Laser Doppler Anemometer (LDA) replacement

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The boundary-layer environmental wind tunnel at Trent University (TEWT) was designed and constructed for simulating the transport of particulate matter by wind. Nearing three decades in operation, this facility is a well-established international leader in aeolian transport research. It is the only facility of its type in the world that is equipped to run under full climate control with varied air temperature (-10 deg C to 35 deg C) and relative humidity (3% to 85%). It is capable of simulating, for example, wind erosion on a farm in Lethbridge during a drought; particle emissions from tailings ponds and stockpiles in the arctic at subfreezing temperatures; and seasonal variation in airborne microplastics transport surrounding waste management facilities throughout Canada. The barrier that we currently face is that our LDA processor, which has run almost continuously during operation of the wind tunnel over the last 13 years, is malfunctioning and cannot be repaired by the manufacturer. It urgently needs to be replaced so that we can fulfill our immediate obligations to sustain graduate student training; conduct experiments on microplastics transport in the atmosphere as a Project Partner with NERC funded colleagues in the UK; and remain competitive in obtaining contract work with industry and various public agencies to assess emission rates and controls. Since acquiring the LDA through a CFI grant awarded in 2009, we have used this instrument daily to carry out research supported by $740K in NSERC Discovery Grant funding. Particles under investigation in our lab may include either aerosols that travel over long distances (km) while in suspension, or larger particles with sufficient mass to constrain their motion to low ballistic hops (cm), and/or creep over short distances (mm). These may originate from sources that are either mineral, organic or anthropogenic, but all are well known to influence air quality and human health. In our daily operations we require a Laser Doppler Anemometer (LDA) to measure the kinetics of both the turbulent airflow structure, which entrains and propels the particles of interest, as well as the particle cloud. A non-contact 2D LDA offers many advantages over older technologies in that it samples rapidly and accurately without inducing flow perturbation caused by inserting a bluff body instrument directly in the flow, particularly one that can be destroyed by particle impact. Using this instrument, our lab was first to capture direct synchronous measurements showing that airflows saturated with particulate matter have increased turbulence intensity. Our overarching aim in future work is to assess the effects of a changing climate on the kinetics of aeolian transport systems that exist throughout high latitude, cold climate regions characteristic of Canada. Such work will build on the pivotal contributions of the TEWT lab toward fundamental understanding of particle transport in atmospheric boundary-layer flows.