cfx, cfd-post, turbo tools 16.0 preview 4 -...

© 2014 ANSYS, Inc. September 19, 2014 1

CFX, CFD-Post, Turbo Tools 16.0 Preview 4


Release of Fourier Transformation Method for Single Stage TRS • Background

– Fourier Transformation Transient Rotor/Stator (FT-TRS) method was a beta feature in previous releases. Since its initial beta release, it has gone through a series of improvements, including accuracy and speed.

• In R16 FT-TRS is to be a released feature

– FT-TRS is best used on large pitch ratio single stage turbomachine where the use of other pitch-change models is not possible

– FT-TRS supports simulations with incompressible fluids in rotating machines such as pumps


Extension of Fourier Transformation Method Capabilities

• In R16 the FT method now supports numerous new applications:

– Ability to use FT-TRS for asymmetric flow situations:

• Fan in a cross-flow

• Impeller in vane-less volute

– Multi-disturbance capability:

• Blade flutter under inlet distortion

• Frozen gust analysis with inlet and outlet disturbances


Improved TBR Usability

• Background

– Time step changes and solution restarts for TBR simulations affect Fourier Coefficient sampling, requiring care on when to stop/start simulation

– Time step size restricted to integer division within period

• Implemented Flexible Time Step and Moving Averages accumulation

– Simulation can be started with large time step, then restarted with smaller time step for last few blade passings to reduce overall simulation time and improve accuracy

– Time step size unrestricted

– Fourier Coefficient Accumulation option “Moving Averages” fully supported


Provide CFD inputs for Harmonic Forced Response Analysis in MAPDL • Background

– R15 provided export of pressure harmonics for Mechanical cyclic Mode Superposition, but did not support user specification of the engine order to export

• CFX can now export pressure harmonic for:

– Arbitrary user-specified engine order (EO) from blade row interaction

– Blade vibration frequency from blade flutter analysis


More Powerful Solution Monitoring

• Background

– Monitoring the transient solution and determining when it becomes periodic in time was difficult and cumbersome

– Following the evolution of averages and other statistics of monitors was not possible

• Extensions to the CFX Solver Manager make it possible now to easily choose to monitor derived statistical quantities (averages, standard deviation, etc.) of any plotted value, and use these to examine convergence to a quasi-steady state solution

– See next slide for screen shot image


More Powerful Solution Monitoring

Monitor

Ave Monitor Over Blade Passing Period

Ave Monitor Over Common Period6


Steady-State Solution Interrupt Control

• Background

– It can be desirable to have the solver stop/interrupt when a target quantity (e.g. drag) is not changing with iterations – even if residuals are not fully converging, e.g. due to unrelated flow solution oscillations

• With R16 you can probe statistics (e.g. standard deviation, etc.) of monitors with solver progress, and stop the solver at defined value

• Especially important in automated workflows – e.g. Optimization

Example where solution is stopped when target quantity (red) becomes constant, based on its standard deviation over a

defined number of iterations (green) being below a specified threshold value

Instantaneous monitor value

Std. deviation of monitor over previous

‘n’ iterations


Improved Mass Flow Rate Specification

• Background

– Mass flow rate boundary condition specified for meshed boundary area, not for machine

– Change in blade count can lead to inconsistent specified flow rate

• R16 adds new Mass Flow Rate Area option with “Total for All Sectors”, allowing machine mass flow rate to be specified directly


Improved Mass Flow Rate Specification

Total for All Sectors area

Mesh sector boundary area


HPC Performance Improvements

• Background

– Dramatic HPC scalability advances were previously implemented, and required additional expert parameter settings for activation

• R16 incorporates numerous HPC improvements and changes, to deliver excellent scalability ‘out-of-the-box’

– Note change: coupled partitioning is the new default in R16

• Can change convergence behaviour!

Default HPC scaling on a transient water turbine simulation with 40M

nodes; benchmark in collaboration with Voith Hydro and HLRZ Stuttgart


Support for Cray XE

• Background

– Cray XE systems can optionally use either standard MPI or their own native ‘Extreme Scalability’ mode for HPC applications

• R16 provides full support for Cray XE ‘Extreme Scalability’ mode

– Take complete advantage of scalable performance of Cray XE systems using Cray’s own MPICH-based MPI library


64-bit MeTiS Partitioning

• Background

– The size of meshes that could be partitioned using MeTiS was limited, forcing users to select other partitioning methods and leading to less efficient partitioning

• R16 provides 64-bit MeTiS partitioning to generate high quality partitions on large cases

– More efficient partitioning more efficient calculation


I/O: File Writing with MPICH

• Background

– File writing time found to be excessive and not scaling on some systems identified as an issue with MPICH-based MPI

• Affected Cray ES mode, Intel MPI and Microsoft’s MS-MPI

• IBM Platform Computing MPI not affected

• R16 includes a dramatic reduction in the file write time with MPICH-based MPI


I/O: File Reading

• Background

– File read time could grow excessively for large complex simulations

• R16 reduces read time significantly particularly for large partition counts and cases with many surface definitions in the mesh

File read time reduction for water turbine simulation with 40M nodes;

benchmark in collaboration with Voith Hydro and HLRZ Stuttgart


Partitioning Improvements

• Background

– More widespread use of HPC highlighted importance of partition quality

– Poor quality partitioning can be detrimental to solver robustness and HPC scalability

• R16 provides new partition smoothing as means to generate higher quality partitions

Example application showing effect of new partitioning smoothing option to

improve efficiency and robustness

Partitions smoothed

Partitions not smoothed


HPC Diagnostics and Output Summary

• Background

– Standard CFX out files have been increasingly compact in recent releases, but parallel host information could still swamp the output when running with larger number partitions

• R16 makes standard diagnostics more succinct again, highlighting only the most important information

– Full output available when desired


Regular HPC Benchmarking

• Numerous benchmark cases run or planned for various HPC facilities and platforms, incl.:

– ANSYS-internal clusters

– Cray-internal XE systems

– Leibniz Supercomputing Ctr. (TU Munich) SUPERMUC

– National Center for Supercomputing Applications (Univ. of Illinois) Blue Waters

– High Performance Computing Ctr. (HLRS Stuttgart) Hermit


Supporting Work: Timing Instrumentation

• Background

– Diagnosing why performance on a given case was not as expected was difficult or even impossible, esp. remotely

Hurdle to focusing efforts for further HPC improvement

• R16 adds detailed instrumentation to measure times for all parts of solver

– Vital for development work

– Tool to aid remote assessment


ssh as Default Network Protocol

• Background

– The default rsh network protocol is no longer current, and is increasingly not supported on newer systems

• The default protocol has been changed in R16 from rsh to ssh (secure shell)

– Users can revert to rsh if desired


Reattachment Modification

• Background

– RANS models may produce exaggerated separation zones, at least when separation onset is correctly predicted

– Thought to be an inherent limitation of RANS models

• R16 includes the release of an option for the SST model to improve prediction of the re-attachment location

– Note: effect can be reduced with severe mesh refinement

Red arrows show the re-attachment location predicted with and without the modification on

a validation test case, and how it significantly improves agreement with the experimentally-

measured re-attachment location (black arrow)


Particle Tracking Enhancements

• Background – Customers highlighted various aspects of

particle-laden flow simulations that could be improved

• R16 includes a number of enhancements to ease the set-up and analysis of complex particle laden flow simulations – Wall energy flow density available for

expressions, post-processing

– Shear strain rate and other common fluid variables directly selectable as arguments for particle user routines


Interphase Heat Transfer

• Background

– Advanced multiphase users needed to change settings in multiple places in simulation and post-processing of cases with interphase heat transfer

• R16 makes such simulations less cumbersome and less error-prone

– Consistency between VARIABLES file and User Fortran (def_vars_mpf )

– Ability to output heat transfer coefficient and post-process interphase heat transfer rate

Example wall boiling application of interphase heat transfer due to

evaporation, quenching and convection


Other CFX Miscellaneous

• Clearer GUI terminology for pressure constraints at mass flow outlets

• S2S radiation output no longer includes misleading radiation intensity (which is also no longer in allowed variable list with S2S in CFX-Pre)


Precision Control for Auto-Annotation

• Background

– Animations of transient with display of time could lead to ‘jumpy’ text output, depending on given time value

• R16 adds user control for the number precision, giving better and cleaner annotation display in the viewer

– Applies to time value and other numerical quantities


Viewer Printing Performance

• Background

– Creating image files (png, jpg, etc) could take a long time, especially for scenes with many transparent pixels, slowing down interactive use as well as batch post-processing

• R16 has various general printing performance improvements, with the most dramatic improvements for cases involving volume rendering

Image file creation time for example with volume rendering • R15: 177 [s] • R16: 19 [s]


Toggle Visibility in Standalone Viewer

• Background

– Sharing ANSYS CFD results as 3D images from CFD-Post meant careful a priori definition of what parts of scene are visible or not

• In R16 this powerful means of sharing 3D results with any colleague or customers allow users to toggle individual object visibility within the viewer itself

– New hot key ‘e’ to list objects and toggle visibilities


Standalone Viewer Enhancements

• Background

– Embedding 3D images in MS Office applications was possible, but with compromised interactive response and the ability to print the selected view was limited

• The interactive response of the R16 3D viewer is instantaneous when embedded in PowerPoint, Internet Explorer, etc., and viewer printing possibilities are also available


Image Generation Efficiency on Linux

• Background

– Generating images using ‘screen capture mode’ can be much more efficient than default rendering for complex scenes, but was not fully supported on Linux

• R16 now fully supports ‘software rendering’ on Linux for much faster image generation

– Potentially large impact on animations of complex scenes and long transients

– Includes support for machines without DISPLAY, e.g. clusters without graphics

Example where time to generate streamline animation using ‘screen capture’ is >50% lower than with

default rendering


“On Demand” Turbo Variables

• Background

– Turbo-specific post-processing variables are calculated and stored at load time, and in some cases repeatedly, leading to delays at start-up and other situations (e.g. change in data instances for TBR simulations)

• Turbo variables are computed only if and when actually needed (“on demand”) in R16

– Analogous to other variables

– Particular impact for changes in data instances for TBR simulations


No Automatic ‘Apply’ of Turbo Plots

• Background

– Automatic creation of turbo plots with default settings often was annoying, as generating the default plot could be time consuming, esp. because default values need user adjustment in most cases

• R16 turbo plots are no longer automatically applied, so you no longer have to wait for the default plot to be generated before being able to make any adjustments

– Note: now must hit ‘apply’ for default plot


Interactive GUI Response on Linux

• Background

– Communication lag between the engine and GUI could cause interactive response to deteriorate significantly on Linux

• R16 incorporates improved algorithms to make Linux interactive response comparable to what it is on Windows

Example of effect of more efficient algorithm to connect GUI and engine, showing object

highlighting time

GUI

Engine

R15 R16

Windows instantaneous instantaneous

Linux ~30 [s] instantaneous


More Accurate Meridional Averaging

• Background

– Undefined values on a polyline could skew quantities like meridional averages and there were limitations with TBR data instances

• Meridional length averaging in R16 properly handles undefined points and works correctly with TBR data instances

R15 (top) shows discontinuities in meridionally-averaged pressure, much

improved in R16 (bottom)


Plotting Fluent Boundary Face Values

• Background

– Using interpolated nodal values for contour plots may not always sufficiently accurately reflect boundary values applied in Fluent

• R16 allows you to choose to use face values from Fluent in the generation of contour plots, to create plots that are fully consistent with boundary values applied in the solver

Face Values

Interpolation from Nodes

Example of difference on a polyhedral mesh


CFD-Post Miscellaneous

• Warning when loading Fluent MRF cases, to use “Velocity in Stn Frame” as equivalent to Fluent’s "Velocity Magnitude"

• Improved accuracy for calculations (e.g. mass flow) on iso-clips when analyzing Fluent results

• Updated pre-defined “comfort factor” macro


BladeModeler: Converting Imported CAD into Native Blade Design

• Example: Customer wants to optimize existing CAD impeller model – Need native BladeModeler description of

blade shape to perform parametric optimization

– R16 development focused on automatically extracting native blade design intent from imported CAD geometry

Camberline and thickness extraction

CAD model


Improved TurboGrid Automation

• Background

– Division between inlet/outlet blocks and blade passage mesh would not update with geometry changes

• Added new parametric inlet/outlet option to better support blade shape changes automatically (default in R16)


New TurboGrid Blade Configurations

• Background

– Some blade configurations previously not supported

• Added meridional splitter for core and bypass

• Added ATM topology for tandem vane configurations

• Added ATM topology for dual splitter impellers (Beta)


Improve TurboGrid Boundary Layers

• Background

– Near wall element thickness not consistent on blade, hub and shroud surfaces

• Improved near wall element thickness

– Uniform element thickness on blade surface

– Better match between blade-to-blade and hub-to-shroud distributions

– Improved element aspect ratios on LE/TE


TurboGrid Misc.

• Blade centered within topology (now default)

• Deprecated Traditional Control Point method

– Existing v15 (and earlier) state files still supported in R16


Turbo Workflow Enhancements

• Background: – Some turbo design workflows were complicated, or required too many user

operations

• R16 development focused on simplifying and reducing number of steps for specific design workflows – BladeGen to BladeEditor: Use “Create New Geometry” option on

BladeGen component in project schematic


Turbo Workflow Enhancements (cont’d)

– Vista CCD/RTD to BladeGen/Vista TF: Use “Create New Throughflow (BladeGen)” option to quickly setup a throughflow analysis with BladeGen and Vista TF

– Vista RTD to BladeGen/BladeEditor: Added radial element blade output option when using “Create New BladeGen” or “Create New Geometry” options

– Vista CCD to CFX: Use “Create New Turbomachinery Fluid Flow” option to quickly setup a CFD analysis with BladeGen/BladeEditor, TurboGrid and CFX


Turbo Workflow Enhancements (cont’d)

– Setup new compressor cases: Use Turbo Setup component to quickly create new throughflow or CFD analyses for different impeller geometry, mesh sizes or operating conditions


Vista Design Tool Enhancements

• BladeGen: “Create new Geometry” option to load the blade model in BladeEditor

• Vista CCD/RTD: “Create new Throughflow Analysis” option to setup an analysis in BladeGen/Vista TF

• Vista RTD: Added radial element blade output with support in both BladeGen and BladeEditor

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