Tetsuro Tamura's research while affiliated with Tokyo Institute of Technology and other places

Publications (161)

Article
In the future, skyscrapers or large structures will become lighter and more flexible. In order to clarify the aerodynamic behavior of such structures by wind tunnel test, flexible, low-density square prism models were developed using polyurethane foam. In this report, mechanical properties and bending vibration characteristics of the models are inv...
Article
This study emphasizes the flow mechanism of negative peak pressures on a square-section cylinder at Reynolds number of 22,000, particularly of those immediately upstream of the trailing edges (trailing-edge peak pressure). The minimum trailing-edge pressure coefficients are observed as low as -5 and have a close correlation in a streamwise length o...
Article
This study topologically describes near-wall flows around a surface-mounted cylinder at a high Reynolds number ( $Re$ ) of $5\times 10^4$ and in a very thick boundary layer, which were partially measured or technically approximated from the literature. For complete and rational flow construction, we use high-resolution simulations and critical-poin...
Article
In general, eigenvalue analysis for beams considering rotatory inertia and shear deformation is not trivial, even in the case of uniform beams. In this paper, a practical method is proposed for calculating natural bending frequencies of uniform elastic beams considering rotatory inertia and shear deformation. The proposed method is based on the mod...
Article
There are only few available studies about wind response of base-isolated high-rise buildings. Conventional design wisdom for wind response is to consider peak responses. However, according to observed wind speed and acceleration of a base-isolated high-rise building, the acceleration peak factor is larger than the expected design value. As such, t...
Article
To validate applicability of the novel hybrid meteorological model/engineering LES method to damage estimation of actual tornado events, simulation is performed focusing on the severely damaged area of the strong tornado on May 6, 2012 in the city of Tsukuba with the realistic tornado structure reproduced in the meteorological model, the actual bui...
Article
Full-text available
Large-eddy simulations were used to investigate unsteady flows around a wall-mounted hemisphere as the Reynolds number (Re, based on the diameter of the hemisphere D) increased from 7 × 10⁴ to 7 × 10⁵. The hemisphere was immersed in a low-turbulence-intensity boundary layer with a thickness of δ/D = 0.5. Strong Re dependence was confirmed to be pre...
Article
To evaluate the aerodynamic instability for buildings considering their high-order oscillation mode and torsional oscillation mode on which it is difficult to perform the usual wind tunnel experiments, the fluid–structure interaction (FSI) analysis code combined with a multi-degree-of-freedom structure model and large-eddy simulation was developed....
Article
Turbulent structure derived from meteorological disturbance with low-frequency fluctuation affects different characteristics for the distribution of wind pressure and the peak value of concentration in comparison with the inflow condition using turbulent boundary layer (TBL) over smooth or rough surface in usual cases. However, it is impossible to...
Article
A new hybrid meteorological model/engineering LES method was used to analyze a tornado and near-ground turbulence under realistic conditions. The hybrid method estimates high frequency turbulence regeneration in an actual severe storm that has complex thermal conditions in order to alleviate the problem of high frequency component dissipation in me...
Article
Full-text available
Shear-inflow effects on flows past a rounded-corner square cylinder is investigated when Reynolds number (Re) increases from subcritical regimes (Re=2.2×104) to supercritical regimes (Re=1.0×106), with a focus on the latter Re in this study. The dimensionless shear parameter K ranges from 0 to 1.0. Results show that shear inflows have different eff...
Article
Full-text available
Large-eddy simulations were used to investigate the supercritical aerodynamics of a square cylinder with rounded corners in comparison with those in the subcritical regime. First, the numerical methods, especially the dynamic mixed model, were validated on the basis of their prediction of supercritical flows past a circular cylinder. Then, the supe...
Article
The flow past a square cylinder at Re = 2.2 × 104 is analyzed by large-eddy simulation (LES) using the fine grids in order to represent details of near-cylinder flows. The accuracy of LES on structured and unstructured grids is assessed from the engineering viewpoint, compared with previous studies. The finite differencing method code with 4th orde...
Article
Large Eddy Simulation (LES) is expected to be adopted as an effective technique to evaluate wind load on buildings for wind-resistant design. For numerical prediction of wind forces or pressures by LES, unstructured grid system is effective in terms of flexibility in generating computational models. In this paper, the fluctuating wind forces acting...
Article
Large Eddy Simulation (LES) is expected to be adopted as an effective technique to evaluate wind load on buildings for wind-resistant design. For numerical prediction of wind pressures by LES, unstructured grid system is effective in terms of flexibility in generating computed models. In this paper, the fluctuating wind pressures on a high-rise bui...
Article
In contrast with a wide range of applications concerning flows around a circular cylinder at upper subcritical Reynolds numbers (Re), there is no systematic understanding about the fundamentals of so-called random flow patterns, and their effects on intermittent modulations in the time history of pressure or force, and the decrease in their spanwis...
Article
This paper discusses the applicability of large eddy simulation (LES) to the wind-resistant design of buildings in cities. In order to accurately predict wind pressures and forces on actual buildings with complicated shapes, we partially introduce the unstructured grid system, which is formulated on the open-source CFD code. Applying the LES method...
Conference Paper
Full-text available
In this study, we investigated the influence of an actual urban block area for predicting the wind pressure of a high-rise target building using large-eddy simulations (LES) and high-performance computing (HPC) resources. This study aims to acquire the LES prediction characteristics for a practical wind road design. First, four LES cases were perfo...
Article
p>Recent development of high-performance computers and numerical techniques on wind engineering has enabled us to simulate the complicated flow such as the wind around buildings. Computational Fluid Dynamics (CFD) is expected to be adopted as an applicable technique for evaluating wind load for wind-resistant design of buildings. For numerical pred...
Article
The purpose of this paper is to investigate the characteristics of local severe suction on side face of a three-dimensional square cylinder by LES. According to the previous researches, the occurrence of local suctions at the angle of the attack α=0o, and glancing angle are focused on. First, the computed results for distribution of the pressure co...
Article
This paper carried out LES of the fluctuating wind pressures on a three-dimensional square cylinder for PIV-based inflow turbulence. Numerical simulation has generated inflow turbulence by directly using the stereo PIV measurement data at inflow condition. Since this PIV experiment was executed at low Reynolds number, the Reynolds number of inflow...
Article
Recent development of techniques on computational fluid engineering has enabled us to simulate the complicated flow around buildings. Large Eddy Simulation (LES) is expected to be adopted as an effective technique to evaluate wind load on buildings for wind-resistant design. In this paper, focusing on unstructured grid system, which is effective in...
Conference Paper
Large Eddy Simulation (LES) is expected to be adopted as an effective technique to evaluate wind load on buildings for wind-resistant design. For numerical prediction of wind pressures by LES, unstructured grid system is effective in terms of flexibility in generating computed models. In this paper, the fluctuating wind pressures on a high-rise bui...
Article
Full-text available
抄録 The vertical wind velocity profiles dominate wind loadings acting on tall buildings. By AIJ (Architectural Institute of Japan) Recommendations for Loads on Buildings, velocity profiles are to be prescribed according to terrain conditions. The effects of terrain conditions can be treated by the surface roughness parameters such as the roughness l...
Article
CFD has come to be used in the prediction of wind loads by the development of computer. Wind loads acting on buildings located in turbulent boundary layer are affected by the characteristic of approach flow strongly. Because inflow wind fluctuations affect the results of calculation with CFD, various kinds of methods to generate inflow wind fluctua...
Article
We have conducted LES (large eddy simulation) for turbulent wind flows and dispersion of hazardous gas emitted from a point source on the ground in a large city, Tokyo. Also, for numerical validation, wind tunnel tests using a Dynamic Particle Image Velocimetry (DPIV) and tracer gas measurement system are performed to estimate turbulence statistics...
Article
This study proposes the method of one-way coupling between nested grids with different resolution for LES of turbulent boundary layer. Based on the difference of the momentum equations for the coarse and fine grids, we deduce the equation of the finer-grid component of velocity fluctuations. This equation has two types of SGS stress terms. One is t...
Article
The method for coupling between nested grids is pro-posed for LES turbulent flows. In this method fluctuating ve-locity simulated in a coarse grid is imposed to a fine grid and the grid-scale velocity fluctuation of the fine grid is generated based on the scale similarity model. The a-priori test of a turbulent boundary layer flow over a rough surf...
Article
Full-text available
The purpose of this paper is to investigate the flow mechanism for maximum negative pressure on the upstream area of an elliptic structure by LES analysis, when the oblique flow attacks. First the present LES model is validated for the prediction of the pressure characteristics on a three-dimensional elliptic structure in boundary-layer turbulence...
Article
Full-text available
When a building with viscoelastic dampers is subjected to wind excitations, its dynamic properties such as vibration period and damping ratio can vary, depending on the frequency contents of the excitation. This is due to frequency sensitivity of the viscoelastic damper, and contradicts with the basis of the conventional spectral or modal analysis...
Article
Full-text available
It has been recognized that the viscoelastic damper is effective against not only seismic force but also wind force. However the effect of viscoelastic damper on the wind-induced response has not been fully comprehended. This paper discusses the wind-induced response characteristic of tall building having the viscoelastic dampers based on time-hist...
Article
In order to validate the LES(large eddy simulation) model for strong wind in actual urban area, this research performs the direct comparison between wind data estimated by LES and full-scale measurement data. Generally, LES cannot evaluate the absolute wind velocity, but can only a relative value to the reference wind velocity. In order to introduc...
Article
The measurement wind velocity on the rooftop of the tall building is usually utilized as a reference wind velocity. However, after many new tall buildings have been constructed around the specified tall building, it becomes difficult to use the rooftop data as a reference. While, the wind velocity predicted by the meso-meteorological model (MM5) wi...
Article
Large Eddy Simulation (LES) of turbulent boundary layer flows over small-scale and large-scale homogenous roughness were performed. The turbulent boundary layer flow over small-scale roughness whose roughness height is 0.028delta (where delta is boundary layer thickness) is expected to have outer-layer similarity in the turbulence structure as same...
Article
It is well known that the flow around a circular cylinder in the critical Reynolds number region represents an intricate combination of laminar separation, turbulence transition, reattachment and turbulent separation of a boundary layer on the cylinder. According to previous experimental studies, separation bubbles are formed in association with th...
Article
This paper performs Large-eddy simulation (LES) of gaseous dispersion in the atmospheric convective boundary layer (CBL) which is capped by a temperature inversion. The vertical temperature flux profile becomes negative within the capping inversion, and its negative peak value is indicated due to the entrainment of a plume and its resulting fluctua...
Article
For strong wind problems in the city, we have to consider the effect of turbulence characteristics for the flow field and wind pressure on a building surface. Consequently, we use large eddy simulation (LES) rather than Reynolds averaged Navier–Stokes (RANS) in order to reproduce non-isotropy and non-stationarity of the actual wind flow field. LES...
Article
This paper reviews large-scale computing results currently obtained by the large eddy simulation (LES) technique for various wind engineering problems. The LES or direct numerical simulation (DNS) techniques should be used to numerically simulate unsteady flow phenomena. LES is appropriate for wind engineering applications because its computational...
Article
This paper presents activities of the Architectural Institute of Japan (AIJ) on computational wind engineering, focusing on numerical prediction of wind loads on buildings. It discusses and evaluates current CFD techniques, including LES and modified RANS, for wind-resistant design of actual buildings. It also provides a guide for constructing a nu...
Article
For accurate large eddy simulation (LES) of complex turbulent flows around bluff bodies with various shapes, we have investigated the effects of the upwind scheme on wake structures and the problems in overset grid systems, which require interpolation of physical values between sub-domains. For the former LES of turbulent flows around a circular cy...
Article
Full-text available
Large-eddy simulation (LES) is applied to the problem of plume dispersion in the spatially-developing convective boundary layer (CBL) capped by a temperature inversion. In order to generate inflow turbulence with buoyant forcing, we first, simulate the neutral boundary layer flow (NBL) in the driver region using Lund's method. At the same time, the...
Chapter
In this study, Large Eddy Simulation of a boundary layer flow over large-scale roughness was performed targeting the experiments conducted by Cheng and Castro [2]. In order to duplicate the experimental conditions, the quasi-periodic boundary method for rough-wall boundary flows was applied to the inlet boundary conditions. The characteristics of t...
Article
Concerning the wind resistant problems for buildings and structures, wind tunnel test and numerical simulation have been conducted out of consideration of effect of thermal stratification. However, it is confirmed that the observed wind profile in the typhoons is different from the wind profile in the boundary-layer type of flows and determined by...
Article
The purpose of this paper is to investigate the motion of the conical vortex which lead to the large level of the negative pressure near the leading comer by LES analysis when flow attack oblique to the flat roof. First the present LES model is validated for the prediction of the pressure characteristics on the roof through comparison with the expe...
Article
Large eddy simulation (LES) is carried out to investigate the turbulent boundary-layer flows over a hill-shaped model with a steep or relatively moderate slope at moderately high Reynolds numbers (Re = O(103)) defined by the hill height and the velocity at the hill height. The study focuses on the effects of surface roughness and curvature. For Sub...
Article
The recent advancement of numerical techniques has made it possible to simulate a bluff body wake accompanied with unsteady vortices at relatively high Reynolds numbers. However, even now it is not easy to accurately simulate the flow around a circular cylinder at higher Reynolds numbers especially above the critical Reynolds number. In order to si...
Article
The applicability of the large eddy simulation (LES) technique to wake flows past a bluff body should be clarified in order to improve numerical accuracy for the estimation of aerodynamic forces and pressures acting on a bluff body. Here, we conduct both LES and particle image velocimetry (PIV) measurement for turbulent flows past rectangular cylin...
Article
Large eddy simulation (LES) is carried out to investigate the turbulent boundary-layer type of flows over a hill-shaped model with a steep slope. Also, we focus on the surface condition of a hill, such as vegetation effects as well as curvature effects. In order to model the vegetation effects for LES, we employ the feedback forcing method proposed...
Article
Wind tunnel experiments were carried out to investigate the effects of roughness blocks on the atmospheric boundary layer flow over a two-dimensional low hill with maximum slope 0.21. Roughness blocks whose heights were one eighth of the hill height were arranged in a staggered pattern with a roughness density of 4.1% to model the rough conditions....
Article
Full-text available
This paper discusses the wind tunnel tests for a tall building model having either viscous or visco-elastic damper under the turbulent boundary layer flow. The wind tunnel tests are carried out either the across- or along-wind direction for the viscous and the visco-elastic damper systems, respectively. This wind test set-up includes a special meas...
Conference Paper
Full-text available
Viscoelastic damper dissipates energy through shear deformation of the viscoelas-tic material, and this causes temperature rise and softening of the material. Under long duration load, therefore significant heat conduction and transfer can occur and control the temperature-rise effects. These and frequency sensitivities are considered in the two an...
Article
Wind‐tunnel tests on an aeroelastic building model with viscoelastic dampers are conducted to investigate the vortex‐induced response of a viscoelastically damped building under uniform flows. Performance of the viscoelastically damped model is compared with that of a viscously damped model simulated by the building model with silicone oil. The dam...
Article
In this study, Large Eddy Simulation (LES) of turbulent boundary flows over homogenous roughness were performed using hybrid LES- RANS model which can represent appropriately and efficiently the roughness condition on ground surface[F. Hamba, Theoret. Comput. Fluid Dynamics 16, 387--403 (2003)]. In LES of boundary layer flows over vegetation fields...
Article
Wind tunnel experiments were carried out to study the effects of surface roughness on the turbulent boundary layer flow over a two-dimensional steep hill, accompanied by a relatively steady and large separation, sometimes called a separation bubble. Rough surface conditions were modeled by placing small cubes on the hill surface with an arrangement...
Chapter
In this research, we carry out LES analysis of the spatially-developing stably stratified turbulent boundary layers and investigate the streamwise variation of turbulence structures. To realize it without enormous computational burden, we employ the pseudo periodic condition using the rescale technique for the velocity field in the streamwise direc...
Article
The objective of this paper is to show the applicability of the LES method to the realistic problem such as the vortex-induced oscillation of high-rise RC cylindrical tower in turbulent boundary layer. First, we introduce the numerical method for generating the boundary-layer turbulence to the present LES method. Next, we study the fundamental char...
Article
Large-eddy simulation(LES) is applied to the problem of atmospheric dispersion around a normal plate for oncoming turbulence, which is time-sequentially generated by unsteady numerical simulation of spatially-developing boundary layer in the driver unit as another computational domain. The present numerical model is validated in comparison with the...
Article
This study aims at establishing a numerical simulation method for obtaining high wind data in actual urban area. Height data of surface roughness measured by remote sensing technique are used and can directly express geometrical boundary of the urban areas on the numerical model. We employ LES (large eddy simulation) model for complex turblulent fl...
Article
This paper shows LES analysis of the physical mechanism of vortex-induced oscillation of a three dimensional circular cylinder. First, we discuss the accuracy of the computed results of free-end effect on the wake structures and the distributions of aerodynamic coefficients in the axial direction of a three dimensional stationary circular cylinder....
Article
It is well known the drag coefficients of a rectangular cylinder normal to a uniform stream show a maximum value as high as 2.8 when the side ratio D/B [depth (D) to breadth (B) ratio] is eaual to about 0.6. Its rectangular geometry is called the critical section. In the case of oncoming turbulent flow, the critical section is shifted to a side rat...
Article
This paper discusses the aeroelastic instability of prismatic structures on the basis of the numerical results by large eddy simulation for turbulent flows around a square and a rectangular cylinders. This type of aeroelastic instability is a classical problem continuing for over , so there have been a number of studies to understand the physical m...
Article
Turbulent boundary layer over a steeply curved hill contains the complicated flow phenomena such as the spatial development, separation, reattachment and downstream recovery, and is sensitively influenced by the surface condition, smooth or rough, of the curve. Variation of the wake structure with the surface condition is of particular interest, be...
Article
For aiming at realization of high level applications of CFD techniques to wind-resistant designs, the urban area densely arranged with high-rise buildings are analyzed by the LES which has smaller errors caused from modeling for turbulence than conventional simulations such as RANS and also predicts time fluctuations of strong winds and wind-pressu...
Article
This paper shows LES analysis of turbulence effects on vortex-induced oscillation of a circular cylinder. First, we discuss the accuracy of the computed results of the wake flows and pressure distribution for a stationary circular cylinder in smooth and turbulent flows as a function of Reynolds numbers. Next, the present LES method is applied to th...
Article
Large-scale motions of fully developed turbulent channel flow were numerically investigated for the Re τ of up to 1180 using LES. They were found to be similar to the streak structures near the wall, but their streamwise and spanwise sizes reach about three times and twice as large as the channel-half width respectively independent of the Re τ.
Article
This paper discusses turbulence effects on aeroelastic instability of a square and a rectangular (B/D=2, B:breadth, Drdepth) prisms by large eddy simulation. We show the accuracy of the computed results for a stationary prism in the oncoming smooth and turbulent flows. Next, the simulation applicability to an oscillating prism is examined and the p...
Article
Full-text available
This paper discusses utilization of digital surface model in urban area for wind engineering; for example, estimation of wind profiles in urban area, estimation of wind loads of tall buildings, and so on. Recent advancement for quality of digital surface model makes it possible to construct sophisticated numerical models for wind flows over roughen...
Conference Paper
This study brings into focus the turbulent boundary layer flow over a two-dimensional hill with sinusoidally curved slope, which has both of convex and concave surfaces. In the regions over these two types of surfaces, it is well known that turbulence is deformed and much influenced due to velocity acceleration and deceleration. DNS has been applie...
Article
The objective of this work is to investigate the very large-scale flow structures observed in or above the logarithmic layer of a wall-bounded turbulence and the effect of thermal stratification on these structures. Large eddy simulation (LES) is adopted as a numerical method in this work. We have found that the large-scale structures are similar t...
Conference Paper
Recent advancement of LES (Large Eddy Simulation) technique for turbulent wake has made it possible to numerically investigate the turbulence effects on aerodynamic characteristics of a bluff body. Here we carry out LES of wake flows past a circular cylinder in the subcritical Reynolds number regime. For inflow boundary condition, homogeneous turbu...

Citations

... However, an essential step before that is to decide the sufficiency of the duration by itself before considering other uncertainties. The common practice of checking for adequacy of duration, especially in computational methods, is tracking the residual error in the quantities of interest (Cao et al., 2022). This approach is subjective and challenging to generalize because the error is defined relative to the 'true value,' usually the longest available duration. ...
... A key difference that separates the two studies is that their Reynolds number is an order of magnitude higher. The effects of the Reynolds number on the wake components have been reported by several studies [18][19][20][21]. ...
... where Fd and Fl are the hydrodynamic forces along x-and y-directions of the cylinder are 7 calculated, ρ is the density, U∞ is the free stream velocity. In equation (16), L and D is the 8 streamwise and transverse length of a rectangular cylinder, f is the vortex shedding frequency 9 (Strouhal frequency) which can be identified from the power spectrum analysis using Fast Fourier Cl are derived using equations (17) and (18), where the drag coefficients are derived in a similar 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t Table 3. 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t domains are listed in Table 4. Percentage deviations are also listed in the parentheses. It be found 2 that the deviations of not only the time-averaged quantity, i.e. d C , but also the fluctuations 3 ...
... In addition, the presence of wall introduces a gap flow between the sphere and the wall, which substantially affects the flow dynamics in the sphere wake. Several parameters have been considered to address the interaction of an isolated sphere with wall-bounded turbulent flows, such as sphere Reynolds number, [21][22][23] ambient turbulence intensity, 21 the gap size between sphere and wall, 22,24,25 shear rate, 25 and the relative size of the sphere with respect to the boundary layer thickness, 25,26 the channel half-height, 21,27 or the pipe diameter. 28 Zeng et al. ...
... Huang et al. 18,19 realized the CFD and CSD two-way FSI through socket communication technology and compared the numerical simulation results with the wind tunnel test of CAARC aeroelastic model, which proved the e®ectiveness and accuracy of the two-way FSI method. Hasama et al. 20 established a six degree of freedom numerical model and used the two-way FSI method to simulate the aeroelastic response of a high-rise building with rectangular section side length ratio of 1:2, considering the in°uence of high-order modes. Zhang et al. ...
... However, it is difficult to generate velocity with sufficient fluctuation for reproducing turbulent field around urban canopy. In this study, inflow condition is generated by Kawai and Tamura (2020). In this method, high-frequency component is added to the results of meteorological model (WRF-LES) using the method using spatial filtering and rescaling technique in semi-periodic condition. ...
... These models are clearly over-simplified. The tornado wind fields are also modeled using CFD simulations (e.g., Kuai et al., 2008;Ishihara et al., 2011;Liu and Ishihara 2015;Eguchi et al., 2018;Gairola and Bitsuamlak 2019;Kawaguchi et al., 2019;Huo et al., 2020;Liu et al., 2021) or laboratory tests (e.g., Sarkar et al., 2006;Refan and Hangan 2016;Razavi and Sarkar 2018;Tang et al., 2018;Ashton et al., 2019;Gillmeier et al., 2019;Hou and Sarkar 2020;Razavi and Sarkar 2021). However, CFD simulations of tornadoes are computational expensive while the laboratory tests are labor intensive. ...
... Changes in the landscape have significantly affected wind patterns in urban areas. Flow separations, downwashes, and vortex shedding around buildings are combined (Cao et al., 2019;Sumner et al., 2017;Unnikrishnan et al., 2017;Wang et al., 2006), making the wind environment highly complex in urban areas. Accordingly, human safety and comfort related wind events in urban environments have provoked growing attention in the academic community. ...
... Furthermore, the level of negative pressure somewhat varies along spanwise direction and in time. Cao and Tamura (2018), and is shown in Eqs. (11) and (12). ...