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ItemEvolution of zero pressure gradient turbulent boundary layers from different initial conditions( 2012)Turbulent boundary layers developing under zero pressure gradient (ZPG) condition are investigated experimentally with the overall aim of learning more about the streamwise evolution of these wall-bounded flows close to the quasi-equilibrium state (The definition of a quasi-equilibrium boundary layer is from Perry et al. [1994] where the wake parameter II is allowed to vary with streamwise distance but it is assumed that the wake gradient is sufficiently small so as to have negligible effect on the shear stress profiles). Scaling of the streamwise broadband turbulence intensity is also investigated. A key aspect of this study is obtaining high fidelity measurements at high Reynolds numbers over a large range of streamwise locations. This has required a novel hot-wire calibration technique. The research work also represents an effort to acquire very high quality ZPG turbulent boundary layer data ranging from Reт = δ Uт/ v ≈2740—22884 (here δ is boundary layer thickness, Uт is friction velocity and v is kinematic viscosity). The inner-normalized wire length l+ ≈ 23 ± 2 is maintained for Reynolds numbers Reт = 2740 —13320. This length increases to 29 and 38 for Reт = 17777 and 22884 respectively. To minimize the effect of changes in boundary conditions for different freestream velocities, the entire set of experiments were performed at three freestream velocities of 20m/s, 30m/s and 40m/s to maintain constant unit Reynolds number U∞/v ≈ 1.295 x 106, 1.91 x 106 and 2/50 x 106 m-1 respectively. Different Reynolds numbers were achieved at 10 different streamwise stations over a 27m long tunnel floor. Mean flow and higher order statistics such as broadband turbulence intensity, skewness, flatness as well as spectral measurements were made for all the Reynolds numbers. The logarithmic law of the wall provides a universal behaviour for the mean velocity profile in the inner region. Universal behaviour in the outer region is provided by the law of the wake. A new scaling is proposed for the streamwise Reynolds stress and energy spectra covering the inner, logarithmic and outer region. Comparisons are made with results from other experiments and numerical simulations. The research work also represents an effort to acquire very high quality ZPG turbulent boundary layer data ranging from Reт = δ Uт/ ѵ ≈2740—22884 (here δ is boundary layer thickness, Uт is friction velocity and ѵ is kinematic viscosity). The inner-normalized wire length l+ ≈ 23 ± 2 is maintained for Reynolds numbers Reт = 2740 —13320. This length increases to 29 and 38 for Reт = 17777 and 22884 respectively. To minimize the effect of changes in boundary conditions for different freestream velocities, the entire set of experiments were performed at three freestream velocities of 20m/s, 30m/s and 40m/s to maintain constant unit Reynolds number U∞/ѵ ≈ 1.295 x 106, 1.91 x 106 and 2/50 x 106 m-1 respectively. Different Reynolds numbers were achieved at 10 different streamwise stations over a 27m long tunnel floor. Mean flow and higher order statistics such as broadband turbulence intensity, skewness, flatness as well as spectral measurements were made for all the Reynolds numbers. The logarithmic law of the wall provides a universal behaviour for the mean velocity profile in the inner region. Universal behaviour in the outer region is provided by the law of the wake. A new scaling is proposed for the streamwise Reynolds stress and energy spectra covering the inner, logarithmic and outer region. Comparisons are made with results from other experiments and numerical simulations.