S-ducts and Nozzles: STAR-CCM+ at the Propulsion Aerodynamics Workshop. Peter Burns, CD-adapco

Transcription

1 S-ducts and Nozzles: STAR-CCM+ at the Propulsion Aerodynamics Workshop Peter Burns, CD-adapco

2 Background The Propulsion Aerodynamics Workshop (PAW) has been held twice PAW01: 2012 at the 48 th AIAA JPC Conference in Atlanta PAW02: 2014 at the 50 th AIAA JPC Conference in Cleveland Two main flow categories S-shaped duct Nozzle flows CFD studies are performed as blind benchmarks Committee provides both structured and unstructured grids but encourages generation of tool-specific meshes

3 S-Duct: Overview All geometry as provided Half-model w/symmetry plane With & without VGs Using the supplied diagram as a reference: OUTFAR, FARFIELD, INLET: Given: total pressure & total temp OUTLET: Given: target mass flow 8 VG vanes Results measured by comparison to experimental data from ONERA Pressure recovery Distortion coefficient Both measured at same probe location (AIP)

4 S-Duct: Mesh Structured AIAA provided 23 M cells* Unstructured AIAA provided 31 M cells* STAR-CCM+ polyhedral 18 M cells* 24 Prism layers, 0.01 mm near wall spacing (y+ < 1) * Cell count given for case w/ VGs

5 S-Duct: Solver STAR-CCM+ v , double precision Coupled Implicit Solver Cell-centered formulation for general cell type Grid sequencing initialization Expert driver Steady-state RANS SST (Menter) k-w, Standard (Wilcox) k-w, Realizable k-e Curvature correction enabled Ideal gas

6 S-Duct: Results Case without VGs, SST k-ω, STAR-CCM+ mesh Separation and counter-rotating vortices No re-attachment prior to bulb

7 S-Duct: Results Case with VGs, SST k-ω, STAR-CCM+ mesh Separation prevented

8 S-Duct: Results Pressure Ratio at AIP for different turbulence models Mesh - AIAA Unstructured Geometry - without VGs SST k-w Standard k-w Realizable k-e

9 S-Duct: Results Pressure Ratio at AIP Geometry - without VGs SST k-w Realizable k-e AIAA Unstructured STAR-CCM+ AIAA Unstructured STAR-CCM+

10 S-Duct: Results Experimental Results: PR = 0.97, DC = 0.02 Unstructured, no VGs SST k-w Standard k-w Realizable k-e Pressure Recovery Distortion Coef SST k-w, no VGs STAR-CCM+ Unstructured Pressure Recovery Distortion Coef

11 S-Duct: Results Pressure Ratio at AIP for different turbulence models Mesh - AIAA Structured Geometry - with VGs SST k-w Standard k-w Realizable k-e

12 S-Duct: Results Pressure Ratio at AIP for different meshes Turbulence SST k-w Geometry - with VGs AIAA Structured STAR-CCM+ AIAA Unstructured

13 S-Duct: Results Structured, VGs SST k-w Standard k-w Realizable k-e Pressure Recovery Distortion Coef SST k-w, VGs Structured STAR-CCM+ Unstructured Pressure Recovery Distortion Coef

14 S-Duct: Lessons k-w was the most consistent performer True for majority of participants Predicts larger velocity deficit without vgs Sharpest counter rotating vortex pair with vgs 2 eqn, eddy viscosity models are challenged by flow physics k-e significantly more diffuse than SST Investigate higher order explicit algebraic closures (quadratic/cubic k-e), new EB-RSM model? STAR-CCM+ proved to be a robust tool for propulsion related flows Continues to be difficult to predict both pressure recovery and distortion coefficient accurately

15 Nozzles: Overview 25 deg Converging Nozzle Swept through range of (P t,inlet /P t,amb ) = ( ) Dual Separate Flow Reference (DSFR) Constant extraction ratio (P t,fan /P t,core ) = 1.2 Swept through range of (P t,fan /P t,amb ) = ( ) 25 deg. Conv. DSFR Mainly focus on axisymmetric Results include: Thrust and discharge coef Static and Total Pressure probes Plume contours

16 Nozzles: Mesh 25 deg Converging AIAA Provided Mesh STAR-CCM+ Trimmed Hex

17 Nozzles: Mesh - DSFR AIAA Provided Mesh STAR-CCM+ Trimmed Hex

18 Nozzles: Solver STAR-CCM Coupled Implicit Solver Grid Sequencing Initialization Expert Driver Enabled Continuity Convergence Accelerator (CCA) Steady-state RANS : SST k-ω Ideal gas Standard Day Air, constant material properties

19 Nozzles: Results - 25 deg Converging PR = AIAA Provided Mesh STAR-CCM+ Trimmed Hex Overall, STAR-CCM+ mesh exhibited less numerical diffusion of shock-train features and outer extent of plume vs. AIAA provided mesh

20 Nozzles: Results - 25 deg Converging Axisymmetric 3D Mesh w/ Splitter Plate

21 Nozzles: Results - DSFR P t,fan /P t,amb = As with the previous case, the STAR-CCM+ generated mesh captures more of the small scale disturbances and is less diffuse overall. Particularly apparent at the transonic regime

22 Nozzles: Results - DSFR

23 Nozzles: Results DSFR, 3D Time and CPU resources only permitted one fully 3D analysis to be performed Results similar to axisymmetric case, with an increase in core Cd P t, fan / P t,amb = 2.6 AIAA Mesh

24 Nozzles: Lessons STAR-CCM+ is an efficient and robust tool for the prediction of supersonic nozzle performance Not overly sensitive to mesh, although STAR-CCM+ generated meshes appear to provide better resolution The Continuity Convergence Accelerator (CCA) and Solution Driver provide a robust and fast solution convergence STAR-CCM+ is capable of handling large meshes and complex shock interactions Highlighted in 3D DSFR nozzle simulation

25 Thank you! Questions/Comments? Interested to hear more? PAW02 invited paper 51 st AIAA JPC Conference in Orlando