Rigid Splitter Plate Research Articles

Effect of length and attack angle of the splitter plates on circular cylinder piezoelectric water energy harvester

With the micro-miniaturization of offshore wireless sensors, signal lights, and other devices and the emergence of the problem of self-powering in the distant sea, how to harvest energy from low-speed currents has become a hot spot of research nowadays. To improve the energy output power and conversion efficiency of low-speed water flow, we propose a vertical cantilever beam circular cylinders fitted with a rigid splitter plate piezoelectric energy harvester (CSPPEH). In this paper, the influence of the length and the attack angle of the splitter plate on CSPPEH has been experimentally investigated. The vibration response mechanism involving the mutual transition between vortex-induced vibration and galloping was analyzed through particle image velocimetry flow field visualization. The experimental results indicate that the vibration and piezoelectric characteristics of the CSPPEH increase initially and then decrease with the length of the splitter plates (L/D = 0–2.4) at the attack angle of 0°, which can be explained by the theoretical model of the energy harvester. It is found that the optimal vibration and piezoelectric characteristics occur at a rigid splitter plate length of 1.40D with an attack angle of 90°. The maximum values for amplitude, vibration swing angle, voltage, power, and power density are 4.96D, 21.7°, 42.68 V, 910.81 μW, and 1.94 mW/cm3, respectively. Efficiency was up to 2.2% at 0.4D length and 90° attack angle of the splitter plate. Compared to the bare circular cylinder energy harvester, the output power and efficiency are significantly improved. The demonstration of continuous charging and discharging of capacitors and light emitting diode lights is performed to show the practicability of the designed CSPPEH. Overall, the present study enables the applications of CSPPEH for realizing self-powered wireless sensing and signal lights under low-water-speed environments.

Flow control using hot splitter plates in the wake of a circular cylinder: A hybrid strategy

A novel and effective hybrid technique, which involves active surface heating strategies in conjunction with the use of passive splitter plates in the wake of the cylinder, is proposed. In this report, we present the results of a numerical investigation on the two-dimensional, laminar mixed convection flow over a circular cylinder with a hot rigid splitter plate attached to it on the wake side. A projection algorithm-based finite volume method is employed to obtain the solution of the coupled, nonlinear governing partial differential equations subjected to Courant–Friedrichs–Lewy conditions. The isothermal heating of the splitter plate under the influence of the gravity field generates an upward buoyancy force in the wake of the cylinder. For different length-to-diameter (L/D) ratios, the effect of heating on aerodynamic, wake, and heat transfer characteristics has been studied for a wide range of parameters; 75 ≤Re≤ 150, 0 ≤Ri≤ 1, and 0.5 ≤L/D≤ 1 at Pr = 0.7. It is observed that the hot splitter plate would bring about conspicuous changes such as asymmetry in the vortex shedding behind the cylinder at low Reynolds numbers. The outcomes demonstrate a notable improvement in convective heat transfer and drag, with gains of up to 7% and 15%, respectively. It is found that the rate of heat transfer and vortex shedding frequency decrease with an increase in L/D ratio. Correlations for the estimation of Strouhal number and Nusselt number have also been proposed which helps provide a more thorough understanding of thermal and aerodynamic features of the hybrid approach.

The Effect of the Layout of a Rigid Splitter Plate on the Flow-Induced Vibration of a Downstream Cylinder Subjected to Wake Flow

In this study, the effect of additional positions of rigid splitter plates on the response characteristics of tandem cylinders at a Reynolds number of 150 and a fixed distance ratio of 5.0 was numerically investigated via the computational fluid dynamics (CFD) method. Four layouts for the cylinder–plate body, including a downstream cylinder (DC), a downstream cylinder–plate body with a wake side plate (DCP), a downstream plate–cylinder body with an incoming flow side plate (DPC), and a downstream plate–cylinder–plate body with a double-sided plate (DPCP), are considered. The results show that the splitter plate attached to the incoming flow side or the wake side can suppress the vibration of the downstream cylinder in a specific reduced velocity range (4.0 < Ur ≤ 10.0). Compared with the DC, the maximum response amplitude of the DPC and DCP in the lock-in region is reduced by 30.8% and 47.4%, and the lock-in bandwidth is also significantly narrower. The layer separation point of the upstream cylinder moves downstream upon adding splitter plates to both the incoming flow and wake sides, and the resulting splitter shear layer of the DPCP is completely parallel to the free flow, while the maximum response amplitude is reduced by 93.6%, which realizes the best effect of stream-induced vibration suppression.

Flow over a circular cylinder with a flexible splitter plate

In the present work, we study the flow field around, and forces acting on, a circular cylinder with an attached flexible splitter plate/flap. Two cases of flap length ( $L/D$ ), namely, $L/D = 5$ and $L/D = 2$ have been investigated focusing on the effect of variations in flap flexural rigidity, $EI$ . We find that for a range of $EI$ and Reynolds numbers $Re = UD/\nu$ , a non-dimensional bending stiffness $K^{\ast }=EI/((1/2)\rho U^2 L^3)$ collapses flap motion and forces on the system well, as long as $Re>5000$ . In the $L/D = 5$ flap case, two periodic flap deformation regimes in the form of travelling waves are identified (modes I and II), with mode I occurring at $K^{\ast } \approx 1.5\times 10^{-3}$ and mode II at lower $K^{\ast }$ values ( $K^{\ast }<3\times 10^{-5}$ ). In the $L/D = 2$ flap case, we find a richer set of flapping modes (modes A, B, C and D) that are differentiated by their flapping characteristics (symmetric/asymmetric and amplitude). Force measurements show that the largest drag reduction occurs in mode I ( $L/D = 5$ ) and mode C ( $L/D = 2$ ), which also correspond to the lowest lift and wake fluctuations, with the mode C wake fluctuations being lower than even the rigid splitter plate case. In contrast, the highest fluctuating lift, in both $L/D$ cases, occurs at higher $K^{\ast }$ , when the wake frequency is close to the first structural bending mode frequency of the flap. The observed rich range of flap/splitter plate dynamics could be useful for applications such as drag reduction, vibration suppression, reduction of wake fluctuations and energy harvesting.

Numerical Study of Circular-Cylinder Disturbance Generators with Rigid Splitter Plates

This paper describes the numerical study of oscillating circular cylinders with rigid splitter plates of different lengths. These geometries may be used as disturbance generators for the study of unsteady airfoils and wings operating in highly vortical flowfields. It has been shown that cylinders undergoing forced rotational oscillations at their natural shedding frequency can produce wakes with minimal deviation in cycle-to-cycle vortex strength and position. Adding a splitter plate allows these deviations to be reduced even further. We present cases for oscillating cylinders having splitter-plate lengths up to at a Reynolds number of 7600. Frequencies are maintained at the natural shedding frequency, and a rotational amplitude of 45 deg is used. Numerical simulations are performed using a two-dimensional unsteady Reynolds-averaged Navier–Stokes (RANS) code. Results are presented in the form of vorticity contours and cycle-averaged velocity profiles, as well as the dominant frequencies of cylinder lift force and downstream velocity angles. The results show that splitter-plate lengths shorter than adversely affect the ability to generate a coherent vortex wake due to shear layer roll-up near the trailing edge of the plate. Splitter plates longer than produced a reverse von Kármán wake with consistent cycle-to-cycle vortex shedding.

Control of flow-induced vibration of a circular cylinder using a splitter plate

A circular cylinder attached by a rigid splitter plate of different lengths was tested to examine its effects on the control of flow-induced vibration. Tests were carried out in a closed-loop water channel. A cylinder of diameter D = 20 mm and a mass ratio m* ≈ 50 was installed to oscillate in the transverse direction. A wide range of splitter length was considered, i.e., L/D = 0–3.5, at a range of reduced velocity Ur = 1–25 and the Reynolds number Re = 800–11 000. Numerical simulations were also conducted to reveal the flow structures associated with the vibration modes observed in the experiment. It is found that, as L/D increases from 0 to 0.25, the peak value of cylinder oscillation amplitude increases and appears at higher reduced velocities. When the splitter length continues to rise, galloping-type oscillations occur at L/D = 0.5 and 0.75. The transition stage has been found at L/D = 1.0. Oscillation is then significantly suppressed when the splitter length is larger than L/D = 1.5.

Study on the parameters of detached dual splitter plates and comparison with single plate for VIV suppression

In the actual marine engineering environment, vortex-induced vibration will affect the safety of cylindrical structures. Rigid splitter plates have become one of the suitable VIV suppression solutions due to their simple structure and low maintenance costs. Therefore, on the basis of numerical simulation, this paper analyses the influence of the gap between parallel and non-parallel double splitter plates and the arrangement angle of non-parallel double splitter plates on the VIV suppression effect at a fixed flow rate. In addition, the VIV suppression effect of the single and dual splitter plates with the same parameter combination is evaluated under the condition of multi-flow velocity. It is found that the parallel dual splitter plate cannot provide good VIV suppression, especially when the gap exceeds the cylinder diameter, the suppression effect begins to deteriorate. However, on the basis of a certain gap between the plates, the dual splitter plate with arrangement angle is more effective than the single splitter plate in suppressing the transverse vibration of the cylinder. Therefore, when using dual splitter plates for VIV suppression, the parallel dual splitter plates should be avoided. When a better transverse vibration suppression effect is required, the arrangement angle can be appropriately changed.

The effect of spacing on the flow-induced vibration of one-fixed-one-free tandem cylinders with a rigid splitter plate

The fluid-structure interaction mechanism of an assembly system, including a fixed upstream cylinder and a transverse oscillating downstream cylinder with a rigid splitter plate, is numerically studied at a low Reynolds number Re = 150 and mass ratio m* = 10.0. The effect of different spacing ratios (G/D = 1.5, 3.0, 5.0, and 8.0) and reduced velocities (Ur = 1.0–40.0) on the dynamic responses, hydrodynamic characteristics, and wake patterns of the downstream cylinder-plate (DCP) are analyzed in detail. The results show that, depending on the spacing ratios and the reduced velocities, different response regimes can be identified: (a) For G/D = 1.5 and 3.0, the response of the DCP presents a steady flow at low Ur where the oscillation is completely suppressed. As Ur increases, the response regime shifts to vortex-induced vibration (VIV), which is characterized by a wider lock-in bandwidth and a larger peak vibration amplitude than those of the single cylinder-plate body. (b) For G/D = 5.0 and 8.0, the response regimes consist of VIV and galloping. For the former, the upstream vortex shedding leads to a significant increase in the lift force on the DCP, and its frequency is highly synchronized with the oscillation. By contrast, multiple harmonic components of the lift force are observed in the galloping-dominated Ur range. Two prominent peaks can be identified in the power spectra. The lower peak, produced by the reattachment of the separated shear layers, is the main contributor to the oscillation. The higher peak originating from the upstream vortex shedding frequency is out of phase with the oscillation, and its contribution to the oscillation is very small.

Effect of splitter plate length on FIV of circular cylinder

The influence of the plate length on the flow-induced vibration (FIV) of a circular cylinder with a rigid splitter plate is numerically studied at a low Reynolds number of 100. The mass and damping ratios of the system are respectively m∗=10 and ζ=0. The reduced velocity (Vr) is varied from 2 to 26 and seven different nondimensional splitter plate length (L∗) values in the range of 0–2 are considered. Three different response patterns are identified in the present research, namely vortex-induced vibration (VIV), combined VIV-galloping and weak VIV-galloping. When the system is undergoing VIV, the frequency synchronisation is delayed and the lock-in range is enlarged with increasing L∗. The onset of galloping is postponed with the kink alleviated and the galloping frequency lowering. Abrupt drops in the vortex and total phases are associated with the initiation of galloping. In the galloping branch, both vortex and total forces remain in phase with the displacement. For the added mass and excitation coefficients (Cay and Cey) of the cylinder-plate assembly which have rarely been reported in the literature, Cay decreases as Vr is increased in the VIV range. Nevertheless, it leaps at the onset of galloping and the galloping response is accompanied by positive Cay values. Cey is negative in most cases and its trough appears at beginning of the VIV lock-in range or around the kink in the galloping branch. Due to the large-amplitude and low-frequency nature of the galloping oscillation, three new multi-vortex wake patterns (4P, 5P and 6P) are found to take place. Overall, for a longer splitter plate in the present study, the shear layer reattachment is observed at lower Vr and the galloping oscillation is associated with more vortex pairs.

Study on the parameters of detached splitter plate for VIV suppression

Cylindrical structures such as offshore risers and offshore platform legs will suffer fatigue damage due to Vortex-induced Vibration (VIV). It is necessary to study the suppression scheme of cylindrical VIV. The rigid splitter plate has the characteristics of simple structure, low maintenance cost, and no external energy. Therefore, it becomes one of the suitable VIV suppression schemes. Based on numerical simulations, the design of a downstream detached splitter plate is investigated at a fixed flow rate. The suppression effects of 3 main parameters, distribution gap, splitter plate width and splitter plate length, are analysed. The study found that there is an obvious effective action interval for the distribution gap. The splitter plate provides better suppression when the gap is within this interval. In addition, the length of the splitter plate is the most significant parameter for the suppression effect. When the length is too small, the vibration response of the cylinder will be further aggravated. As the length continues to increase, so does the overall suppression effect of the splitter plate. Therefore, when the 3 parameters are properly combined and the length is as long as possible within the feasible range, the splitter plate can achieve a significant suppression effect.

Comparative analysis of the flow control over a circular cylinder with detached flexible and rigid splitter plates

A comparative study is performed on a circular cylinder with both flexible and rigid splitter plates (SPs). This study has the novelty of using single and dual detached SPs located downstream of the cylinder. The dimensionless gap distance between the first splitter plate and the cylinder as well as the distance between the SPs are varied. The strain of flexible SPs can be used for energy harvesting from the flow. Therefore, a parametric study is performed to find the optimal design for placing piezoelectric polymers. The two-dimensional fluid–structure-interaction analysis is performed based on the arbitrary Lagrangian–Eulerian scheme using COMSOL Multiphysics. Flow characteristics quantities, tip amplitude, and strain are evaluated at different arrangements of the SPs. The results reveal that wake control enhances effectively by doubling the number of SPs. Strain assessments indicate that the strain of dual SPs increases by more than 100% compared to the single plate case. In addition, the amplitude of the dual SPs increases by a remarkable ratio of 18.29 compared to the single plate. In the case of rigid and flexible SPs at a certain arrangement, dramatic reductions of 97.8% and 76.35% in the Strouhal number are obtained compared to a bare cylinder. In addition, 18% drag reduction compared to the bare cylinder is recorded for the rigid SPs. The presented passive method can be used as an attractive approach in flow control as well as energy harvesting from ocean waves and sea currents.

The roles of rigid splitter plates in flow-induced vibration of a circular cylinder

While it is known that rigid splitter plates play significant roles in flow control, the exact roles of them in flow-induced vibration (FIV) have not been systematically investigated. This has motivated the present work to experimentally investigate the FIV of a cylinder equipped with an upstream rigid splitter plate (USP), a downstream plate (DSP), and symmetrically arranged splitter plates in a water tunnel with Reynolds number of 1100–7700. The length of the plate is in a range of L* = 0–3.6 (L*=L/D, L is the plate length, D is the cylinder diameter). The response characteristics, vortex evolution, fluid force, and pressure fields are thoroughly analyzed. Both USP and DSP can succeed in oscillation mitigation and drag reduction. However, dramatic galloping is observed for DSP with L* = 0.4–3.2. The low-pressure region forms near the downstream plate is beneficial to trigger galloping. For USP, only vortex-induced vibration is found, and the transition of response branches corresponds to the variation in oscillation frequency and phase jumps in total transverse force and vortex force. However, the vortex mode transition from 2S to 2P disappears with long plate length. Flow visualization reveals that the upstream vortex induced by USP alters the downstream vortex shedding. Furthermore, a high-pressure region forms near the tip of USP, yielding an obstructive force that suppresses the growth of oscillation. With the combination of USP and DSP, weak galloping is excited in a narrow range of L* = 1.0–1.8, and the linear increase is also broken due to the existence of USP.

Transition of FIV for a circular cylinder with splitter plates

A flow-induced vibration (FIV) investigation to show the transition from vortex-induced vibration (VIV) to galloping for a circular cylinder equipped with a rear rigid splitter plate was undertaken in a water tunnel at Reynolds number of 1100-7700. The length of the splitter plate is in a range of L∗=0-4.0 (L∗ = L/D, L is the plate length, D is the cylinder diameter). The dependence of oscillation characteristics, vortex evolution, force coefficients, mean added mass and effective added mass on L∗ is illustrated in detail. In the investigated L∗, five oscillation patterns are identified successively: VIV, combined VIV–galloping, separated weak VIV (WVIV)–galloping, WVIV and weak galloping, WVIV and desynchronized. For L∗ = 0.4–1.8, severe galloping is observed at high reduced velocities. The oscillation can be well suppressed when L∗>3.2. The transition from VIV to galloping, indeed, is the competition of vortex shedding and free shear layers attachment. At low reduced velocities, the oscillation is always synchronized with the vortex shedding. Beyond a critical plate length (0.4D), however, galloping is found at high reduced velocities, despite of the interference of vortex shedding. Harmonic force component at three times the oscillation frequency is identified in the galloping dominated region for L∗ = 0.4–1.8. Although it has little energy transfer to the oscillation, considerable negative effective added mass is induced.

Flow-induced vibration control of a circular cylinder by using flexible and rigid splitter plates

Flow-induced vibration (FIV) control of a circular cylinder by using a flexible splitter plate attached to the rear stagnation point is experimentally investigated. The rigid splitter plate is also applied to highlight the unique feature of the flexible splitter plate. A platform has been designed to ensure that the cylinder can only vibrate in the transverse direction. The Reynolds numbers based on the cylinder diameter and the free-stream velocity are in the range of 1680–8720. When a flexible or rigid splitter plate is attached, the vibration response of the circular cylinder is different. The vortex-induced vibration (VIV) and galloping are both observed for the rigid splitter plate cases. Though the vibration amplitude in the synchronization region is reduced by the rigid splitter plate, it increases linearly with the reduced velocity at large reduced velocities. However, the flexible splitter plate with a streamwise length greater than one cylinder diameter performs well in suppression of the vibration, and the reduction in the maximum amplitude reaches about 91% compared with the natural case. The flow pattern in the wake is changed by the splitter plate. The interaction between upper and lower shear layers is reduced, especially in the near-wake region. The shear layers shedding from the cylinder do not alternately reattach on the tip of the flexible splitter plate, thus, the galloping does not occur.

Instabilities and sensitivities in a flow over a rotationally flexible cylinder with a rigid splitter plate

This paper investigates the origin of flow-induced instabilities and their sensitivities in a flow over a rotationally flexible circular cylinder with a rigid splitter plate. A linear stability and sensitivity problem is formulated in the Eulerian frame by considering the geometric nonlinearity arising from the rotational motion of the cylinder which is not present in the stationary or purely translating stability methodology. This nonlinearity needs careful and consistent treatment in the linearised problem particularly when considering the Eulerian frame or reference adopted in this study that is not so widely considered. Two types of instabilities arising from the fluid–structure interaction are found. The first type of instabilities is the stationary symmetry breaking mode, which was well reported in previous studies. This instability exhibits a strong correlation with the length of the recirculation zone. A detailed analysis of the instability mode and its sensitivity reveals the importance of the flow near the tip region of the plate for the generation and control of this instability mode. The second type is an oscillatory torsional flapping mode, which has not been well reported. This instability typically emerges when the length of the splitter plate is sufficiently long. Unlike the symmetry breaking mode, it is not so closely correlated with the length of the recirculation zone. The sensitivity analysis however also reveals the crucial role played by the flow near the tip region in this instability. Finally, it is found that many physical features of this instability are reminiscent of those of the flapping (or flutter instability) observed in a flow over a flexible plate or a flag, suggesting that these instabilities share the same physical origin.

Flapping of heavy inverted flags: a fluid-elastic instability

Abstract

Flexible Plate in the Wake of a Square Cylinder for Piezoelectric Energy Harvesting—Parametric Study Using Fluid–Structure Interaction Modeling

Piezoelectric energy harvesters can scavenge energy from their ambient environment in order to power low-consumption electronic devices. The last two decades have seen a growing interest towards vortex-induced vibration harvesters; most harvesters consist in rigid splitter plates oscillating at higher frequencies. The concept presented here is a low-frequency undulating flexible plate placed in the wake of a square cylinder. Piezoelectric patches can be placed at the plate surface to harvest the strain energy arising when the plate bends. The flapping pattern mimics an anguilliform swimming motion. There is a great need to establish correlation between wake generating bluff body size, plate dimensions and power output. Geometric parameters were investigated using water tunnel experiments, particle image velocimetry and fluid–structure interaction modeling. Results showed that for a given plate length and within a given freestream velocity range, there is a square cylinder diameter and a thickness that optimize the plate–wake interaction. Longer plates yield greater power output but have lower flapping frequencies. Additionally, the more frequent curvature changes occurring can result in charge cancellation among the piezoelectric cells. Consequently, the estimated conversion efficiency from mechanical strain to electricity is higher for shorter plates.

Flow characteristics of a fixed circular cylinder with an upstream splitter plate: On the plate-length sensitivity

In the present study, we place a short splitter plate onto the upstream side of a circular cylinder to modify its incoming flow conditions and the wake-vortex patterns and to attenuate the aerodynamic forces. Wind-tunnel investigations are performed at a Reynolds number of Re = 2.66×104. Special interests are paid to the length sensitivity of the rigid splitter plate. The 2D particle image velocimetry (PIV) technique is employed to measure the flow patterns around the natural and controlled cylinders to reveal the great modifications of the upstream plate to the cylinder flow. Except for PIV tests, sectional pressure measurements are also conducted to obtain the pressure distribution around the cylinder surface so as to estimate the aerodynamic forces, i.e. drag and lift forces of the natural and controlled cylinders. Results of the surface-pressure measurement demonstrate clearly the control effectiveness and the surrounding flow topologies obtained by PIV system help to uncover the mechanism of the passive upstream-plate control.

Flow control over a square cylinder using attached rigid and flexible splitter plate at intermediate flow regime

A detailed flow field behind a stationary square cylinder with attached rigid and flexible splitter plates has been studied using particle image velocimetry, constant temperature anemometry, and flow visualization techniques. A wide range of lengths of the splitter plate (L/B = 0–8) are considered, and their respective wake interference is reported. The investigation is carried out at an intermediate flow regime at three Reynolds numbers 600, 1000, and 2000 (based on blocking width “B” of the cylinder). The literature seriously lacks the information on a passive flow control of bluff body wakes in this flow regime. This study shows that the wake frequency and mean drag coefficient vary nonmonotonically to splitter plate lengths. The length of the splitter plate is a critical parameter, which, apart from flow control, can also bring a significant wake transition. At L/B > 3 to L/B = 4, strong secondary vortices are shed from the trailing edge. The shedding of the secondary vortex leads to a sudden shrinkage in the recirculation bubble and an increase in the periodicity of the unsteady flow. The onset of high amplitude flapping occurs in a flexible splitter plate (L/B = 3) at Re = 2000. The vortex shedding frequency becomes higher than the first mode natural frequency of the flexible splitter plate for this length and remains in the same regime for L/B > 3. The amplitude of flapping increases up to L/B = 5 and then again recedes. The high amplitude flapping of the flexible splitter plate adversely affects the mean drag coefficient of the bluff body.

Numerical study of flow-induced vibration of a circular cylinder with attached flexible splitter plate at low

Flow-induced vibration (FIV) of an elastically mounted circular cylinder with an attached splitter plate in uniform flow is studied numerically via a stabilized space–time finite element method. The Reynolds number based on the cylinder diameter $D$ and the free-stream speed is restricted to 150. The ratio of the density of the body to that of the fluid, for the major part of the study, is 10. Two different reduced speeds are defined to quantify the compliance of the elastic support and flexibility of the splitter plate, respectively: $U_{s}^{\ast }$ based on the natural frequency of the spring–mass system and $U_{p}^{\ast }$ based on the fundamental natural frequency of the plate. Flow past a stationary cylinder ($U_{s}^{\ast }=0$) with a flexible splitter plate of length $3.5D$ is studied at different values of $U_{p}^{\ast }$. The vibration response of the plate exhibits lock-in with various eigenmodes of the plate in different ranges of $U_{p}^{\ast }$. The onsets of these lock-in regions are abrupt and hysteretic. The elastically mounted cylinder, without the splitter plate, undergoes large-amplitude vortex-induced vibration (VIV) for $4<U_{s}^{\ast }<7$. These large-amplitude oscillations are a consequence of synchronization, wherein the vortex shedding frequency locks in to the cylinder oscillation frequency. A rigid splitter plate attached to the cylinder reduces significantly the peak amplitude during VIV. Increasing the length of the plate from $1.5D$ to $3.5D$ only marginally affects the peak amplitude. It, however, leads to a wider range of lock-in. Unlike the case of an isolated cylinder, the lock-in and desynchronization regimes are not well demarcated in the presence of the splitter plate. Further, galloping is observed beyond a critical value of $U_{s}^{\ast }$; the amplitude of vibration increases with an increase in $U_{s}^{\ast }$ while the vibration frequency is relatively low and remains nearly constant. Increase in plate length delays, in terms of $U_{s}^{\ast }$, the onset of galloping. It is also found that the flexibility of the plate affects the maximum oscillation amplitude in the VIV regime. It also dictates the presence/absence of galloping. The system behaves similar to an isolated cylinder for a very flexible plate. The response is devoid of galloping, but relatively large amplitude of oscillation is observed during lock-in. The behaviour of the cylinder with a stiff plate is similar to that with the rigid one. The galloping instability sets in when the flexibility of the plate is less than a certain value ($U_{p}^{\ast }<4.7$, approximately for $U_{s}^{\ast }=22$). The VIV and galloping are separated by a range of $U_{s}^{\ast }$ in which the flow is either steady, for longer plates, or exhibits very weak vortex shedding. In the VIV regime, the plate tip and cylinder vibrate in phase for low $U_{p}^{\ast }$; their motion is out of phase for larger $U_{p}^{\ast }$. The change in phase is also associated with change in the frequency of vibration. At low $U_{p}^{\ast }$, the frequency of vibration is close to the first natural frequency of the system, while at high $U_{p}^{\ast }$ it becomes closer to the second natural frequency. The vibration amplitude of the cylinder is close to maximum in the VIV regime for $U_{s}^{\ast }=6$. Computations for various $U_{p}^{\ast }$, for $U_{s}^{\ast }=6$ and $22$, are utilized to determine optimal flexibility that leads to minimal FIV. The effect of the length of the flexible splitter plate, mass ratio and damping ratio is studied. A strategy is proposed to utilize the computations from various combinations of $U_{s}^{\ast }$ and $U_{p}^{\ast }$ to choose the appropriate flexibility of the attached splitter plate to minimize FIV.