tion models, in spite of some advances, the boundary layer is still not represented realistically. Figure 1 illustrates an aspect of this problem by showing the opposing response of boundary layer (low) clouds to perturbation experiments (e.g., double CO2) in current climate models. The general problem of parameterization in fluids dates back to the first modern studies of turbulence during the...

In this paper an experimental and theoretical investigation is presented on the role of large-scale coherent structures in the zeropressure-gradient turbulent boundary layer. Attention is given to the proposal by Adrian, Meinhart & Tomkins (2000) that hairpin vortices are organized into spatially correlated packets or trains of vortices which extend over many boundary layer thicknesses in the s...

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...

Numerical simulation can provide a valuable tool in evaluating the characteristics of possible sites for new telescopes. This technique can provide accurate information about topographically induced atmospheric disturbances and turbulent boundary layers occurring in the high Reynolds number airflows over such sites. Results are given here for simulations of airflow at the two Gemini 8-m telesco...

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 (...