Three-dimensional rotor flow calculation

U radu je prikazan numerički model za izračunavanje aerodinamičkih sila na glavnom rotoru helikoptera. Model je nestacionaran i u potpunosti trodimenzionalan. Lopatica rotora helikoptera se smatra kruti telom, a njeno kretanje u toku rotacije je modelovano tako da rotor predstavlja model rotora helikoptera Aerospatiale SA 341 "Gazela" (lopatica je povezana sa glavom rotora preko zgloba mahanja, zgloba za promenu koraka i pseudo-zabacujućeg zgloba). Strujno polje oko lopatice se proračunava u nizu sukcesivnih azimutnih položaja. Strujno polje oko rotora je modelovano kao potpuno trodimenzionalno, nestacionarno i potencijalno. Lopatica je aerodinamički modelovana kao tanka noseća površina. Vrtložni krak rotora se sastoji od pravolinijskih vrtložnih niti konstantne vrtložnost koje napuštaju izlaznu ivicu lopatice u određenim azimutnim uglovima. Vrtložni trag se modeluje kao slobodan (free-wake model), a njegov oblik se izračunava u svakom trenutku vremena na osnovu jednostavnog kinematskog zakona primenjenog u kolokacionim tačkama vrtložnog traga. Promena oblika vrtložnog traga se izračunava samo u blizini lopatice, tj. za određeni broj revolucija rotora. Vrtložni elementi traga se modeluju sa jezgrom vrtloga. Poluprečnik jezgra je nepromenljiv tokom vremena, a zavisi jedino od gradijenta cirkulacije u tački u kojoj vrtložni trag napušta lopaticu.This paper presents the numerical model developed for rotor blade aerodynamics loads calculation. The model is unsteady and fully three-dimensional. Helicopter blade is assumed to be rigid, and its motion during rotation is modeled in the manner that rotor presents a model of rotor of helicopter Aerospatiale SA 341 "Gazelle" (the blade is attached to the hub by flap, pitch and pseudo lead-lag hinges). Flow field around the blade is observed in succession of several azimuth locations. Flow field around helicopter rotor is modeled as fully three-dimensional, unsteady and potential. Blade aerodynamics is modeled using a lifting surface model. Rotor wake is generated from the straight elements of constant vorticity, released from the trailing edge, at fixed azimuth angles. These vortices represent both trailed and shed wake components, and are allowed to freely convect along local velocity vectors. Wake is modeled as free one, and its shape at certain moment can be calculated from simple kinematics laws applied on collocation points of the wake. Wake distortion is calculated only in the rotor near-field, i.e. in finite number of rotor revolutions. Vortex elements are modeled with vortex core. The radius of the vortex core is assumed independent of time, and it depends on circulation gradient at the point of vortex element released from the blade

Three-dimensional rotor flow calculation

U radu je prikazan numerički model za izračunavanje aerodinamičkih sila na glavnom rotoru helikoptera. Model je nestacionaran i u potpunosti trodimenzionalan. Lopatica rotora helikoptera se smatra kruti telom, a njeno kretanje u toku rotacije je modelovano tako da rotor predstavlja model rotora helikoptera Aerospatiale SA 341 "Gazela" (lopatica je povezana sa glavom rotora preko zgloba mahanja, zgloba za promenu koraka i pseudo-zabacujućeg zgloba). Strujno polje oko lopatice se proračunava u nizu sukcesivnih azimutnih položaja. Strujno polje oko rotora je modelovano kao potpuno trodimenzionalno, nestacionarno i potencijalno. Lopatica je aerodinamički modelovana kao tanka noseća površina. Vrtložni krak rotora se sastoji od pravolinijskih vrtložnih niti konstantne vrtložnost koje napuštaju izlaznu ivicu lopatice u određenim azimutnim uglovima. Vrtložni trag se modeluje kao slobodan (free-wake model), a njegov oblik se izračunava u svakom trenutku vremena na osnovu jednostavnog kinematskog zakona primenjenog u kolokacionim tačkama vrtložnog traga. Promena oblika vrtložnog traga se izračunava samo u blizini lopatice, tj. za određeni broj revolucija rotora. Vrtložni elementi traga se modeluju sa jezgrom vrtloga. Poluprečnik jezgra je nepromenljiv tokom vremena, a zavisi jedino od gradijenta cirkulacije u tački u kojoj vrtložni trag napušta lopaticu.This paper presents the numerical model developed for rotor blade aerodynamics loads calculation. The model is unsteady and fully three-dimensional. Helicopter blade is assumed to be rigid, and its motion during rotation is modeled in the manner that rotor presents a model of rotor of helicopter Aerospatiale SA 341 "Gazelle" (the blade is attached to the hub by flap, pitch and pseudo lead-lag hinges). Flow field around the blade is observed in succession of several azimuth locations. Flow field around helicopter rotor is modeled as fully three-dimensional, unsteady and potential. Blade aerodynamics is modeled using a lifting surface model. Rotor wake is generated from the straight elements of constant vorticity, released from the trailing edge, at fixed azimuth angles. These vortices represent both trailed and shed wake components, and are allowed to freely convect along local velocity vectors. Wake is modeled as free one, and its shape at certain moment can be calculated from simple kinematics laws applied on collocation points of the wake. Wake distortion is calculated only in the rotor near-field, i.e. in finite number of rotor revolutions. Vortex elements are modeled with vortex core. The radius of the vortex core is assumed independent of time, and it depends on circulation gradient at the point of vortex element released from the blade

Optimization of wind farm layout

U radu je predstavljen metod određivanja optimalnih položaja vetrogeneratora u okviru farme, postavljene na terenu proizvoljne orografije. Optimalni položaji pojedinačnih vetrogeneratora su određeni tako da se postigne njihova maksimalna efikasnost. Metod je zasnovan na genetskom algoritmu kao optimizacionoj tehnici. Aerodinamički proračun vetrogeneratora je izveden na nestacionarnom potencijalnom strujnom polju. Lopatice vetrogeneratora su modelirane kao vrtložne površine, a vrtložni trag je modeliran upotrebom 'freewake' metode. Optimizacioni model je razvijen za dve funkcije cilja. Obe funkcije koriste ukupnu energiju dobijenu iz farme kao jednu od ključnih promenljivih. Druga funkcija cilja uključuje i ukupno ulaganje u svaku pojedinačnu turbinu, tako da optimizacioni proces uključuje i ukupan broj vetrogeneratora kao promenljivu. Metod je testiran na nekoliko proizvoljnih konfiguracija terena, pri čemu je posebna pažnja posvećena izboru parametara genetskog algoritma, kako bi se postigle povoljne performanse optimizacionog procesa.This paper presents a method for determination of optimum positions of single wind turbines within the wind farms installed on arbitrary configured terrains, in order to achieve their maximum production effectiveness. This method is based on use of the genetic algorithm as optimization technique. The wind turbine aerodynamic calculation is unsteady, based on the blade modeled as a vortex lattice and a free-wake type airflow behind the blade. Optimization method is developed for two different fitness functions. Both functions use the total energy obtained from the farm as one of the key variables. The second also involves the total investments in a single wind turbine, so the optimization process can also include the total number of turbines as an additional variable. The method has been tested on several different terrain configurations, with special attention paid to the overall algorithm performance improvements by selecting certain genetic algorithm parameters

Aerodynamic shape optimization of guided missile based on wind tunnel testing and computational fluid dynamics simulation

This paper presents modcation of the existing guided missile which was done by replacing the existing front part with the new five, while the rear part of the missile with rocket motor and missile thrust vector control system remains the same. The shape of all improved front parts is completely different from the original one. Modification was performed based on required aerodynamic coefficients for the existing guided missile. The preliminary aerodynamic configurations of the improved missile front parts were designed based on theoretical and computational fluid dynamics simulations. All aerodynamic configurations were tested in the T-35 wind tunnel at the Military Technical Institute in order to determine the final geometry of the new front parts. The 3-D Reynolds averaged Navier-Stokes numerical simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. Experimental results of the axial force, normal force, and pitching moment coefficients are presented. The computational results of the aerodynamic loads of a guided missile model are also given, and agreed well with

Conceptual Design and Flight Envelopes of a Light Aircraft for Mars Atmosphere

In this paper is presented a new conceptual design of the light aircraft for Mars atmosphere, ALPEMA. It allows atmospheric dropping (aeroshell), as well as direct take-off from Martian surface. Complex atmosphere demanded for simplified yet efficient wing geometry, capable of maximizing Lift-to-Drag ratio. Martian atmospheric pressure, density, temperature and speed of sound variations, demand a scrutinized powerplant choice. Efficient aspect ratio and drag polar lead to optimal flight envelopes as a proof of sustainability of ALPEMA project. Special performances and basic aerodynamics provide boundaries and constraints of the project, in line with similar approaches. Chosen propeller allows for ALPEMA to use maximum power capabilities of its engine, described through Vmin and Vmax, which are significant inputs for flight envelope. Envelope provides effective width and profile for a variety of possible missions. ALPEMA’s specific propeller and engine are a certain comparative advantage, together with its flight envelope

Aeronautical Engineering

Aerospace engineering is the primary branch of engineering concerned with the design, construction and science of flight vehicle. Consequently, they are usually the products of various technological and engineering disciplines including aerodynamics, propulsion, avionics, materials science, structural analysis and manufacturing. These technologies are collectively known as aerospace engineering. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering. It is typically a large combination of many disciplines that makes up aeronautical engineering. The development and manufacturing of a modern flight vehicle is an extremely complex process and demands careful balance and compromise between abilities, design, available technology and costs. Aeronautical engineers design, test, and supervise the manufacture of aircraft. They also develop new technologies for use in aviation. Aeronautical Engineering is a chapter that encompasses challenging areas such as aircraft design, light-weight structures, stability and control of aeronautical vehicles, propulsion systems, and low and high speed aerodynamics. The field also covers their aerodynamic characteristics and behaviors, airfoil, control surfaces, lift, drag, and other properties. The chapter will include all our research and published papers

Flight to Mars: Envelope simulation in a ground based high-performance human centrifuge

Ovo istraživanje ima za cilj da doprinese slanju prve ljudske posade na Mars. U radu je simulirana anvelopa leta na Marsa u centrifugi visokih performansi. Visoka G-opterećenja prilikom poletanja, iskustvo nulte i mikrogravitacije, može rezultirati mnogim psiho-fiziološkim poremećajima kod astronauta. Ovo uslovljava potrebu za posebnim protokolima obuke. Predložena je anvelopa leta za prvu ljudsku misiju na Mars i simulirana u funkciji G-opterećenja. U radu su predloženi profili obuke. Poseban akcenat je stavljen na fazu lansiranja sa zemlje, kao i na fazu ponovnog ulaska i sletanja. Ponovni ulazak može biti posebno opasan, uz mnogo veća ubrzanja. Precizna simulacija zahteva pravilno podešavanje rotacionih uglova centrifuge. Prilagođavanje uglova se vrši u cilju smanjenja bočnih i poprečnih G-opterećenja. Ova studija će, nadamo se, pomoći da se čovečanstvo približi snu “Ljudi na Marsu”.This research is an effort to contribute to the human exploration of Mars by simulating phases of the Mars flight envelope in a high performance human centrifuge. The crushing sensation experienced at high-G levels during take-off, the experience of zero and microgravity, can result in many psycho-problems to astronauts, obviating the need for realistic training protocols. The flight envelope for the first manned mission to Mars is proposed, and simulated in terms of G- load. Some training profile suggestions are given. A special emphasis is placed on the Earth launch phase, and on the Earth re-entry and landing phase. Re-entry can be especially dangerous with much higher accelerations. Accurate simulation requires a proper adjustment of rotational angles of the centrifuge. Angle adjustments are made in order to minimize side-Gy and transverse-Gx load. This study will hopefully help to move faster towards the dream of “Humans on Mars”

Quadcopter altitude estimation using low-cost barometric, infrared, ultrasonic and LIDAR sensors

Cilj ovog istraživanja je procena različitih low-cost senzora za merenje visine leta bespilotne letelice sa više rotora na malim visinama. Primenjene su metode filtriranja podataka i druge metode u cilju optimizacije performansi i tačnosti merenja senzora. Izvšrena su merenja visine leta, a podaci su uskladišteni za kasniju analizu u odnosu na stvarnu visinu leta. Izračunati su stepeni korelacije i srednja kvadratna greška u merenju senzora sa ciljem procene rada senzora. Na osnovu rezultata istraživanja moguće je odrediti izbor adekvatnog senzora za ovu specifičnu primenu. Ovo istraživanje je pokazalo da je u uslovima ovog eksperimenta najbolje rezultate imao lidar senzor Garmin LIDAR-Lite V3HP i senzor Bosch Sensortech BME280 sa mogućnošću istovremenog merenja vlažnosti vazduha, atmosferskog pritiska i temperature.The goal of this research is to assess the different low-cost sensors for flight altitude measuring of a multirotor UAV at low altitude flight. For optimizing the sensor performances and accuracy, data filtering and other methods were applied. The flight altitude data were collected and stored for later analysis with reference to the true altitude. The correlation coefficient and the mean squared error were calculated in order to assess the sensors' performance. On the basis of the results of the study, it was possible to determine the choice of the adequate sensor for this specific use. The study showed that the best characteristics for this experiment conditions had the Garmin LIDAR-Lite V3HP sensor and the Bosch Sensortech BME280 that combined air humidity, atmospheric pressure, and air temperature sensor

Initial development of the hybrid semielliptical-dolphin airfoil

Iosif Taposu has formulated a mathematical model and generated a family of air-foils whose geometry resembles the dolphin shape. These airfoils are characterized by a sharp leading edge and experiments have proven that they can achieve better aerodynamic characteristics at very high angles of attack than certain classical airfoils, with the nose geometry inclined downwards. On the other hand, they have not been applied to any commercial general aviation aircraft. The authors of this paper have been motivated to compare the aerodynamic characteristics of widely used NACA 2415 airfoil with Taposu???s Dolphin that would have the same princi-pal geometric characteristics. A CFD calculation model has been established and applied on NACA 2415. The results were compared with NACA experiments and very good agreements have been achieved in the major domains of lift and polar curves. The same CFD model has been applied on the counterpart Dolphin 2415. Results have shown that the Dolphin has a slightly higher lift/drag ratio in the lift coefficient domain 0.1-0.35 than NACA. On the other hand, at higher and lower lift coefficients, its aerodynamic characteristics were drastically below those of the NACA section, due to the unfavorable influence of the Dolphin???s sharp nose. A series of the Dolphin???s leading edge modifications has been investigated, gradually improving its aerodynamics. Finally, version M4, consisting of about 70% of Dol-phin???s original rear domain and 30% of the new nose shape, managed to exceed the NACA???s characteristics, thus paving the way to investigate the Dolphin hybrids that could be suitable for the general aviation industry