊

To change the background color in ANSYS DesignModeler, you can follow these steps:

• Launch DesignModeler from Workbench by right-clicking on the Geometry cell and selecting DesignModeler as the geometry editor.
• In DesignModeler, go to the View menu and select Background Style. You can choose from Uniform, Gradient, or Image options.
• If you choose Uniform, you can select a single color for the background by clicking on the color box and choosing from the palette.
• If you choose Gradient, you can select two colors for the background by clicking on the color boxes and choosing from the palette. You can also adjust the gradient angle and intensity by dragging the sliders.
• If you choose Image, you can browse for an image file to use as the background. You can also adjust the image position, size, and transparency by dragging the sliders.
• To apply the changes, click OK. You can also save your settings for future use by clicking Save Settings As.

I hope this helps you with your question. If you need more information, you can check out these video tutorials.  😊

💥💥💥 #12steps Ansys Fluent Tutorial Rotating Fan in Steady State 🧐🧐🧐

 Below You can find two parts of tutorial  - how to model rotating fan in Ansys Fluent. The first episode is in Steady State  - frame motion model. 

What is Digital Twin in Ansys and capabilities of dedicated software for this Twin Builder

 A digital twin is a connected, virtual replica of an in-service physical asset that uses simulation and data to mirror the real-world experience of that product¹. A digital twin can be used for system design and optimization, predictive maintenance, and industrial asset management².

Ansys is a software company that provides simulation-based solutions for various engineering domains. Ansys Twin Builder is one of the products that Ansys offers for creating and deploying digital twin models². Ansys Twin Builder allows engineers to build, validate, and deploy simulation-based digital twins with hybrid analytics². Hybrid analytics combines machine learning and physics-based approaches to achieve more accurate predictions².

Some of the capabilities of Ansys Twin Builder are:

- It can integrate real-world data from sensors and IoT platforms with simulation models to create a digital twin that reflects the current state and behavior of the physical asset².

- It can run simulations faster and more efficiently using reduced-order models (ROMs) that capture the essential dynamics of the system without compromising accuracy².

- It can support various types of systems, such as fluid, structural, electromagnetic, thermal, and power systems, using Ansys' multidomain simulation expertise².

- It can validate the performance and reliability of the digital twin using Ansys' solver technology and model libraries².

- It can deploy the digital twin to any platform, such as cloud, edge, or on-premise, using Ansys' runtime capabilities and APIs².

You can find more information about Ansys Twin Builder on the [Ansys website](^2^) or read some case studies and examples on the [Fluid Codes website](^3^) or the [Finite Element Analysis website](^4^).

Source:

(1) Digital Twin Simulation-Based Software | Ansys. https://www.ansys.com/products/digital-twin.

(2) Ansys Twin Builder | Create and Deploy Digital Twin Models. https://www.ansys.com/products/digital-twin/ansys-twin-builder.

(3) Ansys Twin Builder | Create and Deploy Digital Twin Models. https://www.ansys.com/products/digital-twin/ansys-twin-builder.

(4) A working example of a Simulation-enabled Digital Twin. https://www.finiteelementanalysis.com.au/featured/simulation-enabled-digital-twin/.

(5) SIMULATION PRODUCT HANDPRINT: DIGITAL TWINS - Ansys. https://www.ansys.com/content/dam/amp/2022/july/asset-creation/esg-ebooks/ansys-esg-digital-twin.pdf.

What are the generał steps to build Digital Twin in Ansys Twin Builder ? 

The general steps to build a digital twin on Twin Builder Ansys are:

- Build your twin: You need to create a system-level simulation model of your physical asset using Ansys' multidomain simulation expertise and solver technology. You can also integrate third-party tools and 3D models within your system simulation using reduced-order models (ROMs), which are simplifications of 3D models that preserve the essential information and run faster²⁴.

- Validate your twin: You need to verify and validate the performance and reliability of your digital twin model using Ansys' model libraries and test scenarios. You can also compare the simulation results with real-world data from sensors and IoT platforms to calibrate and improve your model².

- Deploy your twin: You need to deploy your digital twin model to any platform, such as cloud, edge, or on-premise, using Ansys' runtime capabilities and APIs. You can also connect your digital twin with real-time data streams from your physical asset and monitor its operation and health remotely².

You can find more information about how to build a digital twin on Twin Builder Ansys on the [Ansys website](^2^) or watch some video tutorials on [YouTube](^1^) ²³.

Source: 

(2) Build, Validate and Deploy Simulation-Based Digital Twins with Ansys. https://www.youtube.com/watch?v=qAsTDoosc2o.

(3) How to Build a Digital Twin from a Systems Simulation | Ansys. https://www.ansys.com/blog/how-to-build-a-digital-twin-from-a-systems-simulation.

(4) Build, Validate and Deploy Simulation-Based Digital Twins with Ansys. https://www.youtube.com/watch?v=qAsTDoosc2o.