48 research outputs found
Effects of reynolds number on flow separation above generic half span transport aircraft model
No full textThe purpose of this study is to investigate the flow separation on UTM half model at 3 different Reynolds number which is 0.5 x 106, 1.0 x 106 and 1.5 x 106 which corresponds to speed, V = 20 m/s, 45 m/s and 65 m/s using pressure distribution method and flow visualization. The study was done to observe the flow separation for three different Reynolds number. The pressure distribution at 50% wing span was measured and plotted to observe the flow characteristic at angle of attack from 0 deg to 24 deg at three different Reynolds number. The pressure distribution on the wing was reduced to local lift coefficient and this data was compared to lift coefficient obtained from the balance data to study when the model reaches stall
An automated visual tracking measurement for quantifying wing and body motion of free-flying houseflies
No full textPioneering discoveries revealed that flying insects actively regulate body appendages such as wings, legs and abdomen to stay aloft. However, the initial stage of capturing their motion during flight is rather challenging and time-consuming, especially during the digitization of lengthy video images. Therefore, our development of an automated visual tracking system will greatly provide a full access to insect's body and wing dynamics during flight. By using the positional dataset obtained from the digitized images which earlier captured by an automated time-resolved high-speed videography, we thus further three-dimensionally reconstructed body and wing dynamics of housefly Musca domestica. We validated and further compared the automated digitization with manual tracking. Our analysis estimates that motions along z-axis yields higher differences (16 ± 28.19 µm for thorax and 13 ± 99.19 µm for wingtip) because it orthogonally points to the cameras, which lead to acceptable inaccuracies of calibration coefficients due to the limited depth of focus
The analysis of flow on round-edged delta wings
No full textThe flow around three-dimensional aircraft wings, including delta-wings is very complicated. Much experimental and numerical work has been performed to discover its complexity. To date, all numerical calculations on delta wings have been carried out for either fully laminar or fully turbulent boundary layers. The transition status of the boundary layer is considered unknown despite several efforts to identify transition from laminar to turbulent flow. One such study, called the International Vortex Flow Experiment – 2 (VFE-2), has been carried out by an international group and mainly focuses on the boundary layers on delta wings. The data from the VFE-2 experimentals potentially provide the location of transition on the upper and lower surfaces of the wing to guide associated numerical studies. The effects of Reynolds number, Mach number, angle of attack and the leading edge bluntness are also investigated.
Almost all delta wing studies to date have involved tests on wings with sharp leading edges and these have led to the conclusion that the flows are relatively independent of Reynolds number. In fact, most real wings have finite leading edge radii. Hence, the flow separation is no longer fixed at the leading edge, thus making the flow dependent on Reynolds number. This particular aspect has been studied extensively by the VFE-2 team.
As part of the VFE-2 project, Glasgow University constructed a delta wing with four different sets of leading edges. Small-, medium- and large-radius edges and a pair of sharp leading edges were constructed in order to compare results from four delta wing configurations. In the current study experiments were carried out on these wings in the 2.65 metre by 2.04 metre, closed circuit, Argyll Wind tunnel of Glasgow University. The models were mounted on a specially designed sting support structure that allowed them to be pitched around a constant centre of rotation throughout the experiments. Tests were conducted at speeds of 20.63 m/s and 41.23 m/s representing Reynolds numbers of 1 x 106 & 2 x 106 respectively, based on the mean aerodynamic chords of the wings. The tests were conducted in three phases. In the first phase, steady and unsteady forces and moments on all wings were measured at an angle of attack that varied from α =100 to 250. The forces and moments were captured at two sampling rates; i.e., 100 Hz and 8000 Hz. The second test series captured flow visualization data on the four wings. In these experiments, a mixture of Ondina oil and paraffin was combined with Dayglo powder and applied to the surfaces of the delta wings. The images of the flow topology on the wings were recorded. The final series of experiments involved Particle Image Velocimetry measurements. A stereo-PIV arrangement was applied in this experiment and two CCD-Cameras were positioned outside the test section for image capture.
The current study has identified interesting features of the interrelationship between the conventional leading edge primary vortex and the occurrence and development of the inner vortex on the round-edged delta wings. The inner vortex was first identified and verified by the VFE-2 team. The effects of Reynolds number, angle of attack and leading-edge radii on both vortices are discussed in detail. The steady balance data have shown that the normal force coefficients are sensitive to leading edge bluntness at moderate angles of attack but are less so at high angles of attack. In relation to this, the flow visualization images have also shown that the primary vortex origin is located further aft on the wing at higher leading edge bluntness. This impacts on the strength of the inner vortex which remains a significant flow feature until the primary vortex approaches the apex. The lateral extent of the inner vortex is very dependent on the primary vortex at the leading edge; i.e. the weakening of the primary vortex has positive effects on the inner vortex. Particle Image Velocimetry shows that the increase in leading edge bluntness significantly decreases the swirl magnitude of the primary vortex.
The results obtained from the current investigation provide considerable insight into the effects of Reynolds number, angle of attack and bluntness on the flow structures experienced by delta wings, with rounded leading edges. This work will, therefore, inform and guide future investigations of delta wing flows and has the potential to impact on future wing design
Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interference
No full textThe main objective of the present work is to study the effect of an external store to a subsonic fighter aircraft. Generally most modern fighter aircraft is designed with an external store installation. In this project a subsonic fighter aircraft model has been manufactured using a computer numerical control machine for the purpose of studying the effect of the external store aerodynamic interference on the flow around the aircraft wing. A computational fluid dynamic (CFD) and wind tunnel testing experiments have been carried out to ensure the aerodynamic characteristic of the model then certified the aircraft will not facing any difficulties in stability and controllability. In the CFD experiment, commercial CFD code is used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with test section sized 0.45 m×0.45 m. Result in the two-dimensional pressure distribution obtained by both experiments are comparable. There is only 12% deviation in pressure distribution found in wind tunnel testing compared to the result predicted by the CFD. The result shows that the effect of the external storage is only significant at the lower surface of the wing and almost negligible at the upper surface of the wing. Aerodynamic interference is due to the external storage were mostly evidence on a lower surface of the wing and almost negligible on the upper surface at low angle of attack. In addition, the area of influence on the wing surface by store interference increased as the airspeed increase
Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interference of subsonic Fighter Aircraf
No full textThe main objective of the present work is to study the effect of an external store to a subsonic fighter aircraft. Generally most modern fighter
aircraft is designed with an external store installation. In this project a subsonic fighter aircraft model has been manufactured using
a computer numerical control machine for the purpose of studying the effect of the external store aerodynamic interference on the flow
around the aircraft wing. A computational fluid dynamic (CFD) and wind tunnel testing experiments have been carried out to ensure the
aerodynamic characteristic of the model then certified the aircraft will not facing any difficulties in stability and controllability. In the CFD
experiment, commercial CFD code is used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model
together with an external store was tested in a low speed wind tunnel with test section sized 0.45 m×0.45 m. Result in the two-dimensional
pressure distribution obtained by both experiments are comparable. There is only 12% deviation in pressure distribution found in wind
tunnel testing compared to the result predicted by the CFD. The result shows that the effect of the external storage is only significant at the
lower surface of the wing and almost negligible at the upper surface of the wing. Aerodynamic interference is due to the external storage were
mostly evidence on a lower surface of the wing and almost negligible on the upper surface at low angle of attack. In addition, the area of
influence on the wing surface by store interference increased as the airspeed increase
Effect of control surface and reynolds number on flow separation of generic light aircraft
No full textThe objective of this project is to investigate the nature of flow separation on a generic SME MD3 160 light aircraft model. The experiment was conducted in UTM low speed tunnel to investigate the flow separation behavior of a 15% scaled down two-seater light aircraft model, Malaysian made SME MD3-160 aircraft. The model has overall length of 1.3m and wingspan of 1.5m. It is designed for external balance and surface pressure measurement studies. The experimental works were conducted at three speeds of 30m/s, 35m/s, 40m/s corresponding to Reynolds numbers which are 0.414, 0.515, 0.519 million with angle of attack ranging from -6°to 23°. Flaps were deflected at 5° 10° 20° during testing. Steady balance and surface pressure data were recorded simultaneously. It showed that flaps promoting stall at 12° and at angle of attack 14° pressure recovery was hindered resulting to a dramatic change of pressure on the surface
Experimental investigation of delta wing flow behaviour under pitching motion
No full textThis paper presents an experimental study of delta wing flow behaviour under pitching motion. The aim is to investigate the pressure distribution of the flow over sharp-edged delta wing. The flow behaviour over the upper surface of a delta wing is mainly governed by the leading edge vortices. Angle of attack variation is applied to simulate the pitching motion of the delta wing. The project focuses on estimating the pressure distribution for a sharp-edged delta wing with 65° sweep angle. Wind tunnel testing is done at two flow velocities, which are 13.5 m/s and 15 m/s. The trend of pressure coefficient (cp) against the spanwise location is then analysed based on four aspects, which are the variations of Reynolds number, chordwise location, spanwise location and angle of attack. The results show that the pressure at the vicinity of leading edge is much lower than the pressure plotted near to the wing centre
Computational fluid dynamic on double delta wing
No full textBasic concept of aircraft wing design is based on airfoil section. Time flies, evolution in aircraft wing design shows the desire of mankind to improve the speed, agility, maneuverability of an aircraft. It is proven that aircraft with delta or double delta wing design fulfill this desire. Basic concept of delta wing is triangular planform of the wing that same with the Greek symbol (Δ) and double delta wing is delta wing with a ‘kink’ or leading edge extension. This research aims is to obtain aerodynamic characteristic (Cl, Cd) of double delta wing using computational fluid dynamic and compare the result with wind tunnel experiment. In this work, the geometry of the double delta wing used was constructed using 2 x 106unstructed mesh elements. Turbulence model that been used in this research is k-ω turbulence model. The simulation was run at Reynolds Number of 1 x 106 and 2 x 106 and with variation of pitch angle from 0° to 20°
Metodologi Al-Albani Dalam Alat At -Nab!
No full textKepentingan solat dan kewajipan melakukannya suatu yang diketahui
umum. Namun bentuk perlakuan solat yang bertepatan dengan
amalan Rasulullah s.a.w suatu yang perlu diberi perhatian. Adalah
suatu yang penting untuk memperhalusi kitab yang membincangkan
tentang solat Nabi s.a.w berasaskan hadith yang sahih. Maka kajian
ini yang bertajuk Metodologi al-Albinl Dalam alit al-Nabl,
tertumpu pada metodologi yang. digunakan oleh pengarangnya dalam
menyusun kitab tersebut.
The importance of prayer and the compulsory duty to do it is one
well-known. However, treatment fonn prayer which was exactly with
the Prophet Muhammad (Peace Be Upon Him) practice is one which
matter should give attention. It is become something important to
scrutinize book which discussed of Prophet (PB UH) prayer based on
authoritative hadith. Then, this study entitled The Methodology of
al-Albiinl in alit al-Nabl focussed on methodology used by the
author to arrange that book
Verification of heat transfer enhancement in tube with spiral corrugation
No full textDemand of high performance heat exchanger in industrial application is increasing since the depletion of energy resources such as in food processing plant, air-conditioning system and power plant. One of the ways of saving energy is by enhancing heat transfer performance, which in return will give a high performance heat exchanger. Existing enhancing techniques can be classified into three different categories which are active method, passive method and compound method. Spirally corrugated tube is one of the passive heat transfer enhancement method which involve surface extensions. The type of surface extension used in heat transfer performance will contribute to heat transfer coefficient and pressure drop, and directly affected the heat transfer performance. Traditionally, experimental studies were carried out to get the desired results but with the help of technology, numerical simulation is one of the promising alternatives in predicting reliable results for real application. For reliable numerical results, experimental studies are still necessary for the validation process and the verification process which comes before it is also mandatory. Thus, this paper focus on verification the numerical simulation of flow in a double-pipe heat exchanger with spirally corrugated internal tube. It was done for laminar flow with Reynolds number of 1000. Numerical simulation model using commercial CFD software were run with different mesh sizes to determine the grid independent solution and to choose which mesh is suitable to use for the whole simulation process. Minimizing and choosing the right mesh were done through Grid Convergence Index (GCI). Solutions of three different grids with their residuals convergence are also presented to fulfil the verification steps. The level of grid independence is evaluated using a form of Richardson extrapolation and the study shows that the finest grid solution has a GCI of less than 5%
