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Publications (503)
Turbulence effects on the aerodynamics of a square cylinder have been widely investigated due to their fundamental significance in both flow physics and engineering applications. However, the influence of large-scale turbulence on shear layer unsteadiness, and its consequences on flow structure and aerodynamic forces has received insufficient atten...
The coupling between sound and flow likely influences the aerodynamics of bluff bodies, which deserves in-depth investigations. This paper presents a comprehensive experimental study of the effects of sound on the near wake flow and aerodynamic forces of a finite three-dimensional (3D) square cylinder in smooth flow and grid-generated turbulent flo...
The knowledge of aerodynamic forces has important implications for the wind‐resistant design of tall buildings. At present, the aerodynamic characteristics of conventional rectangular‐shaped tall buildings have been extensively studied, while those of irregular‐shaped tall buildings have received relatively less attention. Therefore, in the current...
In this paper, 17 severe typhoons that have affected Hong Kong are simulated using an advanced numerical atmospheric simulation system - Weather Research and Forecasting model (WRF). The simulated surface pressure and wind fields of these typhoons are validated against a wide range of field observations. Then azimuth-dependent models for the radius...
The coupling effects between sound and flow on the aerodynamic characteristics of bluff bodies are commonly encountered in engineering practices, such as wind turbine blades and heat exchanger compressors. This study experimentally investigates the effects of sound over a broad range of frequencies (0–400 Hz) and sound pressure levels (80–105 dB) o...
Detailed wind pressure information plays a critical role in the accurate estimation of wind loads on high‐rise buildings, especially for complex‐shaped supertall buildings. However, owing to the limited internal space of a scaled building model and the capacity of data‐acquisition devices, it is often difficult to acquire the wind pressures at all...
Understanding the fluid dynamics and thermodynamics in the urban atmospheric boundary layer (ABL) is of great practical importance. Based on one-year observations from two advanced remote sensing instruments, namely, the wind lidar and the microwave radiometer, this study investigates the urban ABL structure in a densely built downtown area of Hong...
The aerodynamic characteristics of a square cylinder in streamwise sinusoidal flows with non-zero mean velocity are investigated numerically by large eddy simulation. The ratio of the inflow frequency f u to the natural Karman vortex shedding frequency f v s varies from 0.125 to 8. The inflow fluctuating intensity varies from 5% to 20%. The aerodyn...
In structural health monitoring (SHM), wind field monitoring sometimes suffers from data loss owing to monitoring device failure, which inevitably creates barriers to subsequent data analysis and data mining. To this end, a novel strategy for reconstructing missing wind field data based on machine learning (ML) utilizing limited wind pressure measu...
Computational fluid dynamic (CFD) has not been widely accepted as a design tool in current wind‐resistant structural design practices due to its contentious accuracy. To promote the application of CFD in wind‐resistant structural design, the accuracy of CFD should be comprehensively validated. However, most previous validation studies were focused...
This paper investigates the influence of the inflow turbulence integral length scales on the aerodynamic forces on a surface-mounted finite-length square prism and its displacement responses by computational fluid dynamics simulations. Four turbulent inflow conditions with the same mean wind speed and turbulence intensity but different longitudinal...
The present study investigates the aerodynamic characteristics of a square cylinder subjected to transverse oscillating flows. The inflow oscillating frequencies range from 0.25 to 2.00 times the natural Karman vortex shedding frequency. The inflow oscillating intensities are within 5%–20%. Flow resonance between the inflow oscillation and Karman v...
This paper presents an environment-driven tropical cyclone (TC) model for the Western North Pacific basin, which comprises a revised Poisson regression genesis model, a tailored beta-advection track model, and a fast intensity model. The TC model reproduces the temporal and spatial distributions of genesis events, the motion pattern of tracks, as w...
Urban wind power is an appealing alternative for electricity supply. Comprehensive urban wind resource assessment is a prerequisite for cost-efficient deployment of wind turbines. Based on observations from multiple instruments, including a Doppler lidar (light detection and ranging) system, a microwave radiometer, and a cup anemometer/wind vane se...
In operational modal analysis (OMA), only structural responses are typically available. In this context, bias and variance (uncertainty) errors may exist in modal estimates (especially damping estimates), resulting in inaccurate determination of the modal properties of large‐scale structures under harsh excitations. To this end, a hybrid OMA framew...
Since 2011, routine reconnaissance has been carried out whenever there is a tropical cyclone (TC) entering the Flight Information Region of Hong Kong that may pose a threat to the territory. In October 2022, Typhoon Nesat entered the northern part of the South China Sea and aircraft reconnaissance flights were conducted for the storm. This paper pr...
Dust devils at Hong Kong International Airport in two consecutive days in the summer of Hong Kong are documented. They are found to be related to the sea breeze convergence lines and are anticyclonic. The background meteorological conditions under which the dust devils occur are documented. The computer simulation of the tiny anticyclonic flow at t...
Extensive surface and upper air measurements of a typhoon over the northern part of the South China Sea, namely, Typhoon Talim in July 2023, are documented and analysed in this paper. A number of features have been observed from the upper air measurements. First, the log law and the power law were found to be appropriate in fitting the wind profile...
In operational modal analysis, typically only structural responses are available. Errors and uncertainties may exist in modal estimates, thereby leading to discrepancies in the results by different modal identification approaches even analyzing the same data set. To this end, a synergistic usage of multiple stabilization diagram-based modal identif...
Extensive surface and upper air measurements of a typhoon over the northern part of the South China Sea, namely, Typhoon Talim in July 2023, are documented and analyzed in this paper. A number of features have been observed from the upper air measurements. First, the log law and the power law are found to be appropriate in fitting the wind profiles...
Accurate and reliable assessment of wind energy potential has important implication to the wind energy industry. Most previous studies on wind energy assessment focused solely on wind speed, whereas the dependence of wind energy on wind direction was much less considered and documented. In this paper, a copula‐based method is proposed to better cha...
On the basis of two-year-long structural health monitoring data, this paper investigates the structural dynamic properties of a 600-m-high supertall building installed with an active tuned mass damper (ATMD) system. The long-term modal parameters such as natural frequencies and damping ratios of the monitored skyscraper are first determined by the...
Harvesting renewable wind energy is among the most cost-efficient means of reducing carbon emissions and achieving carbon neutrality. However, wind resource is susceptible to climate change impacts since the global temperature increase will reshape atmospheric circulation patterns. To facilitate the evaluation of fine-scale wind energy potential un...
K. K. Hon P.W. Chan L Li- [...]
Mausam IMD
As a follow-up study of the observation of tiny anticyclones by short range LIDAR at the Hong Kong International Airport, super high model numerical weather prediction model simulation of the airflow is performed at a spatial resolution of 50 m. The simulation successfully captures the tiny anticyclonic flow, suggesting that such flow could partly...
Accurate assessment of wind energy potential can provide important implication regarding the optimalization of micro-siting of wind turbines and increase of wind power generation. It is, however, noteworthy that most previous studies on wind energy resource assessment focused solely on wind speed, whereas the dependence of wind energy on wind direc...
Wind pressures on cladding of a 600-m-high skyscraper during Super Typhoon Mangkhut were monitored by a synchronous monitoring system including 48 pressure transducers. Then, simultaneous wind pressure measurements on a 1:500 scale model of the skyscraper were conducted in wind tunnel test. The field measurements of wind pressures are further analy...
In long-term field measurements and structural health monitoring (SHM), data loss sometimes occurs due to interruption of power supply, sensor failure, and disruption of data transmission, which inevitably affects subsequent data analysis and structural condition assessment. To address this issue, this paper proposes a novel data recovery method ba...
In this paper, comprehensive field measurements were conducted on a 600-m-high skyscraper in Shenzhen during Typhoon Kompasu based on structural health monitoring (SHM) system and a remotely non-contact interferometric radar system called IBIS-FS. The SHM system recorded wind field and structural responses, including accelerations at 10 building he...
Waterspout in Macao on 1 June 2021 (provided by radio station of Macao). image
Tiny anticyclonic vortices have been observed at the arrival runway corridor to the east of the central runway of the Hong Kong International Airport many times. However, it is not sure about the cause of such vortices. In this paper, a meteorological model is coupled with a computational fluid dynamics (CFD) model in high spatial resolution in an...
From a practical standpoint, the 1/7th power law has been extensively used for wind speed extrapolation in wind energy community. However, numerous studies have suggested that unrestricted use of the 1/7th power law can be sometimes misleading due to the highly variable nature of wind shear. Hence, the main goal of this study is to unveil the wind...
Despite a large volume of preceding studies on the effects of free-stream turbulence (FST) on the aerodynamic forces of a square cylinder, limited knowledge is available regarding the evolutionary characteristics of flow with the change of turbulence integral length scale and turbulence intensity. This paper presents a systematic experimental study...
The information on long-term modal properties of civil structures under environmental and operational variations is generally required in structural health monitoring and vibration control. In operational modal analysis (OMA), damping estimates usually present larger fluctuations and uncertainties than natural frequency and mode shape estimates, wh...
Recently, the empirical wavelet transform technique has attracted much attention due to its advantage of dealing with non-stationary and nonlinear signals. For empirical wavelet transform-based methods, their performance is heavily dependent on the accuracy of Fourier spectral segmentation. Structural response signals of high-rise buildings under a...
Tall buildings are usually considered as wind-sensitive structures. While extensive studies have been conducted concerning the wind load characteristics on tall buildings, the effect of façade appurtenances has not been fully understood. In this study, a 1:300 scaled CAARC (Commonwealth Advisory Aeronautical Research Council) standard tall building...
This paper investigates the effects of free-stream turbulence such as longitudinal turbulence intensity (I u ) and integral length scale (L x u ) on the flow fields around, and aerodynamic pressures and forces on a surface-mounted three-dimensional (3D) square cylinder with a height-to-width ratio of 5. The flow fields, aerodynamic pressures and fo...
Equivalent load cycle sequence (ELCS) is important basic information to know that affects the reliability of the evaluation of wind-induced fatigue on metal roof claddings. In this study, an estimation method of wind-induced fatigue of metal roof claddings is proposed. Based on the measured wind pressure–time history data of the roof claddings on a...
Wind energy is a mature and cost-effective solution to greenhouse gas emission reduction and climate change mitigation. Wind resource assessment is the most pivotal activity before wind farm development since it determines the bankability of the wind project. Based on the joint use of a Doppler wind sodar (sonic detection and ranging) system and a...
Monitoring of horizontal displacement is essential for structural health monitoring of high-rise structures. This paper proposes a new technique for estimating the horizontal displacement using fusion measurements including strain and acceleration for high-rise structures. The quasi-static component of structural displacement is first derived from...
Structural modal parameters of high-rise buildings during severe winds generally exhibit time-variant features, which conflicts with the assumption adopted in the wind-resistant design procedure that the modal parameters are time-invariant values. This may lead to inaccurate estimation of wind-induced structural dynamic responses, thus deterioratin...
The key meteorological observations of a very late‐season super typhoon over the northern South China Sea, namely, Rai in December 2021, are documented in this article for later reference. In particular, the very valuable dropsonde data in this season are presented. Meteorological data revealed the interaction between the northeast monsoon from the...
Flow separation and reattachment over bluff bodies has been a primary concern in wind engineering community as it may generate large suction pressure. This study re-visits the characteristics of wind pressure underneath the separated shear layer, with emphasis on diagnosing the underlying dynamic properties. Nonlinear dynamic analysis techniques, n...
In recent years, machine learning (ML) techniques have been used in various fields of engineering practice. In order to evaluate the feasibility of machine learning algorithms for prediction of wind-induced effects on high-rise buildings, four machine learning algorithms including ridge regression, decision tree, random forest and gradient boosting...
The assumption of neutral atmosphere in conventional evaluation of air ventilation and thermal stress in a compact urban area with weak wind environment may lead to errors. To assess this effect, this paper presents air ventilation and thermal stress assessment in a real subtropical urban area in Hong Kong by large eddy simulation considering stabl...
A tornado/waterspout associated with a supercell thunderstorm was observed in the adjacent waters of southern China on the evening of 18 April 2019. The case was documented using surface weather observations and Doppler radar data. A weather station near the tornado/waterspout, recorded wind gusts corresponding to hurricane intensity for a few seco...
For high-rise buildings subjected to typhoon or earthquake actions, the excitations are likely non-stationary, which inevitably violates the stationary assumption that is generally adopted by conventional modal identification methods. Under such a condition, conventional modal identification methods may not be applicable, and their performances nee...
The subspace state-space system identification method has drawn extensive attention in structural modal identification, which is generally involved with the stabilization diagram for estimating structural modal parameters. However, the conventional stabilization diagram has an inherent problem, i.e., some spurious modes may be identified as stable...
Accurate information on wind gusts is of critical importance to various practical problems. In this study, observational wind data from high-frequency response (i.e., at a sampling rate of 10 Hz), ultrasonic anemometers instrumented at four different heights (i.e., 10 m, 40 m, 160 m, 320 m) on a weather tower were collected. The observation site fe...
Knowledge of tropical cyclone (TC, or typhoon, hurricane) boundary layer over land is of vital importance to a variety of applications such as track and intensity forecasts of TCs and design of civil structures and infrastructures. On the basis of the 356-m-high Shenzhen Meteorological Gradient Tower which is the tallest of its kind in Asia, this p...
This study aims to examine the feasibility of predicting surface wind pressure induced by conical vortex using a backpropagation neural network (BPNN) combined with proper orthogonal decomposition (POD), in which a 1:150 scaled model with a large-span retractable roof was tested in wind tunnel under both laminar and turbulent flow conditions. The d...
Vertical profiles of tangential and radial wind speeds in Cyclone Mangkhut at 0900–1200 utc 15 September 2018 are shown. Red triangles represent dropsonde locations. Orange solid dots and dashed lines respectively represent observed and simulated tangential wind speed U tan (in ms⁻¹), anti‐clockwise positive. Blue solid dots and dashed lines respec...
Cantilevered roof is particularly vulnerable to wind because high suction loads often occur on the rooftop due to flow separation. However, wind load characteristics associated with cantilevered roof have not been fully understood. In this paper, a 1/100 scale model of a cantilevered roof, over a grandstand, has been tested in a turbulent boundary...
A dust devil was first observed in Hong Kong at the airport in 2021. This paper documents the meteorological conditions under which the dust devil occurred. The dust devil shows up nicely in the plan position indicator scans of a Doppler Light Detection And Ranging (LIDAR) system. The dust devil was found to be associated with a tiny vortex at the...
Understanding the vertical turbulent mixing processes in the planetary boundary layer (PBL) of tropical cyclones (TCs, or typhoons, hurricanes) and improving the PBL parameterization in numerical models of TCs is of paramount importance for TC modeling and forecasting. Based on the multi-level, high-resolution observations from Asia's tallest meteo...
Wind gust characteristics at wind turbine relevant height are closely tied with wind turbine design and wind power generation, which, however, have not been detailed and documented. In this study, high-resolution wind data recorded by 3D sonic anemometers at a tall meteorological tower were analyzed to determine 12 descriptors of wind gusts, and to...
The vast majority of current structural design codes and standards do not separately consider the wind and turbulence profiles for different storm types. Based on the 356-m-high Shenzhen Meteorological Gradient Tower, which is the tallest of its kind in Asia, this paper investigates the characteristics and vertical profiles of mean wind and turbule...
Based on the field measurements on a 600-m-tall skyscraper equiped with an active tuned mass damper (ATMD) system, this paper investigates the control performance of the world's largest ATMD system to suppress the building vibrations. On-site forced vibration tests on the skyscraper were first conducted and the results showed that the ATMD system c...