Abstract: Experimental measurements were conducted on a plunging Eppler 361 strip flapped airfoil to study wake structure in the wake. The heights of strip flap were 2.6% and 3.3% chord. The velocity in the wake was measured by hot-wire anemometry. It was found that the trailing-edge strip had different effects on the plunging wake profile during the oscillation cycle. At initial angle of 0 degree, the trailing-edge strip causes more velocity defect in the oscillation phases of 180º and 270º. At high initial angle 12 degrees, a significant decrease in value of velocity is found at 180º because of the leading edge vortex shedding. The power spectra of dominant frequencies were significantly increased by fitting the strip flap on the plunging airfoil.
Abstract: Compressor is a crucial component of an engine. Flow through the compressor is intricate and sensitive to the reference frame, geometry of the blade, tip clearance, stator, staging etc. Compressor, though designed for a particular environment, is also expected to show its performance under off design conditions like accelerating flight, landing, take off, climbing etc. The flow in third dimension leads to many complications and ambiguity. Tip aerodynamics, passage flow, and vortex aerodynamics play crucial role in describing the flow through the upper half of the blade and in the tip region, whereas flow over blade surface, trailing edge and the hub will guide the aerodynamic behavior of the rotor blade. This exercise is done for off design environment to study the aforesaid flow characteristics and is carried on an axial flow fan. The performance variation of fan flow under varying flow conditions is analyzed.
Abstract: A study on the effect of allocating a square blockage in front of a rotating cylinder is presented. The aim of the study is to determine the optimum design of the blockage to enhance the lift generating performance of the rotating cylinder. A numerical simulation is carried out to investigate the effect of different sizes of blockage towards the lift generating performance of the rotating cylinder. The simulation adopted a fully turbulent flow, having Reynolds number of 600. The cylinder is spinning at 5000 RPM. The validation of the simulation RANS code FLUENT is done through comparison with the published results from past studies. In general, the results suggest that the lift generating performance of the rotating cylinder will be improved by placing a blockage in front of it.
Abstract: The present work is focused on the unsteady aerodynamics of bio-inspired flapping wing to produce lift and thrust for hovering and forward flight. A generic approach is followed to understand and mimic the mechanism and kinematics of ornithopter by considering the motion of a three-dimensional rigid thin wing in flapping and pitching motion, using strip theory and two-dimensional unsteady aerodynamics for idealized wing in pitching and flapping oscillations with phase lag. Parametric study is carried out to obtain the lift, drag, and thrust characteristics within a cycle for assessing the plausibility of the aerodynamic model, and for the synthesis of a Flapping Wing MAV model with simplified mechanism. Other important parameters such as flapping frequency and wing geometry are considered. Results are assessed in comparison with the existing theoretical results.
Abstract: The past research by the author on the conventional brake disk design i.e. straight blade bi-directional design, a misalignment of flow was identified. The misalignment was quantified using CFD as design tool. In the effort of re-aligning the flow angle helical lines fitted onto the conventional inner and outer diameter disk brakes yielded two different design innovation. The two “curved” designs have highlighted tremendous improvement on flow characteristics. Experimental analysis is carried out on the two curved 1 and curved 2 prototypes. The quantitative mass flow rate result is compared for conventional and the two curve shaped brake disk. Then, the data is fed as input condition to Computational Fluid Dynamics (CFD) model for disk brake models to analysis the flow characteristics qualitatively. The aerodynamics visualization through CFD supports well the mass flow improvement. The non-dimensional flow number is established and the correlation between flow number and Reynolds number is highlighted.
Abstract: Liquid atomization is a process of changing the liquid into small droplets. There are many applications which are related to liquid atomization including fuel injection in combustion systems and also in agricultural sprays. In pressure swirl atomizer, the liquid is injected into the atomizer through tangential port and a swirling motion is formed inside the swirl chamber. In high strength of swirling motion, an air core will be visible inside the atomizer. The liquid is then discharged from the orifice to form a spray which breaks up the liquid into small droplets. The objective of this research is to investigate the effect of various orifice geometries on the air core diameter. The injection pressure was varied in the range of 2 to 8 bar and water was used as the working fluid. Experiment data shows that the air core diameter increases as the injection pressure increased, regardless the discharge orifice diameter and discharge orifice length. It also found that the air core diameter increases as the discharge orifice length decreases and the discharge orifice diameter increases.
Abstract: This paper presents a study on the effect of canard setting angle on the aerodynamic characteristic of a Blended Wing Body (BWB). Canard effects to BWB aerodynamic characteristics are not widely investigated. Hence the focus of the study is to investigate the variations of lifts, drags and moments when the angles of attack are varied at different canard setting angles. Wind tunnel tests were performed on BWB aircraft with canard setting angles, ranging from -20˚ to 20˚. Angles of attack, were varied from -10˚ to 10˚. Aspect ratio and canard planform area were kept fixed. All tests were conducted in the subsonic wind tunnel at Universiti Teknologi MARA, at Mach number of 0.1. The streamlines flow, at the upper surface of the canard was visualized using mini tuft. Result shows that the lift coefficient does not change much with different canard setting angles. As expected, the lift coefficient increases with increasing angles of attack at any canard setting angle. In general, the moment coefficient increases as the canard setting angle is increased. The results obtained in this research will be of importance to the understanding of aerodynamic behavior of BWB employing canard in its configuration.
Abstract: During helicopter forward flight, the retreating blade revolves at high angle of attack compared to advancing blade in order to balance the lift and also to stabilise the helicopter. However, due to the aerodynamics limitations of the retreating blade at forward flight, stall may occur at high angle of attack compared with the advancing blade. This phenomenon is dangerous for pilot when controlling and balancing the helicopter while flying against strong wind. This paper investigates the capabilities of introducing multiple vortex traps on the upper surface of the helicopter airfoil in order to delay the stall angle of retreating helicopter blade. Blade Element Theory (BET) was applied to scrutinize the lift force along the helicopter blade. Computational Fluid Dynamic (CFD) analyses using the Shear-Stress Transport (SST) turbulence model was carried out to investigate the effect of groove on delaying the stall and to predict the separation of flow over the airfoil. Based on the CFD analyses, the optimization of the groove was done by analyzing the numbers and locations of the grooves. Finally, the results from both BET and the CFD analyses were utilised to obtain the lift force achieved by the vortex trap. The study showed that the presence of multiple vortex traps has successfully increased the lift coefficient and most importantly, delaying the stall angle.
Abstract: This paper presents the investigation on the effects of the blowing ratio of multiple shallow angle film cooling holes. Multiple film cooling holes having a shallow hole angle (θ = 20°), arranged to perform in-line hole configuration has been considered in the present study. The investigation focuses on the effects of high blowing ratio of the film cooling effectiveness which have been carried out at ReD = 3100 and BR = 2.0, 3.0 and 4.0. The experiments make use of the IR camera in capturing the surface temperature to determine the film cooling effectiveness. The contours of the film cooling effectiveness distribution together with plots on laterally average film cooling effectiveness along the x/D are presented. The discussions have been made with a support of the temperature field captured at x/D = 3, 13, 23, and 33. The results clearly show the benefit of the employment of shallow hole angle (θ = 20°) at high blowing ratio which is much more superior in comparison to the common hole configuration (θ = 35°).