Aerodynamic Investigation of Morphing Wing UAV with Adjustable Slotted Airfoil Configuration

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
R. Jiniraj ◽  
R. Venkat Raman ◽  
N. Dinesh
Keyword(s):  
Flow Velocity ◽  
High Speed ◽  
Flow Simulation ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Low Flow ◽  
Sudden Increase ◽  
Sudden Decrease ◽  
Drag Factor ◽  
Aerodynamic Investigation

Aviation has wide aspects to challenge and discover, the ability to land and take off at slow speed, sudden increase in drag for short runway landings. This paper puts forth the solution by the use of adjustable multi slots configuration of an airfoil. In this case, the slots extend from the wing leading edge to trailing edge. This causes change in the chord, thereby changing the camber of unsymmetrical airfoil. An investigation was made to determine and compare the aerodynamic characteristics of multi slotted adjustable airfoil with unmorphed unsymmetrical airfoil at varied speeds and Angle of Attack (AoA). There are three slots distanced equally along the airfoil. The extension of these slots increases the chord length by 10% of total chord. The slotted and unslotted airfoil profile are then studied using computational fluid dynamics of external flow over a body. The flow simulation is done at 10m/s, 20m/s, 30m/s, 40m/s and 50 m/s flow velocity and at 0, 3, 6, 9 ,12, 15 AoA. The results were obtained for each case and the values for base and slotted model were compared. It was found that lift of slotted model is slightly higher than base model at low flow velocity. It was also seen that the use of slots at high speed causes a large amount of drag. This increased drag factor can be used in UAV’s as spoilers during landing or for landing at shorter runways at lower speed, allowing a sudden decrease in aircraft speed and also to glide at a steeper angle over obstruction.

scholarly journals Controlled-Endwall-Flow Blading for Multistage Axial Compressor Rotor

1997 ◽  
Author(s):  
M. Inoue ◽  
M. Kuroumaru ◽  
M. Furukawa ◽  
Y. Kinoue ◽  
T. Tanino ◽  
...  
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
Axial Compressor ◽  
Internal Flow ◽  
Leading Edge ◽  
Rotor Blades ◽  
Advanced Technology ◽  
Low Flow ◽  
Surge Margin ◽  
Highly Loaded

This research aims to develop an advanced technology of highly loaded axial compressor stages with high efficiency and sufficient surge margin. To improve endwall boundary layer flows which lead to energy loss and instability at an operation of low flow rate, the Controlled-Endwall-Flow (CEF) rotor blades were designed and tested in the low speed rotating cascade facility of Kyushu University. The CEF rotor blades have three distinctive features: the leading-edge sweep near hub and casing wall, the leading-edge bend near the casing, and the same exit metal angle of blade evaluated by a conventional design method. Mechanical strength of the blade was verified by a numerical simulation at a high speed condition. The baseline rotor blades were designed under the same design condition and tested to compare with the CEF rotor. The results showed that the maximum stage efficiency of the CEF rotor was higher by 0.7 percent and the increase in surge margin was more than 20 percent in comparison with the baseline rotor. The results of both internal flow survey and 3D Navier-Stokes analysis showed that improvement of the overall stage performance resulted from activation of the endwall boundary layers, and suggested that further improvement might be expected by combination of end-bend stator blades and a highly loaded axial compressor stage could be developed by use of the CEF rotor.

Suppression of Cavitation in Inducers by J-Grooves

2006 ◽  
Vol 129 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Young-Do Choi ◽  
Junichi Kurokawa ◽  
Hiroshi Imamura
Keyword(s):  
High Speed ◽  
Leading Edge ◽  
Design Flow ◽  
Low Flow ◽  
Axial Pressure ◽  
Flow Rates ◽  
New Device ◽  
Axial Pressure Gradient ◽  
Blade Tip ◽  
Suction Performance

Cavitation is a serious problem in the development of high-speed turbopumps, and an inducer is often used to avoid cavitation in the main impeller. Thus, the inducer often operates under the worst conditions of cavitation. If it could be possible to control and suppress cavitation in the inducer by some new device, it would also be possible to suppress cavitation occurring in all types of pumps. The purpose of our present study is to develop a new, effective method of controlling and suppressing cavitation in an inducer using shallow grooves, called “J-Grooves.” J-Grooves are installed on the casing wall near the blade tip to use the high axial pressure gradient that exists between the region just downstream of the inducer leading edge and the region immediately upstream of the inducer. The results show that the proper combination of backward-swept inducer with J-Grooves improves the suction performance of the turbopump remarkably, at both partial flow rates and the design flow rate. The rotating backflow cavitation occurring at low flow rates and the cavitation surge which occurs near the best efficiency point can be almost fully suppressed by installing J-Grooves.

Identification of a degradation of aerodynamic characteristics of a paraglider due to its flexibility from flight test

2019 ◽  
Vol 91 (6) ◽  
pp. 873-879 ◽  
Author(s):  
Robert Kulhánek
Keyword(s):  
High Speed ◽  
Aerodynamic Drag ◽  
Leading Edge ◽  
Flight Test ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Content Type ◽  
Specific Geometry ◽  
Lift And Drag ◽  
Scaled Models

Purpose Aerodynamics of paragliders is very complicated aeroelastic phenomena. The purpose of this work is to quantify the amount of aerodynamic drag related to the flexible nature of a paraglider wing. Design/methodology/approach The laboratory testing on scaled models can be very difficult because of problems in the elastic similitude of such a structure. Testing of full-scale models in a large facility with a large full-scale test section is very expensive. The degradation of aerodynamic characteristics is evaluated from flight tests of the paraglider speed polar. All aspects of the identification such as pilot and suspension lines drag and aerodynamics of spanwise chambered wings are discussed. The drag of a pilot in a harness was estimated by means of wind tunnel testing, computational fluid dynamics (CFD) solver was used to estimating smooth wing lift and drag characteristics. Findings The drag related to the flexible nature of the modern paraglider wing is within the range of 4-30 per cent of the total aerodynamic drag depending on the flight speed. From the results, it is evident that considering only the cell opening effect is sufficient at a low-speed flight. The stagnation point moves forwards towards the nose during the high speed flight. This causes more pronounced deformation of the leading edge and thus increased drag. Practical implications This paper deals with a detailed analysis of specific paraglider wing. Although the results are limited to the specific geometry, the findings help in the better understanding of the paraglider aerodynamics generally. Originality/value The data obtained in this paper are not affected by any scaling problems. There are only few experimental results in the field of paragliders on scaled models. Those results were made on simplified models at very low Reynolds number. The aerodynamic drag characteristics of the pilot in the harness with variable angles of incidence and Reynolds numbers have not yet been published.

Aerodynamic Characteristics Analysis of Ultra-High-Speed Elevator with Different Hoistway Structures

2021 ◽  
Author(s):  
Hao Jing ◽  
Qing Zhang ◽  
Ruijun Zhang ◽  
Qin He
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Sudden Increase ◽  
Aerodynamic Forces ◽  
Cross Sectional ◽  
Ultra High Speed ◽  
Characteristics Analysis ◽  
Ventilation Hole

The high-speed airflow generated by ultra-high-speed elevators causes significant aerodynamic force, which seriously reduces the comfort and safety of passengers. First, a multi-parameter general model of ultra-high-speed elevator was established, and the three-dimensional numerical simulation of incompressible flow in the ultra-high-speed elevator was simulated. The correctness of the model and method was verified by experiments and grid-independence analyses. On this basis, the variation in the aerodynamic forces and the pressure in the hoistway was analyzed. Finally, the influence of different hoistway structures and parameters of ventilation holes on the aerodynamic forces and hoistway pressure were analyzed. The results showed that the opening of ventilation holes significantly reduced the aerodynamic forces and hoistway pressure for most of the period of the car’s operation period, but both the aerodynamic forces and hoistway pressure showed a sudden increase–decrease process. The aerodynamic forces and hoistway pressure were highly sensitive to changes in the hoistway blockage ratio, the cross-sectional area of the ventilation hole, and the position of the ventilation hole. When a pair of ventilation holes were opened, those in the middle of the hoistway reduced aerodynamic problems in the hoistway to the greatest extent. The increase in the connection angle between the ventilation hole and the hoistway eliminated the low-speed recirculation zone at the ventilation hole and increased the total volume of exhaust air at the ventilation hole.

Effects of Alternate Leading Edge Cutback on Unsteady Cavitation in 4-Bladed Inducers

2001 ◽  
Vol 123 (4) ◽  
pp. 762-770 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto ◽  
Dai Kataoka ◽  
Hironori Horiguchi ◽  
Fabien Wahl
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Leading Edge ◽  
Cavitation Number ◽  
The Other ◽  
Low Flow ◽  
Pressure Measurements ◽  
High Speed Video ◽  
Cavitation Performance ◽  
Wide Range

A set of 4-bladed inducers with various amounts of cutback was tested with the aim of suppressing the rotating cavitation by applying alternate leading edge cutback. Unsteady cavitation patterns were observed by means of inlet pressure measurements and high-speed video pictures. It was found that the region with the alternate blade cavitation and asymmetric cavitation were enlarged with the increase of the amount of the cutback. As a result, the region with the rotating cavitation was diminished. At low flow rate, two types of alternate blade cavitation were found as predicted theoretically on 4-bladed inducer with smaller uneven blade length. One of them is with longer cavities on longer blades, and the other is with longer cavities on shorter blades. Switch was observed in these alternate blade cavitation patterns depending whether the cavitation number was increased or decreased. For an inducer with larger amount of cutback, the rotating cavitation and cavitation surge were almost suppressed as expected for a wide range of flow rate and cavitation number, although the cavitation performance was deteriorated. However, we should note that an asymmetric cavitation pattern occurs more easily in inducers with alternate leading edge cutback, and that the unevenness due to the cutback causes uneven blade stress.

scholarly journals Near-occlusion is difficult to diagnose with common carotid ultrasound methods

2021 ◽  
Vol 63 (5) ◽  
pp. 721-730
Author(s):  
Elias Johansson ◽  
Davide Vanoli ◽  
Isa Bråten-Johansson ◽  
Lucy Law ◽  
Richard I Aviv ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Sensitivity And Specificity ◽  
Low Flow ◽  
Reference Standard ◽  
Carotid Ultrasound ◽  
Ultrasound Method ◽  
Velocity Parameter ◽  
Near Occlusion

Abstract Purpose To assess the sensitivity and specificity of common carotid ultrasound method for carotid near-occlusion diagnosis. Methods Five hundred forty-eight patients examined with both ultrasound and CTA within 30 days of each other were analyzed. CTA graded by near-occlusion experts was used as reference standard. Low flow velocity, unusual findings, and commonly used flow velocity parameters were analyzed. Results One hundred three near-occlusions, 272 conventional ≥50% stenosis, 162 <50% stenosis, and 11 occlusions were included. Carotid ultrasound was 22% (95%CI 14–30%; 23/103) sensitive and 99% (95%CI 99–100%; 442/445) specific for near-occlusion diagnosis. Near-occlusions overlooked on ultrasound were found misdiagnosed as occlusions (n = 13, 13%), conventional ≥50% stenosis (n = 65, 63%) and < 50% stenosis (n = 2, 2%). No velocity parameter or combination of parameters could identify the 65 near-occlusions mistaken for conventional ≥50% stenoses with >75% sensitivity and specificity. Conclusion Near-occlusion is difficult to diagnose with commonly used carotid ultrasound methods. Improved carotid ultrasound methods are needed if ultrasound is to retain its position as sole preoperative modality.

scholarly journals Research on aerodynamic characteristics of two-stage axial micro air turbine spindle for small parts machining

2020 ◽  
Vol 12 (12) ◽  
pp. 168781402098437
Author(s):  
Liu Jiang ◽  
Guo Zhiping ◽  
Miao Shujing ◽  
He Xiangxin ◽  
Zhu Xinyu
Keyword(s):  
High Speed ◽  
Aerodynamic Characteristics ◽  
Maximum Efficiency ◽  
Two Stage ◽  
Output Torque ◽  
Air Turbine ◽  
Solid Foundation ◽  
Computational Fluid Dynamics Cfd ◽  
Micro Machine ◽  
Small Parts

In order to meet the requirements of output torque, efficiency and compact shape of micro-spindles for small parts machining, a two-stage axial micro air turbine spindle with an axial inlet and outlet is proposed. Based on the k-ω turbulence model of SST, the flow field and operation characteristics of the two-stage axial micro air turbine spindle were studied using computational fluid dynamics (CFD) combined with an experimental study. We obtained the air turbine spindle under different working conditions of the loss and torque characteristics. When the inlet pressure was 300 KPa, the output speed of the two-stage turbine was 100,000 rpm, 9% higher than that of a single-stage turbine output torque. The total torque reached 6.39 N·mm, and the maximum efficiency of the turbine and the spindle were 42.2% and 32.3%, respectively. Through the research on the innovative structure of the two-stage axial micro air turbine spindle, the overall performance of the principle prototype has been significantly improved and the problems of insufficient output torque and low working efficiency in high-speed micro-machining can be solved practically, which laid a solid foundation for improving the machining efficiency of small parts and reducing the size of micro machine tool.

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