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Ground effect of an inverted double element wing diffuser on a sedan car

HELIYON 2024年第8期10卷 e29435页

作者： Abood, Mustafa Sabeeh Hussain, Ihsanyahya Univ Baghdad Mech Engn Dept Baghdad Iraq

The diffuser is a critical component in sports cars, enhancing aerodynamics by increasing downforce and reducing drag. Previous studies have focused on its dependence on diffuser incidence, height, and base pressure. The design of the car, particularly the rear end shape and the rear wing's presence, affect base pressure and the diffuser's performance. Previous studies have investigated the effects of diffuser geometry on aerodynamic performance, but the current study is the first to examine the relationship between the diffuser and the rear tires. It also provides specific and quantitative results on the impact of different diffuser design parameters on drag and downforce. The relationship between the rear tires and the double-element inverted wing diffuser using computational fluid dynamics (CFD) was investigated. This is an essential problem because the diffuser is a critical component of sports cars, and its design can significantly impact aerodynamic performance. CFD was used to simulate the flow of air around the car model. The CFD model was based on the Nissan Sunny (Versa) type Almera design, and the diffuser main element and flap wing angles were set at 4 and 15.5 degrees, respectively. The flap gap, overlap distance, and wing ride height above the ground were varied to achieve an optimal aerodynamic design. The study found that the wing's ride height significantly influences the flow through the diffuser. The diffuser significantly impacts base pressure and downforce production. Increasing the ride height decreases base pressure, leading to an increase in downforce until a specific point near the car body, where downforce further increases. The study concluded that the best double-element diffuser design was selected based on lift-to-drag results and the allowable dimensions of the car, wing ride height, element gap, and overlap distances. Ultimately, the best diffuser wing design features a ride height of 154 mm, a gap distance of 10 mm, and an overlap of

关键词： Ground effect Double -element inverted wing Nissan sunny car Car diffuser CFD Drag reduction passive flow control

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Drag Reduction by Application of Different Shape Designs in a Sport Utility Vehicle

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INTERNATIONAL JOURNAL OF AUTOMOTIVE AND MECHANICAL ENGINEERING 2021年第3期18卷 8870-8881页

作者： Elsayed, O. Omar, A. Jeddi, A. Elhessni, S. Hachimy, F. Z. Int Univ Rabat Sch Aerosp & Automot Engn LERMA Campus UIRParc Technopolis Rabat 11100 Sala Al Jadida Morocco

Road vehicles drag is a direct consequence of a large wake area generated behind. This area is created owing to the vehicle shape, which is determined by the class, functional and aesthetic of the vehicle. Aerodynamic characteristics are a ramification and not the reason for the vehicle architecture. To enhance pressure recovery in the wake region, hence reduce drag, three different passive flow control techniques were applied to sport-utility-vehicle (SUV). A three-dimensional SUV was designed in CATIA, and a numerical flow simulation was conducted using Ansys-Fluent to evaluate the aerodynamic effectiveness of the proposed flow control approaches. A closed rectangular flap as an add-on device modifies the wake vortex system topology, enhances vortex merging, and increases base pressure which leads to a drag reduction of 15.87%. The perforated roof surface layer was used to delay flow separation. The measured base pressure values indicate a higher-pressure recovery, which globally reflected in a drag reduction of 19.82%. Finally, air guided through side rams was used as steady blowing. A steady passive air jet introduced at the core of the longitudinal trailing vortices leads to a confined wake area. The net effects appear in a global increase in the base pressure values and the pronounced drag reduction of 22.67%.

关键词： passive flow control Perforated roof Side ram Pressure recovery Vortex merging

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Turbulence model study for aerodynamic analysis of the leading edge tubercle wing for low Reynolds number flows

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HELIYON 2024年第11期10卷 e32148页

作者： Ali, Intizar Hussain, Tanweer Unar, Imran Nazir Kumar, Laveet Ul Ahad, Inam Mehran Univ Engn & Technol Dept Mech Engn Jamshoro 76080 Sindh Pakistan Dublin City Univ Form Adv Mfg Res Ctr 1 Sch Mech & Mfg Engn Dublin D09 V209 Ireland Mehran UET Natl Ctr Robot &Automat Condit Monitoring Syst Jamshoro Pakistan Mehran Univ Engn & Technol Dept Chem Engn Jamshoro 76080 Sindh Pakistan Qatar Univ Coll Engn Dept Mech & Ind Engn Doha Qatar

A turbulence model study was performed to analyze the flow around the Tubercle Leading Edge (TLE) wing. Five turbulence models were selected to evaluate aerodynamic force coefficients and flow mechanism by comparing with existing literature results. The selected models are realizable k-epsilon, k-omega Shear Stress Transport (SST), (gamma - Re theta) SST model, Transition k-kl-omega model and Stress- omega Reynolds Stress Model (RSM). For that purpose, the TLE wing model was developed by using the NACA0021 airfoil profile. The wing model is designed with tubercle wavelength of 0.11c and amplitude of 0.03c. Numerical simulation was performed at chord-based Reynolds number of Rec = 120,000. The Computational Fluid Dynamic (CFD) simulation reveals that among the selected turbulence models, Stress- omega RSM estimated aerodynamic forces (i.e. lift and drag) coefficients closest to that of the experimental values followed by realizable k-epsilon, (gamma - Re theta) SST model, k-omega SST model and k-kl-omega model. However, at a higher angle of attacks i.e. at 16 degrees & 20 degrees k-omega SST model predicted closest drag and lift coefficient to that of the experimental values. Additionally, the critical observation of pressure contour confirmed that at the lower angle of attack Stress- omega RSM predicted strong Leading Edge (LE) suction followed by realizable k-epsilon, (gamma - Re theta)SST model, k-omega SST model and k-kl-omega model. Thus, the superiority of Stress- omega RSM in predicting the aerodynamic force coefficients is shown by the flow behavior. In addition to this pressure contours also confirmed that k-kl-omega model failed to predict tubercled wing aerodynamic performance. At higher angles of attacks k-omega SST model estimated aerodynamic force coefficients closest to that of the experimental values, thus k-omega SST model is used at 16 degrees & 20 degrees AoAs. The observed streamline behavior for different turbulence models showed that the Stress-

关键词： passive flow control Leading edge tubercle CFD simulation Turbulence model Low Reynolds number flows

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Comment to "Atmospheric boundary layer modeling in a short wind tunnel" by Dan Hlevca and Mircea Deguratu, EJM/B Fluids, 79 (2020), 367-375

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EUROPEAN JOURNAL OF MECHANICS B-FLUIDS 2021年 85卷 397-399页

作者： Cook, Nicholas J. Independent Wind Engineer Highcliffe-on-Sea Dorset UK

George Santayana's aphorism "Those who cannot remember the past are condemned to repeat it" has never been more apposite than as applied to this paper. The paper rebutted here reproduces, without any form of acknowledgement, the method of reproducing characteristics of the atmospheric boundary layer (ABL) in a wind tunnel published in 1957 (Owen and Zienkiewicz, 1957). This method, together with the complementary method of Elder (Elder, 1957), was in widespread use through the 1960s before its inadequacies were recognised and it was supplanted by rough-wall boundary layers generated in the new generation of boundary-layer wind tunnels. This paper does not qualify as novel or original work worthy of publication in 2020. (C) 2020 Elsevier Masson SAS. All rights reserved.

关键词： Wind tunnel atmospheric boundary layer development passive flow control Atmospheric turbulence Wind engineering

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Effect of unsteady cavitation on hydrodynamic performance of NACA 4412 Hydrofoil with novel triangular slot

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Heliyon 2025年第3期11卷 e42266页

作者： Biswas, Sayan Harish, R. School of Mechanical Engineering Vellore Institute of Technology Tamil Nadu Chennai 600127 India

This study demonstrates the hydrodynamic performance of a modified NACA 4412 hydrofoil and compares it with the base NACA 4412 hydrofoil in the presence of cavitation. A triangular slot has been introduced at the mid-section of the suction side of the hydrofoil to modify the flow characteristics and assess its effects on the performance at different operational cavitation numbers spanning from 0.8 to 2.5, and at different angles of attack ranging from 4° to 16°. The performance metrics considered include the coefficient of lift, coefficient of drag, and the lift-to-drag ratio. The Reynolds number considered in this study is approximately 1.5 million. The SST k-ω turbulence model, homogeneous mixture multiphase model, and Schnerr& Sauer cavitation model have been employed in this study. At lower cavitation numbers, the modified hydrofoil is better able to control cavitation phenomena compared to the base hydrofoil. However, at higher cavitation numbers, the base hydrofoil exhibits slightly better performance than the modified hydrofoil in terms of lift-to-drag ratio, despite having a lower lift coefficient. Furthermore, the modified hydrofoil demonstrates improved performance at 4°, 8°, and 16° angles of attack, while the base hydrofoil performs better at a 12° angle of attack. It was also observed that stalling occurs at a 16° angle of attack for the base hydrofoil, whereas the modified hydrofoil successfully avoids stalling. © 2025 The Authors

关键词： NACA4412 hydrofoil passive flow control Schnerr& Sauer model SST k-ω turbulence model Unsteady cavitation

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passive DRAG REDUCTION TECHNOLOGY USING MICROFIBER COATINGS

PASSIVE DRAG REDUCTION TECHNOLOGY USING MICROFIBER COATINGS

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ASME-Fluids-Engineering-Division Summer Meeting (FEDSM)

作者： Hasegawa, Mitsugu Sakaue, Hirotaka Univ Notre Dame Notre Dame IN 46556 USA

ISBN: (纸本)9780791885307

Engineered surfaces and coatings can passively manipulate flow over a bluff-body without significant retrofitting and are of great technological interest for a broad range of applications in the engineering field. A microfiber coating with a hair-like structure is developed and studied as a passive drag reduction method for flow over a cylinder that features both attached and separated flow. The impact of the microfiber coating on drag is experimentally investigated at a Reynolds number of 6.1 x 10(4) based on the cylinder diameter. Microfiber coatings of various lengths between 1.1% and 8.0% of the cylinder diameter are fabricated using flocking technology and applied to various positions on the cylinder surface between the leading and trailing edges. It is shown that the microfiber length and location are both influential parameters in drag reduction. Two types of drag reduction can be seen depending on the location of the microfiber coating: (1) Drag is reduced significantly if the microfiber coating is applied before flow separates over the cylinder (2) Drag is reduced moderately if the microfiber coating is applied after the point of flow separation on the cylinder. The former case's best performance is achieved with a microfiber length of less than 1.8% of the cylinder diameter. The latter case shows better performance with relatively long fibers, where the microfiber's length is greater than 3.3% of the cylinder diameter.

关键词： Microfiber Flocking Cylinder flow passive flow control Drag reduction

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A PARAMETRIC STUDY ON THE EFFECT OF CASING TREATMENT SLOTS ON PERFORMANCE ENHANCEMENT OF A SINGLE STAGE AXIAL flow COMPRESSOR

A PARAMETRIC STUDY ON THE EFFECT OF CASING TREATMENT SLOTS O...

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ASME Gas Turbine India Conference (GTINDIA)

作者： Amin, Gautham A. Salunkhe, Pramod B. Kini, Chandrakanth R. Manipal Acad Higher Educ Manipal Inst Technol Dept Aeronaut & Automobile Engn Manipal 576104 Karnataka India

ISBN: (纸本)9780791885536

This paper numerically investigates the effect of slots on the performance of a highly subsonic axial flow compressor. The axial flow compressor consisting of 21 rotor blades with NACA 65 series blade profile was used for the simulations. The present results were obtained using different turbulence models and shear stress transport model was found to be the best one. Studies were conducted to determine the influence of length, depth and skew angle of the slot on the compressor performance. The slot width and centre-to-centre distance between the successive slots were maintained at 6.3% C-a and 11% C-a , respectively. The present study was carried out at different slot lengths (0 to 100% of axial chord, 20 to 100% of axial chord and 40 to 100% of axial chord), slot depths (7.9, 11 and 15.7% C-a) and skew angles (0 degrees, 30 degrees, 45 degrees and 60 degrees). The slot length of 20 to 100% of C-a , depth of 15.7% C a and skew angle of 60 degrees resulted in the best compressor performance leading to 22.1% stall margin improvement. Subsequently, flow characteristics were studied without and with slots.

关键词： Axial compressor casing treatment axially skewed slots stall margin passive flow control

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Numerical study of aerodynamic characteristics on a straight-bladed vertical axis wind turbine with bionic blades

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ENERGY 2022年第PartE期239卷 122453-122453页

作者： Zhu, Xinyu Guo, Zhiping Zhang, Yanfeng Song, Xiaowen Cai, Chang Kamada, Yasunari Maeda, Takao Li, Qing'an Inner Mongolia Univ Technol Coll Mech Engn Hohhot 010051 Peoples R China Inner Mongolia Univ Technol Coll Sci Hohhot 010051 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China Mie Univ Div Mech Engn 1577 Kurimamachiya Cho Tsu Mie 5148507 Japan Inner Mongolia Univ Technol Sch Energy & Power Engn Hohhot 010051 Peoples R China

This paper has attempted to investigate the aerodynamic characteristics of the straight-bladed vertical axis wind turbine (VAWT) with bionic blades for better application of bionic blades to VAWTs. The study was based on the computational fluid dynamics numerical simulation (CFD numerical simulation) technique to investigate the differences of the power and tangential force coefficients of the wind turbine between the bionic blades and standard blades at three different tip speed ratios (TSRs = 1.38, 2.19, and 2.58) for the mainstream wind velocity of 8.0 m/s. The results showed that the average power coefficient enhancing effect of the bionic blade increases as the TSR increases, and the average power coefficient of the bionic blade is higher than that of the standard blade mainly because of the high wind energy utilization in the wave trough section. Moreover, the power coefficients of the wave crest sections for bionic blades are better than that of the standard blades at the downstream region of 200 degrees < theta < 260 degrees. This research provides a reference for the use of bionic blades in the straight-bladed VAWT. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： VAWT passive flow control Wavy leading edge Numerical simulation Power coefficient

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TIME RESOLVED PIV MEASUREMENTS OF A SLOT LOBED JET ISSUING INTO A CROSSflow

TIME RESOLVED PIV MEASUREMENTS OF A SLOT LOBED JET ISSUING I...

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ASME-Fluids-Engineering-Division Summer Meeting (FEDSM)

作者： Lewandowski, Michael Kristo, Paul Weiss, Abdullah Kimber, Mark Texas A&M Univ Dept Nucl Engn College Stn TX 77840 USA Texas A&M Univ Dept Mech Engn College Stn TX 77840 USA

ISBN: (纸本)9780791885291

The near field mixing phenomenon created by a round jet with three slot lobes exhausting into a crossflow are investigated at a velocity ratio of 0.5. Time-resolved particle image velocimetry measurements provide instantaneous velocity fields of the slotted jet in crossflow, allowing for evaluation of the first and second order turbulent statistics in two perpendicular planes of interest. The independently controlled jet exit and crossflow inlet are first characterized extensively to confirm the velocity ratio and anticipated momentum exchanges. Spanwise and transverse mean velocity profiles reveal that the interaction of the three slot lobes and the center round jet primarily occur in the immediate jet exit region, though residual effects are also found in the wake. Evaluation of the Reynold stresses aims to quantify the near region mixing between the jets collated geometric features and their interaction with the crossflow. Frequency analysis reveals that low-frequency harmonics in the wake region provide greater energy contributions than that of the higher-frequency harmonics found along the leading edge shear layer. This behavior is attributed to the low velocity ratio, where the freestream velocity is twice as large as the jet exit velocity. The experimental data and observations herein serve analogous computational modeling efforts for the slotted jet in crossflow at low velocity ratios, with ample information to inform necessary boundary conditions, fluid properties, and flow fields for validation.

关键词： Jet in Crossflow passive flow control Round Jet Slot Lobes Time-Resolved Particle Image Velocimetry Turbulent Jet Validation

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AN EXPERIMENTAL INVESTIGATION ONTO THE EFFECT OF TWO DESIGN METHODS OF LEADING-EDGE TUBERCLES ON THE AERODYNAMIC PERFORMANCE OF A HIGH LIFT AIRFOIL AT LOW REYNOLDS NUMBER

AN EXPERIMENTAL INVESTIGATION ONTO THE EFFECT OF TWO DESIGN ...

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ASME International Mechanical Engineering Congress and Exposition (IMECE)

作者： Khedr, Amr A. Adam, Ihab Ookawara, Shinichi El-Wardany, Ahmed Hassan, Hamdy Egypt Japan Univ Sci & Technol Alexandria Egypt Alexandria Univ Alexandria Dept Mech Engn Alexandria Egypt Tokyo Inst Technol Tokyo Japan

ISBN: (纸本)9780791885581

Inspired by the tubercles on the pectoral flipper leading-edge of the humpback whale, the most acrobatic of baleen whales, sinusoidal leading-edge have been used as a passive flow control method to enhance the stall characteristics of lifting surfaces in different applications. They are supposed to reduce the lift gradually during the stall with an increase in the post-stall lift, however, their enhancement ability in pre-and post-stall is highly dependent on the geometrical parameters and the flow regime. Two different design schemes: nonlinear shear transformation design scheme (NLST) and channelled-like scheme, of the sinusoidal leading edge of the high lift airfoil S1223 are tested and compared with the unmodified airfoil at angles of attack of -6 to 30 degrees experimentally inside a wind tunnel at low Reynolds number Re = 100,000. Experimental data show that Tubercles implemented on S1223 at such a flow regime with either design scheme enhance the post-stall characteristics as much as a 42% increase in lift at some angles for NLST with pre-stall lift penalties. NLST, compared with baseline and channelled models, exhibit a significant increase in aerodynamic efficiency which make it more preferable for wind turbines applications.

关键词： Bio-inspired Tubercles high lift airfoil wind turbine airfoil low Reynolds number laminar separation bubble passive flow control

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