Skip to main content

Spatiotemporal Distribution and Structural impact Loading due to Artificial Debris Objects in Violent Flows

Final Report Summary - IMPLOADIS (Spatiotemporal Distribution and Structural impact Loading due to Artificial Debris Objects in Violent Flows)

The project "Spatiotemporal Distribution and Structural impact LOading due to Artificial Debris Objects in Violent Flows (impLOADis)" was concerned with experimental and numerical work on flow-structure interaction at University of Ottawa, Canada, at Waseda University, Japan and Leibniz Universität Hannover, Germany. The primary focus was on the entrainment and advection of artificial debris such as cars, containers, or pieces from destructed buildings. Besides extensive experimental testing of shipping containers, a second focus lied on parametrization of debris from tsunami in general; thirdly it was researched how it spatiotemporally distributes in violent flows as appearing during dam breaks, flash floods, storm surges or tsunamis. Innovative radio-frequency based and inertial measurement technique by motion sensors were applied for object tracking. Impact loading to buildings and infrastructure from multiple artificial debris will be assessed which eventually leads to significantly improved design guidelines. This research contributes to European and international resilience and safety against natural disasters. It is anticipated that key results of the research such as spreading functions of debris initially at rest will find entry into progressively developed codes and standards, in Europe and worldwide. This research will be useful to policy makers involved with developing building standards and those actively seeking to improve safety and resilience of Europe’s coastal population.
Key results of this research are published in peer-reviewed journals and presented at a number of conferences. The full list of publications is presently maintained at the following link: http://nilsgoseberg.de/os/nils/publications. Key results presented by the publications are summarized below through providing the most important publications. These are:
Paper 1: N. Goseberg et al. “Nonintrusive spatiotemporal smart debris tracking in turbulent flows with application to debris-laden tsunami inundation.” In: Journal of Hydraulic Engineering (2016). doi: 10.1061/(ASCE)HY.1943-7900.0001199
The development of a novel debris tracking system aiming at recording six-degree-of-freedom (6DOF) motion of free floating objects in a free-surface flow is reported in this paper. The object tracking and recording system termed smart debris utilizes off-the-shelf electronic components in a combined and time-synchronized manner. A miniaturized inertial measurement unit (IMU) to determine 3-axis orientation and a bluetooth low-energy system to derive position were combined to form the smart debris for deriving 6DOF spatiotemporal information. The proposed system is scalable and was applied to up to 9 down-scaled shipping containers for proof of concept. Prior to the system’s deployment in experiments where debris dynamics were investigated more systematically, the system’s performance was yet assessed by thoroughly conducting component tests in carefully controlled laboratory conditions. Various prescribed trajectories such as stationary, linear and oscillatory paths were used to assess the system’s overall performance yielding positioning accuracies of 0.05m to 0.25mhorizontally and 0.42mvertically. Likewise, orientation recording was found to be satisfactorily either with standard deviations of up to 11.4°. The proposed smart debris system was successfully applied in experimental research with floating objects, yet with nonintrusive characteristics. It is hence seen to be a promising new laboratory tool in problems such as breakwater studies, large wooden debris tracking in the field and sports analytic studies.
Paper 2: J. Stolle, I. Nistor, and N. Goseberg. “Optical tracking of floating shipping containers in high-velocity flow.” In: Coastal Engineering Journal 58.1650005 (2016)
Despite improved image acquisition capabilities and increased computational power, the problem of tracking individual debris or groups of debris floating in high-volume, high-velocity flows appeared substantial as appropriate routines to detect and distinguish debris in image frames was missing. Thus, the paper provides adequate routines to track multiple objects in an automated manner by sequentially applying techniques such as color thresholding, blob analysis, Kalman filtering, and Hungarian algorithm to images acquired by an overhead mounted camera. The routine was successfully tested for downscaled shipping containers that were dislodged from an initially dry harbour area and entrained into a tsunami-like flow. Results show excellent agreement with manually determined debris trajectories and the routines allow to track up to 9 debris specimen at once. Accuracy however decreases as debris agglomerates and with varying lighting conditions that affected the images taken at the scene. The routine however depicts the first successful attempt to track floating debris in conditions of high-velocity flows that model extreme hydrodynamic conditions.
Paper 3: I. Nistor et al. “Experimental investigations of debris dynamics over a horizontal plane.” In: Journal of Waterway, Port, Coastal, and Ocean Engineering 04016022 (2016). doi: 10.1061/ (ASCE)WW.1943-5460.0000371
Results of a study that focused on the entrainment, spreading and longitudinal displacement of up to 18 shipping containers are presented in this paper. A simplified harbor setting with a horizontal stacking area attached to a horizontal harbor basin was used to model a stacking ground under attack of a broken tsunami-like bore. The bore was generated by a newly-build tsunami wave basin and debris in the form of shipping containers was applied. While the hydraulic boundary condition was kept constant, it was possible to investigate how the number of shipping containers present on the harbor apron and its initial placement on dry ground influenced the spreading and maximum longitudinal displacement. The smart debris system as presented in Goseberg et al. was used to track the individual debris trajectories to determine their overall displacement characteristics. Spreading angle and maximum horizontal displacement are important to designers and harbor planners; these were approximated by linear equations to describe the debris’ behavior in cases where an extreme hydrodynamic flow hit. The usefulness of the smart debris system was successfully proven with even more debris specimen than was previously reported.
Paper 4: N. Goseberg et al. “Experimental analysis of debris motion due the obstruction from fixed obstacles in tsunami-like flow conditions.” In: Coastal Engineering 118 (Dec. 2016), pp. 35–49. doi: 10.1016/j.coastaleng.2016.08.012
A set-up identical the one presented in Nistor et al. was further used to investigate the effect that vertical obstacles have on the propagation of debris. Again, debris was modeled to depict shipping containers and the smart debris system was utilized. Unlike those tests conducted to study debris entrainment and dispersion over a plain harbor area, obstacles were added in various arrangements to introduce what in realistic harbor environments infrastructure, houses and ware houses would be. The smart debris was capable of recording the trajectories of the shipping containers dislogded by an approaching broken tsunami-like bore. Contrary to previous tests, it was shown that spreading angles of the debris was not as significantly alters as compared with undisturbed conditions whereas maximum longitudinal displacement was significantly reduced. A reason for this difference lies within the fact that the surge over the horizontal apron was reduced as it reflected partially off the obstacles; as a result less momentum was available for the debris to be dispersed inland. In addition, the instruments and nonintrusive devices used for this research proved to be very valuable tools to investigate debris’ movement over a harbor area as it did not interfere or alter its path of propagation.