Spectral measurements of hypervelocity flow in an expansion tunnel

Abstract

Atmospheric reentry vehicles and planetary probes fly through the atmosphere at hypervelocity speed. At such speed, there is a significant proportion of heat load to the vehicle surface due to radiative heating. Accurate prediction needs a good knowledge of the radiation spectrum properties. In this paper, a high-speed camera and spectrograph coupled to an intensified charge-coupled device have been implemented to investigate the radiation flow over a semi-cylinder model. The experiments were carried out in the JF16 expansion tunnel with secondary shock velocity of 7.9 km·s⁻¹. Results show that the emission spectrum comprises several atomic lines and molecular band systems. We give detailed data of the radiation spectrum, shock shape, shock detached distance and radiation intensity varying with space and wavelength. This valuable experimental dataset will be helpful to validate computational fluid dynamics codes and radiation models, which equates to increased prediction accuracy of radiation heating. Also, some suggestions for spectral measurement in hypervelocity flow field were list in the end.

Appendix

1.1 A1: Image processing results of the shock wave position

t = 0 μs (Fig. 4a)		t = 33 μs (Fig. 4b)		t = 99 μs (Fig. 4c)		t = 132 μs (Fig. 4d)
x (mm)	y (mm)	x (mm)	y (mm)	x (mm)	y (mm)	x (mm)	y (mm)
− 0.075	− 48.131	9.522	− 48.680	10.223	− 48.545	15.788	− 48.572
− 3.126	− 46.385	5.817	− 46.934	7.172	− 46.799	11.212	− 46.826
− 4.870	− 44.639	2.983	− 45.188	4.121	− 45.053	8.378	− 45.080
− 6.831	− 42.893	0.368	− 43.442	1.288	− 43.307	4.674	− 43.334
− 8.793	− 41.147	− 2.683	− 41.696	− 1.545	− 41.561	1.840	− 41.588
− 10.536	− 39.401	− 5.080	− 39.950	− 3.507	− 39.815	− 0.993	− 39.842
− 12.280	− 37.655	− 6.606	− 38.204	− 5.904	− 38.069	− 3.826	− 38.096
− 14.023	− 35.909	− 8.785	− 36.458	− 8.301	− 36.323	− 6.659	− 36.350
− 15.331	− 34.163	− 10.746	− 34.712	− 10.263	− 34.577	− 8.838	− 34.604
− 16.856	− 32.417	− 12.708	− 32.966	− 12.006	− 32.831	− 11.236	− 32.858
− 17.946	− 30.671	− 14.233	− 31.220	− 14.186	− 31.085	− 13.633	− 31.112
− 19.254	− 28.925	− 16.413	− 29.474	− 16.147	− 29.339	− 15.377	− 29.366
− 20.343	− 27.179	− 17.502	− 27.728	− 18.108	− 27.593	− 17.120	− 27.620
− 21.433	− 25.433	− 19.682	− 25.982	− 19.852	− 25.847	− 18.646	− 25.874
− 22.741	− 23.687	− 21.425	− 24.236	− 20.941	− 24.101	− 20.389	− 24.128
− 23.612	− 21.941	− 22.733	− 22.490	− 22.467	− 22.355	− 21.479	− 22.382
− 24.702	− 20.195	− 23.823	− 20.744	− 23.557	− 20.609	− 22.568	− 20.636
− 25.574	− 18.449	− 24.912	− 18.998	− 24.864	− 18.863	− 23.876	− 18.890
− 26.663	− 16.703	− 26.002	− 17.252	− 25.954	− 17.117	− 24.966	− 17.144
− 27.535	− 14.957	− 27.092	− 15.506	− 27.044	− 15.371	− 26.055	− 15.398
− 28.407	− 13.211	− 27.745	− 13.760	− 27.262	− 13.625	− 27.145	− 13.652
− 29.061	− 11.465	− 28.399	− 12.014	− 28.569	− 11.879	− 27.363	− 11.906
− 29.497	− 9.719	− 29.053	− 10.268	− 29.005	− 10.133	− 28.235	− 10.160
− 30.150	− 7.973	− 29.489	− 8.522	− 29.659	− 8.387	− 28.671	− 8.414
− 30.586	− 6.227	− 29.925	− 6.776	− 29.877	− 6.641	− 29.106	− 6.668
− 30.586	− 4.481	− 30.143	− 5.030	− 30.095	− 4.895	− 29.292	− 4.922
− 30.804	− 2.735	− 30.361	− 3.284	− 30.095	− 3.149	− 29.331	− 3.176
− 31.022	− 0.989	− 30.361	− 1.538	− 30.095	− 1.403	− 29.178	− 1.430
− 31.022	0.757	− 30.361	0.208	− 30.095	0.343	− 29.215	0.316
− 30.804	2.503	− 30.143	1.954	− 30.095	2.089	− 29.106	2.062
− 30.368	4.249	− 30.143	3.700	− 29.877	3.835	− 28.888	3.808
− 30.368	5.995	− 29.707	5.446	− 29.659	5.581	− 28.888	5.554
− 29.932	7.741	− 29.489	7.192	− 29.223	7.327	− 28.671	7.300
− 29.497	9.487	− 29.053	8.938	− 28.787	9.073	− 28.453	9.046
− 28.843	11.233	− 28.617	10.684	− 28.351	10.819	− 27.581	10.792
− 28.189	12.979	− 27.963	12.430	− 27.480	12.565	− 26.927	12.538
− 27.753	14.725	− 26.874	14.176	− 26.826	14.311	− 26.055	14.284
− 27.099	16.471	− 26.002	15.922	− 25.736	16.057	− 25.184	16.030
− 26.445	18.217	− 24.912	17.668	− 24.646	17.803	− 24.094	17.776
− 25.574	19.963	− 23.823	19.414	− 23.557	19.549	− 22.568	19.522
− 24.702	21.709	− 22.733	21.160	− 22.467	21.295	− 21.479	21.268
− 23.612	23.455	− 21.207	22.906	− 20.941	23.041	− 19.735	23.014
− 22.523	25.201	− 19.900	24.652	− 19.852	24.787	− 18.646	24.760
− 21.433	26.947	− 18.156	26.398	− 18.108	26.533	− 16.902	26.506
− 20.125	28.693	− 17.067	28.144	− 16.801	28.279	− 14.723	28.252
− 19.036	30.439	− 15.323	29.890	− 14.621	30.025	− 12.543	29.998
− 17.946	32.185	− 13.362	31.636	− 12.878	31.771	− 10.364	31.744
− 16.420	33.931	− 11.400	33.382	− 10.916	33.517	− 7.749	33.490
− 14.895	35.677	− 9.221	35.128	− 8.737	35.263	− 4.916	35.236
− 12.934	37.423	− 7.042	36.874	− 6.122	37.009	− 2.082	36.982
− 11.626	39.169	− 4.644	38.620	− 3.725	38.755	1.187	38.728
− 9.882	40.915	− 2.247	40.366	− 1.763	40.501	4.674	40.474
− 7.921	42.661	0.150	42.112	1.288	42.247	8.378	42.220
− 5.960	44.407	2.330	43.858	5.429	43.993	12.519	43.966