List the 3 most widely used methods in CFD! Specify the generic transport equation in integral form! Define the conductive and the convective flux! Write the generic transport equation in differential form! What quantities can be represented by fi? Specify the continuity, the equation of motion and the energy equation in conservation form. What kind of terms are the viscous stress and the pressure gradient in the generic transport equation? What form of the transport equations is used in finite volume discretization? What is the conservative behavior of finite volume methods? How algebraic equations can be obtained from the governing equations? At which points of the mesh are geometrical data and field variables stored? What is an iterative solution method? What do we mean by the convergence of iterative methods? How can the boundary conditions be interpreted in the case of finite volume method? List and explain the steps of CFD analyses! What do we mean by boundary conditions of first and second kind? What is a mixed boundary condition? What do we call by a boundary condition in FLUENT simulation system? Describe the physical meaning of Velocity Inlet and Mass-flow Inlet! What boundary conditions are used in each transport equations (in the case of VI and MI boundary conditions)? Which can be used for outlet and what are the application conditions? Describe the physical meaning of Pressure Inlet and Pressure Outlet boundary conditions! What boundary conditions are used in each transport equations (in the case of PI and PO boundary conditions)? In which case the Static Pressure / Total Pressure must be specified? Describe the outflow and the pressure far-field boundary condition! Which density models this boundary conditions can be applied with? What are their advantages over the pressure boundary conditions? Describe the Inlet-vent, Intake-fan, Outlet-vent and Exhaust-fan boundary conditions! How can the pressure jump be defined? Describe the Symmetry, Wall, Axis and Periodic boundary conditions and their application area! What are the rules of co-operation of inlet and outlet boundary conditions? What inlet and outlet BCs can be automatically converted into each other? What kind of outlet boundary conditions can be used for junctions (having more than one outlet)? What inlet boundary conditions can be used for compressible flows? Is outflow allowed through a pressure inlet? How is the specified pressure value regarded by the solver in such circumstances? Explain the 4 different approaches for fluid machinery modeling! Give an application example on the Fan model! Briefly describe the “frozen rotor” approach! What are the limits of applicability? What are the advantages of this approach? Explain the principles of the Mixing Plane model! How can the stator and rotor be linked in sliding mesh models? What are the advantages of this method over the frozen rotor approach? What is a Laminar Zone, Source Term and Fixed Value condition is used for? What are the aims of Fan, Radiator, and internal Wall conditions? What is the advantage of an internal Wall over a solid block? How can a porous zone and a porous jump be parameterized? What are the differences in the application of those? Give examples on the applications of volume sources! What are the aims of the Interface and Interior boundary conditions? Which physical effects is turbulence caused by? Explain Kelvin-Helmholtz instability! List the most important characteristics of turbulent flows! What is the ratio of the size of the smallest and largest eddies? Categorize turbulence models and briefly describe each model category! List RANS models and their application area! List and briefly describe scale resolving turbulence models! Define the turbulent kinetic energy! Why k on its own not enough for the proper description of turbulence? Please, explain the grid turbulence experiments and their results! What is the definition of epsilon? Define turbulent scales on the basis of k and epsilon! Explain the governing equations of k-epsilon model mentioning only the most important terms! What are the major application differences between k-epsilon and k-omega models? What do we mean by High-Reynolds Number and Low-Reynolds Number turbulence models? Give some examples on estimation of the turbulence length scale! How can be the turbulent kinetic energy estimated on the basis of the average flow conditions and turbulent intensity? Describe the Large Eddy Simulation method! What are the advantages and disadvantages? What are the components of a numerical mesh? What kinds of 2D and 3D elements are allowed in Workbench Mesher? Where it is necessary to refine the mesh? Demonstrate the meaning of grid orthogonality (or skewness)! Why does it lead to numerical errors? How do we measure the skewness? Approximately, what values of the equangle-skew is allowed for hexahedral and for tetrahedral meshes? Why must the rate of change of the cell size be limited? Roughly that is the preferred expansion rate? What do we mean by streamlining the mesh? In what applications it is especially important? Why wall inflation layers are used? What is the proper size of the wall adjacent cells? What are the advantages and disadvantages of hexahedral meshes? What are the advantages and disadvantages of tetrahedral meshes? What is a dual mesh and how to create it? How can be the mesh adapted? What meshing methods are available in Workbench Mesher? What preparatory steps are possible for helping the mesher? Give examples on deforming mesh applications! Compare compressible and incompressible models in the following aspects: density models, interpretation of the total pressure and preferable (maximum) time step size! How to set up a model for natural convection in FLUENT? Mention some application examples! What thermal boundary conditions are possible on solid walls? How to model conjugate heat transfer? Give some examples! How is Heat Transfer Coefficient (HTC) is defined in CFD models? How is the reference pressure defined in the presence of gravity in FLUENT models? How is this definition taken into account when using pressure boundary conditions? Define the absorption coefficient and the optical thickness! In what range of the optical thickness S2S, P1 and DO models can be used? What optical effects can be taken into account in Discrete Ordiantes (DO) radiation model? What is model checking, validation and calibration? What is the difference between an error and uncertainty? What are the reasons for model uncertainty? What is the discretisation error caused by? What is the practical meaning of the order of convergence? How can the grid independency of the results be tested? Define the iteration error! What are the most frequent reasons of convergence issues? What is the significance of residuals? How can you check that the solution is converged? Give examples on slowly converging quantities! How do you know that the iteration error has reached the limit defined by the truncation error? What is the reason for the truncation error and how to reduce this error? What models are sensitive for truncation error? What are the reasons for application uncertainties? Give some examples on models which are sensitive for geometrical accuracy! How can the sensitivity of the results for the boundary conditions be reduced? How can you estimate the error rising from the inaccurate boundary values?