Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - THUNDERR (Detection, simulation, modelling and loading of thunderstorm outflows to design wind-safer and cost-efficient structures)

Teaser

OVERVIEWThe safety and sustainability of the built with regard to natural and anthropogenic actions are primary goals of engineering. The wind is the most destructive natural phenomenon: 70% of the damage and death caused by nature every year in the world comes from the wind...

Summary

OVERVIEW
The safety and sustainability of the built with regard to natural and anthropogenic actions are primary goals of engineering. The wind is the most destructive natural phenomenon: 70% of the damage and death caused by nature every year in the world comes from the wind. Evaluating its actions is therefore crucial for society.
The European wind climate and that of many countries in the world are dominated by extra-tropical cyclones and thunderstorms. The genesis and evolution of cyclones is known since the 1920s. Their actions on construction have been framed since the 1960s and engineering still uses these models. Thunderstorm is a complex, mysterious and devastating phenomenon that results in actions often more intense and damaging than the cyclonic ones.
Despite this awareness and the huge amount of research carried out in in the last 30 years on this topic, there is no model of thunderstorm winds and their actions similar to that established over half a century ago for cyclones. Likewise, there is no unified framework for cyclone and thunderstorm wind actions. This occurs because the complexity of thunderstorms makes it difficult to establish realistic and simple models; their short duration and small extension limit the available measures; there is a clear gap between research in atmospheric sciences and wind engineering.
This is a serious shortcoming in structural and civil engineering, as it gives rise to unsafe and/or overly expensive works. The unsafety of small and medium-height light structures is pointed out by their frequent damage and collapse in thunderstorm days. The excessive cost of tall buildings in areas dominated by thunderstorms is testified by the apparent absence of collapses, probably due to the fact that the wind speed due to thunderstorms is maximum at the ground.
The presence in Genoa of a leading wind engineering group with interdisciplinary expertise in atmospheric sciences, the creation of a unique and unprecedented wind monitoring network in previous European projects – Wind & Ports (WP) and Wind, Ports & Sea (WPS) - managed by this group, the existence of new laboratories to simulate large-scale thunderstorms, CFD developments and a huge network of international co-operations are epochal conditions to overcome these limits and to project wind science into a new era. The Advanced Grant 2016 awarded to the Project THUNDERR by the European Research Council is a major fruit of this background.
THUNDERR is an acronym of THUNDERstorm that expresses the innovative Roar of this research. It aims to detect thunderstorms, to create a database of meteorological records and scenarios, to conduct unprecedented laboratory tests and numerical simulations, to formulate a thunderstorm model appropriate for both atmospheric sciences and structural design, to change the format of wind actions, of engineering practice and of the codification system, to make building safer and more sustainable, to bring about a profound impact on society and its economy.
The Project is organized according to 3 objectives involving 10 Work Packages (WP) (Figure 01).

OBJECTIVE I - THUNDERSTORMS
Despite a lot of research, literature lacks of a thunderstorm model shared by scientific community, consistent with physical properties and suitable for simple engineering evaluations. This objective aims at formulating a novel, interdisciplinary and unitary model of the thunderstorm outflows, with the dual prospect of being itself a challenging scientific result and a robust basis to carry out engineering analyses with a ground-breaking impact on construction and society. This model would be the counterpart of the model diffused and shared worldwide from the ‘60s to represent synoptic events.

WP 1. Thunderstorm detection
An unprecedented wind monitoring network created by two previous EU projects (WP and WPS, Figure 02) will be enhanced by a novel LiDAR aiming to detect the position, diameter, direction, and translational speed of

Work performed

FOREWARD
The research on thunderstorms carried out at the University of Genoa originates from two European (EU) projects, “Wind and Ports” (WP, 2009-2012) (A) and “Wind, Ports and Sea” (WPS, 2013-2015) (H), financed by the European cross-border program “Italy–France Maritime 2007-2013”. They handled the wind safe management and risk assessment of the High Tyrrhenian seaport areas through an integrated set of tools including an extensive wind monitoring network, multi-scale numerical models, medium- and short-term forecast algorithms, and statistical analyses. Results are made available to port operators by means of an innovative Web GIS platform (K).
Realized in a geographic area well-known for the intense convective activity and its often dramatic consequences, the WP and WPS monitoring network produced an unprecedented amount of non-stationary wind speed records due to gust fronts potentially associated to thunderstorm outflows (B). This inspired two Italian projects, one supported by Compagnia di San Paolo (Wind monitoring, simulation and forecasting for the smart management and safety of port, urban and territorial systems, 2016-2018), and the other by the Italian Ministry for Instruction, University and Research (Identification and diagnostic of complex structural systems, 2016-2019), during which extensive research has been carried out on the downburst wind field (C, D, I, L) and on the wind loading and response of structures (E, F, G, J, M).
Hence it originated and drove forward the project THUNDERR – Detection, simulation, modelling and loading of thunderstorm outflows to design wind-safer and cost-efficient structures – awarded by an Advanced Grant 2016 of the European Research Council (ERC) under Horizon 2020 (2017-2022).
All the above cited papers (listed at the end of this report), being funded through other projects, are not included among THUNDERR products. Despite this, they represent a fundamental patrimony and a starting point on which the THUNDERR project is being developed.
The following provides an overview of the research activity carried out for the THUNDERR project (6, 7, 14, 15, 18, 21) and of the main obtained results, subdivided with regard to the objectives, work packages and tasks of the project.

OBJECTIVE I - THUNDERSTORMS
This objective aims at formulating a novel, interdisciplinary and unitary model of the thunderstorm outflows, with the dual prospect of being itself a challenging scientific result and a robust basis to carry out engineering analyses of the structural loading and response.

WP 1. Thunderstorm detection.
Starting from the unique wind monitoring network created by the two previous EU projects, WP and WPS, the aim of this WP is to strengthen such monitoring network and to create an unprecedented dataset to be disclosed to scientific community.

Task A. Wind monitoring.
The unique potential of the WP and WPS monitoring network has been enhanced by a Windcube 400S pulsed LiDAR scanning system installed in the Port of Genoa on 18th April 2018 (Figure 08). It detects the wind speed up to a nominal distance of 14 km, with a space step up to 100 m and a sampling frequency up to 1 Hz. It involves a specific software to record and to display data in real time. It is used with the perspective of detecting the touch-down position and the diameter of downdrafts, their direction and translational speed, and the background wind speed field in which they are embedded. At present, preliminary analyses of its measurements have been conducted with reference to stormy days. Systematic analyses will be conducted from 15 May 2019 in the framework of a Post Doc position awarded to Dr. Djordje Romanic.

Task B. Selective dataset.
During some previous projects a semi-automatic expert system has been realized that separates different wind events (C), namely synoptic extra-tropical cyclones, thunderstorm outflows and intermediate events. In the first part of the ERC project this proced

Final results

PROGRESS BEYOND THE STATE OF THE ART
A list of the main results provided by the ERC project beyond the state of the art is reported below for each project task.

Task A. Wind monitoring.
An already unique monitoring network developed during previous EU projects has been enhanced by a top generation Windcube 400S pulsed LiDAR scanning system installed in the Port of Genoa. Currently, this is one of the most extensive monitoring network all over the world.

Task B. Selective dataset.
A semi-automatic expert system has been improved and generalized to separate different wind events. A novel procedure has been implemented to link thunderstorm wind speed measurements and the weather scenarios in which these phenomena occur.

Task C. Signal processing.
A novel directional wind speed decomposition strategy has been implemented that takes into account the rapid direction shifts exhibited by thunderstorm outflows due to their translational movement. It opens the doors to advanced thunderstorm models in terms of wind speed, wind loading and wind-induced response.

Task D. Wind tunnel tests.
A novel scaling rule between laboratory tests and full-scale measurements have been developed.

Task F. Weather scenarios.
See task B.

Task H. Thunderstorm modelling.
A robust though preliminary thunderstorm model that takes into account the stationary downdraft, its translation speed and the background flow into which the thunderstorm is embedded has been created, showing its capacity not only to replicate actual events, but also to extract their main parameters.

Task J. Thunderstorm statistics.
It was proved that in High Mediterranean area, likewise in many parts of the world, thunderstorms are the main events as far as concern mean return periods above 5-20 years, namely for the safety of structures.

Task K. Thunderstorm simulation.
The equivalent wind spectrum technique formulated by P.I. several years ago has been embedded into a hybrid simulation strategy, providing synthetic thunderstorm outflow wind fields in a rapid and effective way. The results seem to be exceptional. Using a mono-variate simulation of a stationary Gaussian process, it has been possible to re-construct a multi-variate non-stationary non-Gaussian random process with unbelievable precision.

Task M. Dynamic response.
A systematic comparison between the previously formulated response spectrum technique and time domain simulations led to improve both of these methods up to obtain results extremely close to each other. This is absolutely impressive considering the burden of time-domain solutions and the simplicity of the response spectrum technique. In addition, fully new results were obtained with regard to directional analysis, never performed before, of the structural response to downbursts.

EXPECTED RESULTS UNTIL THE END OF PROJECT
Intersecting the list of the obtained results with the objectives of the project, the following aims will be pursued until the end of the project.

Task A. Wind monitoring
An extensive number of thunderstorm records will be put at disposal of scientific community through an open portal.

Task C. Signal processing
An advanced model of the time-space evolutionary properties of the wind speed profiles will be set. The development of a POD time-space evolutionary reduced modal representations will be pursued. An answer will be given to an unresolved question: have downbursts similar properties everywhere, or do they depend on local climate ?

Task D. Wind tunnel tests
The role of surface roughness in downbursts will be elucidated. Large-scale downbursts will be generated in order to understand if the resultant wind field due to the downdraft, the cell translation and the background flow can be reconstructed through a vector combination of the partial wind fields.

Task E. CFD simulations
A variety of CFD simulations will be calibrated through full-scale and laboratory tests, in order to recognize the most efficient numerical simulation s

Website & more info

More info: http://www.thunderr.eu.