Automotive Aerodynamics Analysis Using Two Commonly Used Commercial Software

This paper discusses the aerodynamics characteristics of Blended Wing Body — Baseline II E2, unmanned aerial vehicle aircraft. A computational method, Computational Fluid Dynamic (CFD) Star CCM+ software has been performed to obtain the aerodynamics characteristic of the BWB. The aerodynamic characteristics prediction of BWB-Baseline II E2 aircraft was obtained through CFD analysis using unstructured mesh and standard one — equation turbulence model, Spalart-Allmaras was selected in the investigations. Lift coefficient (CL), drag coefficient (CD) and moment coefficient (CM) were studied at flight condition of Mach 0.1 (∼34 m/s) at different angles of attack, α. The CFD results were compared with the experimental result. The results show the trend of lift curves are similar at the linear region (α = −10° to 7°) but at the higher angle of attack the trends become nonlinear. The drag coefficient for CFD simulations is greater than experimental result and there are differences in pitching moment curves between CFD simulation and experiment data which the experiment data shows a steep curve than simulation.

This paper presents a comparative aerodynamic analysis of two vehicle models—a hatchback and a sedan—using computational fluid dynamics (CFD) simulations conducted with SimScale software. The primary objective is to evaluate the behavior of the external flow around the body, focusing on determining the drag (Cd) and lift (Cl) coefficients, as well as analyzing the flow patterns and recirculation zones. The vehicle geometries were generated using the artificial intelligence tool Tripo3D.AI, to investigate the feasibility of automated models for aerodynamic analysis. The study was conducted with the k – ω SST turbulence model, suitable for simulations in regions with flow separation and boundary layers. The mesh was composed of polyhedral elements with local refinements in regions of interest, automatically generated by SimScale. The boundary conditions included velocity inputs of 25 m/s, walls with no-slip and slip conditions, and a lower wall with movement equal to the flow velocity. The results indicated a drag coefficient (Cd) of 0.308 for the sedan model and 0.601 for the hatchback, representing an increase of approximately 95% in Cd for the hatchback compared to the sedan. Regarding the lift force, a value of -0.00014 was observed for the sedan and -1.97 for the hatchback, indicating a greater vertical aerodynamic effect in the hatchback. The simulations showed good numerical convergence, validating the adopted approach.

Two or multiple parallel jets are an important shear flow that widely existing in many industrial applications. The interaction between turbulence jets enables fast and thorough mixing of two fluids. The mixing feature of parallel jets has many engineering applications, such as, in Generation IV conceptual nuclear reactors, the coolants merge in upper or lower plenum after passing through the reactor core. While study of parallel jets mixing phenomenon, numerical experiments such as Computational Fluid Dynamics (CFD) simulations are extensively incorporated. Validation of varied turbulent models is of importance to make sure that the numerical results could be trusted and served as a guideline further design purpose. Many commercial CFD packages in the market such as FLUENT and Star CCM+ can provide the ability to simulate turbulent flow with predefined turbulence model, however, such commercial solvers may lack the flexibility that allow users build their own models for R&D purpose. The existing solvers in OpenFOAM are developed to fulfill both academic and industrial needs by achieving large-scale computational capability with a variety of physical models. Moreover, as an open source CFD toolbox, OpenFOAM grants users full control of the source code with complete freedom of customization. The purpose of this study is to perform CFD simulation using OpenFOAM for two submerged parallel jets issuing from two rectangular channels. Fully hexahedron multi-density mesh is generated using blockMesh utility to ensure velocity gradients are properly evaluated. A generalized-multi-grid solver is used to enhance convergence. Based on Reynolds-Averaged Navier-Stokes Equations (RANS), the realizable k-ε and k-ε shear stress transport (SST) are selected to model turbulent flow. Steady state Finite Volume solver simpleFoam is used to perform the simulation. In addition, data from experiments run in Thermal-Hydraulic Lab at Texas A&M University using particle image velocity (PIV) and Laser Doppler Anemometry (LDA) methods are considered in order to compare and validate simulation results. A number of turbulence characteristic such as mean velocities, turbulent intensities, z-component vorticity were compared with experiments. It was found that for stream-wise mean velocity profile as well as shear stresses, the realizable k-ε model exhibits a good agreement with experimental data. However, velocity fluctuation and turbulence intensities, simulation results showed a certain discrepancy.

Aerodynamic characteristics of a guided rocket projectile are numerically simulated. Simulations are performed in a range of flight conditions using a commercial CFD software FLUENT, and variations of lift coefficients and drag coefficients with Mach numbers and angles of attack were demonstrated. The numerical results also indicate that the angle of canard deflection has significant influence on the flow field near tailfins.

<div class="section abstract"><div class="htmlview paragraph">Simulation tools play a significant role in the automotive industry due to their cost-reducing capabilities in new model development. Computational Fluid Dynamics (CFD) is extensively utilized in various applications, such as vehicle aerodynamics and engine thermal management. However, its application in manufacturing engineering is not yet widespread. One crucial process in automotive manufacturing is the application of the base coat, which provides protection for the final paint layer. This process involves three key steps: bodywork immersion, electrophoretic deposition (E-coat), and bodywork removal from the bath. Each of these steps can be evaluated using appropriate CFD models. During the immersion step, the primary objective is to minimize the presence of trapped air. In the E-coat step, the focus is on controlling the paint layer thickness on the Body-in-white (BIW). Lastly, the drainage analysis aims to minimize the retention of bath fluid, thereby preventing contamination in subsequent baths. In this study, we propose a methodology utilizing Simcenter STAR-CCM+ as the CFD code and a generic car geometry to evaluate these three painting stages. Our methodology demonstrates the effectiveness of Simcenter STAR-CCM+ in predicting the behavior of the BIW throughout the painting process. By simulating the evolution of physical phenomena, our methodology provides valuable information regarding the presence of trapped air during the dipping stage, the thickness of the paint layer during E-coat, and the volume of retained liquid during drainage. This approach offers a promising means to reduce prototype investments by anticipating the behavior of the BIW during the virtual painting process. As a result, potential quality issues can be identified and rectified by making necessary component changes. Moreover, this methodology can be employed to optimize the painting process itself, including the adjustment of parameters related to the generated electric field and the movement of the BIW within the bath. These optimizations aim to enhance energy efficiency and accommodate changes in line speed, maintenance of anodes, and alterations in chemical characteristics of the bath. In conclusion, the use of CFD simulations, specifically employing the presented methodology with Simcenter STAR-CCM+, proves to be highly beneficial in evaluating and optimizing the three critical stages of the automotive painting process. This approach enables the identification and mitigation of quality problems, offers cost savings in prototype development, and facilitates process adjustments for improved efficiency and adaptability.</div></div>

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

Kenyalang is a fuel cell powered Unmanned Aerial Vehicle (UAV) developed by Universiti Teknologi MARA (UiTM). This paper discusses the aircraft performances analysis of Kenyalang. Computational Fluid Dynamic (CFD) using Numeca software had been performed to obtain the aerodynamics characteristic of the Kenyalang UAV in the form of lift (CL) and drag (CD) coefficients. Unstructured mesh and standard one - equation turbulence model, and Spalart-Allmaras selected in the simulation. Lift coefficients (CL) and drag coefficients (CD) were studied at flight condition of Mach 0.08 (~26 m/s) at different angles of attack, α. The CFD data results were used to obtain Stall Speed, Take off Distance and Rate of Climb, and the results are shown in this paper.

Unmanned aerial vehicles (UAV) are used in the military field for missions such as observation, surveillance and seeking object. UAV observation can be used to monitor humans, weather, forests, agriculture, and fisheries and so on. UAV can be operated for very broad missions with low development costs compared to manned aerial vehicles with a low risk of death. The design of an aircraft affects the performances of the aircraft itself. Aircraft flying characteristics are influenced by the value of coefficient of drag (CD) and coefficient of lift (CL). The value of CD affects how much aircraft friction with the air, while the value of CL affects how much lifting force the aircraft is produced so it can fly. The design output needs the most optimal CD and CL values to get the optimal aircraft performance. In this study, we simulated the effect of 4 digit NACA changes on the characteristics of the plane’s CD and CL. This study uses variations modification of NACA digits with different variables. NACA airfoil 4 digit series (MPXX) designates camber lines, maximum camber position and thickness. Based on the results of this study, the optimal CD and CL values for the Airfoil NACA with the Aerosonde UAV model are designs that have a large ratio of lift and drag (CL / CD). The lower the CD value and the higher the CL value, the better the performance of the UAV. The design that has the largest CL / CD is the NACA 6412 Airfoil.

Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicles (UAVs) offer significant advantages in operations requiring both vertical lift and efficient forward flight. However, VTOL aircraft design is challenge in terms of stability, control, and aerodynamic efficiency across flight regimes. Aerodynamic analysis is conducted to determine the variations of pressure distributions, lift and drag forces and center-of-pressure (CP) movement all of which are important towards design optimization and control modeling. This study focuses on aerodynamic analysis of a small VTOL fixed-wing UAV without using any additional actuators or complex tilting mechanisms. The designed UAV only uses the regular control surfaces such as Aileron, Rudder and Elevator of the fixed wing aircraft for maneuverability. Computational fluid dynamics (CFD) has become a essential tool in aerodynamic design and analysis. Studies of flyingwing VTOL UAVs revealed that CFD is effective in the prediction of stability and flow separation which is critical in transition controllability [1]. The structural and CFD studies were also coupled which showed that aeroelastic effects at high lift and inertia can be critical to performance and safety [2]. CFD has also been useful in wing and fuselage optimization to minimize drag and preserve lift as well as in the prediction of aerodynamic coefficients by use of turbulence models to provide reliable control inputs [3]. In addition to CFD, low-order methods like XFLR5 have been used to facilitate initial design through evaluation of centerof-gravity balance and optimization of wing geometry under structural constraints [4] [5]. On this basis, th present work implements CFD and XFLR5 to examine the aerodynamic forces, pressure field, and CP-CG interaction in a fixed-wing UAV-VTOL.

A multi-objective optimization design framework integrated with CFD for the design of AUVs

Comparison of BEM-CFD and full rotor geometry simulations for the performance and flow field of a marine current turbine

The flow over two different shaped bluff bodies in tandem arrangement was numerically investigated by using the finite volume method with Computational Fluid Dynamics (CFD) techniques. The shape of the downstream main bluff body is a right circular cylinder, with shape unchanged, while the shape of the upstream bluff body varies between: circle, triangle, square, ellipse and cylindrical half-shell. The hydraulic diameters of both front and rear bluff bodies are equal. The analysis is carried out for Reynolds numbers of 100, 300 and 500, and center-to-center distance ratios, L/D, of 1.5, 2, 3, 4.5 and 6. Flow characteristics in terms of the lift and drag coefficients and Strouhal number are analyzed and the vortex shedding patterns around the bluff bodies are described. The influence of the shape of the fore cylinder on the flow characteristics is the innovation point of this paper. It is concluded that the center-to-center distance ratio, L/D, and the shape of the upstream bluff body have important effects on the drag and lift coefficients, vortex shedding frequencies from the two bluff bodies, and flowfield characteristics.

A combined numerical and experimental study has been carried out to examine the structure of the flow field from a 4 valve cylinder head under steady state conditions. In this paper, Particle Image Velocimetry (PIV) and the finite-volume Computational Fluid Dynamic (CFD) package, STAR CCM+ have been used on a single cylinder Lotus engine head with a pent-roof for a number of fixed valve lifts at two pressure drops of 250 mm and 635 mm of H2O, equivalent to engine speeds of 2,500 and 4,000 RPM respectively. The Reynolds Stress Turbulence Model (RSTM) is used to simulate the turbulent flow structure. The generated mesh is a polyhedral type that holds nearly 3.7 million grid points. The computational results were validated through qualitative and quantitative comparisons with the PIV experimental measurements on both horizontal and vertical cross sections. Results show reasonable agreements between numerical and experimental outcomes for the mean and RMS velocity values at different locations inside the engine cylinder. The nature of the flow structure, together with discussions on the discrepancies observed are presented and discussed.

<div class="htmlview paragraph">The Objective of this paper is to explain a procedure for using Arbitrary Shape Deformation (ASD) technology coupled with Computational Fluid Dynamics (CFD) software for product development of a generic catalytic converter inlet-cone diffuser. The paper uses the development of an inlet-cone diffuser as an example of such a process.</div> <div class="htmlview paragraph">The non-uniformities of the flow field at the inlet of the catalytic converter bricks are considered to have a negative impact on the converter performance. Computational Fluid Dynamics (CFD) is a powerful tool for computing the flow field in the exhaust system and the catalytic converter which enables the engineers to optimize the geometry of the inlet cone at a very early design stage. The goal of this study is to optimize the shape of an inlet-cone diffuser upstream of a catalytic converter to reduce the pressure drop and maximize the uniformity of exhaust gas distribution on the catalytic converter inlet. The objective of this study is to utilize shape optimization technology to quickly optimize design concept. This will eliminate the lengthy process of looping from CAD to mesh generation to solver. In this study Sculptor<sup>™</sup>, the commercial shape optimization software is used to automatically adjust the shape of the cone diffuser and end-cone, which is coupled to commercial CFD software, Fluent<sup>™</sup>. ICEM<sup>™</sup> CFD Hexa was used for the mesh generation.</div>

A summary of the computational aerodynamic performance tools and analyses for the development of the Surfing Aircraft Vortices for Energy (SAVE) formation flight concept is presented. Aerodynamic analysis is accomplished using several, multi-fidelity prediction methods, including a vortex lattice method (VLM) approach, a panel method to model body effects, and a high-fidelity hybrid computational fluid dynamics (CFD) method that couples a Reynolds Averaged Navier-Stokes (RANS) flow solver for the near-body simulation with a quasi-3D RANS approach for the evolution of wakes over long longitudinal distances. Computational analysis is used to develop a comprehensive aerodynamic database for flight simulation and control law design, to develop a drag benefit “map”, which is used to determine the optimum location of the trailing airplane relative to the leading airplane wake, and to compare with flight-derived performance data to validate the use of CFD for the SAVE program. Finally, an extension of the hybrid CFD method and initial results for a 3-airplane echelon formation to highlight the multiple wake interaction effects and complex flow physics is presented.