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1. Tsunami Debris Damming Drag Forces And Associated Coefficients On Elevated Coastal Structure Columns

   https://doi.org/10.59490/coastlab.2024.732  

   DOYLE, KELLEN; KOH, MYUNG-JIN; JAYASEKARA, RAVINDU; COX, DANIEL; LOMONACO, PEDRO; PARK, HYOUNGSU; KAMESHWAR, SABARETHINAM (April 2024, CoastLab 2024: Physical Modelling in Coastal Engineering and Science)

   Tsunami overland flow induces hydrodynamic loads on coastal structures and may transport various objects located within the inundation zone, which could become debris and exacerbate hydrodynamic loading. In the process of adopting “the first national, consensus-based standard for tsunami resilience” (Chock, 2016) in the form of ASCE 7-16 Chapter 6: Tsunami Loads and Effects, emphasis was placed on evaluating debris transport and impact forces. This is evidenced by the robust body of literature regarding physical model experiments of these processes and thorough design procedures for both load considerations in current structural engineering standards (ASCE, 2022). Debris damming forces, resultant of debris being transported and accumulating against structures, are less thoroughly studied, having only recently begun to transition from steady flow experiments to transient flow conditions representative of coastal inundation events. A recent pair of experiments bridges this gap, comparing debris damming via steady-state, subcritical flow conditions to that caused by a dam-break style hydraulic bore (Stolle et al., 2018). That paper aimed to study debris dam formation, stability, and loading as well as runup of the flow onto idealized structural columns. Another study varied debris quantity, orientation, and arrangement to determine the effect had on damming and impact loads (Shekhar et al., 2020), however neither compared findings to current standards. The experimental work presented herein represents initial findings of a multi-year experimental campaign to better understand the mechanisms that lead to debris damming and increased structural loading. This work builds upon previous studies by using larger scale debris elements, more numerous debris fields, and more trials to better model such a stochastic process as debris damming. Three different incident wave conditions also led to varied hydrodynamics at the column specimen. In later phases, this campaign will also investigate the debris damming consequences of heterogeneous debris, which more accurately represent highly variable debris fields observed in post-event site surveys (Nistor et al., 2017). This paper aims to compare experimental debris dam loading parameters to those in the current ASCE 7-22 standard (ASCE, 2022). Namely, evaluating conservatism of ASCE 7-22 design values for: overall drag force on buildings, minimum closure ratios used in load determination, and empirical rectilinear structure drag coefficients during both debris accumulation and quasi-steady debris damming phases. 

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2. Quantifying and Understanding Structural Loading from Wave-Driven Debris Fields

   https://doi.org/10.1061/9780784484395.052  

   Mascarenas, Dakota; Motley, Michael R.; Eberhard, Marc O.; Arduino, Pedro; Serrone, Abbey (September 2022, ASCE Ports 22)

   During a tsunami or storm surge event, coastal infrastructure and ports are subject to a series of disparate physical hazards that can cause significant damage and loss of life. Among these, debris impact loading during inundation events is chaotic, complex, and thus far minimally understood, especially when considering the accumulation of individual debris into a large debris field. This work provides the results of a comprehensive experimental study of the impact and subsequent damming of chaotic debris fields, including more than 400 individual trials; this scope of this paper describes the experimental design and initial analysis of wave-driven debris-induced loading for select configurations. These data include both the impact phenomena and subsequent damming by debris accumulation and find strong correlation between increasing debris field density and high impact forces. High frequency impact forces and low frequency damming signals are considered via fast Fourier transform methods. Overall trends in wave-induced debris forcing from large debris fields are presented. 

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3. Tsunami debris motion and loads in a scaled port setting: Comparative analysis of three state-of-the-art numerical methods against experiments

   Bonus, Justin; Spröer, Felix; Winter, Andrew; Arduino, Pedro; Krautwald, Clemens; Motley, Michael; Goseberg, Nils (December 2024, Coastal engineering)

   We present an international comparative analysis of simulated 3D tsunami debris hazards, applying three state-of-the-art numerical methods: the Material Point Method (MPM, ClaymoreUW, multi-GPU), Smoothed Particle Hydrodynamics (SPH, DualSPHysics, GPU), and Eulerian grid-based computational fluid dynamics (Simcenter STAR-CCM+, multi-CPU/GPU). Three teams, two from the United States and one from Germany, apply their unique expertise to shed light on the state of advanced tsunami debris modeling in both open source and professional software. A mutually accepted and meaningful benchmark is set as 1:40 Froude scale model experiments of shipping containers mobilized into and amidst a port setting with simplified and generic structures, closely related to the seminal Tohoku 2011 tsunami case histories which majorly affected seaports. A sophisticated wave flume at Waseda University in Tokyo, Japan, hosted the experiments as reported by Goseberget al. (2016b). Across dozens of trials, an elongated vacuum-chamber wave surges and spills over a generic harbor apron, mobilizing 3–6 hollow debris-modeling sea containers-, in 1–2 vertical layers against friction. One to two rows of 5 square obstacles are placed upstream or downstream of the debris, with widths and gaps of 0.66x and 2.2x of debris length, respectively. The work reports and compares results on the long wave generation from a vacuum-controlled tsunami wave maker, longitudinal displacement of debris forward and back, lateral spreading angle of debris, interactions of stacked debris, and impact forces measured with debris accelerometers and/or obstacle load-cells. Each team writes a foreword on their digital twin model, which are all open-sourced. Then, preliminary statistical analysis contrasts simulations originating off different numerical methods, and simulations with experiments. Afterward, team’s give value propositions for their numerical tool. Finally, a transparent cross-interrogation of results highlights the strengths of each respective method. 

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4. Experimental Study of Dynamic Icing Process on a Pitot Probe Model

   https://doi.org/10.2514/1.T6782  

   Hu, Haiyang; Al-Masri, Faisal; Tian, Linchuan; Hu, Hui (July 2023, Journal of Thermophysics and Heat Transfer)

   An experimental study was conducted to characterize the dynamic ice accretion process over the surface of a typical aeronautic Pitot probe model under different icing conditions. The experimental study was conducted in the Icing Research Tunnel available at Iowa State University. While a high-speed imaging system was used to record the dynamic ice accretion process, a three-dimensional (3D) scanning system was also used to measure the 3D shapes of the ice layers accreted on the test model. While opaque and grainy ice structures were found to accrete mainly along the wedge-shaped lip of the front port and over the front surface of the probe holder under a dry rime icing condition, much more complicated ice structures with transparent and glazy appearance were observed to cover almost entire surface of the Pitot probe under a wet glaze icing condition. While a flower-like ice structure was found to grow rapidly along the front port lip, multiple irregular-shaped ice structures accreted over the probe holder under a mixed icing condition. The characteristics of the icing process under different icing conditions were compared in terms of 3D shapes of the ice structures, the profiles of the accreted ice layers, the ice blockage to the front port, and the total ice mass on the Pitot probe model. The acquired ice accretion images were correlated with the 3D ice shape measurements to elucidate the underlying icing physics. 

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5. Tsunami-driven debris experiment with varied density group conditions

   https://doi.org/10.17603/ds2-w6cr-s920  

   Park, Hyoungsu; Cox, Daniel (January 2021, Designsafe-CI)

   It presents an experimental study of tsunami-driven debris transport over the flat testbed. We utilize two types of debris elements, which have the same shape but different material (wood, HDPE) to create debris of different density. We considered variations in the grouping of debris (wood only, mixed wood and HDPE, and HDPE only), parameterized by the mean specific gravity (SGg). The final dislocations and local velocity of debris elements were optically measured and compared to flow velocity. The effects of obstacles on the passage of debris and the probability of collision to obstacles were examined and the process of debris-debris and debris-obstacle interactions from debris entrainment to final dislocation was studied. The curated data could be utilized to understand initial debris entrainment, and espeically utilized to verify/validate a numerical debris transportation model. This work highlights the importance of considering debris density in estimating the longitudinal distance and spreading angle. These variables were less dependent on the initial configuration of the debris field. Future studies should consider other aspects of the phenomena, including a better understanding of the potential impact by debris on obstacles, the role of the return flow in determining the debris trajectory, and investigations of the obstacles that more realistically reflect urban shorelines subjected to strong overland flow. 

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