1 Introduction
2 Background of the shock wave test
2.1 Particle motion across a shock wave
2.2 Spatial and temporal resolution effects
2.3 Measurement dynamic range effects
τ
p
= 4 μs | τ
p
= 2 μs | |
---|---|---|
PIV measurement parameters | ||
FOV [px, mm] | 1,376 × 1,040, 7.9 × 6.0 | |
DR [px/mm] | 170 | |
M, M
n
| 2, 1.25 | |
SR (τ
p
= 4 μs, τ
p
= 2 μs) | 0.1 | 0.2 |
TR (τ
p
= 4 μs, τ
p
= 2 μs) | 0.2 | 0.3 |
Parameters related to the accuracy | ||
u
n∞
, ∆u
n
[px] | 15, 5 | 31, 9 |
ε(u
n∞
) [px, %] | 0.1, 0.3% | 0.05, 0.2% |
ln(u
nlim
*
) | −1.9 | −1.9 |
∆ln required | 1.5 | 1.6 |
N uncorr. | 4 | 12 |
ε
τ
= σ(p = 2) | 7% | 3% |
2.4 Disturbing factors: aero-optical aberrations and unsteady flow effects
3 Experimental apparatus and procedure
3.1 Wind-tunnel and model
3.2 PIV apparatus and data analysis
3.3 Flow seeding
Seeding identification | Material | Primary crystal size (nm) | Bulk density (g/l)a
|
---|---|---|---|
Degussa Aerosil R104 | SiO2
| 12 | ~50 |
Degussa Aerosil R972 | SiO2
| 16 | ~50 |
Kemira P170 | TiO2
| 14 | 150 |
Kemira P580 | TiO2
| 30 | 150 |
Kemira L830 | TiO2
| 50 | 200 |
Kemira 300 | TiO2
| 170 | 800 |
XRDI-S | TiO2
| 240 | 800 |
DuPont R931 | TiO2
| 550 | 3,636 |
4 Results and discussion
4.1 Mean relaxation time from PIV analysis
ID material | Seeder | Mean τ
p
(μs) | σ(τ
p
) (μs) | ||
---|---|---|---|---|---|
Stored (τ
H
) | De-hydrated (τ
Dh
) | Stored | De-hydrated | ||
DEHS | A | 1.92–2.02 | – | 0.40–0.38 | – |
SiO2R104 | C | 2.49 | 2.21 | 0.22 | 0.17 |
SiO2R972 | C | 2.64 | 2.29 | 0.19 | 0.28 |
TiO214 | C | 3.25 | 3.71 | 0.12 | 0.12 |
TiO230 | C | 2.56 | 2.20 | 0.11 | 0.07 |
TiO250 | C | 2.77 | 2.09 | 0.18 | 0.09 |
TiO250 | CF
| – | 0.56 | – | 0.10 |
SiO2R104 | CF
| – | 0.37 | – | 0.10 |
TiO250 | FL
| – | 1.36 | – | 0.05 |
TiO250 | FH
| – | 1.67 | – | 0.08 |
TiO2170 | C | 2.50 | 3.13 | 0.13 | 0.19 |
TiO2240 | C | 2.52 | 2.64 | 0.09 | 0.15 |
TiO2550 | C | 2.43 | 2.78 | 0.07 | 0.22 |
4.2 PTV analysis
Ti50 FH
| Ti50 CI
| TiO250 H | TiO250 Dh | SiO2R972 H | DEHS | TiO2300 Dh | |
---|---|---|---|---|---|---|---|
τ
p
max ± σ(τ
p
) (μs) | 1.2 ± 1.2 | 1.0 ± 0.8 | 2.0 ± 1.1 | 1.8 ± 1.4 | 2.0 ± 1.5 | 1.8 ± 1.4 | 2.4 ± 1.4 |
τ
p
PIV (μs) | 1.67 | 1.08 | 2.77 | 2.09 | 2.64 | 1.92 | 2.64 |