Large-scale Vortical Motions Research Articles

Investigation on energy conversion instability of pump mode in hydro-pneumatic energy storage system

The pump mode of hydro-pneumatic energy storage (HPES) system often experiences off-design conditions due to the boundary pressure rises, and the resultant energy conversion instability has an adverse effect on the system operation. However, the evolutionary process of this instability and the corresponding flow events are still not fully understood. Experimental and numerical simulation studies of a centrifugal pump with vaned diffuser were conducted in a wide operating range, and the following notable results were obtained. The energy conversion of pump mode shows three typical stages as the pump head increases, stable work→stumbled work→shaky work, corresponding to the inner flow pattern development of stall-free→stall inception→stall deepening. In this evolutionary process, the attenuation of rotor blade loading gradually spreads from the inlet shroud side to the entire blade. This strengthens the natural adverse potential rothalpy gradient and induces the energetic vortical structures including leading backflow vortices, dynamic stall cells and trailing helical vortices. A strong coupling between large-scale vortical motions and energy conversion is observed and this yields a Logistic growth of the shaft power and pump head fluctuations. The critical condition for the energy conversion instability is the diagnostic function SI = 1, and this is recommended for determining the stability limit of the pump mode.

A Coherent vorticity preserving eddy-viscosity correction for Large-Eddy Simulation

This paper introduces a new approach to Large-Eddy Simulation (LES) where subgrid-scale (SGS) dissipation is applied proportionally to the degree of local spectral broadening, hence mitigated or deactivated in regions dominated by large-scale and/or laminar vortical motion. The proposed coherent-vorticity preserving (CvP) LES methodology is based on the evaluation of the ratio of the test-filtered to resolved (or grid-filtered) enstrophy, σ. Values of σ close to 1 indicate low sub-test-filter turbulent activity, justifying local deactivation of the SGS dissipation. The intensity of the SGS dissipation is progressively increased for σ<1 which corresponds to a small-scale spectral broadening. The SGS dissipation is then fully activated in developed turbulence characterized by σ≤σeq, where the value σeq is derived assuming a Kolmogorov spectrum. The proposed approach can be applied to any eddy-viscosity model, is algorithmically simple and computationally inexpensive. LES of Taylor–Green vortex breakdown demonstrates that the CvP methodology improves the performance of traditional, non-dynamic dissipative SGS models, capturing the peak of total turbulent kinetic energy dissipation during transition. Similar accuracy is obtained by adopting Germano's dynamic procedure albeit at more than twice the computational overhead. A CvP-LES of a pair of unstable periodic helical vortices is shown to predict accurately the experimentally observed growth rate using coarse resolutions. The ability of the CvP methodology to dynamically sort the coherent, large-scale motion from the smaller, broadband scales during transition is demonstrated via flow visualizations. LES of compressible channel are carried out and show a good match with a reference DNS.

Spectral radiation intensities of a turbulent buoyant ethylene flame: CFD-aided tomographic inversion

Radiation heat transfer has been found to dominate fire spread in large-scale fires. The radiation heat loss of buoyant turbulent fires is coupled with fluid mechanics, combustion processes, and soot/gas concentrations. Deconvolution of these combined phenomena can facilitate the development of combustion and radiation models for use in predictive fire modeling. Therefore, in this work, line-of-sight spectral radiation intensities have been measured from a buoyant turbulent pool-fire-like ethylene diffusion flame. In an attempt to be representative of practical turbulent fires, a burner of 15.2cm in diameter was used. Temporal measurements of radiation intensity were obtained with a fast (400Hz) mid-infrared spectrometer at a horizontal plane located at half a burner diameter above the burner. Measurement statistics, including mean, root mean square (RMS), probability density function (PDF) of line of sight intensity, and intermittency are reported herein for wavelengths dominated by soot and CO2 radiation. The data show that radiation is affected by large-scale vortical motions, resulting in varying flame intermittency in the radial direction. Radial distributions of local scalar properties (temperature and soot volume fraction) were calculated through tomographic inversion, using measured data at multiple soot radiation wavelengths. The inversion technique was coupled with the results of a computational fluid dynamics (CFD) fire simulation code. CFD results were used to construct PDFs and spatial correlations for the scalars of interest. The estimated scalars are shown to be consistent with values from the literature, and mean and RMS radiation intensities computed from these scalars are in good agreement with measurements.

Simulation of magnetohydrodynamic effects during large-scale vortices generation in a liquid-metal coolant

This investigation is aimed at establishing the interrelation between the generation of a large-scale vortical motion and magnetohydrodynamic (MHD) effects in liquid-metal nuclear power plant coolants. The subjects of the study are three-dimensional liquid sodium flows in the presence of an external transverse magnetic field in bent and in rectilinear cylindrical channels with obstacles inside of them with different geometries that generate a large-scale vortical motion. To establish the governing dimensionless criteria and their influence on the distribution of the velocity and the magnetic fields, analytical solutions of the Hartmann problem were found to a 2D approximation. A numerical 3D simulation identified the regions of the most intensive induced magnetic field for the 3D Hartmann flow under consideration. The spatial distributions of the fields of the velocities, the vorticity, and the magnetic induction are obtained considering the position of the flow disturbance source. A correlation is found between the vortex formation effects in channels with a complex geometry and the fluctuations of the magnetic field induced in the area where the vortical structures are localized on imposition of a static magnetic field.

Short- and long-term dynamic modes of turbulent swirling premixed flame in a cuboid combustor

Direct numerical simulation (DNS) of hydrogen–air turbulent swirling premixed flame in a cuboid combustor is conducted to investigate thermoacoustic instability and dynamic modes of turbulent swirling premixed flame in combustors. A detailed kinetic mechanism and temperature dependency of physical properties are considered in DNS. Two swirl number cases of 0.6 and 1.2 are investigated. Large-scale helical vortical structures are generated near the inlet of combustion chamber, and a lot of fine-scale vortices emerge downstream. Flame structure is engulfed by the vortical structures and depends largely on the swirl number. Spectral analysis of pressure oscillation on walls shows that quarter-wave mode of longitudinal acoustics has the largest energy, and that characteristic oscillations are found at higher frequencies. To investigate oscillation modes of pressure and heat release rate fields, dynamic mode decomposition (DMD) is applied to DNS results. It is shown that there are differences between dominant frequencies in spectral analysis of time-series pressure data at one point of walls and DMD of time-series pressure field data. DMD of pressure field reveals that the quarter-wave mode in longitudinal acoustics has the largest energy for the case of S=0.6. Furthermore, it is clarified that the transverse acoustic plane waves and pressure oscillations induced by large-scale vortical motions play important roles for the pressure oscillations in combustors. DMD of heat release rate field reveals that the DMD modes of pressure with high amplitude do not necessarily have coupling with fluctuations of heat release rate. Interactions between dynamic modes of pressure and heat release rate are also discussed.

Computational Study of High-Lift Low-Pressure Turbine Cascade Aerodynamics at Low Reynolds Number

This study uses a Reynolds-averaged Navier–Stokes finite volume flow solver to simulate the flowfields around a two-dimensional linear turbine cascade model at a Reynolds number of 25,000. Three blade profiles have been simulated, including the aft-loaded Pack B, which has a nominal Zweifel loading coefficient equal to 1.15, the midloaded L1M (), and the front-loaded L2F (). All three blade profiles are known to be susceptible to varying degrees of laminar flow separation along the suction surface. Turbulence models used, which to the authors’ knowledge have been applied for the first time here, are the Abe–Kondoh–Nagano linear low- as well as the Kato–Launder modification. Time-accurate simulations, including fully laminar computations, are compared with experimental data and higher-order computations to judge the accuracy of the results, where it is shown that Reynolds-averaged Navier–Stokes simulations with appropriate turbulence modeling can produce both quantitatively and qualitatively similar separation behavior as seen in experiments. However, large-scale vortical motions predicted by the turbulence models and laminar solver advect downstream and instigate flow reattachment, a result the authors believe would be attenuated to some degree by three-dimensional vortex breakdown. Results collectively show that characterization of transition to turbulence as judged by analysis of the Reynolds shear stress is not sufficient in two dimensions, and further analysis including spectral methods may be necessary to better predict transition at low Reynolds number.

Cross-helicity effects and turbulent transport in magnetohydrodynamic flow

In the presence of large-scale vortical motions and/or magnetic-field strains, the turbulent cross helicity (velocity–magnetic-field correlation in fluctuations) may contribute to the turbulent electromotive force and the Reynolds stress. These effects of cross helicity are considered to balance the primary effects of turbulence such as the turbulent magnetic diffusivity in magnetic-field evolution and the eddy viscosity in the momentum transport. The cross-helicity effects may suppress the enhanced transports due to turbulence. Physical interpretation of the effects is presented with special emphasis on the difference between the cross-helicity effect and the usual a or helicity effect in the dynamo action. The relative importance of the cross-helicity effect in dynamo action is validated with the aid of a direct numerical simulation (DNS) of the Kolmogorov flow with an imposed magnetic field. Several mechanisms that provide turbulence with the cross helicity are also discussed.

축대칭 초음속 제트에서 스크리치 모드 전이현상의 수치적 연구

Mode transition of the axi-symmetric screech tone in the low supersonic Mach number range from 1.0 to 1.20 is numerically analyzed. The axi-symmetric Navier-Stokes equations and the k-e turbulence model are solved in the cylindrical coordinate system. The dispersion-relation-preserving(DRP) scheme is applied for space discretization and the optimized four levels marching method are used for time integration. At low supersonic Mach numbers with an axi-symmetric A1 mode in the simulation, it is shown that acoustic propagation due to the nonlinear effects is seen in the lateral direction and the screech tone frequency is the same as the vortex passing frequency due to the generation of intense large-scale vortical motions.

Cavitation, primary break-up and flash boiling of gasoline, iso-octane and n-pentane with a real-size optical direct-injection nozzle

Improvements to the direct-injection spark-ignition combustion system are necessary if the potential reductions in fuel consumption and emissions are to be fully realized in the near future. One critical link in the optimization process is the design and performance of the injectors used for fuel atomization. Multi-hole injectors have become the state-of-the-art choice for gasoline direct-injection engines due to their flexibility in fuel targeting by selection of the number and angle of the nozzle holes, as well as due to their demonstrated stability of performance under a wide range of operating conditions. Recently there has been increased attention devoted to the study of the flow through the internal passages of injectors because of the presence of particular fluid phenomena, such as large-scale vortical motion and cavitation patterns, which have been shown to influence the characteristics of primary break-up. Understanding how cavitation can be used to improve spray atomisation is essential for optimizing mixture preparation quality under early injection and stratified engine operating conditions but currently no data exist for injector-body temperatures representative of real engine operation, particularly at low-load conditions that can also lead to phase change due to fuel flash boiling. This paper outlines results from an experimental imaging investigation into the effects of fuel properties, temperature and pressure conditions on the extent of cavitation, flash boiling and, subsequently, primary break-up. This was achieved by the use of a real-size transparent nozzle of a gasoline injector from a modern direct-injection combustion system. Gasoline, iso-octane and n-pentane fuels were used at 20 and 90 °C injector-body temperatures for ambient pressures of 0.5 and 1.0 bar in order to simulate early homogeneous injection strategies for part-load and wide-open-throttle engine operation.

Large-Scale Vortical Motion and Pressure Fluctuation in Noise-Controlled, Swirl-Stabilized Combustor

To clarify the mechanisms of combustion oscillation, combustion noise and their suppression by secondary fuel injection, simultaneous measurements of stereoscopic particle image velocimetry (SPIV) and pressure fluctuation in combustion chamber were conducted on several planes of a swirl-stabilized turbulent premixed flame for no control case and noise-controlled case by continuous secondary fuel injection. Velocities measured by SPIV were averaged in 8 phases of the pressure fluctuation and streamlines were obtained from the phase-averaged velocities. For no control case, large-scale vortical structures are generated in regions around the axial centerline of the combustor and outer edge of the swirl nozzle in the phase of low pressure. With increasing pressure, they move near the contour surface of mean progress variable c = 0.5 which have been obtained in the previous study. These large-scale vortical motions induce fluctuation of flame front and enhance entropy term in the acoustic sound source. The secondary fuel injection suppresses the velocity fluctuation in the inner recirculation zone, resulting in reduction of combustion noise. These results show that control of the large-scale vortical motion is important for reduction of combustion noise.

Lorentz Force: A Possible Driving Force for Sunspot Rotation

Zhao and Kosovichev (Astrophys. J. 591, 446, 2003) found two opposite sub-photospheric vortical flows in the depth range of 0-12 Mm around a fast rotating sunspot. So far there is no theoretical model explaining such flow motions. In this paper, we try to explain this phenomenon from the point of view of magnetic flux tubes interacting with large-scale vortical motions of plasma. In the deeper zone under the photosphere, the magnetic force may be less than the nonmagnetic force of plasma. The vortical flow located there twists the flux tube and magnetic free energy is built up in the tube. In the shallower zone under the photosphere, the magnetic force may be greater than the nonmagnetic force. Thus, part of the stored magnetic free energy is released to drive the plasma to rotate in two opposite directions, e.g., in the depth ranges of 0-3(5) and 9-12 Mm. In addition, we also define a vector of nonpotential magnetic stress tau, which can be related to flare occurrence. It is calculated for the active region NOAA 10930 on 11 December 2006. We find that: i) the integral of its line-of-sight (LOS) stress successively increases around the magnetic neutral line (MNL) prior to and during the flare and decreases to a minimum after the flare; ii) the integral of its transverse stress exceeds the integral of its LOS component by one order of magnitude over the whole field of view; iii) the transverse stress first points toward the MNL, then along it, and finally it points away from it. We need other data to verify whether or not the magnetic energy is transported in the horizontal direction to the neutral line, and then partly changes into the energy in LOS direction before and during the flare.

Measurements of Aeroacoustic Noise and Pressure Fluctuation Generated by a Door-Mirror Model Placed on a Flat Plate

To provide reliable validation data for computational aeroacoustics methods that predict bluff-body sound, the far-field sound pressure and fluctuating surface pressure were measured in detail for a simplified mock-up model of an automobile door mirror (a quarter-section sphere mounted on a half-circular cylinder placed on a flat plate). The surface flow on the model was visualized using an oil flow method. The Reynolds number based on the upstream uniform wind velocity and the diameter of the half-circular cylinder was varied from 1.4×105 to 2.4×105 for model yaw angles of 0 and 15 degrees. The pressure fluctuations on the model surface and flat plate indicated the existence of large-scale vortical motion with a non-dimensional frequency, calculated on the basis of the model width and the free-stream velocity, of 0.16. The frequency spectra of the sound pressure fluctuations had a weak peak apparently due to the large-scale vortical motion. However, unlike the flow around a two-dimensional circular cylinder, the peak was not intense enough to alter the overall level of the sound radiated from the model. When the model was rotated 15 degrees, the power spectra of the sound pressure increased in the non-dimensional frequency range between 1 and 2.

Variational asymptotics for rotating shallow water near geostrophy: a transformational approach

We introduce a unified variational framework in which the classical balance models for nearly geostrophic shallow water as well as several new models can be derived. Our approach is based on consistently truncating an asymptotic expansion of a near identity transformation of the rotating shallow water Lagrangian. Model reduction is achieved by imposing either degeneracy (for models in a semigeostrophic scaling) or incompressibility (for models in a quasigeostrophic scaling) with respect to the new coordinates. At first order, we recover the classical semigeostrophic and quasigeostrophic equations, Salmon’s L1 and large-scale semigeostrophic equations, as well as a one-parameter family of models that interpolate between the two. We identify one member of this family, dierent from previously known models, that promises better regularity—hence consistency with large-scale vortical motion—than all other first order models. Moreover, we explicitly derive second order models for all cases considered. While these second order models involve nonlinear potential vorticity inversion and do not obviously share the good properties or their first order counterparts, we oer an explicit survey of second order models and point out several avenues for exploration.

RV instantaneous intraventricular diastolic pressure and velocity distributions in normal and volume overload awake dog disease models.

Intraventricular diastolic right ventricular (RV) flow field dynamics were studied by functional imaging using three-dimensional (3D) real-time echocardiography with sonomicrometry and computational fluid dynamics in seven awake dogs at control with normal wall motion (NWM) and RV volume overload with diastolic paradoxical septal motion. Burgeoning flow cross section between inflow anulus and chamber walls induces a convective pressure rise, which represents a "convective deceleration load" (CDL). High spatiotemporal resolution dynamic pressure and velocity distributions of the intraventricular RV flow field revealed time-dependent, subtle interactions between intraventricular local acceleration and convective pressure gradients. During the E-wave upstroke, the total pressure gradient along intraventricular flow is the algebraic sum of a pressure decrease contributed by local acceleration and a pressure rise contributed by a convective deceleration that partially counterbalances the local acceleration gradient. This underlies the smallness of early diastolic intraventricular gradients. At peak volumetric inflow, local acceleration vanishes and the total adverse intraventricular gradient is convective. During the E-wave downstroke, the strongly adverse gradient embodies the streamwise pressure augmentations from both local and convective decelerations. It induces flow separation and large-scale vortical motions, stronger in NWM. Their dynamic corollaries on intraventricular pressure and velocity distributions were ascertained. In the NWM pattern, the strong ring-like vortex surrounding the central core encroaches on the area available for flow toward the apex. This results in higher linear velocities later in the downstroke of the E wave than at peak inflow rate. The augmentation of CDL by ventriculoannular disproportion may contribute to E wave and E-to-A ratio depression with chamber dilatation.

Diastolic right ventricular filling vortex in normal and volume overload states.

Functional imaging computational fluid dynamics simulations of right ventricular (RV) inflow fields were obtained by comprehensive software using individual animal-specific dynamic imaging data input from three-dimensional (3-D) real-time echocardiography (RT3D) on a CRAY T-90 supercomputer. Chronically instrumented, lightly sedated awake dogs (n = 7) with normal wall motion (NWM) at control and normal or diastolic paradoxical septal motion (PSM) during RV volume overload were investigated. Up to the E-wave peak, instantaneous inflow streamlines extended from the tricuspid orifice to the RV endocardial surface in an expanding fanlike pattern. During the descending limb of the E-wave, large-scale (macroscopic or global) vortical motions ensued within the filling RV chamber. Both at control and during RV volume overload (with or without PSM), blood streams rolled up from regions near the walls toward the base. The extent and strength of the ring vortex surrounding the main stream were reduced with chamber dilatation. A hypothesis is proposed for a facilitatory role of the diastolic vortex for ventricular filling. The filling vortex supports filling by shunting inflow kinetic energy, which would otherwise contribute to an inflow-impeding convective pressure rise between inflow orifice and the large endocardial surface of the expanding chamber, into the rotational kinetic energy of the vortical motion that is destined to be dissipated as heat. The basic information presented should improve application and interpretation of noninvasive (Doppler color flow mapping, velocity-encoded cine magnetic resonance imaging, etc.) diastolic diagnostic studies and lead to improved understanding and recognition of subtle, flow-associated abnormalities in ventricular dilatation and remodeling.

Magnetic twist and writhe of active regions

We study the long term evolution of a set of 22 bipolar active regions (ARs) in which the main photospheric polarities are seen to rotate one around the other during several solar rotations. We first show that differential rotation is not at the origin of this large change in the tilt angle. A possible origin of this distortion is the nonlinear development of a kink-instability at the base of the convective zone; this would imply the formation of a non-planar flux tube which, while emerging across the photosphere, would show a rotation of its photospheric polarities as observed. A characteristic of the flux tubes deformed by this mechanism is that their magnetic twist and writhe should have the same sign. From the observed evolution of the tilt of the bipoles, we derive the sign of the writhe of the flux tube forming each AR; while we compute the sign of the twist from transverse field measurements. Comparing the handedness of the magnetic twist and writhe, we find that the presence of kink-unstable flux tubes is coherent with no more than 35\% of the 20 cases for which the sign of the twist can be unambiguously determined. Since at most only a fraction of the tilt evolution can be explained by this process, we discuss the role that other mechanisms may play in the inferred deformation. We find that 36\% of the 22 cases may result from the action of the Coriolis force as the flux tube travels through the convection zone. Furthermore, because several bipoles overpass in their rotation the mean toroidal (East-West) direction or rotate away from it, we propose that a possible explanation for the deformation of all these flux tubes may lie in the interaction with large-scale vortical motions of the plasma in the convection zone, including also photospheric or shallow sub-photospheric large scale flows.

A WIND TUNNEL INVESTIGATION OF THE INFLUENCE OF SOLAR-INDUCED WALL-HEATING ON THE FLOW REGIME WITHIN A SIMULATED URBAN STREET CANYON

A wind tunnel study has been undertaken to assess theinfluence of solar-induced wall heating on the airflowpattern within a street canyon under low-speed windconditions. This flow is normally dominated by large-scalevortical motion, such that the wind moves downwards at thedownstream wall. In the present work the aim has been toexamine whether the buoyancy forces generated at this wallby solar-induced heating are of sufficient strength tooppose the downward inertial forces and, thereby, changethe canyon flow pattern. Such changes will also influencethe dispersion of pollutants within the street. In theexperiments the windward-facing wall of a canyon has beenuniformly heated to simulate the effect of solar radiation.Four different test cases, representing different degreesof buoyancy (defined by a test Froude number, Fr), havebeen examined using a simple, 2-D, square-section canyonmodel in a wind tunnel. For reference purposes, the neutralcase (no wall heating), has also been studied. The approachflow boundary layer conditions have been well defined, withthe wind normal to the main canyon axis, and measurementshave been taken of canyon wall and air temperatures andprofiles of mean velocities and turbulence intensities.Analysis of the results shows clear differences in the flowpatterns. As Fr decreases from the neutral case there arereductions of up to 50% in the magnitudes of the reverseflow velocities near the ground and in the upward motionnear the upstream wall. A marked transition occurs at Fr ≈ 1, where the single dominant vortex, existing at higher Fr values, weakens and moves upwards whilst a lower region of relatively stagnant flow appears. This transition hadpreviously been observed in numerical model predictions butat a Fr at least an order of magnitude higher.

Model of vortex tubes in the low-latitude plasma sheet of the earth magnetosphere

Theoretical model is proposed to explain specific features of compressional waves of the Pc 4–5 frequency range which were observed with the INTERBALL-1 probe in the middle tail of the Earth magnetosphere. The waves exhibit anti-phase disturbances in thermal plasma and magnetic field pressures. Large-scale vortical plasma motions are associated with the waves. Coupling of the drift Alfven and magnetosonic waves is considered with inclusion of finite plasma compressibility and disturbances along the local magnetic field line. In limiting cases derived equations are reduced to well-known Kadomtsev-Pogutse and Hasegawa-Mima equations. Partial solutions take form of vortices. According to proposed model, two-dimensional vortical motion of a plasma transversely to the local field line is accompanied by nonlinear magnetosonic waves propagating in flux tubes almost along the field lines.

JUNCTION FLOWS

▪ Abstract Junction flows occur when a boundary layer encounters an obstacle attached to the same surface. Physical phenomena that have been observed for blunt and streamlined obstacles are discussed for both laminar and turbulent approaching boundary layers. The pressure gradients around an obstacle produce a three-dimensional separation with horseshoe vortices that wrap around the obstacle. Except for very low Reynolds number laminar flows, these vortices are highly unsteady and are responsible for high turbulence intensities, high surface pressure fluctuations and heat transfer rates, and erosion scour in the nose region of the obstacle. Calculation methods are also reviewed; methods that capture the large-scale chaotic vortical motions should be used for computations. Some work on the control, modification, or elimination of such vortices is also reviewed.

Free vibrations of an elastic cylinder in a cross flow and their effects on the near wake

Fluid-structure interactions resulting from the free vibrations of a two-dimensional elastic cylinder in a cross flow are not well understood. Experimental data pertaining to the interaction behavior is rather scarce, especially that related to the phenomenon of synchronization where the vortex shedding frequency is approximately equal to the natural frequency of the fluid-structure system. The present investigation attempts to examine this problem experimentally using a laser vibrometer to assess the bending displacements and a laser Doppler anemometer to measure the velocities in the wake. Experiments were carried out over a range of reduced velocities. The reduced velocity was first varied by using cylinders of different materials and then by changing the free stream velocity, while maintaining the cylinder diameter constant. A proper choice of materials and reduced velocity allowed the synchronization phenomenon to be investigated. For the range of reduced velocity investigated, the vibration amplitude of the cylinder is finite, even at synchronization, and increases with reduced velocity. The results further show that more than one mode of vibration is excited away from synchronization; however, only the first mode is evident at synchronization. In addition, the near-wake flow behind the elastic cylinder, at three different Reynolds numbers in the sub-critical range, was measured in detail and the data was used to analyse the vibration effects on the mean and turbulence field compared to those measured behind a relatively rigid cylinder at the same Reynolds numbers. It is found that cylinder vibrations have little or no effect on the mean drag and the normalized mean field. However, cylinder vibrations enhance turbulent mixing, thus resulting in a substantial increase in the turbulent intensities. This implies that the large-scale vortical motion is also affected. Nevertheless, turbulence structure in the inertial sub-range is not affected by cylinder vibrations. The slopes of the velocity spectra in this range is still measured to be −5/3 for the freely vibrating cylinders investigated.