💥💥💥 What is OptiSLang and what is use for ? 🧐

 OptiSLang is a software for process integration and design optimization, which enables the automation and streamlining of CAE-based simulations. OptiSLang connects with various Ansys tools for simulating different physics domains, such as fluid mechanics, structural mechanics, and optics. OptiSLang uses advanced artificial intelligence and machine learning algorithms to build optimal predictive models, which efficiently explore the design space and identify the best design configurations. OptiSLang allows engineers to make better decisions faster, leading to more innovative designs and shorter time to market .

What are the benefits of using OptiSLang?

Some of the benefits of using OptiSLang are:

- It can automate and streamline the simulation process by integrating multiple CAx tools and different physics domains into a holistic, multi-disciplinary approach to optimization¹.

- It can accelerate the search for the best and most robust design configuration by using state-of-the-art algorithms for design exploration, optimization, robustness and reliability analysis¹.

- It can leverage the latest artificial intelligence and machine learning technologies to build optimal predictive models, which efficiently explore the design space and identify the best design configurations¹².

- It can enable experts to easily create web applications that can be deployed to Ansys Minerva, allowing non-experts to run the application and carry out design studies as needed².

- It can reduce the time and cost of running thousands of designs by using neural networks and smart layout to automatically find the best configuration².

- It can extract the relation from design variables to results as behavior models, which can be implemented in system simulation as table or C-code³.

Source: 

(1) Ansys optiSLang | Process Integration & Design Optimization Software. https://www.ansys.com/products/connect/ansys-optislang.

(2) Top 3 New Features in Ansys optiSLang. https://www.ansys.com/en-gb/blog/top-3-new-features-in-ansys-optislang.

(3) Understand your Design - PRACE. https://materials.prace-ri.eu/340/1/robustDesignOptimization.pdf.

What are some use cases of OptiSLang?

Some use cases of OptiSLang are:

- Process integration and design optimization: OptiSLang can automate and streamline the simulation process by integrating multiple CAx tools and different physics into a holistic, multi-disciplinary approach to optimization. OptiSLang can accelerate the search for the best and most robust design configuration by using state-of-the-art algorithms for design exploration, optimization, robustness and reliability analysis¹.

- Reduced-order modeling: OptiSLang can leverage the latest artificial intelligence and machine learning technologies to build optimal predictive models, which efficiently explore the design space and identify the best design configurations. OptiSLang can reduce the time and cost of running thousands of designs by using neural networks and smart layout to automatically find the best configuration¹².

- Model calibration: OptiSLang can extract the relation from design variables to results as behavior models, which can be implemented in system simulation as table or C-code³. OptiSLang can also calibrate these models by comparing them with experimental data and adjusting the parameters accordingly².

- Ansys Minerva integration: OptiSLang can enable experts to easily create web applications that can be deployed to Ansys Minerva, allowing non-experts to run the application and carry out design studies as needed. Ansys Minerva is a platform that enables collaboration, data management, and process automation across the entire product lifecycle².

- Advanced reliability methods: OptiSLang can help engineers make a safety statement for complex systems such as Level 3 autonomous driving assistance systems (ADAS) using scenario-based simulation. OptiSLang can perform uncertainty quantification and reliability analysis based on advanced methods such as Subset Simulation, Importance Sampling, or Line Sampling, which are more efficient and robust than Monte Carlo Sampling.

Source: 

(1) Ansys optiSLang | Process Integration & Design Optimization Software. https://www.ansys.com/products/connect/ansys-optislang.

(2) Mastering Ansys optiSLang: 5 Useful Methods for Reusing Existing ... - PADT. https://www.padtinc.com/2022/09/27/ansys-optislang-reusing-results/.

(3) Ansys + Daimler. https://www.ansys.com/content/dam/amp/2021/december/quick-request/optislang-case-study/Ansys-Daimler-Case-Study.pdf.

How can I get a license for OptiSLang?

To get a license for OptiSLang, you need to contact Ansys or one of its authorized partners and request a trial or purchase a subscription. You can find more information about the pricing and packaging of OptiSLang on the Ansys website¹. According to the website, there are two license options for OptiSLang: premium and enterprise. The premium license option allows you to run up to four design point variations concurrently, while the enterprise license option allows you to run up to eight design point variations for a design of experiments (DoE) study³. You also need to have a compatible Ansys product license, such as Ansys Fluent, Ansys Mechanical, or Ansys SPEOS, to use OptiSLang with those tools³.

Source: 

(1) Ansys optiSLang | Process Integration & Design Optimization Software. https://www.ansys.com/products/connect/ansys-optislang.

(2) Top 3 New Features in Ansys optiSLang. https://www.ansys.com/blog/top-3-new-features-in-ansys-optislang.

(3) optislang licensing - Ansys Learning Forum. https://forum.ansys.com/forums/topic/optislang-licensing-2/.

(4) Optislang Licensing - Ansys Learning Forum. https://forum.ansys.com/forums/topic/optislang-licensing/.

(5) Download NSYS optiSLang 2022 R1 Win64 full license forever. http://clickdown.org/download-nsys-optislang-2022-r1-win64-full-license-forever/.

💥💥💥 What is ROM Builder in Ansys Workbench and what is it for?

 ROM Builder is a tool that allows you to create reduced order models (ROMs) from your computational fluid dynamics (CFD) simulations in Ansys Workbench. ROMs are simplified representations of complex systems that can capture the essential behavior of the system with much less computational cost. ROMs can be used for various purposes, such as design optimization, parameter studies, system simulation, digital twins, and real-time control¹.

To build a ROM, you need to run a number of design points through a solver. The results from these runs are then combined into a ROM using Ansys DesignXplorer’s 3D ROM builder. These ROMs can then be combined into a system simulation, or digital twin, using Ansys Twin Builder¹.

ROM Builder is available for Fluent systems in Ansys Workbench. You can set up and build a ROM by defining the input parameters, output variables, and design points in the ROM Builder component. You can also export the ROM in standard formats, such as FMU or ROMZ, that can be imported into other software tools².

If you want to learn more about how to use ROM Builder in Ansys Workbench, you can watch some video tutorials here, here, or here. You can also read some articles here, here, or here. I hope this helps you understand what ROM Builder is and what it is for. 😊

How to define ROM Builder for Ansys Fluent?

To define ROM Builder for Ansys Fluent, you need to follow these steps:

• Drag and drop a 3D ROM system from the Design Exploration toolbox in Workbench to your Fluent project¹.
• Define the input parameters that you want to vary in your ROM, such as boundary conditions, material properties, or operating conditions. You can do this in the Parameters tab of the ROM Builder component².
• Define the output variables that you want to capture in your ROM, such as forces, moments, heat transfer coefficients, or pressure drops. You can do this in the Variables tab of the ROM Builder component².
• Define the design points that you want to run for your ROM, using either a predefined or a custom design of experiments (DOE) method. You can do this in the Design Points tab of the ROM Builder component².
• Run the design points and generate the solution snapshots for your ROM. You can do this by right-clicking on the ROM Builder component and selecting Update².
• Build and evaluate the ROM using DesignXplorer’s 3D ROM builder. You can do this by right-clicking on the 3D ROM builder component and selecting Update².
• Export the ROM in a standard format, such as FMU or ROMZ, that can be imported into other software tools, such as Twin Builder².

Is ROM Builder only for Steady State Cases, what module do I need to use for Transient Simulations in Ansys Workbench ?

ROM Builder is only for steady state cases in Ansys Workbench. You cannot build ROMs based on transient analysis using ROM Builder¹. If you want to create ROMs for non-linear transient systems, you need to use Ansys Twin Builder. These types of ROMs are called Dynamic ROMs; Twin Builder has a Dynamic ROM builder to make the process very simple². You can find more information about Twin Builder and Dynamic ROMs in the Ansys Learning Hub - Systems - Twin Builder³. You can also watch a video on how Reduced-Order Models can be used in real-time here. 

💥💥💥 What is porous jump boundary conditions and how to define it in Ansys Fluent ?

 Porous jump boundary conditions are used to model a thin membrane that has known velocity (pressure-drop) characteristics. It is a 1D simplification of the porous media model available for cell zones in Ansys Fluent¹. Examples of uses for the porous jump condition include modeling pressure drops through screens and filters, and modeling radiators when you are not concerned with heat transfer¹.

To define a porous jump boundary condition in Ansys Fluent, you need to follow these steps¹:

1. Identify the porous-jump zone. This is a type of internal face zone that represents the interface between cells, rather than a cell zone. You can use the Boundary Conditions task page to change the appropriate face zone to a porous-jump zone.
2. Set the Face Permeability of the medium. This is the coefficient that determines the pressure drop across the porous jump due to viscous effects. You can use different methods to calculate or estimate the face permeability, depending on the available data and assumptions.
3. Set the Porous Medium Thickness. This is the thickness of the porous medium that is used to calculate the pressure drop across the porous jump due to inertial effects. You can use a small value that is representative of your problem, such as 1e-5 m.
4. Set the Pressure-Jump Coefficient. This is the coefficient that determines the pressure drop across the porous jump due to inertial effects. You can use different methods to calculate or estimate the pressure-jump coefficient, depending on the available data and assumptions.
5. Define the discrete phase boundary condition for the porous jump (for discrete phase calculations). This is the option that specifies what happens to the particles that encounter the porous jump. You can choose to trap, escape, reflect, or rebound them.

How to fdefine porous jump in console  - Ansys Fluent ?

To enter these inputs in the console, you can use the following commands:

/define/boundary-conditions/porous-jump
zone-name <name-of-the-zone>
face-permeability <value-of-face-permeability>
porous-medium-thickness <value-of-porous-medium-thickness>
pressure-jump-coefficient <value-of-pressure-jump-coefficient>
discrete-phase-boundary-condition <trap|escape|reflect|rebound>

For example, if you want to add a porous jump boundary condition for a zone named “filter” with a face permeability of 1e-10 m^2, a porous medium thickness of 1e-5 m, a pressure-jump coefficient of 0.5 kg/m^3, and a discrete phase boundary condition of trap, you can type:

/define/boundary-conditions/porous-jump
zone-name filter
face-permeability 1e-10
porous-medium-thickness 1e-5
pressure-jump-coefficient 0.5
discrete-phase-boundary-condition trap

You can find more information about the porous jump model and its inputs in this web search result. I hope this answer is helpful for you.

💥💥💥 What are mesh quality and mesh errors in Ansys Fluent ?

 Mesh quality and mesh errors in Ansys Fluent are related to how well the mesh represents the geometry and the physics of the problem. A good mesh should have the following characteristics:

• It should conform to the shape of the domain and capture the important features of the geometry.
• It should have a smooth distribution of nodes and elements, without sudden changes in size or shape.
• It should have a low skewness and aspect ratio, which measure how far the elements deviate from an ideal shape (such as a square or an equilateral triangle).
• It should have enough resolution in regions where the flow is complex, such as boundary layers, shear layers, shock waves, etc.
• It should be compatible with the solver settings and the turbulence model used.

Mesh errors can occur when the mesh does not meet these criteria, and they can affect the accuracy and stability of the numerical solution. Some common mesh errors are:

• High skewness: This means that some elements are distorted or twisted, which can cause interpolation errors and convergence problems¹.
• Incorrect boundary layer meshing: This means that the mesh near the walls is not fine enough to resolve the viscous effects, which can lead to inaccurate predictions of wall shear stress and heat transfer¹.
• Coarse meshing: This means that the mesh is too coarse to capture the flow features, which can lead to numerical diffusion and loss of accuracy¹.
• A large aspect ratio leading to interpolation error: This means that some elements are stretched or compressed, which can cause errors in calculating the gradients and fluxes².

To check and improve the mesh quality in Ansys Fluent, there are several tools and methods available, such as:

• The Report Quality button in the General task page, which prints a message to the console with information about the mesh quality criteria¹.
• The Mesh Adaptation feature, which allows you to refine or coarsen the mesh based on various parameters, such as gradients, residuals, curvature, etc¹.
• The TUI commands or the Ansys Meshing tool, which allow you to modify or repair the mesh manually or automatically³.

How to check mesh errors and mesh quality in Ansys Fluent ?

There are several ways to check mesh errors and mesh quality in Ansys Fluent. Here are some of the resources that might help you:

• You can watch this YouTube video Ansys Fluent Tutorial - Check mesh quality errors and define mesh adaptation that shows how to use the Fluent interface to check and improve the mesh quality.
• You can also read this forum post When I open fluent and do mesh quality check, I’m that discusses a common warning message and how to fix it using the TUI commands or the Ansys Meshing tool.
• You can refer to this user’s guide ANSYS FLUENT 12.0 User’s Guide - 6.2.2 Mesh Quality that explains how to use the Report Quality button in the General task page and what the output means.

💥💥💥 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:

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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.