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Recent Advances in Modelling Wind Parks in STAR‐CCM+
Steve Evans
Agenda
• Introduction
– Company
– STAR-CCM+
• Wind engineering at CD-adapco
• STAR-CCM+ & EnviroWizard
– Developments for Offshore Simulation
CD-adapco: Engineering Success
3
We are a growing and successful engineering simulation company
• 20%+ growth in FY2011 global software sales
• $130m End User Spend in FY2011
• >560 employees in ~25 offices
• 40% of employees involved in Research and Development activities
• >9000 users worldwide
Our purpose is to ensure the customer’s success through the use of engineering simulation
• Enable & inspire innovation
• Reduce engineering time & costs
We provide successful engineering simulation solutions
• Software products like STAR-CCM+ that are accurate, efficient, and easy to use
• Flow, Thermal and Stress simulation in a single tool.
• Local dedicated support
• Engineering services: technology transfer, burst engineering resources, custom software tools
Our independence breeds engineering success
• Largest independent CAE/CFD provider
• Heavily invest in employees
• Continuously invest in development of new technology
Why our software technology? From our customers perspective
• A single workflow environment
– Integrated Flow, Thermal, Stress Process
– One tool to learn with all the major physics
– Allows easy toggle from one task to another
– “On the fly” solver setting change
– Streamlined and effective modelling
• Rapid pre-processing & design change
– Reduced man-hours on model prep
– Streamlined meshing for highly complex models
– Rapid design change analysis: Stop, change, start from last
• Client-Server
– Efficiency of large models over multiple cores
– Eliminate lag-time in transferring models to/from clusters to workstation
• Custom automation
– Design of Experiment
– Deploy best-practices to new users quickly
– Ensure consistency
Techn
ical V
alu
e
Wind Engineering with STAR-CCM+
• We have been working with our customers in the Wind Energy Business for the past 5 years.
• Today we have customers working
– Automated wind and site
– Automated blade design
– Offshore and ship engineering
– Code coupling (CFD to FE)
– Acoustics
STAR-CCM+ EnviroWizard
• The EnviroWizard is a GUI driven work process allowing quick & efficient setup of investigations of Wind & Site problems using STAR-CCM+
• Workflow process
– Terrain import
– Mesh Creation
– Boundary Conditions
– Polars (N directions)
– Post processing
» Quantitative
Wake Interactions
• Modelling the turbine interaction problem can generally be split into two problems
– Near Wake Effects
» 3D & tip effects, stall
- High fidelity models BEM/CFD required
– Far wake (Wind Park Level) including
» Wake interaction, turbulence & terrain
- Lower fidelity model such as actuator discs can be used
• EnviroWizard allows the User to investigate wake interactions
– Automatic setup of mesh and actuator functions
NASA AMES Wind Tunnel
Wake Interactions
• Each turbine is modelled individually as a momentum source.
– Torque
– Thrust
» User can choose
– Uin is area averaged velocity upstream of the disc
– Embedded meshing
» Hexahedral dominant mesh in main region
» Polyhedral disc & buffer region
270 degrees, flow aligned grid
Uin determined here
Buffer Region
Disc
EnviroWizard Developments
• While this automatic wake methodology works, the setup requires remeshing for each wind direction.
• In STAR-CCM+ 7.02 (end Feb 2012), CD-adapco will release a version containing the Overset method,
– This has the possibility to simplify the array problem
» No remesh.
» Just change the wind direction and disc orientation.
• The EnviroWizard will be released at the same time incorporating this functionality.
Overset Methodology
• Cells are marked according to three types:
– active, inactive, and acceptor.
• Active cells » regular discretized equations are solved.
» Donor for the interpolation.
• Inactive cells
– no equation is solved – they are temporarily de-activated.
– Need to be surrounded by acceptor cells.
• Acceptor cells
– discretized equations are replaced by interpolation equations which express cell-centre value of a variable as a linear combination of values at another grid.
Overset Methodology
Overset Validation
• Steady State Re=50 cross flow cylinder, 24K elements
Steady State Pressure
Steady State Velocity
Continuity Residuals Red – overset Green – no overset
Overset Validation
• Transient Re=200 cross flow cylinder, 24K elements
Time 0 – 150s
Y F
orc
e
Overset Features
• Release features for v702 (end Feb 2012)
– Any number of overlaps, restricted to:
» Not overlapping each other
» Not overlapping any solid body or exit background mesh
– Physics / Solver
» Steady, moving, or sliding grid.
» Parallel
» VOF, cavitation etc.
» Not particle tracking, liquid film
EnviroWizard with Overset
• New option in the Disc Models
– Setup of N turbines in array is performed with the Wizard.
• Test against a known case, Hornsref
Overset disc
The author wishes to acknowledge Elkraft who provided this production data and the owners of the array, Dong Energy and Vattenfall.
EnviroWizard with Overset
• Computational requirements
– Approximate timings for 5.9M cells
» 1 background mesh with 80 overset regions
– Test machine 2*4 core Intel Xeon X5560 2.8GHz
– Setup & mesh
» 15m
– Solver
» elapsed time on 8 cpus = 38 s/iter
– Peak memory (coupled solver)
» ~40 G
Convergence
EnviroWizard with Overset
6 m/s case
EnviroWizard with Overset
4
4,5
5
5,5
6
6,5
1 2 3 4 5 6 7 8
Upwind Nearly Neutral
STAR-CCM+ Overset
6 m/s case
Turbine number
Velo
city
Conclusions
• STAR-CCM+ is an open toolbox for simulating many aspects of wind engineering.
• Here we demonstrate a new feature of STAR-CCM+ v702 which has the possibility to greatly simplify the setup and calculation of offshore arrays using the overset method.
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