cfd model of a spinning pipe gas lens
TRANSCRIPT
![Page 1: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/1.jpg)
CFD MODEL OF A SPINNING PIPE GAS LENS
SAIP
Dr Andrew Forbes
July 2006
G Snedden1, A Forbes2, C Mahlase1, C Mafusire3 and MM Michaelis4
1CSIR DPSS, PO Box 395, Pretoria
2CSIR National Laser Centre, PO Box 395, Pretoria
3University of Zimbabwe, Mount Pleasant, Harare
4University of Kwazulu-Natal, Durban
![Page 2: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/2.jpg)
Page 2 © CSIR 2006 www.csir.co.za
Spinning Pipe Gas Lens
![Page 3: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/3.jpg)
Page 3 © CSIR 2006 www.csir.co.za
Focal Length
78 C:f = 94.655w-1.1388
104 C:f = 138.94w-1.4796
125 C:f = 79.151w-1.3439
152 C:f = 197.55w-1.7476
0
1
2
3
4
5
6
7
8
9
6 8 10 12 14 16 18 20Pipe Speed,w (Hz)
Foc
al L
engt
h, f
(m
)
T=78 C
T=104 C
T=125 C
T=152 C
Power (T=78 C)
Power (T=104 C)
Power (T=125 C)
Power (T=152 C)
![Page 4: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/4.jpg)
Page 4 © CSIR 2006 www.csir.co.za
Refractive Index
1.0002
1.00021
1.00022
1.00023
1.00024
1.00025
1.00026
1.00027
1.00028
1.00029
1.0003
1.00031
-20 -15 -10 -5 0 5 10 15 20Radial Distance, r(mm)
Ref
ract
ive
Inde
x, n
(r)
78 C 104 C
125 C 153 C
Poly. (78 C) Poly. (104 C)
Poly. (125 C) Poly. (153 C)
![Page 5: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/5.jpg)
Gas Dynamics
![Page 6: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/6.jpg)
Page 6 © CSIR 2006 www.csir.co.za
Cold Air
WarmAir
Cold Air
WarmAir
WarmAir
Tube Rotation
Heater tape
WarmAir Opposing Vortices
Guess at the gas dynamics
![Page 7: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/7.jpg)
Page 7 © CSIR 2006 www.csir.co.za
Density Profile
![Page 8: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/8.jpg)
Page 8 © CSIR 2006 www.csir.co.za
Density Profile
![Page 9: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/9.jpg)
Page 9 © CSIR 2006 www.csir.co.za
Flow Profile
![Page 10: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/10.jpg)
Page 10 © CSIR 2006 www.csir.co.za
Rosby Waves
![Page 11: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/11.jpg)
Page 11 © CSIR 2006 www.csir.co.za
Rayleigh–Taylor Instabilities
![Page 12: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/12.jpg)
Future Work
![Page 13: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/13.jpg)
Page 13 © CSIR 2006 www.csir.co.za
Instabilities near the boundary
![Page 14: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/14.jpg)
Page 14 © CSIR 2006 www.csir.co.za
3/5
0
2
= rDNnmnmσ
)6/23()6/17()6/5()3/14()1()1(15337.0
2 +ΓΓ−ΓΓ+−=
−
nnn
Nmn
nm
∑∑∞
= =
+=Φ0 0
)],(),([),(n
n
m
mn
mn
mn
mn VBUA θρθρθρ
∫ ∫ Φ+=π
θρρθρθρπ
2
0
1
0),(),(
1)( ddUn
mKA mn
mn
∑−
=
−−+ −−
−−=2
0
2
22 )!()!(!)!()1(
)(
mn
k
kn
mnmn
kmn kkk
knR ρρ
3/5
220
max
min
)(423.0
−
= ∫
h
hn dhhCkr
3/112033.0)( −= κκφ nC
Wavefront Measurement & Control
![Page 15: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/15.jpg)
Page 15 © CSIR 2006 www.csir.co.za
Adaptive optics for turbulence correction
• SLM acts as an adaptive optic• Measure wavefront distortion,• Feed result back into SLM to create conjugate
phase,• Propagate conjugate phased beam through
medium.
Control Loop
![Page 16: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/16.jpg)
Page 16 © CSIR 2006 www.csir.co.za
Conclusion
• CFD model of gas lens• Shows Rosby waves and Rayleigh–Taylor instabilities
• Propagation model in preparation• Full Fresnel propagation through GRIN system
• Future work• Adaptive optics theory and experiment
![Page 17: CFD MODEL OF A SPINNING PIPE GAS LENS](https://reader030.vdocuments.us/reader030/viewer/2022012811/61c24fa4f40bdf363d3c919d/html5/thumbnails/17.jpg)
Questions