A Study on Decisional Factors for Service Life of Fire Trucks

The lifetime of fire trucks depends on their built-in pumps. A fire truck delivers water to the site of a fire accident via its pump that is composed of an impeller and a casing. As its service time increases, the clearance between the two elements increases. This causes leakage in the pump to increase beyond its limit and the pump can no longer fulfill its principal role. In general, fatigue, erosion, and corrosion are considered to be the major mechanisms for pump failure. From this study, it has been observed that fatigue is not the main factor for failure because of the small magnitude of stress it induces. Erosion by particles shows a high erosion rate of the suction area of the impeller. Cavitation, which is a key mechanism of corrosion, is observed at a suction depth of 7 m and is observed to widen at 7.1 m depth. Finally, the lifetime of the fire trucks is found to be affected by the motion of sucking the natural water of ponds, rivers, etc.

Typical debris-flow barrier dams and associated outburst floods in the southeastern Tibet

<p>Large-magnitude debris flows up to a volume of 1.0 million m3 happen frequently in the southeastern margin of Tibetan plateau due to rapid rock uplift, high relief and abundant rainfall. These flows with high bulk density can easily block main rivers. Such debris-flow barrier dams fail very quickly, resulting in outburst floods and intensive sed-iment transport. We collect data of four recent large-scale debris-flow damming events at Peilong, Yigong, Tianmo and Sedongpu catch-ments, and examine the process of riverbank erosion and sediment transportation under dam narrowing and outburst flooding. More than 10% of debris mass was delivered downstream when the dams breached. It is concluded that debris flow is main erosion way in this area, and the very high erosion rate play a key role on river morpholo-gy in southeast Tibet.</p>

Soil Erosion Estimation Using RUSLE Modeling and Geospatial Tool: Case Study of Kathmandu District, Nepal

Revised Universal Soil Loss Equation (RUSLE) model is applied in this study to evaluate the risk of erosion in Kathmandu district. The calculation of erosion requires certain data from various sources available in different formats and scales. Geographic Information System (GIS) was used which allowed considerable time savings in the processing of spatial data, screening the effects of each factor affecting soil erosion. Among various erosion factors, topography, rainfall, soil properties, and soil conservation practices were used for the study. Average soil loss was calculated by multiplying these factors. Final results of soil erosion rates were separated into six classes based on erosion severity, in which 2.18% of land (> 80Mg ha-1yr-1), followed by 2.85% of land (40-80 Mg ha-1yr-1), 5.56% of land (20-40 Mg ha-1yr-1), 8.73% of land (10-20 Mg ha-1yr-1), 10.53% of land (5-10 Mg ha-1yr-1) and 70.14% of land (0-5 Mg ha-1yr-1), falls under very severe, severe, very high, moderate and low severity zone respectively. Area having high slope length (LS) factor has high erosion rate. In Dakshinkali, Nagarjun and Budanilkantha area, there is high erosion rate. From the result, spatial distribution of soil erosion across Kathmandu district, can be applied for management and controlling the erosion.

Impact of volcanic and post volcanic activity on fluvial relief

The characteristic features of the river network, the structure and functioning of the valleys affected by effusive and explosive volcanism, volcano-tectonic phenomena, gas hydrothermal activity and mud volcanism are revealed. It has been established that within flows and covers of effusives, the formation of new streams channels can occur not only due to backward erosion, but also as a result of the collapse of the roof of the near-surface lava tubes, which are actively used by underground runoff. A high erosion rate, a large volume of solid runoff, and a significant role of deflation in the transformation of the fluvial relief are characteristic for regions of domination of explosive activity. There valleys become zones of accumulation of volcanic material, which is gradually processed by mudflow, alluvial, aeolian and other processes. Volcanic-tectonic activity changes the rivers position, direction of streams and morphology of the valleys, leading to numerous reorganizations of the river network, as a result of which the valleys of modern watercourses often consist of uneven-age fragments. Valleys of hydrothermal zones are characterized by the active development of slope processes, which leads to the formation in them not only of sinter terraces, but also numerous landslide ones. Mud volcanic processes periodically lead to the filling and blocking of the valleys with mud breccia flows, which affects both the composition of the alluvium of watercourses and the morphology of the valleys.

The Impact of Land Use on Hydrological Characteristics and Erosion Rate of Cilutung Watershed with SWAT Model

Cimanuk watershed will be affected directly by the dynamics of Cilutung watershed as one of its tributaries. Cimanuk is one of the watershed areas in West Java Province, that is categorized as a critical potential due to erosion and vegetation damage. This study aims to simulate hydrological conditions and erosion rates for each sub-watershed. This research uses several variables: 1) soil type; 2) topography; 3) land use; and 4) climate (temperature, rainfall, solar radiation, wind speed, and relative humidity). Analysis conducted is Hydrology Response Units (HRUs) and statistical analysis. Variable physical characteristics are processed by the overlay method for HRUs analysis. Statistical analysis showed the values of R2 and NSE were 0.48 and 0.32. Based on the calibration and validation results, the values of R2 and NSE are 0.75 and 0.46. This shows a satisfactory and acceptable model. The runoff value tends to show a moderate category between 50-80 in the category of Coefficient of Flow Regime and this is precisely proportional to the rate of erosion. Each sub-watershed shows a high runoff value, tends to produce high erosion rate as well and its reverse. The rate of erosion indicates 175.0 tons/ha / year in the medium category.

Mapping soil erosion in the Da Dang river basin, Lam Dong province

The Da Dang river basin, located in the Upper Part of Dong Nai River, plays a crucial role to protect water resources in the downstream parts. The purpose of this study is to assess and develop a soil erosion map in the Da Dang river basin by using the Revised Universal Soil Loss Equation (RUSLE) combined with remote sensing (RS) and Geographic Information System (GIS). The factors used in the RUSLE equation (R, K, LS, C, and P) were computed by using data obtained from local meteorological stations, topographic maps, soil surveys, and satellite images. The data on water quality (TSS) of 75 surface water samples was deployed at 15 monitoring sites in the river basin in the period of 2012 – 2016, provided by DONRE of Lam Dong. The results showed that 14.41% of the basin area is subjected to a high erosion rate with an extent of 10 tons/ha/year or more. Furthermore, the study also indicated that TSS concentration has a closely correlation with land use practices and the the spatial distribution of soil erosion. These findings are essential information and practical implications for local authorities in formulating provincial planning policy for land use and the management practices of soil and water protection in the Da Dang river basin, a sensitively mountainous area, in the context of climate change.

Study of a Bionic Anti-Erosion Blade in a Double Suction Centrifugal Pump

A bionic blade with convex domes was applied in a double suction centrifugal pump to improve erosion resistance of the blade surfaces in this study. The hydraulic performance of the pump was simulated and the numerical results were in good agreement with the experiment data. The erosion rates of the smooth blade and bionic blades with convex domes at different heights (1.0 mm, 1.5 mm, 2.0 mm ) were numerically predicted. The results showed that the pump with bionic blades had a higher head and a lower efficiency than those of the pump with smooth blades. A comparison of the erosion rates indicated that the bionic blades exhibited much better erosion resistance than the smooth surface ones. The high erosion-rate area was reduced remarkably and the erosion region became more dispersed on the whole bionic blade surface. The pressure side of the blade with 2.0 mm-height convex domes showed better anti-erosion performance than those with other two heights, while the suction side with 1.0 mm-height domes showed better anti-erosion performance.

Numerical Simulation of Insulation Layer Ablation in Solid Rocket Motor Based on Fluent

A two-dimensional axisymmetric model was constructed to predict the ablation of the insulation layer in an end burning rocket motor by using the Computational Fluid Dynamics (CFD) software Fluent. The insulation material of graphite was used in the model. The wall surface reactions and discrete phase erosion were applied to simulate the insulation layer ablation. The influence of the burning surface movement was analyzed by using the dynamic mesh method. Numerical results show that the erosion rate increase with the increasing of burning time. The maximum erosion rate occurs at the upstream of the nozzle throat. There has a high erosion rate closing to the burning surface, and it decreases gradually away from the burning surface and becomes zero near the nozzle. It’s found that solid particle deposition appears on the inner surface of combustor closing to the nozzle, and it increases with the increasing of time.

Solid-Liquid Flow-Induced Erosion Prediction in Three-Dimensional Pump Casing

Solid-liquid flow-induced erosion wear prediction in a typical three-dimensional pump casing is dealt with. The two-phase flow field inside the three-dimensional pump casing is simulated using finite element modeling of mono-size particulate flow. Using this flow field and the concentration along the casing surface, wear rate is calculated using empirically determined wear coefficients. Wear rate along the three-dimensional casing surface and the location of high erosion rate are examined. Results show that the wear rate distribution is high near the cut water region (the region separating the total flow from the discharge flow). Wear is non-uniformly distributed and is high at some local spots. Even along other radial sections, wear rate varies significantly from the sides to the centerline of the casing.