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Separated flows are complex but interesting to study because they are variable and unsteady. They are present for every bluff bodies and stalled streamlined bodies (at high angle of attack). Experimental aerodynamics is able to study these types of flow, using pressure sensors. Due to sensor size, pressure tubes are used to connect the pressure scanner to the tap (where the pressure is effectively measured). When an unsteady flow is studied, the signal measured by the sensor is perturbed by the tube. The Transfer Function of the tube has to be computed, to correct for the pressure measure using an inverse Fourier Transform and to obtain the pressure effectively present at the tap. The correction is made on the fluctuation amplitudes (around the mean) and the phase of the signal. The synchronization is important when vortex shedding is studied. This Transfer Function is computed by comparing the pressure measured at the begin and at the end of the tube. For that purpose, pressure with a frequency content has been applied on the tube entry (periodic for KTH calibrator and aperiodic for ULg calibrator). The ratio between these pressures gave the desired correction, showing resonance peaks for some frequencies. When a simple tube is used, theoretical models from fluid equations give very similar results to experimental ones. A parallel with electricity has also been made, replacing the pressure tube by an RLC circuit or a transmission line. The longer and the narrower the tube, the higher the signal distortion.

3D printed models are nowadays commonly used in experimental aerodynamics, allowing not only to build complex shaped models easily, but also pressure taps directly on the model and pressure channels into the structure. These more complex measurement systems have also to be experimentally calibrated. Indeed, diameter restriction on tap or shrinks in tube channels highly distorts the signal. We used this calibration to correct the pressure on a stalled wind turbine wing (at high incidence). The stall is linked to viscous effects, the flow becoming separated and turbulent. The fluctuations and phase of pressure taps signal have been studied to understand the Reynolds effect on a stalled wind turbine wing. Experiments were compared with CFD and theoretical models to validate the results.

Another application of unsteady pressure that we have studied the vortex shedding process, occurring around bluff bodies (in particular for rectangular cylinders). The synchronization and amplitude fluctuations of these vortices have been corrected using the dynamic calibration device. Fluid-structure interaction (vortex induced vibration) has then been studied: when vortices were ejected at the resonance frequency of the cylinder, the structure entered auto-excitation and vibrated a lot. When the cylinders were closely spaced in the flow (assembled into a grid), they interfered with each other and the vortex shedding process was changed compared to a single cylinder. To understand deeply this grid, theoretical and numerical models have been used (FEM and CFD) in parallel with experimental sensors: accelerometers (for vibration), pressure sensors connected on taps by tubes, Cobra Probe (velocity in the wake of cylinders), Hot Wire (free stream velocity). The study of this process in function of the incidence and the cylinder spacing allowed us to predict airspeed that induces instability. This is crucial in order to find parameters that minimize vibrations occurring on a real grid, with undesirable noise. In conclusion, this work can be used to take into account unsteady effects when pressure is measured around streamlined and bluff bodies.

Unsteady Flows --- Calibration --- Wind Turbine Wing --- Stall --- Reynolds --- Vortex Induced Vibration --- Rectangular Cylinder --- Grid --- Strouhal --- Fluid-Structure Interaction --- Pressure Measurement --- Wind Tunnel --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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This book is a printed edition of the Special Issue “Energy Harvesters and Self-Powered Sensors for Smart Electronics” that was published in Micromachines, which showcases the rapid development of various energy harvesting technologies and novel devices. In the current 5G and Internet of Things (IoT) era, energy demand for numerous and widely distributed IoT nodes has greatly driven the innovation of various energy harvesting technologies, providing key functionalities as energy harvesters (i.e., sustainable power supplies) and/or self-powered sensors for diverse IoT systems. Accordingly, this book includes one editorial and nine research articles to explore different aspects of energy harvesting technologies such as electromagnetic energy harvesters, piezoelectric energy harvesters, and hybrid energy harvesters. The mechanism design, structural optimization, performance improvement, and a wide range of energy harvesting and self-powered monitoring applications have been involved. This book can serve as a guidance for researchers and students who would like to know more about the device design, optimization, and applications of different energy harvesting technologies.

Information technology industries --- energy harvesting --- vibration --- broadband --- resonant frequency --- piezoelectric vibration energy harvester --- low frequency --- wideband --- modeling --- energy harvester --- temperature threshold --- piezoelectricity --- vibrational cantilever --- bimetallic effect --- piezoelectric --- optimization --- pattern search --- FEM --- PZT --- electromagnetic --- hybrid energy harvester --- power density improvement --- piezoelectric energy harvester --- tandem --- vortex-induced vibration --- flowing water --- vibration energy harvesting --- electromagnetic generator (EMG) --- nonlinear --- magnetic coupling --- high performance --- diamagnetically stabilized levitation --- Taguchi method --- stable levitation --- maximum gap --- electromagnetic energy harvester --- human body kinetic energy --- n/a

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Oceanic internal waves (IWs) at frequencies from local inertial (e.g., near-inertial internal waves) to buoyancy frequencies (nonlinear internal waves or internal solitary waves), sometimes including diurnal and semidiurnal tidal frequencies, play an important role in redistributing heat, momentum, materials, and energy via turbulent mixing. IWs are found ubiquitously in many seas, including East Asian marginal seas (Indonesian Seas, South China Sea, East China Sea, Yellow Sea, and East Sea or Japan Sea), significantly affecting underwater acoustics, coastal and offshore engineering, submarine navigation, biological productivity, and the local and global climate. Despite decades of study on the IWs in some regions, our understanding of the IWs in the East Asian marginal seas is still in a primitive state and the mechanisms underlying every stage (generation, propagation, evolution, and dissipation) of IWs are not always clear. This Special Issue includes papers related to all fields of both low- and high-frequency IW studies in the specified region, including remote sensing, in situ observations, theories, and numerical models.

Technology: general issues --- History of engineering & technology --- near-inertial waves --- typhoon Megi --- South China Sea --- hybrid coordinate ocean model reanalysis results --- Luzon Strait --- baroclinic tides --- stratification variability --- MITgcm --- nonlinear internal wave --- propagating speed --- propagating direction --- underway observation --- moored observation --- East China Sea --- internal solitary wave --- shipboard observation --- extreme current velocity --- wave breaking --- trapped core --- near-inertial internal waves --- nonseasonal variability --- mesoscale flow field --- relative vorticity --- Okubo-Weiss parameter --- subsurface mooring --- southwestern East Sea --- Japan Sea --- internal waves --- Hainan Island --- KRI nanggala-402 submarine wreck --- Lombok Strait --- Bali Sea --- internal solitary waves --- remote sensing images --- underwater noise --- flow noise --- vortex-induced vibration --- the South China Sea --- n/a

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Oceanic internal waves (IWs) at frequencies from local inertial (e.g., near-inertial internal waves) to buoyancy frequencies (nonlinear internal waves or internal solitary waves), sometimes including diurnal and semidiurnal tidal frequencies, play an important role in redistributing heat, momentum, materials, and energy via turbulent mixing. IWs are found ubiquitously in many seas, including East Asian marginal seas (Indonesian Seas, South China Sea, East China Sea, Yellow Sea, and East Sea or Japan Sea), significantly affecting underwater acoustics, coastal and offshore engineering, submarine navigation, biological productivity, and the local and global climate. Despite decades of study on the IWs in some regions, our understanding of the IWs in the East Asian marginal seas is still in a primitive state and the mechanisms underlying every stage (generation, propagation, evolution, and dissipation) of IWs are not always clear. This Special Issue includes papers related to all fields of both low- and high-frequency IW studies in the specified region, including remote sensing, in situ observations, theories, and numerical models.

Technology: general issues --- History of engineering & technology --- near-inertial waves --- typhoon Megi --- South China Sea --- hybrid coordinate ocean model reanalysis results --- Luzon Strait --- baroclinic tides --- stratification variability --- MITgcm --- nonlinear internal wave --- propagating speed --- propagating direction --- underway observation --- moored observation --- East China Sea --- internal solitary wave --- shipboard observation --- extreme current velocity --- wave breaking --- trapped core --- near-inertial internal waves --- nonseasonal variability --- mesoscale flow field --- relative vorticity --- Okubo-Weiss parameter --- subsurface mooring --- southwestern East Sea --- Japan Sea --- internal waves --- Hainan Island --- KRI nanggala-402 submarine wreck --- Lombok Strait --- Bali Sea --- internal solitary waves --- remote sensing images --- underwater noise --- flow noise --- vortex-induced vibration --- the South China Sea --- near-inertial waves --- typhoon Megi --- South China Sea --- hybrid coordinate ocean model reanalysis results --- Luzon Strait --- baroclinic tides --- stratification variability --- MITgcm --- nonlinear internal wave --- propagating speed --- propagating direction --- underway observation --- moored observation --- East China Sea --- internal solitary wave --- shipboard observation --- extreme current velocity --- wave breaking --- trapped core --- near-inertial internal waves --- nonseasonal variability --- mesoscale flow field --- relative vorticity --- Okubo-Weiss parameter --- subsurface mooring --- southwestern East Sea --- Japan Sea --- internal waves --- Hainan Island --- KRI nanggala-402 submarine wreck --- Lombok Strait --- Bali Sea --- internal solitary waves --- remote sensing images --- underwater noise --- flow noise --- vortex-induced vibration --- the South China Sea

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This Special Issue contains 12 papers devoted to fluid/structure interaction (FSI) problems. The main feature of the problems is an interface on which consistent boundary conditions for both the liquid and the solid regions are formulated. The presented studies cover a wide range of problems and methods for their solution, including problems of weak, or one-way interaction, in which the effect of interface deformation on the fluid flow can be neglected, as well as problems of the strong interaction, for which the interface change affects both the flow and the structure behaviour. The interest in FSI problems is very great due to their practical importance. Recent developments in engineering have led to advanced formulations of FSI problems. Some of them could not be formulated several years ago. The presented papers demonstrate progress in both numerical algorithms, mathematical apparatus and advanced computational techniques. In this issue, we have tried to collect different FSI problems, new mathematical and numerical approaches, new numerical techniques and, of course, new results, which can provide an insight into FSI processes.

Technology: general issues --- History of engineering & technology --- vortex-induced vibration --- higher mode --- flexible pipe --- oscillatory flow --- motion trajectory --- lock-in --- dominant frequency --- time-varying --- lifeboat --- freefall --- ship motion --- Kane’s method --- one-way coupling --- CFD-DEM --- ice resistance --- ice crack --- fluid–structure interaction --- flexible beam --- high speed imaging --- system coupling --- coastal structure --- fluid-structure interaction --- engineering design parameters --- environment protection --- intake velocity --- velocity cap --- axial hydraulic force --- stress --- deformation --- pump turbine --- starting-up --- cutting ratio --- codend --- hydrodynamic characteristics --- fluttering motions --- the Fourier series --- marine centrifugal pump --- vibration excitation source --- fluid excitation --- electromagnetic excitation --- numerical simulation --- OpenFOAM --- one-way approach --- structural analysis --- open water test --- computational fluid dynamics --- numerical analysis --- fluid mechanics --- blade design --- propeller --- hydraulic machinery runner --- wet modal analysis --- acoustic–structure coupling --- boundary condition --- marine growth --- hydrodynamic loading --- roughness --- mussels --- morison coefficients --- cavity detachment --- free streamlines --- Brillouin criterion --- n/a --- Kane's method --- acoustic-structure coupling