The core of the short takeoff and landing problem in thrust-vectoring V/STOL vehicles is the tilt angle control of the thrust vector nozzles. This work resolves it by figuring out the optimal tilt ...angle time history with optimization methods. Since the optimization process is constrained by the transition corridor of the vehicle and the mission requirements, the transition corridor is firstly established by the AES theory with the longitudinal model of the V/STOL protype, where the jet-induced effect of the 3BSD nozzle and the lift fan are especially considered. In addition, the control redundancy caused by the multiple physical control actuators is addressed by a suitable control allocation and flight-mode-based control strategy, which ensures a smooth conversion. By establishing appropriate mission references and optimization constraints, the optimal control strategy and the corresponding transition process are obtained, based on the direct inverse and SQP algorithms.
Enhancement in the aerodynamic performance of wings and airfoils is very notable when Active Flow Control (AFC) is applied to Short Take-off and Landing aircraft (STOL). The present numerical study ...shows the application of steady, pulsed and synthetic tangential jets applied to the plain flap shoulder of a modified NASA Trapezoidal Wing. Pulsed jets are modeled by sinusoidal and square waveforms while synthetic jets are modeled only by pure sine waveform. The freestream airflow conditions are Mach number equal to 0.2 and Reynolds number equal to 4.3 million based on the mean aerodynamic chord. The presented simulations are two-dimensional and based on RANS for steady jet cases and URANS for pulsed and synthetic cases, compiled with the open-source suite SU2 and adapted for time varying boundary conditions. Numerical results for modified configurations based on the same baseline wing profile considering different leading edges, jet slot height, flap position, blowing mass flow, type and frequency of the jets are presented. Curves of pressure coefficient distribution revealed a substantial influence upstream of the AFC, around the slat and main element. The jet slot height analysis showed that the lift gain is also influenced by the slot size due to the change of the local flow velocity considering the same blowing momentum coefficient. Regarding the jet frequency, no significant differences on the lift coefficients were found between the reduced frequencies F+ equal to 1 and 2. Results of aerodynamic loads showed an improved lift coefficient in relation to the baseline airfoil when pulsed and steady jets are employed. Pulsed jets under square waveform were effective even at high deflected flap condition at 50°, with a significant gain in the lift coefficient of 36%, in relation to the uncontrolled case, combined with a drag reduction of 20%, and a decrease in mass flow up to 49% in relation to the steady jet for the same lift gain. Although sine and square waveform results presented similar improvements for lift, the drag is around 15% higher for the former. When compared with the steady jet case, the mass flow reduction is 36% for the sinewave. Synthetic jets with zero-net-mass-flux proved superior to the baseline conventional multi-element airfoil only with deployed flap at 50°, where a modest lift improvement of 5% was observed.
A novel actuator disk model (ADM) coupled with lifting-line theory is proposed in this paper. Several virtual planform blades are placed on a disk plane with a constant azimuthal interval, and the ...lifting-line theory is applied to each blade to predict the effective angle of attack. The proposed model considers the local lift and drag forces acting on disk surface cells by interpolating the predicted effective angle of attack with various azimuth angles to the actuator disk plane; therefore, the proposed model considers individual blade tip vortices without tip loss functions. Experimental data for hover and forward flight rotors are used to validate the proposed model. For hovering flight, sectional thrust based on collective pitch angles predicted by the modified ADM was similar to that obtained in the experiments. For forward flight, the inflow above the rotor estimated by the proposed ADM was similar to that obtained in the experiments and by using other numerical methods. Thus, the developed ADM can be used for rotor performance analysis under the main flight conditions of V/STOL.
Klassiker är ett komplext fenomen. Dynamiskt och svårfångat. Artikeln undersöker hur en modern möbelklassiker skapas Begreppet kan laddas med värden av både immateriell och materiell karaktär. ...Auraproduktion fyller möbeln med innehåll och stärker den som objekt, vilket gör det till ett operativt och flitigt använt epitet inom både kommersiell och kulturell verksamhet. I artikeln lyfts exempel på praktiker och faktorer, små som stora, som kan bättra på en möbels aura och därmed möjlighet att uppnå status som klassiker.
Experimental studies in the acoustic far field and flow visualization are carried out on circular and non-circular impinging jets at a nozzle to plate distance ratio of 5, for the nozzle pressure ...ratios of 1.8, 4, and 6. Spectra and directivity of the overall sound pressure level of circular jets are compared with those of non-circular jets for the same nozzle pressure ratios, at various emission angles. Non-circular jets mitigate the transonic impinging tones at around the critical pressure ratio, compared to the circular jet. Square jet is quieter at low nozzle pressure ratios by 5–8 dB compared to the circular jet. At higher under expansion conditions, the triangular and square jets almost completely eliminate the supersonic impinging tones. Elliptical jet is noisy at a nozzle pressure ratio of 6, even compared to the circular jet. Elliptical minor axis plane is quieter at lower nozzle pressure ratios compared to the major axis plane and the trend is reversed for the higher nozzle pressure ratios. Schlieren flow visualization studies reveal that the shock cell structures are weakened and symmetry of the shock cells are lost for the non-circular jets compared to the circular jet.
•The (3 + 1)-dimensional Sharma-Tasso-Olver-like (STOL) equation is investigated.•Interaction solutions of the (3 + 1)-dimensional STOL equation are determined.•Lump, periodic lump and double ...kinky-periodic lump wave solutions are emerged.•Hybrid lump waves are emerged by fission and fusion of lump-kink waves.
In this article, we consider a (3 + 1)-dimensional Sharma–Tasso–Olver-like (STOL) model describing dynamical propagation of nonlinear dispersive waves in inhomogeneous media. Applying Hirota's bilinear technique and a trial function, we explore nonlinear dynamical properties of basic solutions to the STOL model. We find that the fission fusion pattern occurs in the collision between the lump and kink waves, the collision between the lump and periodic waves, and the collision among the lump, kink and periodic waves, which is a novel fascinating collision pattern. We also observe that a large value of the coefficient in the periodic function produces a hybrid lump wave by fission in the collision solution. To better understand the dynamic properties of the obtained collision solutions, we plot a number of 3D and contour diagrams by choosing suitable parametric values with the aid of the computational software Maple 18.
Anatomija je živa i translatorna disciplina koja integrira istraživanje i edukaciju. Tijekom stoljeća poznavanje anatomije postajalo je sve važnije za medicinske znanosti, posebno za kirurgiju. Za ...široko i detaljno poznavanje anatomije čovjeka disekcija kadavera nezamjenjiva je metoda jer jedino ona omogućava sigurnu i učinkovitu kliničku praksu. Podučavanje anatomije razvijalo se, kako je vrijeme prolazilo, od naslijeđenih učenja iz prošlosti prema modernoj anatomiji. Znanstveni napredak i promjene u društvu uveli su u nastavu anatomije digitalne alate. Nove metode i digitalne tehnologije daju svoj doprinos obrazovanju budućih liječnika, ali se nikako ne bi trebalo odustati od prakticiranja disekcije kao osnovne metode u podučavanju i učenju anatomije jer je kadaver najbliže pravom pacijentu o kojem će se brinuti budući liječnici. Ovaj rad govori o tome kako se anatomija poučavala na Zavodu za anatomiju Medicinskog fakulteta u Rijeci od osnutka do danas.
Anatomy is a dynamic and translational discipline that integrates research and education. Throughout the centuries, anatomical knowledge has become increasingly important for the medical sciences, especially surgery. Cadaver dissection remains an irreplaceable method for acquiring a comprehensive and detailed understanding of human anatomy, as it is the only method that enables safe and effective clinical practice. The teaching of anatomy has evolved from traditional teachings to modern approaches. Scientific progress and societal changes have introduced digital tools into anatomy education. While new methods and digital technologies enhance the education of future doctors, the practice of dissection should never be abandoned as a foundational teaching and learning method in anatomy. This is because cadavers provide the closest approximation to the real patients that future doctors will treat. This paper discusses the evolution of anatomy teaching at the Department of Anatomy of the Faculty of Medicine in Rijeka from its inception to the present day.
Selection process of the propeller for short take-off and landing (STOL) category aircraft is described. The aim is to achieve the highest possible performance with fixed propeller, i.e., high ...maximal horizontal and cruise speed, short take-off and high rate of climb. These requirements are contradictory and so Pareto sets were used in order to find the optimal propeller. The method is applied to a family of geometrically similar propellers that are suitable for 73.5 kW (100 hp) piston engine designed for ultralight category aircraft with maximal take-off weight of 472.5 kg. The propellers have from two to eight blades, blade angle settings from 15° to 40° and diameter from 1.1 m to 2.65 m. Pareto frontier is designed for each pair of flight conditions, and the optimal propeller is selected according to these results. For comparison, the optimal propeller selection from the propeller family by means of a standard single-optimal process based on the speed power coefficient cs is also used. Use of Pareto sets leads to considerable performance increase for the set of contradictory requirements. Therefore, high performance for a low price for the given aircraft can be achieved. The described method can be used for propeller optimization in similar cases.
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