Global Aeroheating Measurements of Shock-Shock Interactions on a Swept Cylinder

Abstract

The effects of fin leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. The cylindrical leading-edge fin models, with radii varied from 0.25 to 0.75 inches, represent wings or struts on hypersonic vehicles. A 9° wedge generated a planar oblique shock at 16.7° to the flow that intersected the fin bow shock, producing a shockshock interaction that impinged on the fin leading edge. The fin sweep angle was varied from 0° (normal to the free-stream) to 15° and 25° swept forward. These cases were chosen to explore three characterized shock-shock interaction types. Global temperature data were obtained from the surface of the fused silica fins using phosphor thermography. Metal oilflow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and any temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using a one-dimensional semi-infinite method, as well as one-and two-dimensional finite-volume methods. These results were compared to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for each explored shock-shock interaction type regardless of the leading-edge radius. However, the dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method. NomenclatureA = area (ft 2 ) c h = convective heat transfer coefficient (lb m /ft 2 -s) c P = specific heat capacity at constant pressure (BTU/lb m -°F) h = enthalpy (BTU/lb m ) k = thermal conductivity (BTU/hr-ft-°F) L = full length of the model leading edge (in.) M = Mach number n = number of time steps in finite-volume algorithm, or cells in the radial (nr) and lateral directions (nz) P = pressure (psi or psia) = heat transfer rate (BTU/hr) r = radial direction in cylindrical coordinates R = radius of the model (in.) Re = unit Reynolds number (1/ft) t = time (s) T = temperature (°F or °R) U = velocity (ft/s) V = volume (ft 3 )2 x, z = lateral direction in IHEAT (x) or cylindrical coordinates (z) ε = emissivity of phosphor-coated fused silica models σ = Stefan-Boltzmann constant (BTU/hr-ft 2 -°R 4 ) ρ = density (slug/ft 3 ) Subscripts: aw = adiabatic wall cond = conduction conv = convection d = known conditions at model surface FR = Fay-Riddell rad = radiation ref = reference from mean baseline heating t,1 = reservoir stagnation tw = tunnel wall w = wall (surface of model) ∞ = free-stream conditions Acronyms: AoA = angle of attack (degrees) BL = boundary layer BS = bow sho...