Cameron Southgate-Ash
About
My research project
The effect of multi-scale roughness on the structure of atmospheric turbulencePhase I - A series of wind tunnel experiments will be designed and carried out to assess the turbulence structure over urban morphologies, characterized by tall buildings of uniform height and a packing density that is typical of megacity environments. These will be performed in the ‘A’ wind tunnel at the University of Surrey. The level of details characterising the model of the buildings will be progressively increased, to produce a multi-scale roughness. The turbulence structure developed over single- and multi-scale roughness will be compared to assess similarities/differences. Scaling laws based on the characteristic length scales of the morphologies will be explored. For all cases, the drag generated by the morphologies will be measured by instrumenting a building with static pressure ports on all faces. This drastically reduces the uncertainty inherent in the law of the wall in rough wall turbulent boundary layers. To incorporate the effect of spatially heterogeneous surfaces, several velocity profiles will be collected with Laser Doppler Anemometry (LDA) to allow for analysis of spatially averaged quantities.
Phase II - The effect of ABL stratification will be examined in the unique ‘EnFlo’ wind tunnel (NERC National facility) at the University of Surrey. Similar single- and multi-scale urban roughness will be investigated (via LDA). Concentration measurements via Fast-response Flame Ionisation Detector (FFID) are also planned to complement the velocity profiles, and inform the urban dispersion phenomenon as a function of both the atmospheric stability and buildings length scales.
Supervisors
Phase I - A series of wind tunnel experiments will be designed and carried out to assess the turbulence structure over urban morphologies, characterized by tall buildings of uniform height and a packing density that is typical of megacity environments. These will be performed in the ‘A’ wind tunnel at the University of Surrey. The level of details characterising the model of the buildings will be progressively increased, to produce a multi-scale roughness. The turbulence structure developed over single- and multi-scale roughness will be compared to assess similarities/differences. Scaling laws based on the characteristic length scales of the morphologies will be explored. For all cases, the drag generated by the morphologies will be measured by instrumenting a building with static pressure ports on all faces. This drastically reduces the uncertainty inherent in the law of the wall in rough wall turbulent boundary layers. To incorporate the effect of spatially heterogeneous surfaces, several velocity profiles will be collected with Laser Doppler Anemometry (LDA) to allow for analysis of spatially averaged quantities.
Phase II - The effect of ABL stratification will be examined in the unique ‘EnFlo’ wind tunnel (NERC National facility) at the University of Surrey. Similar single- and multi-scale urban roughness will be investigated (via LDA). Concentration measurements via Fast-response Flame Ionisation Detector (FFID) are also planned to complement the velocity profiles, and inform the urban dispersion phenomenon as a function of both the atmospheric stability and buildings length scales.
University roles and responsibilities
- Postgraduate Research Student
My qualifications
ResearchResearch interests
Environmental flows and urban dispersion
Rough wall boundary layers
Fractal generated turbulence
Research interests
Environmental flows and urban dispersion
Rough wall boundary layers
Fractal generated turbulence
Publications
Urban forms characterised by multi-scale roughness can drastically modify the wind structure within cities affecting both pedestrian comfort and air quality at street level. For simplicity, most urban flow studies focus on cuboid buildings with a single length scale. We consider six forms to assess how additional length scales impact urban flow: two reference cuboids that differ in aspect ratio (mean building height to width) cases (Standard, 1; Tall, 3) plus two additional fractal iterations of each. The six models have the same mean building width, height, and frontal area but their length scale characteristics differ. These are used in wind tunnel experiments within a deep turbulent boundary layer. The length scale differences are found to affect the drag force exerted by the buildings in a non-negligible way (up to 5 and 13% for Standard and Tall buildings, respectively). The added length scales also modify the wake lateral spread and intensity of the turbulence fluctuations, with smaller the length scales having the lower (higher) intensity of fluctuations in the near (far) wake. Additionally, the strength of the vortex shedding emanating from the buildings is reduced by introducing systematically smaller length scales. This work suggests that omission of additional length scales can lead to inaccuracies in drag and wake recovery estimations. The reduction in intensity of vortex shedding found with each fractal iteration could have engineering applications (e.g. reducing vibration).