Turbulent Air Stream Research Articles

Toxic metals from atmospheric particulate matter in food species of tomato (Solanum lycopersicum) and strawberry (Fragaria x ananassa) used in urban gardening. A closed chamber study

In this work, two plant foods, strawberry and tomato, were subjected to exposure to metals from synthetic airborne particles in a closed chamber experiment. The synthetic particles were obtained in the laboratory. Within the closed chamber, particles were added and recirculated for 4 days in a turbulent air stream, causing deposition on the different parts of the plants. They were evaluated because of their increasingly frequent cultivation in urban gardens of cities. The main objectives were to determine whether the species accumulate metals significantly, which species accumulate the most, and in which parts of the plant. Finally, an attempt was made to differentiate the accumulation of pollutants by surface deposition on leaves and fruits from the adsorbed metals into the leaf or the fruit by their stomata or cuticles. The concentration of heavy metals was quantified in fruits, leaves and the soil after exposure. Metals were evaluated as a whole and individually, both in dry and fresh weight basis. The decrease of particulate matter and metals in the air inside the chamber was also studied in order to evaluate the use of both food species as air purifier by vertical gardens. The concentration of metals in plants (mg kg−1) and airborne particles (mg m−3) was measured by microwave plasma optical emission spectroscopy (MP-AES). For the sake comparison of total amount of metals in the samples concentrations were normalized. Strawberries was the food species that accumulated the largest amount of metals. In a dry weight basis, tomato leaves and strawberry fruits were the parts of the plants with higher accumulation capacity of particles and metals. The potential toxic elements Cd, Ni and Cr in tomato leaves and in strawberry fruits had a higher presence in the interior of the plant system. In a fresh weight basis, the strawberry fruit had the most accumulation capacity for metals.

Application of an aerosol deposition model to whole body dermal exposure scenarios involving VX

In this report we present the application of a modified aerosol deposition model to a number of scenarios involving a whole body dermal exposure to the toxic chemical nerve agent VX in the form of a liquid aerosol. An aerosol deposition model is modified to simulate the distribution of deposited aerosolized particles on the surface of a mannequin exposed to a turbulent air stream with a specified aerosol concentration and particle size distribution, using as few turbulence flow parameters as possible. The aerosol deposition model allows for the calculation of deposition velocity, total deposited mass, and other quantities, over the entire surface of a mannequin given the aerosol concentration, exposure time, particle size distribution, and air flow conditions are specified. The model uses shear velocity distributions over a mannequin, obtained from computational fluid dynamic (CFD) simulations, and accounts for three particle transport mechanisms: Brownian (molecular) diffusion, turbulence (eddy) diffusion, and gravitational sedimentation. Additionally, the model considers surface roughness and orientation of the mannequin surface relative to gravity. The model is integrated into a broader computer program, written in the Fortran programming language, that handles all input and output.

The effects of turbulent air streams and corrugated surfaces on the output of a wind turbine

It is challenging to select the area that best fit the installation of wind turbines within complex and forestry terrains. This study aims to highlight the effects of corrugated surfaces on the characteristics of a turbulent wind flow, and on the performance of a wind turbine installed within this topography. It is hypothesized that a sinusoidal wave can be utilized to describe a corrugated surface. The physical stance was analytically modeled based on conservation principles of mass and mechanical energy. Model’s mathematical equation was then solved, by adopting finite difference method and MATLAB’s Bvp4c algorithm. The results show that wind and turbine related parameters are affected by the evolved atmospheric Boundary Layer (ABL) and differed according to the location within the boundary layer (BL) from the leading part to the edge, where BL’s retarding effects diminishes. The study also proves that velocity and turbine harvested power are inversely proportional to the corrugated surface’s amplitude, and to the wind’s turbulence ratio. On the other hand, it demonstrates a direct proportion between boundary layer thickness (BLT) and corrugated surfaces-related parameters. To the contrary of previous works, this study concentrated on capturing interaction effects between wind turbine, atmospheric inflow, and complex terrains.

Infrasound generated by meteorological fronts: Observations and modeling

The results of study of the parameters of infrasound waves (amplitudes, coherences, grazing angles, azimuths, and horizontal phase speeds) detected during a passage of warm and cold fronts through the networks of microbarometers in Moscow region are presented. The observed effect of internal gravity waves on the coherence and phase speed of infrasound from meteorological fronts is analyzed. The differences found in the time dependences of the parameters of infrasound from warm and cold fronts that must be taken into account when detecting infrasound precursors of atmospheric storms are discussed. A possible mechanism for the generation of infrasound by the turbulent airstream flowing around the geometric irregularities of the meteorological front is proposed. [This work was supported by the Russian Science Foundation, Grant No. 21-17-00021.]

Infrasound Generation by Meteorological Fronts and Its Propagation in the Atmosphere

AbstractInfrasound parameters (amplitudes, coherences, grazing angles, azimuths, and horizontal phase speeds) derived during the passage of warm and cold fronts through the networks of microbarometers in the cities of Dubna and Moscow are presented. The significant differences observed in the temporal variations of the parameters of infrasound from warm and cold fronts are discussed. Such differences must be taken into account when detecting infrasound precursors of atmospheric storms. A possible mechanism for the generation of infrasound by the turbulent airstream flowing around the geometric irregularities of the meteorological front is proposed. The observed effect of internal gravity waves on the parameters of infrasound and its frequency spectrum is explained.

Some issues of monitoring and determining the category of gas activity of coal mines of Ukraine

Abstract. In the paper, the problems of performing mining operations in the mines with high content of gas in the seams are discussed. In the course of their mining, methane and other gases release, which are capable to burn and, together with air, can form explosive mixtures. Depending on the nature and intensity of methane emissions, it is necessary to undertake a set of additional measures in order to ensure explosion and fire safety in the underground space. Therefore, to carry on mining operations in the coal mines, it is obligatory to specify gas composition in the mine air and give the mine a category by methane. During these works, the following should be determined by means of the stationary automatic equipment and devices of periodic action: composition, rate, temperature and humidity of air and content of methane and carbon dioxide. Special attention should be focused on the control and detection of local accumulations of methane in the mine workings and in the seams. The local accumulations are especially relevant because workings in mines are usually ventilated by turbulent air streams. However, methane released in the working is mixed with air not immediately but after some time and at a certain distance from the source of methane release where its concentration in the cross section is equalized. As a result of monitoring and research carried out, a refined measurement procedure was provided for determining gas content in the coal seam and assigning a mine an actual category by methane. The results of checking gas content of some mines in Ukraine and assigning them a category by methane are presented. Besides, aerodynamic state of the coal massif was studied, assessed and provided with detailed explanations. As an example, some elements of calculations of the methane content in the Almaznaya Mine, Dobropolskoye Company of the DTEK “Dobropillyavugillya” for the year 2021 is considered. Since 2019, the Almaznaya Mine was classified as a mine with extremely high content of methane with emissions of 16,34 m3/t per 1 ton of dry ash-free mass Today, a seam l1 in the 3rd north longwall, horizon 550 m, is being developed. The seam l1 is explosive by coal dust and not prone to spontaneous combustion. In addition, telemetric data on the 1st north longwall of the seam l1, horizon 550 m, for August, 2020, are presented. Keywords: monitoring, methane, coal seam, mine category by methane, gas content, explosion and fire safety.

New Type of Draft Tube Spout-Fluid Bed. Part 2: Modeling and Design of the Acceleration Section of the Riser for the Pneumatic Transport of 1 mm Glass Spheres

A new type of draft tube spout-fluid bed (DTSFB) generically similar to a circulating fluidized bed (CFB) possesses a unique combination of capabilities as a fluid-particle contacting system or multiphase reactor. This paper focuses on the modeling of the acceleration section of the draft tube (a riser) of a DTSFB for the dilute phase pneumatic transport of 1 mm glass spheres in a turbulent air stream. An analytical expression for a dimensionless dynamic pressure gradient distribution in the acceleration section (y(ζ)) is derived from the solution of an isoperimetric problem of the calculus of variations. The gradient is shown to be a function of a single dimensionless parameter, which is the ratio of the dynamic pressure drop in the acceleration section and the dynamic pressure gradient in the nonacceleration section. It is shown that ∫01 y(ζ) dζ is maximized in the acceleration section of the riser. As a result, the pressure drop required to overcome the resisting forces in the acceleration section is minimized in any run. The pressure distribution obtained by integrating the pressure gradient is shown to be an excellent fit to experimental data. The modeling of the acceleration section is based on the one-dimensional, two-fluid continuity and momentum equations plus the variational pressure gradient distribution making it possible to calculate the solids fraction, gas and particle phase velocities, and effective drag coefficient distributions in the riser from five independent equations. The particle–wall friction factor in the model is calculated from a theory developed by the authors in a previous paper.

Olfactory receptor neuron coding in the turbulent realm

Insects are able to find their mates from the sparse pheromone patches transported by turbulent air streams. This source-finding ability is remarkable because the pheromone patches don’t point towards the source and because the temporal and concentration statistics encountered during the search are highly irregular. The knowledge of the coding dynamics at the single ORN level is presently incomplete and it seems mandatory to decipher these dynamics before further investigating the integration of the signal at higher levels of the olfactory system. A receptor that would attempt to infer the distance of a source from the detection dynamics of the pheromone patches would obviously benefit from the complete evolution of the pheromone concentration with time. Yet, it is possible to build a Bayesian model based on the known dynamics of the plume propagation [1] and to infer the distance from the temporal dynamics only. Hence, an interesting question is how much of the temporal dynamics of the patches can be encoded in the ORN signals? For example, the uncorrelated statistics of patch duration is sufficient for inferring the distance, yet including the correlations between the durations of detections and non-detections will greatly improve the decoding rate [2]. As a simplified framework, we investigated the dynamical olfactory coding of ORNs of a moth, Agrotis ipsilon, stimulated by puffs of pheromone (cis-7-dodecenyl acetate) of variable duration delivered at constant concentration. The spiking responses of ORNs to single puffs varying over four decades of durations (1ms-10s) were recorded and decoded. In the absence of precise knowledge on the decoding mechanism inside the antennal lobe and in higher neural structures of the insect brain, 3 decoding schemes were utilized, based on logistic regression, support vector machine and signal dependent Poisson firing model designed to include bursting dynamics. With this protocol the relative selectivity of ORNs coding with the variation of puff duration and thus the relative information transfer could be analyzed. Then, in order to investigate the possible coding dependency of the currently detected pheromone patch on previous patch detections, double puffs coding were investigated, similarly over four decades of durations. The evolution of the ORN coding showed that the detection of previous puffs influenced the coding of the current puff and hence that instantaneous decoding could bring information on the previous puff duration and timing. Furthermore, we quantified the relative (conditional) sensitivity of the instantaneous coding with respect to the duration and spacing of the previous puff. Interestingly, we also show that the “random spiking” dynamics bears a non-negligible amount of information on the past patch dynamics detection. The coding and decoding procedures were then evaluated on signals mimicking the temporal dynamics of patches in a turbulent stream. We found that training based on one patch and two patches allowed efficient and reliable decoding of patch dynamics in turbulent air streams. Finally, we quantified the amount of information encoded by ORNs about the duration, timing, and most importantly waiting time between consecutive pheromone puffs.

Computer-automated silica aerosol generator and animal inhalation exposure system

Inhalation exposure systems are necessary tools for determining the dose response relationship of inhaled toxicants under a variety of exposure conditions. The objective of this study was to develop an automated computer controlled system to expose small laboratory animals to precise concentrations of uniformly dispersed airborne silica particles. An acoustical aerosol generator was developed which was capable of re-suspending particles from bulk powder. The aerosolized silica output from the generator was introduced into the throat of a venturi tube. The turbulent high-velocity air stream within the venturi tube increased the dispersion of the re-suspended powder. That aerosol was then used to expose small laboratory animals to constant aerosol concentrations, up to 20 mg/m3, for durations lasting up to 8 h. Particle distribution and morphology of the silica aerosol delivered to the exposure chamber were characterized to verify that a fully dispersed and respirable aerosol was being produced. The inhalation exposure system utilized a combination of airflow controllers, particle monitors, data acquisition devices and custom software with automatic feedback control to achieve constant and repeatable exposure environments. The automatic control algorithm was capable of maintaining median aerosol concentrations to within ±0.2 mg/m3 of a user selected target concentration during exposures lasting from 2 to 8 h. The system was able to reach 95% of the desired target value in <10 min during the beginning phase of an exposure. This exposure system provided a highly automated tool for conducting inhalation toxicology studies involving silica particles.

Numerical investigation of electrohydrodynamic effects on the airflow through corrugated channels

To enhance the forced convection heat transfer of turbulent air stream inside the different corrugated channels, a numerical study has been conducted to explore the effect of electrohydrodynamic actuator. In this regard, a two-dimensional numerical approach has been developed to evaluate the average Nusselt number and friction factor. The results obtained show that, while the thermal enhancement factor without electrohydrodynamic is best with trapezoidal corrugation for flows in the low Reynolds number regime, the addition of electrohydrodynamic works best with rectangular corrugation.

Particle Aerosolisation and Break‐up in Dry Powder Inhalers: Evaluation and Modelling of the Influence of Grid Structures for Agglomerated Systems

This study aimed to investigate the influence of grid structures on the break-up and aerosol performance of a model inhalation formulation through the use of standardised entrainment tubes in combination with computational fluid dynamics (CFD). A series of entrainment tubes with grid structures of different aperture size and wire diameters were designed in silico and constructed using three-dimensional printing. The flow characteristics were simulated using CFD, and the deposition and aerosol performance of a model agglomerate system (496.3-789.2 µm agglomerates containing 3.91 µm median diameter mannitol particles) were evaluated by chemical analysis and laser diffraction, respectively. Analysis of the mannitol recovery from the assembly indicated that mass deposition was primarily on the grid structure with little before or after the grid. Mass deposition was minimal down to 532 µm; however, for smaller grid apertures, significant blockage was observed at all airflow rates (60-140 L · min(-1)). Analysis of the particle size distribution exiting the impactor assembly suggested that mannitol aerosolisation was dependent on the void percentage of the grid structure. It is proposed that initial particle-grid impaction results in a shearing force causing agglomerate fragmentation followed by immediate re-entrainment into the turbulent airstream within the grid apertures which causes further dispersion of the fine particles. Such observations have significant implications in the design of dry powder inhaler devices.

Interactions of rat whiskers with air currents: implications for flow sensing

Event Abstract Back to Event Interactions of rat whiskers with air currents: implications for flow sensing Venkatesh Gopal1*, Minwoo Kim2, Charles Chiapetta2, Joel Russ2, Michael Meaden3 and Mitra Hartmann4 1 Elmhurst College, Department of Physics and Biocenter Oulu,, United States 2 University of Illinois at Urbana Champaign, United States 3 Elmhurst College, United States 4 Northwestern University, United States Many species of mammals have a regular array of facial whiskers (mystacial vibrissae) that emerge from sensory follicles embedded in the cheek. Each whisker-follicle pair constitutes a highly sensitive mechano-transducer, and the whiskers are often used for the tactile exploration of objects. Rats, for example, actively sweep their whiskers against objects between 5 - 12 Hz in a behavior called "whisking." Using only whisking movements, a rat can tactually extract object features such as size, shape, orientation and texture. However, many animals with large and prominent vibrissae, such as dogs, do not actively whisk. Why, then, are the vibrissae so prominent, and so regularly arranged, even in species that do not actively whisk? We reasoned that animal nervous systems have evolved around the need to find food, water, and mates. For most mammals, the search for these resources is largely olfactory, requiring the detection of airborne odorants which are usually present at very low concentrations. The dispersal of an airborne odorant is strongly dependent on local air currents, which are generally turbulent and have complex flow patterns. Olfactory localization thus requires an animal to detect the chemical odorant, to sense wind direction, and then to integrate these chemical and fluid dynamic cues to make a decision on where to move next. We therefore hypothesized that in addition to their direct tactile function, whiskers may also serve as sensitive detectors of air currents, and that the rat’s vibrissal array can be used to measure information about local airflow. To test this hypothesis, we measured the interactions of vibrissae with air currents in anesthetized rats. Turbulent air streams were blown onto the vibrissae of an anesthetized rat at various angles. Whisker deflections were measured using high-speed video cameras at a frame rate of 1KHz. Whisker kinematic parameters were measured and compared across vibrissae on both sides of the face. Our preliminary results show significant differences in response frequency and amplitude across the right and left sides of the vibrissal array depending on the orientation of the air stream. We discuss these results in the context of odor localization behaviors. This work was supported by NSF awards IIS-0613568 and IOS-0818414 (MJZH) and an Elmhurst College Summer Research Collaboration Grant (VG, MM). Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session III Citation: Gopal V, Kim M, Chiapetta C, Russ J, Meaden M and Hartmann M (2010). Interactions of rat whiskers with air currents: implications for flow sensing. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00281 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Mar 2010; Published Online: 05 Mar 2010. * Correspondence: Venkatesh Gopal, Elmhurst College, Department of Physics and Biocenter Oulu,, Elmhurst, United States, vgopal@elmhurst.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Venkatesh Gopal Minwoo Kim Charles Chiapetta Joel Russ Michael Meaden Mitra Hartmann Google Venkatesh Gopal Minwoo Kim Charles Chiapetta Joel Russ Michael Meaden Mitra Hartmann Google Scholar Venkatesh Gopal Minwoo Kim Charles Chiapetta Joel Russ Michael Meaden Mitra Hartmann PubMed Venkatesh Gopal Minwoo Kim Charles Chiapetta Joel Russ Michael Meaden Mitra Hartmann Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Simulations of Evaporating Spray Jet in a Uniform Co-Flowing Turbulent Air Stream

Numerical simulations are performed on the flow of fine, polydisperse droplets of acetone ejected from a round jet of air into an ambient turbulent, uniform co-flowing air stream. The objective is to validate the numerical model by comparing the predictions with experimental measurements of a well defined evaporating spray configuration (Chen et al., Int. J. Multiphase Flow 32(2006), 389–412). The carrier-phase is considered in the Eulerian context, while the dispersed phase is tracked in the Lagrangian framework. Various interactions between the two phases are taken into account by means of a two-way coupling. The stochastic separated flow (SSF) model is adopted for the spray calculations. The gas-phase turbulence terms are closed using the standard k-ε model. The spray evaporation is described using a thermal model with an infinite-conductivity. Overall, very good agreement is observed in the comparisons of the computational predictions and experimental measurements. The predicted droplet number-mean axial velocity, r.m.s. of fluctuating velocity for the various droplet classes at different downstream locations exhibit a self-similarity downstream of the nozzle exit. Near the nozzle-exit (around z/djet = 5), the r.m.s. of droplet number mean axial fluctuating velocity attains a maximum within the shear layer near r/djet = 0.4–0.6 for different droplet classes. Further downstream, the peak shifts towards the axis. A similar variation is noticed in the Sauter mean diameter (SMD) distribution of the droplets. It is concluded that, a higher level of turbulence leads to a faster depletion of the smaller droplets, resulting in an increase in the local droplet-SMD in those regions.

KINEMATIC MODEL FOR YARN MOVEMENT IN TURBULENT AIR FLOWS

Abstract In the textile industry a tool is needed that can predict fibre and yarn movement in turbulent air streams. The Institut für Textiltechnik of RWTH Aachen University (ITA) has developed a yarn model that can be used to study the movement of single fibres and yarns in turbulent air flows. The kinematic model is described in this article. Special attention is paid to the aerodynamic forces that determine the flight path of fibres and yarns. The coefficient of drag tangential to the fibre axis ct was studied thoroughly using computational fluid dynamics (CFD). It is shown that the diameter has a strong influence on the wall shear stress. Neglecting this effect for thin fibres can lead to errors in the coefficient of drag of a factor of 500. The turbulence intensity also has an important influence on the boundary layer development, which also determines the coefficient of drag. The assumptions made for the yarn model were tested in an experiment in which yarn flight paths were detected with a high-speed video camera. The comparison to the simulation results confirms the usability of the yarn model.

Study of hydrogen auto-ignition in a turbulent air co-flow using a Large Eddy Simulation approach

Large Eddy Simulation (LES) is applied to the auto-ignition of an hydrogen jet issuing into a turbulent co-flowing air stream. A 19 step, 9 species detailed mechanism is used for modelling the chemical reactions. The influence of sub-grid fluctuations is accounted for by a sub-grid joint probability density function (PDF) for the reactive scalars. A Eulerian Stochastic Field method is used to solve the modelled form of the PDF transport equation. The model is able to reproduce ignition lengths and different regimes observed experimentally without adjustment of the sub-grid scale model parameters.

A Delicate Balance: Hovering Balloons in an Air Stream

Science museums and popular physics shows often exhibit a blower in whose air stream a ball is held hovering in equilibrium some distance above the jet's orifice. The weight of the ball, mg, is balanced by the drag force of the turbulent air stream, often written as ρCv2A, where ρ and v are the density and velocity of the air, A is the effective area of the ball, and C some drag coefficient depending, among other things, on the surface roughness. This paper describes a ball and balloons of various sizes supported stably stacked one above the other in a vertical air stream from a blower.

Large eddy simulation of hydrogen auto-ignition with a probability density function method

Large eddy simulation is applied to the auto-ignition of a hydrogen jet issuing into a turbulent co-flowing air stream. A 19 step, nine species detailed mechanism is used for reaction. The influence of sub-grid species concentration and temperature fluctuations are accounted for by a sub-grid joint PDF for the reactive scalars, obtained from solution of a modelled transport equation. The method is able to reproduce ignition lengths and different regimes observed experimentally without any adjustment or calibration of the model constants.

Problems in the classification of approximants

The aim of this paper is to show that the approximant feature refers to a phonetic class which includes other subcategories of sounds, such as semi-vowels, rhotics, laterals and a subset of consonants. The consonants – due to the lack of articulatory precision – keep neither the obligatory closure for stops nor the aerodynamic characteristics required to produce a turbulent airstream, as is characteristic of fricatives. I am referring to these sounds as [[Voiced bilabial fricative] [Voiced dental fricative] [Voiced palatal fricative] [Voiced velar fricative]]. Moreover, I suggest a new definition of the approximant feature, which points out that the outflow of non-turbulent airstream is caused by either the opening of the organs or the lack of articulatory precision, or even both phenomena together.

Increased levels of ambient fungal spores in Taiwan are associated with dust events from China

Fungi are ubiquitous in nature and their spores are often dispersed into the atmosphere through turbulent airstreams. As yellow sandstorm blown from deserts in China had affected the ambient air quality with increasing levels of ambient particulates, often including significant amounts of biologically active particles has therefore become imperative for concerns of their health implications. Our study was aimed to examine the effects of yellow sandstorm events on the fungal composition and concentrations in ambient air. Atmospheric fungal spores were continuously collected using Burkard Volumetric Spore Trap. Samples collected between December 2000 and April 2001 were selected for priority analysis from days when the yellow sandstorms were reported to affect Taiwan according to the Central Weather Bureau in Taiwan. The composition of dominant spores such as Basidiospore, Penicillium/Aspergillus, Nigrospora, Arthrinium, Curvularia, Rusts, Stemphylium, Cercospora, Pithomyces, and unidentified fungi were significantly higher than those of background days. The increase of Basidiospore, Penicillium/Aspergillus, Nigrospora, and those unidentified fungi seems to be significantly associated with the increase of ambient particulate levels with regression coefficients ranging from 0.887 to 31.98. Our study has identified increasing ambient concentrations during sandstorm episodes are observed for some major fungi, Basidiospore, Penicillium, Aspergillus, and those unidentified fungi and the trends of the increase seems to associate with ambient particulate levels. Further efforts to clarify the relationship between those high fungal spore exposures and clinical adverse health effects are suggested in the future. In addition, effects of climatic factors and other particulate levels on the variation of ambient fungal spore levels are also desired in further study. Additional monitoring of ambient fungal spores in the first line of west coastline is hoped to assist in differentiating changes of local spores and contribution for sandstorms during the episodes.

An experimental investigation of Curle's theory of aerodynamic noise generation by a stationary body in a turbulent air stream

Bies et al. (J. Sound Vib. 204(4) (1997) 631) investigated Curle's theory (Proc. R. Soc. Ser. A 231 (1955) 505) published in 1955 over a wide range of flow speeds from about 50–200 m/s and found only partial agreement with the experimental data. Here the experimental investigation has been repeated allowing the data to be recorded in a format amenable to analysis, which was not previously possible. Reintroduction of a term neglected by Curle has been found necessary as Curle's compact source condition ensures so low a radiation impedance that the effect cannot be detected in the jet background noise. The reintroduction of the term, which has been neglected, allows his analysis to include radiation from sources not compact but less than half a wavelength in characteristic dimension. It is shown that the power ratio defined as the measured sound power divided by Curle's amended prediction converges to about 3 whereas Curle predicts that the power ratio should converge to 1 as the wave number converges to zero. The introduction of the empirically determined constant 3 into Curle's prediction brings the measurements into very good agreement with prediction over the entire range of the non-dimensional wave numbers from about 0.4 to 3.2.