Investigation of the starting process in a Ludwieg tube

The hypersonic Ludwieg tube Braunschweig (HLB) is a valve-controlled wind tunnel that has been designed for a Mach number of Ma = 5.9 and a Reynolds number range from 2.5 × 10⁶ up to 2.5 × 10⁷ 1/m. The intermittent working principle implies an unsteady onset of flow, which leads to a delay of the time frame suitable for measurements as well as to heat loads different from steady flow conditions. This work numerically simulates the starting process. It determines whether the onset of flow leads to a significant temperature rise in the model surface which in turn impacts results gathered during measurement time. The flow field in the HLB is numerically rebuilt for two operating points including valve opening. The non-stationary flow around a hyperboloid/flare configuration in the test section is calculated for one operating point including surface heating. For laminar flow it is found that due to the short duration of the starting process no significant model heating affects results obtained during measurement time.