Large-scale unsteadiness lies at the heart of many of the design challenges associated with flight at high Mach numbers. Phenomena such as sound generation, fatigue loading, mixing, and separation are driven by turbulent motion on scales larger than the boundary layer thickness and longer than the boundary layer time scale /Ue,. This talk will focus on large-scale unsteadiness in attached a...

Wavefront measurements of a turbulent boundary layer were performed at the University of Notre Dame. Optical access windows to the tunnel were instrumented with 16 accelerometers to measure the tunnel-induced vibrations in the optical windows. A combination of spectral Proper Orthogonal Decomposition (POD) and Linear Stochastic Estimation (LSE) were used to remove vibration induced effects in t...

Three equilibrium-air numerical solutions are presented for the Reentry-F ight-test vehicle at Mach 20, 80,000 ft. conditions, including turbulent t o w predictions. The three solutions are from a thin-layer Navier-Stokes code, coupled thin-layer and parabolized Navier-Stokes codes, and an approximate viscous shock-layer code. Boundary-layer and shock-layer prooles are presented and compared be...

The direct numerical simulation (DNS) data of a turbulent, reacting boundary layer is used to study the turbulence-chemistry interaction and the scaling of the temperature fluctuations. We find that there is a feedback between the turbulence and the chemical reactions. Temperature fluctuations increase the reaction rates. Endothermic reactions reduce the magnitude of the temperature fluctuation...

The temporal response of a well-developed turbulent boundary layer to the superposition of oscillatory shear has been measured experimentally, over a wide range of frequencies. The response is primarily a periodic organization in magnitude of components of the turbulent velocity field at the forcing frequency. Oscillatory production of turbulence arises predominantly as a modulation of the mean...

We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which can calculate the timeand space-dependent skin-friction vector field at the wall, at the resolved scale. By combining the virtual-wall model with the stretched-vortex subgrid-scale (...

Direct numerical simulations are extended to see the effects of time-periodic blowing frequency from a spanwise slot on a turbulent boundary layer. The time-periodic blowing frequency is given in a range 0≤f≤0.08 at a fixed blowing amplitude of A=0.5. The effects of the blowing frequency are scrutinized by examining the phaseor time-averaged turbulent statistics. A most effective blowing freque...

An experimental investigation was conducted to quantify the characteristics of the turbulent boundary layer flows over a dimpled surface in comparison to those over a conventional flat plate. In addition to measuring surface pressure distributions to determine the friction factors of the test plates and to map the surface pressure inside the dimple cavity, a high-resolution digital particle ima...

The study of flow and heat transfer over rotating circular disks is of great practical importance in understanding the cooling of rotatory machinery such as turbines, electric motors and design and manufacturing of computer disk drives. This paper presents an analysis of the flow and heat transfer over a heated infinite permeable rough disk. Boundary-layer approximation reduces the elliptic Nav...