1. R=1D? ▬ Possibility of another standard geometry ▬ Masahiro Ishibashi
4th workshop CFVN, Poitiers
20 Sep., 2013
R=1D?
▬ Possibility of another standard geometry ▬
Masahiro Ishibashi
Gas Flow Standards Sec., Fluid Flow Div.,
NMIJ/AIST

2. Why R=2D? R=2D R=0.5D In the 21st Century, ...
We have excellent experimental facilities.
We have huge calculation powers.
R=0.5D

3. R=2D CFVNs (Common ISO-toroidal shape) aCURVE: laminar
nCURVE: Universal Curve
(turbulent)
sCURVE: aCURVE+nCURVE
(ISO)
(ISO)
(sigmoid function)

4. R=2D CFVNs
Stratford Calculations
aCURVE
nCURVE

5. R=1D CFVNs Theory (Stratford) Smaller jump by the transition.
Smaller sensitivity to the Reynolds number.

6. R=1D CFVNs has thinner boundary layer.
Two dimentional effect in core flow.

7. R=1D CFVNs Measurements Exactly on nCURVE! (coincidence???)
No transition observed up to 2x106.

8. 118 measuring points 5 CFVNs
R=1D CFVNs
118 measuring points CFVNs
bCURVE=nCURVE!
No Transition observed.

9. R=1D CFVNs
Meas. vs. Stratford
Theory for smal R is ...

10. R=1D CFVNs
Removed when obtaining bCURVE

11. R=1D CFVNs ^(-1/2) fit ^(-1/5) fit
Is it totally turbulent? (Very low transient Re?)
^(-1/2) fit
^(-1/5) fit
Can’t judge.

12. R=1D CFVNs ^(-1/2) fit ^(-1/5) fit
Is it totally turbulent? (Very low transient Re?)
^(-1/2) fit
^(-1/5) fit
Trends observed.
Can’t judge.

13. R=1D CFVNs ^(-1/2) fit ^(-1/5) fit ^(-1/5) fit is better?
Is it totally turbulent? (Very low transient Re?)
^(-1/2) fit
^(-1/5) fit
removed
^(-1/5) fit is better?

14. R=1D CFVNs ^(-1/5) fit ^(-1/2) fit
Is it totally turbulent? (Very low transient Re?)
^(-1/5) fit
^(-1/2) fit
removed
removed
still ^(-1/5) fit is better?

15. R=1D CFVNs Stable characteristics as in R=2D CFVNs.
Can be fitted by both ^(-1/2) and ^(-1/5)
Thinner boundary layer.
Robust boundary layer.
Lack of theory accuracy.
Another phenomenon?

16. Some Measurement Results
(No clear conclusions)

17. various R CFVNs R=1.0D R=2.0D R=1.5D R=1.8D R=2.5D R=1.3D R=1.2D

18. various R CFVNs Measurements R=2.5D R=2.0D R=1.8D R=1.5D R=1.3D R=1.2D
Almost the same
(Unfortunately, bad condition in CVTt system at that time.)

19. various R CFVNs
by Stratford
by Measurements

20. Theoretical predictions.
various R CFVNs
Theoretical predictions.
by Stratford
by Geropp-Hall
meas.

21. Inlet diameter?
Din=5D QI BS
Delayed transition!
Normal (Din=2.5D)

22. Inlet obstacle lower the transition Re?
(Din=5D)=‘QI’
Forced transition!
Obstacle (sample)
All R=1.5D
QI nozzle with the upstream obstacle.

23. Other Cd vs. Re Delayed tra? Tra! Delayed tra! Deviating!
Failed forced transition!
No tra! even with obstacle! ??

24. Inlet diameter does affect the transition.
Inlet nozzle holder diameter does affect the transition.