How does anemometer placement affect measurement accuracy of vehicle-mounted anemometers?

Wind measurements are an important part of gas leak plume detection, which we do by truck.  I’ve been working with ANSYS Fluent software and anemometer measurements from the mobile survey trucks to investigate vehicle-based wind measurements. My MSc. project is a field- simulation study comparing experimental field measurements with CFD simulations, to explain how anemometer placement and the vehicle’s external flow field,affect measurement accuracy of vehicle-mounted anemometers.

DSC_0061Along with Nayani Jensen, I conducted field tests in Saskatchewan to explore the effects of anemometer placement, vehicle speed, and wind yaw angle on measured wind speed and direction. We tested five different anemometer positions on the truck, and used stationary anemometers to compare against the mobile measurements.

TruckGeomWe found that our truck-mounted anemometer over-estimated wind speeds, particularly for low mounting positions, high vehicle speeds, and large side winds (> 40% of vehicle speed).  This indicated that corrections are needed for vehicle speed and wind yaw angle. Screen Shot 2018-04-25 at 10.58.56 AM

Screen Shot 2018-04-19 at 11.01.41 AMBack at the lab, we used a Toyota Tacoma CAD model to create Computational Fluid Dynamic (CFD) simulations using ANSYS Fluent, to study the flow field around our truck as a function of speed, yaw angle, and anemometer placements.  We replicated the conditions under which field tests were conducted, but ANSYS Fluent also allowed us to explore a much wider range of conditions.

Our simulations agreed very closely with field measurements.  We are working with the results from the CFD, and field components of this study, to improve our truck-based wind measurements by calibrating anemometer measurements for anemometer placement, vehicle speed, and wind yaw angle.

Measuring wind from trucks isn’t much different than measuring wind from bikes (see this blog post) or from other vessels in motion like boats. Modeling wind fields with CFD has proven a good substitute for field work in these applications.