Experiments on Microbursts
Abstract
An isolated dynamic microburst is modelled in our laboratory by releasing a volume of salt water solution which is slightly heavier than ambient fresh water, allowing it to fall onto a horizontal plate and develop into a turbulent microburst vortex ring. Several visualization methods are used to observe the event and a high resolution video camera is used to record it. Quantitative results are achieved in two ways. The descending rates and wind front positions of the modelled microburst are measured from the video record by means of a digitizing cursor on a monitor. A cross wire type hot film anemometer is utilized to detect the transient wind velocity induced by the vortex ring at different radial positions near the impact center. Ensemble averaging methods are applied to get an average velocity time traces. An inviscid scaling law is derived from the Boussinesq approximation and is used to present the experimental results in an appropriate dimensionless form. This model exhibits many of the features of naturally occurring microbursts which are known to be a hazard to aviation. Experimental results are in good agreement with the real microburst DL191, which occurred at Dallas Fort -Worth airport in August 1985, and with an "average" microburst abstracted from field investigations.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- January 1994
- Bibcode:
- 1994PhDT........18Y
- Keywords:
-
- VORTEX RINGS;
- WINDSHEAR;
- Engineering: Aerospace; Physics: Atmospheric Science