Experimental investigation of artificially generated disturbances in laminar hypersonic boundary layers

Experiments to study artificially generated disturbances in flat plate boundary layers were conducted in the Ludwieg-tube wind tunnel of the DLR in Goettingen at a free-stream Mach number of M_1=5. For the investigations, a 500 mm long and 20 mm thick flat plate model was used which spanned the test section 400 mm in width. As disturbance source a spark device flush mounted to the model surface close to its leading edge was utilized. The hot wire measurements in the boundary layer of the flat plate were conducted at different streamwise positions for natural and forced disturbances. The charge conditions used were almost constant at p_c_h_a_r_g_e=5 bar and T_c_h_a_r_g_e=393 K. This resulted in a unit Reynolds number of Re_1=8.45 x 10"6 1/m and a mass flow rate of #rho#_1 u_1=43.5 kg/m"2s. To check the flow quality of the tunnel and the laminar characteristic of the boundary layer optically, Schlieren pictures and high-speed shadowgraphs were taken prior to each measurement campaign. The artificially inserted wave packets were successfully measured at different distances and spanwise locations downstream of the park source. The main wave parameters, e.g. wave numbers and wave inclination angle were deduced from the obtained results. (orig.)SIGLEAvailable from TIB Hannover: RR 6926(98A29) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman