Unsteady Aerodynamic Loads Research Articles

Real-Time Flow Control of Blade Section Using a Hydraulic Transmission System Based on an H-Inf Controller with LMI Design

Vibration and real-time flow control of the 2D blade section of wind turbines with three degrees of freedom (3-DOF), excited by external pitch motion, are investigated based on an H-inf (H∞) controller using linear-matrix-inequality (HIC/LMI) design. The real-time flow control for the purpose of aeroelastic flutter suppression includes not only the driving process of real-time physical equipment, but also the realization of real-time control algorithm in the physical controller. The aeroelastic system combined with pitch motion is controlled by a kind of HIC/LMI algorithm. The real-time external pitch motion is driven by rack-piston cylinder (RPC) using a hydraulic transmission system (HTS). The unsteady aerodynamic loads model is simplified by the HTS system. The HTS is actuated by a proportional-flow valve (PFV) which is controlled by another HIC/LMI algorithm, a novel algorithm for waveform tracking. According to the result of waveform tracking, the input current signal of PFV is realized by the configuration of the controller hardware system and its external circuits. In two types of HIC/LMI algorithms, controller stabilities are affirmed using Lyapunov analyses, and controller values are derived and obtained by using LMI designs. Flutter suppression for divergent and instable displacements is shown, with obvious controlled effects illustrated. An online monitoring experimental platform using hardware-in-the-loop simulation, based on Siemens S7-200 programmable logic controller (PLC) hardware and Kingview detection system, is built to implement pitch motion based on HTS and configure the signal input of PFV in pitch control.

Numerical investigation of the influence of passive/active flow control on ship/helicopter dynamic interface

In this research, a one-way coupling numerical method for the ship-helicopter dynamic interface was developed in combination with a Detached Eddy Simulation and a helicopter flight mechanics model. Using the method, the effects of the active and passive flow control (i.e., active jet and notch) on ship-helicopter dynamic interface was investigated, especially the control margin and unsteady aerodynamic loading characteristics of a shipborne helicopter. The results showed that although the notch modification could reduce the unsteady aerodynamic loading level, it also increased the lateral velocity component of the ship airwake, which led to the increase of the roll angle of the helicopter and the decrease of the pedal margin. In comparison, the active jet control could reduce pilot workload while had little adverse effect on control margin. The parametric studies indicated that the jet with proper strength and frequency can reduce the lateral turbulence intensity and turbulent kinetic energy levels, and alleviates the pilot workload, but if the strength and frequency is high, the small-scale vortex generated by the jet itself will make the ship airwake disordered, which has a negative effect on the control ability of the active jet to decrease the unsteady level of ship airwake. In addition, the control ability of the unsteady jet was not good as that of steady jet when the jet momentum coefficient was constant.

Prediction and Aerodynamic Analysis of Interior Noise and Wind Drag Generated by the Outside Rear-View Mirror for Commercial Vehicles

The outside rear-view mirror (OSRVM) is installed on the vehicle’s surface, which causes unwanted aerodynamic noise and wind drag during driving. It is important to use simulation methods to predict the performance of aerodynamic noise and wind drag of commercial vehicles due to the OSRVM. Considering the wind drag of the OSRVM, a combinational simulation strategy is employed to calculate external flow and interior acoustic fields of commercial vehicles, respectively. The flow field is computed a priori with an incompressible flow solver. The acoustic field was then computed based on the information extracted from the CFD solver. To obtain the interior noise level at the driver’s ears, a vibroacoustic model is used to calculate the response of the window glass structure and interior cavities, where the unsteady aerodynamic pressure loading on the two side windows’ surface is treated as the acoustic source field. The paper provides flow field and acoustic simulations for three OSRVM configuration models. The results are compared to data obtained in road sliding test measurement on the commercial vehicle. The accuracy of the hybrid simulation method is proved, and the comparative analyses verify that the OSRVM B model dramatically reduces the interior noise and wind drag of commercial vehicles.

Data-driven identification of unsteady-aerodynamics phenomena in flapping airfoils

This work presents a data-driven approach for the identification of relevant flow features and the breakdown of their contributions to unsteady forces in flapping airfoils. The method exploits the correlation between simultaneous flow-field and force measurements. The Extended Proper Orthogonal Decomposition of flow fields and force is employed to identify relevant flow features and to ascertain their contribution on unsteady aerodynamic loads. The analysis is performed in the wing-fixed non-inertial reference frame to avoid moving boundary effects in the decomposition and to accurately track flow features around the wing. This study discloses new insight into large-oscillation force modelling, allowing linking it to classic unsteady potential theories based on the small oscillations hypothesis. From modal analysis, the force is found to be related to large-scale spatio-temporal structures that model the flow behaviour in the proximity of the wing. Flow features in the mid-far wake are shown to have a negligible effect on the aerodynamic force. Two main spatio-temporal structures are found to be correlated with the loads on the wing. The bulk of chord-normal force oscillations is ascribed to the vorticity production and shedding which models the periodic variation of the circulation around the wing and its release in the wake. An alternating release of vorticity from both sides of the airfoil contributes to the determination of Leading and Trailing Edge Vortices and affects mostly the chord-wise force oscillations. The model retrieved through this approach is closely related to the potential aerodynamic-force models by Theodorsen and Garrick. Chord-normal force can be modelled as a quasi-steady circulatory contribution. The chord-wise force component is modelled by a term that can be assimilated to a non-circulatory force, which is linearly correlated to the airfoil kinematics, and by a term that can be assimilated to the Leading Edge Vortex suction.

Active Aerodynamic Load Control for Improved Wind Turbine Design

Historically, cost reduction in wind energy has been accomplished by increasing hub heights and rotor diameters to capture more energy per turbine. However, larger wind turbines cannot be expected to lead to lower LCOE without the addition of new technologies. Capital costs grow rapidly with rotor diameter, faster than the rated power, because as rotor diameter increases, the blades get heavier and more costly. The growth in blade mass with blade length is accelerated by the additional structure that must be added to withstand unsteady aerodynamic loads caused by turbulence, gusts, wind shear, misaligned yaw, upwind wakes, and the tower shadow. This paper presents a holistic design solution to integrate active load control via dielectric barrier discharge (DBD) plasma actuators into wind turbine rotors along with initial findings on load reduction, actuator development, and rotor mass reduction.

Evaluating Unsteady Fluid Dynamic Forces in Viscous Flows from the Vorticity Field

The vortex force map (VFM) method is a promising low-cost technique for predicting unsteady aerodynamic load from the vorticity field. Developed under potential flow assumption and applied to high-resolution computational fluid dynamics (CFD) data, the original VFM method needs to be further explored for viscous flows, especially at low Reynolds numbers and with incomplete knowledge of the flow data. In this paper, the VFM method is extended to general viscous flows, with both forces contributed from vorticity in the flowfield and on the body surface considered. We find that viscosity contributes to not only the skin-friction force but also a pressure force term. We also show that the extended vortex pressure force maps for general flow problems without the potential flow assumption lead to vanishing contributions from the far-field. The extended VFM method is applied to CFD flowfields for the starting flow of a cylinder and a NACA0012 airfoil, and it is used to analyze the force contribution effect of a given vortex. Moreover, acceptable accuracy of the method on truncated domains and under coarse sampling of typical particle image velocimetry measurement size is demonstrated.

Acoustic analysis of a forced-oscillating cylinder in flow using a hybrid method

An acoustic analysis based on a hybrid methodology is performed for a transversely forced-oscillating circular cylinder with the aim of understanding the sound generation mechanism. The sound is predicted both in moving-observer and moving-medium systems using the unsteady near-field flow solutions as input. Different forms of integration formulation, the effect of placement of the data surface, the impact of surface closure and averaging among various closed surfaces are investigated over a range of F=0.2 to 1.4 where F is the frequency ratio of cylinder oscillation to the natural vortex shedding frequency. The results show that the sound is mainly radiated from the cylinder surface, induced by the unsteady aerodynamic loading and cylinder movement. The impact of the hydrodynamic structures of the cylinder wake on the predicted sound signal varies in different regimes of F. For 0.2≤F≤0.7, the hydrodynamic perturbation introduces spurious noise sources on the intersecting portion of the permeable data surface. For 0.8≤F≤1.05, the mean flow of the wake affects sound propagation through a convective effect, which must be taken into account in hybrid prediction. For 1.1≤F≤1.4, the effect of the wake flow on the sound generation, propagation and prediction is small. The accuracy of hybrid prediction can be significantly improved by both the open permeable surface and surface-averaging.

Nonlinear supersonic post-flutter motion of panels with adjacent bays and thermal effects

Aerospace vehicle structures in the supersonic regime flight have their outer skin subjected to unsteady aerodynamic and thermal loading, which may lead to aeroelastic instability. Typical aerospace structures are built as multiple adjacent panels, the so-called multi-bay configuration, but early efforts to predict the supersonic flutter were based on a single panel arrangement. This work evaluates the aeroelastic behavior of supersonic multi-bay fluttering panels under thermal effects, aiming to improve the understanding of adjacent panels interaction in the nonlinear regime. The aeroelastic model is established by using the first-order quasi-steady piston theory in conjunction with isotropic panel model using the von Kármán’s assumptions to account for geometrical nonlinearities. The Newmark time-integration method is used to evaluate the resulting equations of motion. The Hopf bifurcation behavior that determines the flutter onset, thermo-buckling loading, phase portrait plots, and bifurcation diagrams for two adjacent panels are presented. The numerical results show the detrimental aspect of thermal loading in the aeroelastic behavior of fluttering panels, and the new findings corroborate with some recent studies that highlight the difference in the nonlinear flutter behavior between a single panel and multi-bay panels. Moreover, the existence of limit cycle oscillations amplitude jumps from a certain level of flow dynamic pressure is also observed. The multi-bay panels configuration also shows the anticipation of the buckled to the limit cycle oscillation solutions, when compared with a single panel analysis. Results indicate that simplified single bay panel assumptions can underestimate the post-flutter oscillations amplitudes of the adjacent bay. Such dynamic behavior may lead to a negative impact on aircraft structural design and fatigue life estimation.

Effect of unsteady aerodynamic loads on driving safety and comfort of trains running on bridges

In order to investigate the effects of unsteady aerodynamic loads on the driving safety and comfort of trains running on bridges, a three-dimensional and multi-body system model of train–track–bridge was established and the dynamic responses of the coupling system were calculated by combining the finite element software ANSYS with the multi-body dynamics software SIMPACK. The driving safety and comfort of a train running on a bridge under steady and unsteady aerodynamic loads were compared and analyzed. The effects of different crosswind speeds on the driving safety of the train running on the bridge under unsteady aerodynamic loads were studied. It is found that the index values of the driving safety and comfort of the train at the speed of 200–300 km/h without the wind loads are smaller (meaning safer) than those of the train under the wind loads. When the average speed of crosswind is 20 m/s, the driving safety assessment results of the train are better and its comfort assessment results are more conservative with considering the unsteady aerodynamic loads than the steady wind load case. When the average speed of crosswind is smaller than 10 m/s and the train speed is 250 km/h, the driving safety and comfort of the train on the bridge meet the requirements, and the level of stability can reach “good” or above. Through the analysis of driving safety of the train on the bridge under different crosswind speeds, the threshold values of safe driving were obtained, which can provide a better basis for the safe operation of trains on bridges.

Controlled axisymmetric body-wake coupling in a pitching motion

The coupling between a pitching axisymmetric bluff body and its wake is modified in wind tunnel experiments using controlled interactions between fluidic actuators and the cross-flow over its aft end. The model trajectory is controlled using eight servo-controlled support wires with inline force transducers that are operated in closed loop with feedback from a motion analysis system which effects control authority of the wind tunnel model in all six degrees of freedom. The model dynamics studied in the present work is constrained to pitch. Actuation is effected by two integrated aft-facing synthetic jet actuators in the plane of the body pitch oscillation such that each actuator effects a time-dependent segment of local flow attachment over the aft surface. The present investigation focuses on the reciprocal relation between the response of the near and far wake to the actuation and the associated changes in the induced aerodynamic loads when the body executes nearly time-harmonic pitch over a range of reduced oscillation frequencies (up to k = 0.26) for ReD up to 2.3 × 105. The response of the wake to stabilizing and destabilizing actuations that effect reduction or enhancement of the aerodynamic loads is investigated using particle image velocimetry (PIV) and hotwire anemometry in the near and far wake, respectively. It is shown that the studied flow control approach induces aerodynamic loads that are comparable to the loads on the base flow pitching motions and therefore may be suitable for in-flight stabilization. The global unsteady aerodynamic loads on a pitching axisymmetric bluff body are controlled by modification of the coupling between the flow over body and its near wake using two synthetic jet actuators in the plane of motion on the body’s aft end. This actuation results in a time-dependent partial flow attachment of the nominally axisymmetric separating shear layer of the base flow over the aft end of the body, and the asymmetric changes have a profound effect on the evolution of the wake. These changes in the wake dynamics feed back to alter the global aerodynamic forces and moments, leading to about a 50% increase or decrease in the dynamic lift force or pitching moment, depending on the flow control strategy.

Flow analysis of the deep dynamic stall of wind turbine airfoil with single-row and double-row passive vortex generators

This paper aims to understand the influence of vortex generators (VGs) on deep dynamic stall of the NREL S809 airfoil. The fully-resolved URANS method is used to predict aerodynamic responses of the airfoil with both single-row and double-row VGs. On one hand, single-row and double-row VGs are found to attenuate the force fluctuation and postpone the extension of flow separation when the airfoil pitches up. The onset of deep dynamic stall is therefore significantly delayed with the maximum lift coefficient increased beyond 40%. This indicates that VGs are effective in controlling deep dynamic-stall behavior. On the other hand, single-row and double-row VGs are found to make a great difference in aerodynamic responses when the airfoil pitches down. Single-row VGs undermine the torsional aeroelastic stability and have the potential risk of making the airfoil flutter. Double-row VGs can accelerate the flow reattachment effectively, and quickly restore the decreased aerodynamic force near the maximum angle of attack. These findings also imply that deep dynamic stall with VGs becomes highly complicated, because VGs can be fully submerged in separation vortices. In general, double-row VGs perform better than single-row VGs to control deep dynamic stall. This study is believed to assess the VG performance in controlling highly unsteady aerodynamic loads on wind turbines.

Efficient prediction of classical flutter stability of turbomachinery blade using the boundary element type numerical method

In this paper classical flutter phenomena in power turbine rotor is studied. A medium fidelity 2D flow solver based on boundary element method is developed for this purpose. The classical flutter parameters in turbomachinery cascades such as aerodynamic damping at different inter-blade phase angle are estimated using flutter stability analysis flow solver. The flow solver is developed using 2D unsteady potential flow based panel method. The unsteady aerodynamic loading on the vibrating cascade is estimated using a traveling-wave mode oscillation. The simulated aerodynamic damping and pressure coefficient using boundary element method are compared against both experimental data and the computational fluid dynamics model’s results at different flow conditions. The boundary element based method results demonstrate good agreement with experimental data. The boundary element based flow solver shows significant reduction in computational time compared to computational fluid dynamics model.

Effect of platform disturbance on the performance of offshore wind turbine under pitch control

AbstractThe aerodynamic performance of offshore floating wind turbines (OFWTs) is more complicated than onshore wind turbines due to 6‐degree of freedom (DOF) motion of the floating platform. In the current study, the aerodynamic analysis of a horizontal‐axis floating offshore wind turbine is performed with the aim of studying the effects of floating platform movement on the aerodynamic characteristics of the turbine in the presence of a pitch angle control system. The National Renewable Energy Laboratory (NREL) 5‐MW offshore wind turbine is selected as the baseline wind turbine. For this sake, the unsteady blade element momentum method with dynamic stall and dynamic inflow models have been employed to obtain the unsteady aerodynamic loads. The baseline pitch angle control system is assumed to be coupled with the aerodynamic model to maintain the rated condition of the wind turbine and also to approach a closer model of wind turbine. In case of pitching motion input, the reduction of mean power coefficient for tip speed ratios (TSRs) less that 7 is expected by an amount of 16% to 20% at pitch amplitude of 2° and frequency of 0.1 Hz. For high TSRs, the trend is reverse with respect to fixed‐platform case. The mean thrust coefficient is reduced for almost all range of TSRs with maximum loss of 37%. Moreover, the mean control pitch angle that is an index of control system effort is increased. The results also represent the importance of considering the pitch control system for aerodynamic analysis of disturbed OFWT.

Global instability of wing shock-buffet onset

Shock buffet on wings encountered in edge-of-the-envelope transonic flight remains an unresolved and disputed flow phenomenon, challenging both fundamental fluid mechanics and applied aircraft aerodynamics. Its dynamics is revealed through the interaction of spanwise shock-wave oscillations and intermittent turbulent boundary-layer separation. Resulting unsteady aerodynamic loads, and their mutual working with the flexible aircraft structure, need to be accounted for in establishing the safe flight envelope. The question of global instability leading to this flow unsteadiness is addressed herein. It is shown for the first time on an industrially relevant configuration that the dynamics of a single unstable oscillatory eigenmode plays a prominent role in near-onset shock buffet on a quasi-rigid wing. Its three-dimensional spatial structure, previously inferred both from experiment and time-marching simulation, describes a spanwise-localised pocket of shear-layer pulsation synchronised with an outboard-propagating shock oscillation. The results also suggest that the concept of a critical global shock-buffet mode commonly reported for two-dimensional aerofoils also applies to three-dimensional finite and swept wings, albeit different modes at play. Specifically, the modern wing design, NASA Common Research Model, with publicly available geometry and experimental data for code validation is studied at a free-stream Mach number of 0.85 with Reynolds number per reference chord of and varying angle of attack between 3. 5° and 4. 0° targeting the instability onset. Strouhal number at instability onset just above 3. 7° is approximately 0.39. At the same time, a band of eigenmodes shows reduced decay rate in the Strouhal-number range of 0.3 to 0.7, with additional unstable oscillatory modes appearing beyond onset. Importantly, those emerging modes seem to discretise the continuous band of medium-wavelength modes, as recently reported for infinite swept wings using stability analysis, hence generalising those findings to finite wings. Through conventional time-marching unsteady simulation it is explored how the critical linear eigenmode feeds into the nonlinearly saturated limit-cycle oscillation near instability onset. The established numerical strategy, using an iterative inner–outer Krylov approach with shift-and-invert spectral transformation and sparse iterative linear solver, to solve the arising large-scale eigenvalue problem with an industrial Reynolds-averaged Navier–Stokes flow solver means that such a practical non-canonical test case at a high-Reynolds-number condition can be investigated. The numerical findings can potentially be exploited for more effective unsteady flow analysis in future wing design and inform routes to flow control and model reduction.

NUMERICAL ANALYSIS OF THE TURBOMACHINE BLADE ROW AEROELASTIC OSCILLATIONS WITH TAKING INTO ACCOUNT THE DISC DEFORMATION

The unsteady phenomena caused by blades oscillations by action of forced forces are characterized with energy change between gas flow and oscillating blades and formulate the base of physical mechanism of self-excited oscillations that can or to attenuate (aerodamping), or to be displayed in stable form of autooscillations, or in unstable form of flutter, which can activate to the structure destruction. Therefore aeroelastic blades behaviour represents the important problem of reliability and safety of gas and steam turbines with high aerodynamic indicators and high loaded blades. One of approaches to increase the stable blades oscillations is detuning of natural forms bound to disc deformation. There presented the numerical analysis of effect of disc deformation on aeroelastic blades oscillations of turbomachine blade row. The disc deformation is characterized by disc nodal diameters number that defines the interblade phase angle of blades oscillations shift (IBPA), and impacts on unsteady aerodynamic loads and blades oscillations amplitudes. In paper there shown that decrease of IBPA causes to increase of aeroelastic stability that is to reduction of blades oscillations amplitudes. The proposed numerical method of coupled aeroelastic problem solution for threedimensional transonic ideal gas flow allows to predict aeroelastic behaviour of blades including the forced, self-excitation oscillations and autooscillations with purpose to increase the efficiency and reliability of turbomachines blades devices.

Reduced order nonlinear aeroelasticity of swept composite wings using compressible indicial unsteady aerodynamics

Nonlinear dynamic aeroelasticity of composite wings in compressible flows is investigated. To provide a reasonable model for the problem, the composite wing is modeled as a thin walled beam (TWB) with circumferentially asymmetric stiffness layup configuration. The structural model considers nonlinear strain displacement relations and a number of non-classical effects, such as transverse shear and warping inhibition. Geometrically nonlinear terms of up to third order are retained in the formulation. Unsteady aerodynamic loads are calculated according to a compressible model, described by indicial function approximations in the time domain. The aeroelastic system of equations is augmented by the differential equations governing the aerodynamics lag states to derive the final explicit form of the coupled fluid-structure equations of motion. The final nonlinear governing aeroelastic system of equations is solved using the eigenvectors of the linear structural equations of motion to approximate the spatial variation of the corresponding degrees of freedom in the Ritz solution method. Direct time integrations of the nonlinear equations of motion representing the full aeroelastic system are conducted using the well-known Runge–Kutta method. A comprehensive insight is provided over the effect of parameters such as the lamination fiber angle and the sweep angle on the stability margins and the limit cycle oscillation behavior of the system. Integration of the interpolation method employed for the evaluation of compressible indicial functions at any Mach number in the subsonic compressible range to the derivation process of the third order nonlinear aeroelastic system of equations based on TWB theory is done for the first time. Results show that flutter speeds obtained by the incompressible unsteady aerodynamics are not conservative and as the backward sweep angle of the wing is increased, post-flutter aeroelastic response of the wing becomes more well-behaved.

Analysis of FOWT dynamics in 2-DOF hybrid HIL wind tunnel experiments

This paper presents the main results of experimental hybrid/HIL wind tunnel tests of the National Renewable Energy Laboratory (NREL) 5 MW wind turbine coupled with the DeepCwind semi-submersible floating platform. Experiments in still water and in irregular waves without wind are compared to corresponding FAST simulations in order to assess the effectiveness of the proposed HIL methodology and to highlight the main sources of uncertainty. Tests are repeated under three wind conditions, corresponding to different wind turbine operating points, to evaluate the effect of the aerodynamic force field on the overall system response. Experimental results are compared to the output of FAST simulations to investigate its prediction capability with respect to the influence of unsteady aerodynamic loads on the FOWT dynamics.

Aerodynamic Load Characteristics of High-Speed Train under Different Wind Load Models

In order to study the difference of unsteady aerodynamic loads of high-speed train under different wind load models, considering the assumption of uniform wind and the random characteristics of wind, the turbulent velocity field is generated by CDRFG method. A numerical model of cross-wind aerodynamics for high-speed trains was established by using STAR-CCM+, and solved by the IDDES method. The time history curve of fluctuating wind was transported into the computational domain as a function to calculate the computational fluid dynamics directly. The variation law and difference of aerodynamic load of high-speed train under two kinds of wind load models are obtained. With the increase of yaw angle, the maximum, average and standard deviation of aerodynamic load coefficient increase, and the coefficient fluctuation becomes more intense. The aerodynamic performance of the head car is the worst among the three cars. The PSD of aerodynamic load under stochastic wind is higher than that under uniform wind. With the increase of yaw angle, the corresponding PSD difference of aerodynamic load between stochastic wind and uniform wind increases, which indicates that the effect of pulsation is more obvious.

Postponing the Onset and Alleviating the Load of Transonic Buffet by Using Steady and Periodic Tangential Slot Blowing

Transonic buffet not only influences the structural integrity, handling quality and ride comfort, but also limits the flight envelope of transporters and airliners. To delay buffet onset and alleviate the buffet load, the effects of both steady and periodic tangential slot blowing are investigated. The results show that steady tangential blowing on the airfoil upper surface can postpone the buffet onset margin and evidently increase the lift coefficient at incidence angles near and above the buffet onset case of the clean airfoil. Under buffeting conditions of the clean airfoil, unsteady aerodynamic loads can be greatly suppressed by both steady and periodic blowing. The control effort is depicted as reduced wedge effect and weakened dynamic effect. The buffet mechanism includes (a) the feedback loop between the Kutta wave and the separation bubble under the shock foot, and (b) the interaction between the shear layer shed by the shockwave and Kutta waves. Under blowing conditions, the upstream creeping Kutta waves are prevented, and the intensity of the shear layer shed by the shockwave into separated flows is evidently reduced. Parametric studies show that the control effect is reduced as the blowing slot moves downstream, and steady blowing at 41% x/c is the most favorable control case.

Study of the Effect of the Scatter of Acoustic Modes on Turbine Flutter

Abstract The prediction of aerodynamic damping is a relevant issue for turbomachinery design trends. Most of the conventional analysis methodologies for the study of aeroelastic forcing in use until recently neglect any hypothetical effects of adjacent rows. However, in recent years, it has become unquestionable that acoustic waves and nearly convected perturbations reflected in neighboring rows play a significant role in the evaluation of the overall unsteady loading of the blades. In this paper, a study of the impact of these effects in flutter stability margin is performed. For this analysis, ITP Aero’s in-house unsteady 3D frequency domain linearized RANS solver is used. The subject of this research is a setup which is a close representation of a proper LPT geometry. The influence of neighboring rows is examined, taking into consideration how the interactions between rows are scattered into several circumferential modes, as well as into radial modes. A quantitative assessment of all these effects is performed to understand the relative relevance of each one of them, and the results of unsteady aerodynamic blade loading are compared with those of a single-row simulation.