CFD Review  
Serving the CFD Community with News, Articles, and Discussion
 
CFD Review

User Preferences
Site Sponsorship
Headline Feeds
Mobile Edition
Privacy Policy
Terms of Service
twitter

Submit a CFD Story

Site Sponsors
Siemens PLM Software
Pointwise: Reliable CFD meshing
Software Cradle

Tell a Friend
Help this site to grow by sending a friend an invitation to visit this site.

CFD News by Email
Did you know that you can get today's CFD Review headlines mailed to your inbox? Just log in and select Email Headlines Each Night on your User Preferences page.

 
Need Some CFD Advice
Posted Thu December 11, 2003 @06:15PM
Print version Email story Tweet story
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?"


Sponsor CFD Review

[ Post Comment ]

The Growth of CFD | A New STAR is Born at AIAA Aerospace Sciences!  >

 

 
CFD Review Login
User name:

Password:

Create an Account

Related Links
  • NASA
  • More on Help Desk
  • Also by nwyman
  • This discussion has been archived. No new comments can be posted.

    The smallest worm will turn being trodden on. -- William Shakespeare, "Henry VI" All content except comments
    ©2017, Viable Computing.

    [ home | submit story | search | polls | faq | preferences | privacy | terms of service | rss  ]