Computational Fluid Dynamics Predictions Research Articles

A Comparative Study of Performance of Low Reynolds Number Turbulence Models for Various Heat Transfer Enhancement Simulations

The goal of this study is to evaluate the computational fluid dynamic (CFD) predictions of friction factor and Nusselt number from six different low Reynolds number k–ε (LRKE) models namely Chang–Hsieh–Chen (CHC), Launder–Sharma (LS), Abid, Lam–Bremhorst (LB), Yang–Shih (YS), and Abe–Kondoh–Nagano (AKN) for various heat transfer enhancement applications. Standard and realizable k–ε (RKE) models with enhanced wall treatment (EWT) were also studied. CFD predictions of Nusselt number, Stanton number, and friction factor were compared with experimental data from literature. Various parameters such as effect of type of mesh element and grid resolution were also studied. It is recommended that a model, which predicts reasonably accurate values for both friction factor and Nusselt number, should be chosen over disparate models, which may predict either of these quantities more accurately. This is based on the performance evaluation criterion developed by Webb and Kim (2006, Principles of Enhanced Heat Transfer, 2nd ed., Taylor and Francis Group, pp. 1–72) for heat transfer enhancement. It was found that all LRKE models failed to predict friction factor and Nusselt number accurately (within 30%) for transverse rectangular ribs, whereas standard and RKE with EWT predicted friction factor and Nusselt number within 25%. Conversely, for transverse grooves, AKN, AKN/CHC, and LS (with modified constants) models accurately predicted (within 30%) both friction factor and Nusselt number for rectangular, circular, and trapezoidal grooves, respectively. In these cases, standard and RKE predictions were inaccurate and inconsistent. For longitudinal fins, Standard/RKE model, AKN, LS and Abid LRKE models gave the friction factor and Nusselt number predictions within 25%, with the AKN model being the most accurate.

Vortex Pump as Turbine—A Type Turbine for Energy Generation or Recovery Based on Computational Fluid Dynamics Prediction

An experimental vortex pump with a specific speed of 76 is investigated to get its performance and flow structure under noncavitation and cavitation conditions when the pump operates as turbine in the reverse direction by using computational fluid dynamics (CFD) method. A method is proposed to extract hydraulic, volumetric, and mechanical efficiencies for the first time. It is shown that a vortex pump can operate as turbine but it is subject to poor cavitation performance. The performance conversion factors of flow rate and head are 2.33 and 2.74 which are much larger than existing centrifugal pumps as turbine with the same specific speed. The conversion factor of efficiency is 0.98, which agrees with the conversion factor of efficiency for a centrifugal pump as turbine. There are a rope cavity and a vortex flow in the same rotational direction of the impeller. It is shown that flow structure is complex in the impeller in pump and turbine modes, particularly on the blade-to-blade surface, while static pressure profile in the volute and impeller as well as the space between the casing and the impeller is simple. The flow in the space between the impeller and the casing cannot be regarded as a forced vortex in both modes. The cavitation performance improvement and rope cavity control may be key issues in the future.

Investigation of hydrodynamic behavior in random packing using CFD simulation

Computational fluid dynamics (CFD) simulations of countercurrent gas–liquid flow in random packings of Raschig rings were carried out in this study. This model used gravity simulation to construct the random packing structure, and a volume expansion-recovery method to improve the meshing quality. A simple feedback control scheme was applied to control the gas inlet flow rate so that pressure drop can be estimated. The generated characteristics of the packing structure such as the number of packing elements, dry surface area and porosity were found to be close to experiments. CFD predictions of hydrodynamics properties are also validated by the experimental data using a small column section. The results indicate that our CFD model was able to capture the essential hydrodynamics behavior of the gas–liquid countercurrent flow. Hence, the approach presented in this study can be used as a basis for studying the effect of detailed packing-geometry design on hydrodynamic and mass transfer characteristics.

CFD predictions of Swirl burner aerodynamics with variable outlet configurations

Swirl stabilised combustion is one of the most widely used techniques for flame stabilisation in gas turbine combustors. Lean premixed combustion systems allow the reduction of NOx coupled with fair flame stability. The swirl mechanism produces an aerodynamic region known as central recirculation zone (CRZ) providing a low velocity region where the flame speed matches the flow velocity, thus anchoring the flame whilst serving to recycle heat and active chemical species to the root of the former. Another beneficial feature of the CRZ is the enhancement of the mixing in and around this region. However, the mixing and stabilisation processes inside of this zone have shown to be extremely complex. The level of swirl, burner outlet configuration and combustor expansion are very important variables that define the features of the CRZ. Therefore, in this paper swirling flame dynamics are investigated using computational fluid dynamics (CFD) with commercial software (ANSYS). A new generic swirl burner operated under lean-premixed conditions was modelled. A variety of nozzles were analysed using several gaseous blends at a constant power output. The investigation was based on recognising the size and strength of the central recirculation zones. The dimensions and turbulence of the Central Recirculation Zone were measured and correlated to previous experiments. The results show how the strength and size of the recirculation zone are highly influenced by the blend and infer that it is governed by both the shear layer surrounding the Central Recirculation Zones (CRZ) and the gas composition.

Analysis of local wear variables for high-precision erosion modelling in complex geometries

Particle-laden flows in complex geometries often require a more robust performance from erosion models in order to obtain accurate prediction of wear. Most erosion models developed over the last six decades have not been able to achieve the desired accuracy needed for these complex systems, primarily because they are based on single particle-wear material interactions, experimental correlations, and often do not capture the full physics of the erosion process. Recently, the capability of computational fluid dynamics (CFD) in resolving fluid-particle-wall interactions more realistically has been shown to have great potential in the development of high-performance erosion models, especially when combined with experimental data analysis. This paper adopts this combined CFD-experimental methodology to improve the prediction performance of some selected erosion models. Experimental data for the wear of an elbow in gas-solid flow from a previous study was combined with new CFD predictions of local wear variables such as particle impact angle, particle impact velocity, and particle mass rate. A geometric function is developed which can be combined with some common erosion models to significantly improve their wear prediction accuracy for gas-solid elbows. Also, the effects of target material surface roughness and particle rotation on local wear variables are investigated numerically. The simulation results reveal an increased dispersion of particles and a more even distribution of local wear variables at the elbow. In conclusion, this paper presents a method for improving performance of erosion models, and potentially a method to translate wear data between complex geometries.

Assessment of Computational Fluid Dynamics Capabilities for the Prediction of Three-Dimensional Separated Flows: The DELFT 372 Catamaran in Static Drift Conditions

In this paper, capabilities of state-of-the-art computational fluid dynamics (CFD) tools in the prediction of the flow-field around a multihull catamaran advancing in straight ahead motion at nonzero drift angles are investigated. CFD estimations have been provided by three research institutes by using their in-house codes: CNR-INM using Xnavis, IIHR using CFDShip-Iowa, and CNRS/ECN using ISIS. These allowed an in-depth comparison between different methodologies, such as structured overlapping grids versus unstructured grid, different turbulence models and detached eddy simulations (DES) approaches, and level-set (LS) versus volume of fluid (VoF). The activities were pursued within the NATO AVT-183 group “reliable prediction of separated flow onset and progression for air and sea vehicles,” aimed at the assessment of CFD predictions of large three-dimensional separated flows. Comparison between estimations is provided for both integral and local quantities, and for wave-induced vortices. Validation is reported by comparison against the available experimental fluid dynamics (EFD) data. Generally, all the simulations are able to capture the main features of the flow field; grid resolution effects are dominant in the onset phase of coherent structures and turbulence model affects the dynamic of the vortices. Hydrodynamic loads are in agreement between the submissions with standard deviation of about 3.5% for the resistance prediction and about 7% for lateral force and yaw moment estimation. Wave-induced vortices are correctly captured by both LS and VoF approaches, even if some differences have been highlighted, LS showing well-defined and long life vortices.

Application of Exactly Linearized Error Transport Equations to Sonic Boom Prediction Workshop

The computational fluid dynamics (CFD) prediction workshops sponsored by the AIAA have created invaluable opportunities to discuss the predictive capabilities of CFD in areas in which it has struggled, for example, sonic boom prediction. While there are many factors that contribute to disagreement between simulated and experimental results, such as modeling or discretization errors, quantifying the errors contained in a simulation is important for those who make decisions based on the computational results. The linearized error transport equations (ETE) combined with a truncation error estimate is a method to quantify one source of error. The ETE are implemented with a complex-step method to provide an exact linearization with minimal source code modifications to CFD and multidisciplinary analysis methods including atmospheric propagation of sonic boom signatures. Uniformly refined grids from the 2nd AIAA Sonic Boom Prediction Workshop demonstrate the utility of the linearized ETE for multidisciplinary analysis, capturing the general trends of the discretization error when flow features are resolved while also demonstrating issues related to error prediction near strong shocks or when under-resolved flow features are present.

Three-Dimensional Computational Fluid Dynamics Prediction of Turbocharger Centrifugal Compression System Instabilities

The present work combines experimental measurements and unsteady, three-dimensional computational fluid dynamics predictions to gain further insight into the complex flow-field within an automotive turbocharger centrifugal compressor. Flow separation from the suction surface of the main impeller blades first occurs in the mid-flow range, resulting in local flow reversal near the periphery, with the severity increasing with decreasing flow rate. This flow reversal improves leading-edge incidence over the remainder of the annulus, due to (a) reduction of cross-sectional area of forward flow, which increases the axial velocity, and (b) prewhirl in the direction of impeller rotation, as a portion of the tangential velocity of the reversed flow is maintained when it mixes with the core flow and transitions to the forward direction. As the compressor operating point enters the region where the slope of the constant speed compressor characteristic (pressure ratio versus mass flow rate) becomes positive, rotating stall cells appear near the shroud side diffuser wall. The angular propagation speed of the diffuser rotating stall cells is approximately 20% of the shaft speed, generating pressure fluctuations near 20% and 50% of the shaft frequency, which were also experimentally observed. For the present compressor and rotational speed, flow losses associated with diffuser rotating stall are likely the key contributor to increasing the slope of the constant speed compressor performance curve to a positive value, promoting the conditions required for surge instabilities. The present mild surge predictions agree well with the measurements, reproducing the amplitude and period of compressor outlet pressure fluctuations.

Numerical probing of suspended lactose droplet drying experiment

Single droplet drying (SDD) device has been extensively used to measure drying kinetics of droplets of 0.5–2 mm initial diameter. Despite the large size, it has deemed to be the most practical for such purposes in the past 40 years. There is a surplus of numerical investigations of SDD in the literature. However, this is the first time detailed computational fluid dynamics (CFD) simulations were carried out on the actual fluid behaviour inside and around a lactose solution droplet in SDD by glass suspension experiment. The full set of the governing equations were solved and the fluid flow was investigated. A lactose concentration gradient was developed within the droplet due to momentum transfer and water removal. The CFD predictions of lactose concentrations could be used to predict the formation of crust or crystallization in the droplet. Furthermore, accumulation of solute within the droplet indicated the tendency to form solid structure. The simulated overall drying rate curve compared well with the available laboratory data. The predicted temperature results have also been benchmarked against the experimental measurements generated from the thermal history of lactose droplet drying. More importantly, CFD simulations have been extended to similar small droplet sizes occurring during spray drying, which are experimentally inaccessible with SDD. These analyses are relevant to spray drying to validate simpler 1D models.

Computational Fluid Dynamics (CFD) Simulations and Experimental Measurements in an Inductively-Coupled Plasma Generator Operating at Atmospheric Pressure: Performance Analysis and Parametric Study

In this article, electrical characteristics of a high-power inductively-coupled plasma (ICP) torch operating at 3 MHz are determined by direct measurement of radio-frequency (RF) current and voltage together with energy balance in the system. The variation of impedance with two parameters, namely the input power and the sheath gas flow rate for a 50 kW ICP is studied. The ICP torch system is operated at near atmospheric pressure with argon as plasma gas. It is observed that the plasma resistance increases with an increase in the RF-power. Further, the torch inductance decreases with an increase in the RF-power. In addition, plasma resistance and torch inductance decrease with an increase in the sheath gas flow rate. The oscillator efficiency of the ICP system ranges from 40% to 80% with the variation of the Direct current (DC) powers. ICP has also been numerically simulated using Computational Fluid Dynamics (CFD) to predict the impedance profile. A good agreement was found between the CFD predictions and the impedance experimental data published in the literature.

Experimental and CFD investigation of overall heat transfer coefficient of finned tube CO2 gas coolers

The overall heat transfer coefficient of two CO2 gas coolers was investigated through experiment and Computational Fluid Dynamics (CFD). The CFD modelling provided prediction accuracy for the overall heat transfer coefficient with a maximum error of 9% compared to the CFD predictions. Comparing the two gas cooler designs, and from the experimental and modelling results it has been shown that the performance of the gas cooler can be improved by up to 20% through optimization of the circuit design of the gas cooler. A horizontal slit between the 1st and 2nd row of tubes of the gas cooler can increase the overall heat transfer coefficient by 8% compared with the a fin without the slit.

CFD and kinetic modelling study of methane MILD combustion in O2/N2, O2/CO2 and O2/H2O atmospheres

To deepen the understanding of combining moderate or intense low-oxygen dilution (MILD) combustion with oxy-fuel combustion for enhancing flame stability while realizing carbon capturing and storage, this paper presents a numerical study of methane MILD combustion in three atmospheres, i.e.: O2/N2, O2/CO2 and O2/H2O, with both computational fluid dynamics (CFD) and kinetic calculation approaches. Firstly, CFD predictions for the three conditions were performed following a systematic validation of the numerical method against experimental measurement from methane/air MILD combustion in a laboratory-scale closed furnace. Subsequently, kinetic calculations with a well-stirred reactor model was used to quantitatively identify the operating ranges of MILD combustion in the three atmospheres for methane. Moreover, the kinetic calculation provided additional insight into the fuel oxidation pathway. The results reveal that replacing N2 with either CO2 or H2O would help to establish MILD combustion mode from the viewpoint of lower temperature increase, due to both physical and chemical property discrepancies among the diluents. Specifically, the chemical effect and physical effect are responsible to the lower temperature rise for CO2-diluted case and H2O-diluted case, respectively. Inside the MILD combustion furnace, the negative heat release region disappears in regardless of atmospheres, indicating the eliminated fuel pyrolysis process under MILD combustion mode. Detailed analysis of the flame structure suggests that the combustion regimes inside the furnace in the three atmospheres are all in well-stirred combustion regime, and CO2-diluted case has the most extended reaction zone. Kinetic calculation indicates that CO2 or H2O dilution would result in a wider MILD combustion operating range compared to N2 dilution, while it is more pronounced for CO2. These observations all imply that MILD combustion will be more easily established with CO2 dilution than N2 or H2O dilution. However, higher CO formation is obtained in O2/CO2, forcing more attention to be paid on CO emission under CO2-diluted MILD combustion. Furthermore, the hydrocarbon recombination route is negligible under MILD combustion in spite of the atmospheres, implying lower sooting tendency as compared with conventional combustion.

Parametric analysis on the performance of flat plate collector with transparent insulation material

Abstract The transparent insulation materials (TIM) can effectively improve the performance of flat plate solar collector in cold weather. A three dimension numerical model of flat plate collector with TIM has been developed in this paper. The computational fluid dynamics (CFD) have been used to simulate the model. The Renormalization-group (RNG) k-e model and Discrete Ordinates (DO) radiation model were adopted. The influences of the environment conditions, mass flow rate, tilt angle and transmittance on the performance of the collector with TIM were analyzed. A good agreement was achieved between the CFD prediction and the previous experiment. The result shows that the collector with TIM is more efficient, when ambient temperature is low. For various wind speeds, the new collector's efficiency has a slightly change. The transmittance of TIM is a key parameter to achieve high performance for the collector. When the transmittance is below 80%, the collector with TIM has no the advantage of being good value. The optimum mass flow rate is 0.06 kg/s under corresponding conditions. The tilt angle of the collector with TIM has less effect compared with the conventional one.

Solid residence time distribution in a cross-flow dense fluidized bed with baffles

The residence time distribution (RTD) of particles in a gas-solid dense fluidized bed with a continuous solid flow operation and baffles needs much more focus for the purpose of the wide industrial applications. The available models of solid RTD are not adequate in this case due to the additional convective diffusion induced by the cross-flow of the solid feeding and the complex geometry caused by the baffles. To address this problem, this work applied a two-phase Eulerian-Eulerian model combined with the species transport equation to predict solid RTD in a dense fluidized bed. The effects of the continuous solid feeding and baffles were considered. The solid dispersion coefficient Ds in the species transport equation was calculated by an analytical solution from kinetic theory of granular flow. Ds only needs the value at a molecular level due to the fact that the computational fluid dynamics (CFD) model is able to reproduce the RTD procedure exactly same as the practical experiments. To validate the established CFD model, a series of 3D lab-scale cold flow experiments were conducted in the free and baffled beds for the bed material with various severe non-spherical shapes. The measurement included the solid hydrodynamic characteristics at the outlet of the outflow pipe and solid RTD of the system. The reasonable agreement between the CFD prediction and experimental data demonstrated the good performance of the CFD model. 1D plug flow with dispersion model and the tanks-in-series model were further used to fit the calculated RTD curves. The estimated lateral dispersion coefficient of solids locates in a rational range compared with the data collected extensively from the literature. The results showed that the lateral dispersion coefficient of solids decreases when the baffles are installed.

Experimental Validation of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles

Successful implementation of sCO2 power cycles requires high compressor efficiency at both the design-point and over a wide operating range in order to maximize cycle power output and maintain stable operation over a wide range of transient and part-load operating conditions. This requirement is particularly true for air-cooled cycles where compressor inlet density is a strong function of inlet temperature that is subject to daily and seasonal variations as well as transient events. In order to meet these requirements, a novel centrifugal compressor stage design was developed that incorporates multiple novel range extension features, including a passive recirculating casing treatment and semi-open impeller design. This design, presented and analyzed for CO2 operation in a previous paper, was fabricated via direct metal laser sintering and tested in an open-loop test rig in order to validate simulation results and the effectiveness of the casing treatment configuration. Predicted performance curves in air and CO2 conditions are compared, resulting in a reduced diffuser width requirement for the air test in order to match design velocities and demonstrate the casing treatment. Test results show that the casing treatment performance generally matched computational fluid dynamics (CFD) predictions, demonstrating an operating range of 69% and efficiency above air predictions across the entire map. The casing treatment configuration demonstrated improvements over the solid wall configuration in stage performance and flow characteristics at low flows, resulting in an effective 14% increase in operating range with a 0.5-point efficiency penalty. The test results are also compared to a traditional fully shrouded impeller with the same flow coefficient and similar head coefficient, showing a 42% range improvement over traditional designs.

Numerical simulation of container ship in oblique winds to develop a wind resistance model based on statistical data

ABSTRACTThe forces that wind exerts on a merchant ship, especially for a container ship that carries high stacks of cargo on board, can be very large; therefore, more accurate simulations than presently available in the literature on the aerodynamics of a container ship are necessary for a safe and efficient shipping. This research tries to demonstrate a newer level of accuracy in capturing the aerodynamic properties of a typical full-stack container ship. Simulations setup was verified against US National Advisory Committee for Aeronautics (NACA) test data for the Akron airship. These are unique data that can verify the accuracy of the Computational Fluid Dynamics (CFD) prediction for pressure distributions over a three-dimensional (3D) object in nonzero wind angles. The numerical simulations of the container ship, which have been performed by ANSYS-CFX™, focus on wind angles of attack (AOAs) up to 40°, obtained from a voyage data record of a container ship throughout a rather long voyage. A regression equation for air resistance is derived within this range, and a set of voyage data for wind speed and directions is also analyzed to check the applicability of the results. Innovative features of air–sea interface modeling have been included in this report.

Loss Reduction in a 1.5 Stage Axial Turbine by Computer-Driven Stator Hub Contouring

Improvements in stage isentropic efficiency and reductions in total pressure loss are sought in a 1.5 stage axial turbine. This is representative of power generation equipment used in thermal power cycles, which delivers about 80% of the 20 × 1012 kWh world-wide electricity. Component-level improvements are therefore timely and important toward achieving carbon dioxide global emission targets. Secondary flow loss reduction is sought by applying a nonaxisymmetric endwall design to the turbine stator hub. A guide groove directs the pressure side branch of the horseshoe vortex away from the airfoil suction side, using a parametric endwall hub surface, which is defined as to obtain first-order smooth boundary connections to the remainder of the passage geometry. This delays the onset of the passage vortex and reduces its associated loss. The Automatic Process and Optimization Workbench (apow) generates a Kriging surrogate model from a set of Reynolds-averaged Navier–Stokes simulations, which is used to optimize the hub surface. The three-dimensional steady Reynolds-averaged Navier–Stokes model with an axisymmetric hub is validated against reference experimental measurements from the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen. Comparative computational fluid dynamics (CFD) predictions with an optimized nonaxisymmetric hub show a decrease in the total pressure loss coefficient and an increase in the isentropic stage efficiency at and off design conditions.

Fire Smoke Transport and Opacity Reduced-Order Model (Fire-STORM): A New Computer Model for High-Rise Fire Smoke Simulations

The problem of smoke spread through elevator shafts in high rise buildings is analyzed theoretically and numerically in this paper. While experiments and computational fluid dynamics (CFD) models have been used for such exercises, there is a need for fast reduced-order models for such scenarios. Towards this goal, a transient network model called High-rise fire smoke transport and opacity reduced-order model (Fire-STORM) was developed to investigate heat and mass transfer through the elevator shaft during fires. The model numerically solves the coupled set of differential equations of the fire floor in conjunction with the steady state conservation equations of the elevator shaft. The model is validated in two stages. First, the stack effect in a non-fire scenario is analyzed. Pressure differences through exterior doors and elevator doors are compared with experimental data available in the literature and results of a computational fluid dynamics tool. Then, a first-floor fire scenario is considered for the same high-rise building in four different cases which are combinations of different building tightness and ambient temperatures. The results are compared with CFD simulations. For the four different building envelope and ambient thermal conditions, the soot mass fractions and optical visibilities were calculated and compared to CFD predictions. Overall, Fire-STORM is a simple and fast tool to model the evolution of heat and mass transfer in a high-rise building affected by fire. While Fire-STORM is excellent in predicting transient smoke transport for buildings with loose envelopes, it should be used with caution for buildings with tight envelopes since the errors for these cases are relatively high. Despite this, the relative computational speed difference between Fire-STORM and the CFD model highlights the utility of a reduced-order model for firefighter decision making and building control system design.

Cooling Effectiveness for a Shaped Film Cooling Hole at a Range of Compound Angles

Shaped film cooling holes are a well-established cooling technique used in gas turbines to keep component metal temperatures in an acceptable range. One of the goals of film cooling is to reduce the driving temperature for convection at the wall, the success of which is generally represented by the film cooling adiabatic effectiveness. However, the introduction of a film cooling jet-in-crossflow, especially if it is oriented at a compound angle, can augment the convective heat transfer coefficient and dominate the flowfield. This work aims to understand the effect that a compound angle has on the flowfield and adiabatic effectiveness of a shaped film cooling hole. Five orientations of the public 7–7–7 shaped film cooling hole were tested, from a streamwise-oriented hole (0 deg compound angle) to a 60 deg compound angle hole, in increments of 15 deg. Additionally, two pitchwise spacings of P/D = 3 and 6 were tested to examine the effect of hole-to-hole interaction. All cases were tested at a density ratio of 1.2 and blowing ratios ranging from 1.0 to 4.0. The experimental results show that increasing compound angle leads to increased lateral spread of coolant and enables higher laterally averaged effectiveness at high-blowing ratios. A smaller pitchwise spacing leads to more complete coverage of the endwall and has higher laterally averaged effectiveness even when normalized by coverage ratio, suggesting that hole to hole interaction is important for compound angled holes. Steady Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) was not able to capture the exact effectiveness levels, but did predict many of the observed trends. The lateral motion of the coolant jet was also quantified, both from the experimental data and the CFD prediction, and as expected, holes with a higher compound angle and higher blowing ratio have greater lateral motion, which generally also promotes hole-to-hole interaction.

Experimental Study of Periodic Free Stream Unsteadiness Effects on Discrete Hole Film Cooling in Two Geometries

Discrete hole film cooling is widely employed to protect turbine blades and vanes from hot combustion gases entering the high-pressure turbine stage. Accurate prediction of the heat transfer near film cooling holes is critical, and high-fidelity experimental data sets are needed for validation of new computational models. Relatively few studies have examined the effects of periodic main flow unsteadiness resulting from the interaction of turbine blades and vanes, with a particular lack of data for shaped hole configurations. Periodic unsteadiness was generated in the main flow over a laidback, fan-shaped cooling hole at a Strouhal number (St = fD/U) of 0.014 by an airfoil oscillating in pitch. Magnetic resonance imaging (MRI) with water as the working fluid was used to obtain full-field, phase-resolved velocity and scalar concentration data. Operating conditions consisted of a hole Reynolds number of 2900, channel Reynolds number of 25, 000, and blowing ratio of unity. Both mean and phase-resolved data are compared to the previous measurements for the same hole geometry with steady main flow. Under unsteady freestream conditions, the flow separation pattern inside the hole was observed to change from an asymmetric separation bubble to two symmetric bubbles. The periodic unsteadiness was characterized by alternating periods of slow main flow, which allowed the coolant to penetrate into the freestream along the centerplane, and fast, hole-impinging main flow, which deflected coolant toward the laidback wall and caused ejection of coolant from the hole away from the centerplane. Mean adiabatic surface effectiveness was reduced up to 23% inside the hole, while mean laterally averaged effectiveness outside the hole fell 28–36% over the entire measurement domain. A brief comparison to a round jet with and without unsteadiness is included; for the round jet, no disturbance was observed inside the hole, and some fluctuations directed coolant toward the wall, which increased mean film cooling effectiveness. The combined velocity and concentration data for both cases are suitable for quantitative validation of computational fluid dynamics predictions for film cooling flows with periodic freestream unsteadiness.