scholarly journals Influence of Flanks on Resistance Performance of High-Speed Amphibious Vehicle

2021 ◽  
Vol 9 (11) ◽  
pp. 1260
Author(s):  
Dibo Pan ◽  
Xiaojun Xu ◽  
Bolong Liu
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Characteristic Parameters ◽  
Vehicle Model ◽  
Additional Resistance ◽  
Maximum Drag Reduction ◽  
Reduction Effect ◽  
Resistance Performance

In order to reduce the additional resistance of high-speed amphibious vehicles, Flanks are designed on the concave grooves. As a new drag reduction attachment, the principle of Flanks is analyzed and discussed in detail. In this paper, the HSAV model and Flanks coupling resistance tests are performed based on the Reynolds-averaged Navier–Stokes method and SST k−ω model. The accuracy of the numerical approach is verified by a series of towing tests. Results show that with a fixed installation angle and invariable characteristic parameters, Flanks can significantly reduce the total resistance at high speed, with a maximum drag reduction of 16%. In the meantime, Flanks also affect the attitude and flow field of the vehicle, consequently affecting the resistance composition and the sailing condition. A vehicle model self-propulsion test is designed and carried out, and it qualitatively verifies the drag reduction effect of the Flanks at high speed.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

scholarly journals An investigation on the drag reduction performance of bioinspired pipeline surfaces with transverse microgrooves

2020 ◽  
Vol 11 ◽  
pp. 24-40 ◽  
Author(s):  
Weili Liu ◽  
Hongjian Ni ◽  
Peng Wang ◽  
Yi Zhou
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Pressure Loss ◽  
Fluid Transport ◽  
Reduction Rate ◽  
Orthogonal Analysis ◽  
Maximum Drag Reduction ◽  
Reduction Effect ◽  
Save Energy ◽  
Microgrooved Surface

A novel surface morphology for pipelines using transverse microgrooves was proposed in order to reduce the pressure loss of fluid transport. Numerical simulation and experimental research efforts were undertaken to evaluate the drag reduction performance of these bionic pipelines. It was found that the vortex ‘cushioning’ and ‘driving’ effects produced by the vortexes in the microgrooves were the main reason for obtaining a drag reduction effect. The shear stress of the microgrooved surface was reduced significantly owing to the decline of the velocity gradient. Altogether, bionic pipelines achieved drag reduction effects both in a pipeline and in a concentric annulus flow model. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were obtained by an orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% could be achieved. The numerical simulation and experimental results were cross-checked and found to be consistent with each other, allowing to verify that the utilization of bionic theory to reduce the pressure loss of fluid transport is feasible. These results can provide theoretical guidance to save energy in pipeline transportations.

LDV Measurement of Turbulent Pipe Flow With Traveling Wavy Elastic Wall for Drag Reduction

2019 ◽  
Author(s):  
Seiya Nakazawa ◽  
Takaaki Shimura ◽  
Akihiko Mitsuishi ◽  
Kaoru Iwamoto ◽  
Akira Murata
Keyword(s):  
Drag Reduction ◽  
Pipe Flow ◽  
Reduction Rate ◽  
Streamwise Velocity ◽  
Turbulent Pipe Flow ◽  
Deformation Control ◽  
Wall Deformation ◽  
Maximum Drag Reduction ◽  
Reduction Effect ◽  
Ldv Measurement

Abstract Drag reduction effect by traveling wavy wall deformation control in turbulent pipe flow was experimentally investigated. From the visualization, we confirmed the downstream traveling wave although it was not uniform in the circumferential direction. When the frequency is 110 Hz, the wall deformation amplitude and the wavelength indicated that the effective values for drag reduction. The wavespeed is approximately effective values for drag reduction. As a result, the maximum drag reduction rate of 6.8 % is obtained. The result of a LDV measurement shows that the mean streamwise velocity gradient decreased near the wall by the control, which leads to drag reduction.

scholarly journals Numerical Investigations of Cavitation Nose Structure of a High-Speed Projectile Impact on Water-Entry Characteristics

2020 ◽  
Vol 8 (4) ◽  
pp. 265
Author(s):  
Qiang Li ◽  
Lin Lu
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Flow Characteristics ◽  
Water Entry ◽  
Navier Stokes ◽  
Cavitation Model ◽  
Lower Velocity ◽  
Numerical Investigations ◽  
Velocity Attenuation ◽  
Trajectory Stability

In this study, a detailed analysis of the influences of cavitation nose structure of a high-speed projectile on the trajectory stability during the water-entry process was investigated numerically. The Zwart-Gerber-Belamri (Z-G-B) cavitation model and the Shear Stress Ttransport (SST)k-ω turbulence model based on the Reynolds Averaged Navier–Stokes (RANS) method were employed. The numerical methodology was validated by comparing the numerical simulation results with the experimental photograph of cavitation shape and the experimental underwater velocity. Based on the numerical methodology, the disk and the conical cavitation noses were selected to investigate the water-entry characteristics. The influences of cavitation nose angle and cavitation nose diameter of the projectile on the trajectory stability and flow characteristics were carried out in detail. The variation features of projectile trajectory, velocity attenuation and drag were conducted, respectively. In addition, the cavitation characteristics of water-entry is presented and analyzed. Results show that the trajectory stability can be improved by increasing the cavitation nose angle, but the drag reduction performance will be reduced simultaneously. Additionally, due to the weakening of drag reduction performance, the lower velocity of the projectile will cause the damage of the cavitation shape and the trajectory instability. Furthermore, the conical cavitation nose has preferable trajectory stability and drag reduction performance than the disk cavitation nose.

scholarly journals Drag Reduction by Application of Aerodynamic Devices in a Race Car

2020 ◽  
Author(s):  
Devang S. Nath ◽  
Prashant Chandra Pujari ◽  
Amit Jain ◽  
Vikas Rastogi
Keyword(s):  
Drag Reduction ◽  
Drag Force ◽  
High Speed ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Fuel Prices ◽  
Race Car ◽  
High Speeds ◽  
Maximum Drag Reduction ◽  
Computational Fluid Dynamics Cfd

Abstract In this era of fast-depleting natural resources, the hike in fuel prices is ever-growing. With stringent norms over environmental policies, the automotive manufacturers are on a voyage to produce efficient vehicles with lower emissions. High-speed cars are at a stake to provide uncompromised performance but having strict rules over emissions drives the companies to approach through a different route to keep the demands of performance intact. One of the most sought-after ways is to improve the aerodynamics of the vehicles. Drag force is one of the major setbacks when it comes to achieving high speeds when the vehicle is in motion. This research aims to examine the effects of different add on devices on the vehicle to reduce drag and make the vehicle aerodynamically streamlined. A more streamlined vehicle will be able to achieve high speeds and consequently, the fuel economy is also improved. The three-dimensional car model is developed in SOLIDWORKS v17. Computational Fluid Dynamics (CFD) is performed to understand the effects of these add on devices. CFD is carried out in the ANSYSTM 17.0 Fluent module. Drag Coefficient (CD), Lift Coefficient (CL), Drag Force and Lift Force are calculated and compared in different cases. The result of the simulations were analyzed and it was observed that different devices posed several different functionalities, but maximum drag reduction was found in the case of GT with spoiler and diffuser with a maximum reduction of 16.53%.

scholarly journals Aerodynamic Drag Reduction and Optimization of MIRA Model Based on Plasma Actuator

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 64
Author(s):  
Chenguang Lai ◽  
Hang Fu ◽  
Bo Hu ◽  
Zhiwei Ling ◽  
Li Jiang
Keyword(s):  
Drag Reduction ◽  
Flow Control ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Active Flow Control ◽  
Plasma Actuator ◽  
Efficient Global Optimization ◽  
Driving Voltage ◽  
Control Effect ◽  
Reduction Effect

Active flow control of surface dielectric barrier discharge (SDBD) plasma is a technology that converts electrical energy into kinetic energy to achieve flow control. Its main application areas are concentrated in the aviation field. Undoubtedly, few studies have applied it in the field of automobile flow control. Meanwhile, during high-speed driving, there is a serious airflow separation phenomenon at the rear of notch-back cars, which brings a large area of negative pressure to the back of the cars. Due to the huge pressure difference between the front and end of the cars, it will increase the driving drag and fuel cost of the car. In this context, we seek to discuss the control effect on the airflow separation at the rear of the notch-back by using the phenomenological numerical simulation method of plasma flow control. Firstly, the plasma actuator is arranged separately on the rear end of the roof, c-pillar, upper and side of the trunk to study the control effect of airflow separation. After that, the plasma actuators at each position are combined and actuated simultaneously. We try to observe the control effect of airflow separation and select the combination with the best drag reduction effect. In the third stage, an efficient global optimization (EGO) algorithm based on kriging response surface is applied to optimize the supply voltage of the best combination that has been obtained before and obtain the driving voltage parameter of each actuator optimized under this combination. The results show that when plasma actuation is applied at four locations, only the actuation applied to the side of the luggage compartment has a significant drag reduction effect, while in other cases, the drag coefficient will increase. Specifically, drag reduction is better when the actuation is applied at four positions simultaneously. The maximum drag reduction coefficient of the car is reduced by 13.17%.

scholarly journals Drag reduction by application of aerodynamic devices in a race car

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Devang S. Nath ◽  
Prashant Chandra Pujari ◽  
Amit Jain ◽  
Vikas Rastogi
Keyword(s):  
Drag Reduction ◽  
Drag Force ◽  
High Speed ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Fuel Prices ◽  
Race Car ◽  
High Speeds ◽  
Maximum Drag Reduction ◽  
Computational Fluid Dynamics Cfd

AbstractIn this era of fast-depleting natural resources, the hike in fuel prices is ever-growing. With stringent norms over environmental policies, the automotive manufacturers are on a voyage to produce efficient vehicles with lower emissions. High-speed cars are at a stake to provide uncompromised performance but having strict rules over emissions drives the companies to approach through a different route to keep the demands of performance intact. One of the most sought-after ways is to improve the aerodynamics of the vehicles. Drag force is one of the major setbacks when it comes to achieving high speeds when the vehicle is in motion. This research aims to examine the effects of different add on devices on the vehicle to reduce drag and make the vehicle aerodynamically streamlined. A more streamlined vehicle will be able to achieve high speeds and consequently, the fuel economy is also improved. The three-dimensional car model is developed in SOLIDWORKS v17. Computational Fluid Dynamics (CFD) is performed to understand the effects of these add on devices. CFD is carried out in the ANSYS™ 17.0 Fluent module. Drag Coefficient (CD), Lift Coefficient (CL), Drag Force and Lift Force are calculated and compared in different cases. The result of the simulations was analyzed and it was observed that different devices posed several different functionalities, but maximum drag reduction was found in the case of GT with spoiler and diffuser with a maximum reduction of 16.53%.

scholarly journals Research on Control Technology of Jet and Rectifying Cone Combined Flow Field

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Hongqing Lv ◽  
Lei Xu ◽  
Zhenqing Wang ◽  
Xiaobin Zhang
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Drag Reduction ◽  
High Speed ◽  
Bluff Body ◽  
Hot Spot ◽  
Pressure Ratio ◽  
Main Flow ◽  
Control Technology ◽  
Reduction Effect

As an active flow field control technology, reverse jet and rectifier cone can significantly affect the flow field around the high-speed aircraft and reduce the drag and heat of high-speed aircraft to a certain extent. In this paper, the CFD numerical method is used to simulate and analyze the flow around the bluff body front rectifier cone and the reverse jet interference flow field. Further considering the combination of the two, the flow field structure around the bluff body under the combination of rectifying cone and reverse jet flow was simulated. Research shows, for the flow field of a single reverse jet, the pressure ratio of the reverse jet to the main flow has a significant effect on the drag reduction performance. With the change of the pressure ratio of the jet to the main flow, two modes of long jet and short jet will appear. The structure of the short jet modal flow field is relatively stable. However, with the increase of attack angle, the shear layer of free flow will attach to the shock wave and form hot spot, which is a great threat to high-speed aircraft. When the rectifier cone and the reverse jet are combined, within a certain angle of attack, the wall will not form a reattachment shock wave. The area behind the bow shock and in front of the aircraft head is a free-state zone, which has a good cooling effect on the aircraft head. At the same time, the static pressure on the wall is reduced, which has a very good drag reduction effect.

scholarly journals Numerical Study on Noise Reduction of High-Speed Train Based on Non-Smooth Surface

2020 ◽  
Author(s):  
Jiyou Huang ◽  
Haiyan Zhu ◽  
Haifei Wei ◽  
Junhai Huang ◽  
Qiying Xu
Keyword(s):  
Drag Reduction ◽  
Noise Reduction ◽  
High Speed ◽  
Smooth Surface ◽  
Numerical Study ◽  
Aerodynamic Resistance ◽  
Acoustic Power ◽  
Noise Model ◽  
High Speed Train ◽  
Reduction Effect

In this paper, a 350 km/h high-speed train is taken as the research object. Using the realizable k-ε model to calculate the steady-state flow field around the train, based on the results, calculating aerodynamic noise source of the train body surface by using the broadband noise model. The drag, lift and acoustic data of the train with the non-smooth surface units arranged on different positions of the vehicle are analyzed and compared, so as to analyze the influence of the layout of the non-smooth surface units on the drag reduction and noise reduction of the train. The simulation results show that when the non-smooth surface units are arranged in the bogie area, the aerodynamic resistance of the head and the intermediate vehicle can be effectively reduced, with the drag reduction effect of 12.2% in the head vehicle and 26.9% in the intermediate vehicle; when the non-smooth surface units are arranged on the nose of the train, for the intermediate vehicle, the drag reduction effect is 9.3%, and 11.5% when arranged on the transition area; when the non-smooth surface units are arranged on the nose of the train, there are quite a number of scattered points of low surface acoustic power in the streamline area of the tail vehicle, in which the lowest surface acoustic power level is only 50 dB, which is 25.3% lower than that of the train without non-smooth surface units.

Study on drag reduction mechanism of rotating disk with micro-grooves

2017 ◽  
Vol 232 (6) ◽  
pp. 660-673
Author(s):  
Suping Wen ◽  
Wenbo Wang ◽  
Jian Wang
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Viscous Sublayer ◽  
Dual Function ◽  
Reduction Mechanism ◽  
Smooth Disk ◽  
Reduction Effect ◽  
Interaction Phenomenon

This paper presents the drag reduction mechanism of a rotating disk with micro-grooves. The flow characteristics of the micro-grooved disk at various rotating Reynolds numbers are investigated using experiments and large-eddy simulations. The results show that fluid in the gap between the disks undergoes circumferential movement, but fluid within the micro-grooves undergoes radial movement because of the dual function of wall rejection and boundary layer blockage. As a result, fluid within the micro-grooves moves very slowly and quietly. Hence, quiet and slow-moving fluid within the micro-grooves increases the thickness of the viscous sublayer and recedes mixed layer and suppresses the unstable motion. The mean relative velocity gradient of the immersed surface on the grooved disk becomes much lower than that of a smooth disk, and the contact area between the walls and the high-speed fluid is diminished. An interaction phenomenon between the micro-grooves and the gap could be discovered due to the micro-groove unenclosed structure. The interaction phenomenon makes the quiet fluid within the micro-grooves also suppresses the outside flow. Accordingly, a micro-grooved rotating disk has an obvious drag reduction effect compared with a rotating smooth disk.

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