Aerodynamic Variables Research Articles

Phonation Quotient Using Three Aerodynamic Instruments in the Disordered Voice

The purpose of this study was to examine measures of phonation quotient (PQ) in two groups of persons with voice disorders using three different aerodynamic instruments representing low-tech and high-tech options. Prospective, repeated measures design. Two groups of patients with a diagnosis of vocal fold paralysis/paresis (n = 9) or benign vocal fold lesions (n = 8) were assessed for maximum phonation time and vital capacity obtained from three aerodynamic instruments: a hand-held analog windmill-type spirometer; a hand-held digital spirometer; and the Phonatory Aerodynamic System (PAS), Model 6600. PQ was calculated using vital capacity from each instrument along with maximum phonation time. Univariate ANOVAs were performed to test for the main effects of disorder and instrument on derived PQ. Paired samples t tests were performed post hoc to investigate any significant main effects. Pearson product-moment correlation was performed to assess measurement reliability (parallel forms) between the instruments. Statistically significant differences were found for measures of PQ as a function of disorder but not instrument type. There was not a significant interaction effect between disorder and instrument type. Strong positive correlations were present between all three instruments for measures of PQ. PQ was sensitive to differences in airflow as a function of disorder etiology (paralysis/paresis vs benign lesions). This clinical measure of laryngeal function can be used as a low-cost substitute in the absence of a pneumotachograph. These results are consistent with previous literature reporting data from adult male and female speakers with normal voice quality, and support the use of low-tech options for measurement of basic aerodynamic variables associated with voice production.

Evolution of Body Mass in Bats: Insights from a Large Supermatrix Phylogeny

Bats are atypical small mammals. Size is crucial for bats because it affects most aerodynamic variables and several key echolocation parameters. In turn, scaling relationships of both flight and echolocation have been suggested to constrain bat body size evolution. Previous studies have found a large phylogenetic effect and the inclusion of early Eocene fossil bats contributed to recover idiosyncratic body size change patterns in bats. Here, we test these previous hypotheses of bat body size evolution using a large, comprehensive supermatrix phylogeny (+800 taxa) to optimize body size and examine changes reconstructed along branches. Our analysis provides evidence of rapid stem phyletic nanism, an ancestral value stabilized at 12 g for crown-clade Chiroptera followed by backbone stasis, low-magnitude changes inside established families, and massive body size increase at accelerated rate in pteropodid subclades. Total variation amount explained by pteropodid subclades was 86.3%, with most changes reconstructed as phyletic increases but also apomorphic decreases. We evaluate these macroevolutionary patterns in light of the constraints hypothesis, and in terms of both neutral and adaptive evolutionary models. The reconstructed macroevolution of bat body size led us to propose that echolocation and flight work as successive, nested constraints limiting bat evolution along the body size scale.

Aerodynamic test with self-propelled scale model

This research presents a new experimental technique for the testing prototypes of aerodynamic devices of heavy freight vehicles. This technique allows the evaluation and recording of aerodynamic variables, being an alternative to the experimental limitations present in a wind tunnel, or the complexity and costs associated to the real-scale experimental test. For this new methodology a radio-controlled reduced-scale model is used, equipped with different instruments for recording aerodynamic variables. The experiment was performed at the runway in the Chilean Air Force Base in Santiago, at a speed of 90 [km/hr]. The results demonstrate that this technique allows recreating more realistic conditions of the aerodynamic phenomena, obtaining reliable values for the aerodynamic drag, at a low cost.

A Computerized Tomography Study of Vocal Tract Setting in Hyperfunctional Dysphonia and in Belting

Vocal tract setting in hyperfunctional patients is characterized by a high larynx and narrowing of the epilaryngeal and pharyngeal region. Similar observations have been made for various singing styles, eg, belting. The voice quality in belting has been described to be loud, speech like, and high pitched. It is also often described as sounding "pressed" or "tense". The above mentioned has led to the hypothesis that belting may be strenuous to the vocal folds. However, singers and teachers of belting do not regard belting as particularly strenuous. This study investigates possible similarities and differences between hyperfunctional voice production and belting. This study concerns vocal tract setting. Four male patients with hyperfunctional dysphonia and one male contemporary commercial music singer were registered with computerized tomography while phonating on [a:] in their habitual speaking pitch. Additionally, the singer used the pitch G4 in belting. The scannings were studied in sagittal and transversal dimensions by measuring lengths, widths, and areas. Various similarities were found between belting and hyperfunction: high vertical larynx position, small hypopharyngeal width, and epilaryngeal outlet. On the other hand, belting differed from dysphonia (in addition to higher pitch) by a wider lip and jaw opening, and larger volumes of the oral cavity. Belting takes advantage of "megaphone shape" of the vocal tract. Future studies should focus on modeling and simulation to address sound energy transfer. Also, they should consider aerodynamic variables and vocal fold vibration to evaluate the "price of decibels" in these phonation types.

Nasal Structural and Aerodynamic Features That May Benefit Normal Olfactory Sensitivity

Nasal airflow that effectively transports ambient odors to the olfactory receptors is important for human olfaction. Yet, the impact of nasal anatomical variations on airflow pattern and olfactory function is not fully understood. In this study, 22 healthy volunteers were recruited and underwent computed tomographic scans for computational simulations of nasal airflow patterns. Unilateral odor detection thresholds (ODT) to l-carvone, phenylethyl alcohol (PEA) and d-limonene were also obtained for all participants. Significant normative variations in both nasal anatomy and aerodynamics were found. The most prominent was the formation of an anterior dorsal airflow vortex in some but not all subjects, with the vortex size being significantly correlated with ODT of l-carvone (r = 0.31, P < 0.05). The formation of the vortex is likely the result of anterior nasal morphology, with the vortex size varying significantly with the nasal index (ratio of the width and height of external nose, r = -0.59, P < 0.001) and nasal vestibule "notch" index (r = 0.76, P < 0.001). The "notch" is a narrowing of the upper nasal vestibule cartilage region. The degree of the notch also significantly correlates with ODT for PEA (r = 0.32, P < 0.05) and l-carvone (r = 0.33, P < 0.05). ODT of d-limonene, a low mucosal soluble odor, does not correlate with any of the anatomical or aerodynamic variables. The current study revealed that nasal anatomy and aerodynamics might have a significant impact on normal olfactory sensitivity, with greater airflow vortex and a narrower vestibule region likely intensifying the airflow vortex toward the olfactory region and resulting in greater olfactory sensitivity to high mucosal soluble odors.

Acute Effects of Velopharyngeal Resistance Training on Aerodynamic Patterns: A Pilot Study on Healthy Individuals

Objective: The use of continuous positive airway pressure (CPAP) as a form of resistance training has shown some promise in strengthening velopharyngeal (VP) closure muscles in individuals with hypernasality (i.e., excessive nasal resonance perceived in speech). Systematic research on appropriate dosage, however, is largely lacking in the literature. The present pilot study explored the effects of an individual session on the speakers’ VP function. Methods: Healthy volunteers with normal VP function participated in the study. The Exercise group (n=6) underwent 10 individual CPAP sessions with varying intranasal pressure levels as overload during speech. The Control group (n=6) underwent one session with no exercise. VP measurements including aerodynamic and pressure-flow timing variables were obtained immediately before (Pre) and after (Post) each individual CPAP session. Results: No statistically significant differences were found between groups (Exercise vs. Control) or across varying overload levels (5, 6, 7, 8, and 9 cmH2O) in Pre-Post mean changes of the VP measurements. Data rather illustrated that, despite the short-term disturbance caused by resistance training, the participants were able to maintain consistency in the control of VP function, which appeared to be further augmented by exercise with sufficient overload. Conclusion: Results provided pilot data on the acute effects of VP resistance training on healthy speakers’ VP function using the range of overload typically employed in the established CPAP therapy protocol. Future clinical research may provide insights into adequate selection of exercise intensity for individual patients based on their working capacities of the VP mechanism.

Phonation Quotient in Women: A Measure of Vocal Efficiency Using Three Aerodynamic Instruments

The purpose of this study was to examine measures of vital capacity and phonation quotient across three age groups in women using three different aerodynamic instruments representing low-tech and high-tech options. This study has a prospective, repeated measures design. Fifteen women in each age group of 25-39 years, 40-59 years, and 60-79 years were assessed using maximum phonation time and vital capacity obtained from three aerodynamic instruments: a handheld analog windmill type spirometer, a handheld digital spirometer, and the Phonatory Aerodynamic System (PAS), Model 6600. Phonation quotient was calculated using vital capacity from each instrument. Analyses of variance were performed to test for main effects of the instruments and age on vital capacity and derived phonation quotient. Pearson product moment correlation was performed to assess measurement reliability (parallel forms) between the instruments. Regression equations, scatterplots, and coefficients of determination were also calculated. Statistically significant differences were found in vital capacity measures for the digital spirometer compared with the windmill-type spirometer and PAS across age groups. Strong positive correlations were present between all three instruments for both vital capacity and derived phonation quotient measurements. Measurement precision for the digital spirometer was lower than the windmill spirometer compared with the PAS. However, all three instruments had strong measurement reliability. Additionally, age did not have an effect on the measurement across instruments. These results are consistent with previous literature reporting data from male speakers and support the use of low-tech options for measurement of basic aerodynamic variables associated with voice production.

A stochastic approach to rhotic variation in Spanish codas

A stochastic analysis using aerodynamic and temporal variables is presented to explain tap/trill variation in Spanish codas. Simultaneous intraoral pressure (Po), translingual flow (F) and acoustic signals were obtained for two native speakers of Peninsular Spanish performing a rate-controlled reiterative task. Data were analyzed using linear mixed effects models fitted with random effects for speaker and repetition. The results show that tongue height and tongue anteriority of the preceding vowel affect the timing and aerodynamic parameters of the rhotic onset gesture, but the phonological specifications of the following consonants do not. Continuous variables were fit into a Bayesian logit regression model using noninformative priors which shows that tap/trill variation in coda can be predicted in part from aerodynamic and temporal parameters. Such a proposal obviates the need to resort to positional constraints to explain tap/trill variation in codas.

The evolution of avian wing shape and previously unrecognized trends in covert feathering.

Avian wing shape has been related to flight performance, migration, foraging behaviour and display. Historically, linear measurements of the feathered aerofoil and skeletal proportions have been used to describe this shape. While the distribution of covert feathers, layered over the anterior wing, has long been assumed to contribute to aerofoil properties, to our knowledge no previous studies of trends in avian wing shape assessed their variation. Here, these trends are explored using a geometric-morphometric approach with landmarks describing the wing outline as well as the extent of dorsal and ventral covert feathers for 105 avian species. We find that most of the observed variation is explained by phylogeny and ecology but shows only a weak relationship with previously described flight style categories, wing loading and an investigated set of aerodynamic variables. Most of the recovered variation is in greater primary covert feather extent, followed by secondary feather length and the shape of the wing tip. Although often considered a plastic character strongly linked to flight style, the estimated ancestral wing morphology is found to be generally conservative among basal parts of most major avian lineages. The radiation of birds is characterized by successive diversification into largely distinct areas of morphospace. However, aquatic taxa show convergence in feathering despite differences in flight style, and songbirds move into a region of morphospace also occupied by basal taxa but at markedly different body sizes. These results have implications for the proposed inference of flight style in extinct taxa.

The effect of time trial cycling position on physiological and aerodynamic variables

To reduce aerodynamic resistance cyclists lower their torso angle, concurrently reducing Peak Power Output (PPO). However, realistic torso angle changes in the range used by time trial cyclists have not yet been examined. Therefore the aim of this study was to investigate the effect of torso angle on physiological parameters and frontal area in different commonly used time trial positions. Nineteen well-trained male cyclists performed incremental tests on a cycle ergometer at five different torso angles: their preferred torso angle and at 0, 8, 16 and 24°. Oxygen uptake, carbon dioxide expiration, minute ventilation, gross efficiency, PPO, heart rate, cadence and frontal area were recorded. The frontal area provides an estimate of the aerodynamic drag. Overall, results showed that lower torso angles attenuated performance. Maximal values of all variables, attained in the incremental test, decreased with lower torso angles (P < 0.001). The 0° torso angle position significantly affected the metabolic and physiological variables compared to all other investigated positions. At constant submaximal intensities of 60, 70 and 80% PPO, all variables significantly increased with increasing intensity (P < 0.0001) and decreasing torso angle (P < 0.005). This study shows that for trained cyclists there should be a trade-off between the aerodynamic drag and physiological functioning.

Onboard System Identification for Improved Flight Control of UAS

A new technique is proposed to select and estimate the significant aerodynamic parameters of micro unmanned aerial systems from ight data to improve the dynamical qualities of an indirect adaptive ight control system. The aerodynamic variables are estimated in the frequency domain using the angle of attack and sideslip air-ow angles which in turn are estimated using an extended Kalman filter. Parameter estimation and selection procedures of significant aerodynamic parameters are based on linear regression model structures with forward orthogonal least square (OLS) and error reduction ratio (ERR) methods. When combined, the methods can be applied to create an indirect adaptive ight control system. This new approach is verified by comparing the results with those obtained from conventional sensor data, including air ow angle measurements. Performance comparison of the system identification methods show that the proposed technique can obtain the same quality of ight performance as if the airow measurements were available. The new methods are demonstrated in simulation of a benchmark ight performance experiment on an Aerosonde UAV.

Investigating the aerodynamic performance of a model offshore floating wind turbine

Understanding the impact of wave-induced dynamic effects on the aerodynamic performance of Offshore Floating Wind Turbines (OFWTs) is crucial towards developing cost-effective floating wind turbines to harness wind energy in deep water sites. The complexity of the wake of an OFWT has not yet been fully understood. Measurements and numerical simulations are essential. An experiment to investigate the aerodynamics of a model OFWT was undertaken at the University of Malta. Established experimental techniques used to analyse fixed HAWTs were applied and modified for the floating turbine condition. The effects of wave induced motions on the rotor aerodynamic variables were analysed in detail. An open source free-wake vortex code was also used to examine whether certain phenomena observed in the experiments could be reproduced numerically by the lifting line method. Results from hot wire measurements and free-wake vortex simulations have shown that for OFWTs surge-induced torque fluctuations are evident. At high λ a discrepancy in the mean CP between the fixed and floating conditions was found from measurements and numerical simulations.

Nonlinear Aeroelastic Behavior of Slender Wings Considering a Static Stall Model Based on Wagner Function

The aeroelastic behavior of high aspect ratio wings in an incompressible flow is investigated. The nonlinear nonplanar bending-bending-twisting motions of beam theory is used for the structural equations assuming large deformations with small strains, small Poisson effects, inextensional beam theory, and linear elastic material characteristics by neglecting warping and shear deformation. An Unsteady nonlinear aerodynamic static stall model based on the Wagner function is introduced and then is used for determination of aerodynamic loading of the wing. In this aerodynamic model, the static lift curve vs. angle of attack is approximated by a piece-wise curve and for each linear part of this curve a corrected Wagner theory is used. Combining these two types of formulation yields fully nonlinear integro-differentials aeroelastic equations of motion. The governing equations will be solved to predict the nonlinear aeroelastic response of a wing in the stall and post stall regions using Galerkin's method and a numerical method without the need of adding any aerodynamic state-space variables and their corresponding equations. The obtained equations are solved for some test cases and the obtained results are compared with the results given in the literature. Also a study is done to show effects of nonlinear aerodynamic static stall model on the limit cycle oscillations.

Sensitivity of Landsat‐Scale Energy Balance to Aerodynamic Variability in Mountains and Complex Terrain

AbstractThe speed and direction of air flow through complex terrain are difficult to define. Both impact sensible and latent heat flux exchanges at the surface. Evapotranspiration (ET) models such as Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC™) estimate ET as a residual of the surface energy process and are thus sensitive to aerodynamics, including terrain‐induced impacts on roughness governing convective heat transfer (H). There is a need to explore the sensitivities of H estimation and thereby ET estimation to wind speed and terrain roughness in mountainous areas and to determine the merit of operating complex mesoscale wind field models in conjunction with the energy balance process. A sensitivity analysis is explored in METRIC where we increased wind speed in proportion to a relative elevation parameter and we increased aerodynamic roughness to assimilate impacts of relative terrain roughness, estimated in proportion to standard deviation of elevation within a 3 km locality. These aerodynamic modifications increased convective heat transfer in complex terrain and reduced estimated ET. In other sensitivity runs, we reduced estimated wind speed on estimated leeward slopes. Estimated ET with and without these sensitivity adjustments is shown for mountainous areas of Montana and Nevada. Changes in ET ranged from little change (&lt;5%) for lower slopes to about 30% reductions on windward slopes and 25% increases on leeward slopes for some mid to high elevations in the Montana application.

Assessing climate change induced modification of Penman potential evaporation and runoff sensitivity in a large water-limited basin

Potential evaporation (Ep) reflects the combined effects of four key meteorological variables: (i) net radiation (Rn); (ii) wind speed (u); (iii) relative humidity (rh); and (iv) air temperature (Ta). Here, attribution analysis was conducted to investigate the contribution of the four key meteorological variables to changes of a physically-based Ep in a large water-limited basin, the Yellow River Basin (YRB), China. Then the influences of these changes, and precipitation (P) changes, on streamflow (Q) were explored analytically. Results show that: (i) Ep presented different temporal trends for the water yielding region (WYR) and water consuming region (WCR) with a overall changes of +0.16 mm a−2 and −0.66 mm a−2 during 1961–2010, respectively; (ii) trend analysis of Ep and the four key meteorological variables at the basin scale showed that increasing trend in Ta increased Ep during 1961–2010, while changes in Rn and u increased the 1961–1979 Ep rate and reduced it during 1980–1994 and 1995–2010; (iii) revealed by attribution analysis, Ep increased by changes in Ta and rh and reduced by changes of Rn and u in both WYR and WCR, in all, Ep rate presented positive and negative trends in the WYR and WCR, respectively; (iv) the changes of Q and actual evaporation (E) are much more sensitive to changes in P than the changes in Ep; and (v) of critical importance for water resource management of the YRB changes in Q are mainly attributed to changes in catchment-specific parameter (n) and P, while Ep reduced Q in WYR and increased Q in WCR. These results indicated that the causes of trend of Ep rates, influenced by combined effects of radiative and aerodynamic variables should be explicitly explained using fully physically based Ep formulations. Additionally, in the water-limited YRB, changes of Q are primarily controlled by the changes in catchment conditions, and secondarily by hydroclimatic factors where the available water (P) rather than energy condition (Ep) is more important. Better understanding all of these relationships and how they have varied will help water resource management in a changing climate.

Nonlinear Aeroelastic Behavior of Slender Wings Considering a Static Stall Model Based on Wagner Function

The aeroelastic behavior of high aspect ratio wings in an incompressible flow is investigated. The nonlinear nonplanar bending-bending-twisting motions of beam theory is used for the structural equations assuming large deformations with small strains, small Poisson effects, inextensional beam theory, and linear elastic material characteristics by neglecting warping and shear deformation. An Unsteady nonlinear aerodynamic static stall model based on the Wagner function is introduced and then is used for determination of aerodynamic loading of the wing. In this aerodynamic model, the static lift curve vs. angle of attack is approximated by a piece-wise curve and for each linear part of this curve a corrected Wagner theory is used. Combining these two types of formulation yields fully nonlinear integro-differentials aeroelastic equations of motion. The governing equations will be solved to predict the nonlinear aeroelastic response of a wing in the stall and post stall regions using Galerkin's method and a numerical method without the need of adding any aerodynamic state-space variables and their corresponding equations. The obtained equations are solved for some test cases and the obtained results are compared with the results given in the literature. Also a study is done to show effects of nonlinear aerodynamic static stall model on the limit cycle oscillations.

An efficient method for nonlinear aeroelasticy of slender wings

This paper aims the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with the linear unsteady aerodynamic model. High aspect ratio and flexibility are the specific characteristic of this type of wings. Wing flexibility, coupled with long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore, a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear general flexible Euler–Bernoulli beam equations is used for structural modeling. Unsteady linear aerodynamic strip theory based on the Wagner function is used for determination of aerodynamic loading on the wing. Combining these two types of formulation yields nonlinear integro-differentials aeroelastic equations. Using the Galerkin’s method and a mode summation technique, the governing equations will be solved by introducing a numerical method without the need to adding any aerodynamic state space variables and the corresponding equations related to these variables of the problem. The obtained equations are solved to predict the aeroelastic response of the problem. The obtained results for a test case are compared with those of some other works and show a good agreement between results.

The temporal trends of reference evapotranspiration and its sensitivity to key meteorological variables in the Yellow River Basin, China

AbstractThe temporal trends of reference evapotranspiration (ETref) reflect the combined effects of radiometric and aerodynamic variables, such as global solar radiation (Rs), wind speed, relative humidity and air temperature. The temporal trends of annual ETref during 1961–2006 calculated by Penman‐Monteith method were explored and the underlying causes for these trends were analysed in the Yellow River Basin (YRB). The contributions of key meteorological variables to the temporal trend of ETref were detected using the detrended method and then sensitivity coefficients of ETref to meteorological variables were determined. For ETref, positive trends in the upper, middle and whole of YRB, and significant negative trend (P = 0·05) in the lower basin were obtained by the linear fitted model. Significant increasing trend (P = 0·05) in air temperature and decreasing trend in relative humidity were the main causes for the increasing trends of ETref in the upper, middle and whole basins. For the whole basin, the increasing trend of ETref was mainly caused by the significant increase (P = 0·05) in air temperature and to a lesser extent by a decrease in the relative humidity, decreasing trends of Rs and wind speed reduced ETref. The spatial distribution of sensitivity coefficients addressed that the sensitive regions for ETref response to the changes of the four meteorological variables are different in the YRB. The sensitive region lay in the upper basin for Rs, the northwest portion of the middle basin for wind speed, the south portion of YRB for relative humidity and the west portion of the upper basin and the north portion of the middle basin for air temperature. In general, Rs was the most sensitive variable for ETref, followed by relative humidity, air temperature and wind speed in the basin scale. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Aerodynamic/Structural Optimization of a Training Aircraft Wing

This paper presents a coupled aerodynamic/structural optimization model for a light training, low subsonic aircraft wing. Four optimization strategies have been developed and tested. The first was based on minimization of the total weight of the main wing structure subject to strength, stiffness and aeroelastic constraints. The second strategy considered maximization of the critical flight speed at which divergence occurs, while the third one focused on minimization of the wing drag/lift ratio as a measure of improving aerodynamic efficiency without violating structural weight requirements. The last strategy was based on minimization of the power consumption, which has worked very well and shown balanced improvements in both the aerodynamic and structural efficiencies of the wing under the imposed design constraints. The aerodynamic variables are chosen to be the wing aspect and chord taper ratios, while the structural variables encompassed spar locations, spar flange cross-sectional areas, shear webs and covering skin thicknesses of the main wing box section. The optimization problem has been formulated as a nonlinear mathematical programming problem solved by invoking the MATLab optimization Toolbox routines, which implements the method of feasible directions. Structural, aerodynamic and aeroelastic analyses assumed slender one-dimensional configuration. It makes use of the quasi-steady strip theory in evaluating aerodynamic loads and the classical engineering theories of bending and torsion in calculating stresses and deformations. Results have shown that the approach implemented inthis study can be efficient in producing improved designs in a reasonable computer time. The proposed model has succeeded in arriving at the optimum solutions showing significant improvements in the needed design goals as compared with a baseline wing design.

Aerodynamic Measurements: Normative Data for Children Ages 6:0 to 10:11 Years

Normative measures of open quotient, speed quotient, maximum flow declination rate (MFDR), and subglottal pressure were determined for 75 children between the ages of 6 years 0 months and 10 years 11 months. The participants produced a sustained /a/ at low, comfort, and high pitches for a minimum of 5 seconds, and five to seven repetitions of /pa/ at low, comfort, and high pitches. No statistically significant differences were found in the mean measures of any aerodynamic variables (open quotient, speed quotient, maximum flow declination rate, subglottal pressure) between the frequency levels (low, comfort, high pitches). Also, no strong evidence (P > .05) exists that age or sex effect differed between the frequency levels (low, comfort, high) for any of the aerodynamic measures. For /a/ response tasks, mean open quotient measures increased slightly from low to comfort frequency and from comfort to high frequency. Mean speed quotient measures showed minimal differences between low and comfort frequency, with decreased mean measures for high frequency. Mean MFDR measures increased from low to comfort frequency and from comfort to high frequency. Mean subglottal pressure measures increased slightly from low to comfort frequency and from comfort to high frequency.