scholarly journals Wake Structures and Surface Patterns of the DrivAer Notchback Car Model under Side Wind Conditions

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 320 ◽  
Author(s):  
Dirk Wieser ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit
Keyword(s):  
Flow Field ◽  
Aerodynamic Force ◽  
Middle Part ◽  
Surface Flow ◽  
Stereoscopic Particle Image Velocimetry ◽  
Ring Vortex ◽  
Particle Image Velocimetry System ◽  
Rear Window ◽  
Base Surface ◽  
Surface Patterns

The flow field topology of passenger cars considerably changes under side wind conditions. This changes the surface pressure, aerodynamic force, and drag and performance of a vehicle. In this study, the flow field of a generic passenger vehicle is investigated based on three different side wind angles. The study aimed to identify vortical structures causing changes in the rear pressure distribution. The notchback section of the DrivAer model is evaluated on a scale of 1:4. The wind tunnel tests are conducted in a closed section with a splitter plate at a Reynolds number of 3 million. The side wind angles are 0 ∘ , 5 ∘ , and 10 ∘ . The three-dimensional and time-averaged flow field downstream direction of the model is captured by a stereoscopic particle image velocimetry system performed at several measurement planes. These flow field data are complemented by surface flow visualizations performed on the entire model. The combined approaches provide a comprehensive insight into the flow field at the frontal and side wind inflows. The flow without side wind is almost symmetrical. Longitudinal vortices are evident along the downstream direction of the A-pillar, the C-pillars, the middle part of the rear window, and the base surface. In addition, there is a ring vortex downstream of the vehicle base. The side wind completely changes the flow field. The asymmetric topology is dominated by the windward C-pillar vortex, the leeward A-pillar vortex, and other base vortices. Based on the location of the vortices and the pressure distributions measured in earlier studies, it can be concluded that the vortices identified in the wake are responsible for the local minima of pressure, increasing the vehicle drag.

Influence of propeller slipstream on vortex flow field over a typical micro air vehicle

2016 ◽  
Vol 121 (1235) ◽  
pp. 95-113 ◽  
Author(s):  
S. Sudhakar ◽  
A. Chandankumar ◽  
L. Venkatakrishnan
Keyword(s):  
Flow Field ◽  
Vortex Flow ◽  
Surface Flow ◽  
Micro Air Vehicle ◽  
Stereoscopic Particle Image Velocimetry ◽  
Flow Visualisation ◽  
Flow Topology ◽  
Freestream Velocity ◽  
Air Vehicle ◽  
Oil Flow

ABSTRACTAn experimental study has been carried out to explore the effect of propeller-induced slipstream on the vortex flow field on a fixed-wing Micro Air Vehicle (MAV). Experiments were conducted at a freestream velocity of 10 m/s, corresponding to a Reynolds number based on a root chord of about 1.6 × 105. Surface flow topology on the surface of the MAV wing at propeller-off and propeller-on conditions was captured using surface oil flow visualisation at four angles of incidence. The mean off-body flow over the MAV was documented in the four spanwise planes at different chord position using Stereoscopic Particle Image Velocimetry (SPIV) technique at angle-of-attack of 24° for both conditions. The oil flow visualisation showed minimal differences in flow patterns for propeller-off and propeller-on conditions at 10° and 15° incidence. The small asymmetry between port and starboard side observed at 20° during the propeller-off condition became significantly pronounced at 24°. The fuselage stub which is necessary for housing the motor of the propeller was seen to have a significant effect on the flow symmetry at large incidences that can occur when the MAV encounters sudden vertical gusts. Switching on the propeller restored the symmetry at both incidences. SPIV measurements were carried out at the incidence of 24° which exhibited the highest asymmetry. The off-body data shows the re-establishment of symmetry during propeller-on condition owing to the increase in the magnitude of spanwise and vertical velocities as a result of the propeller slipstream. The findings emphasise the importance of considering the propeller flow and design of the motor housing while evaluating the aerodynamics of low-aspect-ratio MAVs.

Experimental and Numerical Study on the Flow Field Around a Parallel-Foil Turbine

2020 ◽  
Author(s):  
Yulu Wang ◽  
Di Zhang ◽  
Yonghui Xie
Keyword(s):  
Flow Field ◽  
Aerodynamic Force ◽  
Numerical Study ◽  
Energy Extraction ◽  
Reduced Frequency ◽  
Image Velocimetry ◽  
Efficiency Increase ◽  
Oscillation Process ◽  
Effective Angle ◽  
Extraction Performance

Abstract An experiment facility of parallel-foil turbine is proposed in this study. The flow field around foils at different reduced frequency, pitching amplitude and plunging amplitude is measured by 2D Particle Image Velocimetry (PIV) system. And the energy extraction performance at different motion parameters is analyzed numerically. The comparison between experimental and numerical flow field is conducted at different reduced frequency. The evolution of flow field and the aerodynamic force with different pitching amplitude and plunging amplitude are discussed. The effect of pitching amplitude and plunging amplitude on energy extraction performance is obtained. Results indicate that the pitching amplitude can increase the range and the strength of acceleration area by varying the pitching velocity and the effective angle of attack. The optimal extraction performance appears at 70°. Due to the increase in plunging amplitude, the energy extraction performance and efficiency increase gradually. The optimal plunging amplitude is 1.0. The pitching amplitude and the plunging amplitude influence the power output by affecting the vortex shedding and the flow reattachment in oscillation process.

scholarly journals Three-dimensional hydrodynamics numerical of wind-driven circulations in Danjiangkou Reservoir

2018 ◽  
Vol 246 ◽  
pp. 02021
Author(s):  
Jie Zhu ◽  
Jin Quan ◽  
Xiaohui Lei ◽  
Xia Yue ◽  
Yang Duan
Keyword(s):  
Wind Speed ◽  
Flow Field ◽  
Potential Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Surface Flow ◽  
Surface Velocity ◽  
Wind Condition ◽  
Reservoir Area ◽  
Danjiangkou Reservoir

This paper focuses on the analysis of the flow field of Danjiangkou Reservoir under the action of wind stress. Based on the analysis of the annual wind field data of Danjiangkou Reservoir, the three-dimensional hydrodynamic model of Danjiangkou Reservoir was established. The distribution of water flow field in the reservoir area under five different wind directions and two different wind speeds was studied. The simulation results were compared with the flow field without wind. The results show that when the wind speed in the reservoir area is 3.3m/s, the surface velocity and flow direction change less under the same wind conditions as the potential flow direction. Under the wind condition opposite to the potential flow direction, the reservoir area is locally generated. The small circulation and surface flow are more disordered; when the wind speed reaches 10.0m/s, under the same wind condition as the potential flow direction, the surface velocity of the reservoir area increases significantly. Under the wind condition opposite to the direction of the potential flow, a stable counterclockwise circulation is generated, and the wind direction dominates the surface layer. seriously affecting the flow field distribution in the reservoir area. The research results in this paper can provide support for the reservoir in the formulation of emergency water pollution emergency strategy and the formulation of real-time scheduling plan.

Particle image velocimetry investigation on air distribution of surface-source buoyancy plume changing heating intensity and structure size in a thermostatic chamber

2020 ◽  
pp. 1420326X2092624
Author(s):  
Xin Wang ◽  
Yukun Xu ◽  
Yinchen Yang ◽  
Bingyan Song
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Axial Velocity ◽  
Particle Image ◽  
Source Parameters ◽  
Air Distribution ◽  
Particle Image Velocimetry System ◽  
Surface Source ◽  
Large Space ◽  
Image Velocimetry

For large space buildings like industrial plants with huge heat generation, the role that surface-source plumes play becomes more crucial. To study the air distribution and movement of plumes, the first step is to quantify how the airflow gets distributed in chambers. The experiment was carried out in a thermostatic chamber where there was no ventilation. Four hundred flow field snapshots (in each region) were measured by a two-dimensional particle image velocimetry system at a sampling frequency of 3 Hz, and the time-average flow field was processed by the adaptive correlation algorithm to quantify the air distribution of the plume. According to the measured data, the variation law of the axial velocity of the surface-source plume under different heat source parameters was analysed. The formula coefficients of the axial velocity, the extended radius and the mass flow of the plume were discussed, and the coefficients from current two mainstream methods and those obtained in this paper were compared. The results of this study will be useful to predict motion of surface-plumes and optimize airflow patterns in large spaces.

Visualization of the flow field and aerodynamic force on a Horizontal Axis Wind Turbine in turbulent inflows

Energy ◽  
2016 ◽  
Vol 111 ◽  
pp. 57-67 ◽  
Author(s):  
Qing'an Li ◽  
Yasunari Kamada ◽  
Takao Maeda ◽  
Junsuke Murata ◽  
Yusuke Nishida
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Aerodynamic Force ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbine

Performance characteristics of axial flow hydraulic turbine with a collection device in free surface flow field

2017 ◽  
Vol 112 ◽  
pp. 53-62 ◽  
Author(s):  
Yasuyuki Nishi ◽  
Genki Sato ◽  
Daishi Shiohara ◽  
Terumi Inagaki ◽  
Norio Kikuchi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Axial Flow ◽  
Free Surface Flow ◽  
Hydraulic Turbine ◽  
Surface Flow ◽  
Performance Characteristics ◽  
Collection Device

Aerodynamic Simulation of Road Vehicle in Steady Crosswind

2013 ◽  
Vol 376 ◽  
pp. 341-344
Author(s):  
Shan Ling Han ◽  
Ru Xing Yu ◽  
Yu Yue Wang ◽  
Gui Shen Wang
Keyword(s):  
Flow Field ◽  
Wind Direction ◽  
Motor Vehicle ◽  
Aerodynamic Force ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
External Flow ◽  
Slant Angle ◽  
Ahmed Body

Because crosswind affects drivers to control their vehicles safely, the research on flow characteristics in automotive crosswind has a great significance to improve the crosswind stability of the vehicle. By the steady state numerical simulation method, the aerodynamic characteristics of external flow field of Ahmed body in crosswind was investigated. The Ahmed body with 25° slant angle is built in UG NX. The external flow field of the Ahmed body in the wind direction of 0°, 15º, 30° angle is simulated in XFlow software. According to the map of the pressure and velocity distribution, the flow field both before and after, as well as left and right has significant change as the wind direction angle increased, and the trail turbulence intensity also changes. The changes of aerodynamic force and moment affect the driving stability of a motor vehicle.

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