scholarly journals Bluff body drag manipulation using pulsed jets and Coanda effect

2016 ◽  
Vol 805 ◽  
pp. 422-459 ◽  
Author(s):  
Diogo Barros ◽  
Jacques Borée ◽  
Bernd R. Noack ◽  
Andreas Spohn ◽  
Tony Ruiz
Keyword(s):  
Bluff Body ◽  
Three Dimensional ◽  
Base Pressure ◽  
Coanda Effect ◽  
Wake Time ◽  
Recirculating Flow ◽  
Flow Deviation ◽  
Coandǎ Effect ◽  
And Control ◽  
The Impact

The impact of fluidic actuation on the wake and drag of a three-dimensional blunt body is investigated experimentally. Jets blowing tangentially to the main flow force the wake with variable frequency and amplitude. Depending on the forcing conditions, two flow regimes can be distinguished. First, in the case of broadband actuation with frequencies comprising the natural wake time scale, the convection of the jet structures enhances wake entrainment, shortens the length of the recirculating flow and increases drag. Secondly, at higher actuation frequencies, shear-layer deviation leads to fluidic boat tailing of the wake. It additionally lowers its turbulent kinetic energy thus reducing the entrainment of momentum towards the recirculating flow. The combination of both mechanisms produces a rise in the base pressure and reduces the drag of the model. Both actuation regimes are characterized by complementary velocity, pressure and drag measurements at several upstream conditions and control parameters. By adding curved surfaces to deviate the jets by the Coanda effect, periodic actuation is reinforced and drag reductions of approximately 20 % are achieved. The unsteady Coanda blowing not only intensifies the flow deviation and the base pressure recovery but also preserves the unsteady high-frequency forcing effect on the turbulent field. The present results encourage further development of fluidic control to improve the aerodynamics of road vehicles and provide a complementary insight into the relation between wake dynamics and drag.

Design Optimization, Modeling, and Control of Unmanned Aerial Vehicle Lifted By Coandă Effect

2017 ◽  
Vol 22 (3) ◽  
pp. 1327-1336 ◽  
Author(s):  
Hyunyong Lee ◽  
Seonhye Han ◽  
Hyoju Lee ◽  
Jaehyeok Jeon ◽  
Choonghan Lee ◽  
...  
Keyword(s):  
Design Optimization ◽  
Unmanned Aerial Vehicle ◽  
Coanda Effect ◽  
Optimization Modeling ◽  
Modeling And Control ◽  
Aerial Vehicle ◽  
Coandǎ Effect ◽  
And Control

scholarly journals On the recirculating flow of three-dimensional asymmetric bluff bodies

2020 ◽  
Vol 61 (12) ◽  
Author(s):  
Antoine Legeai ◽  
Olivier Cadot
Keyword(s):  
Bluff Body ◽  
Reference Model ◽  
Three Dimensional ◽  
Bluff Bodies ◽  
Recirculating Flow ◽  
Bistable Dynamics ◽  
Geometrical Variation ◽  
Static Instability ◽  
State Selection

Abstract The paper investigates the role of geometrical asymmetric modifications of a rectangular flat-backed body on the properties of the recirculating flow at a Reynolds number $$Re=1.8\times 10^5$$ R e = 1.8 × 10 5 . The reference model has two reflectional symmetries denoted $$s_y$$ s y and $$s_z$$ s z in both spanwise directions. The flow is subjected to the static instability that leads to two mirrored wake states breaking the symmetry $$s_y$$ s y . Two families of geometrical variation of the fore-body and after-body are studied, each breaking one of the reflectional symmetries of the reference model. Geometrical modifications that preserve $$s_y$$ s y evidence possibilities of bistable dynamics suppression although the static instability persists. Geometrical modifications that do not preserve $$s_y$$ s y produces a large unbalance of both wake states in accordance to recent observations on real cars (Bonnavion et al. in J Wind Eng Ind Aerodyn 184:77–89, 2019). Results offer perspectives for potential drag reduction induced by appropriate coupling of bluff body geometry and wake state selection. Graphic abstract

Coanda Effect on the Impact of Distribution Characteristics of Oil-Air Annular Flow

2014 ◽  
Vol 620 ◽  
pp. 166-170
Author(s):  
Qi Guo Sun ◽  
Dong Xu Chen ◽  
Xiong Shi Wang ◽  
Zheng Hui Zhou
Keyword(s):  
Pressure Gradient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Annular Flow ◽  
Branch Pipe ◽  
Coanda Effect ◽  
Distribution Characteristics ◽  
Coandǎ Effect ◽  
The Impact

The T-junction model is simulated in Fluent by changing the curvature of branch pipe, and then the distribution characteristics of the annular flow was studied in T-junction distributor. The mass flow and pressure of the annular flow in this T-junction are studied, and the impact of Coanda Effect on the annular flow distribution characteristic is analyzed in oil-air two phases flow. The results show that, Coanda Effect affects the distribution of oil-air annular flow unevenly. The mass flow rate of air phase and the air velocity of outlet increase with decreasing the curvature, while the mass flow rate of liquid decrease with decreasing the curvature of the branch pipe connection; T-shaped junction inlet pressure is high, but the pressure gradient is small, the pressure gradient in the small curvature manifold is larger than that in the large curvature manifold.

A novel valveless piezoelectric micropump with a bluff-body based on Coanda effect

2018 ◽  
Vol 25 (7) ◽  
pp. 2637-2647 ◽  
Author(s):  
Xiuhua He ◽  
Rongqun Bian ◽  
Nan Lin ◽  
Wei Xu ◽  
Zhidan Deng ◽  
...  
Keyword(s):  
Bluff Body ◽  
Coanda Effect ◽  
Coandǎ Effect

A study of three-dimensional aspects of vortex shedding from a bluff body with a mild geometric disturbance

1997 ◽  
Vol 330 ◽  
pp. 85-112 ◽  
Author(s):  
N. TOMBAZIS ◽  
P. W. BEARMAN
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Base Pressure ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Trailing Edges ◽  
Mode Transitions

Experiments have been carried out to study the three-dimensional characteristics of vortex shedding from a half-ellipse shape with a blunt trailing edge. In order to control the occurrence of vortex dislocations, the trailing edges of the models used were constructed with a series of periodic waves across their spans. Flow visualization was carried out in a water tunnel at a Reynolds number of 2500, based on trailing-edge thickness. A number of shedding modes were observed and the sequence of mode transitions recorded. Quantitative data were obtained from wind tunnel measurements performed at a Reynolds number of 40000. Two shedding frequencies were recorded with the higher frequency occurring at spanwise positions coinciding with minima in the chord. At these same positions the base pressure was lowest and the vortex formation length longest. Arguments are put forward to explain these observations. It is shown that the concept of a universal Strouhal number holds, even when the flow is three-dimensional. The spanwise variation in time-average base pressure is predicted using the estimated amount of time the flow spends at the two shedding frequencies.

Modeling and control of a saucer type Coandä effect UAV

2017 ◽  
Author(s):  
Jameson Y. Lee ◽  
Seung Hwan Song ◽  
Hyun Wook Shon ◽  
Hyouk Ryeol Choi ◽  
Woosoon Yim
Keyword(s):  
Coanda Effect ◽  
Modeling And Control ◽  
Coandǎ Effect ◽  
And Control

Three-dimensional vortex interactions with a stationary blade

1999 ◽  
Vol 103 (1030) ◽  
pp. 579-588 ◽  
Author(s):  
C. J. Doolan ◽  
F. N. Coton ◽  
R. A. McD. Galbraith
Keyword(s):  
Three Dimensional ◽  
Lower Surface ◽  
Impulsive Loading ◽  
Axial Component ◽  
Core Flow ◽  
Vortex Interactions ◽  
Rapid Changes ◽  
Naca 0015 ◽  
And Control ◽  
The Impact

Abstract Surface pressure measurements were obtained during a three-dimensional vortex interaction with a NACA 0015 aerofoil. The upper and lower surfaces of the blade experienced different aerodynamic loads which appear to be controlled by the impact of the vortex axial core flow on the blade surface. On the upper surface of the blade, where the vortex core flow was away from the aerofoil, the interaction was characterised by the generation of a suction peak. On the lower surface, where the axial component was towards the blade, a pressure pulse developed and seemed to be influenced by the vortex approach angle. These features resulted in rapid changes in normal force and quarter chord pitching moment during the interaction. This impulsive loading of the blade may provide some explanation for sound generation and control degradation problems associated with the tail rotor of helicopters.

Thermal Management Simulation of Lithium Ion Batteries for EV/HEV

2013 ◽  
Vol 457-458 ◽  
pp. 350-353
Author(s):  
Fofana Gaoussou Hadia ◽  
You Tong Zhang
Keyword(s):  
Lithium Ion Batteries ◽  
Heat Generation ◽  
Fundamental Problem ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Lithium Ion ◽  
Form Solution ◽  
Mechanism Analysis ◽  
And Control ◽  
The Impact

In this paper, we propose a three-dimensional analytical model based on Greens Function to investigate the Impact of temperature rising on simple lithium-ion batteries and control the heat generation during charge/discharge of battery operation. The modeling is based on heat-transform mechanism analysis method that gives a closed-form solution for the fundamental problem of heat conduction in battery cores with orthotropic thermal conductivities. The method uses a simple lithium-ion battery examined, considered the ambient temperature and initial temperature as 25°C, subjected to transient heat generation in various convective cooling boundary conditions at its surfaces.

A method to measure three-dimensional substratum rugosity for ecological studies: an example from the date-mussel fishery desertification in the north-western Mediterranean

2006 ◽  
Vol 86 (4) ◽  
pp. 689-690 ◽  
Author(s):  
Valeriano Parravicini ◽  
Alessio Rovere ◽  
Marco Donato ◽  
Carlo Morri ◽  
Carlo Nike Bianchi
Keyword(s):  
Analysis Of Variance ◽  
Three Dimensional ◽  
Western Mediterranean ◽  
Ecological Studies ◽  
The North ◽  
And Control ◽  
The Impact ◽  
North Western ◽  
Italian Coast

The impact of date-mussel fishery on substratum rugosity was evaluated at Capo Noli and Isola di Bergeggi (Savona, north-western Italian coast) in the summer of 2004. A new measure of substratum rugosity was used as a surface-dependent index of complexity. The results were compared between impact and control sites using two-way analysis of variance and suggested that the mussel fishery reduces substratum complexity.

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