Dry Wall Research Articles

Unsung Heroes or Exploited Workers? Latino Migrant Day Laborers in Post-Harvey Houston and Critical Environmental Justice

Unsung Heroes or Exploited Workers? Latino Migrant Day Laborers in Post-Harvey Houston and Critical Environmental Justice Daniel Olmos (bio) In August 2017, Hurricane Harvey devastated the Houston metropolitan area and caused approximately $125 billion in property damage, becoming one of the most costly storms in US history. Media outlets and observers attended to the serious socioeconomic plight of homeowners by highlighting the flooding of 150,000 homes and over 60,000 displaced people living in shelters and hotels, as well as featuring the historic role that social media played in connecting first responders to victims when emergency call systems overloaded.1 The storm acutely devastated lowlying areas of Houston, which is home to many disinvested and disadvantaged communities of color—the flooding and the lackluster state response led many to evoke the dramatic scenes of racialized abandonment during Hurricane Katrina on New Orleans in 2005.2 As global warming increasingly intensifies tropical storm systems along coastal regions in the US, climate justice movements insist that the most vulnerable and marginalized communities—also the least responsible for deeply-rooted systemic inequities—are also the most negatively impacted by the effects of global warming.3 While much scholarship has emphasized post-hurricane recovery efforts from the vantage point of Houston residents and businesses, little attention has been paid to the incorporation of Latino migrant day laborers as veritable “second responders” and, even less, as subjects of climate injustice and agents of environmentalism.4 Hurricane Harvey, a Category 4 storm, dumped fifty inches of rainfall and thirty-three trillion gallons of water into major commercial, [End Page 46] industrial, and residential corridors of the Houston region. The spectacles of evacuation and rescue that dominated media representation of the storm during the four-day news cycle obscured the eventual arduous process of recovery, in particular the prevailing mode of disaster recovery based on the exploitation of precarious racialized migrant labor. In the aftermath, unregulated small contractors and individual homeowners recruited mostly Latino day laborers to clear out moldy dry walls, replace rotted flooring, demolish dilapidated structures, and clean hazardous facilities, often with little or sometimes no pay and frequently without proper workplace safety equipment and conditions. “People don’t analyze it. They don’t see the consequences,” Martin Mares, a Mexican immigrant day laborer who has lived in Houston since 1995, noted during the recovery efforts. “They go to work without knowing whether the business will even pay them.”5 The erasure of day labor exploitation was extended by the mass-mediated appeals to resilience and grit in the face of a non-responsive state, namely through hashtag campaigns like #houstonstrong that promoted a neoliberal “rebuild above all else” model of recovery.6 In this context, this essay posits that the devastation wrought on the greater Houston area in the wake of Hurricane Harvey revealed not only the increasing vulnerability of US coastal regions to catastrophic weather patterns as a result of accelerated climate change, but also the socioeconomic relations and structures of racialized exploitation necessary for post-disaster reconstruction. I focus on the role of Latino migrant day laborers in greater Houston’s post-Hurricane Harvey rebuilding efforts and the environmental injustice implications, including the situatedness of day laborers in the face of ecological devastation. In the spirit of what Sarah Wald, David Vazquez, Priscilla Solis Ybarra, and Sarah Jaquette articulate as emerging “Latinx environmentalisms,”7 and drawing on a critical environmental justice framework through a qualitative sociological approach, I examine the conditions under which Latino migrant day laborers experienced racialized, economic, and ecological injustice following Hurricane Harvey, and finally how their subjection and struggle for dignity embodies a critical environmental justice politics in a moment of profound ecological crisis. [End Page 47] From the Anthropocene to Critical Environmental Justice The recruitment and exploitation of Latino day laborers in post-Harvey Houston was structured within the anthropocene era. In 2000, Paul Crutzen and Eugene Strermer introduced the concept of the anthropocene to explain a new stage of geohistorical development characterized by human activity as a “major geological force” and influence on climate patterns.8 While the anthropocene has become a buzzword with many different meanings, the category has fundamentally identified humanity as...

Numerical study on the flow and heat-transfer characteristics of horizontal finned-tube falling-film evaporation: Effects of liquid column spacing and wettability

The horizontal finned-tube falling-film evaporator has been successfully used in desalination and other industries. An effective three-dimensional Computational Fluid Dynamics (CFD) model was established to investigate the falling film and heat transfer characteristics of the horizontal finned-tube, and the numerical results were verified by experimental data. The influences of the liquid column feed spacing (S) and Reynolds number (Re) on the hydrodynamic characteristics, film thickness distribution and heat transfer characteristics for the finned-tube falling-film evaporation were explored. The fluid behavior and heat transfer performance with the variation of contact angle (α) were further revealed. At low Re, the liquid films fail to fully cover the tube surface with appearance of dry wall, causing the substantial decrease in wetting ratio and heat transfer performance. When Re = 684, the wetting ratio and average heat transfer coefficient were greatly improved, reaching 0.96 and 7922 W/m2·K, respectively. Heat flux has little effect on heat transfer performance. Additionally, as α increases, both the wetting ratio and the average heat transfer coefficient decrease. The average heat transfer coefficient drops from 8052 W/m2 K at 0° to 3692 W/m2 K at 80°. Furthermore, under different Re and α, smaller S exhibits better wetting properties and heat transfer characteristics.

Experimental and Modeling Study of Wall Film Effect on Combustion Characteristics of Premixed Flame in a Constant Volume Combustion Bomb

The primary objective of the present study was to investigate the impact of wall film on the combustion characteristics of premixed flames in internal combustion engines through the joint experimental and numerical techniques. The interaction between the premixed methane-air flame and n-dodecane film attached to the wall of a constant volume combustion bomb was experimentally examined. The flame propagation processes, as well as pressure evolution were quantitatively characterized. Then, computational fluid dynamic (CFD) simulation was performed incorporating the combustion chemistry model. To enable efficient simulation of the chemically reacting flow in engine chambers, a simplified modeling approach based on a two-step reaction scheme was developed. A compact reaction model for the selected model fuel n-dodecane was constructed and reduced to include 35 chemical species and 180 reactions. The flame propagation process of the premixed flame and its interaction with dry and wet walls was studied. The results showed that the propagation of the premixed flame could be divided into four stages, and the existence of the slit structure increased the instability of the flame structure in the near-wall region. The wall film tended to promote emissions, producing more unburned hydrocarbons, soot precursors and aldehydes.

The effect of a UNESCO world heritage site designation on willingness to pay to preserve an agri-environmental good: The case of the dry stone walls in Mt. Etna

In this paper, we explored the role that an authoritative institution can have on influencing how people perceive the importance of safeguarding environmental goods. We assessed how the recent UNESCO’s designation of the dry-stone walls in Mt. Etna (Sicily-Italy) as a World Heritage Site can affect Sicilian consumers’ willingness to pay (WTP) to preserve them. By referring to the concept of “appeal to authority”, we examined whether providing information about this recent UNESCO decision could influence public’s WTP to preserve the dry-stone walls of Mt Etna. Through a contingent valuation survey experiment, we found that respondents value the preservation of the dry-stone walls but only when respondents are informed about UNESCO’s decision that the WTP was sufficient enough to compensate farmers for the loss of income derived from maintaining the dry-stone walls. Our findings highlight the importance of information sent by an authoritative institution on reducing the effects of uncertainty in the valuation of environmental goods due to the unfamiliarity of such goods among people. Our results have important implications for policy makers as the role of institutions like UNESCO in increasing people’s WTP could increase awareness about the benefits of environmental goods’ preservation. A limitation of our study is that it is based on stated preferences. Future studies should also examine the effect of information on consumers’ WTP for preserving environmental goods with other methodological approach and in other geographical contexts.

Metallurgical Processing for Impregnated Thermionic Cathodes Manufacturing

A metallurgical process using a very high temperature Mo-Ru brazing filler alloy to join a controlled porous tungsten cathode button and a single-crystalline molybdenum cathode body for microwave tubes manufacture was developed†. The Mo-Ru brazing alloy was obtained by mixing and milling powders in the eutectic composition with a binder, and a braze paste was applied on the surface cathode parts. Brazing was performed in two temperatures by using a resistive dry hydrogen cold wall furnace for 10 minutes: at 1890 °C and 1967 °C. It was observed a fillability by the Mo-Ru system only in the tests performed in temperatures above 1967°C. The brazed samples were analyzed by Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy. It was observed absence of microstructural defects in the interface between the tungsten porous and dense molybdenum joint. Stress-strain tests, followed by SEM analysis were performed to determine the mechanical behavior of the brazing joining. The results indicate the origin region of the cracking and show an intergranular propagation; some evidence as grain cleavage indicates a brittle failure behavior.

Interstitial hygrothermal analysis for retrofitting exterior concrete wall of modern heritage building in Korea

Retrofitting modern heritage buildings aims at not only energy conservation, but also restoration and preservation of an architectural artefact. However, if envelope construction is adjusted and HVAC systems are replaced, the temperature and humidity profiles and air-tightness can also be transitional, thus condensation could occur on the surface and/or inside the structure. It is continuously emphasized to assess retrofit measures’ expected transitions in the hygrothermal performance of envelope and their potential condensation problems, prior to actual retrofit. The present study measured the surface moisture content of the concrete structure and built environment of three modern heritage buildings in Seoul. These results were used as the initial conditions for the hygrothermal analysis of insulations and vapor retarder. One modern heritage school was chosen for retrofit, then mock-up test, ISO 13788 steady-state analysis, and dynamic simulations by WUFI were used to analyze the risk of interstitial condensation in the exterior wall, according to the initial moisture content of concrete wall and whether the vapor retarder had been installed. For modern heritage buildings with fully dry concrete walls, the mock-up test verified that the risk of interstitial condensation between the concrete and insulation is low, regardless of whether the vapor retarder had been installed. Per ISO 13788 steady-state analysis and WUFI transient simulation, if PF board was used as the internal insulation for concrete exterior wall, the chance of interstitial condensation was also low, regardless of the initial moisture content and the use of a vapor retarder.

경량벽체로 구성된 소형 공동주택의 바닥충격음 특성 연구

Non-load bearing walls are widely used to facilitate the redesign of multi-residential housing spaces. However, as there are different noise characteristics between load bearing walls and non-load bearing walls, the effect of implementing non-load bearing walls on floor impact noise and slab vibration compared to load bearing walls needs to be studied. In this study, field experiments are carried out in a mock-up structure with various types of light-weight dry walls to evaluate the effect of implementing non-load bearing walls on floor impact noise and slab vibration. We find that there are little differences in the slab vibration and the floor impact noises between the different types of light-weight dry walls. This study also performs a series of numerical analyses for different types of light-weight walls and load-bearing walls to evaluate the effects on slab vibration and floor impact noise. From the numerical analyses, it is observed that the types of light-weight walls makes little difference to the effect on slab vibration and floor impact noise which is consistent with the field test result. However, the numerical analyses show that the floor impact noise characteristics are different between the load-bearing walls and the light-weight walls because the effective plates are different, although the configuration of the slab is the same.

Experimental and analytical investigation on shear behavior of profiled steel sheet dry board composite wall system

Profiled steel sheet dry board (PSSDB) composite wall/panel system with advantages (like lightweight, enhanced flexibility, low-cost, simple pre-fabrication/erection process, no temporary formwork requirement etc.) is an innovative construction technology that has significant potential to be used as a viable alternative to its conventional counterparts in earthquake prone region. No significant research study is available on the structural behavior of PSSDB composite walls under in-plane shear loading. Nineteen PSSDB panels consisted of single profiled steel sheet (PSS) assembled with single or double plywood dry board (DB) are tested under shear loading to failure. The effects of boundary frame, central opening, concrete in-fill, fastener orientation, and panel geometry on load-deformation response, strength and failure modes are investigated and compared. Analytical models for shear capacities of PSSDB composite system of various configurations are developed based on modified code-based/existing equations and their performance validated using experimental results. These analytical models can be used by engineers in designing PSSDB composite system for practical construction.

How Did Sheep Save the Day? The Role of Dry Stone Wall Heritage and Agropastorality in Historical Landscape Preservation. A Case-Study of the Town of Cres Olive Grove

The dry stone wall landscape surrounding the town of Cres is a unique cultural landscape; it is one of the largest well-preserved historical olive groves in the Croatian Adriatic, while simultaneously serving as pasture for sheep. Still, there are currently no studies that capture this landscape as a multifunctional whole or which acknowledge its relevance within the current multidisciplinary discussions. The aim of this paper is to clarify past and current circumstances surrounding and affecting it. The study focuses on two main pillars of landscape preservation: (1) dry stone wall structures and (2) agro-pastoral practices; giving an overview of its historical formation and current management and trends. The goal is to establish knowledge that can be used as a foundation for the management of this area and present a good practice example for the preservation of historical landscapes in the Mediterranean region. The research involved combined desk and fieldwork: cartographic data analysis, literature analysis, GIS elaboration, terrestrial and aerial photographs and observations, followed by interviews with local informants. Continuous investing in the production of quality olive oil and the evolution of the landscape into a multifunctional agro-pastoral-touristic space is what enabled its preservation. This multifunctionality can only be matched by a diversity of scientific studies and this study aimed at providing the first step—a foundation for the identification of the values of the Cres landscape, with the scope of better precising further planning and management.

Numerical simulation of two droplets impacting upon a dynamic liquid film

The impact of droplets on the liquid film is widely involved in industrial and agricultural fields. In recent years, plenty of works are limited to dry walls or stationary liquid films, and the research of multi-droplet impact dynamic films is not sufficient. Based on this, this paper employs a coupled level set and volume of fluid (CLSVOF) method to numerically simulate two-droplet impingement on a dynamic liquid film. In our work, the dynamic film thickness, horizontal central distance between the droplets, droplets’ initial impact speed, and simultaneously the flow velocity of the moving film are analyzed. The evolution phenomenon and mechanism caused by the collision are analyzed in detail. We find that within a certain period of time, the droplet spacing does not affect the peripheral crown height; when the droplet spacing decreases or the initial impact velocity increases, the height of the peripheral crown increases at the beginning, and then, because the crown splashed under Rayleigh–Plateau instability, this results in the reduction of the crown height. At the same time, it is found that when the initial impact velocity increases, the angle between the upstream peripheral jet and the dynamic film becomes larger. The more obvious the horizontal movement characteristics, the more restrained the crown height; the spread length increases with the increase of the dynamic film speed, droplet spacing and the initial impact velocity. When the liquid film is thicker, more fluid enters the crown, due to the crown being unstable, the surface tension is not enough to overcome the weight of the rim at the end of the crown, resulting in droplets falling off.

Evaluating the Impact of Indoor Insulation on Historic Buildings: A Multilevel Approach Involving Heat and Moisture Simulations

The energy refurbishment of historic buildings is a complex task for building envelope designers who need to carefully consider building conservation guidelines and principles. In most cases, external wall insulation techniques can determine an unacceptable alteration of the historical value of a building. For this reason, internal wall insulation techniques have been used widely in the last few decades. Nevertheless, dealing with internal wall insulation requires a complex design to avoid the risk of condensation and moisture-related pathologies. Moreover, an internal wall insulation may have a relevant impact on indoor comfort conditions. In this paper, the Monastery of Santa Maria de Monfero in Galicia (Spain) has been adopted as a building case study to compare different technological solutions based on: (i) an insulating plaster layer, (ii) dry counter wall systems. In the first step, heat and moisture transfer simulations of the wall components were performed to analyze the hygrothermal behavior of the different alternatives considering two different climate conditions. In a second step, a simulation of the whole building was performed to analyze the impact of the retrofitting strategies on the indoor climate and on the building heating and cooling demand. The obtained results show that the counter wall solution leads to higher energy savings during the heating season in the colder winter climate. However, the use of insulating thermal plaster could also be a viable solution since they lead to several advantages in summer because of their higher thermal inertia. Therefore, the selection of the most appropriate insulation technique has to be evaluated carefully considering the outdoor/indoor climate and using a case-by-case approach.

Out-of-plane analysis of dry-stone walls using a pseudo-static experimental and numerical approach in scaled-down specimens

The objective of the present work is to study the response of dry stone walls subjected to out-of-plane forces and the influence of block‘s rugosity, joint arrangement, and border conditions. For this purpose, a series of scaled-down experimental tests on a tilting table and 3D numerical modeling using discrete elements, DEM, are proposed. In the numerical model, the applicability of some types of discrete elements is first studied. The preliminary analysis gives us useful information about the effects of the joint disposition and the border conditions in the response. Finally, the sensitivity of the response of the blocks to the parameter’s variations is analyzed. The experimental and numerical results show that the DEM method is adequate to simulate the failure mode, the displacement, and the lateral load of stone walls due to out-of-plane lateral loads considering the effect of the irregularity of the blocks, joint arrangement, and border conditions.

In-plane lateral cyclic behaviour of lime-mortar and clay-brick masonry walls in dry and wet conditions

This paper presents an experimental investigation into the structural and material response of ambient-dry and wet clay-brick/lime-mortar masonry elements. In addition to cyclic tests on four large-scale masonry walls subjected to lateral in-plane displacement and co-existing compressive gravity load, the study also includes complementary tests on square masonry panels under diagonal compression and cylindrical masonry cores in compression. After describing the specimen details, wetting method and testing arrangements, the main results and observations are provided and discussed. The results obtained from full-field digital image correlation measurements enable a detailed assessment of the material shear-compression strength envelope, and permit a direct comparison with the strength characteristics of structural walls. The full load-deformation behaviour of the large-scale walls is also evaluated, including their ductility and failure modes, and compared with the predictions of available assessment models. It is shown that moisture has a notable effect on the main material properties, including the shear and compression strengths, brick–mortar interaction parameters, and the elastic and shear moduli. The extent of the moisture effects is a function of the governing behaviour and material characteristics as well as the interaction between shear and precompression stresses, and can lead to a loss of more than a third of the stiffness and strength. For the large scale wall specimens subjected to lateral loading and co-existing compression, the wet-to-dry reduction was found to be up to 20% and 11% in terms of stiffness and lateral strength, respectively, whilst the ductility ratio diminished by up to 12%. Overall, provided that the key moisture-dependent material properties are appropriately evaluated, it is shown that analytical assessment methods can be reliably adapted for predicting the response, in terms of the lateral stiffness, strength and overall load-deformation, for both dry and wet masonry walls.

Early Australian rabbit-proof fences: paling, slab and stub fences, modified dry stone walls, and wire netting

AbstractFences were critical in the fight against rabbits in colonial Australia. Initially, domestic rabbits were farmed in pens or paddocks fenced with paling fences or walls. Wild-caught rabbits imported from England escaped and became serious pests from the 1850s. As their status changed from protected private property to a major pest, the functions of fences changed to fencing rabbits out. Legislation requiring or specifying rabbit-proof fences lagged several years behind recognition of rabbits as a problem. Most log and brush fences in infested districts were burnt to destroy rabbit harbour. Dry stone walls were modified in many ways; paling, slab, picket and stub fences were all tried, but were unsuccessful, and by 1886 netting was standard. Using examples from the rich agricultural Western District and the considerably poorer Mallee Region of Victoria, this article describes the many forms of rabbit fences used between the 1850s and the mid-1880s. All of the experimentation with different structures was by individual landholders, with colonial governments conspicuous by their lack of involvement until they erected rabbit-proof barrier fences.

HEAP - The autonomous walking excavator

The demand and the potential for automation in the construction sector is unmatched, particularly for increasing environmental sustainability, improving worker safety and reducing labor shortages. We have developed an autonomous walking excavator - based one of the most versatile machines found on construction sites - as one way to begin fulfilling this potential. This article describes the process of converting an off-the-shelf construction machine into an autonomous robotic system. First we outline the necessary sensing equipment for full autonomy and the novel actuation of the legs, and compare three different complementary actuation principles for the excavator's arm. Second, we solve the state estimation problem for a general wheeled-legged robot. Beside kinematic measurements, it includes GNSS-RTK, to absolutely reference the machine on a construction site. Third, we developed individual controllers for driving, chassis balancing and arm motions allowing for fully autonomous operation. Lastly, we highlight the machine's potential in four different real-world applications, e.g. autonomous trench digging, autonomous assembly of dry stone walls, autonomous forestry work and semi-autonomous teleoperation. On top, we also share some development insights and possible future research directions.

Experimental study on the interaction between flame propagation and wall film in a confined vessel

With applying the direct injection strategy, it is inevitable to develop a liquid fuel wall film, which would significantly affect the combustion process afterward. In this work, the interactions between the premixed flame propagation and wall film in a confined vessel were investigated thoroughly. The methane-air premixed mixture was used to generate the flame, while the wall films were prepared by directly placing liquid fuel onto a plate surface that attached inside of the combustion chamber. Besides laminar flame, a turbulent premixed flame was also induced by putting a cluster of columnar obstacles on the path of the flame propagation to study the effects of turbulent flame on film consumption. The flame propagation processes, as well as the pressure variations, were captured and recorded by a high-speed Schlieren photographic system and a pressure transducer, respectively. The flame morphology, propagation speed, and pressure characteristics were compared to each other under dry and film walls by varying initial conditions. The impact of different types of wall films and chamber structures (e.g., with and without narrow channels of different widths) on the flame propagation was also examined. Results indicated that the flame propagation process was accelerated because the high reactivity species within the film get vaporized and well mixed into the methane-air combustion mixture. Under turbulent combustion conditions, the vaporization and loss of the film were enhanced by the strong heat transfer as indicated by the Schlieren images observations. Furthermore, different fuel/oil films have different mass loss rates under combustion conditions due to the vaporization property. N-dodecane fuel film has the highest film loss rate, followed by diesel and lube oil film. In addition, the turbulent flame leads to higher film loss as well by increasing the heat transfer.

Grasping and Object Reorientation for Autonomous Construction of Stone Structures

Building large and stable structures from highly irregular stones is among the most challenging construction tasks with excavators. In this letter, we present a method for grasp planning and object manipulation that enables the world's first autonomous assembly of a large-scale stone wall with an unmanned hydraulic excavator system. Our method utilizes point clouds and mesh surface reconstruction of stones in order to plan grasp configurations with a 2-jaw gripper mounted on the excavator. Besides considering the geometry of the stone to sample force closure grasps, the grasp planner also takes into account collision constraints during object pick and place, informed by a LiDAR based point cloud map. Furthermore, we show an approach to reorient arbitrarily shaped objects that are not feasible to be directly placed at the desired location without violating collision constraints. Using a physics engine, we find a settled intermediate pose that allows direct placement and is reachable from the initial stone pose. The applicability of the proposed grasp planning method is demonstrated with the construction of a dry stone wall composed of over one hundred boulders using an autonomous excavator. We show a high primary grasp success rate (82.2%) and illustrate how the system recovers from slippage by relocating the object and re-planning the grasp correspondingly.

Reduction-consistent multiple-relaxation-time lattice Boltzmann equation method for wall bounded N immiscible incompressible fluids

A multiple-relaxation-time (MRT) lattice Boltzmann equation (LBE) method is developed for N-phase (N≥ 2) flow with moving contact lines. In the model, MRT LBE is applied to solve the incompressible Navier-Stokes equation, and another MRT LBE is developed for fluid-fluid interface capturing, where the MRT LBE has the reduction-consistent property and can guarantee the mass conservation of each phase. The wettability of solid in the presence of N (N≥ 2) immiscible fluids can be achieved by a reduction-consistent wettability boundary condition, which can treat different contact angle between the fluids and the solid. A series of benchmark tests such as spreading of droplets and compound droplet on a solid wall, and compound droplet impact on a dry solid wall are conducted to validate the MRT LBEs, and it is shown that the predictions of LBE agree well with the theory/other numerical results.

Dry stone constructions – intangible cultural heritage and sustainable environment

PurposeThe purpose of this paper is to demonstrate how safeguarding intangible cultural heritage contributes to environmental conservation and favours sustainable development of natural landscapes. To do so, the authors will focus on a study of dry stone constructions, which have been recognised by United Nations Educational, Scientific and Cultural Organization (UNESCO) as Intangible Cultural Heritage.Design/methodology/approachThe research has been carried out through three methodologies: the search and review of archives (historical and administrative documents), ethnographic methodology (field work and interviews) and case studies.FindingsThe abandonment of dry stone constructions is placing rural zones at risk, as they assume a strategic role in environmental conservation efforts. This article seeks to highlight the importance of safeguarding this cultural heritage.Research limitations/implicationsThe art of dry stone walling has its origins in ancient times and can be found in numerous regions around the world. The main ideas of this paper may be applied to many of the places where this vernacular architecture can be found.Practical implicationsSome stakeholders may apply the results of this study to identify new uses for heritage resources that allow maintenance of ecosystems while at the same time safeguarding intangible cultural heritage.Social implicationsThis paper stresses the importance of raising public awareness of cultural heritage and vernacular architecture, its link with traditional activities such as farming and livestock raising, the rural landscape and reinforcement of cultural identity and historical memory.Originality/valueThis study illustrates the actions taken by UNESCO to safeguard intangible cultural heritage and the effects of those actions. It also considers dry stone constructions from the perspective of environmental sustainability, an area that has been subject to limited study.

Dynamic behavior of metal droplet impact on dry smooth wall: SPH simulation and splash criteria

Droplet impingement is a widespread phenomenon in nature and industrial production. Different from the problem of light drop/wall impact, which has been investigated early and sufficiently, few researches are found on the dynamic behavior and modeling of heavy drop impingement, which is widely existed in the field of plasma spray, 3D printing and ejecta mixing caused by detonation, etc. In this paper, the behavior of different metal drops impinging on dry smooth wall is studied based on Smoothed Particle Hydrodynamics (SPH) method. A newly splash threshold is proposed for heavy drop impact, and the difference of splash criteria between light drop and heavy drop is analyzed. The results show that incident kinetic energy is an important factor to determine the outcomes of heavy droplet impact. When the incident kinetic energy is relatively low, the metal droplet would spread, and the maximum spreading radius increases with the increase of kinetic energy. With higher incident kinetic energy, the droplet would splash, and the proportion of secondary droplets increases with the increase of incident kinetic energy. Higher droplet viscosity will hinder its spreading, but when splash occurs, it will promote the increase of secondary droplet. The increase of surface tension would suppress droplet spreading rate, but it has little effect on the maximum spreading radius. The splash criteria of heavy droplet impinging on dry smooth wall is proposed as K=Oh⋅Re1.5346=3341.95. The splash threshold of heavy droplet is higher than that of light droplet within the range of Re < 4000, owing to the higher surface tension of heavy droplet. When Re > 4000, the outcomes of light droplet impact show strong randomness, thus no uniform splash threshold can be found, while the metal droplet has a uniform splash threshold within the range of Re <100000.