(a) What do we do scientifically?
The laboratory of aerodynamics and acoustics (AA-Lab) conducts fundamental and applied research on flow stability, sound wave generation, and their control. Our interest goes beyond the traditional ‘aeroacoustics’ of turbulence. From a broader perspective, we are interested in dynamic systems, and their application in energy and environmental engineering. Classical acoustics without airflow does form an important subset of our work, but we emphasize the fact that the acoustics of gas and liquid is a branch of unsteady fluid dynamics. Usual structural vibration generates sound but we are far more interested in how it absorbs sound as part of a dynamic system. The key words for our lab are therefore: flow, sound, dynamics and stability.
(b) What are the engineering motivations for our work?
First, environmental noise pollution affects our quality of life, traffic and construction work being two major complices. Take Hong Kong as an example, one in seven lives in an environment where the noise level exceeds the tolerance set by the government. Industrial noise pollution affects both factory workers and nearby residents. Examples include metal workshops, power stations, etc. In advanced economies there are financial compensation schemes, but what we really need is acoustic solutions.
Aircraft noise is a special environmental concern with far reaching commercial consequences. Part of the reason for airports being located afar is their noise. The world’s first supersonic jetliner, Concord, retires prematurely partly due to its noise problems. In one of the projects we get involved, known as a ‘973’ project in China, we now explore new ways to reduce noise in anticipation of the launch of a new passenger aircraft.
Consumer product noise is one of our foci in R&D. Almost all electrical appliances have ventilation noise problems. Examples include computer/IT cooling fans, vacuum cleaners, hair dryers, extraction fans and the list goes on. Most of these have airflow and fan as the main noise source but occasionally vibration is also prominent. Classical acoustics is inadequate and it often leads to high energy (pressure) loss or bulky design.
Prevention of flow induced vibration is another category of our interest. Examples of applications include lifting surfaces of aircraft, turbomachinery blades working under high loading, oil pipelines and risers, human snoring and sleep apnoea, and blood flow through large vessels. Sound wave radiation may or may not be a factor but in others, such as the unstable combustion in gas turbine facility and aircraft after-burners, sound waves do play a central role and acoustic intervention is what it takes.
In flow instability, energy is pumped from the mean flow to catastrophic structural vibrations. On the other hand, such energy conversion might be deliberately set up for the purpose of energy harvesting from moderate to low speeds which are otherwise difficult to utilize in oceans and wind.
(c) The mission of our lab in HKU-ZIRI.
Our lab aims to become
an internationally known centre of excellence in developing new acoustic and fluid machinery technology,
an academic centre of excellence where people of different expertise enjoying working together on inter-disciplinary topics, and
an education hub for postdocs, postgraduates and undergraduate interns.
We plan to accomplish these missions through
developing joint R&D labs with industry and open up our facility to industry,
forge national and international collaborations on topics of scientific and/or social importance,
recruit and nurture research students, set up exchange programs and organize workshops and conferences.
We aim to build a team of 20-30 people with expertise in acoustics and vibration, fluid and structural mechanics, sensors, actuators and control, as well as essential aspects of product development. Interested researchers may contact the lab director by email with an updated CV. Potential applicants for postgraduate studies may follow this link for detailed information on admission while graduates of various levels may find our general recruitment advert useful. We also warmly welcome short-term visitors with an aim to establish long-term collaborations.