One-Click CFD Users' Guide

Distributed by Khamsin Virtual Racecar Challenge
http://www.khamsinvirtualracecarchallenge.com
Copryight (C) 2015 Julien de Charentenay, PhD
Presentation Outline
1.Introduction
2.Objective(s) of the Presentation
3.Geometry Preparation
4.Starting a Simulation
5.Post-processing

Introduction
What is One-Click CFD?
• It is a CFD framework based around openFoam;
• It enables people interested in car aerodynamic to run CFD analysis
with no or very limited knowledge of CFD or openFoam;
• It is the framework used for CFD modelling in the KVRC Challenge;
• It is free to use (Note: One-Click CFD can send simulation to
Amazon AWS Cloud at user request. When using this option, users
need a valid Amazon AWS account and will be charged by Amazon
AWS for their usage).
Interested: Download One-Click CFD from
http://www.khamsinvirtualracecarchallenge.com/one-click-cfd

Presentation Objective
• Provide an overview of what is involved
when using One-Click CFD

Geometry Preparation
1.Orientation & positioning;
2.Part splitting & naming;

• The first step is for the user to generate the geometry using a CAD
package, then export the CAD geometry in STL format. The CAD
model requirements and STL naming conventions are detailed
herein.
• One-Click CFD will only simulate for airflow for half of the geometry
to reduce simulation time. But: you need to prepare a full model!
• One-Click CFD uses the STL file format:
• Export to STL in meters;
• The STL file name and solid name are used to identify the parts of the car.
The naming convention described later can be used in the file name and
solid name. For example for the car body (convention name body):
– The filename could be "mycar.stl" and the solid name "body"; or
– The filename could be "body.stl" and the solid name "test23"; or any other variations.

The geometry should be facing the -y
axis direction

Align lowest point of wheels with
plane z = -5mm
(in other words: the ground will
always be the plane z = 0)

• One-Click CFD identifies geometry part(s) through their
name (which can appear as filename or solid name in
the STL file itself). The identified name patterns are case
insensitive and are as follows:
• wheel-front to identify front wheels and apply wheel rotation;
• wheel-rear to identify rear wheels and apply wheel rotation;
• engine-intake to identify engine air intakes and apply ;
• engine-exhaust to identify engine air exhausts;
• cooling-intake to identify cooling system air intakes;
• cooling-exhaust to identify cooling system exhausts.
• STL parts that are not identified above will be considered to
be parts of the car body. It is not required to have all or any of
the above.

Example of STL naming convention:
Wheel-Front-Left
Wheel-Rear-Left
Body
Engine-Intake-1

• Brief checklist:
– Did you model the full car?
– Is the car facing the -y direction with the +z the up direction?
– Is the car position consistent with the road at plane z=0?
– Did you export the CAD model to STL using meter units?
– Does the exported STL parts or filename follow the naming convention?

Starting a Simulation
• To start a simulation:
1. Open a File Explorer;
2. Change the directory to:
• If using only 1 STL file, the directory
where the STL file is located;
• If using multiple STL files, the parent
directory of the directory where the STL
files are located
1. Select the STL file (or the directory
containing the STL files);
2. Right click;
3. Select the context menu entry:
• One-Click CFD > 100mph (local) to run a
simulation on the local computer with a car
velocity of 100 mph;
• One-Click CFD > 100mph (AWS) to run a
simulation on the Amazon AWS Cloud with a
car velocity of 100 mph;
• One-Click CFD > 200kmh (local) to run a
simulation on the local computer with a car
velocity of 200 km/h;
• One-Click CFD > 200mph (AWS) to run a
simulation on the Amazon AWS Cloud with a
car velocity of 200 km/h.
• Note: the KVRC challenge will use the
100mph scenario.
Using one STL file
Using multiple STL files

Start a Simulation
• After starting a simulation, the simulation will proceed
without any further user input.
– If running the simulation on your local computer, a Command
Prompt window will open that will inform you on the progress of
the simulation.
• If the simulation succeeds (ie everything works as expected), the
window will close automatically when the simulation is complete,
and you can move on to Post-processing;
• If the simulation fails an error message, the window will stay open
with an error message. The error message will not be very helpful
(in most cases), but please take a screenshot and send me an
email. I may not be able to help in the short term, but it is worth a
try. Also ask help from others on either F1 Technical or CFD online
forums. Also have a look at the Post-processing to view the log file.

Start a Simulation
– If running a simulation on the Amazon AWS Cloud:
• a Command Prompt window will open that will prepare the
setup, start the Amazon AWS instance and start the
simulation;
• a Windows batch script called oneClickCFD-...-monitor.bat is
created in the directory where the geometry file is located;
• Double-click on the batch script to monitor the simulation on
Amazon AWS Cloud;
• When the simulation is complete (whether it successfully
complete or failed), the results should automatically
downloaded in the directory as a file called
simulationid.tar.gz (where simulationid is a long list of
numbers and letters). This is an archive that you need to
extract locally using 7-zip (twice!). Then proceed to Post-
processing.

Post-processing
• The simulation
generates quite a
number of files:
Log file:
Store the software output and can be
used to check errors when the
simulation failed.
HTML file:
Automated result summary,
including drag, downforce, etc

Post-processing
• Automated post-
processed result
summary:
– HTML format;
– Overall drag,
downforce, etc;
– Residuals, etc;
– 3D pressure map;
– Drag and downforce
distributions.

Post-processing
• ParaView
– open-source post-
processing tool;
– Reads openFoam (the
CFD solver used in One-
Click CFD) results;
– Generate cuts, streamlines,
maps, etc by loading the
.foam file located in the
same directory as the
HTML file.
Download from
http://www.paraview.org/

One-Click CFD
Happy Modelling
&
Don't Forget the KVRC 2015 Challenge
Question(s)?
Contact us through the F1 Technical forum at
http://www.f1technical.net/forum/viewtopic.php?f=14&t=19456

One-Click CFD Users' Guide

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