Turbulence measurements for rough-wall boundary layers are presented and compared to those a smooth wall. The experiments were made on woven mesh surface at Reynolds numbers approximately equal the Fully rough conditions achieved. present work focuses turbulence structure, as documented through spectra of fluctuating velocity components, swirl strength, two-point auto- cross-correlations swirl. results in good agreement, both qualitatively quantitatively, with structure smooth-wall...

Turbulence measurements for a zero pressure gradient boundary layer over two-dimensional roughness are presented and compared to previous results smooth wall three-dimensional (Volino, Schultz & Flack, J. Fluid Mech ., vol. 592, 2007, p. 263). The present experiments were made on transverse square bars in the fully rough flow regime. turbulence structure was documented through fluctuating velocity components, two-point correlations of swirl strength linear stochastic estimation...

Detailed velocity measurements were made along a flat plate subject to the same dimensionless pressure gradient as suction side of modern low-pressure turbine airfoil. Reynolds numbers based on wetted length and nominal exit varied from 50,000 300,000, covering cruise takeoff conditions. Low high inlet free-stream turbulence intensities (0.2 7 percent) set using passive grids. The location boundary-layer separation does not depend strongly level or number, long boundary layer remains...

Measurements are presented from turbulent boundary layers over periodic two- and three-dimensional roughness. Cases with transverse rows of staggered cubes cases solid square bars two sizes were considered. Previous results by Volino, Schultz & Flack ( J. Fluid Mech . vol. 635, 2009, p. 75) showed outer-layer similarity between roughness smooth walls, deviations in large two-dimensional bars. The present show that differences also occur small to a lesser extent when the replaced cubes....

Oscillating vortex generator jets have been used to control boundary layer separation from the suction side of a low-pressure turbine airfoil. A low Reynolds number (Re=25,000) case with free-stream turbulence has investigated detailed measurements including profiles mean and fluctuating velocity turbulent shear stress. Ensemble averaged are computed for times within jet pulsing cycle, integral parameters local skin friction coefficients these profiles. The injected into mainflow at compound...

Boundary layer separation, transition and reattachment have been studied experimentally under low-pressure turbine airfoil conditions. Cases with Reynolds numbers (Re) ranging from 25,000 to 300,000 (based on suction surface length exit velocity) considered at low (0.5%) high (9% inlet) free-stream turbulence levels. Mean fluctuating velocity intermittency profiles are presented for streamwise locations all along the airfoil, turbulent shear stress provided downstream region where separation...

Pulsed film cooling was studied experimentally to determine its effect on film-cooling effectiveness. The jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical holes inclined at 35 deg surface flat plate considered blowing ratios 0.25, 0.5, 1.0, and 1.5 for variety pulsing frequencies duty cycles. Temperature measurements made an infrared camera, thermocouples, cold-wire anemometry. Hot-wire anemometry used velocity measurements. local...

A method for determining the wall shear stress under arbitrary streamwise pressure gradients and roughness conditions using Reynolds mean velocity profile data is presented. Data from very near are not required. The tested with experimental direct numerical simulation data.

Aiming to study the rough-wall turbulent boundary layer structure over differently arranged roughness elements, an experimental was conducted on flows with regular and random roughness. Varying planform densities of truncated cone elements in a square staggered pattern were investigated. The same also investigated arrangements. Velocity statistics measured via two-component laser Doppler velocimetry stereoscopic particle image velocimetry. Friction velocity, thickness, length zero-plane...

Two-dimensional rectangular bars have been used in an experimental study to control boundary layer transition and reattachment under low-pressure turbine conditions. Cases with Reynolds numbers (Re) ranging from 25,000 300,000 (based on suction surface length exit velocity) considered at low (0.5%) high (8.5% inlet) free-stream turbulence levels. Three different were considered, heights 0.2% 0.7% of length. Mean fluctuating velocity intermittency profiles are presented compared results...

A flow modification technique is introduced in an attempt to allow increased turbine inlet temperatures. large-scale two half-blade cascade simulator used model the secondary between adjacent blades. Various visualization techniques and measurements are verify that test section replicates of actual engine. Two employed modify endwall flow, specifically path passage vortex. Six jets installed at a location downstream saddle point near leading edge pressure side blade. These wall found be...

Boundary layer separation has been studied on a very high lift, low pressure turbine airfoil in the presence of unsteady wakes. Experiments were done under (0.6%) and (4%) freestream turbulence conditions linear cascade speed wind tunnel. Wakes produced from moving rods upstream cascade. Flow coefficients varied 0.35 to 1.4 wake spacing was one two blade spacings, resulting dimensionless passing frequencies F=fLj-te/Uave (f is frequency, Lj-te length adverse gradient region suction surface...

Blowing from the tip of a turbine blade was studied experimentally to determine if total pressure loss could be reduced. Experiments were done with linear cascade in low-speed wind tunnel. Total drop through row and secondary velocity fields passage between two blades measured. Cases documented various blowing hole configurations on flat squealer tipped blades. normal not helpful some cases increased losses. bottom cavity provided little benefit. With tip, holes located near inclined toward...

A model has been developed to incorporate more of the physics free-stream turbulence effects into boundary layer calculations. The transport in is modeled using three terms: 1) molecular viscosity, ν; 2) turbulent eddy εT, as used existing models; and 3) a new induced εf. terms are added give an effective total viscosity. viscosity algebraically with guidance from experimental data. It scales on rms fluctuating velocity free-stream, distance wall, thickness. assumes direct tie between...

A model has been developed to incorporate more of the physics free-stream turbulence effects into boundary layer calculations. The transport in is modeled using three terms: (1) molecular viscosity, ν; (2) turbulent eddy εT, as used existing models; and (3) a new free-stream-induced εf. terms are added give an effective total viscosity. viscosity algebraically with guidance from experimental data. It scales on rms fluctuating velocity free stream, distance wall, thickness. assumes direct tie...

Conditional sampling has been performed on data from a transitional boundary layer subject to high (initially 9%) freestream turbulence and strong (K=ν/U∞2dU∞/dx as 9×10−6) acceleration. Methods for separating the turbulent nonturbulent zone based instantaneous streamwise velocity shear stress were tested found agree. Mean profiles clearly different in zones, skin friction coefficients much 70% higher zone. The fluctuating velocity, contrast, was only about 10% Turbulent differed by an order...

Pulsed film cooling was studied experimentally to determine its effect on film-cooling effectiveness and heat transfer. The jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical holes inclined at 35 deg surface flat plate considered blowing ratios 0.25, 0.5, 1.0, 1.5 for variety pulsing frequencies duty cycles. Temperature measurements made an infrared camera thermocouples. equipped constant flux heaters, data acquired each flow condition both...

Film cooling flows subject to periodic wakes were studied experimentally. The generated with a spoked wheel upstream of flat plate. Cases single row cylindrical film holes inclined at 35deg the surface considered blowing ratios 0.25, 0.50, and 1.0 steady freestream wake Strouhal numbers 0.15, 0.30, 0.60. Temperature measurements made using an infrared camera, thermocouples, constant current (cold-wire) anemometry. Hot-wire anemometry was used for velocity measurements. local effectiveness...

Boundary layer separation, transition, and reattachment have been studied on a new, very high lift, low-pressure turbine airfoil. Experiments were done under low freestream turbulence conditions linear cascade in speed wind tunnel. Pressure surveys the airfoil surface downstream total pressure loss documented. Velocity profiles acquired suction side boundary at several streamwise locations using hot-wire anemometry. Cases considered Reynolds numbers (based length nominal exit velocity from...