Improved Delayed Detached Eddy Simulation Research Articles

Study on the distribution characteristics of TBL fluctuating pressure of a submerged conical-cylindrical structure

The fluctuating pressure within turbulent boundary layers (TBL) has garnered significant attention as a pivotal factor in generating hydrodynamic noise for underwater vehicles. This study employs numerical simulations to investigate the fluctuating pressure of a submerged conical-cylindrical structure, utilizing the Improved Delayed Detached Eddy Simulation (IDDES) method. This research delves into the spatiotemporal distribution characteristics of wall fluctuating pressure across various Reynolds numbers. Notably, the power spectral density (PSD) curve of TBL fluctuating pressure exhibits relative stability at lower frequencies, whereas it undergoes a rapid decline in the high-frequency range, following an inverse proportional trend with the power-law exponent of frequency. Moreover, the dimensionless migration velocity in the parallel mid-body segment is consistent with the TBL over a flat plate, while it is slightly smaller in the outflow segment.

A detached-eddy simulation study on assessing the impact of extreme wind conditions on load and wake characteristics of a horizontal-axis wind turbine

This study utilizes improved delayed detached-eddy simulation (IDDES) to investigate the impact of extreme wind conditions on a horizontal-axis wind turbine, as specified by the IEC-61400 standard. The employed IDDES has a hybrid formulation, where SST K-ω is used to model the turbulence in the boundary layers and large-eddy simulation (LES) is used to resolve turbulence in separated flow regions and the wake area. It also allows for switching to a wall-modeled LES approach, depending on the incoming turbulence content. The research focuses on extreme operating gust (EOG), extreme horizontal shear (EHS), and extreme vertical shear (EVS) conditions at two Tip Speed Ratios (TSR). The loadings and wake characteristics are compared to uniform inlet velocity results to highlight the effects of extreme winds. The novelty of this research lies in its comprehensive investigation of wake behavior under extreme wind conditions, providing valuable insights for improving wind farm layout design and reliability in challenging operational environments. The analysis shows that the impact of the TSR on wind turbine loadings during EOG, EVS, and EHS events is significant. During EOG events for a turbine operating at low TSR, the thrust force and bending moment reach 2.38 and 2.57 times their respective values in uniform inflow conditions, while at the optimal TSR, the thrust force and bending moment increase by only 25%. In all extreme wind cases, there is an escalation in turbulence within the wake, and wake meandering is observed in the EHS and EVS cases.

Numerical study on the pulsation characteristics of tail cavities under vertical launching conditions

This study aimed to analyze the pulsation characteristics of tail cavities at different Froude numbers under vertical launching conditions. The improved delayed detached eddy simulation (IDDES), volume of fluid (VOF) model, adaptive mesh refinement (AMR), and overlapping grid technique were adopted to model the pulsation characteristics of the tail cavity. The feasibility of the model for predicting dynamic behaviors was verified by comparing the numerical and experimental results. The results demonstrated that the volume of the tail cavity pulsated periodically. However, the concurrent expansion and contraction in the integral tail cavity resulted in a relative state of cavity volume pulsation. When the expansion rate exceeded the contraction rate, the cavity volume increased, otherwise, decreased. In addition, four flow patterns were observed in the tail cavity: smooth, irregular, hybrid, and cavity-shedding regions. An increase in the Froude number augmented the tail cavity volume and proportion of irregular regions, and reduced the proportion of hybrid regions.

Reducing the contaminant dispersion and infection risks in the train cabins by adjusting the inlet turbulence intensity: A study based on turbulence simulation

Existing studies on ventilation in closed spaces mainly considered the average inlet velocity and ignored the influence of inlet turbulent fluctuation. However, the variation in inlet turbulence intensity (TI) is considerable and significantly affects the dispersion of contaminants. This study conducts numerical simulations verified by experiments to investigate the effect of the inlet TI on train contaminants dispersion and analyze infection probability variation. Firstly, the unsteady Reynolds-averaged Navier-Stokes (URANS) method and improved delayed detached eddy simulation (IDDES) method are compared in simulating the internal airflow characteristics based on the on-site measurement. The results indicate that the latter dominates in capturing airflow pulsations more than the former, although the mean airflow results obtained from both methods agree well with experimental results. Furthermore, the IDDES method is employed to investigate the effect of the inlet TI on contaminant dispersion, and the infection risks are also assessed using the improved probability model. The results show that, with the increase of TI from 5 % to 30 %, the contaminant removal grows considerably, with the removal index rising from 0.23 to 1.86. The increased TI leads to the overall and local infection risks of occupants descending significantly, wherein the former decreases from 1.53 % to 0.88 % with a reduction rate of 42 %, and the latter drops from 3.30 % to 2.16 % with a mitigation rate of 35 %. The findings can serve as solid guidelines for numerical method selection in accurately capturing the indoor dynamic airflow distribution and for the ventilation parameters design regarding TI inside trains to mitigate the airborne infection risk.

Numerical study on the quadrupole sound source in aerodynamic noise of high-speed pantographs

ABSTRACT Insufficient consideration of aerodynamic noise source will affect the accurate evaluation of high-speed pantograph noise. In this study, we present an approach to separate and quantify the dipole and quadrupole noises of pantographs. The improved delayed detached eddy simulation (IDDES) was used for turbulence modelling and two acoustic surface integral methods were used to predict the noise. The results show that the pantograph noise is caused by the vortex shedding and interaction in the wake. The running speed does not change the distribution of the two aerodynamic noise sources, but the intensity increases significantly. Although the quadrupole noise increases with the speed level, the dipole noise still dominates. The sound pressure levels of the two noise sources increased by about 60 log10V and 70~80 log10V, respectively. The noise energy is concentrated in 160-2500 Hz, and the dominant frequency is proportional to the speed level.

A synthetic particle group method for the unsteady interaction between shock wave and boundary layer past a compression ramp

To overcome the lack of resolved turbulent flow structures generated by the improved delayed detached eddy simulation (IDDES) model when simulating the shock wave and boundary layer interaction (SWBLI), a new, nonzonal, embedded synthetic turbulence generation method, named the synthetic particle group method (SPOM), is proposed and validated by simulating the supersonic flow past a flat plate at Mach 2.25. In the attached boundary layer, the SPOs are automatically introduced to trigger the turbulent perturbations. The turbulent boundary layer is successfully resolved and fully developed in a short streamwise range to produce the desired outcome. The effect of grid scale is also studied, and a suitable grid-scale value is recommended. Then, the SPOM is applied to the compression ramp flow at Mach 2.25 with unsteady SWBLI. The results show that the IDDES-SPOM is highly effective, accurate, and able to model scenarios where the original IDDES simulation fails. Furthermore, the effects of the inlet boundary layer thickness on local separation unsteadiness are studied. From the results, the lower frequency motion is attributed to a more fully developed boundary layer.

An improved laminar–turbulent transition cavitation model using the IDDES method

Prediction of the detachment positions of sheet cavitation remains an unsolved problem, being not only dependent on local pressure but also closely related to the boundary layer transition. For hydrofoils, traditional cavitation models tend to predict premature cavity detachment positions. In the study reported here, to obtain cavity detachment positions that match experimental results, improvements are made to both turbulence models and cavitation models. A scale-resolving transition turbulence model is established by incorporating transport equations to represent boundary layer transition that are based on the improved delayed detached eddy simulation (IDDES) method. The intermittency γ, representing the probability of turbulence at a specific point in space, is introduced into the homogeneous cavitation model to account for the influence of the laminar–turbulent transition on the sheet cavitation detachment position. Numerical results show that the IDDES-based transition turbulence model combines transition and scale-resolving capabilities. The improved turbulence transition cavitation model proposed here is shown to be able to accurately predict the detachment position of sheet cavitation around two-dimensional hydrofoils and a typical axisymmetric ITTC body.

Flow over a 25°Ahmed body at a Reynolds number characteristic of suburban driving speeds

Four turbulence models were used to predict the flow over a 25°Ahmed body at a Reynolds number characteristic of suburban driving speeds in the United States: the k-ω shear stress transport (SST) model, large eddy simulation (LES) with the Smagorinsky-Lilly subgrid scale model, LES with the wall-adapting local eddy viscosity (WALE) subgrid scale model, and improved delayed detached eddy simulation (IDDES). The Reynolds number based on body height was ReH=2.65×105 - this corresponds to a freestream velocity of 13.44m/s, or approximately 30mph. The k-ω SST model only showed promise in predicting the drag coefficient; otherwise, it significantly underpredicted the lift coefficient and predicted an incorrect wake structure in terms of flow separation and the size of the separation bubble behind the body. All three scale-resolving models predicted a wake structure in good agreement with experimental data, with the WALE model and IDDES providing the best agreement in terms of separation bubble size, streamwise velocity magnitude, and turbulent kinetic energy in the wake. The best predictions of the aerodynamic forces were those of the WALE model, with overpredictions of only 5.45% for drag and 5.65% for lift. Overall, both the WALE model and IDDES demonstrated promise in predicting the wake structure and aerodynamic forces, but the best agreements were achieved with the WALE model. Therefore, the WALE model showed the lowest dependence on Reynolds number when comparing lower Reynolds number simulations to higher Reynolds number experiments for this situation.

Cooling enhancement for engine parts using jet impingement

A computational study has been performed to evaluate the use of jet impingement for cooling applications in the automotive industry. The current study uses an entire internal combustion engine cylinder with its components as a computational domain. An unsteady numerical solution for the Navier-Stokes equations was carried out using Improved Delayed Detached Eddy Simulation (IDDES). The volume of fluid approach is proposed to track and locate the liquid jet surface that is in contact with the air. The conjugate heat transfer approach is used to link the heat transfer solution between the fluid and the solid. The boundary conditions that are employed in the study are provided from lab experiments and one-dimensional simulations. The cooling jet in this study targets the hottest region in the piston, i.e., the region underneath the exhaust valve. Three nozzle sizes with flows at different Reynolds numbers are chosen to examine the thermal characteristics of the cooling jet. The computational study reveals that for a specific Reynolds number, the smaller diameter nozzle provides the highest heat transfer coefficient around the impingement point. The maximum relative velocity location at the impingement point slightly leads the location of the maximum Nusselt number. The maximum temperature in the piston decreases by 7% to 11% as the nozzle diameter changes from 1.0 to 3.0 mm for a jet Reynolds number of 4,500. If a correct selection is made for the nozzle size, the cooling jet can be efficiently used to reduce the temperature and alleviate the thermal stresses in the piston in the region underneath the exhaust valve where the maximum temperature occurs.

Numerical and experimental investigation of aerodynamic noise from a cooling fan in a turbulent flow

The investigation into aerodynamic noise arising from rotating surfaces bears significant practical implications. Among these, engine cooling fans have persistently been identified as primary contributors to vehicle noise. This study aims to provide a deeper comprehension of the complex unsteady flow dynamics surrounding an automotive cooling fan and its consequential impact on the generation of aerodynamic noise. Prediction of sound generated from fluid flow, despite its difficulty, can be simulated using modern numerical techniques and computational fluid dynamics (CFD). This research undertakes both numerical and experimental investigations. The experiment involves evaluating fan pressure against mass flow rate at 1500 rpm, while aerodynamic noise assessment transpires at two rotational speeds of 1500 rpm and 2500 rpm. Empirical sound pressure level data of the fan is meticulously captured using the requisite measurement apparatus. In addition, numerical investigations of the aerodynamic noise of an automotive cooling fan based on computational fluid dynamics and computational aeroacoustic (CAA) method have been performed. Initially, a steady-state aerodynamic simulation is carried out, followed by the simulation of the flow field through the application of the improved delayed detached eddy simulation (IDDES) formulation. The pressure rise of the fan versus the mass flow rate is obtained. The satisfactory concurrence observed between the simulation outcomes derived from the numerical method and the experimental dataset stands as notable validation. For the aeroacoustic computation, the Ffowcs Williams-Hawkings model is invoked to deduce sound pressure levels at specific flow points. The broadband noise sources model is also used to obtain the sound power level on the blade surface. Conclusively, it emerges that maximal noise manifestation occurs at a 90° degree angle, corresponding to the hub’s frontal orientation, with discernible dominance of tonal noise within lower frequency ranges (sub-1000 Hz).

Aerodynamic performance analysis of a floating wind turbine with coupled blade rotation and surge motion

The unsteady aerodynamic characteristics and interference effects of a floating wind turbine are significantly influenced by the six-degree-of-freedom (6DoF) motions. In this paper, the computational fluid dynamics (CFD) method using the overset grid technique and the improved delayed detached eddy simulation (IDDES) model was adopted to investigate the effects of harmonic enforced surge motions on the aerodynamic performance and wake characteristics of wind turbines. The aerodynamic load coefficients including the constant term, damping coefficients (surge velocity-induced), and additional mass coefficients (surge acceleration-induced), were fitted by using the least squares method at different surge frequencies and surge amplitudes. The blade pressure distributions and wake characteristics were analysed in detail. The Ω ~ R of the third-generation vortex identification method was applied to visualize vortex evolution. The numerical results are evaluated against the data obtained by wind tunnel experiments, indicating an acceptable relative error of 3.45 % for the power coefficient, C p , at the rated tip speed ratio (TSR). The higher frequency and greater amplitude surge motions lead to more dramatic fluctuations for the power coefficient than the axial load coefficient. The neglect of the additional mass coefficient only results in an acceptable error. Furthermore, the mean damping coefficient is on average approximately 3.5 times the mean constant term coefficient for C p , approximately 1.5 times for C z . In terms of the blade pressure distributions and wake characteristics, a higher comprehensive induced velocity, V c , is induced to expand the wider high-pressure area and shrink the low-pressure area at the pressure surface. Meanwhile, toroidal vortex ropes were induced by surge motion. Besides, the surge motion at high frequency and greater amplitude positively impacts enhancing wake deficit recovery.

Numerical investigation on the mechanism of cascade unsteady force control based on pre-stator actuated oscillating trailing edge flaps

Unsteady force caused by rotor - stator interaction is one of the main excitation sources of impeller machinery vibration. To suppress the unsteady force, the stator wakes are conducted by the secondary flow generated by stator actuated oscillating trailing edge flaps (AOTEF). The unsteady Reynolds averaged Navier-Stokes equation (RANS) method based on the shear transport turbulence k-ω model and the improved delayed detached eddy simulation (IDDES) method are employed to numerically study a single cascade with AOTEF. The results show that the AOTEF oscillating phase angle determines the phase relationship between the stator wake and the rotor blade, and then affects the strength of the interaction between the stator wake and the rotor blade. Under the optimal phase of AOTEF, the rotor unsteady force decreases by 3 dB at rotor-stator blade passing frequency. The AOTEF significantly rises the peak value of the stator wake deficit. The amplitude of stator wake vorticity is significantly weakened by AOTEF, and the vortex shedding phase is regulated by AOTEF actuating phase. This study provides a new idea for the vibration and noise reduction of turbomachinery.

Spatial-temporal characteristics of the transient flow field around high-speed trains transiting the subgrade-cutting transition section under crosswinds

High-speed trains (HSTs) transiting subgrade-cutting transition sections in crosswinds have become a common operating scenario. This paper utilizes the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model, considers air compressibility, and establishes a three-dimensional coupled train-subgrade-wind dynamics model. The aerodynamic load (AL) variation rules of trains and discrepancies in the flow field mechanisms when HSTs transit various types of subgrade-cutting transition sections [half cutting and half flat (HCHF), double side cutting (DC), and half cutting and half embankment (HCHE)] under crosswind conditions are revealed using this model. The results indicate the following. (1) The aerodynamic performance deteriorates when trains transit three subgrade-cutting transition sections under crosswinds. (2) As trains enter the transition section from a flat approach, the head car’s AL power spectrum density (PSD) is the largest when operating in the DC case. (3) After the train drives into the subsequent operating scenario, the average of the AL in the DC case is the lowest. (4) In the DC case, a slope of 1:0.75 should be taken as the basis for the design of the corresponding cutting parameters. (5) After the train enters the cutting, the winding flow speed and number of vortex structures surrounding the trains increase significantly.

Numerical investigations of supersonic combustion characteristics of thermally cracked fuels at typical pyrolysis temperatures

Insight into supersonic combustion characteristics of thermally cracked fuels in a scramjet combustor is crucial for the development of next-generation supersonic flight vehicles. In the present study, four typical thermally cracked fuels at pyrolysis temperatures of 450, 550, 600, and 650 ℃ (denoted as ckori, ck550, ck600, and ck650) were selected. Improved delayed detached eddy simulation (IDDES) modeling with a compact skeletal mechanism and a transported multi-regime flamelet model was carried out to simulate the supersonic combustion of the target fuels in a full-scale scramjet combustor. Supersonic flow, mixing, and combustion characteristics of these fuels were quantitatively compared. Discrepancies in the combustion process are mainly at the cavity region, where the mixing efficiencies and combustion intensities of the first three fuels increase monotonically with the increasing pyrolysis temperature, while that of ck650 locates between ck550 and ck600. The increase in pyrolysis gas content will enhance the mixing process, while the increase in injection pressure will suppress the heat/mass transport between fuel and incoming air. The mixing process dominates the distributions of intermediate radicals and main products. The first three fuels tend to combust under fuel-rich condition, while ck650 tends to combust under the stoichiometric condition, which explains the distributions of OH, CO, and CO2 concentrations. The premixed and non-premixed combustion modes coexist in the model scramjet combustor, and the non-premixed combustion mode dominates the combustion process of thermally cracked fuel.

On the anti-rolling performance of a train using a vortex generator array

Vortex generators (VGs) have shown the potential to mitigate the train's operational instability issues caused by strong wind. Numerical simulations are used to predict the flow structures around a train with VGs of different heights. The improved delayed detached eddy simulation (IDDES) hybrid modeling method is adopted to predict the trailing vortices on the leeward field. The numerical method is validated by reproducing wind tunnel test results. The study results reveal that VGs are capable of reducing the rolling moment coefficient around the leeward rail of a train by about 5% ∼ 15% while keeping the drag of the train still lower than its operational drag without crosswind. The control mechanism lies on that the streamwise vortices generated by VGs are attracted to the large-scale trailing vortices, resulting in the pressure on the leeward wall rising. The differences in the domain frequencies between VGs and Baseline cases in POD modes indicate that the VGs changed the periodicity and symmetry of the vorticity fluctuation. This study provides a new method to improve the safety of trains under crosswinds.

How do dunes along a desert urban motorway affect the driving safety of sedans? Evidences from long- and short-term monitoring and IDDES

Urban on the edge of deserts usually build motorways in desert areas to fully develop its tourism resources. However, due to the long-term transport effect of wind-sand flow (WSL), the driving safety of sedans might be affected by the erratic dunes next to the desert motorway. Based on this, this study aims to give an idea of how dunes next to desert urban motorways affect the driving safety of sedans. Firstly, the movement law of WSL in desert areas is revealed based on the combination of long- and short-term monitoring methods. After determining the period of strong wind through long-term monitoring, short-term monitoring can be more effective in revealing the movement law of the WSL and the aerodynamic performance of the sedan under the effect of WSL. Afterward, a three-dimensional refined Computational Fluid Dynamics (CFD) dynamic mesh numerical model of WSL-dune-embankment-sedan-air was established based on the mosaic mesh technology. The aerodynamic impact and erosion effects of the WSL on the sedan were investigated. The main results are as follows: 1. Dunes cause varying WSL, with wind speed decreasing to 19–26% on the leeward side and increasing to about 1.35 times at the end. 2. The windward side and front of the sedan experience continuous sand impact, severely eroding the body surface, and posing safety risks. The main contributions of the present study are expected to proposed a cheap simulation scheme based on IDDES (Improved Delayed Detached Eddy Simulation)-DPM (Discrete Phase Model) for WSL-dune-sedan-embankment.

Forced-motion simulations of vortex-induced vibrations of wind turbine blades – a study of sensitivities

Abstract. Vortex-induced vibrations on wind turbine blades are a complex phenomenon not predictable by standard engineering models. For this reason, higher-fidelity computational fluid dynamics (CFD) methods are needed. However, the term CFD covers a broad range of fidelities, and this study investigates which choices have to be made when wanting to capture the vortex-induced vibration (VIV) phenomenon to a satisfying degree. The method studied is the so-called forced-motion (FM) approach, where the structural motion is imposed on the CFD blade surface through mode shape assumptions rather than fully coupled two-way fluid–structure interaction. In the study, two independent CFD solvers, EllipSys3D and Ansys CFX, are used and five different turbulence models of varying fidelities are tested. Varying flow scenarios are studied with low to high inclination angles, which determine the component of the flow in the spanwise direction. In all scenarios, the cross-sectional component of the flow is close to perpendicular to the chord of the blade. It is found that the low-inclination-angle and high-inclination-angle scenarios, despite having a difference equivalent to up to only a 30∘ azimuth, have quite different requirements of both grid resolution and turbulence models. For high inclination angles, where the flow has a large spanwise component from the tip towards the root, satisfying results are found from quite affordable grid sizes, and even with unsteady Reynolds-averaged Navier–Stokes (URANS) k–ω turbulence, the result is quite consistent with models resolving more of the turbulent scales. For low inclination, which has a high degree of natural vortex shedding, the picture is the opposite. Here, even for scale-resolving turbulence models, a much finer grid resolution is needed. This allows us to capture the many incoherent vortices, which have a large impact on the coherent vortices, which in turn inject power into the blade or extract power. It is found that a good consistency is seen using different variations of the higher-fidelity hybrid RANS–large eddy simulation (LES) turbulence models, like improved delayed detached eddy simulation (IDDES), stress-blended eddy simulation (SBES) and k–ω scale-adaptive simulation (SAS) models, which agree well for various flow conditions and imposed amplitudes. This study shows that extensive care and consideration are needed when modeling 3D VIVs using CFD, as the flow phenomena, and thereby solver requirements, rapidly change for different scenarios.

Improved Delayed Detached Eddy Simulation of Combustion of Hydrogen Jets in a High-Speed Confined Hot Air Cross Flow II: New Results

The improved delayed detached Eddy simulation (IDDES) approach used in the part I of this investigation to study the self-ignition and combustion of hydrogen jets in a high-speed transverse flow of hot vitiated air in a duct is extended in the following directions: (i) the wall boundary conditions are modified to take into account the optical windows employed in the experiments; (ii) the detailed chemical kinetic model with 19 reactions is used; (iii) a nonlinear turbulence model is implemented in the code to capture the secondary flows in the duct corners; (iv) the wall roughness model is adapted; (v) the synthetic turbulence generator is imposed upstream of the fuel injection. As a result of improving the mathematical and physical problem statements, a good agreement between the simulation and the experimental database obtained at the LAERTE workbench (ONERA) is achieved.

Simulations of Compression Ramp Shock Wave/Turbulent Boundary Layer Interaction Controlled via Steady Jets at High Reynolds Number

Shock wave/turbulent boundary layer interaction (SBLI) is one of the most common physical phenomena in transonic wing and supersonic aircraft. In this study, the compression ramp SBLI (CR-SBLI) was simulated at a 24° corner at Mach 2.84 using the open-source OpenFOAM improved delayed detached eddy simulation (IDDES) turbulence model and the “Rescaling and Recycling” method at high Reynolds number 1.57×106. The results of the control effect of the jet vortex generator on CR-SBLI showed that the jet array can effectively reduce the length of the separation zone. The simulation results of different jet parameters are obtained. With the increasing jet angle, the reduction in the length of the separation zone first increased and then decreased. In this work, when the jet angle was 60°, the location of the separation point was x/δ=−1.48, which was smaller than other jet angles. The different distances of the jet array also had a great influence. When the distance between the jet and the corner djet=70 mm, the location of the separation point x/δ=−1.48 was smaller than that when djet=65/60 mm. A closer distance between the jet hole and the corner caused the vortex structures to squeeze each other, preventing the formation of a complete vortex structure. On the other hand, when the jet was farther away, the vortex structures could separate effectively before reaching the shock wave, resulting in a better inhibition of SBLI. The simulation primarily focused on exploring the effects of the jet angle and distance, and we obtained the jet parameters that provided the best control effect, effectively reducing the length of the CR-SBLI separation zone.

Impact of bogie fairing configuration on the aerodynamic performance of high-speed train under crosswind

In this paper, the unsteady aerodynamic characteristics of a three-car grouped high-speed train (HST) with different bogie fairing configurations under the crosswind are studied using improved delayed detached eddy simulation (IDDES) at Re = 1.85 × 106. The numerical method results are validated against the previous wind tunnel experiments. There are three cases with original half-fairing configuration (HFC), non-fairing configuration (NFC) and full-fairing configuration (FFC), respectively. The numerical results show that the bogie fairing configuration has significant effects. Compared to the HFC case, the drag force coefficients of the head, middle and tail cars with NFC increase by 53.13%, 14.87% and 27.04%, and corresponding parts of the FFC case decrease by 49.98%, 24.40% and 12.41%, respectively. The FFC case can also optimize the pressure distribution on the windward and leeward sides of the HST, and the flow structure and vertex distribution around the car body are also optimized. In addition, the increasing encirclement of the fairing configurations reduces the maximum lateral flow velocity inside the bogie cavities by 70% for HFC and 50% for FFC compared to the NFC. Overall, the FFC presents better aerodynamic performance than the NFC and HFC cases under crosswind, which is recommended for the design of the HST.