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NX Flow uses computational fluid dynamics (CFD) to accurately and efficiently simulate fluid flow and convection. An element-based, finite volume CFD scheme is used to compute 3D fluid velocity, temperature and pressure by solving the Navier-Stokes equations.

The NX Flow technology allows a user to model complex fluid flow problems. The solver and modeling features include: • Steady-state and transient analysis (adaptive correction multigrid solver) • Unstructured fluid meshes (supports tetrahedral, brick and wedge element types) • Skin mesh (boundary layer mesh) • Complete set of automatic and/or manual meshing options for the selected fluid domains • Turbulent (k-e, mixing length), laminar and mixed flows • CFD solution intermediate results recovery and restart • Heat loads and temperature restraints on the fluid • Forced, natural and mixed convection • Fluid buoyancy • Multiple enclosures • Multiple fluids • Internal or external flows • Complete and seamless coupling to NX Thermal for simulation of conjugate heat transfer (handles disjoint meshes at fluid/solid boundaries) • Losses in fluid flow due to screens, filters and other fluid obstructions (including orthotropic porous blockages) • Head loss inlets and openings (fixed or proportional to calculated velocity or squared velocity) • Fluid swirl at inlet and internal fans • Fluid recirculation loop with head loss or heat input/loss or fluid temperature change between unconnected fluid regions • Automatic connection between disjoint fluid meshes • Altitude effects • Nonlinear flow boundary conditions

Reliable and robust CFD solver technology. NX Flow combines the versatility of finite element based analysis technology with the power and accuracy of a control volume formulation: • Algebraic multigrid solver technology • Solver solution time is linear with model size • Calculation points for momentum, mass and energy are co-located • Momentum and mass equations are solved simultaneously, not separately • Turbulence models include: mixing length, k-e and fixed turbulent viscosity • Near wall effects and convection are handled by enhanced log-law wall functions • First- or second-order advection schemes are available • Solver monitor with dynamic plotting of solution convergence and attributes • Intermediate results display and recovery directly from solver progress monitor

Simulation results Simulation results can be displayed with graphical plots, charts and reports. The NX post-processing toolset makes it easy to generate images and reports to communicate the desired results to a design team. The following simulation results are available for post processing: • Fluid velocity • Fluid and solid temperatures • Mass flux at the different fluid boundaries • Heat flux • Fluid pressure • Heat transfer coefficients • K-e turbulence data • Fluid density • Surface shear stresses

Key Features Automatic connection between disjoint fluid meshes. The NX Flow solver can automatically join dissimilar fluid meshes at the interfaces between the different parts within a complex NX assembly. This allows the user to quickly investigate many 'what-if' simulation scenarios involving complex assemblies. All parts within any design assembly context can be meshed independently. The resulting disjoint fluid faces at the surface junctions between the different parts within the assembly can be connected automatically to form a single fluid domain at solve time. Individual part changes can be re-integrated quickly within the assembly mesh, thereby avoiding the time consuming task of re-meshing the entire assembly.

Option for automatic fluid mesh created at run time. For modeling fluid flow around multiple parts, NX Flow offers an option for the fluid mesh to be generated automatically upon launching a solution. This feature allows the selection of a bounding volume around complex geometry to specify the external boundaries of the fluid domain. The fluid mesh is created automatically at run time and complies to all faces and volumes found within the bounding fluid volume (including automatic creation of the boundary layer mesh – skin mesh – on critical internal or bounding part surfaces). This NX Flow feature allows a user to quickly run multiple 'what-if' scenarios involving complex arrangement of parts within a bounding volume and multiple part feature changes can be investigated. The fluid mesh automatically adapts to the new location of internal part surfaces and volumes and to part feature changes at run time.

NX integrated CFD solution toolset NX Flow is integrated within the native NX advanced simulation product toolset. The NX integrated application allows the skilled engineer and CFD specialist alike to avoid any additional transfer of input files or geometry conversions and manipulations. Integrity is assured by maintaining data associativity between model building, solving and results interpretation within a common working environment. By virtue of being integrated, NX Flow provides the ability to model, catalog and share parts and material libraries among the entire NX design team, thereby minimizing tedious rework and modeling errors. The user can continue to work and prepare the next simulation model within NX while the CFD solver solution is running.

Thermo-fluid interactions The fluid flow modeling capabilities offered by NX Flow can be explicitly combined with the NX Thermal heat transfer solution within the NX advanced simulation toolset to simulate strong and fully coupled thermo-fluid interactions problems. Whenever the NX Flow and NX Thermal products are combined, the thermo-fluid iterative solver is automatically and seamlessly turned on within NX at no additional cost; offering both conduction and radiation modeling to be fully coupled to fluid flows through convective heat transfer at the fluid/solid interface. The coupled solver handles disjoint meshes at the fluid/solid boundaries. This unique technology thermally coupling the disjoint solid and fluid meshes provides a complete solution for simulation of conjugate heat transfer problems.