Inflow Turbulence Generation Research Articles

Numerical reconstruction of atmospheric boundary layer seasonal turbulent wind field over a complex forest terrain

The wind characteristics of the atmospheric boundary layer (ABL) over complex forest terrains are inherently intricate, influenced by the interplay of rugged topography, seasonal climatic fluctuations, and periodic vegetation dynamics. These effects are especially evident in the near-ground wind field, which exhibits substantial seasonal variability. Conventional wind characterization methods, as outlined in current standards, often fail to accurately capture these seasonal variations, thereby complicating the reconstruction of the near-ground ABL turbulent wind field in complex forest terrains. Accordingly, we employ the narrow band synthetic random flow generation (NSRFG) technique within large eddy simulation (LES) to generate inflow turbulence representing the growing and baldness seasons in a complex forest terrain by adjusting parameter equations for seasonal adaptation and introducing new empirical equations for the turbulent spectrum. Subsequently, we verified the seasonal turbulent flow's statistical characteristics and flow structure to assess its feasibility and validity, ultimately establishing a ‘seasonal numerical wind field’ model. Finally, the seasonally modified LES-NSRFG method was applied to the numerical simulation of turbulent flow around the Commonwealth Advisory Aeronautical Research Council (CAARC) standard high-rise building model. A comprehensive comparison of wind effects was conducted for the CAARC model under varying incoming flow conditions. The results indicate that seasonal winds in a complex forest terrain significantly affect the building's vortex wake, increasing the irregularity and complexity of the structural wind pressure and base moment coefficients. Thus, the seasonal wind effect must be considered when designing wind-resistant engineering structures in forest regions moving forward.

A new controllable weak recycling inflow turbulence generator for evaluating wind effects on building in LES

The weak recycling method, known as the “rescaling-recycling” method, has been extended to simulate micro-scale turbulent atmospheric boundary layers (ABL) by employing staggered blocks in the developing section, replicating physical ABL wind tunnel setups. However, this method faces challenges, such as the need to re-evaluate the sizes and configurations of roughness elements when addressing different objective structures, computational domain sizes, or ground exposures. To address these issues, we propose a controllable weak recycling (CWR) method for generating turbulent ABL flows over rough surfaces in large eddy simulation (LES). This method can directly produce a turbulent boundary layer with arbitrary target characteristics in a single simulation, significantly enhancing generation efficiency and reducing computational resource consumption. Our refinement method incorporates a feedback proportional control algorithm into the “rescaling” procedure to minimize errors between simulated and targeted turbulence intensities. Besides, an existing drag model is utilized in the near-ground region to maintain horizontal homogeneous ABL flows over rough surfaces. The proposed CWR method is validated by simulating three turbulent ABL flows over various rough terrains using LES. Results confirm that the generated inflow turbulence adheres to prescribed mean velocities and turbulence intensities, demonstrating consistent self-sustainability along the flow direction. Furthermore, the generated wind spectra closely align with the anisotropic von-Kármán spectrum. When applying the extracted wind time histories at the main domain’s inlet, we find that the mean and fluctuating wind pressures on a high-rise building closely match specified wind tunnel test results.

Generation of inflow turbulence using an improved synthetic eddy method

The generation of turbulent inflow conditions is a key issue in large eddy simulation (LES) or direct numerical simulation (DNS). In this paper, an improved synthetic eddy method (SEM) is proposed to generate inflow turbulence for LES and DNS. The improvements about SEM focus on the eddy radius and eddy distributions. First, the eddy radius is improved to reduce the nonphysical vortex structure on the wall caused by overestimation of the radius. Second, a sampling method using Gaussian distribution is proposed to improve the distribution of eddies, which accurately captures the randomness of turbulent structure size and is close to the actual flow field. The improved method is applied to the direct numerical simulation of the supersonic turbulent boundary layer at Mach 2.7 and the 24° compression ramp. Results indicate that the predictions yielded by the improved method are in good agreement with both DNS and experimental data. Compared to the original method, the improved method exhibits a more rapid recovery of the friction coefficient and effectively shortens the development distances. The improved SEM has enhanced the efficiency and accuracy of generating inlet turbulence, which can provide inlet turbulence boundary conditions for LES and DNS.

Inflow turbulence generator for large eddy simulation based on a novel block‐vorticity vortex method: Application on a tall building wind effect

AbstractAccurately simulating turbulent wind fields is a significant challenge in wind engineering. This study proposes a novel block‐vorticity method aimed at overcoming the limitations of traditional turbulence generation methods. By superimposing a blocked vortex field at the inlet boundary of large eddy simulation (LES), the proposed method enables the generation of highly precise and anisotropic turbulent wind fields. To validate the effectiveness of the proposed method, the study investigates wind pressures on a high‐rise building structure and performs a comparative analysis with LES narrowband synthesis random flow generator (NSRFG), traditional LES, and SST k‐ω turbulence inlet models. The results demonstrate that the proposed method can effectively simulate turbulence characteristics of atmospheric boundary layer flow, including vortex structure and stochastic fluctuating wind field. Compared to traditional methods, the wind field characteristics of turbulence intensity, instantaneous vorticity, and turbulence self‐equilibrium had obvious advantages over traditional methods. Moreover, the LES vortex method is more accurate in simulating the mean wind pressure and fluctuating wind pressure of the high‐rise building compared to traditional models and is closer to the wind tunnel test results. The proposed method provides an effective approach for generating turbulent wind fields with anisotropic characteristics and can be used to predict the wind‐induced response of civil engineering structures.

A new probability-distribution scale synthetic eddy method for large eddy simulation of wind loads

The accurate generation of inflow turbulence in large eddy simulation (LES) plays a crucial role in assessing the wind loads on buildings. To faithfully recreate turbulent flow fields, the inflow turbulence must accurately replicate vortex structures. In this study, we propose a novel method for generating turbulent inflow called the probability-distribution scale synthetic eddy method (PDSSEM). PDSSEM utilizes a random generation of eddy positions, with the length of each eddy scale determined by its probability density function (PDF). This approach ensures that PDSSEM maintains consistency in the mean wind speed profile, turbulence integral length, turbulence intensity profile, and wind speed spectra of the atmospheric boundary layer (ABL). The PDSSEM method can be more easily applied compared with multi-scale synthetic eddy method (MSSEM), making it highly versatile and adaptable. The self-sustaining characteristics of the flow field generated by PDSSEM are validated, revealing abundant vortex structures and good agreement with targeted values for turbulence flow characteristics. Furthermore, comparing the wind pressures of a tall building with the experimental data, the accuracy and feasibility of PDSSEM are comprehensively demonstrated. Thus, it indicates the great potential of the proposed method for broader computational wind engineering applications, including wind load evaluation and flow pattern investigation.

Inflow turbulence generation for compressible turbulent boundary layers

It is still challenging to generate high-quality inflow turbulence for the direct numerical and large-eddy simulations of compressible turbulent boundary layers (CTBL). Recently, Wang et al. [“Inflow turbulence generation using an equivalent boundary layer model,” Phys. Fluids 35, 075110 (2023)] proposed a new inflow turbulence generation method based on an equivalent boundary layer model for incompressible turbulent boundary layers. In the present study, the compressible equivalent boundary layer (CEBL) model is proposed and applied to the direct numerical simulation of supersonic turbulent boundary layers. The streamwise equilibrious CEBL approximates the streamwise developing CTBL by adding source terms to the governing equations to recover the mean mass, momentum, and energy balances at a given Reynolds number. Direct numerical simulation is performed to CEBL at free-stream Mach number 5.86 and friction Reynolds number 380. Comparison with the CTBL statistics at the same parameters validates the fidelity and reliability of the CEBL model. Turbulence generated by CEBL as well as the digital filtering and recycling-rescaling methods is used, respectively, to construct the inflow conditions for the direct numerical simulation of supersonic turbulent boundary layers. Results show that the CEBL method has great superiority in reducing the adjustment length compared with the other two methods. In addition, a correction method designed for the high inflow Reynolds number is also introduced.

On the settling of a spherical particle in slightly perturbed ambient fluid

Direct numerical simulations of the settling of a spherical particle under the action of gravity in a slightly perturbed ambient fluid have been performed. The ambient perturbations are generated using a synthetic turbulence inflow generator method, and their length scale and intensity are varied to study their influence on the particle motion. The Galileo number is 151 and the solid-to-fluid density ratio is 1.5, so that in the absence of perturbations, the particle settles following a steady vertical trajectory. It has been found that the ambient perturbations trigger the formation of double-threaded vortical structures in the wake of the particle. These structures resemble those that appear in the oblique oscillating regime that is found in the absence of perturbations at higher Galileo numbers. Due to the flow perturbations the particle is pushed randomly in all directions, and this results in a combination of slow lateral drifts along fixed directions and relatively fast excursions in random directions. The particle response has been characterized using probability density functions of the velocity in the cross-plane and persistence probability. The slow drifts are strongly influenced by the size of the perturbations and by the rotational motion of the particle, while the intensity of the perturbations seems to play a minor role.

Prospect of LES for predicting wind loads and responses of tall buildings: A validation study

Wind load evaluation on buildings using large-eddy simulation (LES) poses several critical challenges. The most notable ones include accurately reproducing the approaching atmospheric boundary layer flow conditions and modeling massively separated flows around buildings. This study investigates the capability of LES for predicting cladding and overall loads on a tall building by addressing these key challenges. The results from LES are systematically validated against boundary layer wind tunnel measurements. The validation process unfolds in three key stages. Firstly, the approaching wind profiles were reproduced in LES by integrating a recently developed synthetic inflow turbulence generator with an implicit ground roughness modeling technique. Then, the statistics of the cladding and global loads were compared with the experiment for representative wind directions. Finally, the performance of the LES for predicting wind-induced response is examined, assuming typical structural properties for the building. Overall, the results obtained from each validation step showed encouraging agreement with the experimental measurement. In light of the findings from the current study, it is evident that LES is progressively realizing its potential to be a practical wind load evaluation tool. Selected simulation cases used in this study are available at .

A coherence-improved and mass-balanced inflow turbulence generation method for large eddy simulation

Realistic inflow turbulence is crucial in large eddy simulations for obtaining accurate results. In this paper, an improved inflow turbulence generation method is proposed, called the coherence-improved and mass-balanced random flow generation (CMRFG) method. First, a study of the effect of the inlet mass-balanced condition is presented. Subsequently, the proposed method is explicitly deduced to satisfy arbitrary spatial coherence functions and the mass-balanced condition, so the generated turbulent fields effectively preserve the original turbulence characteristics, eliminating the need for additional inlet mass flux corrections. Meanwhile, the novel method retains the advantages of the previous method, satisfying arbitrary turbulence intensities, temporal spectra, temporal correlations, and spatial correlation coefficients. Additionally, the proposed method also ensures compliance with the divergence-free condition and Taylor's frozen hypothesis, which are essential for accurate flow field development. Finally, large eddy simulations of both homogeneous isotropic and anisotropic turbulent fields demonstrate that the turbulent fields generated by CMRFG closely align with experimental results and exhibit no artificial pressure fluctuations within the computational domain.

Applicability of Methods for Inflow Turbulence Generation Developed in a CFD Field to the Thermally Driven Convective Boundary Layer Simulations

Abstract This study focuses on the application of two standard inflow turbulence generation methods for growing convective boundary layer (CBL) simulations: the recycle–rescale (R-R) and the digital filter–based (DF) methods, which are used in computational fluid dynamics. The primary objective of this study is to expand the applicability of the R-R method to simulations of thermally driven CBLs. This method is called the extended R-R method. However, in previous studies, the DF method has been extended to generate potential temperature perturbations. This study investigated whether the extended DF method can be applied to simulations of growing thermally driven CBLs. In this study, idealized simulations of growing thermally driven CBLs using the extended R-R and DF methods were performed. The results showed that both extended methods could capture the characteristics of thermally driven CBLs. The extended R-R method reproduced turbulence in thermally driven CBLs better than the extended DF method in the spectrum and histogram of vertical wind speed. However, the height of the thermally driven CBL was underestimated in about 100 m compared with the extended DF method. Sensitivity experiments were conducted on the parameters used in the extended DF and R-R methods. The results showed that underestimation of the length scale in the extended DF method causes a shortage of large-scale turbulence components. The other point suggested by the results of the sensitivity experiments is that the length of the driver region in the extended R-R method should be sufficient to reproduce the spanwise movement of the roll vortices. Significance Statement Inflow turbulence generation methods for large-eddy simulation (LES) models are crucial for the better downscaling of meteorological mesoscale models (RANS models) to microscale models (LES models). Various CFD methods have been developed, but few have been applied to simulations of thermally driven convective boundary layers (CBLs). To address this problem, we focused on a method that recycles turbulence [the recycle–rescale (R-R) method] and another method that synthetically generates turbulence [the digital filter–based (DF) method]. This study extends the R-R method to manage turbulence in thermally driven CBLs. In addition, this study investigated the applicability of the DF method to thermally driven CBL simulations. Both extended methods are effective for downscaling experiments and capture the characteristics of thermally driven CBLs.

Analysis of improved digital filter inflow generation methods for compressible turbulent boundary layers

We propose several enhancements to improve the accuracy and performance of the digital filter turbulent inflow generation technique and assess their efficacy in the context of wall-resolved large-eddy simulations of a compressible turbulent boundary layer. Improvements of accuracy include a more realistic correlation function for the transversal directions, target length scales that vary with wall-distance, and a counter-intuitive approach that involves the suppression of streamwise velocity fluctuations at the inflow. For improving the computational performance, we propose to generate the inflow data in parallel in single precision and at a prescribed time interval based on the turbulence time scale, and not at every time-step of the simulation. Based on the results of 7 wall-resolved large-eddy simulations, we find that the new correlation functions and the considered performance improvements are beneficial and therefore desired. Suppressing streamwise velocity fluctuations at the inflow leads to the fastest relaxation of the pressure fluctuations; however, this approach increases the adaptation length defined in terms of compliance with the von Kármán integral equation. The adaptation length can be shortened by artificially increasing the wall-normal Reynolds stresses, thereby preserving the desired turbulence kinetic energy level. A detailed inspection of the Reynolds stress transport budgets reveals that the observed spurious spatial transients are largely driven by pressure-related terms. For instance, increased values of u′p′¯ are found throughout the computational domain when a physical Reynolds stress distribution is prescribed at the inflow. Therefore, efforts to enhance digital filter techniques should aim at modeling pressure fluctuations as well as their correlation with the velocity components.

A Turbulent Inflow Generation Method for the LES of High Re Flow by Scaling Low Re Flow Data

The rescaling–recycling method (RRM) is usually used to generate turbulent inflow for the LES of compressible wall-bounded flows, which can lead to relatively high computational cost for high Re flows since the mesh resolution increases exponentially with Re number. A turbulent inflow generation method based on the scaling of low Re flow, referred as TIG-LowRe, is proposed, aiming at reducing the computational cost when applying the RRM. To validate the proposed method, the TIG-LowRe method was applied to generate turbulent inflow for the LES of a non-isothermal round jet flow at Re = 86,000. Two cases were carried out with the inflow generated based on two round pipe flows at Re = 10,000 and 24,000. The results show that the mean and fluctuating temperatures of the two cases agree well with the experimental data. In the case of low Re flow at Re = 10,000, the jet flow decays too fast along the axial direction, the mean and fluctuating axial velocities are over-predicted and the radial fluctuating velocity is under-predicted. By increasing the Re of the low Re flow to 24,000, the decay rate of the jet flow decreases and the accuracies of the mean and fluctuating axial velocities are obviously improved, while the radial fluctuating velocity shifts further away from the experimental data. The main reason for the difference between the two cases is that more fine turbulent structure of the inflow in case-Re10000 is lost than in case-Re24000 during the turbulence generation process.

Inflow turbulence generation using an equivalent boundary layer model

Eddy-resolved simulation of external flow usually requires inflow boundary conditions representing a turbulent boundary layer (TBL) flow, and the quality of the inflow turbulent fluctuation directly impact the accuracy and the cost of the simulation. The present study proposes a new method to generate TBL inflow turbulence, i.e., the equivalent boundary layer (EBL) model. Based on the open-channel model, EBL approximates TBL flow at a given Reynolds number by recovering the mean momentum balance with driving force. It simulates streamwise homogeneous turbulence, applying periodic boundary conditions and, thus, overcomes the complexity and artificiality incurred by the classic recycling–rescaling methods. The current paper discusses the difference between turbulent channel and boundary layer flows from the equation point of view and designs the driving force corresponding to the mean inertial force of boundary layer. Also, the total shear stress models for obtaining the driving force are validated both a priori and a posteriori. Direct numerical simulations (DNS) are carried out for EBLs at Reθ=1000,1420, and 2000 (where Reθ is the Reynolds number based on the momentum thickness), showing that the EBL model well reflects the statistical characteristics of TBL at corresponding Reynolds numbers. The application of the EBL model for the generation of inflow turbulence is also demonstrated by DNS of turbulent boundary layers with inlet Reθ=1000,1420, and 2000. The computational results agree well with generally acknowledged DNS data published in the literature, in terms of streamwise developing statistics, and profiles and energy spectra at characteristic cross sections. Judging from the mean velocity, the adjustment section is shorter than one boundary layer thickness.

Reynolds stresses and turbulent heat fluxes in fan-shaped and cylindrical film cooling holes

Large eddy simulation (LES) is carried out to predict the thermal performance, unsteady flow patterns, and turbulence characteristics of the fan-shaped hole and the cylindrical hole cooling films. Velocity fields, Reynolds stresses, and turbulent heat flux distributions are the factors that ultimately determine the film cooling effectiveness by deciding the concentration of coolant and heat near the surface. Accurate prediction of these processes can provide a reliable data set for the design of film cooling systems. It can also help solve difficulties of improving RANS-based simulations in terms of their inaccuracies in matching measured flow rates for a given pressure drop across the film and the mixing process once the coolant is ejected from the film. Credible estimates and modest costs of the current LES originate from the multiblock hexahedra meshing, the turbulence inflow generator, and the numerical schemes implemented. Multiblock hexahedra meshes are adopted and generated by a quasi-automatic mesh generation algorithm utilizing template-based multi-block construction followed by elliptic smoothing. Computational resources are utilized in a way that mesh refinement exists only near cooling decorations of small size and wall boundaries, without the need for associated clustering in the far field which is commonly used in commercial packages. The high orthogonality and continuous smoothness throughout the computational domain are maintained to facilitate turbulence capturing. The synthetic inflow generator produces a random field matching a realistic set of two-point statistics based on eigen-reconstruction in a computationally inexpensive processing step. To prove that the current LES simulations of modest cost can reproduce with high accuracy, the discharge characteristics, velocity, and turbulence intensity profiles of cylindrical and fan-shaped cooling films are compared with published measured data on the same flow configurations. Results reveal that the set of modeling methodologies is valid for calculating film-cooling performance within an acceptable range of accuracy. The energy-carrying turbulence structures in and near the cooling holes are shown and their behaviors are linked to turbulent Reynolds stresses. Reynolds stresses and turbulent heat fluxes are compared for different blowing ratios and two types of cooling holes in the parametric study. Similarity patterns of velocity profiles, non-dimensional temperature profiles, Reynolds stress and turbulent heat flux profiles are discussed.

Investigation of peak wind loading on a high-rise building in the atmospheric boundary layer using large-eddy simulations

Significant negative peak pressures have been observed in two recent wind tunnel experiments of a high-rise building for certain wind directions. This peak wind loading is crucial for the design of cladding systems. However, the governing flow physics is not well understood. In this study, large-eddy simulations with sufficient resolution are performed to capture and analyze these peak pressure phenomena. The atmospheric boundary layer flow is generated using a divergence free synthetic turbulence inflow generator before the high-rise building is placed in the flow at various wind directions. The mean, standard deviation, and peak pressure coefficients are shown to agree well with the experimental measurements. The strongest negative peak pressures near the top trailing corner on the leeward surface are captured by simulations with the resolved scale between the Taylor microscale and Kolmogorov scale. The probability density function of the pressure at the top trailing corner is well approximated using a log-normal distribution, which is a signature of the effect of small-scale turbulence intermittency. Flow visualization indicates that the strong negative peak values result from the interaction between small eddies shed from the separated flow region at the upwind roof edge and larger eddies downstream of the leeward roof edge.

Direct numerical simulation of hypersonic wall-bounded turbulent flows: An improved inflow boundary condition and applications

In this paper, the method of generating inflow turbulence based on turbulence fluctuation library (TFL) in direct numerical simulation (DNS) of the hypersonic turbulent boundary layer (TBL) is investigated. The application of the TFL method to the DNS of a supersonic TBL shows that, although there are significant differences in freestream between the TFL and the target TBL, the flow could successfully develop to the target TBL downstream as the fluctuations of TFL are suitably scaled and added to the DNS inflow. However, there is a “transition”-like recovery process from the inflow to the target turbulence. To deal with the defects of the thermodynamic fluctuations scaling laws in the current TFL method under the hypersonic TBL, new thermodynamic fluctuations scaling laws are theoretically derived by introducing the generalized Reynolds analogy. The application in the DNS of Mach 7.25 TBL shows that the new scaling laws for thermodynamic fluctuations are more rational and accurate than the previous ones. Furthermore, the study on the recovery process shows that the matching degree between the TFL and the target TBL on the friction Reynolds number (Reτ) is the dominant factor in determining the length of recovery distance. Guaranteeing the similar Reτ of the TFL and the target TBL can make the two possess similar coherence structures, which can avoid the distortion of the coherence structures at the inflow after spanwise and normal interpolation, prevent the process of Reynolds stress decay and readjustment downstream the inflow, and finally effectively shorten the recovery distance.

Turbulent Inflow Generation for Large-Eddy Simulation of Winds around Complex Terrain

Accurate turbulent inflow conditions are needed to broaden the application of the large-eddy simulation technique to predict winds around arbitrarily complex terrain. We investigate the concept of buoyancy perturbations with colored noise to trigger turbulence in upstream flows approaching complex terrain regions. Random perturbations are imposed on the source term in the pseudo-temperature transport equation. These perturbations are effective within three-dimensional boxes and scaled using a bulk Richardson number defined for each box. We apply the turbulent inflow generation technique to predict winds around the Askervein and Bolund Hills under neutrally stratified conditions. We find that a common value for the bulk Richardson number works well for a variety of flow problems. Additionally, we show that the height of the perturbation box plays an important role in the accuracy of the predictions around complex terrain. We consistently obtained good results for both simulation cases when the perturbation box height was made a fraction of the Obukhov length scale.

Divergence-free turbulent inflow data from realistic covariance tensor

Scale-resolving computational fluid dynamics (CFD) methods require carefully constructed boundary conditions to produce accurate results. The inflow data should be unsteady and the successive realizations must follow specific statistics while ideally having a particular correlation in both space and time. A method for generating synthetic correlated stochastic data from uncorrelated sequences is detailed and applied to the problem of inflow turbulence generation for CFD simulations. The technique constructs divergence-free anisotropic random fields with the sensible spectrum and complete complex correlation in space and time. A realistic two-point correlation tensor is inferred from first and second moments and a set of heuristic recommendations based on turbulent flow observations. These statistics are readily available in most practical cases making the technique highly versatile. The approach is computationally efficient with the use of eigendecomposition to reduce the resources required depending on the accuracy needed. Demonstration of the method is provided with the simulation of a turbulent channel flow and a square duct flow, and validation is done against existing numerical data.

Large eddy simulation of turbulent atmospheric boundary layer flow based on a synthetic volume forcing method

A popular inflow turbulence generation (ITG) method is the synthetic random Fourier method because of its concise principle and high computational efficiency. However, the turbulent velocity in this method can hardly satisfy the Navier-Stokes (NS) equation, which usually leads to the re-development of the inflow turbulence field and attenuation of the turbulent energy in the downstream region. To overcome these problems, a synthetic volume forcing (SVF) method that constructs volume forces based on synthetic random Fourier method is proposed in this study. The volume forces can directly import turbulent energy into the mean flow to generate specified turbulent atmospheric boundary layer (ABL) flows by acting as the source terms of the NS equation. Turbulent ABL flows over rural, suburban, and urban terrains are simulated by ITG and SVF methods in the LES model. The results indicate that in SVF cases, the turbulent ABL flows meet the predefined mean velocity, turbulence intensity, and spectrum. The validations in ITG and SVF cases show that the turbulent flows in later cases are compatible with the divergence-free condition and flow dynamics described by the momentum equations, indicating that they have good self-sustainability along the flow direction and do not lead to abnormal pressure fluctuations.

An improved inflow turbulence generator for large eddy simulation evaluation of wind effects on tall buildings

Accurate inflow turbulence wind profile is a key premise of large eddy simulation (LES) methodology for super tall buildings. This paper presents an improved method for narrow band synthesis random flow generation to produce a more accurate inflow turbulence of LES based on superposition of harmonics. The proposed method considers time correlation by adopting time parameters, and an accurate expression of wind speed spectrum energy by a modified spectrum integral equation is used. These improvements could generate a more accurate turbulence intensity for the atmospheric boundary layer. A simple numerical example is applied to verify the spectrum characteristic, time correlation and spatial correlation of atmospheric numerical boundary layer. Meanwhile, the effects of the introduced parameters are investigated and the method is applied to the LES of the Commonwealth Advisory Aeronautical Research Council building (CAARC). The improved method could increase the accuracy of simulated turbulence intensity. Compared with the results of CAARC model obtained from the wind tunnel test, the improved method in this study decreases the errors of root-mean-square (rms) of the based bending moment from 5.3% to 4.1% in the along-wind direction and from 5.6% to 1.3% in the cross-wind direction.