Wake Interaction Research Articles

Wake interaction studies of flow past tandem circular cylinders for different diameter and gap ratios

Wake interaction studies of flow past tandem circular cylinders for different diameter and gap ratios

Investigating the Level of Fidelity of an Actuator Line Model in Predicting Loads and Deflections of Rotating Blades under Uniform Free-Stream Flow

In this paper, the accuracy of an in-house Actuator Line (AL) model is tested on aeroelastic simulations of a Wind Turbine (WT) rotor and a helicopter Main Rotor (MR) under uniform free-stream flow. For the scope of aeroelastic analyses, the AL model is coupled with an in-house multibody dynamics code in which the blades are modeled as beams. The advantage from the introduction of CFD analysis in rotorcraft aeroelasticity is related to its capability to account in detail for the interaction of the rotor wake with the boundary layer developed on the surrounding bodies. This has proven to be of great importance in order to accurately estimate the aerodynamic forces and thus the corresponding structural loads and deflections of the blades. In wind turbine applications, a good example of the above is the rotor/ground interaction. In helicopter configurations, the interaction of MR with the ground or the fuselage and the interaction of tail rotor with the duct in fenestron configurations are typical examples. Furthermore, CFD aerodynamic analysis is an obvious modeling option in which the above mentioned asset can be combined with the consideration of the mutual interaction of the rotor with the ambient turbulence. A WT rotor operating inside the atmospheric boundary layer under turbulent free-stream flow is such a case. In the paper, AL results are compared against Blade Element Momentum (BEM) and Lifting Line (LL) model results in the case of the WT, whereas LL and measured data are considered in the helicopter cases. Blade loads and deflections are mainly compared as azimuthal variations. In the helicopter MR cases, where comparison is made against experimental data, harmonic analysis of structural loads is shown as well. Overall, AL proves to be as reliable as LL in the canonical cases addressed in this paper in terms of loads and deflections predictions. Therefore, it can be trusted in more complex flow conditions where viscous effects are pronounced.

Comparative experimental investigation into wake characteristics of turbines in three wind farms areas with varying terrain complexity from LiDAR measurements

Large-scale turbines’ wake expansion is influenced both by atmospheric conditions and terrain effects. This paper conducted comparative experimental measurements on the wind turbines’ wake in three wind farms areas of different terrain complexities using Doppler Light Detection and Ranging (LiDARs). Three wind farm areas of different terrain complexities in North China were selected and wake expansions were detected by three LiDARs over a six-month measurement period. Three wake interaction conditions of separate, full, and half wakes were discussed separately in the aforementioned three wind farm areas of different terrain complexities with a total of nine different cases. The velocity deficit (VD) exhibited a complex expression with the terrain complexity increases. In separate wake condition, the VD trend of flat terrain was gentle, and the decline slopes in moderate and complex areas were 0.1243 and 0.0082 respectively. Results also showed that the wake width (WW) became wider as the terrain complexity increases, and the more complex the terrain was, the faster the WW changes. In separate wake, upstream of full and half wake, WWs in moderate and complex areas showed the same growth trend with an increase rate of 87.5%, which was twice as much as that in flat terrain. Results of this study can provide guidance for the micro-siting arrangement and control strategies of wind turbines in wind farms with different terrain complexities.

Joint optimization of wind farm layout considering optimal control

The wake effect is one of the leading causes of energy losses in offshore wind farms (WFs). Both turbine placement and cooperative control can influence the wake interactions inside the WF and thus the overall WF power production. Traditionally, greedy control strategy is assumed in the layout design phase. To exploit the potential synergy between the WF layout and control so that a system-level optimal layout can be obtained with the greatest energy yields, the layout optimization should be performed with cooperative control considerations. For this purpose, a novel two-stage WF layout optimization model is developed in this paper. Cooperative WF control of both turbine yaw and axis-induction are considered in the WF layout design. However, the integration of WF control makes the layout optimization much more complicated and results in a large-scale nonconvex problem, hindering the application of current layout optimization methods. To increase the computational efficiency, we leverage the hierarchy and decomposability of the joint optimization problem and design a decomposition-based hybrid method (DBHM). Instead of manipulating all the variables simultaneously, the joint optimization problem is decomposed into several subproblems and their coordination. Case studies are carried out on different WFs. It is shown that WF layouts with higher energy yields can be obtained by the proposed joint optimization compared to traditional separate layout optimization. Moreover, the computational advantages of the proposed DBHM on the considered joint layout optimization problem are also demonstrated.

The influence of tidal turbine arrangement on the wake interaction in shallow water

The arrangement of tidal turbines in the tidal farm is known to be complicated due to the resistance to the tidal flow which causes the flow to be channeled around the individual devices. To successfully implement the tidal turbine, the wake interaction between the device and its implication needs to be fully understood. Typically, the wake interaction in the array depends on the arrangement and spacing between the device in the array. In this study, a numerical analysis is conducted through the use of Computational Fluid Dynamic (CFD) approach to investigate the influence of the array setup in shallow water application and to propose a suitable array layout for possible application in Malaysia. The numerical analysis is carried out with 2 combination sets of lateral and longitudinal spacing covering 15 turbines in staggered and squared array layout. Hypothetical ‘actuator’ disk and ‘actuator’ cylinder model are used to represent the Horizontal axis turbine (HATT) and Vertical axis turbine (VATT) respectively. The results showed that the VATT model has faster wake recovery and obeys the definition of the far wake. Staggered arrays with bigger spacing are preferable for application in shallow water due to the low probability of wake merging between the rows.

Noise from a Model-Scale Vertical-Axis Wind Turbine

Vertical-axis wind turbines are an attractive option for small-scale wind-power installations. In this application, noise is crucially important. To investigate the problem, measurements taken from a model-scale turbine in a wind tunnel are considered. The sound radiated by the model is clearly evident in the cross spectra from a pair of flush-mounted microphones. Parameter studies show that, in the normal operating range, speed is the dominant factor. The main source appears to be blade self-noise, although there are also indications of blade–wake interaction in the downstream half of the rotation path. Boundary-layer trips have a significant impact, showing that laminar instability is an important contributor to the self-noise. It will remain a risk at full scale, and its absence should be ensured at the design stage. To minimize the remaining sound radiation (at a given wind speed), configurations with lower tip-speed ratio at maximum power output should be preferred to ones having higher values of this parameter.

난류생성기 판 형상에 의한 난류화염 특성 연구

The cross-shaped fractal grids which have RRBT(reduced ratio of bar thickness) and the hexagonal grid were used to generate various turbulent flow properties for low swirl flames. In the non-reacting flow field with the fixed bulk velocity at 10 m/s, decreasing RRBT induces the increasing turbulent intensity(ISUBU/SUB) with the delay in the location of lowest turbulent mean velocity(Ū) and highest turbulent fluctuation(ú) due to vortex shedding from the bar thickness. This phenomenon was well explained by a wake interaction theory using axial velocity profiles at the centerline. At various equivalence ratios for Hexa. and fractal grids, the characteristics of low swirl flames could be identified to a thin reaction zone regime in the Borghi – Peter regime diagram. Decreasing RRBT increases ISUBU/SUB in front of flame brush with increasing turbulent local displacement speeds (SSUBT,LD/SUB) via a linear correlation. The turbulent Reynolds number, ReSUBT/SUB composed of the ratio of length scale and velocity components induced the proportional trends in non linear relationship showing that the influence of the length scale ratio. The empirical correlation study of SSUBT,LD/SUB as a function of ReSUBT/SUB and ú/SSUP0/SUPSUBL/SUB was investigated to compare the influence of velocity and turbulent length scales ratio. The result of linear correlation equation with SSUBT,LD/SUB indicates the influence of velocity factors greater than ReSUBT/SUB through the exponential factor.

A new method for simulating multiple wind turbine wakes under yawed conditions

Counter-rotating vortices generated in wake steering not only deform the turbine wake, but also can make the wake trajectory of a non-yawed downwind turbine deviate from its rotor centerline, referred to as “secondary wake steering” phenomenon. Recent studies have also shown that the vortex interactions become clearer when the wind farm includes multiple turbines. However, in the common analytical models for active yaw control, the effects of these vortices are not considered. Evidently, this omission can lead to a decrease in model prediction accuracy. To compensate for it, a new analytical wind farm model is proposed. It adopts a physical-based momentum conserving wake superposition method to deal with the interaction of multiple wakes, in which, not only combining the streamwise velocity deficit of each individual yawed wind turbine, but also the transverse velocity from different wakes. Additionally, an “added yaw angle” is defined for a downwind turbine operating in upstream yawed turbine wakes, to reflect the change in local wind direction it perceives. For validation purposes, the LES wind field obtained from the SOWFA tool is used as a reference, and the newly proposed model is found to agree well with LES results and outperforms the representative conventional analytical model in almost all test cases. The new model can successfully reproduce the “secondary wake steering” phenomenon in the overlapped wake, and provides significant improvements in predicting power production of wind turbines.

LiDAR and SCADA data processing for interacting wind turbine wakes with comparison to analytical wake models

This study is a follow up on a previous one carried out within the frame of the French project SMARTEOLE, during which, a ground-based scanning LiDAR measurement campaign was conducted in the onshore wind farm of Sole du Moulin Vieux. That previous study focused on the wakes of two wind turbines that experienced different degrees of interaction depending on the incoming wind direction, through the processing of LiDAR measurements. The measurement duration (7 months) ensured the statistical convergence of the ensemble-averaged flow fields obtained after holding a categorisation process based on the wind speed at hub height, wind direction, and atmospheric stability, where only near-neutral stability conditions were considered. The present study focuses on integrating the operational data of the wind turbines through SCADA processing to complement the LiDAR wake field observations and to be used as an input for analytical wake models. First, the correlation between the atmospheric stability, deduced from MERRA-2 dataset, and the free-stream turbulence intensity, measured by the wind turbines’ anemometers, is studied for different wind speed ranges. It is observed that the turbulence intensity tends towards a consistent value as the atmospheric stability approaches near-neutral stability conditions, giving confidence into the applied strategy of data categorisation based on MERRA-2 outputs. The influence of the degree of wake interaction on the wake added turbulence, the velocity and power deficits between both turbines is assessed. Clear trends between the wake added turbulence and both the velocity and power deficits are detected. Consequently, two fitting laws are proposed. Then, different analytical wake models and wake superposition methods are fed with the operational data deduced from the processed SCADA data, and are used for predicting the evolution of the velocity deficit within the wake. Some statistical metrics are used for error quantification of the different engineering wake models compared to the scanning LiDAR measurements, used as reference, and Blondel and Cathelain produces the closest results to the field measurements.

Deep learning-aided model predictive control of wind farms for AGC considering the dynamic wake effect

To provide automatic generation control (AGC) service, wind farms (WFs) are required to control their operation dynamically to track the time-varying power reference. Wake effects impose significant aerodynamic interactions among turbines, which remarkably influence the WF dynamic power production. The nonlinear and high-dimensional nature of dynamic wake model, however, brings extremely high computation complexity and obscure the design of WF controllers. This paper overcomes the control difficulty brought by the dynamic wake model by proposing a novel control-oriented reduced order WF model and a deep-learning-aided model predictive control (MPC) method. Leveraging recent advances in computational fluid dynamics (CFD) to provide high-fidelity data that simulates WF dynamic wake flows, two novel deep neural network (DNN) architectures are specially designed to learn a dynamic WF reduced-order model (ROM) that can capture the dominant flow dynamics. Then, a novel MPC framework is constructed that explicitly incorporates the obtained WF ROM to coordinate different turbines while considering dynamic wake interactions. The proposed WF ROM and the control method are evaluated in a widely-accepted high-dimensional dynamic WF simulator whose accuracy has been validated by realistic measurement data. A 9-turbine WF case and a larger 25-turbine WF case are studied. By reducing WF model states by many orders of magnitude, the computational burden of the control method is reduced greatly. Besides, through the proposed method, the range of AGC signals that can be tracked by the WF in the dynamic operation is extended compared with the existing greedy controller.

On wake modulation and interaction features of a pair of dual-step circular cylinders in side-by-side arrangements

The proximity interference and the vortex dislocation are fundamental fluid dynamic features that determine a wake pattern of dual-step circular cylinders in a side-by-side arrangement. Each dual-step cylinder consists of two coaxial cylinders with different diameters. A complex wake modulation is expected due to an intrinsic interaction between the vortex shedding of the larger-diameter cylinder (LC) and the smaller-diameter cylinder (SC), and to the cross-wake interaction of side-by-side cylinders in a uniform flow. To understand the physics of fluid wake modulations, three-dimensional direct numerical simulations of the flow around a pair of dual-step circular cylinders in side-by-side arrangements are performed and investigated. Six simulation cases are presented with different combinations of diameter ratio (1.33–2.00), gap ratio (1.00–3.17), and the Reynolds number (60–200) in a laminar flow regime, providing key insights into the two distinct LC-dominated and SC-governing wake modulation characteristics. For the LC-dominated wake modulation, the wake pattern of side-by-side cylinders is determined by the predominant vortex dynamics in the LC wake. For the SC-governing wake modulation, the LC wake pattern becomes modulated and controlled by the SC wake through the connections of vortex tubes shed downstream of the two nonuniform cylinders. Owing to the proximity interference and vortex dislocation, these new evolutionary wake modulations result in distinct wake patterns, vortex structures, and associated hydrodynamic force features for the pair of side-by-side dual-step circular cylinders.

Wind farm set point optimization with surrogate models for load and power output targets

This study presents a methodology for wind farm set point optimization, which allows including both loads and power output as optimization criteria. The primary control strategy investigated involves de-rating of individual turbines in the wind farm. The optimal de-rating level of each individual turbine is determined by using accurate and computationally efficient surrogate models, mapping the dependency between the choice of de-rating strategy for a given turbine and the load and power outputs of downwind turbines. A case study based on the Lillgrund offshore wind farm shows that for specific wind directions with strong wake interactions, it may be possible to achieve a net gain in power output in the order of 5% at specific mean wind speeds. Alternatively, maintaining nominal power output but optimizing the load distribution could lead to substantial fatigue load reductions.

Boundary-Layer Dynamics in Wall-Resolved LES Across Multiple Turbine Stages

Modern turbomachinery relies on accurate prediction of the flow and especially the state of turbulence to achieve the required level of performance. Transition, relaminarization, wake interactions, and interrow influence form complex, highly unsteady flow patterns. Large eddy simulation (LES) emerges as a promising method to deliver improved accuracy over Reynolds-averaged Navier–Stokes (RANS) approaches as the major energy-carrying scales are fully resolved. However, for wall-bounded flows, modeling of (parts of) the boundary layer might still be inevitable to keep the computational costs manageable. In this paper, we aim to characterize and analyze the boundary-layer state in such a scenario. We employ the high-order discontinuous Galerkin spectral element method to perform a wall-resolved LES of a stator-rotor-stator cascade ( up to 0.65, up to ). The interfaces between the blade rows are treated with a high-order accurate sliding mesh approach. Time-averaged performance characteristics are compared against experimental and numerical data. The temporal evolution of the solution is first assessed through the phase-averaged flowfield at different stator-rotor positions. Subsequently, special emphasis is placed on the spatiotemporal evolution of turbulence near the blade surface. Boundary-layer profile and energy spectra analysis are used to give insight into the turbulence development. This investigation not only reveals the complexities of the boundary-layer dynamics but can also serve as benchmark and reference for evaluation and development of wall-modeled LES approaches for turbomachinery applications.

Aeromechanics and Aeroelastic Stability of Coaxial Rotors

Coaxial rotor aeroelasticity is complex due to the counter-rotating wake system, rotor lift offset, periodic blade passage loads, unsteady rotor wake interactions, reduced rotor speed, and stiff hingeless blades. In this study, the aeroelastic stability of a coaxial rotor is examined in hover and forward flight. The rotor wake is modeled with the viscous vortex particle method, a grid-free approach for calculating vortex interactions over long distances. The spanwise blade aerodynamic loading is calculated using a computational-fluid-dynamics-based reduced-order model in attached flow, and the ONERA dynamic stall model in separated flow. Two propulsive trim procedures are developed: one with the propulsor not operating, and the other with the vehicle at level attitude. An aeroelastic stability analysis based on Floquet theory is applied to the periodic system. A novel graphical method is developed to identify coupling between blade modes of the two rotors. The effects of lift offset and advance ratio on the hub loads, inflow distribution, and aeroelastic stability are examined to provide an improved physical understanding of the aeroelastic interactions. Results indicate that the blade passage effect is caused by the bound-circulation-induced inflow. The first and second lag modes are the least stable modes in hover and forward flight.

Very low Reynolds number causes a monotonic force enhancement trend for a three-dimensional hovering wing in ground effect

This research reports the numerical results of the ground effect trend for a three-dimensional flapping insect wing at a very low Reynolds number (Re = 10). It demonstrates that the ground effect trend at this Re has a ‘single force regime,’ i.e. the forces only enhance as the ground distance decreases. This phenomenon is unlike the widely expected non-monotonic trend publicized in previous studies for higher Reynolds numbers, that shows ‘three force regimes,’ i.e. the forces reduce, recover, and also enhance as the ground distance decreases. The force trend in the ground effect correlates to a similar trend in wing–wake interaction or the downwash strength on the wing’s head. At very low Re (10), the very large viscosity causes diffused vortices and less advected vortex wake, while at relatively high Re, the vortices are easily separated from the wing and then advected downwards. This different development of the vortex wake caused different force trends for the flapping wing in the ground effect. Furthermore, by examining only the first stroke when there is no vortex wake, we found that the ‘ramming effect’ enhances the forces on the wing. This effect increases the pressure of the lower wing surface due to the squeezed air between the wing and the ground. The ‘ramming effect’, combined with the reduced downwash (or wing–wake interaction) effect, causes the force enhancement of the wing near the ground’s vicinity. It is further comprehended that the trend is dependent on Re. As the Re is increased, the trend becomes non-monotonic. The effect of varying angles of attack, flapping amplitude and wing planform at very low Re does not change this trend. This ground effect might help insects by enhancing their lift while they hover above the surface. This finding might prove beneficial for developing micro air vehicles.

Convolutional neural networks for fluid flow analysis: toward effective metamodeling and low dimensionalization

We focus on a convolutional neural network (CNN), which has recently been utilized for fluid flow analyses, from the perspective on the influence of various operations inside it by considering some canonical regression problems with fluid flow data. We consider two types of CNN-based fluid flow analyses: (1) CNN metamodeling and (2) CNN autoencoder. For the first type of CNN with additional scalar inputs, which is one of the common forms of CNN for fluid flow analysis, we investigate the influence of input placements in the CNN training pipeline. As an example, estimation of drag and lift coefficients of an inclined flat plate and two side-by-side cylinders in laminar flows is considered. For the example of flat plate wake, we use the chord Reynolds number \(\hbox {Re}_\mathrm{c}\) and the angle of attack \(\alpha \) as the additional scalar inputs to provide the information on the complexity of wake. For the wake interaction problem comprising flows over two side-by-side cylinders, the gap ratio and the diameter ratio are utilized as the additional inputs. We find that care should be taken for the placement of additional scalar inputs depending on the problem setting and the complexity of flows that users handle. We then discuss the influence of various parameters and operations on the CNN performance, with the utilization of autoencoder (AE). A two-dimensional decaying homogeneous isotropic turbulence is considered for the demonstration of AE. The results obtained through the AE highly rely on the decaying nature. Investigation on the influence of padding operation at a convolutional layer is also performed. The zero padding shows reasonable ability compared to other methods which account for the boundary conditions assumed in the numerical data. Moreover, the effect of the dimensional reduction/extension methods inside CNN is also examined. The CNN model is robust against the difference in dimension reduction operations, while it is sensitive to the dimensional extension methods. The findings of this paper will help us better design a CNN architecture for practical fluid flow analysis.

Mechanism of wake-induced flow dynamics in tandem flapping foils: Effect of the chord and gap ratios on propulsion

The present study investigates the mechanisms of wake-induced flow dynamics in tandem National Advisory Committee for Aeronautics 0015 flapping foils at low Reynolds number of Re = 1100. A moving mesh arbitrary Lagrangian–Eulerian framework is utilized to realize the prescribed flapping motion of the foils while solving the flow via incompressible Navier–Stokes equations. The effect of the gap between the two foils on the thrust generation is studied for gaps of 1–10 times the chord of the downstream foil. The mean thrust as well as the propulsive efficiency vary periodically with the gap indicating alternate regions of higher and lower thrust generation, emphasizing the profound effect of upstream foil's wake interaction with the downstream foil. Five crucial wake–foil interactions leading to either favorable or unfavorable conditions for thrust generation are identified and different modes depending on the interactions are proposed for the tandem flapping foils. It is observed that the effect of the wake of the upstream foil on the downstream foil decreases with increasing gap. The study also focuses on the effect of the chord sizes of the upstream and the downstream foils on the propulsive forces, where the chord of the upstream foil is selected as 0.25–1 times the downstream foil's chord length. The effect of the chord size on the thrust is noticed to diminish as the chord size of the upstream foil decreases. Furthermore, the effect of the phase difference between the kinematics of the upstream and the downstream foils on flow dynamics is also explored along with its relationship with the chord sizes. For a fixed chord size, the effect of the phase difference on the propulsive performance is observed to be similar to that by varying the gap between the foils due to similar type of vortex interactions. The mechanisms of vortex interactions are linked to provide a comprehensive and generic understanding of the flow dynamics of tandem foils.

Numerical investigation into the effect of spacing on the flow-induced vibrations of two tandem circular cylinders at subcritical Reynolds numbers

Two-degree-of-freedom (2DOF) flow-induced vibrations (FIV) for a pair of elastically mounted circular cylinders in tandem arrangement with varying centre-to-centre spacings (Sx) are numerically studied. The Reynolds number range Re=1470–10320 belongs to the subcritical flow regime. Two identical cylinders with a mass ratio of m∗=2.6 and a mass-damping parameter of m∗+Caζ=0.013 are considered in the simulation. Four spacing ratios (Sx∕D, where D is the identical diameter) ranging from 3.0 to 8.0 are employed to investigate the effect of Sx∕D on the FIV responses, hydrodynamic characteristics and wake patterns of the two cylinders. It is found that the effect of the downstream cylinder on the FIV of the upstream one becomes insignificant when Sx∕D≥4.0. Due to the unsteady wake-cylinder interactions, multi-peak responses are observed for the downstream cylinder. Dual resonance with the 2:1 in-line to cross-flow oscillation frequency ratio and figure-eight orbital trajectories is found to occur for the upstream cylinder. In contrast, the trajectories of the downstream cylinder are rather irregular because of the low frequency components in the in-line response at high reduced velocity (Vr). Both shear flow and vortex shedding may appear in the gap region depending on Sx∕D and the relative motion of the two cylinders. In general, the vortex shedding modes of the upstream cylinder are similar to those of a single cylinder. Whereas, the analyses on the wake patterns suggest that the interactions of the upstream wake with the downstream cylinder and its own wake contribute to the unsteady fluid dynamics, which is crucial to maintaining the large-amplitude vibrations of the downstream cylinder at high Vr.

Wake interactions of two tandem floating offshore wind turbines: CFD analysis using actuator disc model

Floating offshore wind turbines (FOWTs) have received great attention for deep water wind energy harvesting. So far, research has been focused on a single floating rotor. However, for final deployment of FOWT farms, interactions of multiple FOWTs and potential impacts of the floating motion on power performance and wake of the rotors need to be investigated. In this study, we employ CFD coupled with an Actuator Disc model to analyze interactions of two tandem FOWTs for the scenario, where the upstream rotor is floating with a prescribed surge motion and the downstream rotor is fixed and influenced by the variations in the incoming flow created by the oscillating motion of the surging rotor. We will investigate three different surge amplitudes and analyze the fluctuations in power performance of the two rotors as well as their wake interactions. The results show a light increase in the mean power coefficient of both rotors for the surging case, compared against the case with no surge motion. The standard deviation of the transient CP of the surging rotor linearly scales with the surge amplitude, while such impact for the downstream rotor is very limited. Surging motion of the upstream rotor is found to enhance flow mixing in the wake, which therefore, accelerates the wake recovery of the downstream rotor. This finding suggests prospects for research into redesigning wind farm layout for FOWTs, aiming for more compact arrangements.

Interactions of wakes and shock waves with two-phase air/mist cooling in a transonic gas turbine stage

A 2-D two-phase numerical simulation was conducted to investigate the effect of interactions of moving wakes and shock waves on mist cooling performance over airfoils in a transonic gas turbine stage. The two-phase flow consists of a continuous phase (i.e., air) and a dispersed phase (i.e., mist). The tracking and evaporation of the mist are simulated by using the discrete phase model (DPM). The interactions between the droplets themselves with respect to collision and breakup were simulated by using the breakup and coalescence sub-models. The motion of the rotor domain was simulated by using the linear sliding mesh technique to study the transient stator-rotor interaction. The results show that the passing unsteady wakes caused by the blade rotation press the mist toward the blade surface, providing more enhanced film cooling effectiveness. The oblique shock wave was observed downstream of the vanes passage. The lambda shock wave was observed downstream of the blades passage. Both shock waves did not exert noticeable effect on the air/mist cooling performance. Injecting a 10% mist ratio noticeably improved the cooling enhancement by obtaining a maximum temperature reduction of 200 K and an average temperature reduction of 51 K on the vane, and a maximum of 350 K reduction and an average of 24 K reduction on the blade surface under the influence of wakes and shocks. Injecting the tiny water droplets increased the total pressure losses by 0.1% on the vane and 4% on the blade compared to the air cooling case. Injecting mist has negligible effect on the formations of shocks/wakes and their corresponding behaviors.