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Improved transportation increased the amount of fuel consumption required. Transportation in Indonesia is the largest oil-consuming sector, with a percentage of 40.1% of the total. Vehicle manufacturers are required to produce a vehicle that has a high level of fuel efficiency. This study aims to determine the aerodynamics of energy-efficient vehicle bodies based on computational fluid dynamics (CFD). This research was conducted using SolidWorks to implement the model. This study examined the variations in airflow velocity at 25, 40, 55, and 70 km/hour. It can be found that the coefficient of drag (Cd) values of the latest body designs with variations in airflow velocity were increased value. The calculation results of the coefficient of drag values were 0.149, 0.154, 0.162, and 0.162, respectively, and the average value was 0.156. In this research, we have found that the energy-saving car body can reduce the drag coefficient compared with the previous study. [ABSTRACT FROM AUTHOR]

In studying the flow and effects of airflow on an aircraft of a certain design, several simulation tool are used. Among them are wind tunnel, water tunnel, and CFD simulation. The reasons for using the test simulation tool are to save costs, time, and energy. It is because there is no need to make an aircraft under study with real dimensions and components. In this study, the Airbus A320 aircraft model was tested using a water tunnel and CFD simulations on the Ansys fluent application where it is believed that these two methods are one of two ways to determine coefficient of lift, coefficient of drag, and visualize the vortex that occurs when the aircraft is operating. The experiment was carried out using a water tunnel and numerical simulation on the Ansys fluent application with a design size of 1:185 in its original size. The test is carried out to determine the value of the coefficient of lift and coefficient of drag from the aircraft model design, from the coefficient of lift it is obtained what is the maximum angle before the stall of the aircraft. From testing using a water tunnel, the stall angle of the aircraft is found at 14° with a maximum coefficient of lift value of 1.379. In the numerical simulation using the fluent Ansys application, the stall angle of the aircraft is found at 13° with a maximum coefficient of lift value of 1.21. The value of the coefficient of drag in both tests obtained a value of about 0.2 at a variation of the angle of attack 0° and increases exponentially as the angle of attack increases. [ABSTRACT FROM AUTHOR]

This paper discusses the effect of dimpling on an elastic cylinder using computational fluid dynamics (CFD) simulation. The simulation CFD approach is used because it is low-cost. The purpose of this study is to model a cylinder that has three different cylinder surface configurations: smooth cylinder, outwardly dimpled, and inwardly dimpled on half the surface of the cylinder (front). This aims to increase the coefficient lift value of the cylinder and decrease the coefficient drag value in order to utilize it as alternative energy in the cylinder system supported by two beams. Furthermore, the numerical simulation is performed on an elastic cylinder with a velocity of 3.5 m/s and an aspect ratio (L/D) of 5.6. The time-domain responses of force coefficients and structural displacements are converted into frequency-domain responses using the Fast Fourier Transform to characterize the structure responses. The results demonstrate that the cylinder surface is very successful at improving the lift coefficient and decreasing the drag coefficient while maintaining the velocity constant. The time necessary to commence cylinder displacement varies depending on the circumstance. For an inwardly dimpled cylinder, the displacement initiation start time is 0.1 s; for a smooth and outwardly dimpled cylinder, the displacement initiation start time is 0.25 s. The highest vortex shedding frequency lift coefficient is obtained from an inwardly dimpled cylinder, followed by an outwardly dimpled cylinder, while the lowest is a smooth cylinder. While the frequency obtained due to changes in surface variation does not change significantly, which is around 15 Hz. [ABSTRACT FROM AUTHOR]

This journal discusses specifically about aircraft winglets. Numerical modelling of winglets on airplane wings using CFD is the author's main activity. The author's focus is to find out the effect of adding winglets of the wingtip fence type to the wingtips of the TBM 700 A aircraft that have not used winglets on the aerodynamic characteristics of the aircraft. The use of the winglet itself is to reduce the drag force in the form of vortex drag that occurs at the wingtip of the aircraft due to air movement from the lower area of the aircraft to the upper wing area. Simulation will be carried out using ANSYS by entering the condition of the aircraft when cruising at a speed of 128.66 m/s. Winglets without and with winglets were simulated under the same conditions using the NACA 4415 airfoil. The simulation results showed that the addition of winglets reduced the drag coefficient by 21.7%. In addition, the CL/CD ratio has increased by 6% which indicates the aircraft's ability to fly. Overall, the results of this study show that the performance of the aircraft increases with the addition of wingtip fence type winglets in the aerodynamic profile of the aircraft, which will affect the aircraft's ability and even reduce fuel consumption. [ABSTRACT FROM AUTHOR]

The primary goal of the proposed article is the numerical analysis of the Wing model with and without raked winglets. In order to highlight the significant performance and parameter variations between the designs, the investigation here analyses the parameters of wings made with and without serrated raked winglets. Here, the lift-to-drag ratio, lift coefficient, and drag coefficient were the main topics of conversation. This study's tapered wing design was based on the NACA 653-218 air foil. The geometry of the models is implemented and developed using the Solid Works programme. The main objectives of this work are to enhance flight performance by reducing the induced drag that is produced on the wings during action using ANSYS Fluent. It is found that the Serrated Raked Winglet (SRW) gives better reduction in drag and turbulence than the existing normal raked winglet without affecting its lift more at higher angle of attack. [ABSTRACT FROM AUTHOR]

This study aims to produce a design of tail-sitter UAVs. The research process is begun by determining the design requirement objective and calculating the required wing dimensions. Three candidates of wing airfoil were analyzed for their aerodynamic characteristics using XFLR 5 software. The results were selected using a decision matrix. The three candidates of fuselage design were proposed and also were analyzed for their aerodynamic characteristics using Ansys CFD software. The three fuselage candidates were selected using a decision matrix. The result of the selected wing and fuselage are then assembled and the aerodynamic characteristics are calculated. Based on the calculations, the Clark-Y was selected as the wing airfoil with a lift coefficient and lift-to-drag ratio of 0.83185 and 84.16466, respectively. The second fuselage candidate was chosen as the fuselage design with a drag coefficient value of 0.10077. Finally, at the takeoff phase, the tailsitter UAV design is able to produce lift coefficients and drag coefficients of 0.90017 and 0.11958, respectively. While at the cruise phase, the UAV tail-sitter design is able to produce lift and drag coefficients of 0.99239 and 0.09571, respectively. [ABSTRACT FROM AUTHOR]

The hydrodynamic problems could be solved by assisting the computational fluid dynamics software, paid or based on open-source software. An open-source CFD software, OpenFOAM, is currently at the forefront of solving fluid-related problems, competing with paid CFD software, such as ANSYS Fluent, FLOW-3D, Autodesk CFD, or PHONICS. This study aims to show how OpenFOAM solves one of the fundamental hydrodynamic problems: water flow around a cylindrical obstacle. OpenFOAM's ability to solve turbulence problems at a boundary is determined by observing the flow pattern behind a cylindrical obstacle based on velocity profiles and streamlines. Meanwhile, OpenFOAM's ability to generate the resistance of an obstacle to fluid flow is determined by calculating the drag coefficient based on nine variations of the Reynolds number (Re). 2D flow simulations have been built with OpenFOAM using a CFD approach. OpenFOAM solves the Navier-Stokes equation for incompressible flow by applying the Finite Volume Method. A Turbulent Large Eddy Simulation (LES) k-equation model was chosen to overcome the turbulence. The water velocity field around a fixed diameter cylinder has been calculated using OpenFOAM based on the variation of Re from Re=0.1 (laminar flow) to Re=107 (turbulent flow). The velocity profile of the water behind the cylinder has been compared with the theory and shows a good agreement between the numerical and theoretical results. The streamlines pattern has similarities to the scientific literature. Finally, the drag coefficient (CD) is calculated based on the velocity field generated from the OpenFOAM calculations. The values of CD have followed the drag coefficient diagram of the scientific literature. The comparison test shows that OpenFOAM performs well in solving the problems of water flow through a cylindrical obstacle. The open-source CFD software OpenFOAM could be used as an alternative low-cost option to support studies related to hydrodynamics, such as aerodynamic studies, bridge pier structure design, wind and water turbine studies, and offshore/onshore foundation structure design, and breakwater design. [ABSTRACT FROM AUTHOR]

A sports car is a car that has a speed above the average of a non-sports car. The maximum speed of a sports car is from 250 to 300 km/h and the time traveled from a distance of 0-100 km, ranges from 7 to 3 seconds. The power that can be issued by a sports car ranges from 150-300 HP. The resistance (drag coefficient) on sports cars is 0.25 to 0.35. This value is smaller than non-sport cars which have a value of 0.35 to 0.6. Aerodynamics is a change in the motion of an object due to air resistance when the object is traveling at high speed. Aerodynamic aspects have an important impact on the design of sports car vehicles. In addition to reducing drag, the aerodynamic aspect can serve to avoid the downforce that occurs when the car is traveling at high speed. The lift will cause the car to lift upwards. If this happens, the car will be difficult to control and risk having an accident. The purpose of this analysis is to find out how big the obstacles that occur in sports cars are. Sports cars are designed using Autodesk Inventor software and analyzed using Autodesk CFD. [ABSTRACT FROM AUTHOR]

This paper presents the problem of the body of the vehicle that was designed previously to be competing in the Shell Eco-Marathon competition. The vehicle has difficulties delivering air to the engine bay to help to maintain the temperature of the engine. Side-pods are designed using CATIA software in four different locations on the side of the vehicle, in front of the rear wheel, above the rear wheel, at the front bottom of the rear wheel and the rear top corner of the vehicle. Computational fluid dynamics (CFD) simulations were performed using ANSYS for the four designs to find which design is appropriate in terms of airflow reaching the engine bay. Out of the four designs, it was determined that the side-pod located in front of the rear wheel showed that there is airflow reaching the engine bay, and resulted in the lowest drag coefficient. [ABSTRACT FROM AUTHOR]

This paper presents numerical simulations using an open boundary algorithm with modified dynamic boundary condition (mDBC) for weakly compressible smoothed particle hydrodynamics models from particle-based code Dualsphysics. The problems of piping erosion in earth dams are aimed at studying the algorithm. The case 2D model of fluid flow past around a fixed cylinder is simulated, where various values of Reynold's numbers (Re 20 to Re 100) and different viscosity terms are considered. A constant velocity with different values of viscosity for generating various Reynold's numbers is modeled. The interaction between solid particles of the cylinder and fluid particles is concerned, the cylinder is affected by the hydrodynamics force caused by the flow of fluid particles. The solid particles of the cylinder are the observation points to obtain force and pressure due to the hydrodynamics forces. As a result of the simulation which is to show the capability to model 2D fluid flow with various Reynold's numbers. Drag coefficient, lift coefficient, and Strouhal number are compared to the previous work from literature. [ABSTRACT FROM AUTHOR]

Automobile Engineers have been trying to introduce the application of using dimples to reduce the drag of both road and air vehicles. Developments in automobile industry have led to increased fuel consumption, thereby increasing the need to reduce the fuel consumption. About 60 percentage of the total drag created due to the relative motion between vehicle and air is created at the rear end of the vehicle due to the formation of wake. The major means of drag experienced by a bluff body is the pressure or form drag. Whereas, the main cause of drag for a streamlined body is the skin friction drag which is due to the resistance offered by the friction on the vehicle skin. The present work intends to describe the variations in coefficient of drag of Ahmed body by modifying the top surface of the body using surface dimples of constant diameter 10 mm, constant dimple ratio (ratio of depth of dimple to diameter of dimple) and varying the number of dimples. To accomplish this, the Ahmed body was designed in CATIA@ and the CFD analysis was carried out using ANSYS Fluent@ solver. The drag reduces and also increases for specific patterns of dimples. The results obtained show that the minimum reduction of drag has been obtained for 1 and 5 dimples which is 2.05 percentage and a maximum reduction of drag has been obtained for 3 dimples which is 3.42 percentage. The drag increased gradually if the number of dimples increased beyond 5. The outcomes are validated with different research works in existence and significant conclusions are obtained. [ABSTRACT FROM AUTHOR]

This paper describes the evolution of the boundary layer around a cylinder and its contribution to the drag force in supersonic rarefied flows. Experiments are performed at two different Mach numbers in the MARHy wind tunnel (formerly known as SR3). Shock-wave visualizations, aerodynamic force measurements and static wall-pressure measurement are compared with the evolution of the boundary-layer thickness and the skin-friction-drag coefficient for a large range of laminar Reynolds numbers and Knudsen numbers in the slip regime. The skin-friction-drag coefficient, together with the thickness of the boundary layer measured near the stagnation point are found to scale with the rarefaction coefficient defined by Tsien [1]. [ABSTRACT FROM AUTHOR]

Accurately predicting the motion of resident space objects requires knowledge of all forces acting on these objects. Ionospheric aerodynamic forces, resulting from the interaction of charged bodies with the plasma medium, have been shown to constitute a significant increase in aerodynamic drag in many regimes of low earth orbit (LEO). Previous work on charged aerodynamics has considered only single species plasma flows, neglecting the multi-species interactions in the region of the ionosphere where O+ and H+ mix. We focus on H+ dominated higher altitude regime. The simulations are performed using a hybrid electrostatic particle in cell code (pdFoam). Distinct drag characteristics of H+ and O+ were identified, and related to the sheath structure for each of these regimes. Drag coefficients for high charge density flows with a mix of H+ and O+ were found to behave in a manner similar to a pure H+ flow, with the O+ component behaving similarly to a neutral flow. This results in a reduction in drag contributed by the Oxygen plasma in these mixed flows. Drag forces on these flows were found to be well predicted by the use of the drag prediction model in Capon et al [1] for H+ components, and equivalent neutral oxygen density for oxygen components. [ABSTRACT FROM AUTHOR]

Formula 1 is the most prestigious and competitive auto racing competition in the world. This makes the engineers on the Formula 1 team work hard to improve the quality of the car's design with the slightest changes to get the highest advantage. Therefore, sophisticated technology needs to be used by a team of engineers to produce the best design to win the race. Computational Fluid Dynamic (CFD) is a technology that is always used in Formula 1 races. CFD helps a Formula 1 engineers to predict the results of using a new design without investing a lot of money into prototyping and testing it live. The front wing of the Formula 1 car plays important role of the overall car performance. Its location as an aerodynamic element that is first exposed to the fluid becomes very important because the downforce production by the front wing will also have other impacts on other components downstream. This work tries to simulate the effect of fluid velocity on the front wing design of Formula 1 the year 2018 and 2019 cars with CFD applications. The accuracy of simulation result is tested through variations in the number of different meshes. This work also tries to analyze the impact of changes in the front wing design of Formula 1 2018 and 2019 cars by comparing the values of the lift coefficient and the friction coefficient resulting from the two types of front wing designs. Based on the results of the analysis that has been made by the author, it can be concluded that the 2019 front wing design managed to provide a greater lift force compared to the 2018 front wing by 35%, lift coefficient by 10%, drag coefficient decrease by 4%, with an increase at a drag force value of 16% on the front wing. This is because the shape of the 2018 front wing has a wing cascade that directs fluid away from the tire in order to reduce drag force. [ABSTRACT FROM AUTHOR]

Assessment of the flight dynamics of fragments is based on models created from differential equations and experimental results. The trajectory of fragments moving under the influence of air-drag and gravity force can be determined using the differential equations of the point mass trajectory model. The parameters of the fragmentation process are determined from experimental studies and finite element analysis. The kinetic energy is calculated using the point mass trajectory differential equations, where fragments move through the atmosphere losing energy to drag force. The drag force depends on the air density, the drag coefficient, the speed, and shape of the fragment. The trajectory model has been composed for determining a fragment moving under drag and gravity forces. The trajectory model has been converted into the first-order system of nonlinear ordinary differential equations and solved using the Runge-Kutta method. The numerical results are given for one selected fragment. Initially, simplified drag flow is utilized. [ABSTRACT FROM AUTHOR]

Aerodynamic research has been fueled by advancements in aircraft economy and performance, with a particular emphasis on minimizing drag and maximizing lift. Due to vortices formed at wingtips the lift-induced drag is generated which holds a substantial influence both during cruising and take-off configuration., The wingtip devices are effective approach to counteract this lift-induced drag. The current study examines the effect on lift and drag coefficient due to the curved winglets attached to wingtips. [ABSTRACT FROM AUTHOR]

Improvements in aircraft from year to year continue to be carried out in order to obtain better efficiency values and can be used. One of the parameters that can be used to determine whether or not the aerodynamic efficiency of the aircraft is the comparison between the lift coefficient and the drag coefficient. The TBM 700 aircraft is one of the trainer aircraft still in use. The TBM 700 aircraft is an aircraft that uses a NACA 4415 airfoil, where this aircraft has problems with turbulence in the wing of the aircraft. For this reason, the author wants to make improvements to the wing by adding winglets of the forward wingtip fence type to see the characteristics of the coefficient lift and coefficient drag values on the wing using CFD numerical analysis with variations in the angle of attack of 2.5°, 5°, 7.5°, 10°, and 12.5°. so that based on the results of the CFD simulation, the characteristics of the comparison of the lift coefficient and coefficient drag (cl / cd) values between the winglets without winglets and the wings with the addition of wingtip fence winglets have better values at angles of attack 5 °, 7.5 °, 10 °, and 12.5 °, which is about 3%-15% better, but at an angle of attack of 2.5 ° without additional winglets has a better value of 5%. [ABSTRACT FROM AUTHOR]

Amphibious aircraft is one the suitable transportation for the State of Indonesia, which consists of many islands where not all islands have aircraft runaway facilities. Designing an amphibious aircraft takes a long time and contradicts many aerodynamic theories. Therefore, using an existing aircraft design, a floater or pontoons will be added under it so that it can take off from the water surface. The addition of a floater can affect the aerodynamic characteristics of an airplane. One way to predict the aerodynamic characteristics of an airplane is to use Computational Fluid Dynamics (CFD) method with ANSYS software version 2021 R2. The boundary conditions used are when the aircraft with a floater (type 1) or without a floater (type 2) is in a cruise flight condition. The results of CFD found that the higher the angle of attack, the higher the aerodynamic coefficient. The lift coefficients of type 1 and type 2 models have similar slopes and graphic patterns, even close to each other. However, at the angle of attack of 20 degrees, there are differences and a significant decrease in the lift coefficient values in stall conditions. In comparison, the drag coefficient for the type 1 model is greater than the type 2 model, although it has the same pattern in the form of a parabola. The minimum drag coefficient (Cdmin) value for both models is at the angle of attack of -30 degrees. The value of the moment coefficient of the type 1 model is lower than that of the type 2 model, so adding a floater reduces the pitching moment. As a result, the type 1 model is more stable. The average difference in lift coefficient, drag coefficient, and moment coefficient, respectively, is ±3%, ±30%, and ±37%. [ABSTRACT FROM AUTHOR]

Hyperparameter optimization is an important stage in modeling using machine learning, especially using deep learning algorithm, in which there are many combinations of parameters that will be used to produce a high-accuracy model. There are various methods for hyperparameter optimization of a model architecture, ranging from simple methods, namely trial error, to the most advanced and complex method, such as genetic algorithms. This paper will explain the hyperparameter optimization using the Grid Search Cross Validation (GSVC) method which is relatively simple but quite efficient in calculation time and produces an acceptable model accuracy. The hyperparameter to be optimized are optimizer and activation function. The options for optimizer are Adam, Adamax, Nadam, Stochastic Gradient Descent (SGD), and Root Mean Squared Propagation (RMSProp). The options for activation functions are TanH, Sigmoid, Elu and Relu. The options for optimizer and activation function are combined and selected using GSCV to provide the best performance at a given network architecture. The GSCV method will be used to optimize a model for aerodynamic coefficient of an amphibious aircraft (N219A) based on test data in wind tunnels, i.e. namely CL (coefficient of lift), CD (coefficient of drag) and CM25 (coefficient of bending moment). The best combination of hyperparameters for the aerodynamic coefficient model is (Adam & Sigmoid) for CL, (Adam & Elu) for CD and (Adamax & Elu) for CM25. The results of validation using testing data produce the following RMSE (Root Mean Square Error) and R2 (R-Squared) i.e. (0.0137 & 0.9949) for CL; (0.0113 & 0.9969) for CD and (0.02096 & 0.9984) for CM25 show that the error of the prediction in CL, CD and CM25 is acceptable and the relationship between independent and dependent variables are quite strong. [ABSTRACT FROM AUTHOR]

The use of numerical simulations to obtain drag coefficient values cd for flow around a rough cylinder in the subcritical and critical Re number regions were the aim of this paper. The model of the cylinder with the trapezoidal waves on the surface was calculated. The results from simulations were compared with standard and available experimental results obtained by measuring of a rough cylinder with similar parameters of the relative roughness and flow regime. ANSYS Fluent software using the RANS SST k-ω turbulence model was chosen for the numerical simulations. This comparative study confirms the influence of the density and shape of protrusions on the value of the drag coefficient and thus on the shift of the position of the of cd drop to lower Re numbers. [ABSTRACT FROM AUTHOR]

C-wing design is one of many non-planar wings that can improve aerodynamic performance without compromising the aspect ratio of a typical aircraft. This paper presents and compares the aerodynamic characteristics of planar wings and C-wings with backward and forward swept configurations at transonic speed in terms of lift coefficient (CL), drag coefficient (CD), drag polar, and lift-to-drag ratio (CL/CD). The ONERA M6 wing was used as a benchmark in this study. The numerical analysis was conducted at a constant Mach number of 0.8395 with α ranging from 0° to 10° using the Spalart-Allmaras turbulence model. The results show that the Backward Swept C-wing (BSCW) delays the stall angle compared to the Backward Swept Wing (BSW). The Forward Swept Wing (FSW) and Forward Swept C-wing (FSCW) can operate at high α without showing signs of stalling. Furthermore, operating above the intersecting point, the C-wing configurations exhibit better drag reduction for a specific CL value compared to their respective planar counterparts. The CL/CD curves provide insight into the aerodynamic efficiency of the four wing configurations. The preliminary results indicate that both the BSCW and FSCW of this study can produce more lift and delay stalling α compared to their respective BSW and FSW counterparts. However, the CL/CD performance of both the BSCW and FSCW is comparatively lower than BSW and FSW, respectively, due to the interference of shock waves between the wing and C-winglet. This paper provides insight into the potential advantages and disadvantages of using C-wings in aircraft design. The findings of this study can inform future efforts to optimize aircraft performance by improving aerodynamic efficiency while maintaining similar levels of lift. [ABSTRACT FROM AUTHOR]

Cars have been important part of life for nearly a century. Many design iterations have been made since its emergence to improve its efficiency and extract more work. Some of the improvements include downsizing the engine, improved engine and transmission efficiency, using fluids like oil and coolant to resist phase change in extreme temperature conditions and for the aerodynamic losses like changing the vehicle shape to make it more streamline. The vehicle shape not only affects the efficiency but also the stability in using it at high speeds. The major objective of the present work is to design the various diffuser sections for a vehicle and to determine the Coefficient of drag, coefficient of lift, drag force and lift force of a vehicle through computational fluid dynamics analysis. A diffuser was added at the rear end of the vehicle and simulation studies were carried out for different diffuser angles of 0o, 6o, 9o and 12o. Lift coefficient in the downward direction should be high, which is desirable to prevent over turn at high-speed usage. The obtained data is analyzed and plotted to select the considerable diffuser section to be used to achieve the permissible lift and drag forces. [ABSTRACT FROM AUTHOR]

Vehicular exhaust emission is the most prominent cause of air pollution in India. Air pollution reduction to its minimum level is possible by switching from gasoline to electric vehicles. Since battery power consumption is a crucial aspect of a battery-electric car, lowering the aerodynamic drag force can decrease its consumption. In this study, a generic vehicle model named Ahmed body with a 35° rear slant angle was taken as a baseline model. FLUENT, a fluid flow component system of ANSYS, was used to simulate this baseline model at zero yawing angles via the k-epsilon turbulence model at velocities 20, 30, and 40 m/s. The result of the baseline model was validated from literature with a minimum difference of 0.35%. Drag reduction analysis was carried out to find the optimized model by placing an array of cylindrical vortex generators on top of the validated baseline model with diameters that varied in the range of 6mm to 12mm each at corresponding heights of 6mm to 18mm. The velocity contours and streamlines were studied to examine the wake region, and a maximum of 6.51% of drag reduction was found under investigation. Drag coefficient results of baseline and optimized model were applied to the real car under two road conditions. Flat road and 5% uphill were considered for calculating the percentage battery consumption reduction, and the best results were found as 3.97% and 2.25%, respectively. This drag reduction study in automobile engineering, especially for battery electric vehicles, can help reduce fossil fuel dependency. Thus, minimizing air pollution. [ABSTRACT FROM AUTHOR]

Robotic fish generates thrust using reactive force from the surrounding water and is highly non-linear and distributive in nature. Hence, describing the complete hydrodynamics of robotic fish motion is challenging. This necessitates data-assisted modelling that estimates the influential parameters using real-time experiments. This work proposes a novel multi-objective genetic algorithm (MOGA) approach for estimating the model parameters by fitting experimental data with the model. A non-dominated Pareto front solution of MOGA identifies the optimum solutions. A two-link, remotely operated, carangiform-inspired robotic fish is fabricated, and the experimental trials are conducted in an in-house water tank. The overall drag and moment coefficients are estimated through extensive open-loop experiments using MOGA optimization. Finally, the proposed model is validated using fresh experiments and close correlations are observed. The maximum average speed the designed prototype achieves is about 0.086 ms−1 at 50° tail oscillation magnitude and a turning radius of 0.18 m. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical experiments to determine the drag coefficient and study the flow patterns around small aircraft using the SolidWorks flow simulation CAE system. A feature of the problem being solved was the specificity of the calculation of small bodies when compared with the results of a ballistic experiment on a ballistic track. The structure of this experiment is presented in the paper. The use of launchers of various capacities made it possible to cover a wide range of subsonic velocities, highlighting three characteristic values of the flight velocity of a small-sized spherical aircraft. For these velocities, the values of the drag coefficient were determined. The conditions of the ballistic experiment were used as input data when organizing a numerical experiment in SolidWorks flow simulation. Moreover, the used parameters of the computational domain and the resulting flow patterns around a spherical body are presented. In addition, the values of the drag coefficient of this body are calculated. Comparison of the results of the ballistic and numerical experiments showed the high accuracy of modeling the considered processes in SolidWorks flow simulation. Additional verification with known data obtained for a similar problem in another software package confirms the effectiveness of the numerical experiment. [ABSTRACT FROM AUTHOR]

A micro air vehicle can be as small as 6 cm. Development is driven by military, research, and commercial purposes, with insect-sized aircraft that may be used in the future. The small aircraft allows for remote observation of hazardous environments, aerial photography, and robotics contests. The CFD simulation of fluid flow and aerodynamic performance of the dragonfly (Aeshna Cyanea) wing section was examined using FLUENT software at low Reynolds numbers (1000, 1250, and 1500) with various angles of attack (AOA) (0°, 5°, 10°). The numerical solver was based on the SIMPLE algorithm with Green-Gauss Node velocity pressure coupling. With increasing AOA, the mean lift coefficient increased while the drag coefficient decreased, resulting in improved propulsive performance. As the AOA rises, the gliding ratio increases in lockstep. The drag formation has some exciting outcomes. Because viscous effects are more significant at lower Re values, leading skin friction to be the primary contributor to drag reduction, the average drag coefficient in each case drops as the AOA increases. [ABSTRACT FROM AUTHOR]

Wind tunnels and linearized turbulence and boundary-layer models have been so far necessary to simulate and approximate the stationery lift and drag forces on (base-mounted) airfoils by means of statistically determined or approximated values of the relevant situational coefficients as the drag and lift coefficients. To improve this process, we introduce transient and exact formulae to separate these forces in advance by means of the solutions found from the fluid dynamics model of the Navier Stokes differential equations. [ABSTRACT FROM AUTHOR]

In this study, the CFD simulation of fluid flow and aerodynamic performance of the dragonfly (Aeshna Cyanea) wing section at low Reynolds numbers (500, 750, and 1000) with various angles of attack (AOA) (0°, 5°, 10°) was analyzed through FLUENT software. The numerical solver employed was based on the SIMPLE algorithm, velocity pressure coupling with the Green-Gauss Node scheme. The triangular unstructured mesh simulation was employed as per finite volume discretization and observed that the mean coefficient of lift increased as the AOA increased, while the drag coefficient decreased, resulting in an enhanced propulsive performance with increasing AOA. The gliding ratio, increases monotonically as the AOA increases. The drag formation yields some intriguing results. The average drag coefficient in each case decreases as the AOA increases, as expected, because viscous effects are more prevalent at lower Re numbers, causing skin friction to be the predominant contributor to drag reduction. [ABSTRACT FROM AUTHOR]

The effect of attaching a front splitter plate on a circular cylinder along the line of symmetry is studied via means of vortex shedding and aerodynamic loading. The objective of the current study is to understand the role of the front splitter plate with and without the back splitter plate in modifying the flow behind the circular cylinder. Computations are carried out for a fixed length of the splitter plates at a low Reynolds number (based on the cylinder diameter) of 100 using the finite volume computational approach. It is observed that attaching an upstream splitter plate doesn't modify the flow much behind the cylinder (compared to the back splitter plate of the same length) when attached alone. Although, a reduction in the values of the aerodynamic lift coefficient and the drag coefficient is observed. But, when attached in combination with a back splitter plate of the same length (termed the bi-lateral splitter plate), the wake behind the cylinder is primarily affected, and a reduced vortex shedding is observed. This study establishes the use of bi-lateral splitter plates to mitigate the aerodynamic loading on the cylinder efficiently. [ABSTRACT FROM AUTHOR]

The sunroof has become a much sought-after feature in Sports Utility Vehicles (SUVs). However, opening the sunroof of the SUV modifies the streamlined profile of the SUV and adversely affects the aerodynamics both inside and outside of the vehicle. This leads to increased drag (or air resistance) on the SUV, and can also induce flow disturbances inside the cabin. Here, it is proposed to examine the aerodynamics of an SUV modeled with the simple profile of an Ahmed body, but with an open sunroof. The primary objective of this study is to examine the velocity field of air inside the cabin, and the drag on the SUV, when its sunroof is opened. Using the CFD package-ANSYS Fluent-this work assesses the velocity contours and drag coefficient for three locations of the sunroof – above the driver, middle of the roof, and above the rear passengers. The results from this study can help the automotive industry in improving the aerodynamic designs for SUVs with sunroof. [ABSTRACT FROM AUTHOR]

A circular cylinder has been applied to the world of engineering with various geometries and is frequently placed in the stream of the fluid flow. The interaction between the flow and the cylinders causes drag, and at certain circumstances, causes lift also. The drag occurs due to the presence of pressure and friction on the cylinder surface. Therefore, in the present study, the researcher tried to investigate the flow behavior across three circular cylinders in a stagger arrangement placed in the airflow. The purpose of this study is to obtain drag reduction that occurs on the cylinder arrangement. This research was conducted numerically using Ansys Fluent® 19.1 and conducted in two-dimensional (2D) Unsteady RANS using the turbulence model of standard k-epsilon. In this study, the longitudinal distance (L/D) has four variations, i.e. L/D = 1.5; 2.0; 3.0; and 4.0 with a diameter of the cylinder (D)=25 mm. The cylinder arrangement is placed in a narrow channel with a square cross-section Wide x High x Long=300 mm x 300 mm x 600 mm, the flow Reynolds number in this study is set to be 2.4 x 104. The results showed that the distance (L/D) greatly affects the coefficient of drag of the circular cylinder in that arrangement. The smallest coefficient of drag on cylinders 1 and 2 occurs at a distance (L/D=3.0), while the smallest coefficient of drag on cylinder 3 occurs at a distance (L/D=2.0). [ABSTRACT FROM AUTHOR]

In this study, the turbulent flow over symmetrical and unsymmetrical airfoils was investigated numerically at different inlet velocities. The airfoils chosen for the simulation are symmetrical (NACA 0015) and unsymmetrical (NACA 4412), which are the most conventional four-digit and widely used airfoils. These airfoils are vastly used for various applications such as aircraft wings, wind turbine blades, etc. While both of these airfoils were subjected to the same fluid principle, it gave contradictory results in their aerodynamic behavior. In this paper, two different meshing techniques were used for the airfoils and the numerical analysis of NACA 0015 and NACA 4412 was carried out to study their aerodynamic behavior. A 2D steady-state incompressible turbulent flow is used to model the computational issue. The performance of the turbulence model is also reviewed. The lift and drag coefficients of the airfoils were numerically measured using the k − ε turbulence model. This study briefs the aerodynamic flow characteristics of both airfoils and evaluates the pressure and velocity contours, lift force and drag force. [ABSTRACT FROM AUTHOR]

When an autonomous underwater vehicle (AUV) sails beneath the water surface, the impact of various forces on the AUV's hydrodynamic performance is one of the key factors to be considered. A computational fluid dynamics (CFD) method is employed to numerically study and examine the parameters that effect hydrodynamic performance of an axisymmetric AUV travelling under water. The effects of flow on the AUV are quantified for various Reynolds numbers and submerged depths. It is assumed from past studies that the flow has a considerable impact on the AUV's lift & drag fluctuations, and the overall drag force increases with depth level and maneuvering becomes tough. This work focuses on study of flow past AUV where flow parameters like changing velocities, pressures and turbulence kinetic energies are studied. The analysis is carried out for AUV's at different angles of attack to study the required flow effects. The flow parameters like lift, drag, moment forces are evaluated to estimate the performance of the vehicle. The results obtained are in accordance with theory of aerodynamics where lift and drag forces are increasing with increase in angle of attack (AOA) from 00 to 100. The effect of aerodynamic stall is observed on further rise in AOA. Higher slope for lift coefficient is observed in comparison with that of drag coefficient. [ABSTRACT FROM AUTHOR]

In this study focuses primarily on the effect of adding needle ends on NACA 4412 airfoil and compare the result with NACA 4412 airfoil without needle ends. Theoretical analysis by using Ansys Fluent on NACA 4412 airfoil with needle ends to calculate the effects of these ends on lift and drag coefficients. Five angles of attack were taken (0°, 4.5°, 9°,13.5°, and 18°) for Reynolds number (Re = 106) based on airfoil chord length. The result shows that there is a 10% increase in the lift coefficient for modified airfoil more than standard airfoil. the drag coefficient of NACA 4412 with needle ends has value less than a standard airfoil. [ABSTRACT FROM AUTHOR]

A two-dimensional numerical wave tank (NWT) simulated the interaction between waves and a moving surface-piercing thin plate in intermediate water with a sloping beach. Navier-Stokes equations are discretized using the finite volume method in the tank model built by ANSYS FLUENT software. We'll employ the inflow velocity approach to create the nonlinear wave, which uses five different wave steepness conditions in the testing. The researchers investigated wave-structure interaction around a moving plate. It is essential to examine the efficiency of plate wave energy converters for various relative opening ratios. This paper's primary focus is on how the drag coefficient changes as the wave steepness changes. It demonstrates that when wave steepness increases, the drag coefficient improves. A wave energy converter (WEC) is directly implemented to harvest ocean wave energy as a renewable energy source. Wave steepness and second-order stokes wave theory on an intermediate-water moving thin plate are new topics for discussion. This study gives a new idea to the researchers for developing different types of WEC in the surge direction. [ABSTRACT FROM AUTHOR]

Combining several high lift devices on airplanes is a natural thing. High lift devices are used to control aircraft movements and improve aerodynamic performance. The landing phase in flight is vulnerable and requires good control, especially aircraft wing control that uses high lift devices. High lift devices such as slat clearance and flap are commonly used, but variations in their geometry always produce different and interesting phenomena to be explored further. This research was conducted numerically on a rectangular wing with NACA 43018 airfoil. This study will compare the rectangular wing with a wing that uses a combination of slat slots (slat clearance) and flaps on the landing process. The angle of attack used in this study is (α) = 0°, 2°, 4°, 6°, 8°, 10°,12°,15°, 16°,17°,19°, and 20°. Ansys 18.1 software with k-ε Realizable turbulent model is used to help the numerical simulation. The combination of slat clearance and flap results in a higher total drag coefficient and higher lift coefficient. However, the rectangular wing produces better aerodynamic performance. Visualizing the velocity path line and wall shear stress shows that the rectangular wing is easier to separate than the combined flap δT = 30° and slat δL = 0°. [ABSTRACT FROM AUTHOR]

Ocean Bottom Unit (OBU) is part of the tsunami buoy system located on the ocean floor. The OBU will be released from the transport vessels carrying the bouy tsunami system. The OBU prototype must withstand various conditions when it is gliding from a transport ship so that it can land perfectly and withstand strong ocean currents on the sea bottom. A method to study gliding performance of the OBU is Computational Fluid Dynamics (CFD). This study aims to find out which type of OBU model can provide large drag coefficients and small moment coefficients. There are 2 OBU models to be simulated, namely the finless OBU model (type 2) and the fin OBU model (type 1) with variations in flow speed. The simulation results show that the thickness of the base plate and fins makes the coefficient greater than the OBU type 2 model. In addition, the increase of the thickness of the base plate and fins makes the OBU type 1 model less stable when exposed to crossflow compared to the OBU model type 2. [ABSTRACT FROM AUTHOR]

Wind energy is one of the most important types of green energy with both water and solar energy. These types can be actual alternatives to fossil fuels, as wind energy is one of the energies that can only be easily obtained and used appropriately. Vertical-axis wind turbines (VAWTs) are probably very suitable in places where wind speeds are fairly low, and in order to get the best performance before the actual design, we have to do analysis, examination and simulation that will help us as an important step towards the best design of the turbine. Through this study, a comparison is made between (NACAOOO8 and NACA0021) and it is shown that the thickness of the airfoil has an important role in making (NACA0021) the best design for vertical axis turbine blades by using Qblade, where the first phase of two-dimensional simulation is to study aerodynamic properties on each section of the blade and calculate parameters such as the lift coefficient (Cl) and the drag coefficient (Cd). Then the second stage is the use of the (DMS) approach, in which the three-dimensional simulation of (VAWT) is to calculate several parameters. Most notably the power coefficient (Cl), tip speed ratio (TSR) and torque (T), the dimensions of the vertical-axis turbine from blade height, rotor diameter and chord length have an impact on turbine performance at low wind speeds, and increasing the number of blades leads to increased torque. In order to do so the turbine design must be taken into account so that it is solidity suitable for load resistance. [ABSTRACT FROM AUTHOR]

Aerodynamic drag is influenced by the geometry of the front, windshield, roof, and rear of the vehicle. Most of the drag on the vehicle is due to the low pressure and flow separation at the rear of the vehicle. Therefore, one of the efforts that can be made to reduce aerodynamic drag is changing the shape of the vehicle model, especially at the rear window tilt angle. This study aims to analyze the effect of changing the shape of the rear window on the aerodynamic drag of the sedan vehicle model. The object of this research is a sedan vehicle model with a front window tilt of 25°. The research was carried out using two approaches, namely a computational approach using a computational fluid dynamics program and an experimental approach using a subsonic wind tunnel. The rear window tilt angle of the sedan model is set at an angle of 20°, 23°, 25°, 27°, and 30°, and the upstream speed was set at 19.4 m/s. The results showed that the change in the shape of the rear window has an effect on the flow separation and turbulence developed at the rear of the sedan vehicle model. It also affects the pressure coefficient and aerodynamic drag. The smallest aerodynamic drag coefficient is obtained at the rear-window tilt angle of 20°, gaining 0.691 for the computational approach, and 0.665 for the experimental approach. [ABSTRACT FROM AUTHOR]

The blade profile of the Darrieus Vertical Axis Wind Turbine is very influential against the drag force and lift force, and power output. This research aimed to determine the maximum turbine power performance of Darrieus VAWT using the blade profile NACA 2412 airfoil with a camber radius and thickness of 50%. The 2D profile of the turbine blade was created based on web applications airfoiltools.com with specific chord lengths, radius 137.5 mm, and 50% thickness, then converted to AutoCAD. At the same time, 3D Geometry was created by using Solidworks software. The magnitude of drag coefficient, lift coefficient, drag force, and torque was analyzed using CFD Flow Simulation and experiment. Drag force was also calculated analytically and validated with software and experiment. From the simulation and experiment results showed that the torque and power output were obtained at 30°, 120°, 210°, and 300° azimuth angle with the maximum Cp of 0.46. [ABSTRACT FROM AUTHOR]

The aerodynamic aspect of a vehicle is related to the emergence of drag on the vehicle. Aerodynamic drag arises due to the low pressure and flow separation that occurs at the rear of the car. This affects the amount of fuel consumption used by vehicles. The earlier the emergence of the flow separation, the larger the wake area will be and cause a decrease in pressure at the rear of vehicles. Therefore, efforts are needed to reduce the aerodynamic drag on the vehicle so that it can delay the flow separation and increase the pressure at the rear of the vehicle by implementing flow control. This study aims to analyze the effect of passive control in the form of fin and active control in the form of suction on the flow characteristics, pressure field, and aerodynamic drag of the vehicle model. The test model used is Ahmed's body modified in flow direction with a slant front geometry of 25°. The research was carried out with two approaches: a computational approach by using the Computational Fluid Dynamics (CFD) program ANSYS Fluent 6.3.26, and an experimental approach by using a subsonic wind tunnel. The upstream flow speed is 22.2 m/s and the suction speed is 0.5 m/s, 1.0 m/s, and 1.5 m/s. The results show that the addition of passive fin control and active suction control could delay flow separation, reduce turbulence, and increase pressure at the rear of the test model. The largest increase in the minimum pressure coefficient value is 56.66% and the largest aerodynamic drag coefficient reduction is 16.902% for the computational approach and 17.757% for the experimental approach which occurs at a suction speed of 0.5 m/s. [ABSTRACT FROM AUTHOR]

In the Russian Federation, 80% of agricultural land is in unstable moisture. The economic crisis at the end of the last century affected the state of reclamation hydraulic structures. The large-scale reconstruction and construction of reclamation systems planned until 2030 requires the development of new media for them. The use of renewable energy sources to control water supply is at the heart of injection flow controllers. The structure is an alternative to automatic gates of electromechanical actions and uses the hydrodynamic properties of the flow for its operation. The previously obtained theoretical relationships for the hydraulic calculation of the regulator considered the structure as a kind of injector located under the dam or embankment. To further optimize the shape of the flow path of the regulators, an analysis of the modern improvement of water-jet pumps was carried out, taking into account the operation of the regulator as a hydraulic structure. The improved design model was tested in the hydraulic laboratory, its hydraulic characteristics were obtained experimentally, and the estimated random errors of direct and indirect measurements were obtained. The limiting position of the boundary streamline before the mixing chamber is obtained theoretically. For the first time, the drag coefficient of a rectangular asymmetric diffuser with a large expansion angle and shortened dividing walls has been experimentally obtained. For a smooth dissolution of the flow, the leading edges of the dividing walls are placed outside the inlet section of the diffuser. Variants of the diffuser operation in the network and when the flow enters the tailwater volume are considered. The change in the flow path elements, made in accordance with the recommendations for the design of injection devices, makes it possible to increase the volume of the circulating flow, representing the excess water supply that develops in the downstream when the sprinklers are turned off. After the modernization, the range of pressures on the structure has significantly increased. This opened up new possibilities for its application. Studies have shown that further improvement of the form of execution of the flow path without introducing a rigid nozzle in the final pressure head part of the water outlet. The confluence of flows, in which the injected flow in the initial section is similar to a streamlined body, is not capable of optimal ratios of the areas of the nozzle and the mixing chamber, which affect the efficiency of the injectors. [ABSTRACT FROM AUTHOR]

This paper presents the CFD analysis for a Supercritical Airfoil with a slotted flap. The analysis has been carried out for the Flight segments-Takeoff, Cruise & Landing. The elements were Modelled in CATIA V5 R20 and then analyzed in ANSYS fluent to obtain the lift and drag Coefficients, the results were then compared with a Cambered Airfoil of similar configuration analyzed separately. For the flight segments Takeoff & Landing, the airflow is considered to be subsonic and for the flight segment Cruise the airflow is considered as transonic as to study the Critical Mach Number and the behavior of transonic buffet around the airfoil. The contours for transonic regime were then compared with Cambered Airfoil to validate the efficiency of Supercritical Airfoil and to observe the location of Shock waves formed at Critical Mach Number for both Supercritical Airfoil and Cambered Airfoil configurations respectively. [ABSTRACT FROM AUTHOR]

Design optimization of car outer body is to bring best design solution to the real time application in order to achieve the efficiency, efficacy, strength, reliability and utilization. Growing advancements in automotive industry faced a problem to reduce fuel need without compromising an existing efficiency is a real challenge. Drag is the kind of pressure that forms behind the vehicle while the vehicle attains certain speed. It creates some space that attracts atmospheric air towards in it. This faster occupation of air pulls the vehicle backward which directly affects the vehicle fuel need. Drag coefficient and lift coefficient are the main factors to affect the movement of a car and its fuel standard. In order to reduce this drag and lift coefficient, designers pay much attention to study a vehicle structure that influencing drag and also focus on aero control add-on device like, under body diffusers which has major impact on fuel consumption, aero acoustics and steadiness of vehicles. Diffusers are the widely perform and most effective aerodynamic add-ons used both in competitive racing and passenger car vehicles that can be designed to increase the downforce and diffuse the high velocity air without generating much turbulence at the back end of the vehicle. The less turbulence formation allows the smooth flow at the back end which reduces negative pressure formation. The factors generating drag and detailed flow structure for various diffuser models were studied and proposed an effective way of reducing the drag in passenger vehicle using better aerodynamic diffuser model which helps to achieve higher mileage standards of car. [ABSTRACT FROM AUTHOR]

This study investigates the potential of multiple winglets mounted on a transonic wing. The investigation evaluates the reduction of drag coefficient due to presence of multiple winglets on the basic wing model. Numerical Experiments were adopted for these investigations. The commercial CFD solver ANSYS Fluent was used to perform the aerodynamic investigation. Four different models were evaluated based on the configuration. The first model is a non-winglet model, i.e., the base model. The remaining three models were the wings with the multiple winglets, i.e., 60-Winglet model, 75-Winglet model and 90-Winglet model. The differences in the model were based on the cant angle of the winglet. 3D RANS equation along with one equation Spalart-Almaras turbulence model was used for solving the flow past the wing models. The chord wise pressure distribution, pressure variation over the entire wing, coefficient of lift, coefficient of drag, lift to drag ratio were compared for all the cases. [ABSTRACT FROM AUTHOR]

Lower ballistic coefficient offers an optimal re-entry, where the vehicle decelerates higher up in the atmosphere thereby decreasing the imposed aerothermal loads. The current numerical study investigates the effects of an add-on duct to the re-entry vehicle. The add-on duct shall circumvent the vehicle from the shoulder to the base. The add-on duct is expected to improve aerocapture ability of the re-entry vehicle. The drag and ballistic coefficient of the ducted re-entry vehicle will be evaluated and compared with the baseline model. Apart from this, the effect of the distance of the duct from the body will also be investigated. In addition to this the variation of drag and ballistic coefficient due to the change in speed regime will also be investigated. All the investigations will be performed using the CFD solver Fluent. The results reveal that the position-1 has the highest drag when the duct-position is at position-1. When the body is tested at Mach 3, the drag coefficient increased for all the positions. The position-2 showcased the highest drag coefficient for the model. The model tested at Mach 5 revealed that the position-2 of the duct has the highest drag coefficient. [ABSTRACT FROM AUTHOR]

The demand for a high-speed car is increasing in which vehicle stability and fuel economy are a primary concern. The vehicle's aerodynamics play a crucial role as they influence the overall performance of the vehicles. The study of car aerodynamics involves the study of various forces that are acting on a car while it is moving on the road, i.e., drag force, lift force. The leading cause of aerodynamic drag for automotive vehicles is the flow separation at the rear end of the vehicles. By reducing the drag force, it is possible to improve the fuel economy. To study the delay of flow separation, rear-end spoiler application is tested at the end of a sedan car using a numerical model. This study is conducted by using Computational Fluids Dynamics (CFD) ANSYS software to analyze the flow pattern, drag coefficient Cd, lift coefficient Cₗ, streamline pattern, and pressure contour of a sedan car. The model was tested with seven conditions which are without rear end spoiler attached and with a rear-end spoiler of six different inclination angles (0°, -2°, 2°, 4°, 6° and 8°). The two-equation models utilized in this work are k with the Reynolds-averaged Navier Stokes (RANS) equations for the fluid flow behavior around the sedan automobile. The Reynolds number used is Re = 3.94 x 10⁶. Based on the results, the drag and lift coefficient of all models differs which affect the car fuel efficiency and stability. The velocity streamlines flow and vortex formation pattern differ according to the rear-end spoiler inclination angle. [ABSTRACT FROM AUTHOR]

Fluid flow over a NACA airfoil (NACA 0012) was simulated using ANSYS FLUENT. A two-dimensional steady state simulation was conducted along with SST k-ω turbulence model. Grid independency was established and study was done by varying Reynolds number and angle of attack over a range of 5x105 to 2x106 and -15° to 15°, respectively. Lift and drag coefficients were calculated from the simulations and compared with their experimental values. An excellent agreement was noted for the coefficient of lift. However, some discrepancies were observed and highlighted for the coefficient of drag. Specifically, the simulated values of drag coefficients were 30 to 100% higher than the experimental values. The discrepancies are attributed to the selection of turbulence model and 2-D steady state flow. Over the range of parametric variation in this study, both lift and drag coefficients increased with an increase in the angle of attack. The effect of variation in Reynolds number was minor. The coefficient of drag decreased with Reynolds number, whereas the coefficient of lift remained almost unchanged. [ABSTRACT FROM AUTHOR]

A forward-facing aerospike have been identified as a passive flow control device for enhancing the aerodynamic efficiency and reducing the heat transfer in high-speed flows. In addition, it has been reported that the presence of a spike brings in unsteadiness in the form of oscillation and pulsation to the structure. Previous researchers have investigated the aerothermodynamic coefficients, together with offering a detailed explanation of the flow physics and associated unsteadiness, and their dependence on the spike's geometric characteristics (spike nose, and length-to-fore-body diameter ratio, L/D). This work focuses on ascertaining the role of flow speeds (free-stream Mach number), and their energy content, in governing the physics around a spiked body, which is yet to be established. Numerical investigation has been carried out using axisymmetric Navier-Stokes laminar flow solver for Mach number range of 2.0 to 7.0. A round-tip spike with flat-face cylindrical after-body have been simulated for spike length ratio of L/D=2.0, with spike diameter to fore-body diameter of 0.1. The flow unsteadiness has been analyzed with drag and pressure coefficients variation at different Mach numbers. It was found that the flow field around the spiked blunt nose behaves in pulsation mode at lower Mach numbers 2, 3 and transition to oscillatory mode at higher Mach numbers 5, 6 and 7, while remain almost stable at Mach 4. The limit of Strouhal Number for characterizing the pulsation and oscillation modes at various Mach numbers for spike length of L/D = 2 with flat after-body is observed as 0.2, however it may very well depend on other geometric parameters of spike and after-body. [ABSTRACT FROM AUTHOR]