Sea Level Conditions Research Articles

Implications of Climate Change on Agricultural Productivity: A Review

Global warning and thus climate change is a global issue and its consequences are being felt at varying degrees in different parts of the world. The developing countries are more vulnerable to its effects because of their poor economic status and political instability. In recent times, experiences of more flooding, erosion, drought, storms, rise in sea level and other extreme weather conditions resulting in poverty, degraded environment and low agricultural productivity. It’s devastating impact on various dimension of human endeavours and socio-economic income of nations and individual cannot be over emphasized. Climatologically, has an extremely variable rainfall distribution, which will be exacerbated by climate change. This will inevitably impact on agriculture and the availability of water to sustain human activities. These future climate change impacts are likely to aggravate the harmful effects of poor land use; practices, especially deforestation, soil degradation and water pollution. Communities that have been made vulnerable by economic hardship and disease will find it even harder to cope. Climate change is perhaps the most serious environmental threat to the fight against hunger, malnutrition, diseases and poverty in sub-Saharan Africa mainly through its impact on agricultural productivity

Hypersonic Flow Control of Kinzhal Missile via Off-Axis, Pulsed Energy Deposition

The interaction of an off-axis, spherical energy discharge with the Kh-47M2 Kinzhal missile at Mach 6 sea-level conditions was simulated. A parametric study of the energy discharge parameter (proportional to the ratio of the energy added to the internal energy within the energy deposition volume) was performed to examine the effect of energy added to the heated region in front of the missile and the changes it causes on the drag force, side (vertical) force, and pitching moment. The peak value for the pitching moment coefficient was shown to be 0.0045 for , which was shown to be 15.5% of the value due to a 10° front finset deflection. Both inviscid and Reynolds-averaged Navier–Stokes simulations were performed. The additional influence of the turbulent boundary layer on the peak value of the produced pitching moment was negligible. The time interval for the variation in the pitching moment coefficient due to energy deposition is 61 times faster than the standard actuation time (0.1 s) for conventional control surfaces, indicating the potential for multiple pulsed energy depositions as a means for hypersonic flight control.

Was Aboriginal population recovery delayed after the Last Glacial Maximum? A synthesis of a terminal Pleistocene deposit from the Sydney Basin, New South Wales, Australia

We present a synthesis of 14 compliance-based investigations of an archaeologically significant sand body on the banks of the Parramatta River. We find the alluvial deposit initially formed ∼ 50,000 years ago (50 ka), but with extensive portions reworked between ∼ 20–5 ka. There is limited evidence of past visitation, with only three excavations having recovered substantive material culture (i.e. > 20 lithics/m2 across small areas, ≤35 m2). Following equivocal evidence of visitation prior to the Last Glacial Maximum (LGM), these assemblages generally demonstrate: i) widespread ephemeral, but repeated, activity between ∼ 14–6 ka, dominated by indurated mudstone/tuff/chert raw materials (IMTC) and expedient technologies, overprinted by; ii) more extensive occupation of the landscape in the last few thousand years, with increasingly diverse and complex stone assemblages using heat-treated silcrete and additional raw materials from multiple geological sources. Notably, these two different phases are often found in the same locale, potentially suggesting a long continuity and repeated land use over 14,000 years. This synthesis demonstrates expansion away from cryptic refuges occupied during the LGM along the Hawkesbury-Nepean River corridor (some 40 km west of Parramatta) only occurred several thousand years after the height of this major climatic disruption. This timing is suggestive of a delayed recovery from the LGM and is coincident with changing environmental and sea-level conditions, which may have influenced, or been exploited by, people in the past. Our knowledge of Aboriginal societies during the terminal Pleistocene/early Holocene transition remains poorly understood in southeast Australia and is crucial to understanding demographic, symbolic and technological changes seen later in the Holocene.

Quantifying the Impacts of Storm Surge, Sea Level Rise, and Potential Reduction and Changes in Wetlands in Coastal Areas of the Chesapeake Bay Region

Along the North Atlantic coasts of the United States, sea levels are rising at higher rates than the global average. Additionally, sea level rise (SLR) can cause reduction and redistribution of wetlands across the low-lying coastal landscape. This study applied a coupled storm surge and waves model to the Chesapeake Bay regions that are prone to SLR. Two historical storms of low and high wind intensity were simulated for current and potential future sea-level and land cover conditions. The future scenarios incorporated projections of local SLR and land use due to potential reduction and changes in coastal wetlands. Simulated flood depths were used in depth–damage functions to estimate prospective property damages, and were combined with population density information to estimate potential number of people at risk. The results showed that, depending on storm intensity, the total flooded area can increase from the baseline by 1.3–2.3 times in the minimum SLR scenario, and by 2.1–4.7 times in the maximum SLR scenario. The maximum SLR was estimated to cause approximately $5.8 billion to $8.6 billion in additional damages and potentially to affect 1–1.2 million people more than the number affected in current conditions. Results also suggest that the low-intensity storm was projected to have greater impacts in the future than the high-intensity storm today, indicating that even relatively weak storms may cause considerable damage to coastal communities in a future with SLR. Finally, flooding, property damage, and the number of people affected in the future scenarios were exacerbated by wetlands reduction and change—in other words, the protective services currently provided by natural lands in coastal areas can be diminished in the future with SLR.

The Formation of Late Pleistocene and Holocene Sand Dunes on Kikaijima Island, Nansei Islands

Coastal sand dunes dating to the latter part of the late Pleistocene were constructed at substantially lower sea levels on Kikaijima Island. They are preserved because of large-magnitude uplifts ascertained from occurrences of outstanding late Pleistocene and Holocene coral terraces. In addition, because Holocene sand dunes occur close to those of Marine Oxygen Isotope Stage 3 (MIS 3), the island is ideal for examining the environments of the formation of sand dunes, which were constructed under different climatic and sea-level conditions. Distributional and depositional features of sand dunes are clarified, and their chronology is constructed on the basis of tephrochronology, 14C dating, and chronological relationships of the sand dunes with marine terraces of known age. The environments of sand-dune formation on Kikaijima are examined in relation to climatic and sea-level records within regional and global contexts. Nine tephra layers are recognized. These include two widespread tephras, Kikai-Akahoya tephra (K-Ah) and Aira-Tn tephra (AT). The other seven tephras, consisting of fine ash layers, are newly recognized and named Kikaijima-1 tephra (Kj-1) to Kikaijima-7 tephra (Kj-7), of which the upper six, lying between K-Ah and AT, are aged from 13,000 to 30,000 cal BP. Holocene sand dunes began to form at c. 8,000 cal BP before the culmination of maximum Holocene sea-level rise. This is earlier than dune formation on other coasts of the Japanese Islands, where formation was generally after the culmination of maximum Holocene sea-level rise. The earlier formation on Kikaijima Island is probably due to coastal emergence caused by the conspicuous uplifts of Kikaijima and the high production of calcareous beach sands sourced from coral and foraminiferal and other materials. Late Pleistocene sand dunes, predominantly distributed at the southwestern part of Kikaijima Island, were formed in MIS 3. These dunes consist of longitudinal and parallel dunes. The largest longitudinal dunes on the lowest MIS 3 terraces, at the northern area of the southwestern part of Kikaijima Island, were formed in late MIS 3, c. 40 to 32 ka, while small and parallel sand dunes on the upper MIS 3 terraces were formed in early MIS 3. The occurrence and chronology of the Holocene and late Pleistocene sand dunes suggest that their formation on Kikaijima Island is mainly related to the occurrence of coastal sandy beaches during sea-level high stands. Although Holocene sand dunes are related to Holocene high stand, those of MIS 3 are related to high stands during cycles of sea-level fluctuations in MIS 3. The longitudinal landform of the sand dunes recognized in the late MIS 3 suggests that the prevailing winds in MIS 3 were stronger than in the Holocene. This study provides critical data for constructing a chronological framework that integrates various aspects of palaeoenvironments, as well as human interactions and responses in southern Kyushu.

Modeling water crossings leading to the arrival of early Homo in Sulawesi, Indonesia, via paleoclimate drift experiments

Lithic tools found at Talepu, Sulawesi, in Wallacea suggest that an unknown hominin occupied Sulawesi between ∼ 118–194 ka. The Philippines, Borneo, and Flores are identified as possible sources of the colonizing hominin. Climatic reconstructions indicate that the period between ∼ 118–194 ka was marked by large variation in sea level in Wallacea, with portions of the Sunda shelf exposed at low sea level but with coastlines and land extent comparable to that of the present day at high sea level stages. A series of simulated 30-day oceanic drift experiments are conducted to determine which of the three proposed regions would be the most likely origin for hominin dispersal to Sulawesi. Drifts are simulated for low and high sea level cases. Present day sea level, winds and currents from atmosphere and ocean reanalysis products are used as proxy of environmental conditions during high sea level states. Output from Last Glacial Maximum (∼21 ka) simulations generated by three paleoclimate models is used to reconstruct the environment during low sea level conditions. Simulated drifters are released from multiple locations within three possible source regions: Borneo, Mindanao (Philippines) and the Banda Arc (including Flores). Probabilities of success and trip durations of direct arrivals as well as island-hops to Sulawesi are calculated. Results indicate that crossings are facilitated by low sea level, but the possibility of crossings at high sea level cannot be discarded. All of the three analyzed departure areas could be considered feasible sources for arrivals at Sulawesi but, Borneo is by far the most likely source area and Mindanao departures more likely to arrive in Sulawesi than those from the Banda Arc. The shortest simulated period voyagers would have to survive at sea are 3–8 days, 14–19 days and 12–20 days for Borneo, Mindanao and Band Arc departures respectively. These results have implications for the trajectory of hominin evolution in the region, including inputs to modern human diversity.

Reinterpreting the Bruun Rule in the Context of Equilibrium Shoreline Models

Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models.

The influence of paleoclimate and a marine transgression event on organic matter accumulation in lacustrine black shales from the Late Cretaceous, southern Songliao Basin, Northeast China

Lacustrine black shales are widely developed within the Late Cretaceous Nenjiang Formation (k2n) of the Songliao Basin. These black shales provide an ideal natural laboratory for reconstructing the paleoclimate and paleoenvironment during the Late Cretaceous in Northeast China and have great significance in the exploration for potential oil and gas resources. According to the systematic analysis of organic carbon isotopes, elemental geochemistry and clay mineral composition, the organic matter (OM) source, paleoenvironment, paleoclimate, paleoproductivity and marine transgression event of the Nen 1 member (k2n1) were investigated, and the influence of the paleoclimate and marine transgression event on OM accumulation in lacustrine black shales was revealed. Black shales in the lower unit are characterized by a high OM abundance (max. 4.19 wt%, avg. 3.02 wt%), I-II1 kerogen (with abundant lamalginite) and low maturity. The element ratios (Fe/Mn, Mg/Ca and Sr/Cu), paleoweathering indexes (CIA and PIA), δ13Corg values and clay mineral composition together indicate a warm paleoclimate in the Late Cretaceous. The humid paleoclimate promoted the flourishing of lacustrine microalgae and surrounding terrestrial vascular plants and enhanced the lake level, conducive to favorable sources and preservation conditions for OM accumulation. Based on paleontological and radioisotope dating, the global paleotemperature rise in the Late Santonian stage probably led to the marine transgression event. It can be explained by the high lake level and sea-level conditions under the global humid climate background that resulted in the Songliao paleolake connecting with the paleo-Pacific Ocean. Alkaline and saline seawater incursion into the paleolake increased the salinity of the lacustrine water column and further aggravated the anoxic conditions of the lake, and abundant marine nutrient inputs promoted the primary bioproductivity and contributed to the accumulation of OM. The discovery of the OM accumulation mechanism under the influence of the warm-humid paleoclimate and intermittent marine transgression will add critical geological constraints on further studies of geological events in the deposition of late Cretaceous black shale.

Analysis for design optimization of high thrust liquid engine hot test facility

A high thrust liquid oxygen-kerosene fuelled engine is being developed for future launch vehicle applications. Comprehensive hot testing of engine at sea level conditions is required for qualification and acceptance of flight engine and launch vehicle stage. The engine and stage will be tested in a specialized rocket engine and stage hot test facility which deflects the flame safely to avoid any hazard to engine and adjoining mechanical structures. The facility is equipped with water jets to sufficiently cool the rocket plume before impinging on deflector pit walls. The high temperature and high-pressure rocket exhaust jet is cooled with sufficient quantity of water to maintain the impingement wall temperature within safe working limits.In this study, a multi-phase computational fluid dynamics (CFD) methodology is developed for design of water-cooling jet configuration of deflector facility. Multi-phase model validation study using full phase treatment and droplet assumption for water injection is performed prior to water jet optimization analysis of high thrust LOX-kerosene test facility. Validation studies based on simulation and analysis of existing test stand is developed. A discrete particle (DPM) based two phase methodology is chosen to model water injection in RANS framework. The optimum cooling configuration is determined iteratively through numerous multi-phase simulations. The multi-phase analysis showed ineffectiveness of initial water injection scheme which results in facility wall temperature above safe limit. A multi-plane water injection scheme is devised there on with provision of water injection at two axial locations from the nozzle exit. A detailed parametric multi-phase analysis is carried out for design optimization of multi-plane water injection scheme and to determine thermal condition of the test facility. Analysis showed effective rocket plume cooling and lower facility wall temperature with two plane water injection schemes in comparison to initial single plane design configuration. The study highlights the role of CFD based methodology to formulate an engineering solution for design optimization of LOX-kerosene engine hot test facility.

Control of coal-bearing claystone composition by sea level and redox conditions: An example from the Upper Paleozoic of the Datong Basin, North China

In order to investigate the genesis of different types of claystones and facies-related variations in clay mineralogy, a mineralogical and geochemical investigation of the coal-bearing Upper Carboniferous Taiyuan Formation of North China was undertaken in the Wangping and Xiaoyu mines of the SE Datong Basin. This formation contains both kaolinitic and mixed-layer illite/smectite (I/S) claystones having distinctly different compositions. The former is composed of kaolinite with minor illite, quartz, calcite, and boehmite, whereas the latter consists mainly of R1 and R3 mixed-layer I/S clay and kaolinite with minor illite, siderite, quartz, dolomite, and anatase. The two types of claystone formed from the same parent materials, as shown by Al2O3/TiO2 ratios and rare earth element (REE) patterns. Paleosalinity indices (B/Ga and Sr/Ba) and redox proxies (Mo and U enrichment factors and Corg/P ratios) indicate that the kaolinitic claystones formed under freshwater, oxic-anoxic conditions, whereas the I/S claystones formed under brackish, oxic-suboxic conditions. Chemical index of alteration (CIA) values show that the kaolinitic claystones experienced more intense leaching than the I/S claystones, even though both formed in a warm and humid climate, and this result is consistent with late Carboniferous-early Permian global climate and weathering intensity. The kaolinite developed through recrystallization and alteration of terrigenous clastics and an aluminosilicate colloidal solution in a reducing, freshwater peaty swamp environment. The formation of smectite was linked to marine transgressions that altered the salinity and oxygen content of sedimentary porewaters, with subsequent deep-burial conversion of smectite to mixed-layer I/S. The frequent changes in salinity and redox conditions that caused mineralogical variations in Taiyuan Formation claystones were driven by glacio-eustatic fluctuations of the Late Paleozoic Ice Age (LPIA), which led to episodic marine incursions into the Datong Basin.

IDENTIFYING THE EFFECT OF TIDES ON GROUNDWATER LEVEL FLUCTUATIONS ON GILI KETAPANG ISLAND, INDONESIA

This research aims to identify the effect of tides on groundwater level fluctuation in Gili Ketapang Island by using a combination of field monitoring and hydrodynamic modeling. Groundwater data were collected from 5 July to 17 August 2018 from two wells monitoring, while the hydrodynamic model was adopted to identify sea-level conditions. The result explains the sea level around the island is similar among extremely strong correlations between the points. The hydrodynamic model proves a standing wave due to tidal amplification in Madura Strait waters. The effect of tides on the groundwater level characterized by decreasing in amplitudes and time lags as increasing the distance from the coast.

Coastal Flooding in the Maldives Induced by Mean Sea-Level Rise and Wind-Waves: From Global to Local Coastal Modelling

The Maldives, with one of the lowest average land elevations above present-day mean sea level, is among the world regions that will be the most impacted by mean sea-level rise and marine extreme events induced by climate change. Yet, the lack of regional and local information on marine drivers is a major drawback that coastal decision-makers face to anticipate the impacts of climate change along the Maldivian coastlines. In this study we focus on wind-waves, the main driver of extremes causing coastal flooding in the region. We dynamically downscale large-scale fields from global wave models, providing a valuable source of climate information along the coastlines with spatial resolution down to 500 m. This dataset serves to characterise the wave climate around the Maldives, with applications in regional development and land reclamation, and is also an essential input for local flood hazard modelling. We illustrate this with a case study of HA Hoarafushi, an atoll island where local topo-bathymetry is available. This island is exposed to the highest incoming waves in the archipelago and recently saw development of an airport island on its reef via land reclamation. Regional waves are propagated toward the shoreline using a phase-resolving model and coastal inundation is simulated under different mean sea-level rise conditions of up to 1 m above present-day mean sea level. The results are represented as risk maps with different hazard levels gathering inundation depth and speed, providing a clear evidence of the impacts of the sea level rise combined with extreme wave events.

Altitude Performance and Fuel Consumption Modelling of Aircraft Piston Engine Rotax 912 S/ULS

Rotax 912 spark-ignition (SI) naturally aspirated aircraft piston engine is one of the most popular prime movers for the ultra-light weight aircrafts used for short and moderate range flights. SI engines operate at stoichiometric combustion and at high altitude conditions atmospheric pressure is lower than sea level reducing mass of air intake to the engine. At these conditions engine power degrades significantly from sea level, affecting flight parameters such as range and endurance. In order to optimize these parameters, engine power modelling is of vital importance. Within the scope of this study, a thermodynamic SI engine model with performance parameters (break torque and power) and fuel consumption estimation developed in MATLAB/Simulink software. Model tuning is realised using data extracted from Rotax engine operating manual at sea level and high altitude conditions. Model inputs are set as altitude, throttle lever and engine speed. Pressure drop at the intake port is modelled as a function of mass air flow using engine operating manual pressure data at various engine speed points. Mass air flow is determined via employing a volumetric efficiency map based on intake port pressure and engine speed inputs, calibrated using engine operating manual fuel data considering stoichiometric combustion. Compression and expansion strokes area modelled as isentropic events and combustion is modelled as constant volume heat input at top dead centre (TDC). However a combustion efficiency map based on engine speed and fuel flow is employed for the heat input in order to tune the work output of the engine and heat loss to the coolant and exhaust. Pumping loss is calculated based on friction mean effective pressure data. Introduced approach provides high accuracy performance and fuel consumption modelling based on engine operating manual data and can be used for flight parameters optimization studies.

Heterogeneous tidal marsh soil organic carbon accumulation among and within temperate estuaries in Australia

The scarcity of data on tidal marsh soil accumulation rates (SAR) and soil organic carbon accumulation rates (CAR) globally precludes a comprehensive assessment of the role of tidal marshes in climate change mitigation and adaptation. Particularly few data exist from the southern hemisphere and for Australia in particular, which contains ~24% of globally recognised tidal marsh extent. Here we estimate SAR and CAR over the last 70 years using 210Pb-based geochronologies in temperate estuarine tidal marsh ecosystems in southern Western Australia (WA). Specifically, we assessed tidal marsh ecosystems situated in two geomorphic settings (marine vs. fluvial deltas) within 10 wave-dominated, barrier estuaries. Overall, average SAR (1.1 ± 0.3 mm yr−1) and CAR (32 ± 9 g m−2 yr−1) estimates were 5-fold lower than global mean estimates. Furthermore, we showed that hotspots of soil organic carbon stocks are not indicative of current hotspots for CAR. The lack of significant differences (P > 0.05) in SAR, CAR, and excess 210Pb inventories between marine and fluvial settings can be explained by the high heterogeneity among and within estuaries throughout the region. The relative stability of recent and Holocene relative sea-levels in WA likely explains the limited CAR potential in tidal marshes under relatively stable sea-level conditions. However, further research exploring interactions among biotic and abiotic factors within estuaries is required to shed more light on the small spatial-scale variability in SAR and CAR across tidal marsh ecosystems in WA and elsewhere. This study provides baseline estimates for the inclusion of tidal marshes in national carbon inventories, identifies hotspots for the development of blue carbon projects, and supports the use of site-specific assessments opposed to regional means for estimating blue carbon resources.

Impacto del cambio climático en la salud

Climate changes evidenced by an increase in our planet's mean temperature, changes in rainfall, increased sea level and extreme weather conditions, favor air and soil contamination, ocean acidification, droughts, floods, heat waves and forest fires, which affect the health and wellbeing of exposed populations. These changes will exert negative effects on respiratory and cardiovascular systems, nutritional status, burden of infectious diseases, especially vector-borne infections, and human mental health. Moreover, environmental damages, such as loss of biodiversity, ecological collapse and deterioration of socioeconomic factors such as agricultural and fishery production, and the loss of habitable land, will impulse massive migrations. This article summarizes the impact that climate change is expected to have on respiratory, cardiovascular and infectious diseases and its repercussions on people of extreme ages. It is imperative to achieve the immediate commitment of worldwide national governments to control green-house gas emissions. The appropriate technology does exist, but political will is urgently needed to accomplish this goal.

Sea-Level Static Tests of Rocket–Ramjet Combined Cycle Engine Model

A rocket–ramjet combined cycle engine model, embedding twin rocket chambers driven with gaseous hydrogen and oxygen on the top wall side of a scramjet flowpath, was tested in its ejector-mode operation under sea-level static conditions. Gaseous hydrogen was also injected through secondary injector orifices to pressurize a ramjet combustor located downstream of the rocket chambers. Mixing between the hot rocket plume and cold airflow as well as combustion of residual fuel within the plume with the airflow caused entropy and static pressure increases in the constant-area mixing duct in the original flowpath design, resulting in a limited airflow rate. The mixing duct was redesigned to incorporate divergence from its onset to counter the pressure rise. With the diverging flowpath configuration, the airflow rate was increased by 40 percent. However, this modified flowpath geometry resulted in the formation of a low-speed area, through which the pressure rise in the ramjet combustor penetrated the mixing duct and reduced the incoming airflow rate. Without mechanical contraction near the engine exit, increasing pressure in the diverging portion of the flowpath was difficult, which in turn, resulted in poor mixing between the airflow and the rocket plume. Balancing these factors and additional mixing enhancement are required. The engine performance is then summarized.

The length of the development phases and the growing season of Nigella sativa L. along altitude gradients (the example of Dagestan)

Aim. To study of the duration life cycle and phenological phases of plants of Nigella sativa L. (variability depending on height above sea level, seed quality and climatic conditions of the year). Material and Methods. Generally accepted methods described in the relevant guidelines were used in conducting the research. Samples of Nigella sativa (black cumin) were sourced from various eco‐geographical origins: Saudi Arabia, Ethiopia, Syria, Egypt and Azerbaijan. Results. It was determined that with an increase in height above sea level of the place of growth, the life cycle of plants of N. sativa samples is prolonged and their content of palmitic acid decreases. Conclusion. The main reason for the above‐mentioned negative changes is a decrease in the average daily temperature with altitude above sea level and, as a result, a delay in the accumulation of the sum of effective temperatures necessary for the passage of certain stages of individual development and the life cycle as a whole.

Experimental study on the rocket-ejector system with a throat in the secondary stream

This study concentrated on hot-fire tests to demonstrate the flow characteristics that influenced by the throttle of the secondary stream in the rocket-ejector system. The experiment was conducted under the sea level static (SLS) condition. A small rocket used gaseous oxygen / liquid kerosene propellant as a primary stream supply system, and the high-pressure air bottles were employed as the secondary stream supply system. The equivalence ratio of the rocket, the air mass flow rate and the mixing length were varied to study the performance. The results show that there is a mass flow rate mismatch between the air flow entering through the inlet and the mass flow permitted due to aerodynamic choking. If the air mass flow rate through the throat is more, the inlet may unstart. If the air mass flow rate through the throat is less, the total pressure loss of the air due to the pseudo-shock would be caused under the effect of the suction performance. The unsuitable air mass flow rate is detrimental to RBCC engine operation in the ejector mode. With the increasing equivalence ratio of the rocket, the pressurization performance is improved accordingly, but the suction performance is obviously decreased. When the equivalence ratio is more than 1.1, the reacting shear layer would affect the suction performance.

Sediment supply dampens the erosive effects of sea-level rise on reef islands

Large uncertainty surrounds the future physical stability of low-lying coral reef islands due to a limited understanding of the geomorphic response of islands to changing environmental conditions. Physical and numerical modelling efforts have improved understanding of the modes and styles of island change in response to increasing wave and water level conditions. However, the impact of sediment supply on island morphodynamics has not been addressed and remains poorly understood. Here we present evidence from the first physical modelling experiments to explore the effect of storm-derived sediment supply on the geomorphic response of islands to changes in sea level and energetic wave conditions. Results demonstrate that a sediment supply has a substantial influence on island adjustments in response to sea-level rise, promoting the increase of the elevation of the island while dampening island migration and subaerial volume reduction. The implications of sediment supply are significant as it improves the potential of islands to offset the impacts of future flood events, increasing the future physical persistence of reef islands. Results emphasize the urgent need to incorporate the physical response of islands to both physical and ecological processes in future flood risk models.

SHOCKWAVE STUDY ON THE WINGS NACA 0012, NACA 64 - 206, AND NASA SC (2) - 0706 WITH Λ = 15O AT 0.85 MACH NUMBER

Airfoil is used as a basic form on aircraft wings. Airfoil on the wing of the aircraft is used to produce lift that will lift the fuselage into the air. Lifting force results from the difference in pressure between the upper surface and the lower surface of an aircraft wings. In high speed flights shockwave will occur at certain parts of the wing which will adversely affect the aerodynamic performance of the wing. Wing aerodynamic performance at high speeds can be improved in various ways, one of which is by giving a angle to the wing span called a swept angle. This study will use 3D CFD simulation methods using Ansys Fluent. The airfoil used are NACA 0012, NACA 64-206, and NASA SC (2) -0706 with a chord length of 1 m, AR = 5, and λ = 1 with backward swept angle Λ = 15 °. Free stream flow is air flowing with Mach Number = 0,85 at sea level and steady conditions. Based on the simulation results, shock occurs on the upper and lower surfaces for NACA 0012 with Cl = 0 due to symmetric airfoil, whereas shock occurs only on the upper surface for NACA 64-206 and NASA SC (2) - 0706 with a Cl / Cd value of 18.55 ( NACA 64-206) and 20.78 (NASA SC (2) - 0706). This simulation also provides a visual representation of Mach Number contour plots in the middle stretch (Midspan) of the wing and Cl and Cd data.