Wall-resolved Large Eddy Simulation Research Articles

Leading-edge contamination and its effects over a controlled-diffusion compressor blade for varying levels of freestream turbulence

A tiny separation bubble appears at the leading-edge of a controlled-diffusion compressor stator blade at an off-designed inflow angle of 38.3°, when a wall-resolved large-eddy simulation (LES) is employed to assess the flow field at a Reynolds number (Re) of 2.1×105. The objective of the study is to examine how this leading-edge bubble influences the transition and spatial evolution of the boundary layer on the suction surface before the mid-chord for varying levels of inlet freestream turbulence (FST). When compared with the experiment, LES resolves the flow field with an appreciable accuracy, although some discrepancies exist in the surface pressure distribution. The boundary layer is pre-transitional at the leading-edge followed by a decay in fluctuations up to 40% of the chord (C), attributing to the local flow acceleration at the FST level of 1.5%. Additionally, the boundary layer appears laminar after recovering from the leading-edge contaminations near the mid-chord but separates again because of the adverse pressure gradient with augmentation of turbulence leading to breakdown around 0.70 C. When the FST level is increased to 7.6%, an earlier reattachment occurs, shortening the leading-edge bubble length. In this case, the longitudinal streaks continuously amplify with significant three-dimensional motions near the mid-chord, and the bubble eventually disappears in the second half of the blade. In brief, the LES effectively resolves the contaminations of the boundary layer due to the appearance of the leading-edge separation with increasing levels of background disturbances.

Evaluation of Subfilter Model Performance for Large-Eddy Simulations of Supercritical Fluids

Abstract The accuracy of three large-eddy simulations (LES) is assessed using a reference dataset obtained via direct numerical simulation (DNS). All of the LES simulations employ the dynamic Smagorinsky model to close the momentum equation and a dynamic gradient model to close the total energy equation. The LES data are obtained on three grids with resolutions spanning from the wall-resolved LES limit to two successive levels coarser in the spatial and temporal domains. The configuration employed for the study is a three-dimensional spatially evolving turbulent shear layer. The working fluid is pure carbon dioxide. The system is maintained at a supercritical state near the critical point such that the field is dominated by strongly nonlinear thermophysics. This allows the analysis to occur under conditions where the subfilter closures are significantly strained by the thermodynamics. Results explore characteristics of the turbulence from both a modeling and fundamental perspective. First, mixing layer growth rates are quantified. Discrepancies are found between the reference DNS data and the LES data. Energy spectra, turbulent transport coefficients, and Reynolds stress anisotropy results are presented to explore the origins of this mismatch.

A wall model for separated flows: embedded learning to improve a posteriori performance

Developing large-eddy simulation (LES) wall models for separated flows is challenging. We propose to leverage the significance of separated flow data, for which existing theories are not applicable, and the existing knowledge of wall-bounded flows (such as the law of the wall) along with embedded learning to address this issue. The proposed so-called features-embedded-learning (FEL) wall model comprises two submodels: one for predicting the wall shear stress and another for calculating the eddy viscosity at the first off-wall grid nodes. We train the former using the wall-resolved LES (WRLES) data of the periodic hill flow and the law of the wall. For the latter, we propose a modified mixing length model, with the model coefficient trained using the ensemble Kalman method. The proposed FEL model is assessed using the separated flows with different flow configurations, grid resolutions and Reynolds numbers. Overall good a posteriori performance is observed for predicting the statistics of the recirculation bubble, wall stresses and turbulence characteristics. The statistics of the modelled subgrid-scale (SGS) stresses at the first off-wall grids are compared with those calculated using the WRLES data. The comparison shows that the amplitude and distribution of the SGS stresses and energy transfer obtained using the proposed model agree better with the reference data when compared with the conventional SGS model.

Large Eddy Simulation of an Open Fan Blade at Full-Scale Reynolds Number

Abstract Large-scale commercial turbofan designs are typically evaluated early in the technology maturation phase through subscale rig tests, while evaluations at full scale can only feasibly occur much later in a given engine development program. Therefore, how Reynolds number (Re) affects the aerodynamic and acoustic performance is of key interest while multiple candidate fan designs are still being evaluated and refined early in the program, and often tested scaled down to lower Re relative to the end application. To confidently evaluate full-scale Re performance, however, large-scale physical testing is traditionally required because the high-fidelity simulations needed to capture the complex physics associated with high Re turbulent flows, such as wall-resolved large eddy simulations (LES), are challenging due to the extremely high computational cost. In this article, we present wall-resolved LES of an open fan blade at full scale for a highly loaded design operating at a condition representative of takeoff for acoustic considerations. The simulations are at high order (up to sixth) and have been performed using the unstructured LES solver, GENESIS. These simulations extend prior research to allow for a study of practically relevant flight scale Re, for which wall-resolved LES is now possible with computing capability available at the Oak Ridge Leadership Computing Facility (OLCF) exascale supercomputer, Frontier. The observed effects at flight scale Reynolds number of the flow physics on the blade and into the wake are presented in specific regions of interest that can affect the overall blade aeroacoustic design.

Implicit near-wall domain decomposition approach for large eddy simulation of turbulent flow separation

To mitigate the high computational cost associated with resolving small near-wall eddies in large eddy simulation (LES) while achieving acceptable accuracy, this work extends the implicit near-wall domain decomposition (INDD) method to a hybrid Reynolds-averaged Navier–Stokes (RANS)/LES zonal decomposition approach. In this framework, the LES solution is first computed using a Robin-type (slip) wall boundary condition on a coarse mesh. This solution is then iteratively corrected in the near-wall region based on an updated solution derived from simplified one-dimensional (1D) RANS equations. It is important that the composite solution is smooth thanks to the specially designed slip boundary conditions. The performance of the proposed approach is assessed for flow over a plain channel at different Reynolds numbers and for a periodic hill at ReH=10,595, using very coarse meshes. Applying the INDD technique to both flows results in a significant accuracy improvement compared to unresolved LES, demonstrating good generalization capability across different turbulent viscosity models, such as algebraic or RANS turbulence models. Meanwhile, when applying the k – l RANS model to channel flow cases, the quality of predictions by INDD remains relatively independent of interface locations. Compared to reference wall-resolved LES, the INDD technique significantly reduces the overall computational cost by using simplified RANS equations and more importantly, by requiring far fewer grid points.

Modulation of the local mass and heat transfer of turbulent double-diffusive convection under stable thermal stratifications

We report on numerical studies of bounded double-diffusive turbulent convection, which involves the combined effects of concentration/solutal and thermal buoyancy forces. Our study focuses on an intermediate range of the characteristic non-dimensional numbers, specifically 107≤Rac≤109, and 0≤Raθ≤106. We use fixed values for the concentration and temperature Prandtl numbers (i.e. Prc=700, Prθ = 7), which approximately correspond to seawater properties. We apply wall-resolved Large Eddy Simulations (LES) and compare the obtained results with available Direct Numerical Simulations (DNS) in the literature. Our findings show an overall good agreement in predicting the global wall mass and heat transfer coefficients, achieved with significantly reduced computational costs. Furthermore, the local mass and heat transfer distributions reveal a high sensitivity to the strength of the vertically imposed stable thermal stratification. Finally, we present the vertical profiles of the long-term time-averaged first and second moments.

Structure and Dynamics of Bleed-Controlled Impinging Shock/Turbulent-Boundary-Layer Interactions

Porous boundary-layer bleed alleviates the detrimental effects of shock/turbulent-boundary-layer interactions (SBLIs) in high-speed vehicles. However, many underlying mechanisms through which bleed influences SBLI dynamics remain poorly understood, including unsteady separation mitigation, effects on low-frequency spectra, and turbulent kinetic energy (TKE) modulation. Proper resolution of the dynamics of these phenomena motivates the use of wall-resolved large-eddy simulations. The configuration is based on experiments at Mach 2.5 and a momentum-thickness Reynolds number of 2800, on which a shock of flow-deflection angle of 8 deg impinges. Porous bleed patches are considered with resolution of the flow structure in individual holes. Two different suction strengths are examined, denoted “half-” and “full-bleed” cases based on the sonic mass flow coefficient. Although both bleed cases localize and reduce the mean reversed flow region, only the full-bleed case successfully reduces unsteadiness, TKE, wall-pressure loading, and overall distortion due to the SBLIs. These distinctions are reflected in various local and global effects of bleed, which are examined with three-dimensional modal analysis. Among the key findings is energy shifting from the low-frequency separation behavior to a higher-frequency signature, which modulates the bleed-associated shocks and expansions. Overall, the study highlights the complex interactions between individual bleed-hole flow structures that cumulatively yield the observed overall effects, which are important in optimizing bleed systems for various design objectives.

Guideline for Large-Scale Analysis of Centrifugal Blower Using Wall-Resolved Large Eddy Simulation

Abstract To reduce the number of prototypes during product design and accurately predict unsteady phenomena occurring at off-design points, a method for accurately predicting the performance of centrifugal blowers through numerical analysis is required. This article presents a guideline for accurately predicting the performance of centrifugal blowers using compressible flow analysis with large eddy simulation (LES). In LES analysis, it is important to have a grid resolution that resolves the minimum vortex scale near the wall (referred to as wall-resolved LES) and to consider detailed geometry such as the length of the suction pipe. The calculations in this study used a model blower, which is a scale model of a single-stage centrifugal blower for use in industrial plants. The model blower was experimentally measured for various parameters such as the blower pressure coefficient, the static-pressure-rise coefficients of the impeller and vane-less diffuser, the shaft power, and the pressure fluctuations at the inlet of the impeller and the inlet of the vane-less diffuser. The results of these measurements were compared with those obtained from the wall-resolved LES. The study confirmed that the accuracy of performance prediction can be improved to less than a 4.0% error in the blower pressure coefficient at both design and off-design operating points by resolving the minimum vortex scale with 14.6 billion-grid elements and considering the detailed geometry.

Characterizing disturbance growth and transition of laminar separation bubbles subjected to varying freestream turbulence

The spatial manifestation of a boundary layer subjected to an adverse pressure gradient for varying freestream turbulence (FST) is discussed here through experiments and a wall-resolved large eddy simulation (LES). Three levels of FST, i.e., 1.02%, 2.1%, and 3.5%, are considered at a Reynolds number of 0.2 × 106 based on the inlet velocity and plate length. A laminar separation bubble (LSB) appears for FST levels of 1.02%, where the shear layer becomes unstable via the Kelvin-Helmholtz (K-H) mechanism. Bubble suppression is apparent, where transition occurs via the Klebanoff mode (K-mode), bypassing the K-H instability as the FST level is increased to 3.5%. The streamwise evolution of fluctuations reveals an exponential growth at a low FST of 1.02%, whereas it changes to algebraic at a higher FST level of 3.5%. Notably, a dual growth of velocity fluctuations, i.e., an algebraic growth in the initial part of LSB followed by an exponential growth, illustrates the coexistence of K-H instability and K-mode at an FST level of 2.1%: a finding corroborated by LES. Additionally, local linear stability analysis and the evolution of intermittency provide valuable insights into the growth of modal and non-modal instabilities and their interactions.

Boundary layer stability on a rotating wind turbine blade section

Wall-resolved large eddy simulations of the flow on a rotating wind turbine blade section are conducted to study the rotation effects on laminar-turbulent transition on the suction surface. A chord Reynolds number of 1×105 and angles of attack (AoA) of 12.8°, 4.2°, and 1.2° are considered. Simulations with and without rotation are performed for each AoA. For AoA=12.8°, rotation increases the reverse flow from 7% of the free-stream velocity in the non-rotating case to 16% of it in the rotating case in the laminar separation bubble (LSB), triggering an oblique instability mechanism in the latter, leading to a faster breakdown to small-scale turbulence. However, rotation delays transition and reattachment in 3%–4% of the chord due to the acceleration of the boundary layer upstream of the LSB, which is subject to a strong adverse pressure gradient (APG), stabilizing Tollmien–Schlichting (TS) waves. Regarding AoA=4.2° and 1.2°, rotation slightly decelerates the attached boundary layer since the APG is very mild but accelerates the separated flow downstream, stabilizing Kelvin–Helmholtz (KH) modes. This mitigates the oblique instability mechanism and slows down the breakdown of KH vortices in the rotating case. In these cases, the transition location is little affected by rotation, possibly due to a rotation-independent absolute instability. Rotation also generates a spanwise tip-flow in the LSB for AoA=4.2° and 1.2°, which is highly unstable and triggers stationary and traveling crossflow modes. Nevertheless, the amplitudes of these modes remain too low to trigger transition.

Towards Wall-Resolved Large-Eddy Simulation of the High-Lift Common Research Model

In the present study, we performed a sixth-order wall-resolved large-eddy simulation (WRLES) of the high-lift Common Research Model (CRM-HL) on the Leadership Class Computing Cluster Summit. During the 4th High-Lift Prediction Workshop (HLPW-4), wall-modeled LES (WMLES) and hybrid Reynolds-averaged Navier–Stokes (RANS)/LES approaches showed promise in predicting the maximum lift and large flow separations near stall. In those simulations, however, laminar and transition regions were not resolved since the flow was assumed to be fully turbulent. If one wants to resolve these regions, the only viable approach is WRLES. The main purpose of the present study is to demonstrate the feasibility of WRLES for a complex real-world configuration at the wind tunnel Reynolds number. A high-order unstructured mesh LES solver called hpMusic was employed in the study. The simulation at solution polynomial order P=5 has more than 14 billion degrees of freedom per equation. Computational results are compared to experimental data in the form of surface oil flows and pressure coefficient profiles. We highlight lessons learned from attempting a grand-challenge type large-scale simulation: 1) such a simulation is feasible but very expensive, estimated to be at least three orders more expensive than WMLES, 2) oil flows produced with WRLES agree very well with experimental oil flows in fine detail, not observed in those produced with WMLES, and 3) flow visualization is a severe bottleneck, and parallel postprocessing capability is needed.

A critical assessment of Navier–Stokes and lattice Boltzmann frameworks applied to high-lift configuration through a multiresolution approach

The present work focuses on a thorough assessment of the influence of two very different numerical approaches, namely, Navier–Stokes (NS) and the lattice Boltzmann method (LBM), to simulate the flow past a three-element airfoil through zonal detached eddy simulation (ZDES). Both computations (ZDES-NS and ZDES-LBM) are compared to the reference results, namely, a wall-resolved large eddy simulation (WRLES) as well as the experimental data. It is shown that despite very different numerical modeling, the two ZDES provide very consistent results, with the first- and second-order statistics obtained with equivalent accuracy in the impingement region. In light of present results, the ZDES mode 2 (2020) turbulence model within an LBM framework appears as a judicious combination for high-lift flow applications owing to its robustness regarding the use of very fine isotropic Cartesian grids. In addition, ZDES-NS exhibits a very good agreement with both references, especially WRLES despite having 40 times less nodes.

Role of very large-scale motions in shock wave/turbulent boundary layer interactions

The present study investigates the cause of low-frequency unsteadiness in shock wave/turbulent boundary layer (TBL) interactions. A supersonic turbulent flow over a compression ramp is studied using wall-resolved large eddy simulation (LES) with a freestream Mach number of 2.95 and a Reynolds number (based on δ0: the thickness of the incoming TBL) of 63 560. From the view of stability analysis, the effect of intrinsic instability on such low-frequency unsteadiness is excluded from the flow system by designing a ramp angle of 15°, and our attention is paid to the convective instability contributed by the incoming TBL. The LES results are analyzed by linear and nonlinear disambiguation optimization (LANDO), spectral proper orthogonal decomposition (SPOD), and resolvent analysis. The LANDO results reveal a streamwise scale-frequency relation of coherent structures in a very long (around 60δ0) TBL, which indicates that the dynamics of very large-scale motions (VLSMs) in the TBL are featured by a low frequency. The SPOD results reveal that the most energetic SPOD mode features a low frequency that is identical to the dominant low frequency of the wall-pressure spectrum. Additionally, coherent structures of the mode resemble the VLSMs in the incoming TBL. These consistencies imply that the dynamics of VLSMs contribute to the low-frequency unsteadiness of the present flow. A resolvent analysis then further suggests that the origins of low-frequency dynamics of the present flow are from the VLSMs, which can be optimally amplified by the forcing in the turbulent flow.

Compressibility effect on flow characteristics over a circular cylinder at Reynolds number of 3900

The compressibility effect of flow over a circular cylinder has been investigated using wall-resolved large eddy simulation. The Reynolds number in terms of the freestream quantities and the cylinder diameter is fixed at 3900 while varying the freestream Mach number from 0.01 to 0.5. Mesh quality, numerical scheme, and subgrid-scale model are carefully verified prior to the detailed flow study. Results such as Mach number effects on the drag coefficient, the shape of the mean streamwise velocity profile in the near-wake, the length of the recirculation zone, and shear layer instability are provided. Although compressibility suppresses the Kelvin–Helmholtz instability and mixing process within the shear layer, it increases the velocity fluctuation in the boundary layer and the pressure difference between the freestream and recirculation zone, which intensifies the wake oscillation, shedding amplitude, thus shortens the recirculation zone significantly with the Mach number up to 0.5. This phenomenon is different from that found in lower Reynolds number cases where the length of the recirculation zone elongates as the Mach number increases. The deficit of the velocity profile shape in the near-wake depends on the length of the recirculation zone. Furthermore, inside the wake zone and near the cylinder back wall, two pairs of recirculation bubbles emerge as the Mach number increases.

Large-eddy simulation of vortex interaction in pitching-fixed tandem airfoils

In this study, the interaction of vortices generated from an oscillating airfoil with a hindfoil placed downstream of the oscillating forefoil at low-Reynolds-number flow was investigated numerically. The forefoil entered a deep dynamic stall induced by large-amplitude pitching oscillation. The dynamic stall process is characterized by unsteady separation and the formation of a strong clockwise vortex. A wall-resolved large-eddy simulation approach was applied to compute the flowfield. The numerical measurements were performed for an incompressible flow at a Reynolds number of Re = 30 000 based on chord length with a pitching reduced frequency of K= 0.5, and amplitude of A = 14.1° over Selig–Donovan 7003 airfoils. A single-airfoil case was validated against numerical and experimental measurements. In the present study, we investigated the flowfield and aerodynamic coefficients resulting from the deep dynamic stall of the pitching forefoil and the vortex interaction in tandem-airfoil configuration related to micro-air vehicle applications by employing large-eddy simulation approach. Large-eddy simulation was also compared to two-dimensional unsteady Reynolds-averaged Navier–Stokes simulation to determine the accuracy and validity of the low-fidelity approach in prediction of deep dynamic stall and vortex interaction at low-Reynolds-number flow.

Low-frequency dynamics of turbulent recirculation bubbles

We revisit the origin of low-frequency unsteadiness in turbulent recirculation bubbles (TRBs), and, in particular, the hypothesis of a dynamic feedback mechanism between unconstrained separation and reattachment locations. To this end, we conduct wall-resolved large-eddy simulations of a novel experimental configuration where a shock-induced TRB forms over a backward-facing step that is intended to intercept the hypothesized dynamic feedback. Our results demonstrate, for the first time, effective suppression of the low-frequency characteristics of the TRB without reducing its size, strongly supporting our hypothesis.

URANOS-2.0: Improved performance, enhanced portability, and model extension towards exascale computing of high-speed engineering flows

We present URANOS-2.0, the second major release of our massively parallel, GPU-accelerated solver for compressible wall flow applications. This latest version represents a significant leap forward in our initial tool, which was launched in 2023 (De Vanna et al. [1]), and has been specifically optimized to take full advantage of the opportunities offered by the cutting-edge pre-exascale architectures available within the EuroHPC JU. In particular, URANOS-2.0 emphasizes portability and compatibility improvements with the two top-ranked supercomputing architectures in Europe: LUMI and Leonardo. These systems utilize different GPU architectures, AMD and NVIDIA, respectively, which necessitates extensive efforts to ensure seamless usability across their distinct structures. In pursuit of this objective, the current release adheres to the OpenACC standard. This choice not only facilitates efficient utilization of the full potential inherent in these extensive GPU-based architectures but also upholds the principles of vendor neutrality, a distinctive characteristic of URANOS solvers in the CFD solvers' panorama. However, the URANOS-2.0 version goes beyond the goals of improving usability and portability; it introduces performance enhancements and restructures the most demanding computational kernels. This translates into a 2× speedup over the same architecture. In addition to its enhanced single-GPU performance, the present solver release demonstrates very good scalability in multi-GPU environments. URANOS-2.0, in fact, achieves strong scaling efficiencies of over 80% across 64 compute nodes (256 GPUs) for both LUMI and Leonardo. Furthermore, its weak scaling efficiencies reach approximately 95% and 90% on LUMI and Leonardo, respectively, when up to 256 nodes (1024 GPUs) are considered. These significant performance advancements position URANOS-2.0 as a state-of-the-art supercomputing platform tailored for compressible wall turbulence applications, establishing the solver as an integrated tool for various aerospace and energy engineering applications, which can span from direct numerical simulations, wall-resolved large eddy simulations, up to most recent wall-modeled large eddy simulations. Program summaryProgram title: Unsteady Robust All-around Navier-StOkes Solver (URANOS)CPC Library link to program files:https://doi.org/10.17632/pw5hshn9k6.2Developer's repository link:https://github.com/uranos-gpu/uranos-gpu, https://github.com/uranos-gpu/uranos-gpu/tree/v2.0Licensing provisions: BSD License 2.0Programming language: Modern Fortran, OpenACC, MPINature of problem: Solving the compressible Navier-Stokes equations in a three-dimensional Cartesian framework.Solution method: Convective terms are treated with high-resolution shock-capturing schemes. The system dynamics is advanced in time with a three-stage Runge-Kutta method. Parallelization adopts MPI+OpenACC.

Large Eddy Simulation of Laminar and Turbulent Shock/Boundary Layer Interactions in a Transonic Passage

Abstract Shock/boundary layer interactions (SBLI) are a fundamental fluid mechanics problem relevant in a wide range of applications including transonic rotors in turbomachinery. This paper uses wall-resolved large eddy simulation (LES) to examine the interaction of normal shocks with laminar and turbulent inflow boundary layers in transonic flow. The calculations were performed using GENESIS, a high-order, unstructured LES solver. The geometry created for this study is a transonic passage with a convergent-divergent nozzle that expands the flow to the desired Mach number upstream of the shock and then introduces constant radius curvature to simulate local airfoil camber. The Mach numbers in the divergent section of the transonic passage simulate single stage commercial fan blades. The results predicted with the LES calculations show significant differences between laminar and turbulent SBLI in terms of shock structure, boundary layer separation and transition, and aerodynamic losses. For laminar flow into the shock, significant flow separation and low-frequency unsteadiness occur, while for turbulent flow into the shock, both the boundary layer loss and the low-frequency unsteadiness are reduced. The time period of the unsteadiness was hypothesized to align with the time it takes for turbulent structures to convect from the shock to the trailing edge and acoustic disturbances to travel back from the trailing edge to the shock, and this is supported by the LES results.

Large-Eddy Simulations of Flow over a Backward-Facing Ramp with a Wall-Mounted Cube

Passive flow control devices, such as vortex generators (VGs), can effectively modulate the turbulent boundary layer flow near regions of adverse pressure gradients, but the interactions between the salient flow structures produced by VGs and those of the separated flow are not fully understood. In this study, a spatially evolving turbulent boundary layer interacting with a wall-mounted cube ahead of a backward-facing ramp is investigated using wall-resolved large-eddy simulations for a Reynolds number of 19,600, based on the inlet boundary layer thickness and freestream velocity. Different cube configurations are examined to isolate the effects of cube height and streamwise position. The large counter-rotating flow produced by the larger cubes generated more turbulent kinetic energy, thereby resulting in smaller separated regions over the ramp. Although significantly lower levels of turbulent kinetic energy dissipation than production are observed in the outer flow regions of the horseshoe vortex and in the induced counter-rotating flow, the spatial distribution of dissipation is similar to that of the turbulent kinetic energy. When the upstream position of an isolated single cube, relative to the leading ramp edge, is more than three cube heights, the streamwise decay of the counter-rotating flow results in lower levels of turbulent kinetic energy.

Characterization of near-wall flow and in-cylinder free-stream turbulence during the intake phase of a direct-injection engine: A flow bench study

This study investigates the characteristics of the near-wall flow and pressure-induced wall-influenced turbulence inside a direct-injection engine during the intake phase by utilizing a wall-resolved Large Eddy Simulation. An engine flow bench operating under stationary conditions is used to reduce the complexity of engine flows and to shed light on the in-cylinder flow during the intake phase. The investigation focuses on in-cylinder turbulence on symmetry (SP) and valve planes (VP), particularly emphasizing the flow close to the intake valves and the impingement region on the liner wall. An experimental dataset acquired through 2D high-speed particle image velocimetry (PIV) facilitates validation of the simulation of both time-averaged velocity field and associated turbulence structure. Turbulence anisotropy analysis shows that, in complex wall-bounded flows, the IC engine-related in-cylinder turbulence structure is characterized by the anisotropic states that cope with both axisymmetric expansion and contraction straining events. Due to the strong influence of the intake flow, the turbulence anisotropy level, expressed in terms of the two-componentality parameter F, retains its value of less than 0.85, and no turbulence occurs in accordance with the fully three-component isotropic state, characterized by the F-parameter value of 1. In the vicinity of the intake valve near wall area, the turbulence anisotropy state transitions from that resembling a canonical channel flow characteristic to curvature-induced acceleration after impingement, which aligns with axisymmetric expansion in the anisotropy invariant map. The presence of intake flow sustains turbulence anisotropy. Limitations in applying wall-function treatments for near-wall flow in engine contexts due to simplifications, such as the zero-pressure gradient assumption, are highlighted. In this respect, the interplay of non-equilibrium effects in the near-wall region needed to be further explored. Accordingly, analysis of the viscosity-affected layer near the intake valve and the flow impingement area of the liner wall underscores the importance of the wall-tangential pressure gradient in shaping the near-wall behavior. A budget analysis of the turbulent kinetic energy equation at the intake valve emphasizes the dominance of fluctuating pressure-induced diffusive transport in turbulence generation.