Aerodynamic Characteristics Of Vehicle Research Articles

Influence of wind barrier on aerodynamic characteristics of vehicle on railway–highway combined bridge

Wind barriers with different parameters will change the aerodynamic force of the car on the bridge as well as the stability of the vehicle–bridge system, affecting the vehicle’s safety and comfort. A numerical simulation test was conducted on the bridge-deck with three different air permeability wind barriers under three distinct vehicles of varying sizes and wind directions, with a large-span road–rail asymmetric cable-stayed bridge serving as the engineering foundation. The results show that the roll force of the bridge is proportional to the width of the body and inversely related to the height of the train. The roll force of a vehicle is inversely proportional to its height and width. The type of vehicle and the properties of the bridge deck exert minimal influence on the stability of the bridge when a single vehicle is positioned upstream. When a single vehicle is situated downstream, the tri-component force coefficient of the bridge undergoes significant changes, and the vehicle’s impact on the bridge’s stability becomes more pronounced. When the bridge deck’s ventilation rate is at 50%, the drag coefficient of the bridge deck doubles compared to that of a bare bridge deck, and the wind pressure coefficient of the vehicle surface on the bridge approaches zero. In scenarios involving two vehicles, the shielding effect caused by the vehicles positioned upstream and downstream results in a substantial shift in the aerodynamic forces acting on the two vehicles. This increases the wake width of the bridge and generates a visible vortex in the wake.

Assessment of drag prediction techniques based on radar data for supersonic vehicles

Flight testing is probably the most accurate approach for defining the aerodynamic characteristics of a flying vehicle. This is justified by the fact that compared to other approaches, either engineering or computational ones, flight testing is indeed the one that perfectly resembles the real flight environment. Flight data are either obtained by measuring the vehicle’s kinematics via onboard sensors or by tracking the vehicle’s flight via (commonly) radars. The advantages of the latter approach are evident in cases where modifying the vehicle design is not possible or in cases where rival/enemy vehicles are examined. The key issue for this approach is the quality and demands of the technique by which vehicle aerodynamic characteristics are reduced from flight-tracked data. In the open literature, different techniques are used to analyze radar data of vehicle position and utilize them to predict vehicle drag coefficient. Each technique has its strengths and pitfalls. In this paper, the three well-used techniques of drag estimation from radar data namely, Least Square (LS), Maximum Likelihood Estimation (MLE), and Stepwise regression (SR), are considered. The underlying principle, the output, and the range of validity for each technique are addressed with emphasis on what differentiates each of them. The viability and validity of the three techniques are addressed based on the own flight testing of a free-flight supersonic vehicle and using the point-mass flight model. Meteorological data are also recorded and flight conditions are used to enhance the resulting calculations. Based on experimental data available from the literature, a comparison is conducted for the techniques examined. Considering the lack of flight data utilized, and in conjunction with data from the literature, it has been concluded that the SR technique outperforms for a higher sample rate, however, the MLE is more feasible when there is a lack of data.

Computational study of a conceptual re-entry vehicle's aerodynamic characterization at Mach number-2

Re-entry vehicles are becoming an important topic of study in recent times due to the interest of many countries in space endeavor. They are incorporated with double-delta wings having many profiles, different strake and wing swept angles. A conceptual re-entry vehicle having a double delta wing with NACA0020 symmetrical aerofoil at the top surface and the reflex aerofoil at the bottom is studied. Here, the main objective is to examine the effect of viscosity on the aerodynamic characteristics of the vehicle by varying the angle of attack from 10°to 50°at a free stream Mach number of 2. The steady-state Reynolds Averaged Navier-Stokes equations with Spalart-Allmaras turbulence model and Euler equations are solved using ANSYS Fluent for examining the contribution of the viscous term on flow past the re-entry vehicle. The non-dimensional coefficients of lift, drag, pressure, Mach number, and density gradients obtained from both the models are compared. It is observed that the coefficients of lift and drag obtained from Euler simulations differed significantly from the Spalart-Allmaras turbulence model at all angle of attacks. The maximum value of lift coefficient is seen at 40°in Euler simulation and it appeared at 35°in Spalart-Allmaras model. Both the models have predicted the zones of attached flow, separated flow, leading-edge vortices and the shock pattern over the vehicle. But the flow transition and vortex breakdown are observed earlier in Spalart-Allmaras model compared to inviscid simulations. It suggested that the viscosity and fluctuation in the upstream flow has a significant role in the aerodynamic characteristics of re-entry vehicles.

Optimization of aerodynamic drag reduction for vehicles with non-smooth surfaces and research on aerodynamic characteristics under crosswind

Energy consumption and environmental pollution problems have become increasingly prominent in China. The drag reduction of vehicles is an effective method to improve the fuel economy of cars and reduce greenhouse emissions. In this paper, based on the MIRA squareback model, the influence of the shapes, arrangements, layout positions, and dimensions of the non-smooth units on the aerodynamic characteristics of vehicles are investigated through the computational fluid dynamics (CFD) method. The depth, longitudinal spacing, and horizontal spacing are taken as the design variables and the aerodynamic drag coefficient is used as the optimization objective. The optimal Latin hypercube experimental design method is adopted to select sample points, and the response values of each experiment sample point are calculated through the integrated platform in Isight software. According to the response values, the Kriging approximation model is built and validated. Furthermore, the multi-island genetic algorithm is applied to optimize the dimensions of pit non-smooth units. The aerodynamic characteristics of the smooth surface model and the optimized non-smooth surface model under steady crosswind are conducted using numerical simulation. The findings obtained from the investigation will provide a certain reference for the application of non-smooth units in the field of automobiles.

Bio-inspired design and performance evaluation of a novel morphing nose cone for aerospace vehicles

An effective way to improve the flight capability and environmental adaptability of aerospace vehicles is to design a morphing aircraft structure, which can actively change their aerodynamic shape. During different physiological activities, the abdomens of bees are regularly deformed to improve the efficiency of movement. This was used as an inspiration for the design of a nose cone for aerospace vehicles. Based on the deformation mechanism of the bee abdomen, a bionic design of a variable configuration morphing nose cone (MNC) mechanism with high sensitivity is proposed, which can realize real-time reverse self-locking of the mechanism via auxiliary branch chains. Theoretical models for the kinematics and dynamics of the MNC mechanism under two configurations are derived, verifying that the proposed mechanism has good kinematic and dynamic characteristics. The theoretical models are validated through simulation studies. In addition, static finite element simulations are performed to verify that the auxiliary locking branch chain can significantly improve the bearing capacity of the proposed mechanism. Moreover, the force and thermal parameters of different configurations of the MNC under corresponding typical working conditions are analyzed, enabling the improvement of the aerospace vehicle aerodynamic characteristics by the morphing of its nose cone. Finally, based on the analytic hierarchy process, different drag and heat flux reduction schemes are comprehensively evaluated.

System Identification Approach for eVTOL Aircraft Demonstrated Using Simulated Flight Data

This paper describes a system identification method for electric vertical takeoff and landing (eVTOL) aircraft. The approach merges fixed-wing and rotary-wing modeling techniques with new strategies to develop a modeling method for eVTOL vehicles using flight-test data. The eVTOL aircraft system identification approach is demonstrated through application to the NASA Langley Aerodrome No. 8 tandem tilt-wing, distributed electric propulsion aircraft using a high-fidelity flight dynamics simulation. Orthogonal phase-optimized multisine inputs are applied to each control surface and propulsor at numerous flight conditions throughout the flight envelope to collect informative flight data. An aero-propulsive model is identified at each flight condition using the equation-error method in the frequency domain. The local model parameters are then blended to create a global model across the nominal flight envelope. The identified models are shown to provide a good fit to modeling data with good prediction capability. The methodology is developed with a discussion of unique eVTOL vehicle aerodynamic characteristics and practical strategies intended to inform future flight-based system identification efforts for eVTOL aircraft.

CFD Numerical Simulation of Wind Field and Vehicle Aerodynamic Characteristics on Truss Bridge Deck under Crosswind

CFD Numerical Simulation of Wind Field and Vehicle Aerodynamic Characteristics on Truss Bridge Deck under Crosswind

Wind tunnel tests on aerodynamic characteristics of vehicles on same-storey highway and rail bridge under crosswind

Wind tunnel tests on aerodynamic characteristics of vehicles on same-storey highway and rail bridge under crosswind

Theoretical and numerical simulation study on aerodynamics of V configuration high-pressure capture wing (HCW-V)

The high-pressure capture wing (HCW) configuration has excellent aerodynamic characteristics verified by theoretical, experimental, and numerical simulation methods. It has a good effect on improving vehicle lift at hypersonic speed. A HCW-V configuration based on the HCW was proposed in this paper. This configuration further increased the vehicle's lift by increasing the wedge angle of the capture wing and forming a compression plane on the lower surface. We obtained the pressure ratio relationship between the upper and lower surfaces of the HCW-V configuration concerning the free-stream airflow Mach number, the body compression angle, and the captive wing wedge angle based on theoretical derivation. It was nearly 60% higher than the HCW configuration pressure ratio. In addition, the influence of the HCW-V configuration on the vehicle's aerodynamic characteristics at different Mach numbers and body compression angles was studied through numerical simulation methods. The HCW-V configuration improved the lift-to-drag ratio by at least 25% compared with the HCW configuration. The expression of the lift coefficient of the vehicle CL = −0.095Ma∞tanδ + 2.352tanδ + 0.031θ + 0.010 under the model presented was obtained in this study. Meanwhile, the adaptability of this configuration to varied Mach number and attack angle was investigated further. The average lift-to-drag ratio of HCW-V was increased by 23.7% and 7.09% at varying Mach numbers and angles of attack. The lift-to-drag ratio of the three-dimensional HCW-V configuration is 14% higher than that of the HCW configuration when the wedge angle is 4.19°.

Protective effect of railway bridge wind barriers on moving trains: An experimental study

Wind barriers are an important wind protection facility that has been commonly used in high-speed railways to ensure the ride comfort and driving safety of high-speed trains in wind-prone areas. This paper presents an experimental study on the protective effect of wind barriers on the moving head and tail train vehicles under crosswinds for the first time. This study utilized a novel wind tunnel test device of a moving train model. The effects of the wind speed and the height and porosity of the wind barriers on the protective effect for moving trains were investigated considering the aerodynamic characteristics of the moving train. The protective effects of the wind barrier on the head and tail vehicles were compared, and the relationship between the vehicle aerodynamic characteristics with and without employing the porous wind barrier was discussed to simplify the test conditions and improve the evaluation efficiency of the protective effect of the wind barrier. The results indicated that the protective effect of the wind barriers on the moving train varied with different yaw angles. In addition, the height and porosity of the wind barriers significantly affected the protective effect of the wind barriers. Furthermore, the relationship between the vehicle overturning moment coefficient, an important indicator for vehicle safety evaluation, with and without employing the porous wind barrier, is quantified via a wind speed reduction coefficient. The wind speed reduction coefficient enables fast prediction of the vehicle overturning moment coefficient after the installation of porous wind barrier at any given yaw angle β, without conducting additional wind tunnel tests.

Effects of embankment layouts on train aerodynamics in a wind tunnel configuration

Crosswind stability of rolling stocks running on an embankment has been a key focus for decades, stemmed from the high overturning risks under crosswind. The correct reproduction of the embankment layout in a wind tunnel is therefore of great significance for estimating the train's aerodynamics and running safety. In this study, four different 6-m-high embankment layouts are proposed to replicate realistic wind tunnel configurations with the improved detached eddy simulation (IDDES) method. These helped to estimate the aerodynamics of a leading vehicle when subjected to a block wind profile of 45 m/s at the typical yaw angle of 30°. Furthermore, a static wind tunnel test with a 1:20 scaled train/embankment model enabled the validation of the numerical algorithm. The overall results indicate that all the aerodynamic coefficients of the leading vehicle mounted on the leeward track of the embankment top, decrease rapidly with the extending length of the upstream embankment. Similar aerodynamic performance appears on scenarios such as wall-to-wall (W2W) and partially wall-to-wall (P–W2W), which highlight equivalences between W2W and P–W2W under yaw effects. However, those particular scenarios considerably underestimate the aerodynamic coefficients compared with a more realistic scenario based on open domain (OD) and motion boundaries. Therefore, the conservative assessment of the vehicle aerodynamic characteristics based on the finite-length-embankment in a wind tunnel test could be taken into consideration for determining the running safety.

A development of longitudinal static stability analysis method of a Wing-In-Ground effect vehicle in cruise during the design process

Traditional methods of Wing-In-Ground effect (WIG) vehicle longitudinal stability analysis in cruise are based on calculation of aerodynamic forces and moments coefficients and its derivatives. Static longitudinal stability analysis includes the determination of Irodov criteria, and functions of pitch moment coefficient versus lift force coefficient for constant angle of attack or ground clearance are considered as linear. Here the problem of development of WIG vehicle longitudinal static stability analysis method accounting the nonlinearity of pitch moment coefficient on lift force coefficient dependence for constant angle of attack is researched. WIG vehicle aerodynamic characteristics are determinate by RANS-SST numerical simulation. Results of numerical studies show that function of pitch moment coefficient versus lift force coefficient for constant angle of attack is approximated by curve of order no higher than two, and this function for constant ground clearance is linear. The relationship between static height stability, second derivative of the pitching moment coefficient with respect to lift force coefficient, and lift coefficient was derived. Reliability of analysis method is based on using of fundamental equations of WIG vehicle motion and fluid dynamics. Application of the method can simplify study of WIG vehicle stability during design process.

Vehicle Aerodynamic Characteristics due to Front-end Shape and Engine Cooling Air

Vehicle Aerodynamic Characteristics due to Front-end Shape and Engine Cooling Air

Aerodynamics of High-Sided Vehicles on Truss Girder Considering Sheltering Effect by Wind Tunnel Tests

Aerodynamic characteristics of vehicles are directly related to their running safety, especially for the high-sided vehicles. In order to study the aerodynamic characteristics under multiple sheltering conditions, a complex large scale (1:20.4) truss model and three high-sided vehicles including articulated lorry, travelling bus and commercial van models with the same scale were built. The aerodynamic coefficients under various sheltering effects of wind barriers with different heights and porosities, bridge tower and the vehicle on the adjacent lane were measured. According to the results, wind barriers can effectively reduce wind speed behind them, thus decreasing the wind load acting on the vehicle, which causes the decrease of the aerodynamic response of all three vehicles. However, the influence at the leeward side is limited due to installation of central stabilizers. When the vehicle passes through the bridge tower, a sudden change occurs, the aerodynamic coefficients decrease and fluctuate in varying degrees, especially for the commercial van. When the vehicle moves in different lanes behind the bridge tower, the sheltering effect of the tower on the aerodynamic coefficient in Lane 1 is much greater than that in Lane 2. With regard to the interference between two vehicles on the adjacent lanes, the relative windward area between the test vehicle and the interference vehicle greatly affects the aerodynamics of the test vehicle.

Wind tunnel tests on the aerodynamic characteristics of vehicles on highway bridges

Accurately quantifying the aerodynamic forces acting on vehicles and long-span bridges is critical for assessing the safety of moving vehicles on bridges which are subjected to strong wind. It is necessary to consider the aerodynamic interference between vehicles and the bridge, especially for this with the bluff body section and wind barriers. However, very few investigations have been carried out to find aerodynamic coefficients of vehicles on a bridge with the bluff body section and considering the effect of wind barrier. This article therefore carried out wind tunnel tests to determine aerodynamic coefficients of container truck on a bridge with a π-cross section and wind barriers. The influence of vehicle position in different road lanes of the bridge deck and the aerodynamic interference between vehicles on the aerodynamic characteristics of the vehicle and the bridge are investigated. Different heights and ventilation ratios of wind barrier are taken into consideration to examine variations of aerodynamic coefficients with different wind barriers. Furthermore, the change mechanism in the aerodynamic coefficients of the vehicles is observed by analyzing the wind pressure distribution on the surface of the vehicles. The test results show that the different lane locations of the vehicle affect the aerodynamic coefficients significantly, as well as the aerodynamic interference between vehicles with transverse arrangement or longitudinal arrangement, especially for the side force coefficient. The existence of wind barrier reduces the side force coefficients of the vehicle remarkably. Such effects also vary with the ventilation ratio and height of wind barrier.

Aerodynamic Effects of Viaduct-Cutting Connection Section on High-Speed Railway by Wind Tunnel Tests

AbstractThe wind environment and aerodynamic characteristics of vehicles are easily affected by the structural form of the railway. To investigate the aerodynamic effects of viaduct-cutting connect...

Effects of Riblet Shape of Non-smooth Surface on Aerodynamic Characteristics of Vehicle

To reduce the aerodynamic drag of the vehicle, three kinds of riblet shape non-smooth surfaces were arranged in the tail of the Motor Industry Research Association (MIRA) stepped-back vehicle mode. The shapes of the non-smooth riblet elements are triangular, circular and rectangular. Computational fluid dynamics (CFD) method was used for numerical analysis. To verify the effectiveness of the analysis method, the analysis result of the standard MIRA stepped-back vehicle mode was compared with wind tunnel test data. The tail-flow, pressure and turbulent kinetic energy of the MIRA stepped back vehicle modes, which were arranged with riblet elements, were analyzed. The effects of riblet shape of non-smooth surfaces on the reduction of vehicle’ aerodynamic drag were compared with each other. The simulation results show that the three kinds of non-smooth surfaces have a good effect on drag reduction by reducing the negative pressure in the tail zone of the model, reduce the turbulent kinetic energy and reduce energy dissipation. The circular non-smooth surface is better than the other, with drag reduction effect of 5.53%.

Experimental Investigation of Aerodynamic Characteristics of Vehicles Subjected to Fluctuating Wind

Experimental Investigation of Aerodynamic Characteristics of Vehicles Subjected to Fluctuating Wind

Dynamic analysis of long-span cable-stayed bridges under wind and traffic using aerodynamic coefficients considering aerodynamic interference

The aerodynamic characteristics of vehicles are critical to assess vehicle safety and passenger comfort for vehicles running on long span bridges in a windy environment. However, in previous wind–vehicle–bridge (WVB) system analysis, the aerodynamic interference between the vehicle and the bridge was seldom considered, which will result in changing aerodynamic coefficients. In this study, the aerodynamic coefficients of a high-sided truck on the ground (ground case) and a typical bridge deck (bridge deck case) are determined in a wind tunnel. The effects of existent structures including the bridge deck and bridge accessories on the high-sided vehicle\'s aerodynamic characteristics are investigated. A three-dimensional analytical framework of a fully coupled WVB system is then established based on the finite element method. By inputting the aerodynamic coefficients of both cases into the WVB system separately, the vehicle safety and passenger comfort are assessed, and the critical accidental wind speed for the truck on the bridge in a windy environment is derived. The differences in the bridge response between the windward case and the leeward case are also compared. The results show that the bridge deck and the accessories play a positive role in ensuring vehicle safety and improving passenger comfort, and the influence of aerodynamic interference on the response of the bridge is weak.

Computational Aeromechanics of a Manuevering Unmanned Aerial Vehicle with Variable-Incidence Wings

The aerodynamics and flight mechanics of the dynamic maneuver of a low-speed propeller-powered puller-type unmanned aerial vehicle are modeled by solving the unsteady, incompressible Navier–Stokes equations and the six-degree-of-freedom rigid-body flight dynamics equations together. The flight maneuver of this unmanned aerial vehicle is accomplished by swiveling the outboard wings relative to the inboard wing fixed to the fuselage to change the angle of attack toward stall angle to slow down the unmanned aerial vehicle for symmetric as well as asymmetric flight conditions. To set the stage for a computational aeromechanics modeling, the performance characteristics of a propeller are assessed numerically first. Time-accurate unsteady, unmanned aerial vehicle aerodynamic characteristics are estimated on the basis of high-fidelity computational aerodynamics, and the flight trajectory of the unmanned aerial vehicle is computed as part of the overall computed solution, considering the variation of aerodynamic characteristics during the flight maneuver by coupling the aerodynamics and flight dynamics.