Journal Articles
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Item For rapid industrialization, a high degree of mechanisation has become inevitable, further increasing the capital investment. Mining statistics project a figure of 60 to 80% of the capital invested in a few new coal mining projects on mining machinery and around 5 to 15% on the development necessary to install the equipment. However, a mining property has a definite value only by virtue of its ability to produce profit over a span of years. The components and areas in which cost can be reduced are dealt with.(Cost reduction in mining industry: a conceptual analysis) Uma Maheshwar Rao, K.; Sridhar, S.; Suryanarayana Murthy, Ch.1989Item Implementation of tubercles on Vertical Axis Wind Turbines (VAWTs): An Aerodynamic Perspective(Elsevier Ltd, 2022) Sridhar, S.; Joseph, J.; Radhakrishnan, J.In recent days, enhancement of Vertical Axis Wind Turbines (VAWTs) by mitigating flow deteriorating effects like dynamic stalling, unsteady wake is given great importance. The following article focuses on implementing four different tubercles on the blades’ leading edge and studying its performance and flow characteristics using CFD techniques. Results indicate that the addition of tubercles generated counter-rotating vortices and delayed flow separation and helped control dynamic stalling. Between azimuth angles 70°–160°, the flow was seen to separate only along the trough regions of the blade and remained attached along the peak regions, thus providing more torque and power. In addition to the enhancements in the flow characteristics, a 28% increase in power coefficient was observed for the optimal configuration at the optimal tip speed ratio. Additionally, a 14% increase in maximum lift generated by the blade was observed. Preliminary aeroacoustics analysis revealed a 12% and 20% decrease in the noise emissions along the blade tip and mid-plane of the turbine, respectively. Hence, it can be shown that tubercles effectively control dynamic stall, reduce noise emissions, and increase the power output of VAWTs. © 2022 Elsevier LtdItem Musculoskeletal Disorder Risk in the Upper Extremities of Mobile Mining Equipment Operators Exposed to Hand-Transmitted Vibrations in Underground Metal Mines: a Case–Control Study(Springer Science and Business Media Deutschland GmbH, 2022) Sridhar, S.; Raj, M.G.; Mangalpady, M.Hand-transmitted vibration (HTV) exposure is associated with various health risks for operators of mobile mining equipment (MME). The case–control research was conducted to determine the musculoskeletal disorder (MSD) risks associated with exposure to HTVs in the exposed (case) and non-exposed (control) groups. HTV readings were measured at the interface between the hand and the steering device using the SV 105B triaxial hand accelerometer connected to the SV106 human vibration analyzer involving 40 MME operators in accordance with ISO 5349:2001 guidelines. A questionnaire survey was also carried out among both the study groups using Cornell Musculoskeletal Discomfort Questionnaire. The European Union's 2002/44/E.C. was used to assess the health risks posed to the MME operators. Twenty-eight out of the 40 MMEs were generating HTVs exceeding the stipulated daily limits of vibration, putting 70% of the operators at increased risk for developing MSDs. The case group was found to have an elevated risk of exposure with odds ratio (OR) 7.56 (95% confidence interval (CI), 1.159, 49.39) and OR 12.80 (95% CI, 2.436, 67.285) times more likely than the control group to suffer discomfort in the left shoulder and left wrist, respectively, indicating increased risk of exposure to HTV. Additionally, cases had elevated risk associated with exposure to tobacco, OR 9.35(95% CI, 1.856, 47.129) compared to those who did not use tobacco. MSDs were more prevalent in the case group compared to the control group. This observation was validated by the field investigations and the responses of MME operators to the questionnaires. © 2022, Society for Mining, Metallurgy & Exploration Inc.Item Experimental and numerical analysis of humpback whale inspired tubercles on swept wings(Emerald Publishing, 2022) Joseph, J.; A, S.; Sridhar, S.Purpose: With aims to increase the aerodynamic efficiency of aerodynamic surfaces, study on flow control over these surfaces has gained importance. With the addition of flow control devices such as synthetic jets and vortex generators, the flow characteristics can be modified over the surface and, at the same time, enhance the performance of the body. One such flow control device is the tubercle. Inspired by the humpback whale’s flippers, these leading-edge serrations have improved the aerodynamic efficiency and the lift characteristics of airfoils and wings. This paper aims to discusses in detail the flow physics associated with tubercles and their effect on swept wings. Design/methodology/approach: This study involves a series of experimental and numerical analyses that have been performed on four different wing configurations, with four different sweep angles corresponding to 0°, 10°, 20° and 30° at a low Reynolds number corresponding to Rec=100,000. Findings: Results indicate that the effect of tubercles diminishes with an increase in wing sweep. A significant performance enhancement was observed in the stall and post-stall regions. The addition of tubercles led to a smooth post-stall lift characteristic compared to the sudden loss in the lift with regular wings. Among the four different wings under observation, it was found that tubercles were most effective on the 0° configuration (no sweep), showing a 10.8% increment in maximum lift and a 38.5% increase in the average lift generated in the post-stall region. Tubercles were least effective on 30° configuration. Furthermore, with an increase in wing sweep, co-rotating vortices were distinctly observed rather than counter-rotating vortices. Originality/value: While extensive numerical and experimental studies have been performed on straight wings with tubercles, studies on the tubercle effect on swept wings at low Reynolds number are minimal and mainly experimental in nature. This study uses numerical methods to explore the complex flow physics associated with tubercles and their implementation on swept wings. This study can be used as an introductory study to implement passive flow control devices in the low Reynolds number regime. © 2022, Emerald Publishing Limited.Item Maximum Aerobic Capacity and Relative Aerobic Strain among Mobile Mine Equipment Operators in Underground Mines(Springer, 2023) Sridhar, S.; Raj, M.G.; Mangalpady, M.The maximum aerobic capacity and relative aerobic strain could be employed as indicators to establish a balance between work and individuals. Unfortunately, information about the physiological demands of mobile mine equipment operators working in underground mines is nearly nonexistent. The present research aimed to determine the maximum aerobic capacity and relative aerobic strain of the mobile mine equipment operators and assess their relationship with their age and body mass index. Forty operators involved in transporting ore, overburden, mine personnel, explosives, repair material, etc., were examined. The maximum aerobic capacity was determined indirectly using the heart rate of the operators. The mean aerobic capacity of the operators was 38.75 mL/kg/min, and the lowest mean aerobic capacity was found in LHD operators, 37.98 ± 3.93 mL/kg/min. The maximum aerobic capacity was negatively correlated with age and body mass index. Eleven out of 40 operators had relative aerobic strain exceeding 50% of the maximum aerobic capacity. The mean relative aerobic strain was 46.9 ± 5.54, and the highest mean relative aerobic strain of 49.37 ± 5.55 was found among LHD operators. The relative aerobic strain had a positive correlation with age and BMI. Knowing the operators’ maximal capacities while executing their tasks could be crucial in assessing the physiological demands of individuals working in underground mines in terms of acceptable work constraints. © 2022, The Institution of Engineers (India).Item Analyzing dynamic stall on tubercle mounted VAWT blades: A simplistic experimental approach using an oscillating rig(Elsevier Ltd, 2024) Joseph, J.; Sridhar, S.; A, S.; Radhakrishnan, J.Leading-edge tubercles, inspired by the flippers of humpback whales, are widely adopted passive flow control devices to enhance the aerodynamic performance of various lifting surfaces. This experimental study investigates the implementation of sinusoidal and triangular tubercles on H-type Vertical Axis Wind Turbine blades to analyze their effects on dynamic stall characteristics. Experimental tests were conducted using a specially designed oscillating rig to replicate blade motion at different reduced frequencies. The results reveal that tubercle blades exhibit a lower stall angle and maximum normal force compared to the baseline configuration. Moreover, the dynamic stall characteristics of tubercle blades are notably smoother, leading to reduced hysteresis losses. A variation in the tubercle amplitude-wavelength ratio further decreases hysteresis, albeit at the cost of reduced normal force generation. At the highest tested reduced frequency of 0.065, tubercles reduce hysteresis by up to 38%. Despite the reduction in normal force, tubercles effectively mitigate the effects of dynamic stall vortices, resulting in smoother stall behavior. The observed reduction in hysteresis can contribute to enhancing the turbine's lifespan and increasing power production efficiency. This experimental approach provides a cost-effective alternative to more expensive methods for studying dynamic stall characteristics. © 2024 The AuthorsItem Comprehensive Evaluation of Iron Ore Tailing and Cement Treated Lithomargic Soil for Pavement Application(Springer Science and Business Media Deutschland GmbH, 2025) Satheesh, A.; Sridhar, S.Lithomargic soil, extensively found along the coastal regions of Karnataka, India, is inherently weak with a low California Bearing Ratio (CBR) value and hence, unsuitable as a subgrade or sub-base material in a pavement. To utilize the lithomargic soil as a subgrade or sub-base material, the present study focuses on its stabilization using Iron Ore Tailing (IOT) and cement. IOT, collected from Kudremukh region, Karnataka, India, was assessed for its suitability in pavement stabilization, with proportions ranging from 10 to 50%. Lithomargic soil stabilized with optimum proportion of IOT was subsequently treated with cement, with proportions ranging from 2 to 12% and in increments of 2%. Compaction test, CBR test, Unconfined compression test and durability tests were carried out on lithomargic soil stabilized by IOT alone and both IOT and Cement. Furthermore, X-ray Diffraction, Field Emission Scanning Electron Microscope and Fourier Transform Infrared Spectroscopy analyses were carried out to understand the stabilization mechanisms. Optimal results were obtained for lithomargic soil treated with 20% IOT. The unconfined compression test revealed that the soil-IOT mix satisfied the strength requirements for a subbase material with 6% cement, whereas lithomargic soil alone required 8% cement content to meet the strength requirements. Incorporating 2% cement into the soil-IOT mix enhanced the CBR to 31%, up from 2% for lithomargic soil, satisfying subgrade requirement. All stabilized mix containing more than 2% cement met the durability requirements for 12 cycles of wet-dry and freeze-thaw. The microstructural analyses showed cementitious compounds within the soil structure, indicating the formation of hydration products along with additional hydroxyl compounds. The pavement design and analysis for high-volume roads was carried out as per IRC: 37-2018 and IITPAVE software and results indicate 28% reduction in design pavement thickness and a reduced maximum deflection value after stabilization. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.Item Comprehensive Assessment on Utilization of Iron Ore Tailing as Backfill Material in Mechanically Stabilized Earth Wall(Springer, 2025) Satheesh, A.; Sridhar, S.; Packiam, S.World is bestowed with self-sufficient magnetite and hematite iron ores. Huge volume of mining waste, namely iron ore tailings (IOT), is generated during processing of iron ore, leading to environmental concerns. At the same time, due to excessive usage and environmental regulations, there is scarcity of naturally available granular material. This paper presents the detailed laboratory study carried out to ascertain the feasibility of adopting iron ore tailings as an alternate granular backfill material in mechanically stabilized earth wall. A comprehensive study on mineralogical, physiochemical, and geotechnical characteristics was carried out on IOT procured from Lakhya dam, Chikkamagaluru district, Karnataka, India. X-ray fluorescence study indicates the presence of silica as major mineral along with hematite as major iron-bearing mineral. IOT is classified as a poorly graded sand with high friction angle value varying between 44° and 50° under loose and dense states and negligible particle breakage under compaction. The environmental risk connected with IOT was assessed through leaching studies and it was characterized as low contamination low ecological risk material. Design of mechanically stabilized earth (MSE) wall with IOT and granular soil as backfill using tie-back wedge method revealed that identical number of reinforcement layers are required when iron ore tailing or granular soil is used as backfill. Further, finite element modeling of MSE wall with IOT and river sand as backfill was carried out to compare the deformation behavior. MSE wall with IOT as backfill showed 70% reduction in horizontal facing displacement in comparison with sand backfill. © The Author(s), under exclusive licence to Indian Geotechnical Society 2024.