Wind analysis in the early design stage: an empirical study of wind visualisation techniques for architects

This research develops a study about wind analysis techniques for rapid wind visualisation in the early design stage. It develops protocols for rapid visualisation and evaluation of wind phenomena around groups of buildings and complex architectural and urban windbreak screen morphologies for feedback into design. Interaction between wind and buildings produces aerodynamic phenomena, affecting the comfort level of pedestrian areas in urban environments. For this reason, architects have incorporated, in the design process, wind analysis technologies and expert consulting, to anticipate the possible wind effects that could require mitigation measures and even modifications in the final form of a project. In this sense, wind analysis in the earlier stage of the design process is a strategy that allows architects to consider wind in the conceptual designs of a project and to develop more sophisticated strategies to interact with and mitigate wind phenomena. Examples of the integration of wind visualisation in the early design stage are the CFD-PST (computational fluid dynamics - performance sketch tools), which have been developed to facilitate basic and preliminary wind analyses, conducted by architects, in the first stage of the conceptual design process. Previous research has addressed their impact in the design process and architects' practice (including other analysis and simulation programs) with comparisons between programs and interviews with architects. However, the performance of CFD-PST in resolving the problem of rapid wind visualisation for architects has not been well evaluated in more complex scenarios than those originally proposed, for instance, with multiple buildings or with wind porous architectural screens or in comparison with other techniques such as physical visualisation methods. The aim of this research is to investigate, through empirical wind visualisation studies and architectural explorations of windbreaks, the CFD-PST and other techniques for rapid wind visualisation, in order to evaluate their efficacy for architects' practice in the early design stage. The results of this research present an evaluation of these wind visualisation technologies as a clear hierarchy of efficacy for rapid feedback, regarding requirements of visualisation complexity and extension of generation process. In addition, the study suggests architectural protocols for rapid visualisation and feedback in design process workflows. Finally, this research examines design rules of aerodynamic features, through rapid wind visualisation, to improve architectural exploration of windbreak design, for outdoor microclimatic control

Challenges in imaging and predictive modeling of rhizosphere processes

Background Plant-soil interaction is central to human food production and ecosystem function. Thus, it is essential to not only understand, but also to develop predictive mathematical models which can be used to assess how climate and soil management practices will affect these interactions. Scope In this paper we review the current developments in structural and chemical imaging of rhizosphere processes within the context of multiscale mathematical image based modeling. We outline areas that need more research and areas which would benefit from more detailed understanding. Conclusions We conclude that the combination of structural and chemical imaging with modeling is an incredibly powerful tool which is fundamental for understanding how plant roots interact with soil. We emphasize the need for more researchers to be attracted to this area that is so fertile for future discoveries. Finally, model building must go hand in hand with experiments. In particular, there is a real need to integrate rhizosphere structural and chemical imaging with modeling for better understanding of the rhizosphere processes leading to models which explicitly account for pore scale processes

Fluid tunnel research for challenges of urban climate

Experimental investigations using wind and water tunnels have long been a staple of fluid mechanics research for a large number of applications. These experiments often single out a specific physical process to be investigated, while studies involving multiscale and multi-physics processes are rare due to the difficulty and complexity in the experimental setup. In the era of climate change, there is an increasing interest in innovative experimental studies in which fluid (wind and water) tunnels are employed for modelling multiscale, multi-physics phenomena of the urban climate. High-quality fluid tunnel measurements of urban-physics related phenomena are also much needed to facilitate the development and validation of advanced multi-physics numerical models. As a repository of knowledge in modelling these urban processes, we cover fundamentals, recommendations and guidelines for experimental design, recent advances and outlook on eight selected research areas, including (i) thermal buoyancy effects of urban airflows, (ii) aerodynamic and thermal effects of vegetation, (iii) radiative and convective heat fluxes over urban materials, (iv) influence of thermal stratification on land-atmosphere interactions, (v) pollutant dispersion, (vi) indoor and outdoor natural ventilation, (vii) wind thermal comfort, and (viii) urban winds over complex urban sites. Further, three main challenges, i.e., modelling of multi-physics, modelling of anthropogenic processes, and combined use of fluid tunnels, scaled outdoor and field measurements for urban climate studies, are discussed

Fluid tunnel research for challenges of urban climate

Experimental investigations using wind and water tunnels have long been a staple in fluid mechanics research. These experiments often choose a specific physical process to be investigated, whereas studies involving multiscale and multiphysics processes are rare. In the era of climate change, there is increasing interest in innovative experimental studies in which fluid (wind and water) tunnels are used in the modeling of multiscale, multiphysics phenomena of the urban climate. Fluid tunnel measurements of urban-physics-related phenomena are also required to facilitate the development and validation of advanced multiphysics numerical models. As a repository of knowledge for modeling these urban processes, we cover the fundamentals, experimental design guidelines, recent advances, and outlook of eight selected research areas, i.e., (i) absorption of solar radiation, (ii) inhomogeneous thermal buoyancy effects, (iii) influence of thermal stratification on land-atmosphere interactions, (iv) indoor and outdoor natural ventilation, (v) aerodynamic effects of vegetation, (vi) dispersion of pollutants, (vii) outdoor wind thermal comfort, and (viii) wind flows over complex urban sites. Three main challenges are discussed, i.e., (i) the modeling of multiphysics, (ii) the modeling of anthropogenic processes, and (iii) the combined use of fluid tunnels and scaled outdoor and field measurements for urban climate studies

Study of ventilation strategies, in agricultural buildings through CFD modeling and experimental analysis.

Environmental control in agricultural and agro-industrial buildings is a very important and topical subject which falls within the domain of precision agriculture and smart food processing. There is a growing interest in the study of systems able to combine active and passive environmental control techniques and in the development of methodologies for modeling and simulating the environmental conditions in the agro-industrial sector. These ones need a process of validation and experimental calibration, but they can investigate specific aspects and variations of the thermo-fluidynamic phenomena involved in the control of environmental parameters. The computational fluid dynamic application (CFD) can give these opportunities and it has been used to study animal comfort in farms, distribution of temperature and humidity in greenhouses, to define structural improvement of greenhouses and to investigate effective ventilation strategies. This thesis is focused on the ventilation aspects in agricultural buildings, with the aim of considering improvement actions to optimize and act on airflow conditions in an experimental greenhouse and in a cellar, where climate control is extremely important. The natural ventilation of a glass greenhouse has been investigated with a particular focus on the effects of internal shading screens on the internal fluid-dynamic and on the crop growing conditions. A deep focus on the characterization of this type of screens has been carried out, with the aim of identifying applicable methodologies for this purpose. Finally, a smart system has been created to be placed in a cellar, for the improvement of the air flows around the barrels, which would thus prevent the molds formation and avoid air stagnation areas. Different configurations have been analyzed to identify the optimal design of the system. In conclusion, CFD approach has allowed to reach conclusions on possible decisions or strategies to improve the ventilation for improving the production and food quality conditions

Adaptive wall wind tunnels: A selected, annotated bibliography

This bibliography, with abstracts, consists of 257 citations arranged in chronological order. Selection of the citations was made for their value to researchers working to solve problems associated with reducing wall interference by the design, development, and operation of adaptive wall test sections. Author, source, and subject indexes are included

Identification and Attenuation of Losses in Thermoacoustics: Issues Arising in the Miniaturization of Thermoacoustic Devices

Thermoacoustic energy conversion is based on the Stirling cycle and uses sound waves to displace and compress the working gas. When this process occurs inside a porous medium that is subject to a temperature gradient, a thermoacoustic engine creates intense sound. Conversely, when strong sound waves interact with a porous medium, a temperature gradient can be imposed through the attenuation of the pressure amplitude, creating a thermoacoustic refrigerator. The device size is a limiting factor to widespread use. This work investigates issues arising in their miniaturization in three separate ways. To date, the thermal properties of the driving components are largely ignored during the design phase, partially because the traditional design ``works,' and partially because of a lack of understanding of the thermal energy fluxes that occur during operation. First, a direct quantification of the influence of the thermal conductivity of the driving components on the performance of a thermoacoustic engine and refrigerator is performed. It is shown that materials with low thermal conductivity yield the highest sound output and cooling performance, respectively. As a second approach to decreasing the footprint of a thermoacoustic system, the introduction of curvature to the resonator tube was investigated. A CFD analysis of a whole thermoacoustic engine was performed, and the influence of the stack assembly on the flow behavior was investigated. Nonlinearities in the temperature behavior and vortices in the flow close to the stack ends were identified. Resonator curvature prompts a decrease in the amplitude of the pressure, velocity, and temperature oscillations. Furthermore, the total energy transfer from the stack to the fluid is also reduced. Finally, through combining the aforementioned investigations, an optimization scheme is applied to a standing wave engine. A black box solver was used to find the optimal combination of the design parameters subject to four objectives. When focusing solely on acoustic power, for example, the device should be designed to be as large as possible. On the other hand, when attempting to minimize thermal losses, the stack should be designed as small as possible

Modeling a Field Application of In Situ Bioremediation of Perchlorate-Contaminated Groundwater Using Horizontal Flow Treatment Wells (HFTWs)

Perchlorate contaminated groundwater is rapidly becoming a significant environmental remediation issue for the Department of Defense. In this study, an existing numerical model that simulates the operation of a Horizontal Flow Treatment Well (HFTW) system to effect the in situ biodegradation of perchlorate through the addition of an electron donor is modified to include a submodel that describes bioclogging. Bioclogging restricts flow out of the HFTW due to the accumulation of biomass directly adjacent to the well. The modified model is then applied to an existing perchlorate contaminated site that will be used for an evaluation of the HFTW technology. Simulations were conducted to determine the impact of altering various engineered parameters on HFTW performance. Simulation results indicate that higher time averaged electron donor concentrations and HFTW pumping rates lead to more perchlorate degradation in terms of total mass of perchlorate removed. Simulation results also indicate that varying the electron donor addition schedule has little impact on HFTW performance. The simulations conducted in this study show that, regardless of the engineered parameter values, bioclogging does not impact the ability of the HFTW technology to effect in situ biodegradation of perchlorate at the evaluation site