We present large-eddy simulation (LES) of flow past different airfoils with
$Re_{c}$
, based on the free-stream velocity and airfoil chord length, ranging from
$10^{4}$
to
$2.1\times 10^{6}$
. To ...avoid the challenging resolution requirements of the near-wall region, we develop a virtual wall model in generalized curvilinear coordinates and incorporate the non-equilibrium effects via proper treatment of the momentum equations. It is demonstrated that the wall model dynamically captures the instantaneous skin-friction vector field on arbitrary curved surfaces at the resolved scale. By combining the present wall model with the stretched-vortex subgrid-scale model, we apply the wall-modelled LES approach to three different airfoil cases, spanning different geometrical parameters, different attack angles and low to high
$Re_{c}$
. The numerical results are verified with direct numerical simulation (DNS) at low
$Re_{c}$
, and validated with experiment data at higher
$Re_{c}$
, including typical aerodynamic properties such as pressure coefficient distributions, velocity components and also more challenging measurements such as skin-friction coefficient and Reynolds stresses. All comparisons show reasonable agreement, providing a measure of validity that enables us to further probe simulation results into aspects of flow physics that are not available from experiments. Two techniques to quantify hitherto unexplored physics of flows past airfoils are employed: one is the construction of the anisotropy invariant map, and the second is skin-friction portraits with emphasis on flow transition and unsteady separation along the airfoil surface. The anisotropy maps for all three
$Re_{c}$
cases, show clearly that a portion of the flow field is aligned along the axisymmetric expansion line, corresponding to the turbulent boundary layer log-law behaviour and the appearance of turbulent transition. The instantaneous skin-friction portraits reveal a monotonic shrinking of the near wall structure scale. At
$Re_{c}=10^{4}$
, the interaction between the primary separation bubble and the secondary separation bubble contributes to turbulent transition, similar to the case of flow past a cylinder. At higher
$Re_{c}=10^{5}$
, the primary separation breaks into several small separation bubbles. At even higher
$Re_{c}=2.1\times 10^{6}$
, near the turbulent separation, the skin-friction lines show small-scale reversal flows that are similar to those observed in DNS of the flat plate turbulent separation. A notable feature of turbulent separation in flow past an airfoil is the appearance of turbulence structures and small-scale reversal flows in the spanwise direction due to the vortex shedding behaviour.
The aim of this article is to model CFD (Computational Fluid Dynamics modeling), a spray dryer, for which experimental studies were conducted, and the general parameters of the drying process in the ...software environment ANSYS, FLUENT were determined. The numerical model should meet most requirements, such as the modeling of spray dryers . Thus, the purpose of the basic model is to provide the principles of a modern industrial approach to the modeling of spray dryers at moderate computational costs, while laying the foundation for further development and evaluation of relevant aspects of modeling spray systems equipped with disk sprayers.
•Aerodynamic properties of hexadecagonal section models by wind tunnel tests.•Effects induced by rounded corners, ancillaries and ladder.•Role of Reynolds number and turbulence intensity is ...investigated.•Non-negligible values of lift coefficient are obtained.•Susceptibility to galloping for 16-sided polygonal section is discussed.
This paper evaluates and discusses the aerodynamic properties of a 16-sided polygonal cylinder with imperfections and ancillaries investigated by wind tunnel tests. Two sectional models with different size have been realized, reproducing the peculiarities of real structures, such as the rounded corners, local protuberance due to weld bead, cables, ducts and the external ladder. The models have been subjected to static tests to measure the mean force coefficients and the Strouhal number varying angle of attack, flow velocity, turbulence intensity focusing on the effects of the imperfections and ancillaries on the aerodynamic loads with consideration of Reynolds number effects. The results provide an estimate of the aerodynamic coefficients for this type of elements, quantify the influence of geometrical and flow properties on the aerodynamic behaviour and point out the sensitivity of such polygonal cross-section to galloping instability.
Soccer balls are typically constructed from 32 pentagonal and hexagonal panels. Recently, however, newer balls named Cafusa, Teamgeist 2, and Jabulani were respectively produced from 32, 14, and 8 ...panels with shapes and designs dramatically different from those of conventional balls. The newest type of ball, named Brazuca, was produced from six panels and will be used in the 2014 FIFA World Cup in Brazil. There have, however, been few studies on the aerodynamic properties of balls constructed from different numbers and shapes of panels. Hence, we used wind tunnel tests and a kick-robot to examine the relationship between the panel shape and orientation of modern soccer balls and their aerodynamic and flight characteristics. We observed a correlation between the wind tunnel test results and the actual ball trajectories, and also clarified how the panel characteristics affected the flight of the ball, which enabled prediction of the trajectory.
Bats show a remarkable ecological diversity that is reflected both in dietary and foraging guilds (FGs). Cranial ecomorphological adaptations linked to diet have been widely studied in bats, using a ...variety of anatomical, computational and mathematical approaches. However, foraging‐related ecomorphological adaptations and the concordance between cranial and postcranial morphological adaptations remain unexamined in bats and limited to the interpretation of traditional aerodynamic properties of the wing (e.g. wing loading WL and aspect ratio AR). For this reason, the postcranial ecomorphological diversity in bats and its drivers remain understudied. Using 3D virtual modelling and geometric morphometrics (GMM), we explored the phylogenetic, ecological and biological drivers of humeral morphology in bats, evaluating the presence and magnitude of modularity and integration. To explore decoupled patterns of variation across the bone, we analysed whole‐bone shape, diaphyseal and epiphyseal shape. We also tested whether traditional aerodynamic wing traits correlate with humeral shape. By studying 37 species from 20 families (covering all FGs and 85% of dietary guilds), we found similar patterns of variation in whole‐bone and diaphyseal shape and unique variation patterns in epiphyseal shape. Phylogeny, diet and FG significantly correlated with shape variation at all levels, whereas size only had a significant effect on epiphyseal morphology. We found a significant phylogenetic signal in all levels of humeral shape. Epiphyseal shape significantly correlated with wing AR. Statistical support for a diaphyseal‐epiphyseal modular partition of the humerus suggests a functional partition of shape variability. Our study is the first to show within‐structure modular morphological variation in the appendicular skeleton of any living tetrapod. Our results suggest that diaphyseal shape correlates more with phylogeny, whereas epiphyseal shape correlates with diet and FG.
Bat humeral morphology exhibits patterns of variation associated with differences in foraging behaviour and phylogeny. This study is the first to show within‐structure modular morphological variation in the appendicular skeleton of any living tetrapod.
Various types of combustion-related particles in the size range between 100 and 850
nm were analyzed with an aerosol mass spectrometer and a differential mobility analyzer. The measurements were ...performed with particles originating from biomass burning, diesel engine exhaust, laboratory combustion of diesel fuel and gasoline, as well as from spark soot generation. Physical and morphological parameters like fractal dimension, effective density, bulk density and dynamic shape factor were derived or at least approximated from the measurements of electrical mobility diameter and vacuum aerodynamic diameter. The relative intensities of the mass peaks in the mass spectra obtained from particles generated by a commercial diesel passenger car, by diesel combustion in a laboratory burner, and by evaporating and re-condensing lubrication oil were found to be very similar. The mass spectra from biomass burning particles show signatures identified as organic compounds like levoglucosan but also others which are yet unidentified. The aerodynamic behavior yielded a fractal dimension (
D
f) of 2.09
±
0.06 for biomass burning particles from the combustion of dry beech sticks, but showed values around three, and hence more compact particle morphologies, for particles from combustion of more natural oak. Scanning electron microscope images confirmed the finding that the beech combustion particles were fractal-like aggregates, while the oak combustion particles displayed a much more compact shape. For particles from laboratory combusted diesel fuel, a
D
f value of 2.35 was found, for spark soot particles,
D
f
≈
2.10. The aerodynamic properties of fractal-like particles from dry beech wood combustion indicate an aerodynamic shape factor
χ that increases with electrical mobility diameter, and a bulk density of 1.92
g
cm
−3. An upper limit of
χ
≈
1.2 was inferred for the shape factor of the more compact particles from oak combustion.
Delivery of food and drug molecules is a challenging field of research with growing interests. Due to concerns on solubility, stability, and bioavailability, numerous techniques have been explored to ...identify effective and sustainable approaches. The large surface area and wide blood supply made the lungs a prominent route for the delivery of therapeutic molecules. Several drug molecules have been effectively delivered through the pulmonary route, and this review focuses on the pulmonary delivery of food-derived therapeutic molecules through aerosols. Various methods have been used to fabricate aerosols; their mechanism of deposition and absorption in the lungs involves intricacies in terms of a range of factors including their physical and aerodynamic properties, apart from the conditions of the body. This review attempts to elaborate on these aspects, apart from providing a status report on the current scenario of delivering therapeutic molecules through the pulmonary route. Importantly, highlighting regulatory aspects, challenges associated with the delivery of food-derived molecules such as aerosols are presented, giving lead for directions for future research.
Abstract
The use of state estimation techniques offers a means of inferring rotor effective wind speed from standard measurements of wind turbines. Typical wind speed estimators rely upon a ...pre‐computed quasi‐steady aerodynamic mapping, which describes the relationship between pitch angle and tip‐speed ratio and the power coefficient. In practice, the static mapping does not capture the influence of turbine structural dynamics and atmospheric turbulence, inevitably resulting in poor performance of the wind speed estimation. In addition, the turbine aerodynamic properties might not be easily accessible. Thus, this paper presents a rotor effective wind speed estimation method that obviates the requirement for prior knowledge of turbine power coefficients. Specifically, the proposed method exploits a simple actuator disc model, where the aerodynamic power and thrust coefficients can be characterized in terms of axial induction factors. Based on this insight and standard turbine measurements, real‐time estimation of rotor effective wind speed and axial induction factors can then be achieved using a simplified turbine drive‐train model and an extended Kalman filter. In addition, the actuator disc model can be updated easily over time by calibrating solely two correction factors. Thus, the proposed algorithm presents an alternative for estimating the rotor effective wind speed, which is valuable for numerous applications, for example, LiDAR‐assisted control and coherence studies.
•Time-domain method for prediction of 3DOF buffeting response of a tall building.•Experimental extraction of aerodynamic sectional properties for 3 cross-sections.•Comparison of predicted and ...aeroelastic-model response and aero-damping in ABL Wind.•Parametric study on effects of taper and cross-section on tall building response.•Proposed method can be used for mega-tall structures, uniform/non-uniform in height.
A time-domain method to calculate the buffeting response of a rectangular tall building (AR of B/D = 1.5 and H/D = 6) in along-wind, across-wind and torsional degrees of freedom using 2D aerodynamic sectional properties is presented here. The aerodynamic sectional properties were identified first using wind tunnel section models. Aerodynamic damping, which is critical in wind-induced response analysis of tall buildings, was calculated using the identified aeroelastic derivatives (flutter derivatives) and validated by comparing with those extracted directly from the response measurements of aeroelastic models of the tall building. A good agreement between the numerically simulated responses and the experimental measurements of an aeroelastic model (1:175 scale) shows the capability of the proposed method in the prediction of generalized 3DOF buffeting response of tall buildings in a wide range of wind speeds. Furthermore, the response of a tall building with two other cross-sectional shapes, circular and elliptical, was calculated using the developed method and compared amongst the three cross-sectional shapes to study the effect of cross section on buffeting response. The relative dependency of buffeting response of a tall building along each of the 3DOF on cross section, wind speed as well as angle of attack was assessed. Finally, the effect of taper on tall building’s buffeting response was studied using the developed method which showed that taper could significantly reduce the wind-induced response of tall buildings. The time-domain method to assess wind loads and buffeting response of tall buildings based on experimentally or theoretically derived aerodynamic properties of two-dimensional sections, as presented here, provides a viable and perhaps the only alternative to methods based on aeroelastic model tests and CFD simulations.
Avian trans‐Saharan migrants travelling long distances and crossing ecological barriers experience different constraints in terms of time, energy and safety than short‐/medium‐distance migrants ...without barrier‐crossings. As such, natural selection shapes the aerodynamic properties of these groups differently. Yet, to the best of our knowledge, we lack information on whether natural selection has contributed to reducing energetic flight costs through generally lower body mass in trans‐Saharan migrants. To fill parts of this gap, we investigated this eco‐morphological pattern in 5,410 individuals of 22 Palearctic songbird species ranging from short‐/medium‐distance to trans‐Saharan migrants. We used individual size‐independent scaled lean body mass values based on wing length as a measure of body size and, for the first time, precisely determined lean body mass values by direct measurements via quantitative magnetic resonance technology. Scaled lean body mass for a given body size was significantly higher in short‐/medium‐distance migrants than in trans‐Saharan migrants. Although scaled lean body mass significantly decreased with increasing migration distance in short‐/medium‐distance migrants, no such effect was found in trans‐Saharan migrants. Our results thus show an eco‐morphological pattern relating species’ lean body mass not only to migration distance but also to migration group. This suggests that selective effects of the presence/absence of ecological barriers and/or of a threshold level for migration distance on migrant birds may be more important than the linear continuum of migration distance per se.
In 22 Palearctic songbird species, lean body mass for a given body size was significantly higher in short‐/medium‐distance migrants than in trans‐Saharan migrants. This observed eco‐morphological pattern suggests that selective effects of the presence/absence of ecological barriers and/or of a threshold level for migration distance on migrant birds may be more important than the linear continuum of migration distance per se.
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