Richard Flay

Richard Flay
University of Auckland · Department of Mechanical Engineering

About

168
Publications
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2,181
Citations

Publications

Publications (168)
Article
The non-Gaussian property of turbulence has been emphasized in some measured wind data. However, the classic Scanlan buffeting theory with the Gaussian distribution assumption of turbulence may cause errors in predicting the structural extreme response. In this study, a hybrid approach for predicting bridge's extreme buffeting response is proposed...
Article
Many parallel bridges have been recently designed and built around the world to accommodate the ever-increasing volumes of vehicle and rail traffic. Accordingly, the aerodynamic interference around the parallel girders becomes important to investigate for a more accurate estimation of wind-induced effects on bridges. In this study, a wide range of...
Article
Full-text available
In this study, the resilience of large cities and their built infrastructure in New Zealand to extreme winds, is investigated by coupling the outputs of a very high-resolution, 333-m resolution, numerical weather prediction (NWP) model with computational fluid dynamics (CFD) simulations. Following an extreme wind event on 18 September 2020 in Auckl...
Article
There are a number of long-span bridges located in the southeast coastal bay of China which is prone to typhoons. Very limited studies have been made of the wind field characteristics in this bay which is special as it has various changes in fetch from sea to land and vice versa, depending on the wind direction. Thus, a detailed analysis of the win...
Article
Full-text available
Dome structures have been used extensively for industrial, residential, and military infrastructure. Therefore, it is necessary to understand the damage risk potential for such structures for blast-resistant design considerations. This paper investigates the effect of blast load variability on the design value and the structural dynamic response. T...
Article
The study aims to estimate design wind speeds and associated directional multipliers, also lee-zone multipliers for New Zealand through the analysis of historical wind data recorded at meteorological stations and also utilising a high-resolution convection-resolving numerical weather prediction model (New Zealand Convective-Scale Model (NZCSM)) ana...
Article
The increasing threat of terrorist attacks and the risk of accidental explosions has raised the alarm on structural design, and consequently, the dome structure as the classical building configuration model for public buildings requires safe and reliable defence capabilities against blast loads for the duration of its lifespan. Some deterministic b...
Article
In the present study, a combined cooling, heating and power (CCHP) system with a gas internal combustion (IC) engine prime mover, called EF7, has been proposed. A numerical model has been presented to evaluate the performance of the system, and for the first time, the effects of operating parameters of the IC engine, such as the combustion start an...
Article
The use of wind speed data recorded using different measuring equipment (i.e. anemometers with different response characteristics) and different signal-processing procedures can introduce errors in the characterisation of surface wind speeds. This study aims to assess the effects of a set of various moving average filter durations and turbulence in...
Conference Paper
Full-text available
A scaling or nondimensionalisation of atmospheric buoyancy vortices for power generation (based on the Oberbeck-Boussinesq assumption) is proposed that uses a published formulation from the study of Rotating Rayleigh-Benard Convection. This is combined with assumptions that the vortex flows are pseudo-cyclostrophic and that a radial Richardson numb...
Article
Full-text available
The ERA5 reanalysis product has been compared with hourly near-surface wind speed and gust observations across Sweden for 2013–2017. ERA5 shows closer agreement than the previous ERA-Interim reanalysis with regard to both mean wind speed and gust measurements, although significant discrepancies are still found for inland and mountainous regions. Th...
Article
It is essential in a bridge design to study the wind parameters at the bridge site, particularly in a complex mountain area where the wind characteristics vary from location to location. The aim of this paper is to study the wind characteristics in a Y-shaped valley in mountainous terrain, the site of a proposed long-span bridge. Data recorded cont...
Article
Dome structures are often employed for industrial buildings and may be potential targets of terrorist attacks or accidental explosion. Military design manuals that are commonly used for structural design practice are based on the assumption that the blast wave reflects on an infinite or finite flat surface. These semi-empirical formulae ignore the...
Article
Full-text available
The study investigates one of the major causes of damage in severe wind events in urban areas: windborne debris, using a case study of a location in the Auckland city centre, New Zealand. The probability and risk of paving stone ballast becoming windborne from the podium of a tall building was evaluated through wind-tunnel experiments and numerical...
Research
Full-text available
Extreme wind hazards have a substantial societal and environmental impact on countries. Due to the complex origins of extreme winds, there are great knowledge gaps about their variations and the associated mechanisms, which makes their prediction very challenging. New Zealand’s vulnerability to extreme weather is well known, due to its position in...
Article
The dynamic performance of single-layer reticulated domes under explosions was analysed experimentally and numerically in this study. The loading was generated by a Gas Blast Shock loading system (GBS) by igniting a gaseous mixture and applying it to the reduced-scale structure to investigate the dynamic response modes. Acetylene/air mixtures with...
Article
The aim of the research described in this paper is to reduce the vulnerability of New Zealand's built infrastructure to wind damage through provision of improved wind speed prediction procedures for wind flow over complex terrain that could ultimately be incorporated into the AS/NZS 1170.2 loading standard. This paper presents results from a specif...
Article
Full-text available
This study aims at (i) analysing the gust wind records of four meteorological stations across New Zealand for 1972-2017; (ii) investigating whether or not the long-term wind gust series have changed significantly; and (iii) assessing the impact of these changes in the estimation of design wind speeds to ensure the safety and reliability of future s...
Research
Full-text available
Published in New Zealand Natural Hazards Magazine: https://www.naturalhazards.org.nz/NHRP/Publications/Natural-Hazards-Issues
Conference Paper
Full-text available
The wind speeds recorded since 1997 at a height of 318 m from anemometers mounted on the Sky Tower in Auckland, New Zealand, are the focus of this study. Mean and gust speeds have been measured by two anemometers, one mounted out from the North-West side and the other out from the South-East side. The tower and the surrounding buildings affect the...
Poster
Full-text available
We evaluated and compared the performance of two numerical approaches, namely Reynolds-averaged Navier-Stokes (RANS) and hybrid RANS/Large Eddy Simulation (LES), in simulating wind flow over isolated and consecutive hills. Wind-flow characteristics over isolated and consecutive sinusoidal hills were investigated and also effects of hill slope on th...
Article
Full-text available
A broad range of research in a programme undertaken over the past 4 years, and in earlier closely related research programmes, has led to the development of recommendations for the New Zealand component of the joint Australia/New Zealand Wind Loadings Standard AS/NZS 1170.2. These recommendations mainly concern the analysis of the design wind speed...
Article
In most wind load codes, the wind direction is assumed to be the same along the height in the atmospheric boundary layer (ABL). But actually, due to the Earth's rotation (Coriolis force), the wind direction in the ABL changes along the height. This twisted wind flow (TWF) will obviously make a difference to the wind loads on megatall buildings. In...
Article
The paper presents a Velocity Prediction Program for hydrofoiling catamarans with solid wing sails. Starting from a description of the mechanical model, suitable models are identified for the forces that act on the boat components. The study is deliberately limited to means for restricted methods where computational resources and budgets are limite...
Article
This paper describes how a combination of high-resolution numerical modeling, a robust homogenization algorithm, and local pressure observations have been used to understand and reconcile time series of daily, seasonal, and annual peak wind gusts recorded at observing sites in the Cook Strait region of New Zealand. The homogenization algorithm con...
Article
The accurate simulation of wind flow in the boundary layer wind tunnel is very important for the relevant research on the environmental and structural wind engineering. Due to the earth's rotation, an Ekman spiral shaped wind direction profile would be generated, which is a common phenomenon in the thousand-meter high atmospheric boundary layer (AB...
Conference Paper
Pressure-driven horizontally homogeneous atmospheric boundary layer flow has been numerically modelled using Reynolds Averaged Navier–Stokes (RANS) equations with a Shear Stress Transport (SST) turbulence closure. The flow over full scale two-dimensional isolated and consecutive sinusoidal hills has been studied. Different hill slopes and shapes ha...
Article
Full-text available
We evaluate the accuracy of the speed-up provided in several wind-loading standards by comparison with wind-tunnel measurements and numerical predictions, which are carried out at a nominal scale of 1:500 and full-scale, respectively. Airflow over two- and three-dimensional bell-shaped hills is numerically modelled using the Reynolds-averaged Navie...
Poster
Full-text available
Using surface-layer wind speeds directly without correction for terrain and instrument response characteristics can introduce significant errors in climatological studies, particularly when dealing with long-term historical data. Usually, wind speeds collected at airports are of great importance to climatology studies due to good quality and length...
Conference Paper
Full-text available
Using surface wind speed observations directly without correction for terrain and instrument response characteristics can introduce significant errors in extreme wind speed estimates and other climatological studies. Wind speed measurements collected during 1972 to 2016 at Wellington airport, New Zealand, are the focus of this study. There is a con...
Conference Paper
Full-text available
Several types of cup anemometers with considerably different designs and recording systems have been used in New Zealand during various periods. The changes in instrumentation and observing practices have affected the recorded wind speeds and resulted in inhomogeneous historical data. In this study, wind-tunnel tests were carried out to compare the...
Article
Wind tunnel tests of synchronous measurements of the buffeting lifts and moments on six separated strips of a motionless 1:45 scale sectional model of a flat closed-box bridge deck were carried out in three turbulent flow conditions. The longitudinal and vertical components of turbulent wind speed were also measured synchronously with the buffeting...
Conference Paper
Full-text available
Extreme winds can be dangerous for people and cause significant damage to property and buildings. Analysing the historical wind data to gain a better understanding of the space and time distribution of extreme winds is essential to produce appropriate design wind speeds. However, the historical wind data set have not been analysed in New Zealand fo...
Conference Paper
Full-text available
Dust-devil wind-speeds are modelled for a dataset from NASA Report DAC-63098. The model suggests dust-devils act as heat-engines which convert Convectively Available Potential Energy (CAPE) available within the super-adiabatic boundary layer into rotational kinetic energy at an efficiency proportional to the height of the super-adiabatic layer. The...
Article
Full-text available
We compare ethnological views of Māori canoes (waka) of the first colonisation period with those of the European contact period, and then describe diverse archaeological waka from the interim period. The aim is to reconstruct basic design elements of whole canoes and to suggest their relative ages. Variations in form relate to differences in sailin...
Article
The structure of turbulence in a rapid tidal flow is characterized through new observations of fundamental statistical properties at a site in the UK which has a simple geometry and sedate surface wave action. The mean flow at the Sound of Islay exceeded 2.5 m s(-1) and the turbulent boundary layer occupied the majority of the water column, with an...
Conference Paper
Mean and gust wind speeds can be increased significantly by natural and man-made topography. Various multipliers provided in wind loading standards and codes can be used to predict these speed-ups, and accordingly, structures are designed to resist the effects of topographic wind speed-ups. The need to confirm the actual mean and gust wind speed-up...
Article
Synchronical measurements of fluctuating lifts and moments on six bridge deck strips in a motionless 1:45 scale model were carried out in the TJ-2 Wind Tunnel at Tongji University by using six miniature force-balances. Furthermore, synchronical measurements of pressures on six same-arranged strips in another identical model were also conducted for...
Article
This paper investigates an inverse process for the design of yacht sails. The method is described and then applied to the design of optimal sails for a specific yacht. The proposed inverse method generates the three-dimensional shapes of a headsail and mainsail from prescribed loading (i.e. differential pressure) distributions, accounts for the eff...
Article
Wind tunnel tests of a 1/2200-scale mountainous terrain model have been carried out to investigate local wind characteristics at a bridge location in southeast Tibet, China. Flows at five key locations on the bridge at deck level were measured for 26 directions. It was observed that wind characteristics (including mean wind velocity and overall tur...
Article
A detailed wind tunnel test has been carried out on a motionless flat-box bridge deck model with three special grid-generated wind fields using an electronically scanned pressure transducer system, enabling almost instantaneous capture of 372 pressure tap signals from 6 sections of 62 different spacing taps at each section. A very complete analysis...
Conference Paper
Full-text available
A modification of the published heat engine theory of Renno et al. is suggested to allow an improved prediction of vortex height and consequent thermodynamic efficiency and wind-speeds in dust devils, through a reconsideration of the nature of the cold reservoir of the heat engine.
Article
Full-text available
This paper investigates an inverse process for the design of yacht sails. The method is described and then applied to the design of optimal sails for a specific yacht. The proposed inverse method generates the three-dimensional shapes of a headsail and mainsail from prescribed loading (i.e. differential pressure) distributions, accounts for the eff...
Article
Full-text available
An improved characterisation of the hydrodynamic blade loads due to onset turbulence is essential in order to mitigate premature failures, reduce excessive levels of conservativeness and ultimately ensure the commercial viability of tidal turbines. The literature focussing on the turbulence in fast flowing tidal streams and of the unsteady loads th...
Conference Paper
Full-text available
An experiment was performed in the Yacht Research Unit’s Twisted Flow Wind Tunnel (University of Auckland) to test the effect of dynamic trimming on three IMOCA 60 inspired mainsail models in an upwind (AWA = 60deg) unheeled configuration.This study presents dynamic fluid structure interaction results in well controlled conditions (wind, sheetlengt...
Article
Following the 33rd America's Cup which featured a trimaran versus a catamaran, and the recent 34th America's Cup in 2013 featuring AC72 catamarans with multi-element wing sail yachts sailing at unprecedented speeds, interest in wing sail technology has increased substantially. Unfortunately there is currently very little open peer-reviewe...
Article
We report on a collaboration between archaeology and the Yacht Research Unit at the University of Auckland to investigate the sailing characteristics of Pacific canoes, both ancient and modern. Archaeology provides a chronology for the colonisation of Pacific Islands, but one mystery that remains is how well the canoes could sail. We describe the f...
Article
Full-text available
Download link: http://authors.elsevier.com/a/1QHvz3QJ-dH6di An improved characterisation of the unsteady hydrodynamic loads on tidal turbine blades is necessary to enable more reliable predictions of their fatigue life and to avoid premature failures. To this end, this paper presents a set of blade-root bending moment responses for a scale-model ti...
Conference Paper
Full-text available
This paper presents new results obtained from analysing on-the-water pressure, shape, force, speed and direction data that were obtained from experiments in the Hauraki Gulf in Auckland, New Zealand in April 2014. A fully instrumented Stewart 34 Class yacht sailing downwind was used for the tests. Details of the analysis of the results from simulta...
Conference Paper
The general flow features observed on yacht sails can be predicted with well-established fluid dynamic theory. Headsails are thin wings with a sharp leading edge and thin-airfoil theory can predict the general flow and pressure fields around these sails. However, a closer look shows viscous flow features, such as the leading edge bubble, that canno...
Conference Paper
The general flow features observed on yacht sails can be predicted with well-established fluid dynamic theory. Headsails are thin wings with a sharp leading edge and thin-airfoil theory can predict the general flow and pressure fields around these sails. However, a closer look shows viscous flow features, such as the leading edge bubble, that canno...
Conference Paper
The means by which the ancestors of Maori and Polynesian peoples were able to explore and settle the Pacific Ocean are hotly contested. Hypothesis 1 holds that prehistoric canoes had considerable sailing capabilities and that the seafarers were competent navigators able to steer their canoes by the stars and other sea signs, to explore the ocean an...
Article
We propose two methods for short term forecasting of wind direction with the aim to provide input for tactic decisions during yacht races. The wind direction measured in the past minutes is used as input and the wind direction for the next two minutes constitutes the output. The two methods are based on artificial neural networks (ANN) and support...
Conference Paper
Full-text available
This paper summarises and compares methods recommended in seven different national and international wind loadings standards for determining wind speed hill shape multipliers. In an attempt to help determine the accuracy of the predictions from the standards, a comparison has been made of the seven predictions from the standards and full-scale spee...
Article
An innovative method combining simultaneous on-water pressure and sail shape measurements for determining aerodynamic forces produced by sails is described and used on Stewart 34 and J80 Class yachts flying asymmetric spinnakers. Data were recorded in light and medium winds in order to check the reliability, accuracy and repeatability of the system...
Book
Full-text available
It is with much pleasure that we write the editorial for this special issue devoted to Yacht Engineering, arising from the 3rd International Conference on Innovation in High Performance Sailing Yachts (Innov'sail 2013), held in Lorient, France. The conference took place during 26–28 June 2013 and was chaired by Dr Patrick Bot from the Naval Academy...
Article
When the future wind direction is uncertain, the tactical decisions of a yacht skipper involve a stochastic routing problem. The objective of this problem is to maximise the probability of reaching the next mark ahead of all the other competitors. This paper describes some numerical experiments that explore the effect of the skipper׳s risk attitude...
Article
The cavitation aspect of the transient interaction of a vessel hull with extreme breaking waves is considered. The authors show that the elastic deformation of thin hull elements by a short water-wave pressure pulse can be accompanied by hull cavitation. The effect of this cavitation is important if the duration of loading by the water pressure is...
Article
Full-text available
This paper presents the results of experimental tests conducted to study the aerodynamic performance of sailing dhows. The investigation emerged from the interest shown by designers and sail-makers to understand how these sails perform, since they have never been studied before. The 43ft/13.lm and 60ft/18m classes have been tested in a wind tunnel...
Conference Paper
Full-text available
Overview On December 8 2012 a building impact survey was conducted in Hobsonville and Whenuapai, Auckland following a damaging tornado 1 event. The survey purpose was to collect wind hazard exposure, building attribute and building damage information to validate wind damage functions used in the 'RiskScape' tool. The updated functions were then app...
Conference Paper
Full-text available
NIWA and GNS are Crown Research Institutes in New Zealand with interests in Natural Hazards research. Recently they have partnered to develop the RiskScape multi-hazard impact and risk assessment tool for application in New Zealand and potentially the Pacific Islands. However, for only a few previous damaging wind storm previous events has field da...
Article
In this paper, the aerodynamic performance of the telescopic blade wind turbine concept has been analysed experimentally and computationally. A model-scale wind turbine with two-stage telescopic blades, having a chord ratio of 0.6, was studied in the wind tunnel for different blade extensions (i.e. different lengths of the second section, ranging 0...
Chapter
This chapter describes a relatively well developed method for determining the along-wind response of tall buildings to wind excitation using a theoretical approach. It has been found to give good predictions, and is now the basis of along-wind response predictions in some wind loading standards and codes. It is based on the premise that the along-w...
Chapter
The aerodynamic characteristics of bluff bodies differ substantially from streamlined bodies, and an understanding of bluff body aerodynamics is essential to make progress in understanding wind engineering. Streamlined bodies like aircraft wings have a rounded nose, a thin profile, and a sharp trailing edge. Their wakes are small and for small angl...
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