scholarly journals Control of Sunroof Buffeting Noise by Optimizing the Flow Field Characteristics of a Commercial Vehicle

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1052
Author(s):  
Rongjiang Tang ◽  
Hongbin He ◽  
Zengjun Lu ◽  
Shenfang Li ◽  
Enyong Xu ◽  
...  
Keyword(s):  
Flow Field ◽  
Commercial Vehicle ◽  
Resistance Coefficient ◽  
Local Pressure ◽  
Turbulent Vortex ◽  
Pressure Drag ◽  
Eddy Simulation ◽  
Flow Field Characteristics ◽  
Potential Applicability ◽  
Sunroof Buffeting Noise

When a commercial vehicle is driving with the sunroof open, it is easy for the problem of sunroof buffeting noise to occur. This paper establishes the basis for the design of a commercial vehicle model that solves the problem of sunroof buffeting noise, which is based on computational fluid dynamics (CFD) numerical simulation technology. The large eddy simulation (LES) method was used to analyze the characteristics of the buffeting noise with different speed conditions while the sunroof was open. The simulation results showed that the small vortex generated in the cab forehead merges into a large vortex during the backward movement, and the turbulent vortex causes a resonance response in the cab cavity as the turbulent vortex moves above the sunroof and falls into the cab. Improving the flow field characteristics above the cab can reduce the sunroof buffeting noise. Focusing on the buffeting noise of commercial vehicles, it is proposed that the existing accessories, including sun visors and roof domes, are optimized to deal with the problem of sunroof buffeting noise. The sound pressure level of the sunroof buffeting noise was reduced by 6.7 dB after optimization. At the same time, the local pressure drag of the commercial vehicle was reduced, and the wind resistance coefficient was reduced by 1.55% compared to the original commercial vehicle. These results can be considered as relevant, with high potential applicability, within this field of research.

scholarly journals Comparison of conventional Lagrangian stochastic footprint models against LES driven footprint estimates

2009 ◽  
Vol 9 (15) ◽  
pp. 5575-5586 ◽  
Author(s):  
T. Markkanen ◽  
G. Steinfeld ◽  
N. Kljun ◽  
S. Raasch ◽  
T. Foken
Keyword(s):  
Flow Field ◽  
Model Comparison ◽  
Comparison Method ◽  
Flux Footprint ◽  
Footprint Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Field Characteristics ◽  
Unstable Case ◽  
Conventional Models

Abstract. In this study we introduce a comparison method for footprint model results by evaluating the performance of conventional Lagrangian stochastic (LS) footprint models that use parameterised flow field characteristics with results of a Lagrangian trajectory model embedded in a large eddy simulation (LES) framework. The two conventional models follow the particles backward and forward in time while the trajectories in LES only evolve forward in time. We assess their performance in two unstably stratified boundary layers at observation levels covering the whole depth of the atmospheric boundary layer. We present a concept for footprint model comparison that can be applied for 2-D footprints and demonstrate that comparison of only cross wind integrated footprints is not sufficient for purposes facilitating two dimensional footprint information. Because the flow field description among the three models is most realistic in LES we use those results as the reference in the comparison. We found that the agreement of the two conventional models against the LES is generally better for intermediate measurement heights and for the more unstable case, whereas the two conventional flux footprint models agree best under less unstable conditions. The model comparison in 2-D was found quite sensitive to the grid resolution.

scholarly journals Large Eddy Simulation of Self-Excited Oscillation Pulsed Jet (SEOPJ) Induced by a Helmholtz Oscillator in Underground Mining

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2161 ◽  
Author(s):  
Zhenlong Fang ◽  
Qiang Wu ◽  
Mengda Zhang ◽  
Haoyang Liu ◽  
Pan Jiang ◽  
...  
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Coherent Structure ◽  
Underground Mining ◽  
Operating Pressure ◽  
Mean Flow ◽  
The Core ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Field Characteristics

Pulsed waterjet can break rocks effectively by taking advantage of the water hammer effect, and is thus widely used in mining, petroleum, and natural gas fields. With the aim to further clarify the flow field characteristics of pulsed jets induced by a Helmholtz oscillator, large eddy simulation was conducted under different operating pressures. The velocity distribution, mean flow field, and the coherent structure were examined using the oscillators of different cavity lengths and diameters. The results clearly showed that the major frequency of jet pulsation gradually increased with the increase of operating pressure. A stable periodic velocity core was formed at the outlet of the Helmholtz oscillator, while the external flow field was subjected to periodic impact. As a result, the ambient fluid was strongly entrained into the jet beam. With the increase of the cavity length, the length of the core segment decreased while the energy loss caused by the cavity increased, which was also accompanied by a rapid attenuation of the axial velocity at the jet outlet. The coherent structure of the jet in the oscillator with small cavity diameter was more disordered near the nozzle outlet, and the vortex scale was larger. The effect of cavity diameter can be reflected in the feedback modulation of the jet in the cavity. Compared with the conical nozzle, the length of the core section of the jet was shorter, but the jet had better bunching, a smaller diffusion angle, and better mixing performance. These results provide a further understanding of the characteristics of pulsed water jet for better utilizations in the fields of energy exploitation.

scholarly journals Validation of conventional Lagrangian stochastic footprint models against LES driven footprint estimates

2009 ◽  
Vol 9 (1) ◽  
pp. 4195-4230
Author(s):  
T. Markkanen ◽  
G. Steinfeld ◽  
N. Kljun ◽  
S. Raasch ◽  
T. Foken
Keyword(s):  
Flow Field ◽  
Model Comparison ◽  
Flux Footprint ◽  
Footprint Model ◽  
Lagrangian Trajectory ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Field Characteristics ◽  
Conventional Models ◽  
Neutral Conditions

Abstract. In this study we compare the performance of conventional Lagrangian stochastic (LS) footprint models that use parameterised flow field characteristics with results of a Lagrangian trajectory model embedded in a large eddy simulation (LES) framework. The two conventional models follow the particles backward and forward in time while the trajectories in LES only evolve forward in time. We assess their performance in unstably and neutrally stratified boundary layers at observation levels covering the whole depth of the atmospheric boundary layer. We present a concept for footprint model comparison that can be applied for 2-D footprints and demonstrate that comparison of only cross wind integrated footprints is not sufficient for purposes facilitating two dimensional footprint information. Because the flow field description among the three models is most realistic in LES we use those results as the reference in the comparison. We found that the agreement of the two conventional models against the LES is generally better for intermediate measurement heights and for the convective case, whereas the two conventional flux footprint models agree best under near neutral conditions.

scholarly journals Large Eddy Simulation and Flow Field Analysis of Car on the Bridge under Turbulent Crosswind

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Juyue Ding ◽  
Weitan Yin ◽  
Yongqi Ma
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Wind Tunnel Test ◽  
Simulation Method ◽  
Field Analysis ◽  
Long Span Bridges ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Field Characteristics

As more long-span bridges continue to be completed and opened to traffic, the safety of cars driving across the bridge has attracted more and more attention, especially when the car is suddenly affected by the crosswind, the car is likely to have direction deviation or even a rollover accident. In this paper, the large eddy simulation method is used to study the flow field characteristics and safety of the car on the bridge under the turbulent crosswind. The numerical simulation model is established by referring to the Donghai Bridge, and the correctness of the car model is validated by combining with the data of wind tunnel test. The influence of factors such as the porosity and height of the bridge guardrail and the Reynolds number of airflow on the flow field characteristics is analyzed. The study shows that, in order to ensure the safety of cars on the bridge, the bridge guardrail porosity should be small, 35.8% is more suitable, the guardrail height should be more suitable within the range of 1.5–1.625 meters, and the Reynolds number should not be 3.51e + 5. The research results of this paper will provide reference for the optimal design of bridge guardrail.

Analysis of flow field characteristics and structure optimization of the split-stream rushing muffler for diesel engine

2020 ◽  
Vol 68 (1) ◽  
pp. 101-111 ◽  
Author(s):  
He Su ◽  
Pei Wu ◽  
Jing Xue ◽  
Yongan Zhang ◽  
Haijun Zhang
Keyword(s):  
Theoretical Model ◽  
Diesel Engine ◽  
Flow Field ◽  
Pressure Loss ◽  
Transmission Loss ◽  
Engineering Application ◽  
Structure Optimization ◽  
Resistance Coefficient ◽  
Tracer Test ◽  
Flow Field Characteristics

In order to analyze the flow field characteristics of the split-stream rushing muffler, a theoretical model describing the velocity of the split streams is established and verified by the tracer test. For this new-principle muffler, the acoustic performance and the relationship between the velocity drop of the airflow and the pressure field are analyzed, also the structure optimization of the muffler is carried out based on the orthogonal test. Finally, a new muffler is fabricated based on the designing theory of this type of muffler for a prototype of diesel engine, and the comparative analyses are conducted compared with its original muffler. The results show that the establishment and analysis of the theoretical model for velocity during the split-streams rushing process are correct. In the frequency range of 0â–“1000 Hz, the average transmission loss of split-stream rushing muffler is better than that of the original muffler. While the speed of airflow is reduced by split-streams rushing, a certain pressure loss is caused at the same time, which is about 50% of total pressure loss of the muffler, and the average fluid resistance coefficient of the split-stream rushing process is 0.91. Compared to the original muffler of the sample engine, the average insertion loss of the optimized new muffler is increased by 61.2%. At inlet air velocity of 30 m/s, the pressure loss is reduced by 16.8%. The results provide a potential for practical engineering application of this new split-stream rushing muffler in future.

Investigation on Influence of Launch Depth to the Hydrodynamic Characteristics of the Cylinder out of the Tube

2011 ◽  
Vol 328-330 ◽  
pp. 2261-2264
Author(s):  
Hai Jun Liu ◽  
Xing Zhi Peng ◽  
Cong Wang ◽  
Ben Li Wang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Resistance Coefficient ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Multiphase Model ◽  
Pressure Drag ◽  
Simulation Results ◽  
Volume Method ◽  
Mesh Technique

The influence of different the depth to the hydrodynamic characteristics of the underwater cylinder vertical launch out of the tube was researched with numerical simulation. The finite volume method based on the multiphase model, continuity equation, transport equations of liquid mass fraction,a dynamic mesh technique and a standard tow-turbulence model are adopted to solve RANS equation in conjunction. The fluid-solid coupling problem of both movement boundary of the cylinder and multiphase flow field was solved by using numerical method. Under the influence of the gravity, the flow field affected the hydrodynamic characteristics of the cylinder was derived with the numerical simulation. Simulation results show that different launch depths affect on the trajectory of underwater cylinder and hydrodynamic. The fluctuation reasons of different pressure drag coefficient, viscous drag resistance coefficient and toll resistance coefficient were derived by analyzing simulation results.

scholarly journals Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 97
Author(s):  
Junfeng Sun ◽  
Meihong Liu ◽  
Zhen Xu ◽  
Taohong Liao ◽  
Xiangping Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Thickness ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
High Rotational Speed ◽  
Flexible Support ◽  
Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

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