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Gotowa bibliografia na temat „Turbulent Boundary Layer (TBL)”

Autor: Grafiati

Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Turbulent Boundary Layer (TBL)"

Savin, S., J. Büchner, G. Consolini, B. Nikutowski, L. Zelenyi, E. Amata, H. U. Auster i in. "On the properties of turbulent boundary layer over polar cusps". Nonlinear Processes in Geophysics 9, nr 5/6 (31.12.2002): 443–51. http://dx.doi.org/10.5194/npg-9-443-2002.

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Abstract. We study properties of nonlinear magnetic fluctuations in the turbulent boundary layer (TBL) over polar cusps during a typical TBL crossing on 19 June 1998. Interball-1data in the summer TBL are compared with that of Geotail in solar wind (SW) and Polar in the northern TBL. In the TBL two characteristic slopes are seen: ~ - 1 at (0.004- 0.08) Hz and ~ - 2.2 at (0.08-2) Hz. We present evidences that random current sheets with features of coherent solitons can result in: (i) slopes of ~ - 1 in the magnetic power spectra; (ii) demagnetization of the SW plasma in "diamagnetic bubbles"; (iii) nonlinear, presumably, 3-wave phase coupling with cascade features; (iiii) departure from the Gaussian statistics. We discuss the above TBL properties in terms of intermittency and self-organization of nonlinear systems, and compare them with kinetic simulations of reconnected current sheet at the nonlinear state. Virtual satellite data in the model current sheet reproduce valuable cascade-like spectral and bi-spectral properties of the TBL turbulence.

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Leehey, P. "Structural Excitation by a Turbulent Boundary Layer: An Overview". Journal of Vibration and Acoustics 110, nr 2 (1.04.1988): 220–25. http://dx.doi.org/10.1115/1.3269502.

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Thirty years of theoretical and experimental research have yet to resolve a number of questions regarding the vibratory response of, and acoustic radiation from, a structure excited by a turbulent boundary layer (TBL). The most important questions are: (a) Can the TBL be characterized as a Thevenin source—particularly when vibratory power flow into the structure is maximized at hydrodynamic coincidence? Alternatively, at what level does structural vibration fundamentally change the character of the TBL? (b) Is the low wave number portion of the wall pressure spectrum of dominant importance in structural excitation away from hydrodynamic coincidence? Or do structural discontinuities cause the convective ridge of wall pressure to be of greater practical interest? (c) Can one quantify the radiation from a turbulent boundary layer about a rigid finite body? Is it dipole or quadrupole? What is the role of fluctuating wall shear stress? Current research on dense fluid loading and on modeling the behavior of the TBL is yielding new, and sometimes surprising, answers to some of these questions. Free resonant structural vibration in the dense fluid limit and the use of a bounded, non-causal, Green function representing the TBL are two of the surprises discussed.

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Zhang, Jiaojiao, Shengna Liu i Liancun Zheng. "Turbulent boundary layer heat transfer of CuO–water nanofluids on a continuously moving plate subject to convective boundary". Zeitschrift für Naturforschung A 77, nr 4 (21.12.2021): 369–77. http://dx.doi.org/10.1515/zna-2021-0268.

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Abstract The turbulent boundary layer (TBL) heat transfer of CuO–water nanofluids on a continuously moving plate subject to convective boundary are investigated. Five different shapes of nanoparticles are taken into account. Prandtl mixing length theory is adopted to divide the TBL into two parts, laminar sub-layer and turbulent region. The numerical solutions are obtained by bvp4c and accuracy is verified with previous results. It is found that the transfer of momentum and heat in the TBL is more obvious in laminar sub-layer than in turbulent region. The rise of velocity ratio parameter increases the velocity and temperature while decreases the local friction coefficient. The heat transfer increases significantly with the increase of velocity ratio parameter, Biot number, and nanoparticles volume fraction. For nanoparticles of different shapes, the heat transfer characteristics are Nu x (sphere) < Nu x (hexahedron) < Nu x (tetrahedron) < Nu x (column) < Nu x (lamina).

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Satcunanathan, Sutharsan, Matthias Meinke i Wolfgang Schröder. "Impact of Porous Media on Boundary Layer Turbulence". Fluids 7, nr 4 (13.04.2022): 139. http://dx.doi.org/10.3390/fluids7040139.

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The subsonic flows around NACA 0012 aerofoils with a solid, a porous, and a poro-serrated trailing edge (TE) at a Reynolds number of 1 × 106 are investigated by a hybrid Reynolds-averaged Navier–Stokes (RANS)/large-eddy simulation (LES) approach. The porosity is treated by the method-of-volume averaging. In the RANS, a two-equation low Reynolds number k-ε turbulence model is modified to include the porous treatment. Similarly the equations in the LES are extended by the Darcy–Forchheimer model. The simulation is set up with the broadband turbulent boundary layer trailing edge (TBL-TE) noise prediction as a future objective in mind, i.e., the noise sources in the trailing edge region are captured by the LES. To enforce a physically realistic transition from an averaged RANS solution towards a resolved turbulent flow field, at the inflow of the LES coherent structures are generated by means of the reformulated synthetic turbulence generation (RSTG) method. For the poro-serrated TE, turbulence statistics vary in the spanwise direction between the two extremes of a pure solid and a rectangular porous TE, where porosity locally increases the level of turbulence intensity and alters the near wall turbulence anisotropy.

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LEE, SEUNG-HYUN, i HYUNG JIN SUNG. "Direct numerical simulation of the turbulent boundary layer over a rod-roughened wall". Journal of Fluid Mechanics 584 (25.07.2007): 125–46. http://dx.doi.org/10.1017/s0022112007006465.

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The effects of surface roughness on a spatially developing turbulent boundary layer (TBL) are investigated by performing direct numerical simulations of TBLs over rough and smooth walls. The Reynolds number based on the momentum thickness was varied in the range Reθ = 300 ∼ 1400. The roughness elements were periodically arranged two-dimensional spanwise rods, and the roughness height was k = 1.5θin, where θin is the momentum thickness at the inlet, which corresponds to k/δ = 0.045 ∼ 0.125, δ being the boundary layer thickness. To avoid generating a rough-wall inflow, which is prohibitively difficult, a step change from smooth to rough was placed 80θin downstream from the inlet. The spatially developing characteristics of the rough-wall TBL were examined. Along the streamwise direction, the friction velocity approached a constant value, and self-preserving forms of the turbulent Reynolds stress tensors were obtained. Introduction of the roughness elements affected the turbulent stress not only in the roughness sublayer but also in the outer layer. Despite the roughness-induced increase of the turbulent Reynolds stress tensors in the outer layer, the roughness had only a relatively small effect on the anisotropic Reynolds stress tensor in the outer layer. Inspection of the triple products of the velocity fluctuations revealed that introducing the roughness elements onto the smooth wall had a marked effect on vertical turbulent transport across the whole TBL. By contrast, good surface similarity in the outer layer was obtained for the third-order moments of the velocity fluctuations.

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LEE, JAE HWA, HYUNG JIN SUNG i PER-ÅGE KROGSTAD. "Direct numerical simulation of the turbulent boundary layer over a cube-roughened wall". Journal of Fluid Mechanics 669 (12.01.2011): 397–431. http://dx.doi.org/10.1017/s0022112010005082.

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Direct numerical simulation (DNS) of a spatially developing turbulent boundary layer (TBL) over a wall roughened with regularly arrayed cubes was performed to investigate the effects of three-dimensional (3-D) surface elements on the properties of the TBL. The cubes were staggered in the downstream direction and periodically arranged in the streamwise and spanwise directions with pitches of px/k = 8 and pz/k = 2, where px and pz are the streamwise and spanwise spacings of the cubes and k is the roughness height. The Reynolds number based on the momentum thickness was varied in the range Reθ = 300−1300, and the roughness height was k = 1.5θin, where θin is the momentum thickness at the inlet, which corresponds to k/δ = 0.052–0.174 from the inlet to the outlet; δ is the boundary layer thickness. The characteristics of the TBL over the 3-D cube-roughened wall were compared with the results from a DNS of the TBL over a two-dimensional (2-D) rod-roughened wall. The introduction of cube roughness affected the turbulent Reynolds stresses not only in the roughness sublayer but also in the outer layer. The present instantaneous flow field and linear stochastic estimations of the conditional averaging showed that the streaky structures in the near-wall region and the low-momentum regions and hairpin packets in the outer layer are dominant features in the TBLs over the 2-D and 3-D rough walls and that these features are significantly affected by the surface roughness throughout the entire boundary layer. In the outer layer, however, it was shown that the large-scale structures over the 2-D and 3-D roughened walls have similar characteristics, which indicates that the dimensional difference between the surfaces with 2-D and 3-D roughness has a negligible effect on the turbulence statistics and coherent structures of the TBLs.

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Tian, Hai Ping, Shao Qiong Yang i Nan Jiang. "Topological Characteristics of Coherent Structures in the Turbulent Boundary Layer Measured by Tomo-PIV". Advanced Materials Research 718-720 (lipiec 2013): 801–6. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.801.

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Database of time series of the instantaneous three-dimensional three-component (3D-3C) velocity vector field, measured by tomographic time-resolved PIV(Tomo-PIV) in a water tunnel, was analyzed to investigate spatial topologies of coherent structures in the turbulent boundary layer (TBL). A new concept of spatial locally averaged velocity structure function of turbulence is put forward to describe the spatial dilation or compression of the multi-scale coherent structures in the TBL. According to the physical mechanism of dilation or compression of multi-scale coherent vortex structures in the turbulent flow, a new conditional sampling method was proposed as well to extract the spatial topological characteristics of physical quantities of coherent structures, such as fluctuating velocities, velocity gradients, velocity strain rates and vorticity during the bursting process in the Tomo-PIV database. Furthermore, the anti-symmetric structures are the typical spatial topologies characteristics for the velocity gradients and vorticity during coherent structures burst.

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Shehzad, M., B. Sun, D. Jovic, Y. Ostovan, C. Cuvier, J. M. Foucaut, C. Willert, C. Atkinson i J. Soria. "Intense large-scale motions in zero and adverse pressure gradient turbulent boundary layers". Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (11.07.2022): 1–9. http://dx.doi.org/10.55037/lxlaser.20th.169.

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Proper orthogonal decomposition (POD) is used to study coherent structures in wall-bounded turbulent flows. The present study uses POD in turbulent boundary layers to determine the contributions of the intense large-scale motions (LSMs) to the Reynolds stresses. This study uses the 2C-2D PIV measurements of zero pressure gradient turbulent boundary layers (ZPG-TBL) at Re_{δ2} = 7750, and adverse pressure gradient turbulent boundary layer (APG-TBL) at β = 2.27 and Re_{δ2}= 16240, where Re_{δ2} is the momentum thickness based Reynolds number and β is the Clauser’s pressure gradient parameter. The measurements were obtained in the Laboratoire de Mécanique des Fluides de Lille (LMFL) High-Reynolds-Number (HRN) Boundary Layer Wind Tunnel, Lille, France. The snapshots of the flow field are segregated into those dominated by the intense and mild LSMs based on the intensity of the temporal coefficients of the first POD mode. The intense LSMs are further decomposed into high-momentum (HM) and low-momentum (LM) motions. The relative contributions of the HM motions to the Reynolds stresses are larger near the wall as compared to the LM motions. At the wall-normal distance of the displacement thickness (δ1), HM and LM motions have similar contributions. Beyond δ1, the LM motions have larger contributions with their peaks located closer to the displacement thickness height. This shows that in the presence of an APG, the turbulence activity is shifted closer to the displacement thickness height.

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Stroh, A., Y. Hasegawa, P. Schlatter i B. Frohnapfel. "Global effect of local skin friction drag reduction in spatially developing turbulent boundary layer". Journal of Fluid Mechanics 805 (20.09.2016): 303–21. http://dx.doi.org/10.1017/jfm.2016.545.

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A numerical investigation of two locally applied drag-reducing control schemes is carried out in the configuration of a spatially developing turbulent boundary layer (TBL). One control is designed to damp near-wall turbulence and the other induces constant mass flux in the wall-normal direction. Both control schemes yield similar local drag reduction rates within the control region. However, the flow development downstream of the control significantly differs: persistent drag reduction is found for the uniform blowing case, whereas drag increase is found for the turbulence damping case. In order to account for this difference, the formulation of a global drag reduction rate is suggested. It represents the reduction of the streamwise force exerted by the fluid on a plate of finite length. Furthermore, it is shown that the far-downstream development of the TBL after the control region can be described by a single quantity, namely a streamwise shift of the uncontrolled boundary layer, i.e. a changed virtual origin. Based on this result, a simple model is developed that allows the local drag reduction rate to be related to the global one without the need to conduct expensive simulations or measurements far downstream of the control region.

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Ismail, Umair. "Direct Numerical Simulation of a Turbulent Boundary Layer Encountering a Smooth-to-Rough Step Change". Energies 16, nr 4 (8.02.2023): 1709. http://dx.doi.org/10.3390/en16041709.

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Using a direct numerical simulation (DNS), we investigate the onset of non-equilibrium effects and the subsequent emergence of a self-preserving state as a turbulent boundary layer (TBL) encounters a smooth-to-rough (STR) step change. The rough surface comprises over 2500 staggered cuboid-shaped elements where the first row is placed at 50 θ0 from the inflow. A Reθ=4500 value is attained along with δk≈35 as the TBL develops. While different flow parameters adjust at dissimilar rates that further depend on the vertical distance from the surface and perhaps on δSTR/k, an equilibrium for wall stress, mean velocity, and Reynolds stresses exists across the entire TBL by 35 δSTR after the step change. First-order statistics inside the inner layer adapt much earlier, i.e., at 10–15 δSTR after the step change. Like rough-to-smooth (RTS) scenarios, an equilibrium layer develops from the surface. Unlike RTS transitions, a nascent logarithmic layer is identifiable much earlier, at 4 δSTR after the step change. The notion of equivalent sandgrain roughness does not apply upstream of this fetch because non-equilibrium advection effects permeate into the inner layer. The emergent equilibrium TBL is categorized by a fully rough state (ks+≈120–130; ks/k≈2.8). Decomposition of wall stress into constituent parts reveals no streamwise dependence. Mean velocity in the outer layer is well approximated by Coles’ wake law. The wake parameter and shape factor are enhanced above their smooth-wall counterparts. Quadrant analysis shows that shear-stress-producing motions adjust promptly to the roughness, and the balance between ejections and sweeps in the outer layer remains impervious to the underlying surface.

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Rozprawy doktorskie na temat "Turbulent Boundary Layer (TBL)"

Nironi, Chiara. "Concentration fluctuations of a passive scalar in a turbulent boundary layer". Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00964852.

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This experimental study analyses the dynamics of concentration fluctuations in a passive plume emitted by a point source within the turbulent boundary layer. We aim to extend the popular study of Fackrell and Robins (1982) about concentration fluctuations and fluxes from point sources by including third and fourth moments of concentration. We also further inquire into the influence of source conditions, such as the source size, source elevation and emission velocity, on higher order concentration moments. The data set is completed by a detailed description of the velocity statistics within the TBL, with exhaustive information on both the temporal and spatial structure of the flow. The experimental data-set has been used to test two different modeling ap- proaches: an analytical meandering plume model (in one and in three dimen- sions) and a Lagrangian stochastic micro-mixing model.

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Zhang, Yufang. "Coupled convective heat transfer and radiative energy transfer in turbulent boundary layers". Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00969159.

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If radiation plays an important role in many engineering applications, especially in those including combustion systems, influence of radiation on turbulent flows, particularly on the turbulent boundary layers, is still not well known. The objective is here to perform a detailed study of radiation effect on turbulent flows. An optimized emission-based reciprocal (OERM) approach of the Monte-Carlo method is proposed for radiation simulation using the CK model for radiative gas properties. OERM allows the uncertainty of results to be locally controlled while it overcomes the drawback of the original emission-based reciprocity approach by introducing a new frequency distribution function that is based on the maximum temperature of the domain. Direct Numerical Simulation (DNS) has been performed for turbulent channel flows under different pressure, wall temperatures and wall emissivity conditions. Flow field DNS simulations are fully coupled with radiation simulation using the OERM approach. The role of radiation on the mean temperature field and fluctuation field are analyzed in details. Modification of the mean temperature profile leads to changes in wall conductive heat fluxes and new wall laws for temperature when radiation is accounted for. The influence on temperature fluctuations and the turbulent heat flux is investigated through their respective transport equations whose balance is modified by radiation. A new wall-scaling based on the energy balance is proposed to improve collapsing of wall-normal turbulent flux profiles among different channel flows with/without considering radiation transfer. This scaling enables a new turbulent Prandtl number model to be introduced to take into account the effects of radiation. In order to consider the influence of radiation in the near-wall region and predict the modified wall law, a one-dimensional wall model for Large Eddy Simulation (LES) is proposed. The 1D turbulent equilibrium boundary layer equations are solved on an embedded grid in the inner layer. The obtained wall friction stress and wall conductive flux are then fed back to the LES solver. The radiative power term in the energy equation of the 1D wall model is computed from an analytical model. The proposed wall model is validated by a comparison with the former DNS/Monte-Carlo results. Finally, two criteria are proposed and validated. The first one is aimed to predict the importance of wall radiative heat flux while the other one predicts whether a wall model accounting for radiation in the near wall region is necessary. A parametric study is then performed where a k-ǫ model and a turbulent Prandtl number model are applied to simulate the velocity and temperature field of different channel flows under various flow conditions. The obtained criteria values are analyzed and compared.

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Ben, Nasr Ouissem. "Numerical simulations of supersonic turbulent wall-bounded flows". Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-01059805.

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This work deals with spatially-evolving supersonic turbulent boundary layers over adiabatic and cold walls at M∞ = 2 and up to Re0 ≈ 2600 using 3 different SGS models. The numerical methodology is based on high-order split-centered scheme to discretize the convective fluxes of the Navier-Stokes equations . For the adiabatic case, it is demonstrated that all SGS models require a comparable minimum grid-refinement in order to capture accurately the near-wall-turbulence. Overall, the models exhibit correct behavior when predictiong the dynamic properties, but show different performances for the temperature distribution in the near-wall region. For the isothermal case, it is found that the compressibility effects are not enhanced due to the wall cooling. As expected, the total temperature fluctuations are not negligible in the near-wall region. The study shows that the anti-correlation linking both velocity and temperature fields, derived from the Morkovin's hypothesis, is not satisfied.

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Liu, Bilong. "Acoustical Characteristics of Aircraft Panels". Doctoral thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4102.

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Ma, Wei. "Experimental investigation of corner stall in a linear compressor cascade". Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00728374.

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In applied research, a lack of understanding of corner stall, i.e. the three-dimensional (3D) separation in the juncture of the endwall and blade corner region, which has limited the efficiency and the stability of compressors. Both Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) still need to be calibrated for turbomachinery applications. In the fundamental research of the turbulent boundary layer (TBL), there are a lot of findings of the effects of curvature and pressure gradients, which also play an important role in physics of corner stall. The purpose of this thesis is (i) to carry out an experiment in a cascade, (ii) to gain a database that could be used to calibrate both RANS and LES, and (iii) to give some basic explanations of corner stall through investigating the TBL on the suction side at the mid-span which is more complex than those in the basic investigations but simpler than those in a real engine. A detailed and accurate experiment of 3D flow field through a linear compressor cascade has been set up. Experimental data were acquired for a Reynolds number of 3.82×10 ^5 based on blade chord and inlet flow conditions. Measurements have been achieved by hot-wire anemometry, pressure taps on blade and endwall, five-hole pressure probe, oil visualization, 2D particle image velocimetry (PIV),and two-component laser Doppler anemometry (LDA). An original and complete database was thus obtained. The TBL on the suction side at mid-span was investigated. The wall-normal negative pressure gradient restrains the separation, on the contrary to its influence in the corner stall. The streamwise adverse pressure gradient can be responsible for the development of Reynolds stresses. The remarkable phenomenon at measurement stations near the trailing edge of blade is that an inflection point occurs in each profile of the mean streamwise velocity. At this inflection point, the magnitudes of the Reynolds stresses reach their maximum values, and the direction of energy diffusion also changes. The velocity field in the corner stall was presented. Bimodal histograms of velocity exist in the experiment. The bimodal points mainly appear in the region around the mean interface of separated flow and non-separated flow. At a bimodal point the local two velocity components are non-independent from each other, due to the aperiodic interplay of two basic modes in the flow field. Two modes were proposed to interpret the physics of bimodal behaviour.

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Lögdberg, Ola. "Turbulent Boundary Layer Separation and Control". Doctoral thesis, KTH, Linné Flow Center, FLOW, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9821.

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Boundary layer separation is an unwanted phenomenon in most technical applications, as for instance on airplane wings, ground vehicles and in internal flow systems. If separation occurs, it causes loss of lift, higher drag and energy losses. It is thus essential to develop methods to eliminate or delay separation.In the present experimental work streamwise vortices are introduced in turbulent boundary layers to transport higher momentum fluid towards the wall. This enables the boundary layer to stay attached at larger pressure gradients. First the adverse pressure gradient (APG) separation bubbles that are to be eliminated are studied. It is shown that, independent of pressure gradient, the mean velocity defect profiles are self-similar when the scaling proposed by Zagarola and Smits is applied to the data. Then vortex pairs and arrays of vortices of different initial strength are studied in zero pressure gradient (ZPG). Vane-type vortex generators (VGs) are used to generate counter-rotating vortex pairs, and it is shown that the vortex core trajectories scale with the VG height h and the spanwise spacing of the blades. Also the streamwise evolution of the turbulent quantities scale with h. As the vortices are convected downstream they seem to move towards a equidistant state, where the distance from the vortex centres to the wall is half the spanwise distance between two vortices. Yawing the VGs up to 20° do not change the generated circulation of a VG pair. After the ZPG measurements, the VGs where applied in the APG mentioned above. It is shown that that the circulation needed to eliminate separation is nearly independent of the pressure gradient and that the streamwise position of the VG array relative to the separated region is not critical to the control effect. In a similar APG jet vortex generators (VGJs) are shown to as effective as the passive VGs. The ratio VR of jet velocity and test section inlet velocity is varied and a control effectiveness optimum is found for VR=5. At 40° yaw the VGJs have only lost approximately 20% of the control effect. For pulsed VGJs the pulsing frequency, the duty cycle and VR were varied. It was shown that to achieve maximum control effect the injected mass flow rate should be as large as possible, within an optimal range of jet VRs. For a given injected mass flow rate, the important parameter was shown to be the injection time t1. A non-dimensional injection time is defined as t1+ = t1Ujet/d, where d is the jet orifice diameter. Here, the optimal t1+ was 100-200.
QC 20100825

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Hystad, Ida. "Numerical Modelling of Turbulent Boundary Layer". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26365.

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Most physical problems involving viscous fluid flows are characterized by turbulence where instabilities and large velocity gradients generate fluctuations in the flow field. Towed sonar arrays are exposed to turbulence in the boundary layer formed around the cable. Problems are related to the cable rotating around its own axis due to variations in tension force caused by the towing vehicle. Numerical calculations of a pressure driven flow along a cylinder are performed for the purpose of investigating the turbulent boundary layer around the cable. In this study, the numerical software OpenFOAM has been used in order to solve the flow field. The Reynolds Average Navier-Stokes (RANS) approach was applied, providing a time-average solution of the flow quantities. The results were used in a comparative study with data obtained from Large Eddy Simulation (LES). Simulations were carried out for two Reynolds numbers based on the shear velocity; Re_tau=[240,550]. The cylinder was assigned two different rotational velocities in addition to a case with zero rotation. Results show that the normalized mean velocity profile is in good agreement with the universal law-of-the-wall and previous published data. Comparison with LES data indicated good agreement with Reynolds shear stresses and the normalized mean velocities in the case of a non-rotating cylinder. However, deviations were observed when rotation was applied. In order to ensure the quality of the numerical results a convergence study was performed. Special attention was paid to the near-wall region in order to capture all levels of the boundary layer.

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Lögdberg, Ola. "Turbulent boundary layer separation and control /". Stockholm : Mekanik, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9821.

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Miller, Teresa S. "Turbulent boundary layer models for acoustic analysis". Diss., Wichita State University, 2011. http://hdl.handle.net/10057/3933.

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An analysis of the three types of turbulent boundary layer (TBL) models for acoustic analysis is presented because current preferred models over-predict TBL contributions to aircraft interior noise predictions. The mean square pressure is a measure of the total energy due to the pressure fluctuations beneath a turbulent boundary layer. The single point wall pressure spectrum sorts the energy into frequencies. The normalized wavenumber-frequency spectrum sorts the energy into wavenumbers. The pressure fluctuations beneath a turbulent boundary layer are found by solving the Poisson equation. In this work, the Poisson equation is solved both numerically and analytically using data from an LES/DES simulation. The numerical solution uses the point Gauss-Seidel method and has reasonable results. The analytical solution uses an eigenvalue expansion method that is less successful. The empirical mean square pressure models predict a relatively large spread in the pressure fluctuation values. It is difficult to draw any meaningful conclusions on which mean square pressure model is preferred when compared to data from the Spirit AeroSystems 6x6 duct. The single point wall pressure spectrum models are evaluated and the two more modern models of Smol’yakov and Goody seem to perform the best. These models are also compared to data from the Spirit AeroSystems 6x6 duct. The spectrum at low frequencies rolled off similar to the Goody model. This analysis indicates that the Goody model is the appropriate single point wall pressure spectrum model for aircraft applications. Important features of the normalized wavenumber-frequency spectrum models are presented and can be classified as either separable or non-separable. Separable models in the Corcos normalized wavenumber-frequency spectrum model class tend to over-predict the response for a range of cases. Both the non-separable Chase 1 and Smol’yakov-Tkachenko models appear to match the M.I.T. low noise, low turbulence wind tunnel data throughout the range of comparison. The Smol’yakov-Tkachenko model does not lend itself to straight forward Fourier transforms needed by the acoustic models. But the Chase 1 model can be converted from wavenumber-frequency spectrum to the cross spectrum, so it is the preferred model for aircraft applications. Therefore, the preferred turbulent boundary layer models for aircraft interior noise predictions are the single point wall pressure spectrum model of Goody and the normalized wavenumber-frequency spectrum model of Chase 1.
Dissertation (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

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Shaikh, F. N. "Turbulent spots in a transitional boundary layer". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319596.

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Książki na temat "Turbulent Boundary Layer (TBL)"

Boundary layer analysis. Englewood Cliffs, N.J: Prentice Hall, 1993.

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Boundary layer analysis. Reston, Va: American Institute of Aeronautics and Aeronautics, 2010.

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Schetz, Joseph A. Boundary layer analysis. Wyd. 2. Reston, Va: American Institute of Aeronautics and Astronautics, 2011.

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1945-, Harloff G. J., i Lewis Research Center, red. Hypersonic turbulent wall boundary layer computations. Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, 1988.

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1940-, Rahman M., red. Laminar and turbulent boundary layers. Southampton: Computational Mechanics Publication, 1997.

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Center, Ames Research, red. The kinematics of turbulent boundary layer structure. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1991.

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Mouskos, Michael. Droplet growth in turbulent boundary layer clouds. Manchester: UMIST, 1997.

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Otto, S. R. Fully nonlinear developent of the most unstable Go rtler vortex in a three dimensional boundary layer. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1992.

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Zaman, K. B. M. O., Reshotko Eli i United States. National Aeronautics and Space Administration., red. Turbulent heat flux measurements in a transitional boundary layer. [Washington, DC]: National Aeronautics and Space Administration, 1992.

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Zaman, K. B. M. Q., Reshotko E i United States. National Aeronautics and Space Administration., red. Turbulent heat flux measurements in a transitional boundary layer. [Washington, DC]: National Aeronautics and Space Administration, 1992.

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Części książek na temat "Turbulent Boundary Layer (TBL)"

Schlichting, Herrmann, i Klaus Gersten. "Fundamentals of Turbulent Flows". W Boundary-Layer Theory, 495–515. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_16.

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Schlichting, Herrmann, i Klaus Gersten. "Unsteady Turbulent Boundary Layers". W Boundary-Layer Theory, 643–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_21.

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Schlichting, Herrmann, i Klaus Gersten. "Turbulent Free Shear Flows". W Boundary-Layer Theory, 651–77. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-85829-1_22.

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Schlichting, Hermann, i Klaus Gersten. "Fundamentals of Turbulent Flows". W Boundary-Layer Theory, 499–518. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-52919-5_16.

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Schlichting, Hermann, i Klaus Gersten. "Unsteady Turbulent Boundary Layers". W Boundary-Layer Theory, 645–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-52919-5_21.

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Schlichting, Hermann, i Klaus Gersten. "Turbulent Free Shear Flows". W Boundary-Layer Theory, 653–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-52919-5_22.

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Sreenivasan, K. R. "The turbulent boundary layer". W Lecture Notes in Engineering, 159–209. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-83831-6_4.

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Sychev, Vladimir V. "On Turbulent Boundary-Layer Separation". W Boundary-Layer Separation, 91–107. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83000-6_6.

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Melnik, R. E. "A new Asymptotic Theory of Turbulent Boundary Layers and the Turbulent Goldstein Problem". W Boundary-Layer Separation, 217–34. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83000-6_13.

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Gaudet, L. "Visualisation of Boundary Layer Transition". W Laminar-Turbulent Transition, 699–704. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-84103-3_66.

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Streszczenia konferencji na temat "Turbulent Boundary Layer (TBL)"

Hambric, Stephen A., Yun Fan Hwang i William K. Bonness. "Vibrations of Plates With Clamped and Free Edges Excited by Highly Subsonic Turbulent Boundary Layer Flow". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32224.

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Plate vibrations due to turbulent boundary layer (TBL) excitation can depend strongly on the plate boundary conditions, especially when the flow convects over the plate at speeds much slower than those of the bending waves in the plate. The vibration response of a TBL excited flat rectangular plate is analyzed with two sets of boundary conditions: (A) all four edges clamped, and (B) three edges clamped and one edge free, with the flow direction perpendicular to the free edge. A finite element model with discretization sufficient to resolve the convective wavenumbers in the flow excitation field is used for the study. Three TBL wall pressure excitation models are applied to the plates to represent the cross-spectra of the wall pressures: (1) a modified Corcos model, which includes all wavenumber components of excitation; (2) a low-wavenumber excitation model previously derived by one of the authors, which only models the wavenumber-white region of the modified Corcos model; and (3) an equivalent edge force model which only models the convective component in the modified Corcos model. The TBL wall pressure autospectrum is approximated using the model derived by Smolyakov and Tkachenko. The results obtained from applying models (2) and (3) to the clamped and free edge plates are compared to those generated using model (1). For the completely clamped boundary conditions, the low-wavenumber and Modified Corcos models yield nearly identical vibration spectra, indicating that surface interactions dominate the response of fully clamped plates excited by TBL pressures. For the free edge boundary condition, the vibrations predicted using the equivalent edge force and modified Corcos models match very well, showing that edge interactions between TBL pressures and structural modes dominate the vibrations of plates with free edges excited by TBL flow.

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Mendoza, Jeff M., i Hoang Pham. "Elastic Response of a Submerged Plate Coated With Multiple Layers of Elastomeric Materials in the Presence of a Turbulent Boundary Layer". W ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0179.

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Abstract This study addresses the elastic response of a submerged plate coated with multiple layers of elastomeric materials. of interest is the extent at which the mechanism of interaction between dissimilar elastomers can be modified through selection of material properties. Such modification can optimize the received signal response at the sensors in the presence of a turbulent boundary layer (TBL) as well as provide insight into advantageous TBL and structure-borne vibration decoupling configurations. The analytical model is an infinite multilayer composite of steel and viscoelastic materials separating the semi-infinite media of water (external) and air (internal). The theory of elasticity expedites the analysis of elastic response, governed by dilatational and shear motion, in each layer. The analysis considers excitation by an incident plane wave in addition to a fully developed TBL both in the water medium. A series of numerical simulations based on material properties of well-characterized elastomers quantify the degree at which this coupling mechanism can be optimized in applications of noise and vibration reduction.

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Katz, Richard A., Thomas A. Galib i Joan Cembrola. "Application of nontraditional processing methods to transitional and turbulent boundary layer (tbl) flow-noise-induced signals". W SPIE's 1993 International Symposium on Optics, Imaging, and Instrumentation, redaktor Louis M. Pecora. SPIE, 1993. http://dx.doi.org/10.1117/12.162682.

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Winkel, E. S., B. R. Elbing, D. R. Dowling, S. L. Ceccio i M. Perlin. "High-Reynolds-Number Turbulent-Boundary-Layer Surface Pressure Fluctuations With Bubble or Polymer Additives". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79740.

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This paper reports multi-point dynamic pressure fluctuation measurements made beneath a high-Reynolds-number turbulent boundary layer (TBL) with wall-injection of air or polymer additives for the purpose of skin-friction drag reduction. Two independent experiments were conducted in the U.S. Navy’s Large Cavitation Channel (LCC) on a 12.9 m long, 3.05 m wide hydro-dynamically smooth (k+ < 1) flat plate at free-stream speeds from 6.5 to 20.0 m/s. The first, a bubble drag reduction experiment (BDR), involved injecting gas at flow rates ranging from 100 to 800 CFM (17.8 to 142.5 liter/s per meter of injector span) from one of two injectors located 1.32 and 9.78 m from the model leading edge. The second, a polymer drag reduction experiment (PDR), involved injecting polymer from a single slot injector, 1.32 m from the leading edge, at flow-rates ranging from 6 to 30 GPM (0.14 to 0.71 liter/s per meter of injector span). Dynamic pressure measurements were made with 16 flush-mounted transducers in “L”-shaped arrays located 10.7 and 9.8 m (70 × 106 < ReX < 210 × 106) from the leading edge for the BDR and PDR experiments, respectively. Measurements show modifications in the spectra, stream-wise coherence, and convection velocity of the pressure fluctuations due to the presence of gas or polymer in the near-wall region of the TBL. At the dynamic pressure measurement locations the maximum skin-friction drag reduction approached 100% for the BDR experiment and 63% for the PDR experiment.

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Kartushinsky, Alexander I., Efstathios E. Michaelides i Leonid I. Zaichik. "The RANS, PDF and TBL Simulations of Turbulent Gas-Solid Particle Flow in Vertical Pipe". W ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98036.

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The numerical simulation of turbulent gas-solid particle flow in vertical round pipe is performed & analyzed by three different approaches: RANS 2D modeling, PDF approach (Zaichik’s model 2001) & by two-phase TBL (turbulent boundary layer approach). The given performances include all relevant force factors imposed on the motion of solid phase (two-fluid model is considered): particle-turbulence, particle-particle, particle-wall interactions, two-lift the Magnus & Saffman forces and buoyancy (gravitational) force. The dispersed phase is considered as a polydispersed phase composed of finite number of particle fractions and the mass & momentum equations are closed with the help of implementation of original “collision” model (Kartushinsky & Michaelides, 2004). The two/four-way coupling model of Gillandt & Crowe (1998) is accounted for turbulence modulation. The numerical results show that retaining of second diffusion terms in both directions (in streamwise & transverse directions) aligns the average x-velocity components of gas and dispersed phases as well as the particle mass concentration and k-profiles across the flow in case of both PDF and RANS 2D approaches that versus the distributions of parameters obtained by two-phase TBL approach. This is reasonable due to additional effect of fluxes diffusion of the carrier fluid & solid phase in the main direction derived from turbulence fluctuation and inter-particle collision which smoothes the profile shapes.

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Suto, Hitoshi, Yasuo Hattori i Keisuke Nakao. "INTERACTIONS BETWEEN FREE-STREAM TURBULENCE AND TURBULENT BOUNDARY LAYER GENERATED BY PID CONTROL AND LINEAR FORCING". W 5-6th Thermal and Fluids Engineering Conference (TFEC). Connecticut: Begellhouse, 2021. http://dx.doi.org/10.1615/tfec2021.tfl.032374.

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Koukounian, Viken N., i Chris K. Mechefske. "FEM-BEM Modeling and Experimental Verification of the Vibro-Acoustic Behaviour of a Section of Aircraft Fuselage". W ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/detc2016-59163.

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The aerodynamics of an aircraft in flight impose significant stresses upon the structure. Specifically, the mechanics of fluid flow are highly turbulent and, the layer around the aircraft, is referred to the turbulent boundary layer (TBL). The TBL incites a gradient of pressure fluctuations across the fuselage skin resulting in its vibration, and in turn, the generation of noise inside the passenger cabin. The investigation herein proposes a hybrid FEM-BEM modeling technique to predict the aforementioned vibro-acoustic response and an experimental methodology to verify the results (following ASTM and ANSI international testing standards). The described expectations required construction of an acoustic facility consisting of a reverberation chamber and a semi-anechoic room, the development of DAQ software using LabVIEW, an assembly of DAQ hardware using National Instruments products, and the post-processing of test data using Microsoft Excel. The principal quantity of interest is transmission loss (though insertion loss, absorption and other metrics are also calculated). Two panels (0.04in (40thou) and 0.09in (90thou) in thickness) were simulated and tested (0.01in = 1thou). The calculated error of the proposed methodology is within a maximum of 5dB, with an average of 1dB. Ongoing work is investigating complex constructions and the use of damping materials.

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da Rocha, Joana, Afzal Suleman i Fernando Lau. "Prediction of Turbulent Flow-Induced Noise in Aircraft Cabins". W ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39231.

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Flow-induced noise in aircraft cabins can be predicted through analytical models or numerical methods. However, the analytical methods existent nowadays were obtained for simple structures and cabins, in which, usually, a single panel is excited by the turbulent flow, and coupled with an acoustic enclosure. This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). The coupled structural-acoustic analytical model is developed using the contribution of both structural and acoustic natural modes. While, in previous works, only the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is also analyzed. The analytical models were developed for rectangular and cylindrical cabins. The mathematical models were successfully validated through the good agreement with several independent experimental studies. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabins. It is shown that identical panels located at different positions have dissimilar contributions to the cabin interior noise, showing that the position of the vibrating panel is an important variable for the accurate prediction of cabin interior noise. Additionally, the results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. The space-averaged SPL is usually accepted to provide the necessary information for the noise prediction. However, in some real life applications, the local sound pressure may be desirable. To overcome this point, the model is also able to predict local SPL values, at specific locations in the cabin, which are also affected by number of vibrating panels, and often differ from the average SPL values. The developed analytical model can be used to study a wide range of different systems involving a cabin coupled with vibrating panels, excited by the TBL. The properties of the external flow, acoustic cabin, and panels, as well as the number of vibrating panels, can be easily changed to represent different systems. These abilities of the model make it a solid basis for future investigations involving the implementation of noise reduction techniques and multidisciplinary design optimization analyzes.

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Hambric, Stephen A., L. Joel Peltier, John B. Fahnline, David A. Boger i John E. Poremba. "Structural and Acoustic Noise Sources Due to Turbulent Flow Through an Elbow: Formulation of Analysis Methods". W ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41525.

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The low-frequency structure- and fluid-borne noise from elbows excited by fluctuating forces within turbulent fluid flow is investigated. Computational Fluid Dynamics (CFD) Reynolds Averaged Navier Stokes (RANS) analyses of the flow through a piping elbow with a radius to diameter ratio of 2.8 compare favorable to measurements made by previous investigators. The CFD RANS solutions are post-processed to estimate the spectra of the fluctuating wall pressures beneath the turbulent boundary layer (TBL) flow. The CFD RANS solutions are also used to identify regions within the core flow that might excite acoustic modes within the piping fluid. A finite element (FE) model of the piping walls is coupled with a boundary element (BE) model of the interior acoustic fluid and is excited by the fluctuating wall and fluid forces estimated from the CFD RANS solutions. The power transmission through the inlet and discharge ports of the elbow is computed and separated into its structure-borne and fluid-borne components. The influence of both structural and acoustic resonances on the power transmission is evident for both excitation mechanisms. The power transmission curves at the elbow ports may be used as source inputs to transfer matrix models of piping systems that contain elbows.

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Hwang, Y. F. "A Discrete Model of Turbulence Loading Function for Computation of Flow-Induced Vibration and Noise". W ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0534.

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Abstract This paper discusses a discrete representation of the spatially homogeneous and temporally stationary turbulence loading on a structure induced by low speed incompressible flow. In the classical random vibration theory involved with continuous structural systems, this forcing function is expressed as the space-time cross correlation function or its Fourier conjugate, the wavevector-frequency spectrum of the turbulent boundary layer (TBL) wall pressure. These functions cannot be applied directly to finite discrete systems, such as most finite-element structural models, because they contain a fine-scale oscillating component which represents the predominant pressure fluctuations convected with the flow. For example, at mid- and moderate high frequencies, this fluctuating length scale may become smaller than the mesh size of a discrete structure model. An approximated discrete forcing function model to ease this numerical difficulty is presented in this paper. The approximate forcing function model is verified by comparing the numerically calculated modal input force spectra to that obtained from exact analytical solutions. The numerical calculated values approach the exact solutions as the finite-element mesh size becomes smaller.

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Raporty organizacyjne na temat "Turbulent Boundary Layer (TBL)"

Dimotakis, Paul, Patrick Diamond, Freeman Dyson, David Hammer i Jonathan Katz. Turbulent Boundary-Layer Drag Reduction. Fort Belvoir, VA: Defense Technical Information Center, maj 2003. http://dx.doi.org/10.21236/ada416331.

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Lumley, John L. A Study of Turbulent Boundary Layer Structure. Fort Belvoir, VA: Defense Technical Information Center, październik 1986. http://dx.doi.org/10.21236/ada177609.

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Rydalch, Andrew J. Turbulent Boundary Layer Flow over Superhydrophobic Surfaces. Fort Belvoir, VA: Defense Technical Information Center, maj 2013. http://dx.doi.org/10.21236/ada581869.

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Mirels, Harold. Turbulent Boundary Layer Induced by Thermal Precursor. Fort Belvoir, VA: Defense Technical Information Center, czerwiec 1986. http://dx.doi.org/10.21236/ada173715.

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Jodha, Siri, S. Khalsa i Howard P. Hanson. Turbulent Transfer in the Marine Planetary Boundary Layer. Fort Belvoir, VA: Defense Technical Information Center, czerwiec 1994. http://dx.doi.org/10.21236/ada280549.

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Chase, D. M. Turbulent Boundary-Layer Fluctuations at the Solid Interface. Fort Belvoir, VA: Defense Technical Information Center, wrzesień 1992. http://dx.doi.org/10.21236/ada257253.

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Martin, M. P., i A. J. Smits. Understanding and Predicting Shockwave and Turbulent Boundary Layer Interactions. Fort Belvoir, VA: Defense Technical Information Center, listopad 2008. http://dx.doi.org/10.21236/ada504718.

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Goldstein, David B. Computational Modeling of MEMS Microjets for Turbulent Boundary Layer Control. Fort Belvoir, VA: Defense Technical Information Center, grudzień 2004. http://dx.doi.org/10.21236/ada430475.

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Falco, R. E. Sensitivity to Turbulent Boundary Layer Production Mechanisms to Turbulence Control. Fort Belvoir, VA: Defense Technical Information Center, marzec 1991. http://dx.doi.org/10.21236/ada250210.

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Compton, Debora A., i John K. Eaton. Near-Wall Measurements of a Three-Dimensional Turbulent Boundary Layer. Fort Belvoir, VA: Defense Technical Information Center, sierpień 1995. http://dx.doi.org/10.21236/ada344017.

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