Page 101 - Undergraduate Research Opportunities Program Proceedings 2017-18

School of Engineering
Department of Mechanical & Aerospace Engineering

relevance has been defined. Solving this foundational problem can help solve other problems defined by more
complicated wing configurations, such as the aerodynamics of cloth-based wingsuits.

Forced synchronization of a low-density jet

Supervisor: LI Larry / MAE
Student: REN Da Wei David / PHYS Course: UROP1100, Fall

Low-density jets are a canonical model of fuel injector flows within aircraft and rocket engines. It is well known that low-
density jets can exhibit global instability in the form of self-excited axisymmetric oscillations. It is less well known,
however, that such jets can also exhibit global instability in the form of self-excited helical oscillations. The existence of
such helical modes has been predicted before in the local linear spatiotemporal stability analysis of Coenen, Sevilla, and
Sanchez for long circular injectors with thick shear layers, but they have yet to be found in experiments. We report
experimental evidence that low-density jets can exhibit global helical modes. We characterize the dynamics of the jet
with time-resolved Schlieren imaging and quantify the departure from axisymmetry with the phase angle between
diametrically opposite shear layers. On decreasing the non-dimensional injector length L−1 t = (Re a)/lt (where Re is the
jet Reynolds number, a is the jet radius, and lt is the injector length), we find that global instability switches from an
axisymmetric mode to a helical mode, with the latter being weaker than the former. This shows that it is possible to
create self-excited helical modes in laboratory low-density jets, provided that the shear layer at the nozzle exit is
sufficiently thick. Realisation of helical modes within combustion chambers may yield more homogeneous fuel-air mixing
and more turbulent flow. This may improve the environmental-friendliness, safety, and noise of combustion devices.

Designing Novel Efficient and Quiet Amphibious Aircraft for General Aviation

Supervisor: LIEM Rhea Patricia / MAE Co-Supervisor: ZHANG Xin / MAE
Student: HUI Wai Mong / AERO Course: UROP1100, Fall
LEUNG Kai Lok / MAE UROP1100, Fall

The aviation industry is expected to continuously grow in the coming decades, especially in rapid developing economies
like Asia. However, some places, like islands, are often inaccessible through existing conventional aircraft. The
constructions of airport in urban areas are also limited due to insufficient lands, where the infrastructures of rural areas
are not well-developed. Thus, some research and development efforts have been focused on designing amphibious
aircraft, which can take off and land on ground and on water surface. In this project, a group of final year students are
going to develop, build and fly a model-size amphibious aircraft. A reference model, ICON A5, will be used as the
template and different improvements, including ducted propeller and morphing wing designs, will be implemented to
the model and tested for their effectiveness. In this work, the efficiency of thrust generation in ducted propeller and the
airfoil shape of morphing wing are studied. Experimental results of ducted propeller and the comparison result of airfoil
shapes of morphing wing are summarized and evaluated to aid the design of the amphibious aircraft model.

Supervisor: LIEM Rhea Patricia / MAE Co-Supervisor: ZHANG Xin / MAE
Student: HUNG Kin Ting Ken / AERO Course: UROP1100, Spring

This project explores different designs for amphibious aircraft which is designated for areas which are previously not
accessible by traditional aircraft. In particular, this report focuses on the relationship between the presence of hydrofoil
and the take-off performance in water. Using CLARK-Y as a model of the hydrofoil for the amphibious aircraft,
Computational Fluid Dynamics (CFD) simulations are carried out to find out the lift coefficient and the drag coefficient of

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