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© Fluent Inc. 5/10/2015N1 Fluids Review TRN-1998-004 Postprocessing and Visualization.

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Presentation on theme: "© Fluent Inc. 5/10/2015N1 Fluids Review TRN-1998-004 Postprocessing and Visualization."— Presentation transcript:

1 © Fluent Inc. 5/10/2015N1 Fluids Review TRN-1998-004 Postprocessing and Visualization

2 © Fluent Inc. 5/10/2015N2 Fluids Review TRN-1998-004 Outline  Solution monitoring  Solution data  Graphical display: vectors contours pathlines XY plots, histograms 2D vs. 3D  Alphanumeric reports: field data, fluxes, forces, integrals  Custom Field Functions  Data export

3 © Fluent Inc. 5/10/2015N3 Fluids Review TRN-1998-004 Solution monitoring  Graphical display of the solution provides: quick visual check of solution status indication of equations that are not converging  The actual solution quantity plotted depends on the software continuity equation convergence trouble affects convergence of all equations Fidap example here

4 © Fluent Inc. 5/10/2015N4 Fluids Review TRN-1998-004 Other Solution Monitors  You can also monitor and display other quantities during calculation Value of a variable at a boundary at a point Integrals/averages on a surface Force: lift, drag, moment  Another indication of convergence is when the monitored value stops changing Lift coefficient vs. iteration

5 © Fluent Inc. 5/10/2015N5 Fluids Review TRN-1998-004 Solution Data (1)  Pressure static, dynamic, total, pressure coefficient,...  Velocity magnitude, components, stream function, vorticity, helicity,...  Temperature static, total, enthalpy, internal energy, entropy,...  Turbulence kinetic energy, dissipation rate, effective viscosity, wall y +,...  Species mass fraction, mole fraction, concentration, deposition rate,...  m o2  k

6 © Fluent Inc. 5/10/2015N6 Fluids Review TRN-1998-004 Solution Data (2)  Properties density, viscosity, conductivity, specific heat,...  Wall quantities shear stress, heat flux, heat transfer coefficient,...  Grid coordinates, areas, volumes, quality measures,...  Derived quantities shear rate, stresses, other derivatives, …  Custom quantites User-defined Functions Field Function Calculator

7 © Fluent Inc. 5/10/2015N7 Fluids Review TRN-1998-004 Graphical Display of Data  What would “colorful fluid dynamics” (CFD) be without graphics?!  Graphical display should be more than just pretty pictures  The goal is visualization and understanding of the flow capture of gross features: is the flow headed the right way does it look correct? Have I done something wrong? Visualization of finer features: where does the flow separate what does the local heat transfer coefficient look like on the wall  Many options: contours, vectors, path lines,...

8 © Fluent Inc. 5/10/2015N8 Fluids Review TRN-1998-004 Contours  Color-coded contours are an effective means of visualizing scalar quantities such as pressure, velocity magnitude, stream function, …  Display is essentially 2-D  You can identify the min/max and gradients slide coater contours of stream functionfilled contours

9 © Fluent Inc. 5/10/2015N9 Fluids Review TRN-1998-004 Vector Plots  Velocity vectors indicate the direction and magnitude of the flow  Usually colored by velocity magnitude  Usually displayed on a surface, but shows “three-dimensionality”

10 © Fluent Inc. 5/10/2015N10 Fluids Review TRN-1998-004 Path Lines  Path lines trace the flow pattern using massless “particles”  3-D version of stream function contours  Can be colored/twisted by any scalar value  Be careful! You specify the starting point for the path lines, but... if the particles start outside a recirculating region, you won’t see it! particles released here nothing here?! Flow structure is actually quite complex! Particles released here

11 © Fluent Inc. 5/10/2015N11 Fluids Review TRN-1998-004 XY Plots  “Quantitative” data can be viewed as XY plots  Useful for comparing against experimental or other data  Examples: heat transfer coefficient along a wall pressure distribution on lift surfaces time dependent behavior (e.g., shedding)  Can be plotted on a surface, but usually along a line velocity distribution at exit of a coating die

12 © Fluent Inc. 5/10/2015N12 Fluids Review TRN-1998-004 Histograms  Histograms are a good way to visualize distributions cell skewness other statistics (e.g., variation of density throughout flowfield) Cell skewness distribution

13 © Fluent Inc. 5/10/2015N13 Fluids Review TRN-1998-004 2D vs. 3D  In 2D, data is normally plotted on the entire flow domain  In 3D, this is not feasible — too much data!!  Thus, for 3D problems, you normally plot data on: a surface or surfaces a line or lines  All outer boundaries are available as plotting surfaces  Most postprocessors provide tools for creating arbitrary plotting surfaces: points or lines planes, iso-surfaces, clipped surfaces

14 © Fluent Inc. 5/10/2015N14 Fluids Review TRN-1998-004 Alphanumeric Reports  It is not practical to view “raw data” — perhaps on a small, “mapped” grid  However, other alphanumeric reports are quite helpful: L D fluxes: e.g., summary of mass flux in/out of each boundary forces: e.g., summary of xyz components of forces/moments on a surface integrals: e.g., evaluate mass flow rate weighted average temperature at the outlet

15 © Fluent Inc. 5/10/2015N15 Fluids Review TRN-1998-004 Custom Postprocessing Values  Sometimes, the value you want to plot isn’t provided  What then? Some software programs provide: user-defined subroutines — calculation of “custom” quantities which then can be visualized “field function calculator” — you can enter a formula in a special GUI panel. The resulting quantity can be contoured, XY plotted, etc.

16 © Fluent Inc. 5/10/2015N16 Fluids Review TRN-1998-004 Data Export  Most CFD codes can write out data in other formats  For people who want to: view the data in another CAD program (I-DEAS, PATRAN, etc.) use a third-party postprocessor (FieldView, Ensight, Data Explorer, Tecplot, etc.) make some further calculations with the data using their own software

17 © Fluent Inc. 5/10/2015N17 Fluids Review TRN-1998-004 Animation  CFD data lends itself nicely to animation: i.e., moving pictures of the data  Examples: particles moving with the fluid fly-by’s, fly-through’s visualizations of moving geometries (e.g., mixing tanks) visualizations of other transient phenomena (e.g., movement of a shock) data on a plane passing through the domain  Its very helpful if the CFD software provides animation support: composition of animation proper file output formats

18 © Fluent Inc. 5/10/2015N18 Fluids Review TRN-1998-004 Summary  Postprocessing includes all the tools needed for interpretation and visualization of the CFD solution  Postprocessing occurs at two levels: qualitative check: are b.c.’s correct, does flow look “right” extracting the quantitative results that are needed for design  2D postprocessing is fairly straightforward and trivial  Effective visualization of 3D flows is assisted by: preparing appropriate plotting surfaces for viewing scalar data path line plots or particle tracks to “see” overall flow patterns animation to “bring the flow to life”

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