Pixelated Flow facilities for tomorrow's fluid dynamics

Most incompressible wind tunnels are designed to generate flow at a range of speeds and have been optimized for mild spatiotemporal variability, large-scale unsteadiness, low background noise, and full dynamic similarity. However, current technological challenges in fluid dynamics, such as with urban air mobility, are increasingly complex with vehicles subjected to atmospheric turbulence, vehicle wakes, three-dimensional building vortices, and thermal updrafts -- all simultaneously. To enable controlled studies that reproduce the critical physics of such flows we need a fundamentally new concept, like the recently proposed distributed flow facility made of computer cooling fans. We have taken this a step further by creating a facility using computer fans on all of the flow facility walls that can generate stable flow-speeds up to 11 m/s. Custom software is used to control complex 1D, 2D, and 3D gusts that can be induced on a fixed aircraft within the tunnel.

Active Student(s): Carson, Manish

Turbulence enhances insects' life?

Invasive insect species such as mosquitos and moths are a major menace that draw billions of dollars in prevention and healthcare, in addition to causing nearly a million deaths each year. Host-seeking behavior – where mosquitos approach humans using air-borne odor cues from even 50 meters away – remains unexplored with insects employing robust tracking strategies, apparently leveraging the flow turbulence instead of resisting it. Understanding this could yield not only efficient insect control strategies but also robust bio-inspired algorithms for bio-chemical hazard tracking.
Active Student(s): Jay

Developing a Photoelastic Sensor to Measure Turbulent Shear Stresses

 

This research aims to develop a novel photoelastic sensor to study the time-resolved physics of momentum loss on the surfaces of large low-speed vehicles subjected to turbulent flows. While turbulence exerts only a few milli-Pascals of tangential stress, it contributes over 50% of the total energy cost by accumulating across the vehicle surface. Detecting this weak, time-varying signal over large areas in high Reynolds number flows remains challenging despite advances in sensing technology. Many indirect methods rely on assumptions, while the most direct method, oil film interferometry (OFI), provides only average measurements. This is insufficient to fully understand the causal relationship between turbulent motions, drag, and noise. The objective of this project is to develop an ultrasensitive, fast-response photoelastic sensor to measure local, instantaneous stress tensors, offering new insights into these dynamics.
Active Student(s): Alex

Archived Projects

Informing climate modelling and predictions

The recent AR6 Climate Change 2021 report by the Intergovernmental Panel on Climate Change (IPCC) highlights the state of the art in weather and climate predictions that rely on very high-resolution (< 200 m) simulations. However, it also highlights the handicaps to generating highly reliable projections of sea level rise, precipitation patterns, air pollution, and surface temperature. One of the key limitations is the paucity of near-surface planetary boundary layer physics where recent studies have shown Monin-Obukhov Stability Theory (MOST) to breakdown. To combat this, we need comprehensive data for accurate sub-grid scale models, through extensive field campaigns to document the boundary layer characteristics in the bottom fifty meters of the planetary boundary layer. We aim to deliver this by implementing a cost-effective, large scale, bubble tracking velocimetry technique over a broad range of flow conditions.

Making energy-efficient vehicles quieter

Designing energy-efficient vehicles to tackle climate change is an urgent challenge but it turns out that energy efficiency and aerodynamic noise are inversely related to each other. Noise is detrimental to human health and often constrains  aerodynamic efficiency through public policy. Extensive investigation of the canonical flat plate boundary layer and pipe flow has yielded well-accepted tools to predict drag penalty, structural vibrations, and noise. However, practical applications suffer from complicated boundary conditions and very high Reynolds numbers. Experiments that use cutting-edge techniques to investigate complex flows (with roughness, flexible surfaces, wall curvature etc.) are critical as they remain as the only feasible approach for high Reynolds number regime. 

Space-time structure of turbulent inflow to a rotor

Microphone sensitivity to wall shear stress

Quantitative Visualization of Atmospheric Flows

A novel sensor for large scale turbulent pressure