Spanwise Correlation Research Articles

Component decomposition and spatial distribution of unsteady forces on a circular cylinder oscillated under various amplitudes at Re = 2.0×104

Vortex-induced vibrations (VIVs) are of practical significance in the design of engineering structures, and the dynamic loads responsible for VIVs are thus crucial. In this study, the force characteristics of a circular cylinder undergoing forced oscillations at vortex lock-in states are investigated by employing three-dimensional large eddy simulations (LES) at a moderate subcritical Reynolds number of 2.0 × 104. Simulations of the oscillating cylinder are performed under a series of normalized amplitudes ranging from 0.05 to 0.60 at a fixed reduced velocity of 6.0. Moreover, a force spectrum-based approach is proposed to decompose the overall force into motion-induced and vortex-shedding components. Alternative insights into the spatial distribution of the force are also obtained by analysing the spanwise correlation, pressure field, and flow feature. The numerical results show that the motion-induced lifts experience an abrupt jump in both magnitude and phase as the oscillation amplitude increases. Furthermore, the motion-induced forces are almost fully correlated except in the phase-jump regime, although the correlation of the overall forces is relatively weak. Finally, the identified force parameters are successfully applied to predict the VIV amplitudes of the cylinder under various mass-damping conditions.

Distribution and spanwise correlation of aerodynamic forces on a 5:1 rectangular cylinder in the vortex-induced vibration stage

Vortex-induced vibration (VIV) is a type of fluid–solid coupling vibration with a complex flow-field structure. Herein, the wall pressures around a 5:1 rectangular cylinder in the stationary and vibration states are studied via wind tunnel tests. By conducting the spectrum analysis, a novel method is proposed to divide the flow-field of the side surface into recirculation, main vortex, and reattachment regions. The method proposed can be used as a reference for partitioning the flow-field. Based on the partition results, the effects of the maximum amplitudes and development VIV stages on the spanwise correlations of the aerodynamic forces in different subregions are investigated. The results show that the correlation coefficients of the aerodynamic forces in all three subregions increase with the value of maximum amplitude, while the correlation coefficients in the stationary state are all the smallest. Additionally, the spanwise correlations are most affected by the maximum amplitude in the recirculation region and least affected in the main vortex region. Moreover, the maximum spanwise correlation coefficients in the three subregions do not appear at the maximum amplitude, but in the VIV rising stage, owing to the interaction between the self-excited force and vortex shedding force.

Effect of Wavy Leading Edges on Airfoil Trailing-Edge Bluntness Noise

Among the several noise-generation mechanisms of airfoil self-noise, trailing-edge bluntness noise is an important noise source, which is caused by the vortex shedding at blunt trailing edges. A numerical study on airfoil trailing-edge bluntness noise control using the bio-inspired wavy leading edges is presented in this paper. The high-fidelity, improved, delayed, detached eddy simulation (IDDES) method was used to calculate the flow field, and the acoustic analogy method was used for noise prediction. For both the blunt-trailing-edge airfoils, a baseline airfoil with a straight leading edge and a bio-inspired airfoil with a wavy leading edge were used in this study. The chord-based Reynolds number was 400,000, and there was no angle of attack. The numerical results show that the trailing-edge bluntness noise of the baseline airfoil was significantly reduced by the wavy leading edges. The sound pressure level reduction was about 3.7 dB at the characteristic frequency, and the maximum sound pressure level reduction was as high as 35 dB. The trailing-edge bluntness noise was decreased at all directional angles. The maximum overall sound pressure level reduction was 6.3 dB at 0°. In addition, by analyzing the pressure fluctuations, wake characteristics, turbulent vortex structures and spanwise correlation and coherence of the flow field, the noise-reduction mechanisms of the bio-inspired airfoil are deeply revealed.

Effects of flexible films on the aerodynamics of a 5:1 rectangular cylinder

The present study demonstrates the aerodynamics of a 5:1 rectangular cylinder with flexible films perpendicularly mounted on its upper surface at both the upstream and downstream ends in wind angle of attack (AOA) up to 20°. Flow and pressure fields around the cylinder are examined by smoke-wire visualizations and pressure measurements in a wind tunnel, respectively. Experimental results show that periodic flapping-induced vortices (FIVs) chiefly caused by the leading-edge flapping film play important roles in the cylinder flow and pressure field properties. The FIVs have a positive effect on the reattachment of the cylinder leading-edge shear layer. For the leading-edge film, the tip of the flapping film would touch down on the cylinder upper surface due to the large amplitude flapping of the film at fD/U∞ ≈ 0.811 (f is the film flapping frequency, D is the model characterized length, and U∞ is the free oncoming flow velocity). Meanwhile, the periodic FIVs dominate the cylinder flow and aerodynamic properties in the range of AoA = [0°, 8°), thus defined as the wall-flapped mode. With an increase in AoA = [8°, 20°], the tip of the flapping leading-edge film would not touch down owing to the small amplitude flapping of the film. Simultaneously, the periodic FIVs have limited effects on the cylinder flow and aerodynamic properties, thus named as the free-flapping mode. Compared to the without flexible films case, the scale of the FIVs is smaller than that of the impinging leading-edge vortices but in a higher frequency, resulting in a quick dissipation of the cylinder impinging shear layer instability, rapid recovery of the pressure on the cylinder upper surface, and reductions in the cylinder drag coefficient, lift coefficient, moment coefficient, and spanwise correlation. For the trailing-edge film, it flaps at fD/U∞ ≈ 0.650 and has a limited effect on the cylinder flow and aerodynamic properties. Finally, the flexible films can significantly mitigate the static stall of the rectangular cylinder, which may stabilize the elongated bluff bodies.

An experimental investigation into the influence of installed passively controlled jet flows on wall-pressure fluctuations

Jet-surface interaction(JSI) represents a significant noise problem in the installation of modern ultra-high bypass ratio turbofan engines. The use of chevron nozzles is known to reduce low-frequency jet mixing noise(JM) by increasing the velocity gradient in the jet shear layer. This effect is expected to influence the jet flow in the vicinity of the wing and to modify the jet-surface interaction noise. To clarify the physics of these two(JSI and JM) noise source mechanisms, an extensive experimental investigation has been conducted in the anechoic chamber of the Doak Laboratory at the University of Southampton. Various measurements were carried out on an isolated subsonic jet and an installed beneath a 2D NACA4415 airfoil using different nozzle shapes and passive vortex generator geometries. The wall-pressure field on the airfoil surface was investigated using a set of wall-pressure transducers flush-mounted in the streamwise and spanwise directions on the pressure side of the airfoil. The unsteady wall-pressure data were analysed in both time and frequency domains to assess changes in: 1) surface trailing edge spanwise correlation length, 2) streamwise convection velocity of the hydrodynamic pressure field, and 3) modification of the hydrodynamic pressure field in the vicinity of the surface trailing edge.

Strategies for identifying the two-dimensional aerodynamic admittance functions of a bridge deck

Pressure measurement experiments were carried out on three streamlined box girders with three geometric ratios of 1:50, 1:75 and 1:100 in five turbulent flow fields generated by grids. The turbulence intensities only affected the root-mean-square (RMS) of the pressure coefficients in the flow separation zone, while the turbulence integral scales affected the RMS of the pressure coefficients over the entire cross-sections. The spanwise correlations of the fluctuating winds and buffeting forces mainly varied with the turbulence integral scales. New strategies are proposed to identify the two-dimensional aerodynamic admittance functions (2D AAFs) using the two-wavenumber approach. The two-wavenumber coherence functions of fluctuating winds or buffeting forces obtained through new strategies do not need to use the empirical spanwise root-coherence function models compared to the traditional strategy. A complete analysis of 2D AAFs based on different strategies was performed. The determined 2D AAF using spanwise root-coherence function models varied with the kinds of spanwise root-coherence function model and relied on spacings chosen to fit, which caused the 2D AAF to vary in size. Therefore, the strategy without any spanwise root-coherence function models is recommended, and it is confirmed to give reliable and repeatable bridge deck 2D AAFs.

Numerical Analysis on Spanwise Correlation of Vortex-Induced Force of Split Double-Box Beam

The vortex-induced force of bridges is not synchronized along the span direction. The spatial correlation of vortex-induced force becomes obvious when the span of the bridge structure gradually increases, and the mass gradually decreases. Therefore, it is important to study the spanwise correlation of vortex-induced forces of long-span bridges to ensure the accuracy of the prediction of vortex-induced vibration response of bridges. The study established and improved the theory and experimental research methods for vortex-induced vibration analysis of large-span bridges by discussing the spanwise correlation during vortex-induced vibration of the split double-box beam. Taking Xihoumen Bridge as the object, two-dimensional (2D) and three-dimensional (3D) numerical models of the scaled-down sections were designed and established based on the ANSYS Fluent platform and the RANS SST turbulence model. Based on the Newmark-β algorithm, a User Defined Function (UDF) was written for vortex vibration calculation, the three-dimensional bypass of the split double-box beam in static conditions and vortex-induced vibration of the split double-box beam of which were calculated, and the spanwise correlations of the aerodynamic coefficients, the surface pressure coefficients, and the wake wind velocity of the main girder section were analyzed for the static and vibration states of the bridge. The results show that the self-excited force of the split double-box beam in vortex-induced vibration improved its spanwise correlation. Compared with those in a static state, the spanwise correlation of the lift coefficient and torque coefficient increased by 55% and 87%, respectively, and the resistance coefficient increased by more than 10 times. The correlation of the pressure coefficients increased by 153%. The correlation of wake wind velocity increased by 37% in the along-wind direction and that in the across-wind and vertical-wind direction increased by more than 10 times. The accuracy of the numerical simulation results was verified by comparing the pressure distribution and pressure spanwise correlation of the main beam with field-measured data.

Airfoil trailing-edge noise and drag reduction at a moderate Reynolds number using wavy geometries

This study utilizes a hybrid aeroacoustic model to investigate how airfoils with spanwise wavy geometries can be used to reduce trailing-edge noise alongside improving the aerodynamic performance. A smooth airfoil is compared to four variants, which have spanwise surface waves of different wavelengths, at a Reynolds number of Re = 64 000 and an angle-of-attack of 1°. The first three variants have a geometry modified by a single wavelength, whereas the fourth has a surface composed of two wavelengths, which creates a more irregular surface variation. The results show that modest noise reductions of around 4 dB are achieved for the first three variants, but a much larger reduction of 17.7 dB is achieved for the fourth variant. The mechanisms behind the noise reduction are explored, and it is shown that the geometry reduces the spanwise correlation of the pressure fluctuations and also modifies the boundary layer dynamics, which contributes to the large reduction. It is further shown that a wavy geometry can reduce the drag force by reducing the shear stress over parts of the airfoil surface and by limiting the flow separation on the suction side. The fourth variant is also assessed across a wider range of angles (0°≤α≤4°) and is shown to produce less noise than the smooth wing across the entire range as well as a drag reduction for α≥1°.

Spanwise correlation and coherent structures of separated flow around rectangular 5:1 cylinder

Spanwise correlation and coherent structure of separated flow around a rectangular cylinder with a side ratio of B/D = 5 (B: breadth; D: depth of cylinder) are numerically investigated by Large Eddy Simulation (LES) at Reynolds number Re = 22,000. The investigation utilizes one series of three-dimensional simulations with various spanwise lengths up to 10D at a grid resolution of D/16 and another series of simulations with various spanwise grid resolutions as small as D/40 at a spanwise length of 5D, in addition to a two-dimensional simulation. The results show that a spanwise coherent flow structure with a wavelength of roughly 1.4D, associated with longitudinal vortices, exists in the separated flow. A spanwise length of 3D seems long enough to eliminate the influence of spanwise coherent flow structure on the global aerodynamic parameters and leads to convergent simulation results. The spanwise correlations of sectional forces and surface pressures decay with the spanwise distance. A finer spanwise resolution results in decreased spanwise correlations in the investigated spanwise resolution region. The results also imply that it is necessary to consider the combined effects of multiple interacting factors such as numerical method, three-dimensional grid discretization and turbulence model when selecting the spanwise resolution.

Experimental exploration of unpowered propellers for vortex-induced vibration suppression of flexible riser

Passive control of the vortex-induced vibrations (VIVs) of flexible risers has been typically studied to alleviate their VIV responses by means of breaking the spanwise correlation, modifying the structural characteristic, or disturbing the flow field. However, this paper proposed using innovative suppression devices—unpowered propellers—to mitigate VIVs and output energy through passive rotation under flowing fluids. The effectiveness of three-, four-, and six-blade propellers for VIV suppression was experimentally examined in the Reynolds number range of 2600–10,400. Seven identical propellers were installed uniformly along a riser facing the incoming flow for VIV suppression. The response parameters of the riser models, including the displacement, frequency, trajectory, and fatigue damage, were investigated. Moreover, a comprehensive evaluation of the unpowered propellers, determined by the suppression efficiency and the cost, was also conducted. The experimental results showed that all three types of propellers significantly decreased the VIV amplitudes and inhibited high-order frequency components. Increasing the number of blades effectively enhanced the amplitude suppression of the propellers, whereas it had almost no effect on the vibration frequencies of the controlled risers. It is worth noting that the three-blade propellers with the best comprehensive evaluation may not be a reasonable choice in high-velocity water.

Full bridge analysis of nonlinear vortex-induced vibration considering incomplete span-wise correlation of vortex-induced force

Responses of vortex-induced vibration (VIV) of long-span bridges are commonly measured at first via wind tunnel tests of sectional model and then converted to the prototype ones of the corresponding full bridges by some approximate formulae. In this paper, a time-domain full bridge analysis method was presented for predicting nonlinear VIV responses mode-by-mode based on a polynomial type of nonlinear mathematical model of vortex-induced force (VIF) on bridge deck cross section. In this method, the motion-dependant self-excited force (SEF) components of VIF were regarded as fully correlated span-wise in the case of smooth flow, while the motion-independent harmonic pure vortex-shedding force (PVSF) component of VIF was regarded as incompletely correlated along the bridge span. To take into account the incomplete span-wise correlation of PVSF, an equivalent generalized PVSF including the effect of the incomplete span-wise correlation of PVSF was defined by using a span-wise correlation coefficient of PVSF which could be obtained through a sectional model wind tunnel test of simultaneous pressure measurement. As an application example, the VIV responses of 12 vertical modes of a steel box deck cable stayed bridge with a main span of 688 m were analysed, and were compared with those converted with two approximate converting formulae, respectively, based on Scanlan’s linear and nonlinear mathematical model of VIF. It is found that the influence of the incomplete span-wise correlation of PVSF on the bridge VIV response is very small and can then be ignored.

LES study on variation of flow pattern around a 4:1 rectangular cylinder and corresponding wind load during VIV

Vortex-induced vibration (VIV) is one of the typical flow-induced large amplitude vibrations. In this study, large eddy simulation (LES) is carried out to investigate the whole VIV process of a rectangular cylinder with aspect ratio 4. The flow fields and wind loads for rigid and elastic models are examined and compared to clarify the crucial flow characteristics during VIV. Results show that the time-averaged reattachment point of separated shear layer moves towards upstream direction with the increase of response amplitude. The mean negative pressure is consequently increased near leading edge of side face. For dynamic flow and wind load, in initial branch, the reattachment point of the separated shear layer, corresponding to the instant of largest side face wind load, gradually moves towards downstream with the increase of response amplitude. Meanwhile, the fluctuating lift coefficient and span-wise wind load correlation increase accordingly. In upper branch, the separated shear layer temporally separates from the side face, which leads to a sharp reduction of fluctuating lift coefficient and span-wise wind load correlation. The response amplitude, however, does not change apparently. In desynchronization, the response amplitude starts to decrease, as the vibration can no longer capture the shedding frequency of shape-induced vortex. The characteristics of the motion-induced wind loads corresponding to different wind speeds are also discussed in this study.

Aerodynamic Forces on a Bluff Cylinder in Sinusoidal Streamwise Winds with Different Angles of Attack

In the present study, multiple-fan active control wind tunnel tests are conducted to investigate the aerodynamic forces on a 5:1 rectangular cylinder in sinusoidal streamwise winds with different angles of attack (AoA). The effects of the frequency, amplitude, and AoA of the sinusoidal flow on the statistical parameters, spectral characteristics, and spanwise distributions of drag, lift, and moment coefficients are analyzed. Results show that each force has two components: the one induced by the approaching velocity oscillation and the one induced by wake vortex-shedding—this is quite different from that in the smooth flows, where the fluctuating forces are totally due to wake vortex-shedding. For each force, changes of the two components and their relationship with the frequency, amplitude, and AoA are presented. The drag fluctuations are generally dominated by the approaching velocity oscillations, whereas the lift and moment are more sensitive to wake vortex-shedding. Therefore, the drag force has better spanwise correlations than the lift and moment forces. Meanwhile, at a non-zero AoA, the inflow amplitude has different effects on the vortex-shedding-induced component as that at a zero AoA. The differences of spanwise distributions between the sinusoidal flow cases and the smooth flow cases are analyzed.

Numerical investigations of the flow-induced vibration of a three-dimensional circular cylinder with various symmetric strips attached

Changes to the surface morphology of a cylinder immersed in a uniform flow may affect the surrounding flow characteristics. Circular cylinders with various symmetric strips attached are ideal models for studying this subject. This study investigates the flow-induced vibration (FIV) of a three-dimensional cylinder with symmetric strips attached using the delayed detached-eddy simulation method. First, the effects of the 22 different types of strip parameters are evaluated on the fixed cylinder. Then, P5-60-20 (location α=60°, coverage β=20°, and thickness h/D=5%) is chosen to explore the transverse FIV. P5-60-20 vibration responses exhibit four distinct branches—initial branch, passive upper branch, transition branch from vortex-induced vibration (VIV) to galloping, and pure galloping—which correspond to the classic initial, upper, lower, and desynchronization regions of the circular cylinder. Through a detailed discussion of each branch, it is discovered that the passive upper branch is significantly different from the upper branch, despite their similar vibration amplitudes and frequencies. The upper branch is induced by the flutter in the presence of intense three-dimensional flow. However, the passive upper branch is caused by symmetric strips, which promote spanwise correlation, prevent lift phase shifting, and dampen the effect of three-dimensional flow. Consequently, at higher reduced velocities, the transition from VIV to galloping and pure galloping is triggered.

The effect of turbulence intensity on the unsteady gust loading on a 5:1 rectangular cylinder

The present work aims to study the effects of turbulence intensity on the three-dimensional spatial distribution of unsteady gust loading on a 5:1 rectangular cylinder. Three types of grids are adopted to produce uniform turbulent flows with different turbulence intensities and constant integral scales. The experimental results show that the turbulence intensity has a noticeable influence on the gust loading. An increase in the turbulence intensity results in a stronger spanwise correlation of the fluctuating pressures on the side surfaces. To reveal the three-dimensional aerodynamic effects of turbulence, a closed-form solution of a three-dimensional aerodynamic admittance function (3D AAF) is presented based on Ribner's three-dimensional spectral tensor theory. This 3D AAF model is expressed in terms of two-dimensional aerodynamic admittance function (2D AAF) for transversely fully correlated gusts and the gust-related spanwise correlation factor. The proposed 3D AAF can explain the mechanism of the three-dimensional aerodynamic effect of turbulence, which results in a more correlated lift force. It is observed that the filtered bandwidth in the spanwise direction amplifies as the turbulence intensity decreases, suggesting that the large-scale vortices in the separated flow are contaminated by smaller eddies. Consequently, the spanwise correlation of the lift force on a 5:1 rectangular cylinder will have the opposite tendency. Notably, it is confirmed that the 2D AAF depends only on the cross-sectional shape rather than the turbulence intensity.

Spanwise-Discontinuous Grooves for Separation Delay and Drag Reduction of Bodies with Vortex Shedding

Suitably shaped grooves, placed transverse to the flow, can delay flow separation over curved surfaces. When grooves are fully extruded in the spanwise direction, they may reduce the drag of boat-tailed bodies with vortex shedding, but with the drawback of increasing the spanwise correlation of the vortex shedding. We investigate herein the effect of spanwise-discontinuous grooves through Large Eddy Simulations. A systematic analysis is carried out on the effect of the number, N, of grooves that are present for N equally long portions of the total spanwise length of the boat-tail. Discontinuous grooves further reduce the drag compared with the full-spanwise-extruded groove. Increasing N produces an improvement of the flow-control-device performance, whose maximum value is reached for N=3, corresponding to a spanwise extension of the groove roughly equal to the body crossflow dimension. Above this value, no further improvements are found. The maximum drag reduction is equal to 25.7% of the drag of the boat-tail without grooves and to 17.7% of the one of the boat-tail with the full-spanwise-extruded groove. The lowest drag value occurs for the least correlated vortex-shedding in the spanwise direction. The reduction in the correlation is mainly related to a flow separation line that is less regular in the spanwise direction.

Spatial correlation of along-wind fluctuating aerodynamic force acting on large aspect-ratio rectangular prisms

This work examines the spatial correlation of the along-wind aerodynamic fluctuating force and its influence on wind-induced responses of high-rise buildings. Seven rectangular rigid models with different side ratios (1/4-4) are made, and simultaneous pressure experiments are conducted under turbulent boundary layer flows. Using the measured data, span-wise correlation coefficients are calculated, and then empirical coherence functions are obtained. In comparing with the traditional coherence models, the main factors affecting the coherence of the along-wind fluctuating aerodynamic force are presented and discussed in this study. A normalized coherence model was proposed, considering factors such as the windward side width, aspect ratio, separation distance from the ground, and low frequency correction. Further, the nondimensional joint acceptance function is presented, based on which the influence of the coherence model on along-wind wind load evaluation and wind-induced response analysis is compared. Finally, for convenience of engineering application, a simplified formula consistent with the revealed coherence properties is recommended.

On the receptivity of low-pressure turbine blades to external disturbances

In the present work, the laminar–turbulent transition of the flow evolving around a low-pressure turbine blade has been investigated. Direct numerical simulations have been carried out for two different free stream turbulence intensity (FSTI) levels to investigate the role of free stream oscillations on the evolution of the blade boundary layer. Emphasis is placed on identifying the mechanisms driving the formation and breakup of coherent structures in the high FSTI case and how these processes are affected by the leading-edge receptivity and/or by the continuous forcing in the blade passage. Proper orthogonal decomposition (POD) has been adopted to provide a clear statistical representation of the shape of the structures. Extended POD projections provided temporal and spanwise correlations that allowed us to identify dominant temporal structures and spanwise wavelengths in the transition process. The extended POD analysis shows that the structures on the pressure side are not related to what happens at the leading edge. The results on the suction side show that the modes defining the leading edge and the passage bases correlate with coherent structures responsible for the transition. The most energetic mode of the passage basis is strongly related to the most amplified wavelength in the boundary layer and breakup events leading to transition. Modes with a smaller spanwise wavelength belong to the band predicted by optimal disturbance theory, they amplify with a smaller gain in the rear suction side, and they show the highest degree of correlation between the passage region and the rear suction side.

Dynamic responses of the rail vehicle-bridge coupling system considering the spanwise correlation functions in vehicle aerodynamic forces

For rail vehicles, the spanwise correlation of aerodynamic forces acting on a single car is usually overlooked. To investigate the effects of spanwise correlation functions on the dynamic responses of the rail vehicle-bridge coupling system, firstly, the forms of spanwise correlation functions in the aerodynamic forces of a running vehicle, which are associated with the longitudinal and vertical fluctuating wind speeds, were proposed. Secondly, the spectra of buffeting forces acting on the running vehicle considering those spanwise correlation functions were obtained. Thirdly, a rail vehicle-bridge coupling system was established by using the commercial software SIMPACK, and a single car running on a typical high-speed railway bridge was taken as an example. Again, the effects of artificial discrete wind fields on the dynamic responses of the vehicle and bridge were investigated. Finally, the effects of the above spanwise correlation functions on the dynamic responses of the rail vehicle-bridge coupling system were compared under the cases of different vehicle speeds and wind speeds. The results show that different discrete time intervals can exert significant effects on the vehicle responses, and the discrete time interval of 0.05 s can be used for analysis in the wind-rail vehicle-bridge coupling system. With the increase of vehicle speed, the values of vehicle and bridge responses considering the spanwise correlation functions tend to be close to those without considering the spanwise correlation functions. However, as the wind speed increases, the values of vehicle and bridge responses generally tend to show greater differences in the presence and absence of spanwise correlation functions. At different vehicle speeds or wind speeds, the spanwise correlation functions have significant effects on the RMSs of vehicle accelerations and bridge lateral acceleration, but they have little effects on the bridge vertical acceleration.

Effects of end condition and aspect ratio on vortex-induced vibration of a 5:1 rectangular cylinder

A series of wind tunnel tests were carried out to study the end condition and aspect ratio effects of a sectional model on the vortex-induced vibration (VIV) of a 5:1 rectangular cylinder. Five aspect ratios varying from 9 to 32 as well as eight endplates with different sizes were examined in the tests. Static and elastically mounted sectional models were employed to measure the surface pressure and VIV response of the cylinder, respectively. Sectional fluctuating lift forces, shedding frequency, as well as their spanwise distribution and correlation on the sectional model were obtained and discussed. Results indicated that the aspect ratio had a significant effect on VIV amplitudes, and small aspect ratios tended to remarkably underestimate the VIV amplitudes. There existed an end interference region with a length of 6–8 D, where the sectional lift forces could be, on average, half the value for the non-interference region. Besides, the aspect ratio was positively related to the spanwise correlation of sectional lift forces. Both end condition and VIV had little effect on the length of the end interference region. In the VIV ‘lock-in’ range, with the increasing reduced wind velocity the fluctuating lift force first increased and reached a maximum value earlier than the VIV amplitude, and after that further increase of reduced wind velocity led to decreased fluctuating lift force (toward a value even smaller than that of the stational model). This complicated variation of sectional lift forces implied that vortex shedding was highly nonlinear and self-limiting. Finally, an empirical method based on the test results was explored to account for the influence of aspect ratio on VIV amplitude.