Wall-bounded turbulent flows at high Reynolds numbers have become an increasingly active area of research in recent years. Many challenges remain theory, scaling, physical understanding, experimental techniques, and numerical simulations. In this paper we distill the salient advances origin, particularly those that challenge textbook orthodoxy. Some outstanding questions, such as extent logarithmic overlap layer, universality or otherwise principal model parameters von Kármán “constant,”...

The overlap parameters for the logarithmic law are obtained available turbulent pipe and channel flow data using composite profiles fitted to mean velocity. profile incorporates κ, B, Π as varying their resulting behavior with Reynolds number is examined these flows compared results from boundary layers. von Kármán coefficient in smaller than well-established value zero pressure gradient layers of 0.384, while it consistently higher. In contrast, estimates wake parameter smallest largest...

An extensive set of experimental data, for zero pressure gradient boundary layers, over a wide range Reynolds number is re-evaluated with the help composite profile fitted to mean-velocity data. Boundary layer parameters such as Π, H and time scale ratio, Ω, are then carefully examined consistency among various experiments their dependence on number. Based predictions classical theory these parameters, several criteria established evaluate whether data can be classified 'well-behaved', i.e....

Two independent experimental investigations of the behavior turbulent boundary layers with increasing Reynolds number were recently completed. The experiments performed in two facilities, Minimum Turbulence Level (MTL) wind tunnel at Royal Institute Technology (KTH) and National Diagnostic Facility (NDF) Illinois (IIT). Both utilized oil-film interferometry to obtain an measure wall-shear stress. A collaborative study by principals experiments, aimed understanding characteristics overlap...

Smoke-wire flow visualization and hot-wire anemometry have been used to study near far wakes of two-dimensional bluff bodies. For the case a circular cylinder at 70 < Re 2000, very rapid (exponential) decay velocity fluctuations Kármán-vortex-street frequency is observed. Beyond this region decay, larger-scale (lower wavenumber) structure can be seen. In wake (beyond one hundred diameters) broad band frequencies selectively amplified then damped, centre shifting lower as downstream...

Flat plate turbulent boundary layers under zero pressure gradient at high Reynolds numbers are studied to reveal appropriate scale relations and asymptotic behaviour. Careful examination of the skin-friction coefficient results confirms necessity for direct independent measurement wall shear stress. We find that many previously proposed empirical accurately describe local Cf behaviour when modified underpinned by same experimental data. The variation integral parameter, H, shows consistent...

The asymptotic behavior of mean velocity and integral parameters in flat plate turbulent boundary layers under zero pressure gradient are studied for Reynolds numbers approaching infinity. Using the classical two-layer approach Millikan, Rotta, Clauser with a logarithmic profile overlap region between “inner” “outer” layers, fully self-consistent leading-order description all is developed. It shown that this fits most high number data, particular their dependence, exceedingly well; i.e.,...

This article is concerned with the mean velocity distributions of two-dimensional fully developed turbulent plane-channel flows. To yield reliable information, authors performed detailed hot-wire measurements for more than 12 Reynolds numbers. The experimental investigations covered a wide range numbers up to Reτ≈5×103, where Reτ based on wall friction and channel half-height. From distribution gradient (dU+/dy+)=f(y+) entire flow field was analyzed, resulting in logarithmic region profile...

AbstractThree-dimensional effects in turbulent duct flows, i.e., sidewall boundary layers and secondary motions, are studied by means of direct numerical simulation (DNS). The spectral element code Nek5000 is used to compute flows with aspect ratios 1–7 (at Reb, c = 2800, Reτ, ≃ 180) ratio 1 5600, 330), streamwise-periodic boxes length 25h. total number grid points ranges from 28 145 million, the pressure gradient adjusted iteratively order keep same bulk Reynolds centreplane changing ratio....

Accurate measurements of the turbulent wall pressure have been difficult to achieve due signal contamination at low frequencies by background facility noise and/or attenuation high sensor averaging effects. The current study utilizes a new cancellation scheme based on an optimal filtering technique capture noise-canceled time series. Furthermore, address high-frequency problem, number pinholes are utilized along with high-sensitivity micropbones obtain resolution down d + = du τ /v ≅2....

The effects of honeycomb different lengths on free-stream turbulence are studied in air with hot-wire anemometry and water using hydrogen bubbles visualization. honeycombs viewed as operators which suppress the level incoming generate, primarily through documented instabilities, new scales characteristic shear layers present their near wake. suppression appears to be mostly due inhibition lateral components fluctuating velocity. level, structure decay generated depends, part, instabilities...

Abstract This article reports on one component of a larger study measurement the zero-pressure-gradient turbulent flat plate boundary layer, in which detailed investigation was conducted suite corrections required for mean velocity measurements performed using Pitot tubes. In particular, shear across tube and blockage effects occur when is close proximity to wall were investigated from tubes five different diameters, two facilities, at Reynolds numbers ranging ${\mathit{Re}}_{\theta } =...

The secondary flow in wide turbulent ducts is characterized by means of high-order direct numerical simulations. New results indicate that or experimental facilities with aspect ratios larger than 10 may, if properly designed, exhibit good agreement obtained from spanwise-periodic channel computations.

The logarithmic law of the wall, joining inner, near-wall mean velocity profile (abbreviated MVP) in wall-bounded turbulent flows to outer region, has been a permanent fixture turbulence research for over hundred years, but there is still no general agreement on value pre-factor, inverse K\'arm\'an ``constant'' $\kappa$, or its universality. choice diagnostic tool locate parts MVP look regions where indicator function $\Xi$ (equal wall-normal coordinate $y^+$ times derivative $\dd U^+/\dd...

The events which are responsible for strong Reynolds-stress production in the near-wall region of a bounded turbulent shear flow have been investigated boundary layer at Reynolds number based on momentum thickness Re θ = 4650. coherent structures associated with process studied using quadrant detection technique. All three velocity components were measured three-dimensional sampling volume about point detection. conditional ensemble-averaged field sweep or an ejection is presented and...

Effects of screens and perforated plates (grids) on free-stream turbulence are studied in several test flow conditions. The level, structure decay the generated by such ‘manipulators’ depend part their shear-layer instabilities, can therefore be modified inserting additional devices immediately downstream. performance some is found to characteristics incoming as velocity, level spectra. Combinations very effective manipulators. By optimizing intermanipulator separation carefully matching...

The paper presents an in depth assessment of different similarity laws for the mean velocity profile zero pressure gradient (ZPG) turbulent boundary layers (TBL's) comparison with mostly experimental and few computational data. emphasis is on descriptions which are complete sense that a full representation profile, its streamwise evolution all integral parameters, including friction factor shape factor, provided as function Reynolds number. first such description classical two-layer theory...

Two sets of measurements utilizing hot-wire anemometry and oil-film interferometry for flat-plate turbulent boundary layers, exposed to various controlled adverse favourable pressure gradients, are used evaluate history effects the imposed varying free-stream gradients. The results from NDF wind tunnel at Illinois Tech (IIT) MTL KTH, over range $800 < Re_\tau 22\,000$ (where $Re_{\tau }$ is friction Reynolds number). streamwise pressure-gradient parameter $\beta \equiv (-\ell /\tau _{w})...

This paper presents experimental results on the nonlinear phase locking present in resonant growth of unstable modes shear layer an axisymmetric jet. The initial instability scale with exiting and grow convectively downstream distance. Because special condition at exit lip jet, is very sensitive to local unsteady pressure fields. A part field stochastic nature. To a larger extent, jet contains imprint downstream-developing modes, particular first mode its subharmonic. These are felt as...

There have been rising concerns regarding the accuracy of measurements in turbulent channel flows, particular, skin-friction results. In present study, two different methods, namely, mean streamwise pressure gradient (PG) and oil film interferometry (OFI), are used to estimate wall relation, cf = f(Rem), for fully developed plane-channel flow over a wide range Reynolds numbers. The data then fitted well-known logarithmic friction law, providing outstanding agreement with values constants law...

Although the equations governing turbulent flow of fluids are well known, understanding overwhelming richness phenomena, especially in high Reynolds number flows, remains one grand challenges physics and engineering. High turbulence is ubiquitous aerospace engineering, ground transportation systems, machinery, energy production (from gas turbines to wind water turbines), as nature, e.g. various processes occurring planetary boundary layer. not easily obtained laboratory, since order have...