INVESTIGATION OF UNSTEADY EXCITATION EFFECTS ON AERODYNAMIC PROPERTIES OF AIRFOILS

In this paper, the techniques to manage and control the flow over airfoils by using the external unsteady excitations are investigated. The mechanisms of these excitation effects are also explored. The principal goal of this study is to gain a better understanding and to find the possible ways for enhancing the aerodynamic efficients. The experimental investigations are carried out in two low-speed wind tunnels. The test models are two dimensional airfoils with different section geometries. Four means of excitations have been used in these experiments. (1) The pitch oscillation of the airfoil high-angle-of-attack situation. (2) The moving surface effects of the airfoil with a leading edge rotating cylinder. (3) Oscillating leading edge flaperon. (4) Small oscillating spoiler located near the leading edge of the airfoil. The lift, drag and pitch moment coefficients are measured in these experiments. But, we will put the emphasis only on the 'dynamic amplifying effects' on aerodynamic lift in this paper. Results obtained indicate that the beneficial aerodynamic effects of section lift increase can be obtained at the high angle of attack near stall regime, as long as the frequency and amplitute of the excitation are appropriately selected.

Development of sorting methods based on physical and aerodynamic properties of off-ground harvested almonds

This research was conducted to develop an effective approach to sort off-ground harvested almonds for efficient drying based on their physical and aerodynamic properties.Three popular varieties were studied,including Nonpareil,Monterey,and Fritz.The insect damage,axial dimensions,weight ratio,moisture content,bulk density and terminal velocity of in-hull almonds,in-shell almonds and loose hull at harvest were measured.The results indicated that the insect infestation percentage in the off-ground harvested almonds ranged from 2.5%to 6.3%,which was about half of those in the conventional on-ground dried almonds.Loose hulls and in-hull almonds had higher moisture content and wider moisture distribution than those of in-shell almonds,suggesting that sorting of the almonds and drying them separately are necessary for efficient handling and processing.Thickness was the smallest axial dimension of an almond,and thus could be used for sorting.The cut-off sizes of 16.5 mm,21.3 mm and 21.1 mm could separate 100%of the in-shell almonds from the rest for Nonpareil,Monterey and Fritz varieties,respectively,as the first step.In the second step,applying terminal velocities of 12.3 m/s,11.8 m/s and 12.2 m/s could efficiently separate the in-hull almonds and loose hulls for Nonpareil,Monterey and Fritz varieties,respectively.Overall,up to 76.7%of the loose hulls could be removed,and up to 3.3%in-hull almonds may be lost during the sorting process.The experimental results provided important information for developing efficient sorting and drying methods with improved throughput,energy efficiency,better quality and safety of off-ground harvested almonds.

The effect of ethanol on the habit and in vitro aerodynamic results of dry powder inhalation formulations containing ciprofloxacin hydrochloride

In the case of dry powder inhalation systems(DPIs),the development of carrierfree formulations has gained increased attention.Thereby,spray-drying is a promising technology and is widely used to produce carrier-free DPIs.Numerous works have been published about the co-spray-drying of active ingredients with various solid excipients and their effect on the physicochemical characteristics and aerodynamic properties of the formulations.However,only a few studies have been reported about the role of the solvents used in the stock solutions of spray-dried formulations.In the present work,DPI microcomposites containing ciprofloxacin hydrochloride were prepared by spray-drying in the presence of different ethanol concentrations.The work expresses the roughness,depth and width of the dimples for particle size as a novel calculation possibility,and as a correlation between the MMAD/D_(0.5)ratio and correlating it with cohesion work,these new terms and correlations have not been published–to the best of our knowledge–which has resulted in gap-filling findings.As a result,different proportions of solvent mixtures could be interpreted and placed in a new perspective,in which the influence of different concentrations of ethanol on the habit of the DPI formulations,and thus on in vitro aerodynamic results.Based on these,it became clear why we obtained the best in vitro aerodynamic results for DPI formulation containing 30%ethanol in the stock solution.

Possibility of Solid Hydrometeor Growth Zone Identification Using Radar Spectrum Width

In this study,the correlation between simulated and measured radar velocity spectrum width(σ_(v))is investigated.The results show that the dendrites growth zones(DGZs)and needles growth zones(NGZs)mostly contain dendrites(DN)and needles(NE),respectively.Clearσ_(v) zones(1.1<σ_(v)(m s^(-1))<1.3 and 0.3<σ_(v)(m s^(-1))<0.7 for the DGZ and NGZ,respectively)could be identified in the case studies(27 and 28 February 2016)near altitudes corresponding to temperatures of–15°C and–5°C,according to the Japan Meteorological Agency and mesoscale model reanalysis data.Oblate particles with diverse particle shapes were observed in the DGZ withσ_(v)>1.2 m s^(-1),a differential reflectivity(ZDR)higher than 0 dB,and a cross-correlation coefficient(ρhv)less than 0.96.In contrast,prolate particles with relatively uniform shapes were observed in the NGZ withσ_(v)<0.6 m s^(-1),a ZDR less than 0 dB,andρhv higher than 0.97.The simulation results show that the DN exhibited a largerσ_(v) compared to the NE,and this observedσ_(v) was strongly dependent on the wind fluctuations(v’)due to turbulence or wind shear.In contrast,the NE exhibited a significantly smallσ_(v)~0.55 m s^(-1),which converges irrespective of v’.In addition,a strong correlation between the measuredσ_(v) values at five radar elevation angles(θ=6.2°,9.1°,13.1°,19°,and 80°)and those simulated in this study confirmed the significance of the analysis results.

Rarefied gas effect in hypersonic shear flows

Recently,as aerodynamics was applied to flying vehicles with very high speed and flying at high altitude,the numerical simulation based on the Navier-Stokes(NS)equations was found that cannot correctly predict certain aero-thermo-dynamic properties in a certain range of velocity and altitude while the Knudsen number indicates that the flow is still in the continuum regime.As first noted by Zhou and Zhang(Science in China,2015),the invalidity of NS equations for such flows might be attributed to an non-equilibrium effect originating from the combined effects of gas rarefaction and strong shear in the boundary-layer flows.In this paper,we present the scope,physical concept,mathematical model of this shear non-equilibrium effect in hypersonic flows,as well as the way of considering this effect in conventional computational fluid mechanics(CFD)for engineering applications.Several hypersonic flows over sharp bodies and blunt bodies are analyzed by the proposed new continuum model,named direct simulation Monte Carlo(DSMC)data-improved Navier-Stokes(DiNS)model.