Pitching airfoil study and freestream effects for wind turbine applications

A Horizontal Axis Wind Turbine (HAWT) experiences imbalanced loads when it operates under yaw loads. For each blade element of the aerodynamically imbalanced rotor, not only is the angle of attack unsteady, but also the corresponding incident velocity, a fact usually unfairly ignored. For the unsteady angle of attack, a pitch oscillating airfoil has been studied experimentally and numerically when 3.5×10⁴<Re<10⁵. For small wind tunnel airfoils, Particle Image Velocimetry (PIV) was utilized to determine the aerodynamic loads and the pressure field where other measurement techniques are either intrusive or very challenging. For dynamic airfoils in highly separated flow fields, i.e., deep dynamic stall phenomena, loads were calculated successfully based on the control-volume approach by exploring ways to reduce the level of uncertainties in particular for drag estimation. Consecutive high resolution PIV velocity fields revealed that increasing the reduced frequency was followed by an enriched vortex growth time and phase delay as well as a reduced number of vortices during upstroke motion. Moreover, the locations of the vortices after separation were influenced by each other. Laminar separation bubble height also showed a reducing trend as the reduced frequency increased. The nature of the vortex sheet vortices before stall were explored in two Reynolds numbers, with and without laminar separation bubbles, at low angles of attack. For all cases, a vortex sheet was the result of random vortex sheding while a longer vortex sheet was more favorable for lift augmentation. A wake study and averaged drag calculation at low angles of attack were also performed with Laser Doppler Anemometry (LDA) for Re=10⁵. For the unsteady incident velocity, longitudinal freestream oscillations have been studied numerically, since experimental study of an unsteady freestream is challenging. In this regard, the streamwise freestream velocity and pitch angle of incidence oscillated with the same frequency in a wide range of phase differences. Changing the phase difference caused variation of the results, including significantly augmented and dramatically damped dynamic stall loads, both increasing and decreasing trends for vortex growth time during phase increase and shifted location of the maximum loads. The results showed strong dependency on the velocity and acceleration of the freestream during dynamic stall and the dynamic stall characteristics differed significantly from those of the steady freestream states. The results also demonstrated consistent trends regardless of the airfoil shape and the Reynolds number while Re=10⁵ and 10⁶. The vortex study presented here not only provides information about the unsteady aerodynamic forces, but also knowledge regarding airfoil noise generation and distributed flow for downstream objects beyond wind turbine applications.1 yea

Cheilosia cumanica (Dip.: Syrphidae), a new record of flower flies from Iran

Cheilosia (Convocheila) cumanica Szilady is recorded for the first time from Iran. This species is similar to C. laticornis Rondani morphologically; however, is distinguished from this close species in male by hairy eyes (bare in C. laticornis) and in female by longer third antennal segment that is three times longer than the second segment (less than 2.5 times in C. laticornis). This finding increase the number of Cheilosia species known from Iran to seven

First record of the genus Milesia (Dip.: Syrphidae: Eristalinae) from Iran

با نمونه‌برداری از منطقه جنگلی حسین‌آباد استان قزوین، نمونه‌ای از جنس Milesia Latreille جمع‌آوری و با نام علمی Milesia semiluctifera (Villers, 1789) تشخیص داده شد. این اولین گزارش از جنس و گونه مذکور از ایران می‌باشد

First record of Leucopis (Leucopis) spyrothecae (Dip.: Chamaemyiidae) from Iran

طی نمونه‌برداری‌های انجام‌شده از دشمنان طبیعی شته‌ها در اردبیل طی سال‌های 91-1390، لاروهای مگس شکارگر از خانواده Chamaemyiidae در حال تغذیه از شته Pemphigus spyrothecae Passerini روی درخت صنوبر، Populus nigra (L.)، جمع‌آوری و پس‌ از پرورش در شرایطی مشابه شرایط محل جمع‌آوری، حشرات کامل به نام Leucopis (Leucopis) spyrothecae Raspi, 2003 شناسایی شدند. این گونه برای اولین‌بار از ایران گزارش می‌شود

The first report of silver fly, Leucopis argentata (Dip.: Chamaemyiidae) from Iran

در طی نمونه‌برداری‌های انجام‌شده از دشمنان طبیعی شته‌ها در اصفهان در سال 1385، لاروهای مگس شکارگر از خانواده‌ی Chamaemyiidae در حال تغذیه از شته‌ی Hyalopterus pruni (Geoffroy) روی گیاه نی Phragmites sp. جمع‌آوری شد و پس از پرورش آن‌ها در آزمایشگاه، حشرات کامل توسط دکتر Gaimari در آمریکا با نامLeucopis argentata Heeger شناسایی شد. طبق اطلاعات موجود، این گونه تخصص میزبانی روی شته‌ی H. pruni، و صرفاً روی گیاه نی Phragmites spp.، دارد

Determination of economic injury level for pod borers of chickpea in dry farms of Ilam province

Chickpea, one of the major pulses, is planted together with wheat as a custom rotation in Ilam province. Pod borers are serious pest of chickpea and their direct damage to seed reduce yield considerably. Annually, farmers use much pesticide against the pest without any clue. In order to determine economic injury level (EIL), a semi-field study was started in 2000 to calculate this parameter based on a complete randomized block design with five treatments and four replications. Emerged larvae in the surrounding chickpea fields were collected and released in cages at the density of 0, 10, 20, 40, 80 larvae per square meter. Various factors (e. g. yield, damaged and total seeds) were measured and analyzed at harvesting time. Results show that if market value of chickpea and cost of management (treatment) are considered 3500 rials per kg and 150000 rials, respectively, then EIL will be 3.9 larvae per square meter (four rows with a length of one meter)

Report of the genus Parhelophilus Grischner (Dip.: Syrphidae) from Iran

The species, Pharhelophilus versicolor (Fabricius), was collected during the study of the syrphid flies (Dip.: Syrphidae) fauna in Sangachin and Shijan, Guilan province. Further confirmation was made by Menno Reemer. The genus and species is newly recorded from Iran

Two new records of Chalcidoidea (Hymenoptera) from Iran

دو گونه از زنبورهای پارازیتویید بالاخانواده Chalcidoidea (Hymenoptera) و همچنین، روابط میزبان- پارازیتوییدی آن‌ها روی گیاه Scariola orientalis Boissier برای اولین‌بار از ایران گزارش می‌شوند: گونه Pteromalus sequester Walker (Hym.: Pteromalidae) پارازیتویید داخلی، انفرادی و لاروی-‌ شفیرگی مگس Hypenidium oculatum (Becker) (Dip.: Tephritidae) و گونه Discodes rubtzovi Sugonjaev (Hym.: Encyrtidae) پارازیتویید شپشک Cerococcus longipilosus (Archangelskaya) (Hem.: Cerococcidae)

A survey of alfalfa aphids and their natural enemies in Isfahan, Iran, and the effect of alfalfa strip-harvesting on their populations

During a two-year (2004-2005) survey of alfalfa aphids and their natural enemies in Isfahan, a total of four aphid species and 58 species of their natural enemies comprised of 45 predatory species, 11 parasitoid species and two species of parasitic mites were collected and identified. Moreover, five hyperparasitoid species were collected. On each sampling date, six 20-sweep samples were taken using a 38cm-diameter sweep-net and also six 20-stem were sampled. The results showed that the mean percent of Hippodamia variegata Goeze, Nabis spp., Deraeocoris spp., Orius spp., Geocoris spp. and aphid parasitoids in strip-harvested field were 38%, 95%, 119%, 57%, 100% and 122%, respectively; higher than those in conventionally-harvested field. In contrast, the mean percent of Acyrthosiphon pisum (Harris) and Therioaphis trifolii (Monell) forma maculata (Buckton) were 24% and 28%, respectively; lower in strip-harvested field than in conventionally-harvested field