Vehicle Applications using STAR-CCM+ Frederick J. Ross Director, Ground Transportation
Agenda 2012: Great Year for Advance Vehicle Simulation This presentation will be broken down to two parts: – Key features/enhancements of STAR-CCM+ which are impacting ground transportation sector – Key applications where clients are taking advantage of virtual simulation in 2012.
2012 Key Advances in STAR-CCM+ for Ground Transportation Meshing – Improved geometry retention with surface wrapping – Indirect mapped interface – Geometry transfer from CAD Physics – Coupled Solver • Continuity convergence accelerator – Overset grids – Wall Film model • Boiling, Melting Solidification – Discrete Element Modeling (DEM) – Co-Simulation – Conduction Baffles Posting – LIC
Surface Wrapper: Improved Geometry Retention New Retention Code Old Retention Code V7.06 Introduces improved geometry retention from the surface wrapper. This allows the surface wrapper to move deeper into sharp corners. Studies with this features have shown improved convergence.
Indirect Mapped Interface Indirect Mapped Interface Indirect mapped interfaces have been used for years to map between CFD and FEA tools. Now, provided as a boundary type in STAR-CCM+ simplifies joining complex environment around solid components.
Accelerating erating Converge ergence: nce: Couple pled d Solv lver er Elapsed Time (Hours) Elapsed Time (Hours) 64 Cores 64 Cores Segregated: 0 Yaw 5.29 11.3 Segregated: Grid 1 2.22 Couple: 0 Yaw 9.5 Segregated: Grid 2 13.36 Segregated: 6 Yaw 2.7 7.67 Couple: Grid 2 Couple: 6 Yaw Coup uple le solver er has really ly been een pus ushed ed hard d over r the e past yea ear r by our ur F1 teams ms – F1 Teams are regulated on amount of CFD/Wind Tunnel Time used – Coupled solver has allowed teams reduce computational costs by 25%. This allows more calculations per year. STAR-CCM+ improvements now show time reduction for passenger cars as well as commercial vehicles.
Optimate: Design Exploration Mode Forms Response Surfaces There has been increase in demand for DOE studies. In 2012, CD-adapco came out with new license plan to be more flexible for DOE studies. Included is also optimization tool within STAR-CCM+ to simplify the process.
Overset Grids 2012 Introduced the new feature of overset grids. This helps simplify moving complex paths or motion such as pumps, vehicle handling, or passing.
Water er/Dir /Dirt t Managemen gement Wall film model allows water to be tracked on surface. Body forces added to simulate motion of windshield wipers New wall film models are also helping improve DeIce/DeFog simulations Head Lamp Defogging
Spray Freezing on Windshield Liquid film solidification has also been implemented and is • currently undergoing extensive testing... Example: Freezing of a liquid film created by water droplets • hitting a cold windshield Wall Film includes ability of phase change. The above example shows ice building up on the windshield as particles impact on the cold surface.
Modeling of Cabin Deice/Defog Deicing/Defogging modeling in STAR-CCM+ Thin Film Model – Defog dependent on coefficients – DeIce not valid for low ambient temperatures 2012: Wall Film Model – Provides more physics based model for both deIce and Defog Water film model now can model physics of condensation, melting, and solidification. The enhanced physics improves accuracy for cases with low ambient temperatures.
SCR R Devices es • V7.06 Adds boiling to wall film – SCR are commonly found in Off- Highway, Commercial Vehicles, and Automobiles Latest release of wall film includes condensation and boiling. These are needed components in modeling SCR devices within STAR-CCM+.
Discrete Element Method (DEM) • Advance Fluid-Particle interaction – Particles can simulate: • Dirt Particles • Grass Clumping on Lawn Mowers • Corn Husks • Snow Flakes • Sand – Particles can bounce or stick or even break apart. Circular or composite particles DEM has been pushed heavily by off-highway vehicles. Enhancements in 2012 enable to model millions of particle fully coupled to CFD simulation in a reasonable time frame.
Vector Option: LIC Added features are being developed for post processing. There is now simh to store results for iteration or time step. New graphics options such as LIC vector style. Plots shown with Vortex core tracking from v6.
Key applications where clients are taking advantage of virtual simulation in 2012. Ground Transportation covers wide range of applications. STAR-CCM+ has grown in use for each of these individual groups. This next section highlights some of the recent work.
Impacting Design: Aerodynamic Optimization Ford has shown recently a process for rapid aerodynamics at a recent workshop ANSA – Evaluate response surfaces to determine optimum design. – Compared both steady to unsteady simulation STAR- • Unsteady solution took 10 times CCM+ longer – Turn-Around: 200 cases per week • Steady Solver • 20-30 million cells PowerPoint • 500 processor cluster DOE study compared steady simulation to transient. With steady simulation, the client was able to form the same response surface as predicted by transient, but in 1/10 th the computation time.
Trend: Increase of Transient Simulation Simulating Transient Operating Conditions In 2012, there has also been increase in demand, and testing looking at transient aerodynamics. Some work looks at transient operating conditions, such as passing or vehicle cornering.
Growth in Aero-acoustic Key Areas of Interest – Aero-Vibroacoustics – Internal Flow • HVAC Ducts • Fans • Pumps Over the past year, emphasis of aero-acoustic study has shifted from far field propagation to vibro- acoustic and propagation of noise into the cabin.
Example Unsteady Simulation: Fluid Solid Interaction Roof Deflector • This is an example where it is important to run the mesh morpher as part of the unsteady analysis. • Displacement exaggerated for animation • Displacement can be calculated coupled to stress code, or using internal stress solver of STAR-CCM+ Fluid solid interaction key use for unsteady simulation.
Water/Dirt Management • Transient DES simulation tracking water particles on side of vehicle. – Water particles leave wheel region, tracked with wall film model on vehicle surface. • Also looking at exhaust gas mixing in vehicle wake to find regions – Exhaust gas trapped in wake of vehicle is drawn into vehicle through air vents. Combining DES with fluid particles in wake provide more realistic soiling on rear and sides of the vehicle.
Ground Transportation External Aerodynamic • Environmental Conditions • Water/Dirt Management Vehicle Thermal Management • Front End Cooling/Top Tank Temperature • Component Temperature Prediction Cabin Simulations • Physiological Models • Defrost/Demist analysis Manufacturing Simulations • Paint Dipping • E-coat Powertrain • Intake/Exhaust • SCR Catalyst System
Vehicle Thermal Management (VTM): Front End Cooling Cooling air flow: Heat Exchanger Sizing/Positioning • Top Tank Temperature Prediction • Models secondary flow for CAC and • radiator. Fan Simulation Body Force Method • Pressure Jump • Multi-Reference Frame • Rigid Body Motion • CD-adapco has over 20 years experience looking at vehicle heat protection. With STAR-CCM+, front end cooling has been made easy. Users are achieving results within 24 hours.
Key Feature: Enabling Quick Turn-Around • STAR-CCM+ builds all tools in a single environment – Grid generation in STAR-CCM+ designed as pipeline process. – Designed to enable quick modifications – Environment promotes automation • Record button on GUI helps quickly build automation Pre-processing is a key advantage of STAR-CCM+. Clients are finding pre-processing tools time savings up to 70% of their previous process
Example: Tractor • Done several demo’s by Pre - Sales on off-highway vehicles – CAD: ProE – Baseline Study: 7 days – Replace component 1 day • Swap geometry: 10 minutes • Analysis: 10 Hours • Post Processing: 0.5 hours – Output: • Coolant top tank temperature • Temperature field • Flow field Case goes straight from ProE to STAR-CCM+. Surface wrapping enables automation of case setup. Modifications just a swap of part.
CAD to Solution in 1 Day • CD-adapco worked with Off Highway Client to automated process – Model Preparation: ProE • All boundaries names are marked in ProE model. • Surface exported straight from STAR-CCM+ • Head nodes generate mesh • Once done, job pushed straight over to cluster • Post processing done at end of run on cluster • Returns PowerPoint with results. Process is completely automatic. Modifications can easily be done by exporting new surface, or just swapping CAD file.
Autom omat ation ion: : Generati erating ng Pa Part t Conta tact ct User has different options to form part contacts: 1. Build part contacts in CAD 2. User boolean operation in STAR-CCM+ CAD module 3. Imprint triangulated surface in surface repair module 4. Mesh separate, use solver to arbitrary match surfaces • Indirect mapped interface or direct. One of the strengths of STAR-CCM+ is in building CHT assemblies for complex geometry. This includes both modeling of the solids, as well as fluid around the object.
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