1,721,085 research outputs found
Particle-ladened flow in pipes and channels
No full textThis project is a research-based project between Nanyang Technological University and Jurong Port Private Limited. The first aim of this project is to experimentally investigate the air and cement flow encountered in an air-slide conveyor and pneumatic conveyor. Said conveyors are presently used at Jurong Port Terminal. The second aim is to, based on the results of the investigations, explore potential engineering modifications that can increase cement delivery rate or reduce instances of choking e.g. varying the mass flow rate (cement) by adjusting the speed of the blower. These modifications are targeted to increase the operational efficiency of cement rig.
Based on the single-phase PIV measurements, the author was able to determine flow conditions at three different locations of the rig – the three locations allowed a better understanding of how the flow changed along the rig.
The data from the two-phase PIV experiments allowed the author to distinguish the flow of cement particles from airflow. The results concluded that the cement particles were able to track the airflow well and future experiments can be conducted in single-phase. This is important as it eliminates complications involved in two-phase PIV experiments where the seeding particles (Rhodamine dye) were absorbed by the cement. Also, as the mass flow rate increases, the cement particles will increasingly block light from the atomized dye, which may result in errors in results.Bachelor of Engineering (Aerospace Engineering
Leapfrogging of vortex rings
No full textThis report documents and discusses the findings of an experimental study conducted to shed light on the leapfrogging process of elliptic vortex rings, together with the associated interactions and flow structures. Planar laser induced fluorescence and time-resolved particle image velocimetry were employed to obtain both qualitative visualisations as well as quantitative flow measurements. Four cases of varying Reynolds number (Re=2000 and 4000) and time interval between the generation of the two rings (ΔT=0.05s and 0.2s) were investigated in two orthogonal planes along the major and minor axes of the elliptic orifice, and the results suggested that leapfrogging was more difficult to achieve for elliptic rings, as compared to circular ones, due to the additional inherent axis switching behaviour. A single passage was observed in both planes for Re=2000, ΔT=0.2s and Re=4000, ΔT=0.05s, although the passing ring dissipated soon after. Interestingly, for the case of Re=2000, ΔT=0.05s, the trailing vortices passed through successfully in one plane, but merged with the leading vortices in the other plane, demonstrating that the interaction was highly three-dimensional. It was also determined from the results for the case of Re=4000, ΔT=0.2s that the trailing ring unexpectedly bifurcated into two sub-rings under the combined influence of the self-induced velocity and the induced velocity from the leading ring. In a similar sense, partial bifurcation of the trailing ring could also explain the transient appearance of a counter-rotating vortex pair in two particular cases as well.Bachelor of Engineering (Aerospace Engineering
Flow simulations on modified aero-propellers
No full textIn this project, steady airflow is simulated around a propeller using the CFD software Fluent from ANSYS Student. The propellers for the simulations were a model propeller and a modified propeller with sawtooth serrations at its trailing edge. The fluid domain was built around the propeller and meshed with different settings while maintaining the number of cells in the mesh did not exceed the given limit from ANSYS Student. Flow simulations were then run on Fluent for different flow velocities using a medium mesh, a fine mesh, and a medium mesh with body and face element sizing, for both original model propeller and modified propeller. The results such as the thrust and power coefficients, velocity and pressure distribution, and acoustic power level were compared between the propellers and the meshes.
Different meshes gave similar results for the thrust coefficient, power coefficient, velocity distribution of the airflow and pressure distribution on both model and modified propellers. The coefficients of thrust and power of the model propeller, calculated from the results of the flow simulations, were respectively around 0.04 and 0.02 lower than experimental results using the same type of propeller for a range of flow velocities, while modified propeller has thrust and power coefficients reduced by about 18% and 12 % respectively when working at low velocities. On the other hand, the reduction in acoustic power level could not be estimated surely as different mesh showed different degree of noise reduction.Bachelor of Engineering (Aerospace Engineering
An experimental investigation into the flow behaviour of submersibles.
No full textSubmarines are relatively complicated machinery that are required to operate in a range of environments and operations. To achieve efficient operations, as well as to maintain a strategic advantage, it is important to focus on the flow around the submarine, especially on the areas where the flow separates from laminar to turbulent regions.
This investigation will focus on establishing a set-up that is able to accommodate the following requirements: the ability to vary the pitch and yaw angles while maintaining a stable model, a method that does not interfere with the flow around the model and allow the dye tubes to be able to be adjusted laterally and vertically. Furthermore, this investigation also aims to use water tunnel experiments to establish the interactions of the flow with the submarine at various combinations of pitch and yaw.
The author concluded that the set-up was able to meet the three requirements. However, a key issue faced was that the dye flow was not consistently stable. Future research and work are needed to ensure this problem is resolved. The author recommends using the same set-up with particle image velocimetry (PIV) instead of dye flow.Bachelor of Engineering (Aerospace Engineering
Simulations of drone aerodynamics in an indoor environment
No full textAdvancements in Technology in the recent years has brought about convenience for the people and is in some cases has saved lives. Some examples will be the usage of robots to aid bomb disposal units, Unmanned Aerial Vehicle (UAV) in the military as surveillance and reconnaissance and even usage of drones to snap aerial videos and photos. This has in turn give rise to the increase in usage of drones within the general population. Furthermore,
drones are small enough to navigate through tight spaces and corners which are unreachable by man and even able respond to emergencies faster than any man. Hence, with studies conducted to allow a single operator to control a swamp of drones, this study aims to incorporate this technology as an emergency system to aid data centers in times of power failure through investigating the effects of drone aerodynamics using computational fluid dynamics (CFD). Using the open source OpenFOAM 4.1 and RANS turbulence modelling method, an operating scenario of the drone aerodynamic in the data centre was simulated. A simplified computational domain was created to represent the geometries of the drone downwash in a walkway, 1m by 1m, with 2m racks on 2 sides. Boundary conditions and other domain properties were chosen to represent the real scenario as close as possible. For the geometry,
it is generated using double grading to provide for a finer meshes close to the walls and floor. The drone is tested at different hovering heights (y = 2m / 1.5m / 1m). Temperature evaluation of the downwash is obtained through the simulation in OpenFOAM to determine the heat transfer efficiency through convection and conduction, which are the only mechanisms affecting the outcome. In conclusion, the lower the hovering height of the drone, the higher the overall change in temperature will be.Bachelor of Engineering (Mechanical Engineering
Design, development and testing of multicopters: part 2 – flight control
No full textIn the recent years, the propeller-based multicopter has seen a massive rise in popularity among remote control enthusiasts because of its simplicity in design. However, this has also led to the lack of incentive to innovate beyond the propeller-based design. As an attempt at innovation, the Jet Propulsion Multicopter Project (JPMP) was initiated to explore the feasibility of a jet-propelled multicopter.
The purpose of this study is to lay the groundwork for the first phase of the JPMP. Within the span of this study, the Experimental Gimbaled Nozzle Module (EGNM) was built and tested. Two prediction models were also programmed in MATLAB to estimate the thrust and vectoring performances of the EGNM. In the course of the experiments, the thrust prediction model had demonstrated consistency in its predictions but the mechanical limitations of the EGNM left something to be desired. Possible improvements on the prediction models and the EGNM were then explored for future development.Bachelor of Engineering (Aerospace Engineering
On the flow behaviour of 2D flexible airfoils
No full textThis thesis studies the on flow behaviour of the corrugated airfoil proposed by B. G Newman
et al. [1]. Unlike previous studies by Flint et al. [2], this study put the flexibility and
deformation of the airfoil into consideration. As the wings of real life dragonfly wings are
flexible in nature, it is only natural to consider the airfoils used in fluid dynamic calculations
as flexible in order to better understand how insects such as dragonfly can achieve better
flight dynamics at low Reynold’s number with their wings. The aim of this study is to study
the lift and drag of the airfoil, the pressure distribution around, and streamline across the
flexible airfoil at different angle of attacks. A computational fluid dynamics programme was
set up and a flexible airfoil was placed in a low speed fluid flow at 11 different angles of
attack. A stiff airfoil with identical dimensions was placed in the exact same setting for
control purpose.
The lift coefficient of the flexible airfoil was found to be lower than that of the stiff airfoil but
the stall angle increased and stall was delayed. The drag coefficient of flexible airfoil was
also lower than the stiff airfoil and the lift over drag ratio for the flexible airfoil was lower
compared to the stiff airfoil at higher angles of attack.Bachelor of Engineering (Aerospace Engineering
Numerical simulations of vortex ring leapfrogging
No full textThis paper reports upon a numerical study on the leapfrogging of two elliptical vortex rings at Re=2200 and Re=4400. To start with, a single circular vortex ring model is developed and tested using Large Eddy Simulation in Ansys Fluent. A second model of two circular vortex rings leapfrogging is developed and simulated at Re=3000. Its results are compared with published simulation and experimental results to validate the leapfrogging behavior of the model. A single elliptical vortex ring model is developed as the third model. A simulation on single elliptical vortex ring of Aspect Ratio 3 at Re=2189 is conducted and compared to published simulation results to validate the axis switching behavior of the model. Finally, simulations of two elliptical vortex rings leapfrogging at Re=2200 and Re=4400 are conducted. Bifurcation is observed in both Reynolds numbers where the trailing ring is bifurcated into three rings. Two of these bifurcated rings at the sides collide and combine with the leading ring. The centre bifurcated ring reduced in size and travelled through the leading ring. Only one leapfrogging is possible with elliptical vortex rings at a separation distance of R0 independent of Reynolds number.Bachelor of Engineering (Aerospace Engineering
Hot-wire anemometry measurements of collared-jets
No full textThe purpose of this project is to conduct an experimental investigation using hot-wire anemometry to understand the effects of collared jet nozzles on jet flow. The collars used are namely circular, squared and triangular collared jets. Each collar shape can be altered in collar length for in depth analysis. Experiments are conducted in both stream wise and cross stream direction. The experimental data collected can be used to analyse centreline velocity decay, centreline turbulent intensity, virtual origin and cross stream velocity profile. The experimental results showed that triangular collared jet has the best centreline velocity decay and perhaps the most gradual cross stream velocity profile due to a higher expansion ratio compared with circular and squared collars. A higher expansion ratio would mean that there is an increased self-excitation in flow behaviour, hence aiding in jet mixing.Bachelor of Engineering (Mechanical Engineering
On the vortical behaviour of annular impinging jets
No full textThis study aims to examine and analyse the vortical behaviour of annular impinging jets upon convex cylindrical surfaces with diameter D = 20, 40 and 80 mm. Laser Induced Fluorescence (LIF) as well as Digital Particle Image Velocimetry (DPIV) experiments are performed at Reynolds number Re=370 with nozzle-to-cylinder separation distance of H = 20, 40 and 80 mm, while both scenarios along cylinder straight edges and curvature surfaces are studied. Observations are made on vortex shape, movement and location via LIF as well as DPIV results to conclude on vortical behaviours and flow dynamics. In depths comparison is done between flow pattern of different experiment configuration to determine the effect of various setup parameters. These behaviours are also compared with those of similar existing researches and possible explanation will be presented in this report.Bachelor of Engineering (Aerospace Engineering
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