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WHITEPAPER: Concurrent CFD Analysis Methods Boost Automotive Design Productivity A Strategic Engineering Tool for the Automotive Industry

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WHITEPAPER:

Concurrent CFD Analysis Methods Boost Automotive Design Productivity

A Strategic Engineering Tool for the Automotive Industry

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 2

Abstract

A new class of Computational Fluid Dynamics (CFD) analysis software, ‘Concurrent CFD’, is

proving to be highly effective at performing heat, fluid and airflow analyses, enabling Engineers to

accelerate key decisions at their workstations and without the need for CFD specialists. This

intuitive MCAD embedded process allows designers to optimize a product during the design stages

reducing manufacturing costs across a wide range of automotive parts and systems such as

heating, cooling, fuel delivery systems, braking systems, exhaust systems, body panels etc, etc.

Traditional and up-front CFD approaches have either been difficult, cumbersome or time

consuming in their use, but with Concurrent CFD, mechanical design teams can accelerate the

design process, increase their productivity workflow, reduce re-spins and increase profits. This

paper includes two case studies using Mentor Graphics Concurrent CFD technology for automotive

design applications.

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 3

It’s now common knowledge that

computer modeling/virtual prototyping in

the form of Computational Fluid

Dynamics (CFD) can make major

contributions in reducing product costs

and accelerating time to market.

However, many managers fail to realize

that the latest software advances are now

making these benefits both accessible and affordable to small- and mid-sized enterprises. This is

in part thanks to a new design/analysis technology known as ‘Concurrent CFD’, created by leading

simulation software company Mentor Graphics. Aimed specifically at the mechanical design

engineer, Mentor Graphics have introduced FloEFD, a Concurrent CFD software that is embedded

– concurrent, in a users MCAD system. With it there is no longer the need to hire or train CFD

specialists, outsource analysis to consultants, or conduct tests on expensive multiple physical

prototypes; instead, a design engineer - with standard training and working in any size company,

can use their existing knowledge to successfully perform flow and heat transfer analyses all within

their already familiar MCAD environment, helping increase workflow and dramatically reducing the

number of physical prototypes needed.

This breakthrough arose because FloEFD is able to simplify the process of setting up and running

a flow or heat transfer analysis. Certainly, there will always be a few very demanding applications

where a more advanced CFD knowledge is needed to fine-tune the meshing and solver settings in

order to converge to a solution. However, experience shows that using their existing knowledge,

design engineers with no specific training in CFD codes can correctly perform an analysis in

roughly 80% to 90% of the situations they encounter. This ability to take CFD out of the exclusive

domain of specialists and bring it into the mainstream represents a fundamental change in the

design process. Just as the shift from 2D to 3D CAD required a mental leap, so does FloEFD –

and the results are perhaps even more significant.

Because of these factors, the scope of applications for

CFD is expanding tremendously. Although many

managers in the automotive industry might think that

flow analysis is dedicated to studying the

aerodynamics of a vehicle’s exterior, this is only the

start of where FloEFD can be applied. Another

application that might come to mind is the study of

flow through a valve in order to size it or the air flow

through ventilation ducting to control cabin comfort temperatures. However, FloEFD is actually

being used to optimize the design and manufacture of a wide variety of parts such as pumps,

Using their existing knowledge, design

engineers with no specific training in CFD codes can

correctly perform an analysis in roughly 80% to 90% of the situations they

encounter.

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 4

braking systems, filters, fuel cells, manifolds, lights, transmissions and a multitude of other

components both mechanical and electrical. It is also important to note that fluid-flow effects

inevitably have a result on the movement of heat from a device or process and FloEFD is equally

good at studying these heating effects in components and systems of all sizes.

The purpose of simulation and modeling is to inform and confirm important decisions about an

emerging product, and to do so as early as possible in the design process. These benefits are

especially critical when the product in question is complex. Most Automotive-related products are

considered to have either “high” or “very high” complexity levels. The latter category can

encompass systems containing many thousands of individual parts. The development process can

span weeks or years, depending on the complexity of the end product; and with each passing day,

costs mount up. Figure 1 depicts the time and cost of prototypes at various levels of complexity. It

is important to note that this is not the whole project timeline, but only the portion devoted to

building a prototype.

The conclusion after examining Figure 1 is that it pays, literally, to avoid physical prototypes. Not

surprisingly, best-in-class companies strive to substitute virtual prototypes for physical ones as

much as possible. This is a fact that has been verified by pragmatic market research.

Figure 1: The cost of building physical prototypes. Source: Aberdeen Group study

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 5

Potential savings in the millions for just one project

The bottom line for procurement of any hardware or software for an engineering team is: Can it

save us time, can it save us money? FloEFD packages which cost in the range of $20,000 to

$30,000 for a perpetual license, can generally pay for themselves in the first project in which they

are used – with the benefits continuing on for years.

Convincing proof of this claim comes from a study conducted by the Aberdeen Group

(“Engineering Decision Support: Driving Better Product Decisions and Speed to Market”). The

study first compares 190 companies by means of several key performance criteria related to

meeting cost/revenue targets and hitting product-launch dates; it then categorizes the

organizations it studied into three groups: “best-in-class”, “industry average” and “laggards”.

Time and Cost Saved with 1.1 Fewer Prototypes

Source: Aberdeen Group, 2007

Table 1: A study by the Aberdeen Group shows that even with 1.1 fewer physical prototypes - made possible

by the use of virtual prototypes in software, the savings in both time and money are considerable.

Not surprisingly, the strategy adopted by best-in-class companies is to trade physical prototypes for

virtual ones as much as possible. These top companies conduct a mean number of 7.3 virtual iterations

whereas laggards perform only 2.8. The obvious consequence is that with fewer virtual prototypes, the

laggards need more physical prototypes: a mean of 3.8 for laggards compared to only 2.7 for best-in-

class organizations – 1.1 fewer physical prototypes. The savings accrued in these 1.1 fewer physical

prototypes can be enormous (see Table 1): For a product of low complexity, a cost savings

approaching $10,000; for a product of very high complexity, the savings are well over a million dollars!

Financial benefits also span the product’s useful lifetime. As stated by the AUTOSIM Consortium (a

project funded by the European Commission), a product that is six months late to market, even if on

budget, will generate an average of 33% less revenue during a 5-year period than it would if introduced

Product

Complexity

Number of

Parts

Length of

Development

Time Saved

(days)

Cost Saved ($)

Low <50 1 week – 1 year 14 $8,360

Moderate 50 – 1000 1 month –

5 years

26 $63,800

High 50 – 10,000 1 – 5 years 51 $143,000

Very High 1000 – 100,000 1 – 20 years 109 $1,320,000

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 6

on time and, as Figure 1 shows, having just one fewer physical prototypes can eliminate anything from

14 to 100 days from the project development timeline.

The key message today is that these time and cost

savings are now available to virtually every design

engineering team.

Awardwinning

FloEFD moves CFD into the mainstream

Although the computer modeling of engineering

systems is now available to every engineering team,

the underlying concept is nothing new. For

centuries, scientists have used mathematical

models to describe the world around us. Newton

and Leibnitz independently developed differential

calculus to allow them to add dynamics to models.

In fact, with a relatively simple model, Newton was

able to predict planetary orbits. This feat was so

revolutionary that it even challenged the then

current view of the universe.

In the following decades and centuries, researchers discovered the formulas that describe various

physical phenomena whether mechanical, structural, chemical or across the entire electromagnetic

spectrum. For the flow of a liquid or gas, the most basic relationships are the Navier-Stokes equations,

which were initially developed in the early 1800s. Their use was limited though, because realistic

problems became so complex that it was impossible to find an analytical solution and it became

necessary to find solutions using the brute force of approximate numerical methods – bringing what we

now know as Computational Fluid Dynamics.

Only with the emergence of computers in the 1950s did CFD studies start to become feasible, but they

were based on programs - also known as “codes”, developed and written by researchers, usually in

academia or government-sponsored programs. These codes were custom programmed for each

individual case. Only in the 1980’s did commercial codes become available to bring CFD to a wider

audience, but they also required specialists who could understand how to properly set up the software

such as getting a good mesh and then selecting the best solvers and tuning their results. Even so, with

such packages, engineers were able to model any flow field if they could define the geometry, identify

the underlying physics and prescribe some initial conditions.

The skills required to operate

FloEFD software are simply

knowledge of the CAD system and

the physics of the product, both of

which the vast majority of design

engineers already possess.

Engine water-cooling jacket

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 7

These early adopters started to solve a wide variety of problems with commercial CFD codes, and

providers of such software have used the past decade to refine the underlying meshers and solution

engines. The next step, taking place now, is to leverage these advances to achieve a breakthrough just

as significant as the introduction of the first commercial codes; the emergence of Mentor Graphics

Concurrent CFD technology and its software FloEFD.

FloEFD software was designed for use by everyday design engineers, not just specialists. It removes

all the barriers to the mainstream use of CFD. Until now, the greatest obstacle has been that traditional

CFD codes require users to have a deep understanding of the computational aspects of fluid dynamics

in order to obtain accurate results. In contrast, FloEFD’s groundbreaking features – its use of native 3D

CAD data, automatic definition of the flow space and the creation of a computational mesh for it, and the

management of flow parameters as object-based features – handled via a convenient wizard interface

eliminate the need for engineers to understand the computational side of CFD. Instead, they can focus

on the fluid dynamics of the product, an aspect that is already part of their responsibility and for which

they are trained and experienced. The skills required to operate FloEFD software are simply knowledge

of the CAD system and the physics of the product, both of which the vast majority of design engineers

already possess.

One major aspect that differentiates FloEFD is that it can be either fully embedded or at least tightly

integrated with most mechanical CAD packages engineers are familiar with.

After installation of the software, all the menus and commands necessary to run a full CFD flow or heat

analysis are created in the CAD packages menu system. This close interaction between the CAD and CFD

functions within FLOEFD - see Figure 2, brings with it several major benefits:

Engineers no longer have to export a file from their CAD environment into an analysis package or

spend time making the geometry “CFD-ready”, a process that can take hours, sometimes days.

Instead, FloEFD uses the same geometry the engineers have created in their mechanical CAD

package; any modifications to the CAD

geometry are carried over automatically to

the analysis.

Automatically detects the fluid regions of

interest; this contrasts to conventional CFD

software, which requires users to define the

computational domain of interest.

Transparently sets up and runs the mesher

and solver. CFD software, to be all things

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 8

to all people, offers a wide range of choices, most of which are never needed whereas FloEFD

software automatically chooses the appropriate solver and sets it up to find the solution.

Engineers do not have to worry about identifying when or where flow characteristics change

because FloEFD fully supports laminar, transition and turbulent flow.

It’s only necessary to set up the boundary conditions once; because of the unified environment,

these parameters remain fixed to the geometry unless the engineer chooses to modify them.

FloEFD also accelerates the iterative design process; engineers can quickly and easily incorporate

knowledge gained in an analysis into an improved design. With traditional CFD software, after

each geometrical change it is necessary to re-create the mesh which usually involves time-

consuming manual intervention. In contrast, FloEFD software operates immediately on the

changed geometry; creates a new mesh automatically, and works with the previously defined

boundary conditions. Thus, the step from a changed geometry to running the solver and

examining results is greatly accelerated.

The overall result is a much faster workflow with FloEFD that because of the tight integration of CAD and

CFD functions, eliminates the need to perform several steps in subsequent analysis runs.

Exhaust Manifold

Flow analysis of an intake manifold being performed within Pro/ENGINEER Wildfire – changes to the physical design are immediately available to the FloEFD software for analysis purposes.

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 9

With FloEFD, manufacturers can apply simulation at the concept stage so they can explore

design alternatives, detect design flaws, and optimize product performance before detailed

designs or physical prototypes are created. FloEFD also makes it easy to conduct “what-if”

analysis. Engineers can modify the solid model without having to re-apply loads, boundary

conditions and material properties. The software also aids in parametric analysis, for example,

running an analysis multiple times with various wall thicknesses in a valve to determine the

optimal thickness.

A multitude of applications

Until recently, a common thought among managers was, “I don’t see how FloEFD can help my

staff design their products better. After all, fluid flow isn’t a major factor in our designs.”

Meanwhile, best-in-class suppliers have discovered the enormous benefits of FloEFD go far

beyond traditional applications such as aerodynamics.

In the automobile industry alone, engineers use FloEFD software for optimizing the following

products and processes; Pressure drop in fuel injectors, heat transfer in radiators, fluid flow in

catalytic converters, exhaust and emission control systems, and:-

Under-hood airflow and thermal management

Passenger comfort and environmental control systems

Coolant flow in water jackets, engine blocks and cylinder heads

Cooling of electronic systems, braking systems, powertrain components, headlamps etc.

Performance of heat exchangers and heat sinks

Flow and pressure drop through filters

Fuel cell performance

Hydraulic systems

Vehicle Ventilation Vehicle Turbo

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 10

Aerodynamics of whole vehicles or components such as wing mirrors, windscreen wipers,

spoilers, etc.

It becomes clear that FloEFD can prove invaluable in many other industries beyond vehicle

manufacturing. In fact, there are very few industries or product areas that cannot benefit from

Mentor Graphics Concurrent CFD software!

Why Concurrent CFD Speeds Up a Designers Workflow, and a Company’s Profits

Figure 2 shows that in conventional CFD or as it is sometimes known, traditional CFD, the model

geometry is first captured and then exported from the users MCAD system. The geometry then

needs to be imported into the users CFD tool, cleaned, meshed, solved, the results post-

processed and then reported back to the design team. This work is usually done by a specialist

analysis group, or outsourced to a consultancy, so it’s necessary for the design team to

communicate accurately just what needs to be analyzed and how. However, by the time the

Figure 2. Diagram shows both Conventional and Upfront CFD need to Import/Export users MCAD geometry

to Third Party software for analysis during the design process. By comparison, Concurrent CFD is

embedded into the users existing MCAD design software.

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 11

results are captured and reported on, the analysis model has become ‘stale’, as the design – due

to time restrictions, has progressed, often making it difficult to act on the results. Any significant

changes to the model‘s geometry then need re-analyzing. The penalties of conventional and

traditional CFD are increased manpower, time and cost.

Upfront CFD attempts to improve this situation by aiming to streamline the interfacing between

the MCAD tool to the CFD tool. Usually this is done by incorporating a solid modeler within the

analysis suite. The result are a cleaner import of the geometry; However, the actual CFD analysis

process is still performed outside of the users MCAD system, so a user needs to learn a separate

and often complex piece of software, increasing a users learning curve and the products eventual

‘time-to-market’. It still carries the penalty of time, and the need to repeatedly export the

geometry from the MCAD software and re-import it into the CFD software.

Concurrent CFD operates very differently. Its MCAD embedded, so the work is performed within

the MCAD environment in an interface the user is already familiar with. Embedding CFD inside an

MCAD tool delivers very significant benefits. Design changes necessary to achieve the desired

product performance are made directly on the MCAD model, so the design is always up-to-date

with the analysis.

Figure 3. Diagram shows how both Conventional and Upfront CFD require extra workflow processes to perform their analysis programs. Embedded Concurrent CFD uses the ‘live’ MCAD geometry. This saves time and effort allowing the design to perform more iterations of a design in less time.

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 12

In Figure 3 it becomes apparent why concurrent CFD is different to conventional and upfront

CFD. By expanding the CFD workflow procedures, we can see they involve a number of process

steps to obtain a full analysis report on a design. Both conventional and upfront CFD require

geometry transferring from the MCAD system and cleaning it up so it’s suitable for analysis. This

process has to be repeated each time a design change occurs, to keep the MCAD geometry and

CFD analysis synchronized. Typically this approach will require the geometry’s fluid spaces to be

‘watertight’ for the analysis. In MCAD terms this is referred to as ‘healing’ the geometry to make it

‘manifold’, whereas analysts often refer to it as ‘cleaning the MCAD model’. This is a generic

requirement for CFD analysis, so it appears in all three approaches. Another process in both

conventional and upfront CFD is the “Create Cavity” step. Most conventional CFD meshing tools

work by meshing a solid, so they require a solid object to mesh. For a CFD simulation the solid

object is the flow space, which – for conventional and upfront CFD tools has to be created as a

dummy part within the MCAD system by Boolean subtraction of the entire model from an

encapsulating solid. This is usually done in the MCAD system and it’s this inverted flow space

that is transferred to the external third party CFD software for meshing and analysis.

By comparison, MCAD embedded concurrent CFD works rather differently. The geometry used

for the analysis is native to the MCAD system. This means that there is no geometry transfer step

because the designer never has to leave his/her MCAD software. Concurrent CFD therefore

eliminates the “transfer geometry” and “create cavity” steps, and effectively meshes in one step.

Meshing still takes place, but only takes minutes rather than hours of iterating back and forth.

This speeds up a user’s workflow, allowing them time to explore ‘what if’ optimization changes

which could enhance still further a designs reliability and overall manufacturing costs.

Concurrent CFD provides one final benefit that’s not shown in the diagram. As mechanical

designers undertake their own analyses they quickly learn how to build analysis-friendly geometry

within their MCAD software, further eliminating the “clean geometry” step, so the time savings can

be even greater than those indicated!

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 13

Users tell the story Vendors can make all the claims they want, but the true test of a software package’s value comes

when engineers tell about the benefits they receive. Here are just two stories from the thousands

of satisfied users now working with FloEFD software:

As explained earlier in this whitepaper, performing virtual

prototypes instead fabricating physical prototypes brings

enormous savings in time and costs. This was clearly the

experience of Ventrex Automotive GmbH in Graz, Austria.

This company is a supplier of compressors and air-

conditioning valves to all major automobile manufacturers.

One recent challenge was to develop valves suited for new CO2 refrigerants that are supplanting

those based on hydro fluorocarbons. These new fluids operate at pressures 7 to 10 times higher

and requires a redesign of many air-conditioning system components such as the valves used to

evacuate and charge the system. A key advantage of FloEFD is that the simulation describes the

pressure drop in a new design without the need to build a prototype; it also provides diagnostic

information such as the flow velocity and direction at every point in the flow field so engineers can

determine the optimal design.

Ventrex has long used CATIA, so they selected FloEFD V5, which integrates directly into that

CAD environment. Without leaving that mechanical CAD environment, Ventrex engineers could

simply execute a menu selection that invokes the FloEFD software to simulate the design using

the native CATIA data. It automatically identified the voids within the valve where fluids could

Ventrex Automotive: Eliminate

50 prototypes and reduce time

to market by 4 months

Figure 3: Valve production at Ventrex Automotive GmbH. FloEFD software cuts the time to market of a new valve by 4 months.

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 14

flow, and the engineers simply had to specify the boundary conditions, in this case the inlet and

outlet pressures. “Within a few hours we had a complete simulation of the initial concept design

and were able to turn our attention to improving it,” says the firm’s project manager.

The result? “CAD-embedded CFD makes it possible to determine simulation results nearly as

fast as we can change the design. We were able to improve the flow rate of our new CO2 valve

by 15% while eliminating roughly 50 prototypes and reducing time to market by 4 months.”

Miniature Precision Components: Quickly evaluate 12 design alternatives A recognized leader in the innovative design and production of world-class thermoplastic parts for

the automotive and commercial industries, Miniature Precision Components (MPC) supplies

functional thermoplastic injection, extrusion, and suction blow molded assemblies/subassemblies.

Headquartered in Walworth, Wisconsin, USA, the company has roughly 1500 employees.

As an interim step towards a long-term mandate for zero-emission vehicles, which will require the

production of vehicles driven by electricity or hydrogen fuel cells, several states in the USA allow

the licensing of partial zero-emission vehicles (PZEVs) that continue to use gasoline engines. In

order to qualify as a PZEV, a vehicle must meet the “super ultra low emission vehicle” standard

and have zero evaporative emissions from its fuel system. A key feature of a PZEV vehicle is a

hydrocarbon trap in the air intake that prevents stray hydrocarbons from migrating out of the

engine after shutdown -- but it must do so while avoiding a significant increase in backpressure

for air entering the engine because that would adversely affect fuel efficiency and performance.

In designing a cost-competitive hydrocarbon trap, engineers at MPC started by creating the

physical design as a CATIA model. They started by analyzing various rib configurations based

on experience. Doing so with FloEFD V5 software was easy because they simply defined the

boundary conditions and ran a flow analysis. They soon found that a 5-spoke version’s

backpressure was the lowest, but it was not low enough. The engineers then ran through roughly

a dozen iterations of the 5-spoke design, each time changing the spokes’ geometry and the

spacing of the carbon elements. Says the engineer in charge of this project, “By the end of this

process, I had beaten the target for backpressure, at least in the software. We built a rapid

prototype and found that its backpressure was within 0.1 in. of water of the CFD predictions.”

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 15

An easy step to dramatically higher productivity

FloEFD can make a large contribution to your efforts to reduce costs and speed time to market,

all while optimizing product design and thus customer satisfaction. The investment in the

software will most likely pay for itself in the first project:-

1. Because the software is embedded into the CAD system your engineers are already

familiar with

2. Because it is so intuitive to use, there is a very small short learning curve – engineers can

be productive with FloEFD software in a matter of hours.

If you are working with any of the following 3D CAD packages, which together dominate the

automotive market, we offer an integrated FloEFD solution that you can put to use immediately:

FloEFD V5: For CATIA V5

FloEFD Pro: For Pro/ENGINEER Wildfire

FloEFD: Here you import the CAD model into the FloEFD 3D environment and

immediately gain all the features and functionality of the FloEFD design and analysis

process. for virtually all other CAD package including:

Autodesk Inventor

Siemens NX

Solid Edge

CoCreate

SpaceClaim

Catalytic Converter

_________________________________________________________________________ Mentor Graphics: Accelerate Automotive Design with FloEFD 16

For detailed information…

Minimal investment, maximal gain: If your company isn’t already using FloEFD software, you

should be. Speak with your design team and encourage them to get in touch with us – we’ll

be happy to explain how they can get on board with this exciting new technology quickly and

easily.

For additional information, please contact:

Mentor Graphics Corp

Mechanical Analysis Division

81 Bridge Road Hampton Court Surrey KT8 9HH UK

Tel: +44 (0)20 8487 3000

Fax: +44 (0)20 8487 3001

[email protected]

Mentor Graphics Corp

300 Nickerson Road, Suite 200 Marlborough Massachusetts 01752 US

Tel: +1 (508) 480 0881

Fax: +1 (508) 480 0882

[email protected]

©2008 Mentor Graphics Corp. All rights reserved. All products mentioned are trademarks or trade names of their respective companies.