Assessment of RANS turbulence closure models for predicting airflow in neutral ABL over hilly terrain

Implementing wind farms in heights of a hilly terrain where wind speed is expected to be large may be viewed as a means to increase wind energy production without occupying fertile lands. Micro sitting of a wind farm in these conditions can gain dramatically from CFD simulation of fluid flow in the ABL above complex topography. However, this issue still poses tough challenges regarding the turbulence model to be used and the way to operate the near wall treatment in the presence eventually of separation. In this work, prediction capacity of RANS turbulence models was studied for a typical hill under the assumption of steady state and incompressible airflow regime in neutral ABL. Two models were analyzed by using COMSOL Multiphysics software packages. These included standard , and shear-stress transport . The most up-to-date procedures dedicated to near wall treatment were applied along with refined closer coefficients adjusted for the particular case of ABL. Considering wind tunnel test data, performance of the previous models was discussed in terms of converging mesh, computational time, reattachment point position and propensity of the model to retrieve the right level of turbulence flow in conditions of neutral stratifications. Then, a numerical simulation of the turbulent airflow over two slopes shapes of the symmetry hill by the validation of the experimental data has been then carried out. Both turbulence models agree well with air-velocity tested windward of the hills H3 and H5. Therefore, it was found that the standard model performs very well at the different positions of the low slope hill, and at the summit of a steep hill, but it over-predicts wind speed close to the wall, which requires an improvement of the near-wall treatment. However, the model in neutral case of the ABL was given consistent simulation results with experimental data for prediction of the flow separation and recirculation region at the leeward side of a steep hill, whereas standard model under the neutral condition and the model by using standard coefficients were failed to predict accurately detailed characteristics of recirculation region process.

Perceived Human-Induced Causes of Landslide in Chattogram Metropolitan Area in Bangladesh

This study investigates Land Use Land Cover changes in the Chattogram metropolitan area, the second largest city in Bangladesh. Using a questionnaire survey of 150 local inhabitants, the study explores perceived human-induced causes of landslides. Using time series Landsat images this study also analyzes Land Use Land Cover changes from 1990 to 2020. The analysis reveals built-up area extended rapidly during 1990 to 2020. In 1990, total built up area was 82.13km², which in 30 years, stood at 451.34km². Conversely, total vegetative area decreased rapidly. In 1990, total vegetation area was 364.31km², which reduced to 130.44 km² in 2020. The survey respondents identified extensive rainfall, hill cutting, steep hill, and weak soil texture as several reasons for landslide. Findings show that age and experience of facing landslide are two significant predictors to explain whether excessive hill cutting is solely responsible for landslide. Level of education and experience of facing landslide are statistically significant in explaining building infrastructure as solitary cause to landslide. Gender, age and income of the respondents significantly explain deforestation as the only responsible for landslide. Finally, gender, level of education, and income of the respondents significantly explain only excessive sand collection causes landslide.

Public vs Private: The Four Categories of Open-Air Spaces at the Late Minoan IIIC Middle Settlement at Monastiraki–Halasmenos (­Ierapetra, Crete)

On the eastern side of the Isthmus of Ierapetra (Crete), just to the north of the village of Monastiraki, and immediately to the south of the mouth of the Ha Gorge, is situated the Late Minoan IIIC (LM IIIC) settlement of Monastiraki – Halasmenos (Tsipopoulou 2011a, 323). It is one of six sites excavated in the northern part of the Isthmus (Figure 1) which were occupied at some point during the 12th century BC (Kavousi – Kastro, Kavousi – Vronda, Kavousi – Azoria, Monastiraki – Katalimata and Vasiliki – Kephala).1 The excavations of Halasmenos by Metaxia Tsipopoulou and the late William D.E. Coulson, beginning in 1992,2 have revealed an apparently short-lived occupation at a location on a steep hill that projects from the face of the adjacent, steep escarpment, the Lamia (Figure 2).

We Walk

This chapter focuses on the author's experience with her twenty-one-year-old son, Jonah, who has severe autism as they walk around Atlantic City. It mentions home in Philadelphia, where they hike through Valley Forge National Park and Fairmount Park, the largest city park in the world. It also refers to their walk around their neighbors' field or up and down their driveway, which is harder than it sounds since it's a quarter of a mile up a steep hill. The chapter talks about the laps they did around the top deck of a cruise ship to the Bahamas but had to abort once they discovered how determined Jonah was to launch himself overboard the way he likes to jump off the little motorboat. It recounts their walk on the beach at Key Largo and down abandoned railroad tracks by the Susquehanna River in Maryland.

The Fortifications of Chalcis (Evripos/Negreponte/Egriboz), Greece

The aim of this paper is the study of the now destroyed fortifications of the Greek city of Chalcis (Evripos / Negreponte / Egriboz). Having been an important urban centre during the Early and Middle Byzantine Period, Chalcis was occupied by the Latins after the capture of Constantinople in 1204 and became a significant trade centre of Venice. By the end of the fourteenth century, the city became a Venetian holding. In 1470 the Ottomans captured the city after a brief siege. In 1688 the city was unsuccessfully besieged by the Venetians. And in 1833 it was annexed by the Greek State. In the end of the nineteenth century the fortifications of Chalcis were almost completely demolished during an attempt to reorganize and modernize the city. The fortified medieval city of Chalcis, the Kastro, had the shape of a long, irregular pentagon with maximum dimensions 400 x 700 m. It was surrounded on three sides, namely the north, west and south, by sea. Along its two other sides, the northeast and the southeast, there was a dry moat. Its fortifications had three gates, one on Euripus bridge and two on the land wall, through which the city was connected with Boeotia and Euboea, respectively. From the study of the fortifications, based on their depictions in old engravings and photographs as well as on some poor and still visible remnants, it appears that until their demolition the city walls retained to a large extent their late medieval form, although they had undergone significant interventions by the Ottomans, mainly on the eve, and just after the siege of 1688. The only surviving part of the city’s defences, the fort of Karababa, built on the steep hill of the Boeotian coast, can be dated to this period.

Geotourism on XIII Koto Kampar: an Approach for Sustainable Eco-Geo System

XIII Koto Kampar has become one of the potential geotourism destinations in Riau Province. The beauty of geomorphological view of XIII Koto Kampar is the main attraction for tourism. This study aims to expose the uniqueness of geological conditions that form the geomorphological of study for educational, social and economic purposes. The method used for this study is a combination of geological and geomorphological mapping and assess the inventory of geosites. Geomorphological of study area is consist of wide lake with some islands on it. Based on the elevation, geomorphology of study area devided into four which are flatland, gentle hill, steep hill and very steep hill. The result of geological mapping shown there are two dominated rock claystone and sandstone. Geotourism potential of study area classified into three main zone namely geomorphological landscape zone, water play zone and waterfall zone. Sustainable system of geotourism of XIII Koto Kampar is potential livelihood to increase the economical of local society.

Evaluating the Effectiveness of Spatially Reconfiguring Erosion Hot Spots to Reduce Stream Sediment Load in an Upland Agricultural Catchment of South Korea

Upland agricultural expansion and intensification cause soil erosion, which has a negative impact on the environment and socioeconomic factors by degrading the quality of both nutrient-rich surface soil and water. The Haean catchment is a well-known upland agricultural area in South Korea, which generates a large amount of sediment from its cropland. The transportation of nutrient-rich sediment to the stream adversely affects the water quality of the Han River watershed, which supports over twenty million people. In this paper, we suggest a spatially explicit mitigation method to reduce the amount of sediment yield to the stream of the catchment by converting soil erosion hot spots into forest. To evaluate the effectiveness of this reconfiguration, we estimated the sediment redistribution rate and assessed the soil erosion risk in the Haean catchment using the daily based Morgan–Morgan–Finney (DMMF) model. We found that dry crop fields located in the steep hill-slope suffer from severe soil erosion, and the rice paddy, orchard, and urban area, which are located in a comparatively lower and flatter area, suffer less from erosion. Although located in the steep hill-slope, the forest exhibits high sediment trapping capabilities in this model. When the erosion-prone crop lands were managed by sequentially reconfiguring their land use and land cover (LULC) to the forest from the area with the most severe erosion to the area with the least severe erosion, the result showed a strong reduction in sediment yield flowing to the stream. A change of 3% of the catchment’s crop lands of the catchment into forest reduced the sediment yield entering into the stream by approximately 10% and a change of 10% of crop lands potentially resulted in a sediment yield reduction by approximately 50%. According to these results, identifying erosion hot spots and managing them by reconfiguring their LULC is effective in reducing terrestrial sediment yield entering into the stream.

An Empty Graveyard: The Victims of the 1946 AOA DC-4 Crash, Their Final Resting Place, and Dark Tourism

In 2013, archaeologists succeeded in locating a plane crash that had been presumed buried based on local stories. The aircraft had crashed into a steep hill, subsequently known as Crash Hill. On the summit is a deteriorated memorial which resembles a cemetery, marking the thirty-nine people who died in the 1946 tragedy. This memorial has been a spot of pilgrimage for family and an attraction for adventure seekers. This draw to dark tourism sites is not uncommon but since archaeologists shared their finds with the public through social and local media, many of those visitors are drawn to the crash site instead of the memorial. This is a problem as there are possibly mass graves at the crash site, and visitation can potentially disturb those remains. This article argues for caution when discussing finds publically and for the repair and restoration of the memorial at the top of the hill to fill the want to visit a site of tragedy without disturbing the actual crash site.