The present numerical study examines hypersonic flow (Mach 5.9) over a blunt body, comparing configurations with and without a forward-facing cavity (FFC). Operating at 1200 Pa and 143 K free-stream conditions, the research focuses on critical parameters, including the drag coefficient, pressure fluctuations, and shock stand-off distance, using unsteady-state RANS simulations. The findings indicate that a forward-facing cavity reduces drag by up to 18% at an L/D ratio of 3. This improvement is attributed to an increased shock stand-off distance, which alters the flow dynamics around the body. The s-a turbulence model with three coefficient equations has satisfied the Navier-Stokes equations to simulate hypervelocity flow over a blunt body. The current time-dependent simulation has provided almost steady results after reaching 11 milliseconds. A comparative analysis of blunt bodies with and without cavities and with varying L/D ratios further demonstrates that deeper cavities enhance performance in hypervelocity conditions.

The present work provides an experimental, sustainability, and ML-based analysis of Andropogon Nardus biodiesel as a potential second-generation green fuel for compression ignition engines. The biodiesel blends (AN20, AN30, and AN40) were then used on a single-cylinder direct-injection diesel engine over the 25–100% load range and at injection pressures of 190, 210, and 230 bar. Among the three AN30 blends tested, the improvement in engine performance at 230 bar indicates that AN30 provides nearly 15% greater brake thermal efficiency and reduces brake-specific fuel consumption by as much as 31% compared to the neat diesel level. Because of good atomization and the presence of oxygen in biodiesel, significantly lower emission levels of carbon monoxide, hydrocarbons, smoke opacity, and nitrogen oxides were achieved at optimized engine conditions. To evaluate the broader sustainability potential of the fuel, we applied a multi-criteria PUGH matrix analysis of performance (high & low) and emissions (atmospheric & land use)/sustainability (high & low) indicators. Out of all the fuel tested, the most favorable compromise between combustion modes was achieved with AN30 at 230 bar, which represents the best operating condition among the fuels tested. The experimental patterns were also employed to develop machine-learning models for predicting engine responses across an entire cruising range, and the results compared the prediction accuracy with models found ensemble-based algorithms provided the best prediction accuracy of the three models evaluated. These studies demonstrate that biodiesel produced from Andropogon narudus possesses decent potential as a sustainable biofuel for use in diesel engines when mixed at appropriate ratios and injected at appropriate pressures.

Separated flow at a blunt base remains a critical topic in both automotive and aerospace engineering, particularly in the context of high-speed and supersonic vehicles such as modern fighter aircraft. In the separated region, characterized by a recirculation zone, the local pressure is typically lower than the ambient back pressure. This reduced base pressure can account for up to 70 percent of the total drag acting on an axisymmetric body. The present study focuses on regulating the base pressure within the recirculation region to reduce base drag and thereby enhance the operational range of rockets, missiles, and related aerospace vehicles. The analysis considers key inertial and geometric parameters, including a Mach number of M = 1.8, different expansion levels, an area ratio of 6.25, and duct lengths ranging from L/D = 1 to 6. A triangular rib is introduced as a passive flow-control device to modulate the pressure within the duct. In the numerical simulations, the rib base is fixed at 3 mm, while its height varies from 1 mm to 5 mm. The results indicate that increasing the rib height enhances the base pressure, with the largest height producing the greatest pressure rise. A rib height of 3 mm is sufficient to raise the base pressure close to the back pressure. For applications requiring a more substantial increase in base pressure, ribs with heights of 4 or 5 mm are recommended, depending on mission constraints. Optimal performance is achieved when the rib is positioned at L/D = 3 or 4, where the maximum pressure gain is observed.

The world is crippled by an energy crisis. Such a situation sparks innovation and transformation for emerging technology. Energy harvesting is a viable approach towards generating sustainable energy. Piezoelectric energy harvesting from runway surfaces offers a potential pathway for recovering otherwise wasted mechanical energy during aircraft landing and takeoff. In this study, a finite element model is developed to investigate the electromechanical response of PZT-5H piezoelectric material embedded beneath a runway surface. A three-dimensional coupled-field simulation is performed using the finite element method to evaluate voltage generation under applied pressure loads. The model predicts a linear relationship between applied pressure (1–4 N/m2) and output voltage, with a maximum voltage of 0.078 V obtained at 4 N/m2. A theoretical extrapolation to aircraft loading conditions is presented to assess potential scalability. The results demonstrate the sensitivity of PZT-5H under compressive loading and highlight its suitability for low-power sensing and localized energy harvesting applications. The study provides a numerical framework for future optimization and experimental validation of piezoelectric runway energy harvesting systems.

The rapid development of space transportation systems and high-speed military aircrafts have intensified interest in turbulent separated flows, particularly under transonic and supersonic conditions. Such flows commonly arise downstream of sudden expansions, where separation and subsequent reattachment generate strong shear layers, increased drag, and a low-pressure recirculation region at the base. In this study, the control of base pressure downstream of a sudden expansion is investigated numerically using a passive bullet-shaped rib. A jet issuing from a nozzle is discharged abruptly into a duct of 25 mm diameter, producing a separated flow with pronounced recirculation. Bullet-shaped ribs with length-to-diameter ratios ranging from 0.5 to 3 are placed at different axial locations, and three rib geometries are examined. The results indicate that ribs with L/D = 0.5 are largely ineffective for two of the geometries, whereas the third geometry produces a substantial increase in base pressure. For rib placements at L/D ratios of 1, 1.5, and 2, geometries corresponding to cases 1 and 2 do not significantly alter the flow, as reattachment occurs farther downstream. In contrast, the rib geometry of case 3 consistently enhances base pressure across all tested locations, with the most pronounced improvements observed when the rib is positioned at L/D = 2 and 3.

Abrupt relief increases at the blunt base are common in aerospace because a recirculation zone decreases pressure and increases drag. This study investigates the control of base pressure at Mach 1.0 by using quarter-ribs placed at various points within an axisymmetric duct. CFD simulations with ANSYS Fluent identified the optimal rib size, position, and nozzle pressure ratio (NPR) for either maximizing or minimizing base pressure. Air flows from a converging nozzle into a 16 mm diameter duct, with lengths ranging from L/D = 1 to 6, rib radii from 1 mm to 2.5 mm, and placements from L/D = 0.5 to 2.0. Results demonstrate that ribs significantly impact base pressure by interacting with the shear layer and duct wall. This interaction affects flow reattachment and pressure differences, which depend on the size and location of the ribs. Ribs at 0.5D and 1D slightly increase base pressure, while those at 1.5D and 2D are more effective. Larger rib radii enhance shear layer reattachment, further boosting pressure. Temperature analysis reveals a rise immediately behind the rib, attributed to the increased flow area, followed by a subsequent drop. These findings enable the optimization of passive control strategies in high-speed aerodynamics, thereby improving system reliability, reducing costs, increasing fuel efficiency, and supporting environmental goals.

A comprehensive Computational Fluid Dynamics (CFD) and Unified Machine Learning (ML) framework is developed to study high-speed flow regimes over a cone. The study evaluates the distributions of total pressure and total temperature along the slant length of the cone for freestream Mach numbers between 4.2 and 6 and semi-cone angles between 2° and 20° Flow properties are extracted at non-dimensional positions (x/L) across the range 0 to 1 in 0.1 increments. The CFD results show that the cone tip experiences a significant total pressure loss due to intense shock interactions, leading to downstream pressure stabilization. The total temperature shows a gradual change pattern, resulting from both viscous dissipation and boundary-layer growth, which becomes more pronounced with increasing Mach number and larger cone angles. The CFD results are validated against the Taylor-Maccoll theory. The machine learning models use Support Vector Machines (SVMs), K-Nearest Neighbors (KNN), and Ordinal Logistic Regression (OLR) to train on CFD data using k-fold cross-validation method. Later, the models' generalizability was tested on the test dataset. The analysis shows that SVM achieves the best total pressure prediction accuracy, while OLR outperforms other methods in total temperature prediction accuracy. KNN demonstrates moderate accuracy, but it struggles to apply its knowledge to new situations. The combined CFD–ML solution enables researchers to achieve their results with less computational work while delivering accurate predictions. It would serve as a powerful resource for high-speed aerodynamic research and design optimization.

The current study investigates the aerodynamic characteristics of three distinct missile nose cone geometries: sharp, blunt, and bulb-shaped under supersonic conditions at Mach numbers 2.4, 2.8, 3.2, and 3.6. The primary objective is to analyze key parameters, such as lift and drag coefficients, and compare the findings with values reported in existing literature. The research aims to explore the flow physics responsible for variations in drag force as the missile nose shape is altered. Supersonic missile design has drawn significant interest, with improving performance remaining a critical focus for researchers and engineers. One of the main challenges in achieving better performance is mitigating the high drag forces experienced at these speeds. The research employs two-dimensional computational fluid dynamics simulations using the standard k-epsilon turbulence model in ANSYS Fluent. Key parameters such as drag coefficient, lift coefficient, and pressure distribution are analyzed to understand the impact of nose shape on aerodynamic efficiency. Results indicate that the sharp nose geometry exhibits significantly reduced drag compared to the blunt and bulb configurations due to streamlined shock wave interactions and reduced pressure concentration at the nose tip. Conversely, while producing higher drag, the blunt shape offers better heat dissipation potential due to increased surface exposure. This study fills a gap in the literature by conducting a detailed comparative analysis of unconventional nose shapes at high Mach numbers. The findings contribute to improved missile nose design by balancing drag reduction and thermal management in high-speed flight regimes. The study concludes that minimizing the missile's exposed surface area to the freestream and shock interactions effectively reduces drag, as smaller surface areas diminish shock interaction and associated drag forces.

A sudden increase in the area of a duct or at the blunt base of the projectile leads to flow separation and reattachment. In the flow separation process, the base pressure at the blunt base is sub-atmospheric, leading to significant drag, which can be around sixty to seventy percent. This study is undertaken to regulate the base pressure in the recirculation zone and the flow field of the duct. This paper focuses on the effectiveness of quarter ribs of various radii in the range from 1 mm to mm and nozzle pressure ratio ranging from 3 to 11 at Mach M = 1.48 for a duct diameter of 22 mm and its sizes ranging from 1D to 6D. Some oscillations are observed for the rib location of 11 mm from the exit of the nozzle. Due to the proximity to the nozzle exit, these oscillations are observed. With a progressive shift of passive control along the more significant length, a continued rise in the pressure in the base region for rib radii in the range from 2 mm to 4 mm and an extreme increase in the base pressure is achieved for 4 mm rib radii placed at 66 mm inside the duct. Nevertheless, despite the maximum enhancement in pressure for duct size L = 4D, a negligible reduction in base pressure and ambient pressure cannot affect the flow contained by the duct for a more considerable duct length. However, using a quarter rib radii of 1mm is inadequate, and base pressure values are identical with and without rib except for the nozzle pressure ratio (NPR) = 3, where the nozzle at NPR = 3 is over-expanded. Except at NPR = 3, the nozzles are under-expanded, and the control mechanism becomes efficient, resulting in a significant base pressure increase. One can make a final decision based on the mission requirements about the radius of the rib, rib location, and level of expansion to meet the user's requirements.

The study of base pressure and its control is an important research area in the transonic speed when the flow undergoes a sudden change in area. The turbulent flow in a separated region is still a crucial area of research due to the advent of space shuttles and high-performance military aircraft, and turbulent flow in transonic and supersonic flow is a thrust area for researchers. This paper focuses on base pressure control with sudden expansion at Mach 1.3 for an area ratio of 4.84. The flow field inside the duct is controlled through a passive control in the form of quarter ribs of radii 1 mm, 2 mm, 3 mm, and 4 mm for various duct lengths in the range from L = 1D to 6D for nozzle pressure ratios in the range from 3 to 11. Results show that a 1 mm rib is not adequate, and rib radii 2 mm, 3 mm, and 4 mm are effective in raising the base pressure values, and this rise in the base pressure continues till the duct length L = 1D to 4D. There is a marginal reduction in base pressure for the duct lengths L = 5D and 6D due to the ineffectiveness of the back pressure.

The study of turbulent flow at high inertia levels remains an area of investigation with the advent of the space shuttle and the design and development of supersonic/hypersonic missiles and aircraft. When the flow gets separated, there is an abrupt rise in the relief to the flow, resulting in a low-pressure recirculation region at the blunt base of the shells, rockets, and missiles. This study aims to assess the effectiveness of passive control as a corrugated rib at Mach unity for a pipe of diameter 25 mm for a length-to-diameter ratio (L/D ratio) = 1 to 6. The study was conducted for a nozzle pressure ratio of 1.5 to 5. At sonic Mach number, when the passive control is placed at various locations in the duct, the optimum location and height of the rib seem to be L/D = 0.5,1, 2, and 5 mm, resulting in a base pressure almost three to four times the ambient pressure where the flow from the nozzle sees corrugated part of the rib which sheds secondary vortices due the presence of the sharp corners. The control is adequate for the three mm height of the rib, but the maximum gain is at L/D = 2, and for other locations of the rib, the change in the pressure at the recirculation region is insignificant. The base pressure values remain the same when the rib is further moved downstream at L/D = 3 and 4, and the rib position variation is ineffective. Hence, based on the mission's needs, one can select the size and position of the rib. Therefore, any increase in base pressure will enhance the range of missiles, rockets, aircraft bombs, and artillery shells, leading to enormous savings in fossil fuels, a reduction in carbon emissions, and a reduction in global warming.

Many Engineering applications use multi-jet systems, such as aircraft propulsion units and spacecraft. A complex aerodynamic flow field occurs when multiple jets are close to each other. This study experimentally examines the supersonic jets' mean flow field and mixing characteristics from one, two, and three different convergingdiverging nozzles placed in close vicinity. The cross-wire is used as a passive control technique to investigate the impact of the control on the flow field and the core length. The nozzle is designed for Mach number M = 1.5, with an inter-nozzle positioning equal to twofold the nozzle exit diameter. The typical contact procedure and the triple jet's growth are discussed using cross-sectional contour patterns and transverse pressure profiles. The effect of leading parallel jets on local flow field features, comprising shock wave structure, supersonic core, and jet spread, is observed by measuring pressure beside the jet axes. Similarly, the flow spread rate declines when the quantity of jet flow increases- this is mainly owed to a decrease in attuning; subsequently, the jet decays more slowly, and the core length decreases. Schlieren's pictures of triple, twin, and single jets reveal that the core of the supersonic jet varies in triple and twin jets compared to single jets.

The current investigation focuses on numerically simulating the stiffness derivative across a wedge by varying Mach numbers and wedge angles at different pivot points. The simulation of the stiffness derivative utilizes an approach based on regression model analysis. The analytical results draw upon Ghosh's two-dimensional piston theory. This research considers the Mach number, wedge angle, and pivot position as factors. This study's Mach number (M) ranges from 5.0 to 10. 0 while the wedge angle (θ) varies between 3° and 30°. The stiffness derivative findings are obtained for Mach numbers (M) and angles of incidence (θ) at several pivot positions (h) spanning from 0. 0 to 1.0. The findings of this study regarding stiffness derivatives are compared to the analytical results. There is a strong alignment between the current research results and the analytical findings. It is observed that parameters such as pivot position (h), wedge angle (θ), and Mach number (M) play a significant role in influencing the variations of the stiffness derivative. The stiffness derivative consistently increases with the angle of incidence (θ) and decreases steadily as the Mach number (M) increases at each pivot location (h).

This investigation primarily underscores the numerical modeling of damping derivative across a two-dimensional wedge at diverse pivot points, particularly for considerable Mach numbers and angles of incidence values. The damping derivative is simulated numerically via regression model analysis. Analytical results are derived by employing Ghosh's two-dimensional piston theory. This study considers factors including Mach number, wedge angle, and pivot position. The current inquiry observes that the wedge angle (θ) spans from 3° to 30°, whereas the Mach number (M) fluctuates between 5.5 and 10.0. Damping derivatives results are acquired through the examination of various Mach numbers (M) and angles of incidence (θ) at multiple pivot locations (h) ranging from 0.0 to 1.0. This research evaluates the damping derivative findings against theoretical forecasts, revealing a notable correlation between them. Research results and theoretical predictions exhibit a remarkable resemblance; however, this study demonstrates that changes in damping derivative are influenced by factors such as Mach number (M), angle of the wedge (θ), and position of the pivot (h). At every pivot position, the damping derivative magnitude diminishes with an increase in Mach number; however, it ascends with an increase in the angle of incidence. This phenomenon is noteworthy because it underscores the complex interplay between these variables (factors), although one might posit that the relationship could be more linear under certain conditions.

Fossil fuels like coal, oil, and natural gas currently dominate global energy production but release significant amounts of CO2 and other greenhouse gases, contributing to global warming and climate change. To address these environmental concerns, alternative methods of energy production and storage must be explored. This study investigates the thermal performance of latent heat thermal energy storage (LHTES) using phase-change materials (PCMs) in a horizontal cylinder. The experimental setup consists of a copper tube, 650 mm in length, with an inner diameter of 25 mm and a thickness of 2 mm, enclosed by a 600 mm acrylic tube with a diameter of 45 mm and thickness of 5 mm, and insulated to minimize heat loss. The temperature distribution was monitored along the axial direction during charging and discharging processes. These findings suggest that the proposed method can enhance the efficiency and performance of thermal energy storage systems, making them more suitable for practical applications in renewable energy storage.

The turbulent flow in a separated region is still a fundamental area of research due to the advent of space shuttles and high-performance military aircraft, and turbulent flow in transonic and supersonic flow is a thrust area for researchers. Whenever the flow experiences an abrupt increase in the area of the enlarged duct, the flow gets significant relief to separate and expand. When the shear layer comes out, it gets divided into two regions: main flow and separated flow. The divided stream line gets reattached with the duct and forms a recirculation zone where the pressure is lower than ambient pressure, resulting in significant drag. This study focuses on base pressure control through quarter-circle rib as a passive control mechanism. Accordingly, a comprehensive numerical simulation was carried out at screech-prone Mach number M = 1.6 for various radii 1 mm, 2 mm, 3 mm, and 4 mm for duct lengths in the range from L = 1D to 6D and nozzle pressure ratios from 3 to 11. Results indicate that for the same range of the rib radius, duct lengths, and level of expansion, there is a progressive increase in the base pressure when rib locations are moved downstream from 0.5D to 3D. The maximum rise in the base pressure is achieved when the rib is located at 66 mm from the base region. A rib with a radius of 1 mm is inadequate for the entire range of rib placement in the present study except when the rib is 11 mm from the base. It can be concluded that a rib of a 1.5 mm radius will be sufficient to neutralize the suction created due to the flow separation. The user can decide on the rib dimension, location, and nozzle pressure ratio based on their requirements.