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Papers by Andrea Bisignano
Meteorological Applications, Oct 31, 2023
Meteorological Applications
In this work we aim at investigating a negatively buoyant plume and providing quantitative estima... more In this work we aim at investigating a negatively buoyant plume and providing quantitative estimates of the effect of a background rotation on the dynamics of the turbulent plume, with a focus on the intensity of the fluxes of ambient fluid entrained within the plume depending on the parameters that control the flow dynamics. The experiments were performed taking advantage of recent works on the dynamics of atmospheric downburst and on the analysis of the entrainment coefficient in plumes with varying dynamical states
Heat and Mass Transfer, Jan 15, 2022
Boundary-Layer Meteorology, 2015
We present a hybrid Lagrangian stochastic model for buoyant plume rise from an isolated source th... more We present a hybrid Lagrangian stochastic model for buoyant plume rise from an isolated source that includes the effects of temperature fluctuations. The model is based on that of Webster and Thomson (Atmos Environ 36:5031–5042, 2002) in that it is a coupling of a classical plume model in a crossflow with stochastic differential equations for the vertical velocity and temperature (which are themselves coupled). The novelty lies in the addition of the latter stochastic differential equation. Parametrizations of the plume turbulence are presented that are used as inputs to the model. The root-mean-square temperature is assumed to be proportional to the difference between the centreline temperature of the plume and the ambient temperature. The constant of proportionality is tuned by comparison with equivalent statistics from large-eddy simulations (LES) of buoyant plumes in a uniform crossflow and linear stratification. We compare plume trajectories for a wide range of crossflow velocities and find that the model generally compares well with the equivalent LES results particularly when added mass is included in the model. The exception occurs when the crossflow velocity component becomes very small. Comparison of the scalar concentration, both in terms of the height of the maximum concentration and its vertical spread, shows similar behaviour. The model is extended to allow for realistic profiles of ambient wind and temperature and the results are compared with LES of the plume that emanated from the explosion and fire at the Buncefield oil depot in 2005.
International Journal of Environment and Pollution, 2019
<p>An Eulerian model for the dispersion of a passive tracer over a simplified slope... more <p>An Eulerian model for the dispersion of a passive tracer over a simplified slope driven by a thermally driven circulation is presented here. The source of the tracer is point-like and the emission continuous, the local circulation is a pure anabatic flow modelled following Prandtl&#8217;s (1942) steady-state model. The eddy diffusivity is considered constant along the vertical direction. The incapability of a classical Gaussian model to forecast the concentration field is shown through a comparison between the results of the Gaussian and Eulerian models. A study of the sensitivity of the concentration field to the position of the source and to the characteristics of the wind field is proposed. Moreover, a relationship between the position and the intensity of the ground concentration field, together with its dependence on the environmental parameters is found.&#160;</p><p>Prandtl L. 1942. F&#252;hrer durch die Str&#246;mungslehre, Chapter 5. Vieweg und Sohn: Braunschweig, Germany. [English translation: Prandtl L. 1952. Mountain and valley winds in stratified air, in Essentials of Fluid Dynamics: 422&#8211;425. Hafner Publishing Company: New York, NY]<br><br></p><p>&#160;</p>
<p>This contribution aims at presenting results from the project &#8220;Atm... more <p>This contribution aims at presenting results from the project &#8220;Atmospheric boundary-layer modeling over complex terrain&#8221;, a collaboration between the University of Trento, the University of Bolzano and the University of Innsbruck with the objective to evaluate the performance of turbulence and land surface parameterizations over mountainous terrain and to identify potential issues that have a large impact on model results and consequently on the quality of weather forecasts.</p><p>A set of Reynolds-averaged Navier-Stokes (RANS) simulations at 1 km horizontal resolution is performed in an idealized three-dimensional valley-plain topography, using typical geometrical features of a north-south Alpine valley, with ridges up to 1500 m above the valley floor and a distance of 20 km from crest to crest. Simulations are initialized with a linear and stable vertical profile of potential temperature, dry air and an atmosphere at rest. The aim of the modeling experiment is to evaluate the sensitivity of model results to planetary boundary layer (PBL) parameterizations, exploring the performance of the PBL schemes implemented in the Weather Research and Forecasting (WRF) model, including a newly developed k-&#949; closure. Results from the RANS simulations are compared against a large-eddy simulation (LES) with a resolution of 100 m, which is taken as the benchmark. A full diurnal cycle has been considered for the evaluation of numerical results, focusing on the development of along- and cross-valley thermally-driven circulations and on the associated thermal field both in the nighttime and in the daytime phases. The sensitivity of model results to the change of the PBL scheme is assessed using as key metrics the strength and the timing of the thermally-driven circulations, as well as the vertical profiles of mean and turbulent quantities, when available. Results show that in most cases there is a good agreement between RANS simulations and the LES considering the main features of both along- and cross-valley circulations and the diurnal evolution of the thermal stratification. In particular, the intensity of the along-valley wind is generally well-reproduced by all the RANS simulations, while higher discrepancies are found for the timing of the evening transition. On the other hand, RANS simulations are in good agreement with the LES considering the timing of slope winds, whereas the simulation of their intensity presents much more variability, especially during nighttime.</p>
This thesis is dedicated to my parents Manuela and Raffaele and my girlfriend Valentina who have ... more This thesis is dedicated to my parents Manuela and Raffaele and my girlfriend Valentina who have patiently tolerated me. "The next great era of awakening of human intellect may well produce a method of understanding the qualitative content of equations. Today we cannot. Today we cannot see that the water flow equations contains such things as the barber pole structure of turbulence that one sees between rotating cylinders. Today we cannot see whether Schrodinger's equation contains frogs, musical composers, or morality-or whether it does not. We cannot say whether something beyond it like God is needed, or not. And so we can all hold strong opinions either way."
This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at ... more This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at a local scale, over complex terrain, in order to reproduce the dispersion of a tracer gas released from an incinerator stack.
A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The... more A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The plume rise scheme is based on a stochastic differential equation for the potential temperature fluctuations coupled with the equations for the wind velocity fluctuation components. The new approach is tested against measured data from a water tank experiment (Weil et al., 2002). The results are discussed in terms of statistical indices and scatter plots. For the sake of comparison, the new scheme's performance is compared with the algorithm used in SPRAYWEB formerly proposed by Anfossi et al. (1993) which doesn't account for the temperature fluctuations. The results obtained with the novel plume rise scheme are generally satisfactory. A better agreement is found for the vertical standard deviation with respect to the results given by the Anfossi et al. (1993) scheme.
Quarterly Journal of the Royal Meteorological Society, 2019
This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at ... more This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at a local scale, over complex terrain, in order to reproduce the dispersion of a tracer gas released from an incinerator stack.
A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The... more A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The plume rise scheme is based on a stochastic differential equation for the potential temperature fluctuations coupled with the equations for the wind velocity fluctuation components. The new approach is tested against measured data from a water tank experiment (Weil et al., 2002). The results are discussed in terms of statistical indices and scatter plots. For the sake of comparison, the new scheme's performance is compared with the algorithm used in SPRAYWEB formerly proposed by Anfossi et al. (1993) which doesn't account for the temperature fluctuations. The results obtained with the novel plume rise scheme are generally satisfactory. A better agreement is found for the vertical standard deviation with respect to the results given by the Anfossi et al. (1993) scheme.
We developed a fluctuating plume model able to evaluate all the higher concentration moments only... more We developed a fluctuating plume model able to evaluate all the higher concentration moments only requiring the knowledge of the first one. The simple algorithm used to calculate the meander centroid component is independent of the method used to obtain the mean concentration field and makes the computational time lower than most meandering plume model versions. Thus it is especially suitable for practical applications.
Springer Proceedings in Complexity
A new modelling system, SMART, is under development for the simulation of accidental releases dis... more A new modelling system, SMART, is under development for the simulation of accidental releases dispersion. The interfacing code ARAMIS was originally created to interface the non-hydrostatic atmospheric model MOLOCH and the Lagrangian stochastic dispersion model SPRAY. Here, a comparison between simulations with the new modelling suite SMART and the RMS modelling system, applied in several previous assessment studies, is presented for a case of a release in complex terrain in southern Italy. The new suite is planned to be adopted as a tool for emergency response purposes in any part of the Italian territory at any time.
Springer Proceedings in Complexity
Meteorological Applications, Oct 31, 2023
Meteorological Applications
In this work we aim at investigating a negatively buoyant plume and providing quantitative estima... more In this work we aim at investigating a negatively buoyant plume and providing quantitative estimates of the effect of a background rotation on the dynamics of the turbulent plume, with a focus on the intensity of the fluxes of ambient fluid entrained within the plume depending on the parameters that control the flow dynamics. The experiments were performed taking advantage of recent works on the dynamics of atmospheric downburst and on the analysis of the entrainment coefficient in plumes with varying dynamical states
Heat and Mass Transfer, Jan 15, 2022
Boundary-Layer Meteorology, 2015
We present a hybrid Lagrangian stochastic model for buoyant plume rise from an isolated source th... more We present a hybrid Lagrangian stochastic model for buoyant plume rise from an isolated source that includes the effects of temperature fluctuations. The model is based on that of Webster and Thomson (Atmos Environ 36:5031–5042, 2002) in that it is a coupling of a classical plume model in a crossflow with stochastic differential equations for the vertical velocity and temperature (which are themselves coupled). The novelty lies in the addition of the latter stochastic differential equation. Parametrizations of the plume turbulence are presented that are used as inputs to the model. The root-mean-square temperature is assumed to be proportional to the difference between the centreline temperature of the plume and the ambient temperature. The constant of proportionality is tuned by comparison with equivalent statistics from large-eddy simulations (LES) of buoyant plumes in a uniform crossflow and linear stratification. We compare plume trajectories for a wide range of crossflow velocities and find that the model generally compares well with the equivalent LES results particularly when added mass is included in the model. The exception occurs when the crossflow velocity component becomes very small. Comparison of the scalar concentration, both in terms of the height of the maximum concentration and its vertical spread, shows similar behaviour. The model is extended to allow for realistic profiles of ambient wind and temperature and the results are compared with LES of the plume that emanated from the explosion and fire at the Buncefield oil depot in 2005.
International Journal of Environment and Pollution, 2019
<p>An Eulerian model for the dispersion of a passive tracer over a simplified slope... more <p>An Eulerian model for the dispersion of a passive tracer over a simplified slope driven by a thermally driven circulation is presented here. The source of the tracer is point-like and the emission continuous, the local circulation is a pure anabatic flow modelled following Prandtl&#8217;s (1942) steady-state model. The eddy diffusivity is considered constant along the vertical direction. The incapability of a classical Gaussian model to forecast the concentration field is shown through a comparison between the results of the Gaussian and Eulerian models. A study of the sensitivity of the concentration field to the position of the source and to the characteristics of the wind field is proposed. Moreover, a relationship between the position and the intensity of the ground concentration field, together with its dependence on the environmental parameters is found.&#160;</p><p>Prandtl L. 1942. F&#252;hrer durch die Str&#246;mungslehre, Chapter 5. Vieweg und Sohn: Braunschweig, Germany. [English translation: Prandtl L. 1952. Mountain and valley winds in stratified air, in Essentials of Fluid Dynamics: 422&#8211;425. Hafner Publishing Company: New York, NY]<br><br></p><p>&#160;</p>
<p>This contribution aims at presenting results from the project &#8220;Atm... more <p>This contribution aims at presenting results from the project &#8220;Atmospheric boundary-layer modeling over complex terrain&#8221;, a collaboration between the University of Trento, the University of Bolzano and the University of Innsbruck with the objective to evaluate the performance of turbulence and land surface parameterizations over mountainous terrain and to identify potential issues that have a large impact on model results and consequently on the quality of weather forecasts.</p><p>A set of Reynolds-averaged Navier-Stokes (RANS) simulations at 1 km horizontal resolution is performed in an idealized three-dimensional valley-plain topography, using typical geometrical features of a north-south Alpine valley, with ridges up to 1500 m above the valley floor and a distance of 20 km from crest to crest. Simulations are initialized with a linear and stable vertical profile of potential temperature, dry air and an atmosphere at rest. The aim of the modeling experiment is to evaluate the sensitivity of model results to planetary boundary layer (PBL) parameterizations, exploring the performance of the PBL schemes implemented in the Weather Research and Forecasting (WRF) model, including a newly developed k-&#949; closure. Results from the RANS simulations are compared against a large-eddy simulation (LES) with a resolution of 100 m, which is taken as the benchmark. A full diurnal cycle has been considered for the evaluation of numerical results, focusing on the development of along- and cross-valley thermally-driven circulations and on the associated thermal field both in the nighttime and in the daytime phases. The sensitivity of model results to the change of the PBL scheme is assessed using as key metrics the strength and the timing of the thermally-driven circulations, as well as the vertical profiles of mean and turbulent quantities, when available. Results show that in most cases there is a good agreement between RANS simulations and the LES considering the main features of both along- and cross-valley circulations and the diurnal evolution of the thermal stratification. In particular, the intensity of the along-valley wind is generally well-reproduced by all the RANS simulations, while higher discrepancies are found for the timing of the evening transition. On the other hand, RANS simulations are in good agreement with the LES considering the timing of slope winds, whereas the simulation of their intensity presents much more variability, especially during nighttime.</p>
This thesis is dedicated to my parents Manuela and Raffaele and my girlfriend Valentina who have ... more This thesis is dedicated to my parents Manuela and Raffaele and my girlfriend Valentina who have patiently tolerated me. "The next great era of awakening of human intellect may well produce a method of understanding the qualitative content of equations. Today we cannot. Today we cannot see that the water flow equations contains such things as the barber pole structure of turbulence that one sees between rotating cylinders. Today we cannot see whether Schrodinger's equation contains frogs, musical composers, or morality-or whether it does not. We cannot say whether something beyond it like God is needed, or not. And so we can all hold strong opinions either way."
This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at ... more This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at a local scale, over complex terrain, in order to reproduce the dispersion of a tracer gas released from an incinerator stack.
A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The... more A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The plume rise scheme is based on a stochastic differential equation for the potential temperature fluctuations coupled with the equations for the wind velocity fluctuation components. The new approach is tested against measured data from a water tank experiment (Weil et al., 2002). The results are discussed in terms of statistical indices and scatter plots. For the sake of comparison, the new scheme's performance is compared with the algorithm used in SPRAYWEB formerly proposed by Anfossi et al. (1993) which doesn't account for the temperature fluctuations. The results obtained with the novel plume rise scheme are generally satisfactory. A better agreement is found for the vertical standard deviation with respect to the results given by the Anfossi et al. (1993) scheme.
Quarterly Journal of the Royal Meteorological Society, 2019
This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at ... more This chapter presents preliminary results obtained from a WRF-CALPUFF modeling system applied at a local scale, over complex terrain, in order to reproduce the dispersion of a tracer gas released from an incinerator stack.
A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The... more A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The plume rise scheme is based on a stochastic differential equation for the potential temperature fluctuations coupled with the equations for the wind velocity fluctuation components. The new approach is tested against measured data from a water tank experiment (Weil et al., 2002). The results are discussed in terms of statistical indices and scatter plots. For the sake of comparison, the new scheme's performance is compared with the algorithm used in SPRAYWEB formerly proposed by Anfossi et al. (1993) which doesn't account for the temperature fluctuations. The results obtained with the novel plume rise scheme are generally satisfactory. A better agreement is found for the vertical standard deviation with respect to the results given by the Anfossi et al. (1993) scheme.
We developed a fluctuating plume model able to evaluate all the higher concentration moments only... more We developed a fluctuating plume model able to evaluate all the higher concentration moments only requiring the knowledge of the first one. The simple algorithm used to calculate the meander centroid component is independent of the method used to obtain the mean concentration field and makes the computational time lower than most meandering plume model versions. Thus it is especially suitable for practical applications.
Springer Proceedings in Complexity
A new modelling system, SMART, is under development for the simulation of accidental releases dis... more A new modelling system, SMART, is under development for the simulation of accidental releases dispersion. The interfacing code ARAMIS was originally created to interface the non-hydrostatic atmospheric model MOLOCH and the Lagrangian stochastic dispersion model SPRAY. Here, a comparison between simulations with the new modelling suite SMART and the RMS modelling system, applied in several previous assessment studies, is presented for a case of a release in complex terrain in southern Italy. The new suite is planned to be adopted as a tool for emergency response purposes in any part of the Italian territory at any time.
Springer Proceedings in Complexity