Drag Reduction on the 25-deg Ahmed Model Using Fluidic Oscillators

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Matthew Metka ◽  
James W. Gregory
Keyword(s):  
Drag Reduction ◽  
Moving Objects ◽  
Ground Vehicle ◽  
Flow Energy ◽  
Structure Changes ◽  
Slant Surface ◽  
Oil Flow ◽  
Oscillating Jet ◽  
Oil Flow Visualization ◽  
Model Oil

Transportation of goods and people involves moving objects through air, which leads to a force opposing motion. This drag force can account for more than 60% of power consumed by a ground vehicle, such as a car or truck, at highway speeds. This paper studies drag reduction on the 25-deg Ahmed generic vehicle model with quasi-steady blowing at the roof–slant interface using a spanwise array of fluidic oscillators. A fluidic oscillator is a simple device that converts a steady pressure input into a spatially oscillating jet. Drag reduction near 7% was attributed to separation control on the rear slant surface. Particle image velocimetry (PIV) and pressure taps were used to characterize the flow structure changes behind the model. Oil flow visualization was used to understand the mechanism behind oscillator effectiveness. An energy analysis suggests that this method may be viable from a flow energy perspective.

Drag Reduction and Velocity Profiles Distribution of Crude Oil Flow in Spiral Pipes

2015 ◽  
Vol 9 (1) ◽  
pp. 1 ◽  
Author(s):  
Yanuar Yanuar ◽  
Kurniawan T. Waskito ◽  
Gunawan Gunawan ◽  
Budiarso Budiarso
Keyword(s):  
Drag Reduction ◽  
Crude Oil ◽  
Velocity Profiles ◽  
Oil Flow

Effects of Freestream Turbulence on the Losses of a Highly-Loaded Compressor Stator Blade

2003 ◽  
Author(s):  
J. W. Douglas ◽  
S.-M. Li ◽  
B. Song ◽  
W. F. Ng ◽  
Toyotaka Sonoda ◽  
...  
Keyword(s):  
Turbulence Intensity ◽  
Flow Separation ◽  
Reynolds Numbers ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Flow Losses ◽  
Oil Flow ◽  
Oil Flow Visualization ◽  
Inlet Conditions ◽  
High Reynolds

Very little published literature documents the effects of different freestream turbulence intensities on compressor flows at realistically high Reynolds numbers. This paper presents a study of these effects on a transonic, linear, compressor stator cascade. The cascade consisted of high turning stator airfoils that had the camber of 55 degrees. The effects of freestream turbulence intensities of approximately 0.1% (baseline) and 1.6% were examined. Inlet Mach numbers to the cascade were tested from 0.55 to 0.89. Reynolds numbers, based on the inlet conditions and blade chord, varied between 1.0–2.0×106. Inlet flow angles to the cascade ranged from a choking to a stall condition. For the baseline cases, at most positive incidence angles to the cascade, surface oil flow visualization and Schlieren pictures showed a significant flow separation on the suction surface of the blade. Under these conditions, the increase in freestream turbulence from 0.1% to 1.6% significantly reduced the flow losses of the cascade (by as much as 57% in some cases). In other test conditions where no evidence depicted flow separation on the blade, there were no measurable effects on the losses due to the increase in freestream turbulence intensity. In addition, the increase of freestream turbulence intensity also improved the effective operating range of the cascade significantly (e.g., by 46% or higher).

Experimental investigation of plasma vortex generator in flow control

2018 ◽  
Vol 92 (3) ◽  
pp. 376-385
Author(s):  
Alireza Ghayour ◽  
Mahmoud Mani
Keyword(s):  
Vortex Generator ◽  
Leading Edge ◽  
Streamwise Vortex ◽  
Flow Visualisation ◽  
Content Type ◽  
Oil Flow ◽  
Order Of Magnitude ◽  
Oil Flow Visualization ◽  
Unsteady Operation ◽  
Naca 0012

Purpose The purpose of this paper is to compare the effects of two different configurations of plasma streamwise vortex generators (PSVG), including comb-type and mesh-type in controlling flow. This is demonstrated on the NACA 0012 airfoil. Design/methodology/approach The investigations have been done experimentally at the various electric and aerodynamic conditions. The surface oil flow visualization method has been used to the better understanding of the flow physics and the interaction of the oncoming flow passing over the airfoil and the vortex generated by comb-type PSVG. Findings This paper demonstrates the potential capabilities of the mesh-type and comb-type PSVGs in controlling flow in unsteady operation. It was found that the vortex generated by the mesh-type PSVG in unsteady operation was an order of magnitude stronger than comb-type PSVG. The flow visualisation technic proved that only a part of the plasma actuator is effective in the condition that the actuator is installed only on a portion of the upper surface of the airfoil. Originality/value This paper experimentally confirms the capabilities of the mesh-type PSVG unsteady operation in compare with comb-type PSVG in controlling flow, whereby recommends using mesh-type PSVG in the leading edge in front of comb-type PSVG on the entire wingspan to prevent the stall.

scholarly journals The Effect of Single Dielectric Barrier Discharge Actuators in Reducing Drag on an Ahmed Body

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 244
Author(s):  
Saber Karimi ◽  
Arash Zargar ◽  
Mahmoud Mani ◽  
Arman Hemmati
Keyword(s):  
Drag Reduction ◽  
Dielectric Barrier Discharge ◽  
Barrier Discharge ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Dielectric Barrier ◽  
Car Model ◽  
Slant Surface ◽  
Ahmed Body

The feasibility of a single dielectric barrier discharge (SDBD) actuator in controlling flow over an Ahmed body, representing a simplified car model, has been numerically and experimentally investigated at Reynolds numbers of 7.68×105 and 2.25×105. The Ahmed body had slant angles of 25∘ and 35∘. The results showed that SDBD actuators could significantly enhance the aerodynamic performance of the Ahmed body. Several arrangements of the actuators on the slant surface and the rear face of the model were examined to identify the most effective arrangement for drag reduction. This arrangement resulted in an approximately 6.1% drag reduction. This improvement in aerodynamic performance is attributed to the alteration of three-dimensional wake structures due to the presence of SDBD, which coincides with surface pressure variations on the slant and rear faces of the Ahmed body.

Study on Natural Gas Drag Reduction Agent and Mechanism of Gas Pipelines Drag Reduction

2008 ◽  
Author(s):  
Guoping Li ◽  
Zhiheng Zhang ◽  
Bing Liu ◽  
Chunman Li ◽  
Weichun Chang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Drag Reduction ◽  
Reduction Method ◽  
Radial Pulsation ◽  
Gas Pipelines ◽  
Oil Pipelines ◽  
Oil Flow ◽  
Pipeline Wall ◽  
Gas Drag ◽  
Long Chain

On the basis of the study on the principle of oil flow and that on mechanism of drag reduction and transportation promotion of oil pipelines, the article makes a further research on the Mechanism of Drag Reduction in the gas pipelines. It points out that the basic cause for gas pipelines drag reduction is to control effectively the radial pulsation of gas adjacent to pipeline wall. It is considered that the most effective drag reduction method is to reduce the pipeline wall’s roughness degree and pipeline wall’s undercoat and to make gas drag reduction agent adjacent to pipeline wall. The research shows that gas drag reduction agent should be a polymer and compound with polarity and nonpolarity long chain.

Drag reduction effect of crude palm oil flow by using Tween 80 in pentagon spiral pipe

2020 ◽  
Author(s):  
Yanuar ◽  
Gunawan ◽  
Angga Arianda ◽  
M. Raihan Setiawan ◽  
Whisnu Febriansyah
Keyword(s):  
Drag Reduction ◽  
Palm Oil ◽  
Tween 80 ◽  
Crude Palm Oil ◽  
Oil Flow ◽  
Reduction Effect

Experimental Investigation of Oil Flowrate in a Hermetic Reciprocating Compressor

2014 ◽  
Author(s):  
Sibel Tas ◽  
Sertac Cadirci ◽  
Hasan Gunes ◽  
Kemal Sarioglu ◽  
Husnu Kerpicci
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
High Speed ◽  
Operating Conditions ◽  
Lubricating Oil ◽  
Reciprocating Compressor ◽  
Oil Flow ◽  
Oil Flow Visualization

The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in a hermetic reciprocating compressor. Essential parameters affecting the performance of the lubrication are the rotational speed of the crankshaft, the viscosity of the oil, the operating temperature and the submersion depth of the crankshaft. An experimental setup was built as to measure the oil mass flow rate with respect to the oil temperature variation during different operating conditions. The influence of the governing parameters such as the rotational speed, temperature (viscosity) and the submersion depth on the mass flow rate from crankshaft outlet are studied in detail. In addition, the oil flow visualization from the upper hole of the crankshaft is performed using a high-speed camera in order to observe the effectiveness of the lubrication of the various parts of the compressor. This study reveals that with increasing rotational speed, the submersion depth of the crankshaft and with decreasing viscosity of the lubricant, the mass flow rate from the crankshaft increases.

Complex Secondary Flow and Associated Loss Generation in Ultra-Highly Loaded Turbine Cascade

2010 ◽  
Author(s):  
Hoshio Tsujita ◽  
Atsumasa Yamamoto
Keyword(s):  
Secondary Flow ◽  
Static Pressure ◽  
Incidence Angle ◽  
Blade Surface ◽  
Turbine Cascade ◽  
Blade Loading ◽  
Oil Flow ◽  
Oil Flow Visualization ◽  
Secondary Flow Structure ◽  
Highly Loaded

An increase of turbine blade loading decreases the numbers of blades and stages, and results in the improvement of the performance characteristics of gas turbines. However, in such highly loaded turbine cascade with high turning angle, the secondary flow becomes much strong due to the steep pressure gradient across the blade-to-blade passage and deteriorates the performance of turbine enormously. In this study, the computations were performed for the flow in the ultra-highly loaded turbine cascade in order to clarify the effects of the inlet boundary layer thickness and the incidence angle which strongly influence the secondary flow structure in a turbine cascade. Moreover, the experimental oil flow visualization was conducted on the blade surface and the endwall, and the measurements of blade surface static pressure were performed at the midspan. The computed results agreed well with the oil flow visualization and the measured blade surface static pressure. The effects of the incidence angle and the inlet boundary layer thickness on the secondary flow structure, the total pressure loss, the secondary flow kinetic energy and the blade loading distributions were examined in detail. The positive incidence angle induced the characteristic vortex released from the endwall. Moreover, it was revealed that the interactions among the horseshoe vortex, the passage vortex and the characteristic vortex strongly increase the secondary loss in the cascade passage.

Studies of Flow Topology around Hemisphere at Transonic Speeds Using Time-Resolved Oil Flow Visualization

2016 ◽  
Author(s):  
Stanislav Gordeyev ◽  
Alexander Vorobiev ◽  
Eric J. Jumper ◽  
Sivaram P. Gogineni ◽  
Donald J. Wittich
Keyword(s):  
Flow Visualization ◽  
Flow Topology ◽  
Time Resolved ◽  
Oil Flow ◽  
Oil Flow Visualization
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