• Home
  • UNSW Sydney
  • School of Engineering and Information Technology
  • Joseph C. S. Lai
Joseph C. S. Lai

Joseph C. S. Lai
UNSW Sydney | UNSW · School of Engineering and Information Technology

PhD

About

284
Publications
90,762
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
6,438
Citations
Additional affiliations
January 2003 - January 2017
UNSW Sydney
Position
  • Professor in Mechanical Engineering

Publications

Publications (284)
Conference Paper
Full-text available
The immersed boundary method (IBM) has attracted growing interest in the computational fluid dynamics (CFD) research community due to its simplicity in dealing with moving boundaries in fluid-structure interaction (FSI) systems. We present a study on streamline penetration, velocity error and consequences of an FSI solver based on an iterative feed...
Article
Full-text available
This paper presents a study on streamline penetration, velocity error and consequences of a fluid-structure interaction (FSI) solver based on the feedback immersed boundary method (IBM). In the FSI solver, the fluid dynamics is solved by the lattice Boltzmann method; the solid structure deformation is solved by the finite difference method and the...
Article
Full-text available
Termites sense tiny substrate-borne vibrations through subgenual organs (SGOs) located within their legs’ tibiae. Little is known about the SGOs’ structure and physical properties. We applied high-resolution (voxel size 0.45 μm) micro-computed tomography (μCT) to Australian termites, Coptotermes lacteus and Nasutitermes exitiosus (Hill) to test two...
Conference Paper
Micro-vibration signals in bioassays under controlled environmental conditions in biotremology require a device that can generate a similar level of vibration response as caused by the insect. Since bioassays often need to be run in environmental cabinets, the space available is limited, and structures to be excited should not be mass loaded. Consi...
Conference Paper
Micro-vibrations caused by the motion of insects, provide a content-rich signal that may be perceived by nestmates, competitors or predators. Knowing the ground reaction forces of a single leg im-pacting the surface can provide quantitative information about the interaction with the substrate, the substrate itself, physiological and behavioural sta...
Article
The influences of serrated trailing edge on the aerodynamic and aeroacoustic performance of a flapping wing during hovering flight are investigated using a hybrid framework of an immersed boundary Navier–Stokes solver for the flow field and the Ffowcs Williams–Hawkings (FW–H) analogy for the sound field. A rigid rectangular wing with an aspect rati...
Conference Paper
Full-text available
Fluid-structure interactions (FSIs) of fluid-conveying collapsible vessels produce rich physiologically significant phenomena in many biological systems. However, it remains challenging to compute the flow-induced vibration of collapsible vessels due to nonlinear FSIs involving large-deformations, three-dimensional (3-D) motion, unsteady flows and...
Conference Paper
Full-text available
Wing pitching motion in insect flapping flight has been recognized as a passive phenomenon induced by inertial and aerodynamic forces. Inspired by the insect flight, passively pitching flapping wings have been implemented in micro aerial vehicles (MAVs) designs. The pitching angle of the flapping wings is passively modulated by an elastic hinge usi...
Article
Full-text available
The nonlinear dynamics of a two-sided collapsible channel flow is investigated by using an immersed boundary-lattice Boltzmann method. The stability of the hydrodynamic flow and collapsible channel walls is examined over a wide range of Reynolds numbers $Re$ , structure-to-fluid mass ratios $M$ and external pressures $P_e$ . Based on extensive simu...
Article
Termites inhabit complex underground mounds of intricate stigmergic labyrinthine designs with multiple functions as nursery, food storage and refuge, while maintaining a homeostatic microclimate. Past research studied termite building activities rather than the actual material structure. Yet, prior to understanding how multi-functionality shaped te...
Article
A novel model is proposed to estimate the optimal propulsive efficiency and the optimal dimensionless heaving velocity of a flapping foil based on a lift–drag ratio under the assumption of negligible pitching power. The optimal efficiency increases with the lift–drag ratio. The optimal Strouhal number of sinusoidal heaving motion approaches 0.318,...
Article
Full-text available
The dynamic behaviours of a filament in a viscoelastic uniform flow were investigated by an immersed boundary-lattice Boltzmann method. The effects of the Reynolds numbers (Re, ranging from 10 to 200) and the Weissenberg number (Wi, ranging from 0 to 1.2) on the filament flapping motion and the drag and lift coefficients on the filament were studie...
Article
Full-text available
Fish adaption behaviors in complex environments are of great importance in improving the performance of underwater vehicles. This work presents a numerical study of the adaption behaviors of self-propelled fish in complex environments by developing a numerical framework of deep learning and immersed boundary–lattice Boltzmann method (IB–LBM). In th...
Chapter
Despite significant efforts made in the last two decades for the analysis and prediction of brake squeal propensity, brake squeal remains a major source of customer dissatisfaction and warranty-related costs. Brake squeal is a fugitive nonlinear self-excitation phenomenon induced by friction. Traditional linear complex eigenvalue analysis (CEA) com...
Conference Paper
Full-text available
The immersed boundary method has attracted growing interest in the CFD research community due to its simplicity in dealing with moving boundaries. In the diffused interface immersed boundary method, a discrete delta function is introduced to account for the boundary effects on the fluid, which causes the diffusion of the boundary interface. Therefo...
Conference Paper
Full-text available
The fluid flow through a 50% diameter reduction asymmetric stenosis is simulated by the diffused interface immersed boundary-lattice Boltzmann method. In the diffused interface immersed boundary method (IBM), a discrete delta function is introduced to account for the boundary effects on the fluid, which causes the diffusion of the boundary interfac...
Article
A control volume based analytical method for calculating the efficiency η of flapping foil power generators was developed for single and tandem foil configurations. Ignoring unsteady effects and non-uniform pressures resulted in theoretical limits identical to the Betz (η = 16/27 for a single turbine) and Newman (η = 16/25 for tandem turbines) limi...
Article
Full-text available
Termite mounds are fascinating because of their intriguing composition of numerous geometric shapes and materials. However, little is known about these structures, or of their functionalities. Most research has been on the basic composition of mounds compared with surrounding soils. There has been some targeted research on the thermoregulation and...
Article
The flow-induced vibration characteristics and energy extraction performance of flexible inverted piezoelectric flags in a uniform flow are studied by using an immersed boundary-lattice Boltzmann method for Reynolds number of 100, mass ratio of 2.9 and non-dimensional bending stiffness of 0.26 which correspond to the maximum flapping amplitude for...
Article
This paper presents an immersed boundary (IB) method for fluid–structure–acoustics interactions involving large deformations and complex geometries. In this method, the fluid dynamics is solved by a finite difference method where the temporal, viscous and convective terms are respectively discretized by the third-order Runge–Kutta scheme, the fourt...
Article
An immersed boundary-lattice Boltzmann method (IB-LBM) for fluid-structure interaction (FSI) problems involving viscoelastic fluids and complex geometries is presented in this paper. In this method, the fluid dynamics and the constitutive equations of viscoelastic fluids are both solved using the lattice Boltzmann method. In order to enhance numeri...
Chapter
Socially living insects rely on efficient and accurate communication and source localisation for survival. Insects communicate multimodally using visual, chemical or mechanical cues. Vibrations are often considered to be a primitive mode of exchanging information, but vibrations are independent of sight or airflow, and can reach the destination cry...
Book
Full-text available
This volume is a self-contained companion piece to Studying Vibrational Communication, published in 2014 within the same series. The field has expanded considerably since then, and has even acquired a name of its own: biotremology. In this context, the book reports on new concepts in this fascinating discipline, and features chapters on state-of-t...
Conference Paper
Full-text available
Fluid-structure interaction (FSI) in collapsible channel flow is numerically studied with an immersed boundary-lattice Boltzmann method. Compared with previous studies, current method is able to simulate nonlinear fully coupled FSI in two-sided collapsible channel and high Reynolds numbers flow (Re up to 2000). The stability of the hydrodynamic flo...
Article
Animals use cues to find their food, in microhabitats within their physiological tolerances. Termites build and modify their microhabitat, to transform hostile environments into benign ones, which raises questions about the relative importance of cues. Termites are desiccation intolerant and foraging termites are attracted to water, so most researc...
Preprint
This paper presents an immersed boundary (IB) method for fluid--structure--acoustics interactions involving large deformations and complex geometries. In this method, the fluid dynamics is solved by a finite difference method where the temporal, viscous and convective terms are respectively discretized by the third-order Runge-Kutta scheme, the fou...
Article
The dynamic characteristics of a two-dimensional deformable capsule in a simple shear flow are studied with an immersed boundary-lattice Boltzmann method. Simulations are conducted by varying the Reynolds number (Re) from 0.0125 to 2000 and the dimensionless shear rate (G) from 0.001 to 0.5. The G-Re plane can be divided into four regions according...
Book
Full-text available
Complete coverage of all aspects of electromagnetic, structural, and vibroacoustic noise in induction and permanent magnet brushless machines
Article
As eusocial and wood-dwelling insects, termites have been shown to use vibrations to assess their food, to eavesdrop on competitors and predators and to warn nest-mates. Bioassay choice experiments used to determine food preferences in animals often consider single factors only but foraging decisions can be influenced by multiple factors such as th...
Conference Paper
The interaction of two tandem inverted piezoelectric flags in uniform flow is investigated. An immersed boundary method based on the multi-block lattice Boltzmann method (LBM) is used to study the dynamics of the fluid-structure interaction of the tandem flags as well as their energy harvesting performance. At a Reynolds number of 100, mass ratio 2...
Data
Supplementary Information for paper "Key physical wood properties in termite foraging decisions" Sebastian Oberst , Joseph C. S. Lai and Theodore A. Evans https://royalsocietypublishing.org/doi/10.1098/rsif.2018.0505
Article
Even though much research has been devoted to understand friction-induced vibrations, its root cause is not yet fully understood. Reliable prediction of friction-induced unstable vibrations such as in brake squeal or hip squeak remains a challenge because of nonlinearities involved and because the complex eigenvalue analysis (CEA) widely used in in...
Article
The aerodynamic characteristics of model hoverflies during hovering flight are studied with a three-dimensional sharp-interface immersed boundary method. The wing is modelled as a rectangular generic wing to test the effects of an accessory flap called the alula, which is located at the wing root. Simulations are conducted in two groups: One group...
Article
Aerodynamic characteristics of hoverflies during hovering flight are studied with a three-dimensional sharp-interface immersed boundary method. The wing of hoverfly is modelled with a rectangular generic wing. Simulations are conducted in two groups: One group of simulations are conducted to determine the equilibrium kinematics of the wings with an...
Presentation
Full-text available
Insects can perceive multimodal cues including smell, vision, tactile and vibrational information or acoustics. Some of these signals are used to communicate, some of them are just used to extract information but all of them and influence mating or foraging decisions. One common signal abundant in nature is that of substrate responses due to moving...
Presentation
It has been shown in recent years that vibration and acoustics play an important role in insect communication and cue detection. It is well known that ants use acoustic signals detected by sensory organs within their legs. Termites communicate mainly using vibrations and our recent research shows they are able to detect their predators solely on vi...
Article
The effect of hawkmoth-like flexibility on the aerodynamic hovering performance of wings at a Reynolds number of 400 has been assessed by conducting fluid structure interaction simulations incorporating a finite difference based immersed boundary method coupled with a finite-element based structure solver. The stiffness distribution of a hawkmoth f...
Article
For hydrodynamic optimization using computational fluid dynamics methods, the high computational cost impedes the use of evolutionary algorithms since they require evaluation of numerous solutions. In this paper, a multi-fidelity evolutionary algorithm, implemented with a dynamic stall model and a modified discrete vortex method, is used to find va...
Article
A novel computational framework which combines the lattice Boltzmann method (LBM) and an improved immersed boundary method (IBM) based on a dynamic geometry-adaptive Cartesian grid system is introduced for the fluid–structure interaction (FSI) problems at moderate and high Reynolds numbers. In this framework, the fluid dynamics is obtained by solvi...
Conference Paper
Full-text available
Brake squeal, as a phenomenon of friction-induced self-excited vibrations, has been a noise, vibration and harshness (NVH) problem for the automotive industry due to warranty-related claims and customer dissatisfaction. Intensive research in the past two decades have provided insight into a number of mechanisms that trigger brake squeal. However, b...
Poster
Full-text available
Extracting features from experimental time series (TS), especially for nonlinear systems, using nonlinear time series analysis (NTSA) has largely been neglected in the past. Brunton et al. have shown that it is possible to extract a set of differential equations (DE) describing a steady-state using a phase space reconstruction of a scalar time seri...
Article
Owing to an ageing population, the impact of unhealthy lifestyle, or simply congenital or gender specific issues (dysplasia), degenerative bone and joint disease (osteoarthritis) at the hip pose an increasing problem in many countries. Osteoarthritis is painful and causes mobility restrictions; amelioration is often only achieved by replacing the c...
Article
Full-text available
Owing to an ageing population, the impact of unhealthy lifestyle, or simply congenital or gender specific issues (dysplasia), degenerative bone and joint disease (osteoarthritis) at the hip pose an increasing problem in many countries. Osteoarthritis is painful and causes mobility restrictions; amelioration is often only achieved by replacing the c...
Article
This paper presents a numerical study of a 2D pitching and plunging flat plate foil operating in the vicinity of near side walls. The efects of the side wall proximity and the stroke reversal fraction are compared to previously published water tunnel experimental results and the resulting vortex structures are used to comment on the efect of the co...
Article
The flexibility effects on the performance of a flapping foil power generator are numerically studied by using the immersed boundary-lattice Boltzmann method at a Reynolds number of 1100. The flapping foil system consists of a rigid NACA0015 foil undergoing harmonic pitch and plunge motions and a passively actuated flat plate pinned to the trailing...
Presentation
Full-text available
Termites are notorious for their destructive nature and cryptic character. Termites (order Isoptera) communicate multi-modally, however, their dominant mode of communication is that of using substrate-borne vibrations. The use of vibrations distinguishes termites from their main predators, the ants (order Hymenoptera), which inhabit similar ecologi...
Conference Paper
Owing to an ageing population, the impact of unhealthy lifestyle, or simply congenital or gender specific issues (dysplasia), degenerative bone and joint disease (osteoarthritis) at the hip pose an increasing problem in many countries. Osteoarthritis is painful and causes mobility restrictions; amelioration is often only achieved by replacing the c...
Conference Paper
Full-text available
Since brake squeal was first investigated in the 1930s, it has been a noise, vibration and harshness (NVH) problem plaguing the automotive industry due to warranty-related claims and customer dissatisfaction. Accelerating research efforts in the last decade, represented by almost 70% of the papers published in the open literature, have improved the...
Conference Paper
Full-text available
Termites are notoriously cryptic: infestations in houses are often discovered when an apparently intact timber object collapses, the archetypal 'falling through the floor boards'. This behaviour is adaptive because remaining undiscovered is the termite's primary defence against predators. However, being cryptic severely limits the ability of termit...
Article
Full-text available
This study is focused on evaluating the aerodynamic performance of rigid and isotropic flexible wing shapes defined by the radius of the first moment of wing area at Reynolds number of 6000. An immersed boundary method was used to solve the 3D, viscous, incompressible Navier-Stokes equations, and coupled with an in-house non-linear finite element s...
Article
This study provides a comprehensive analysis of the effects of flexibility on bumblebee propulsion. The unusual stiffness distribution of bumblebee wings caused by the absence of veins on their outer one-third region is analyzed for the first time, with two flexible-wing models and one rigid-wing model tested in two-way Fluid-Structure Interactions...
Article
Eavesdropping has evolved in many predator–prey relationships. Communication signals of social species may be particularly vulnerable to eavesdropping, such as pheromones produced by ants, which are predators of termites. Termites communicate mostly by way of substrate-borne vibrations, which suggest they may be able to eavesdrop, using two possibl...
Data
Eavesdropping has evolved in many predator–prey relationships. Communication signals of social species may be particularly vulnerable to eavesdropping, such as pheromones produced by ants, which are predators of termites. Termites communicate mostly by way of substrate-borne vibrations, which suggest they may be able to eavesdrop, using two possibl...
Conference Paper
Wing geometric parameters govern the aerodynamic performance of insects and micro aerial vehicles. Previous studies of wing shapes have been limited to rigid wings. The aerodynamic hovering performance of rigid and flexible wing shapes for aspect ratio AR = 1.5 is evaluated computationally at the Reynolds number (Re) of 400. The three-dimensional v...
Article
This numerical study is focused on assessing the effect on the aerodynamic hovering performance of wing shapes defined by the radius of the first moment of the wing area ( r 1 ¯) and aspect ratio (AR). In addition, the effect of introducing a deviation angle in the kinematics is examined. The performance of r 1 ¯ = 0 . 43, 0.53, and 0.63 wings with...
Article
Energy harvesting using flapping foils has attracted significant attention in the last 10 years. In contrast to conventional turbines, which rely on attached flow for high efficiency, a flapping-foil turbine exploits the separation of fluid flow near the nose of the foil to form a leading-edge vortex, resulting in high instantaneous forces. To redu...
Conference Paper
Full-text available
Brake squeal, as friction-induced audible noise above 1 kHz to 20 kHz, is a major concern to automotive manufacturers because of noise, vibration and harshness performance and warranty-claim related costs. The prediction of brake squeal is as difficult as ever due to nonlinearities, uncertainty boundary and operating conditions. The exact contact c...
Conference Paper
Full-text available
Osteoarthritis in hip joints affects patients’ quality of life such that often only costly orthopaedic surgeries i.e. total hip arthroplasty (THA) provide relief. Common implant materials are metal alloys, steel or titanium-based, plastics such as ultra-high molecular weight polyethylene, or biocompatible alumina and composite ceramics. Hard-on-har...
Conference Paper
Full-text available
Brake squeal, defined as audible noise above 1 kHz, is triggered by energy provided in the contact area between the pad and the disc and friction-induced instabilities. Owing to customers’ demand of reducing vehicle noise and the increasing use of light composite materials in cars, squealing brakes remain a major concern to the automotive industry...
Presentation
Full-text available
Eusocial insects communicate multimodally using visual, chemical or mechanical (touch, vibration, pressure differences) cues. Termites make use of substrate-borne vibrations, to detect conspecifics or to locate competitors; the secretive gnawing wood is very different to the soldiers’ obvious alarm signal, a repetitive head drumming on the ground....
Article
Full-text available
Despite significant progress made in the past 20 years in discovering some of the mechanisms of brake squeal, it remains difficult to predict the underlying friction-induced instabilities reliably. Most numerical analyses are based on linear deterministic analyses of structural vibrations such as the complex eigenvalue analysis (CEA). However, nonl...
Conference Paper
Full-text available
Brake squeal is a strong cost driver for automotive manufacturers owing to warranty-claim related costs. It is difficult to model numerically because of nonlinearities, and uncertainties in complex contact interactions, friction characteristics, operating and environmental conditions in a brake system. In addition, finite element brake models are o...
Article
Brake squeal is a source of significant warranty-related claims for automotive manufacturers because it is annoying and is often perceived by customers as a safety concern. A brake squeal analysis is complex due to changing environmental and operating conditions, high sensitivity to manufacturing and assembly tolerances as well as the not so well u...
Article
Brake squeal is a source of significant warranty-related claims for automotive manufacturers because it is annoying and is often perceived by customers as a safety concern. A brake squeal analysis is complex due to changing environmental and operating conditions, high sensitivity to manufacturing and assembly tolerances as well as the not so well u...