Detached Eddy Simulation Model Research Articles

O-008. Influence of Hypertension in Pregnancy on Hematological Phenotypes of Preterm Infants with Gestational Age Inferior to 32 Weeks

This paper presents validation studies to simulate performance, cavitation and cavitation erosion properties of the King's College (KCD) KCD-193 model propeller. The simulations are performed to investigate the effect of wake on the cavitation formation and the cavitation erosion intensity. The numerical (CFD) study is achieved by using unsteady Reynolds Averaged Navier-Stokes (RANS) and Detached Eddy Simulation (DES) techniques with SST (Menter) k-ω turbulence model. The Schnerr-Sauer cavitation model and Eulerian approach with the Volume of Fluid (VOF) multiphase model are used to model a two-phase cavitation flow. The sliding mesh technique is applied to simulate the rotation of the propeller, and particular mesh refinement is performed on the regions where cavitation development is observed. Erosion intensity values on the propeller surface are obtained by Erosive Power Method (EPM) approach, and erosion formation on the blades is illustrated by utilizing the erosion intensity dataset. Numerical comparison for the erosion intensity values using RANS and DES models is carried out to evaluate the effect of wake in behind condition. Numerical results are evaluated against cavitation tunnel measurements at the Emerson Cavitation Tunnel (ECT) of Newcastle University. The main objectives of the study are to obtain the cavitation and cavitation erosion formation on the propeller in good agreement with experimental data obtained in ECT and to investigate the characteristics of the erosion intensity subject to cavitation conditions. In view of the flow conditions investigated, the RANS model is also found appropriate and required less computing efforts to predict the erosion intensity than the DES model. The results confirm the EPM method is to be compatible in predicting the erosion intensity. The results of the simulations indicate that a decrease in cavitation number does not necessarily cause an increase in the erosion intensity, requiring further investigation.

Evaluation of Shear Stress Transport, Large Eddy Simulation and Detached Eddy Simulation for the Flow around a Statically Loaded Tire

To select a more suitable turbulence model to study tire aerodynamics, the characteristics of a deformed profile of a 185/65 R14 passenger tire were reproduced using 3D printing technology. Based on the distance from automobile chassis to the ground, a partially loaded tire model with a height of 150 mm was selected in this paper, and the surface pressure coefficient of the tire model was determined using a wind tunnel test. A computational fluid dynamics (CFD) model was established according to the tire wind tunnel test. The surface pressure coefficient results of three turbulence models, shear stress transport (SST) k-ω, large eddy simulation (LES), and detached eddy simulation (DES) were obtained. Compared with the wind tunnel test results, the mean relative errors of the surface pressure coefficients predicted using SST, LES, and DES in the longitudinal section were 22.4%, 20.9%, and 14.8%, respectively. The LES and DES can capture details of the unsteady flow field that were not predicted by SST. By synthetically analyzing the results of the surface pressure coefficient and flow fields, the DES model is more advantageous than the other two models in predicting the flow characteristics around a statically loaded tire. This study can help designers in the tire industry to apply these cost-effective tools for minimizing the aerodynamic drag of a new tire design.

Performance Prediction of a Hard-Chine Planing Hull by Employing Different CFD Models

This paper presents CFD (Computational Fluid Dynamics) simulations of the performance of a planing hull in a calm-water condition, aiming to evaluate similarities and differences between results of different CFD models. The key differences between these models are the ways they use to compute the turbulent flow and simulate the motion of the vessel. The planing motion of a vessel on water leads to a strong turbulent fluid flow motion, and the movement of the vessel from its initial position can be relatively significant, which makes the simulation of the problem challenging. Two different frameworks including k-ε and DES (Detached Eddy Simulation) methods are employed to model the turbulence behavior of the fluid motion of the air–water flow around the boat. Vertical motions of the rigid solid body in the fluid domain, which eventually converge to steady linear and angular displacements, are numerically modeled by using two approaches, including morphing and overset techniques. All simulations are performed with a similar mesh structure which allows us to evaluate the differences between results of the applied mesh motions in terms of computation of turbulent air–water flow around the vessel. Through quantitative comparisons, the morphing technique has been seen to result in smaller errors in the prediction of the running trim angle at high speeds. Numerical observations suggest that a DES model can modify the accuracy of the morphing mesh simulations in the prediction of the trim angle, especially at high-speeds. The DES model has been seen to increase the accuracy of the model in the computation of the resistance of the vessel in a high-speed operation, as well. This better level of accuracy in the prediction of resistance is a result of the calculation of the turbulent eddies emerging in the water flow in the downstream zone, which are not captured when a k-ε framework is employed. The morphing approach itself can also increase the accuracy of the resistance prediction. The overset method, however, overpredicts the resistance force. This overprediction is caused by the larger vorticity, computed in the direction of the waves, generated under the bow of the vessel. Furthermore, the overset technique is observed to result in larger hydrodynamic pressure on the stagnation line, which is linked to the greater trim angle, predicted by this approach. The DES model is seen to result in extra-damping of the second and third crests of transom waves as it calculates the stronger eddies in the wake of the boat. Overall, a combination of the morphing and DES models is recommended to be used for CFD modeling of a planing hull at high-speeds. This combined CFD model might be relatively slower in terms of computational time, but it provides a greater level of accuracy in the performance prediction, and can predict the energy damping, developed in the surrounding water. Finally, the results of the present paper demonstrate that a better level of accuracy in the performance prediction of the vessel might also be achieved when an overset mesh motion is used. This can be attained in future by modifying the mesh structure in such a way that vorticity is not overpredicted and the generated eddies, emerging when a DES model is employed, are captured properly.

THREE-DIMENSIONAL NUMERICAL ANALYSIS OF STAGGERED GROINS

Mahmuzlar, kıyıda katı madde hareketini engelleyerek, kıyıların mevcut durumunu korumak üzere inşa edilirler. Dalga hareketlerinin mevsimsel farklılık göstermesi, kıyıların değişimine neden olabilmektedir. Kıyıları korumak adına inşa edilen mahmuzlarla etkileşim halinde olan akımın hareketinin analiz edilmesi, kıyıların korunması açısından alınacak önemleri daha etkili kılacaktır. Bu çalışmada, farklı akım durumlarında deneysel olarak incelenen şaşırtmalı mahmuzların üç boyutlu sayısal modellemesi yapılmıştır. Sayısal modellemelerde, akımın hareketini tanımlayan, Navier Stokes ve süreklilik denklemleri, sonlu hacimler yöntemi kullanılarak çözülmüştür. Sayısal modellemelerde, türbülans viskozitesinin hesabında, Ayrılmış Girdap Simülasyon (Detached Eddy Simulation-DES) modeli ve su-hava arakesitinin belirlenmesinde ise akışkan hacimleri yöntemi kullanılmıştır. DES modeli kullanılarak elde edilen sayısal model sonuçları deneysel bulgularla karşılaştırılmış ve karşılaştırma sonucunda sayısal model sonuçlarının deneysel bulgularla oldukça uyumlu olduğu görülmüştür. Sonuç olarak, sayısal modelleme tekniklerinin şaşırtmalı mahmuz yapılarıyla etkileşimde bulunan akım problemlerinin çözümünde başarılı olduğu, farklı akım ve yapı koşullarında tekrar edilebilme imkânı sunmasından dolayı tercih edilebileceği belirlenmiştir.

Adaptive detached eddy simulation of transition under the influence of free-stream turbulence and pressure gradient

Abstract

Computational analysis of gas–liquid flow in an idealised CANDU reactor header under conditions that are relevant to small-break loss-of-coolant and loss-of-flow accidents

Extensive numerical simulations of isothermal air/water flow in an idealised model of the header/feeder system of a CANDU nuclear reactor were performed under conditions that are relevant to postulated loss-of-flow accidents (LOFA) and small-break loss-of-coolant accidents (SBLOCA). Following our recent work, in which the present CFD methodology was validated against in–house experimental results, we used the volume of fluid method to solve the system of multi-phase flow governing equations and the detached eddy simulation model to close this system in turbulent flow. We computed the steady-state liquid flow distribution to the different feeders for different combinations of inlet water and air mass flow rates and different mass extraction rates, namely, values of the ratio of the leak liquid mass flow rate and the inlet liquid mass flow rate, and found that, in general, this distribution tends to become more uniform as the inlet flow rate of either the liquid or the gas increases. A “free surface” separating air above from an air–water mixture below was observed in many cases, generally moving downward with decreasing inlet flow rates and increasing mass extraction ratio. The liquid distribution to non-leaking feeders was not affected significantly by a change in the location of the leak. Time histories of flow properties following a step change in boundary conditions showed that the change of flow rate through each feeder can be represented by a first-order model with a time constant of roughly 1 s. As part of the validation of the present CFD analysis, the computed local pressure loss coefficient for a leaking feeder was found to be in excellent agreement with previously published experimental results. The static pressure loss across the header, estimated from available semi-empirical two-phase flows models was, in most cases, found to be within 10% of the CFD solution.

Turbulence Modeling a Review for Different Used Methods

This contribution represents a critical view of the advantages and limits of the set of mathematical models of the physical phenomena of turbulence. Turbulence models can be grouped into two categories, depending on how turbulent quantities are calculated: direct numerical simulations (DNS) and RANS (Reynolds Averaged Navier-Stokes Equations) models. The disadvantage of these models is that they require enormous computing power, inaccessible, especially for large and complicated geometries. For this reason, hybrid models (combinations between DNS and RANS methods) have been developed, for example, the LES (“Large Eddy Simulation”) or DES (“Detached Eddy Simulation”) models. They represent a compromise - are less precise than DNS, but more precise than RANS models. The results presented in this contribution will allow and facilitate future research in the field the choice of the model approach necessary for the case studies whatever their difficulty factor.

Comparison of hydrodynamic performance and wake vortices of two typical types of pumpjet propulsor

Pumpjet propulsor (PJP) is widely used in various underwater vehicles recently. Two types of PJP, the stator-rotor PJP (the rotor is behind the stator) and the rotor-stator PJP (the rotor is in front of the stator), are designed to investigate the difference of the hydrodynamic performance between those two PJPs. Numerical simulations based on the Improved Delayed Detached Eddy Simulation (IDDES) model are carried out. Results show that the rotor-stator PJP has a better balanced torque character than that of the stator-rotor PJP. In addition, the characteristic frequency of unsteady forces acting on each rotor blade is the stator blade passage frequency and its harmonics, while that of each stator blade is the rotor blade passage frequency and its harmonics. The wake vortex structure and the evolution mechanism of both PJPs are discussed and compared. Spiral precession and double-helix breakdown of hub vortex are observed for the stator-rotor PJP. The roll-up process of rotor blade trailing edge vortex sheet for both PJPs is discussed. The short-wave instability and the mutual-inductance instability of tip vortices for PJPs are discussed. The instability of tip and hub vortices of the rotor-stator PJP is more likely to occur.

Numerical simulation of rotating channel flow based on a modified DES model

A new type of nonlinear sub-grid scale (SGS) model is adopted based on the helicity analysis and is verified by predicting the internal flow in a rotating channel. A stress term that contains helicity constraint is introduced into the original SGS model to construct a nonlinear sub-grid model. This additional term representing the helicity constraint effect in the momentum equations is shown to give predictions that are in better agreement with the experimental data. In this paper, the Detached-Eddy Simulation (DES) and the nonlinear SGS model are used to further study the turbulence statistics of the rotating channel flow. Combining with the Reynolds stress transport equations and the turbulent kinetic energy transport equation, the change of turbulence statistics near the wall of the rotating channel is analyzed. The newly added term changes the turbulent viscosity near the wall, which changes the velocity gradient near the wall and further affects other turbulence statistics near the wall.

Comparative Study on CFD Turbulence Models for the Flow Field in Air Cooled Radiator

This paper compares the performances of three Computational Fluid Dynamics (CFD) turbulence models, Reynolds Average Navier-Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for simulating the flow field of a wheel loader engine compartment. The distributions of pressure fields, velocity fields, and vortex structures in a hybrid-grided engine compartment model are analyzed. The result reveals that the LES and DES can capture the detachment and breakage of the trailing edge more abundantly and meticulously than RANS. Additionally, by comparing the relevant calculation time, the feasibility of the DES model is proved to simulate the three-dimensional unsteady flow of engine compartment efficiently and accurately. This paper aims to provide a guiding idea for simulating the transient flow field in the engine compartment, which could serve as a theoretical basis for optimizing and improving the layout of the components of the engine compartment.

Experimental and numerical investigations of heat transfer and fluid flow in a rectangular channel with perforated ribs

The present work concentrates on perforated 90° ribs to improve the thermal performances in a rectangular cooling channel with an aspect ratio of 4:1. Three different types of perforated ribbed channels are designed and compared. Steady-state Liquid Crystal Thermography (LCT) is employed to measure surface temperature and derive heat transfer coefficients over the ribbed surfaces in the tested channels. The turbulent flow details are presented by numerical calculations with two established turbulence model, i.e., the k-ω SST (Shear Stress Transportation) model and the DES (Detached Eddy Simulation) model. Compared with the normal rib (Case 1), the low heat transfer behind the ribs is improved by the perforated ribs with slightly reduced pressure drop. This phenomenon is more obvious when the perforated ratio is larger (Case 4). The local heat transfer is enhanced by about 12%–24% and the overall heat transfer is enhanced by about 4%–8%. The overall thermal performance is also improved by the perforated ribs with a slightly reduced pressure drop. The recirculating flows behind the ribs are reduced by the perforated cases. The reduced recirculation flows enhance the local heat transfer in this region. However, the flow reattachment region is disturbed by the perforated ribs and the local heat transfer in this region is slightly decreased. As a perforated rib can improve the overall thermal performance and provide more uniform heat transfer fields, it is promising for applications in internal cooling of turbine blades.

Unsteady aerodynamics analysis and modelling of a Slingsby Firefly aircraft: Detached-Eddy Simulation model and flight test validation

This paper presents unsteady stall characteristics of a Slingsby T67M260 Firefly light aircraft from both a computational fluid dynamics (CFD) half model and flight tests. Initial results from the steady CFD, based on a RANS k−ω SST turbulence model, established the critical angle of attack of the stall to be αstall=16∘, with a maximum lift coefficient of CLmax=1.2. Comparisons with straight and level flight test data were comparable up to α=12∘ – 14∘, with the increasing deviation at higher α attributed to the effect of the propeller slipstream under these flight conditions. The RANS CFD model was then extended to an unsteady Detached-Eddy Simulation (DES) model for three angles of attack at pre-stall and stall condition (α=14∘, 16∘, 18∘), with analysis of the vortex shedding frequency. Further comparisons were then made with flight test data taken using on-board accelerometers and wing tuft surface flow visualization, at a stalled condition at equivalent α. These unsteady CFD data established a dominant shedding frequency ranging from 11.7 Hz – 8.74 Hz with increasing α and a Strouhal number based on wing chord of St = 0.11, which when compared to flight test accelerometer spectra matched within 2.9% of the measured frequency.

Detached Eddy Simulation of syngas combustion in a reverse-flow configuration

The combustion of low calorific value syngas in a 3.3-kW reverse-flow chamber under moderate or intense low-oxygen dilution (MILD) (global equivalence ratio Φglobal = 0.89) and ultra-lean (Φglobal = 0.32) conditions have been numerically investigated with detailed chemistry. Reynolds averaged Navier Stokes (RANS)/Detached eddy simulation (DES) models for flow and Eddy dissipation concept (EDC)/Flamelet generated manifold (FGM) models for combustion have been used. Quantitative measurements of temperature, OH radical, and CO emissions performed in the same combustor are used to validate and compare the models. The prediction of the minor species OH is a special focus of the present study. The fields of velocity, mixture fraction, and kinetic parameters have been investigated in detail. The DES-EDC model performs the best in predicting the scalar distributions, although the computational cost is highest. The RANS model predicts insufficient mixing and higher velocities leading to a delayed reaction zone. The FGM model consistently predicts early ignition that has been attributed to the lack of a suitable progress variable and the use of the diffusion flamelet to represent the thermochemistry. However, the FGM model is promising with suitable modifications due to the low computational cost. The present study also provides a comprehensive dataset in a reverse-flow chamber operating under MILD and ultra-lean conditions for validation of numerical models.

Research on wind buffeting noise characteristics of a vehicle based on ILRN and DES-ILRN methods

In view of the unsatisfactory calculation accuracy of common turbulence models, two improved models, called improved low-Reynolds number (ILRN) k− ε and Detached EddySimulation (DES)-ILRN are proposed. Basing on the low-Reynolds number (LRN k− ε) turbulence model in this paper, revised concepts include the introduction of turbulence time scale, eddy viscosity coefficient limitation concept and separation perception model. Otherwise, the DES model is improved by introducing the ILRN model. The accuracy of the two models is validated through wind tunnel test. Then, the wind buffeting noise from rear windows is received by ILRN and DES-ILRN turbulence models, and the obtained results are compared with the road test. The accuracy of ILRN and DES-ILRN turbulence models in calculating wind buffeting noise of a real vehicle is validated by experiment. ILRN and DES-ILRN models are applied to research the wind buffeting noise, and good calculation results are obtained. They are promising methods to solve wind buffeting noise problems.

Research and Application of Filtering Grid Scale in Detached Eddy Simulation Model

The existing definition method of filter grid scale in a Detached Eddy Simulation (DES) hybrid model is unreasonable, which will lead to the unreasonable trigger of a boundary layer large eddy simulation and reduce computational efficiency. In view of this problem, the filter grid scale is discussed in this paper. The 90° square curved elbow is selected as the research object. The effects of three grid definition methods: geometric mean (ΔGM), arithmetic mean (ΔAM) and quadratic mean (ΔQM) on the simulation results of the DES model are compared, and the velocity distribution of the flow cross section and the distribution of the flow pressure coefficient on the outer arc surface are compared with the experimental results of Taylor. The results show that the order of the three definition methods is ΔGM≤ΔAM≤ΔQM. Meanwhile, within 30° < polar angle(θ) < 75°, the results are closer to the experiment, and the development trends and numerical values of ΔAM and ΔQM are closer to the experiment in general. However, when θ > 60°, the value of ΔQM is slightly closer to the experimental result than ΔAM. ΔQM is more suitable for calculating the internal flow in a curved elbow than the other two methods.

Improved Delayed Detached Eddy Simulation of Compressor Cascade Tip Leakage Flow

An Improved Delayed Detached Eddy Simulation (IDDES) model as a kind of hybrid RANS/LES approach has been developed and applied to calculate tip leakage flow in a linear compressor cascade with moving casing, and the result was compared with the experimental results and LES results. The hybrid approach combines delayed detached eddy simulation (DDES) with an improved RANS–LES hybrid model aimed at wall modeling in LES (WMLES). In this code, the convective flux was solved using fourth-order skew-symmetric scheme and the Spalart–Allmaras (S–A) model was applied as a subgrid scale (SGS) model. This hybrid RANS/LES model code was successfully validated by simulation of homogeneous isotropic turbulence, turbulent channel flow, and backward facing step flow. After validation, a 3D compressor cascade tip leakage flow with different specific blade tip clearances was simulated via this code. Result shows that the blade surface pressure distribution agrees well with the results of experiment and LES. The hybrid RANS/LES model captures intensive vortices clearly, including tip leakage vortex, tip separation vortices, induced vortices, and abundant vortex structures generated by the interaction between tip separation vortices and tip leakage vortex. The end-wall vortical structures were observed in detail being described by Q vortex identification method and meanstream lines. The effect of tip-gap size on total pressure loss was investigated and it was found that there is a best tip gap with most stable tip leakage vortex and least pressure loss.

Flow dynamics and wall-pressure signatures in a high-Reynolds-number overexpanded nozzle with free shock separation

A delayed detached eddy simulation of an overexpanded nozzle flow with shock-induced separation is carried out at a Reynolds number of , based on nozzle throat diameter and stagnation chamber properties. In this flow, self-sustained shock oscillations induce local unsteady loads on the nozzle wall as well as global off-axis forces. Despite several studies in the last few decades, a clear physical understanding of the factors driving this unsteadiness is still lacking. The geometry under investigation is a subscale truncated ideal contour nozzle, which was experimentally tested at the University of Texas at Austin at a nozzle pressure ratio of 30. Under these conditions, the nozzle operates in a highly overexpanded state and comprises a conical separation shock that merges to form a Mach disk at the nozzle centre. The delayed detached eddy simulation model agrees well with the experimental results in terms of mean and fluctuating wall-pressure statistics. Wall-pressure spectra reveal a large bump at low frequencies associated with an axisymmetric (piston-like) motion of the shock system, followed by a broad and high-amplitude peak at higher frequencies associated with the Mach waves produced by turbulent eddies convecting through the detached shear layer. Moreover, a distinct peak at an intermediate frequency ( ) persists in the wall-pressure spectra downstream of the separation shock. A Fourier-based analysis performed in both time and space (azimuthal wavenumber) reveals that this intermediate-frequency peak is associated with the (non-symmetric) pressure mode and is thus related to the generation of aerodynamic side loads. It is then shown how the unsteady Mach disk motion is characterized by an intense vortex shedding activity that, together with the vortical structures of the annular shear layer, contributes to the sustainment of an aeroacoustic feedback loop occurring within the nozzle.

Computational Analysis of Rotor-Blown-Wing for Electric Rotorcraft Applications

This Paper examines the performance of a rotor-blown-wing in hover and forward flight conditions. Flow solutions were generated using Helios, with a delayed detached eddy simulation model. The configuration is based on one set of rotors/wing of a quadrotor biplane tail-sitter aircraft. Simulations were conducted to assess the effect of varying angle of attack, rotor revolutions per minute with rotor speed, and rotor diameter. Two configurations were examined, the rotor-blown-wing baseline with two 60.96 cm diameter rotors and the configuration with four 30.48 cm diameter rotors. The smaller rotors were analyzed at the revolutions per minute corresponding to producing half the thrust of the rotor-blown-wing baseline rotor. The presence of the wing in hover resulted in the rotor-blown-wing baseline rotor operating at 1.9% lower power loading than the same rotor in isolation. In comparison, the configuration reduced power loading by 13.6% compared to the isolated rotor. In forward flight (airplane mode), an increasing angle of attack was shown to increase thrust produced on the downstroke side of the rotor. Furthermore, the presence of the wing increases the thrust produced on the bottom half of the disk. Both the blown wings increase the ratio from 3.2 for the isolated wing to 3.6 and 4.3 for the rotor-blown-wing baseline and configurations, respectively.

Comparison of different turbulence models in predicting cohesive fluid mud gravity current propagation

A numerical study of propagation of cohesive fluid mud gravity currents in the form of lock-exchange was done using the OpenFOAM open source toolbox. An Eulerian approach solution for three separate phases was developed by incorporating a rheological model to predict the front position of cohesive fluid mud gravity currents. The model also simulates features in the complete movement phases including slumping, self-similar, and viscous in which the dynamics of propagation are affected by the balance of viscous and buoyancy forces, and the inertia force is negligible. The influence of using different turbulence models containing sub-grid scale (SGS), modified SGS, detached eddy simulation (DES), delayed-detached eddy simulation (DDES), Launder-R eece-Rodi (LRR), and k-ɛ models on the accuracy of simulation results was evaluated by comparing with available experimental data. The results show that the selection of the proper turbulence model is one of the most important issues for this type of the numerical modeling. The more efficient turbulence model was suggested and tabulated for each stage of propagation and different selected concentrations of 1,045, 1,140, and 1,214 g/L. Although different turbulence models (except k-ɛ) lead to front propagation dynamic simulation results that are in good agreement with the experimental measurements in the early stage of propagation for low concentrations, only DES, SGS, and modified SGS are able to capture the Kelvin-Helmholtz instability vortex shapes at the dense fluid interface, which is the main characteristic of the gravity current through the slumping phase. The calculated accuracies of SGS and modified SGS in predicting gravity current propagation for the both self-similar and viscous phases also are slightly better than DES, DDES, and LRR model results. The results of this study confirmed the performance and efficiency of the modified SGS model in which the interaction coefficients between phases are calibrated for the numerical modeling of fluid mud gravity current propagation.

Near-Field Simulations of Film Cooling with a Modified DES Model

Modeling the heat transfer characteristics of highly turbulent flow in gas turbine film cooling is important for providing better insights and engineering solutions to the film cooling problem. This study proposes a modified detached eddy simulation (DES) model for better film cooling simulations. First, spatially varying anisotropic eddy viscosity is found from the results of the large eddy simulation (LES) of film cooling. Then the correlation for eddy viscosity anisotropy ratio has been established based on the LES results and is proposed as the modification approach for the DES model. The modified DES model has been tested for the near-field film cooling simulations under different blowing ratios. Detailed comparisons of the centerline and 2D film cooling effectiveness indicate that the modified DES model enhances the spanwise spreading of the temperature field. The DES model leads to deviations of 62.4%, 39.8%, and 33.5% from the experimental centerline effectiveness under blowing ratios of 0.5, 1.0, and 1.5, respectively, while the modified DES reduces the deviations to 51.5%, 26.7%, and 28.9%. The modified DES model provides a promising approach for film cooling numerical simulations. It embraces the advantage of LES in resolving detailed vortical structure dynamics with a moderate computational cost. It also significantly improves the original DES model on the spanwise counter rotating vortex pair (CRVP) spreading, mixing, and effectiveness prediction.