FLOWVISION CFD FREQUENTLY ASKED QUESTIONS

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1 FLOWVISION CFD FREQUENTLY ASKED QUESTIONS 1. Installation and Licensing 1.1. Does FlowVision have floating licenses? Actually all FlowVision licenses have floating capability and no extra fees are charged for this. Once you register a license with various capabilities, any computer connected license manager can borrow license properties What options do I have for specifying properties of a FlowVision license? Any FlowVision license should basically contain following information: Number of Pre/Post-Processors Number of Solvers (to be Run Simultaneously) Number of Parallel Processes (Total Number of Cores to Distribute among Solvers) Physical Modules 1.3. How many Pre/Post-Processors should be included in my license? Number of PPP determines the number of simultaneous users who are preparing simulation models. Therefore, you should be specifying how many team members would be involved in preparation of CFD models How many solvers and parallel processes should be included in my license? Number of solvers determines the number of simultaneous solver runs and these solvers can be run on any number of different processor cores each time. At any instance, total number of cores on which various solvers are run cannot exceed number of parallel processes. Therefore, you should be specifying how much computation power you would need and how many parallel runs would be expected Which physical modules are available to be included in a FlowVision configuration? Depending on your specific requirements, you can select whether to involve the following physical modules: Turbulence Models Multi-Phase Models Disperse Phase Transfer (including Porosity) Moving Bodies Gap (Clearance) Modeling Radiation Heat Transfer Sliding Mesh Combustion EHD (Electro-Hydro Dynamics) MPM (Multi Physics Manager) (ABAQUS Direct Coupling) 1.6. Can I install new version without uninstalling the previous one? Yes. You can also use the settings and folders from the previous version Can I use two versions of FV at the same time? Yes. However running multiple solvers depends on your license configuration What kind of licensing options does FlowVision have? There are academic, commercial and evaluation type of licenses which are also divided as annual and perpetual licenses on the time basis. Please ask your local reseller if you have different time period requests. Page 1 / 8

2 1.9. If license activation period has expired, can I install new version without creating a new license? Yes. To do that, do not uninstall the previous version of FlowVision until you setup the new version and confirm that it is running correctly Basically, what is implied by the high flexibility of installation and licensing? You can install each module (PPP, LM, SA) in any computer you prefer which can even all be separate machines. Then, you can install one or more LM in any computers and each module can look for license in the LM you prefer. 2. CAD 2.1. Can I sketch or model any kind of CAD geometry within FlowVision? You can model primitives such as box, cylinder, sphere etc Can I check conformability of my CAD model before running a simulation? Yes. You can use Check geometry for self-intersections. FlowVision is extremely accurate in detecting geometry related problems. The problematic parts are highlighted in Postprocessor tree Can I heal any CAD-related problems inside FlowVision? No, you can only detect CAD problems with FlowVision. However, you can use Capvidia s 3DTransVidia to translate, repair and heal CAD geometry Why is FlowVision superior in working with original and non-simplified CAD boundaries? Most CFD meshers work on the principle of dividing edges, surfaces and finally volumes into pieces and these divisions are based on linear geometric features. Therefore, resolution of CAD boundaries depend on number of divisions of the original CAD elements and boundary conditions are assigned to final mesh elements which are, intrinsically, simplified versions of CAD geometries. On the other hand, FlowVision applies SGGR (Sub Grid Geometry Resolution) technology where CAD surfaces are kept originally and grid elements are cut depending on curvilinear CAD boundaries. Resultantly, resolution of CAD boundaries is always the same with original CAD geometry and boundary conditions are assigned to original CAD surfaces. In FlowVision, grid resolution determines only solution accuracy, not accuracy of CAD preservation. 3. Substances 3.1. Are there pre-defined substances in FlowVision? Yes. Standard Substance Database contains majority of the mostly used substances used in CFD simulations Can I change properties of a substance in FlowVision database? Yes. You can reach the substance information in the folder named Database which is located in FlowVision installation folder under Program Files directory. If you have any further questions about changing the properties, please consult FV Technical Support Team Can I define a new substance and add it to the existing database? Yes. You can create new user substances and a new user database which is reachable through FlowVision interface in exactly the same way with standard database Is it possible to simulate non-newtonian fluid motion with FlowVision? Page 2 / 8

3 Yes. Non-Newtonian fluid motion can be included in the simulations through Preprocessor/Phases/(Preferred Phase)/Physical processes/motion: Non-Newtonian fluid 4. Grid Generation 4.1. How is the grid generation workflow in FlowVision? In FlowVision, grid generation starts with formation of initial Cartesian grid which is built in seconds. Having the initial grid, computations can be started and SGGR technology automatically works for fitting grid elements to region and object boundaries. Additionally, grid elements can be locally adapted with respect to geometric features, virtual geometries and solution gradients / results How can I define element sizing in initial grid? The simplest way to define initial grid sizes is to enter number of divisions in each axis which results in homogenously sized elements. However, for most of problems, initial grid editor and alternative initial grid editor is utilized to define size distributions of elements with various growth rates Which type of geometries can be used for determining adaptation locations? Firstly, all boundaries are natural sources of adaptation since boundary condition settings allow for adaptation with strata and boundary layer meshes. Additionally, you can adapt grid elements in any section of computational domain where there are no boundaries. For this purpose, you can either use simple geometric shapes created in FlowVision or import any arbitrary shape formed in a CAD software. Once you import a CAD file into FlowVision, you can define surfaces and/or volume of this geometry as an adaptation marker What is involved in FlowVision in the context of solution based adaptations? Any solution variable including but not limited to pressure, temperature and velocity can be selected and criterion for adaptation may be defined as either specific values of gradients of these variables. Any number of variables and criteria can simultaneously be included in a simulation and user can specify influence weights of each Do I have to stop simulation to perform solution based adaptation and the continue simulation with updated grid? No FlowVision has real-time adaptation feature. Solution based adaptation is carried on during the course of simulation and user can monitor adapted and updated computational grid in each time step How should configure FlowVision grid settings to work with moving bodies and surfaces? Users are not required to configure FlowVision grid to resolve moving bodies and surfaces. Thanks to SGGR technology; whenever a body changes its location between adjacent time steps, initial grid elements are re-cut and pre-defined adaptations are performed automatically in the region of moving bodies. Therefore, users can easily define moving bodies or prepare models with free surfaces and FlowVision would automatically updates grid elements around these surfaces. 5. Solver 5.1. Which type of numerical schemes are available in FlowVision? Skew & Non-Skew Schemes Implicit & Explicit Pressure Velocity Splitting Methods Page 3 / 8

4 First & Second Order Advection Schemes 5.2. Is it possible to simulate both steady and transient flows in FlowVision? Yes, FlowVision utilizes implicit standard (transient) and steady-state time integration methods. Steady-state time integration differentiates from standard version by discarding enthalpy change with respect to time in energy equation for solids and by discarding enthalpy and pressure change with respect to time in energy equation for liquids. 6. Post-Processing 6.1. Which modules are used for post-processing FlowVision results? FlowVision Pre/Post-Processor is main module for both pre and post processing. Additionally, you can attach FV-Viewer module to any running solvers to monitor existing results and visuals Do I have to stop simulation and save results in prior to investigating results? No, while FlowVision solver is running, you can connect to solver via Pre/Post- Processor and create layers which would be updated at the end of current time step. So, most of post-processing activities can be performed during the course of simulation and it allows user to have a detailed control over the results of an ongoing project. 7. Formula Editor 7.1. Is it possible to define input variables as a function of other solution variables? Yes, by using Formula Editor, any variable in FlowVision can be parametrically defined as a function of other variables, as a function of time, etc. All such formulas can be entered through a very easy Formula Editor interface without any need for coding experience Which type of operators are available in FlowVision Formula Editor? Operators available in FlowVision Formula Editor consist of but not limited to standard mathematical expressions like summation, subtraction, trigonometric operators and logical operators Can I define a personalized variable to monitor in the scope of post-processing? Yes, in FlowVision, you can create user variables which can be defined as constants, tabulated data or functions compiled via Formula Editor. You can define a user variable as a function of one or more variables obtained throughout the calculations and monitor them as values and plots. 8. Heat Transfer 8.1. Which types of heat transfer modules are available in FlowVision? Conduction, convection and radiation in fluids, conduction in solids and conjugate heat transfer modules are available in FlowVision Do I have to switch on/off energy equation in whole computational domain? No. You can switch on/of energy equation in each sub-region independently Can I use a different time step for heat transfer equations different than the global time step? Yes. You can define independent time steps for each of the physical phenomena through Preprocessor/Phases/(Preferred Phase)/Physical processes/(desired Physical Process)/Time Step Coefficient. Note that time step of a specific process is equal to multiplication of global time step and time step coefficient. 9. Turbulence Page 4 / 8

5 9.1. Which turbulence models are available in FlowVision? Laminar KES (Standard k-ε Model) KEAKN (Low-Reynolds k- ε Model of Abe, Kondoh, Nagano) KEFV (k-ε Model FlowVision) KEQ (Quadratic k-ε Model) SST (Shear Stress Transport k- ε Model) SA (Spalart-Allmaras Model) Sm (Algebraic Smagorinsky Model) 9.2. What is covered in FlowVision s near wall treatment approach? You can either turn off wall functions in the presence of very fine grid close to the wall. Otherwise, equilibrium and non-equilibrium wall functions can be preferred where latter is more suitable for flows with small y+ values. Additionally, switching on/off and selection of wall functions is specific to each wall and defined independently for each boundary condition For which y+ values, are wall functions applicable in FlowVision? In most CFD solutions, wall functions work uncertainly when y+ < 30 whereas in FlowVision 3.x.x; wall functions are applicable when y+ > Multi-Phase What is implied by the naming Model in FlowVision and why is it required? In FlowVision, there is a sort of modeling chain consisting of substances, phases, models and sub-regions, respectively. You should first import any number of substances you intend to use in the simulation. Then, phase(s) are created where there can be only one or more than one phase and into each phase you can add one or more substances. If there is more than one substance in a phase, it implies mass transfer. Following that, model(s) are created where there can be only one or more than one model and into each model you can add one or more phases. If there is more than one phase in a model, it implies phase transfer. Finally, you divide your geometry into one or more sub-regions by noting that only conjugate heat transfer can be calculated between two sub-regions and apart from that, each sub-region is independently solved. At the end, you should assign a model to each sub-region and note that one model can be assigned to any number of sub-regions but only one model can be assigned to a subregion. Now, starting from the beginning, you can follow the chain in any special way specific to your problem Can I simulate a multi-phase flow with FlowVision in presence of various phenomena such as free surfaces, mixing, particles, reactions etc.? Yes. FlowVision is highly capable of simulating multi-phase flows which are including but not limited to the sub-topics listed below: Mass & Phase Transfer Free Surface Flows Mixed Flows Dispersed Phase / Particle Flows Reacting Flows & Combustion (Please consult FV Technical Support Team for your specific case.) Page 5 / 8

6 11. Moving Bodies Which methods are available in FlowVision for modeling translating and/or rotating bodies? Moving Reference Frame (MRF) Sliding Mesh Actually Translating / Rotating Bodies Fluid Induced Motion Motion Induced by Artificial Forces Do I need to apply special techniques, use special computers or spend extreme meshing effort to simulate actual translation or rotation of a solid body in FlowVision? No. You should just assign any object as Modifier/Moving Body and define properties of motion. FlowVision sub-grid technology will simply handle your case. Please refer to FV documentation related to moving bodies and turbomachines Is it possible to define any geometry as moving bodies regardless of their shape and whether they are imported to or created in FlowVision? Yes. Any water-proof modeled geometry can be defined as a moving body. Imported objects are directly available under Modifier / Moving Body list. If you have created a geometry in FlowVision, initially Copy as imported object in order to make it available I would like to import a CAD model and define it as a moving body but some portion of the geometry remains out of the computational region. Does it prevent my simulation from running? No. FlowVision s sub-grid technology considers only the volume of the computational region and whatever exists out of the region borders is insignificant. Even if the body is rotating and resultantly the portion which remains outside changes with time, your simulation is still not interrupted. At each time step, only the portion remaining in the control volume is taken into consideration Do I have to rotate a body around its center (of inertia)? No. FlowVision assumes the geometrical center of the imported bodies as their centers of inertia and this is presented under Proprocessor/Objects/(Preferred Object)/Properties Window/Information/Dimensions/Center. However in Moving Body menu, you can either prefer Use Center of Inertia or enter the Center of Rotation you require. 12. FSI (Fluid Structure Interactions) Which FEA software can be integrated with FlowVision for FSI problems? You can integrate FlowVision with all FEA software but only in the case of ABAQUS integration, there is no need for a 3 rd party integration software such as MpCCI. In this case, user can easily configure coupling settings through FlowVision MPM (Multi- Physics Manager) and run even 2 way coupled FSI simulations without extensive IT knowledge and application What kind of data exchange mechanisms are available in the scope of a FSI simulation with FlowVision? The simplest way of data exchange is to export loadings at an instant from FlowVision and import into an FEA code which does not include coupling of software. Secondly, real time one way coupling can be performed where, for example, pressure distribution resulting from a transient flow field can be transferred to FEA software at Page 6 / 8

7 each time step but deformed CAD boundaries are not imported back to FlowVision. This would result in limited accuracy but significantly decreases computational costs. Finally, 2-way coupling between FlowVision and FEA software can be done where required fluid property distributions are transferred to FEA software and deformed CAD boundaries are transferred back to FlowVision. This transfer mechanism can be realized at every preferred number of time steps or simulation seconds. 13. Non-Newtonian & Visco-Elastic Rheology Which type of rheology models are available in FlowVision? Power Law for Viscosity Bird-Carreau Law for Viscosity Herschel-Bulkley Model 14. Compressible Aerodynamics Are there any limitations of FlowVision solver in regards of different Mach number flow regimes? No, FlowVision solver is capable of simulating subsonic, transonic, supersonic and hypersonic flows which involves flow regimes between Mach 0 to Mach >> Are there different solvers for each different Mach flow regime? No, FlowVision s general Navier-Stokes solver is capable of recognizing different flow regimes and calculation algorithms are updated automatically depending on location based flow characteristics. Since the recognition and application process is automatic, users are not expected to make special configurations and preferences before beginning such a simulation. 15. Porous Medium Is it possible to define porosity without modelling complex CAD geometries? Yes, you can define any arbitrary geometry or a sub-region as porous media and specify magnitude of porosity by means of resistance coefficients. Porous resistance can either be isotropic or unisotropic Is it possible to define porous surfaces in FlowVision? Yes, you can use Free Outlet boundary condition where pressure can be specified as pressure at porous surface. In this case, a user-defined hydraulic resistance is applied to the flow through the given boundary. To use this boundary condition, user should define static pressure, permeability, inertia coefficient and virtual thickness of porous boundary. 16. Gap Modeling How is it possible to resolve very small clearances (in sizes of microns) with FlowVision? FlowVision has a unique Gap Model which has been empirically verified with high accuracy. Once it is activated, user specifies the dimension interval to be considered as gap and during the simulation, FlowVision automatically detects these regions. In these regions, a source term representing the physics in the gap is added to momentum equation and user can do the simulation in the regular manner What should my meshing approach involve for the clearance regions? You don t need to resolve these very small gap regions with mesh elements which is already very difficult to do. Instead, you can continue using regular sized elements also in the regions where clearances exist. FlowVision Gap Model will identify these regions and update the solution algorithm automatically. Page 7 / 8

8 16.3. Does activating Gap Model increase computational cost drastically? No, Gap Model would only slightly increase computational cost but this increase is incomparably small with respect to the potential increase in computational cost when these regions are to be resolved with grid elements. Page 8 / 8