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Need Some CFD Advice
Posted Thu December 11, 2003 @06:15PM
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Help Desk ken writes "I appreciate any sort of advice or guildlines here. I am using CFdesign to simulate the turning of a two bladed propeller. All experimental data is in NASA CR 196702. So basically this is a verification exercise.

I know in finite element space time decoupled formulation, the size of the time step affects both stability and accuracy. Here is the situation I have: In my first test case, I used this time step and get 90% matching in thrust and power. I consider that good enough. On the second case, initially using the same time step as test case 1, my converged solution only matches about 75% with experimental data. The difference between test case 1 & 2 is the case 2 has a higher propeller RPM, while the free stream Mach number and blade pitch setting is kept constant (To be more specific, M tip 1 = 0.77, M tip 2 = 0.89). The mesh of both cases are identical too. Therefore I decided to further reduce the time step and now i got 95% percent matching on thrust and power.

Here comes my question. How would I justisfy my approach of using different time step for the same type of analyses when I am dualing with real problems without known experimental data? Critics will shoot me on this "taking incosistent approach issue". So what should I reply them?"

( Post Comment )

The Growth of CFD
Posted Wed December 10, 2003 @10:08AM
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News Mechanical Engineering Magazine has posted a feature article about the growth of CFD from an academic interest to a heavily relied upon industrial tool.

The article also discusses the move toward combined CAD and CFD packages, a move which mirrors the development of FEA and allows for analysis during design.

"Historically, analysis has been relegated to the research and development departments, or the tail end of the design process," Vincent Harrand of CFD Research said. "Imagine the design engineer who, with minimal training or experience, can assess a series of geometrical variants or a series of unique approaches and determine within minutes fluid flow, heat transfer, thermal or structural stress, or any number of other physical phenomena."

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FLOMANIA Workshop Proceedings Available
Posted Tue December 09, 2003 @09:52AM
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News Proceedings are available from the FLOWMANIA project's recent workshop on detached-eddy simulation (DES) turbulence modeling. Detached-eddy simulation is a hybrid model containing both traditional Reynolds Averaged Navier Stokes (RANS) turbulence modeling, eg. k-epsilon, and more advanced large eddy simulation (LES) modeling.

RANS modeling is computationally efficient and is known to work well in attached boundary layer flows where the turbulent eddies are "attached". LES modeling, while significantly more expensive computationally, is known to work well in separated flows with "detached" eddies. The DES model is designed to use the RANS and LES modes where appropriate in the flowfield.

The proceedings detail the method and also show some interesting results which indicate the strong potential for this method.

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Business: Fluent to Open Global Operations Hub in India
Posted Mon December 08, 2003 @02:37PM
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News The US-based computational fluid dynamics (CFD) company, Fluent Inc, will make India its second hub for global operations.

The company will set up a research & development (R&D) centre in Maharashtra.

The $77 million company, which has been operating in the sub-continent and six other countries through its wholly owned subsidiary Fluent India Pvt Ltd (FIPL), will invest at least Rs 25 crore more during the next one year in its upcoming R&D centre in Pune.

The company had invested Rs 30 crore in India in the last fiscal year. The parent company is now gearing up to go public shortly.

Ferit Boysan, president and chief operating officer of Fluent Inc, said, “We will make India our second major hub next to our headquarters in New Hampshire in the US in the next five years. Our activities in this potential market has gained momentum only very recently and the revenues coming in from our Indian operations are not enough to expand our activities in this important market. So we have decided to keep investing in India through our parent company.”

( Read Full Article | Business )

Help Running CFX-4.4 Case
Posted Mon December 08, 2003 @11:59AM
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Help Desk Devin writes "hello to everyone,

I'm a user of CFX-4.4. How can I set the velocity on the "conducting solid". I can't find this option... I simulate a fluid flow into a horizontal channel, and the bottom of the channel is moving (similar to conveyer belt) and heated.

And if I set the velocity on it, is there anything need to be noticed? For example, moving grid, unmatched boundary, unmatched grid, etc.

Thank you for your help~~~

( Post Comment )

Help Running Fluent Case
Posted Sat December 06, 2003 @11:53AM
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Help Desk I have been running into one problem for the last 2 weeks. I am using Fluent to perform a compressible turbulence flow with time-dependent. I am not be able to do more than 10 time steps. If I did more than that, I would get an error massage. It said, "EOF on stderr". What exactly does it mean? How can I perform a simulation more than 10 time steps? I do not think that my mesh model has something wrong. Can you please give me some advice on this problem?
Best Regards,
Patinya Kayasit
University of Wisconsin-Milwaukee

( Post Comment )

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