Design Exploration of Low-Speed Wind Tunnel for Improved Flow Characteristics with STAR-CCM+ and Optimate+

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1 Design Exploration of Low-Speed Wind Tunnel for Improved Flow Characteristics with STAR-CCM+ and Optimate+

2 Aerodynamic Department LWTE AWTE 2 RUAG Aviation

3 LWTE Test section Test Section 7m x 5m x 12m (21x15x36ft) Max. 68 m/s, Ma=0.2 3 RUAG Aviation

4 Reference Wind Tunnel Tests 4 RUAG Aviation

5 Large Wind Tunnel Emmen LWTE Facility built RUAG Aviation

6 Large Wind Tunnel Emmen LWTE facility built 1945 continuous improvements - flow straightener (Darchem honeycomb), controlled systems, model manipulators (sensors and software), data acquisition, master control program, upgrade hydraulic supply, acoustic capability RUAG Aviation

7 Large Wind Tunnel Emmen LWTE facility built 1945 continuous improvements - flow straightener (Darchem honeycomb), controlled systems, model manipulators (sensors and software), data acquisition, master control program, upgrade hydraulic supply, acoustic capability 2014 study for further upgrades: - test section - cooler - fan blades 7 RUAG Aviation

8 LWTE Airline test section nozzle flow straightener honeycomb 3200kW CR fan Mesh 8 RUAG Aviation

9 LWTE Airline Evaluation plane for flow homogeneity Mesh 9 RUAG Aviation

10 Flow Quality Mesh in corner 3 Velocity in test section 21 Iterations 10 weeks of wind tunnel occupancy 10 RUAG Aviation

11 Motivation 2016 Fan blade redesign and replacement Fan blade design life reached Improved flow distribution behind the fan, less velocity deficit in the wake of the nacelle Mesh refurbishment necessary due to age Reduction of pressure losses Compensate for pressure losses due to possible installation of a heat exchanger which stabilizes flow temperatures Improve wind tunnel efficiency and maximum speed Use CFD as a tool to improve efficiency of optimization 11 RUAG Aviation

12 LWTE Optimization - Background Transient simulation of full wind tunnel 3D unsteady Segregated flow solver Constant density air SST k-ω turbulence model All y+ wall treatment Rigid body motion for propellers No mesh present in corner 3 Steady optimization simulations 3D steady Use transient results for BCs Specified Pressure Atmospheric Pressure Specified Velocity Inlet 12 RUAG Aviation

13 Simulation Experiment LWTE Optimization - Background 13 RUAG Aviation

14 LWTE Optimization - Background Parameters (170) Inertial resistances in porous baffle equation p = ρ(α v n + β)v n Discrete set of 34 values corresponding to known mesh configurations Design goals Maximize flow uniformity in test section Minimize pressure drop RUAG Aviation

15 LWTE Optimization - Background Transient simulation of full wind tunnel 70 M trimmed cells Steady optimization simulations 16 M Trimmed cells 15 RUAG Aviation

16 LWTE Optimization - Background Reporting 1000 iteration moving averages of max dynamic pressure difference and pressure drop Convergence 25 Pa 1000 iteration asymptotic stopping criteria for pressure drop 0.01 Pa 1000 iteration asymptotic stopping criteria for max dynamic pressure difference max iterations flags design as error due to lack of convergence if reached 16 RUAG Aviation

17 LWTE Optimization - Results RUAG Aviation

18 LWTE Optimization - Conclusion In 1 week of optimization the maximum difference in the test section dynamic pressure reduced from 13% of mean to 2.1% of mean Identified novel concepts for mesh design with potential to significantly reduce pressure drop with good uniformity Additional runs are expected to continue to find improved designs More thorough validation of the CFD model to LWTE Update the CAD to correctly represent the propeller geometry Include flow straightener Ensure mesh and time step independence Incorporate a pressure drop constraint that would allow the addition of the heat exchanger Pareto optimization would represent a valuable approach to this problem 18 RUAG Aviation