Vortical flow control on a conical fore body cross section using an array of pulsed dc actuators

2007 ◽  
Vol 101 (9) ◽  
pp. 093301 ◽  
Author(s):  
Kunwar Pal Singh ◽  
Subrata Roy
Keyword(s):  
Flow Control ◽  
Cross Section ◽  
Vortical Flow ◽  
Pulsed Dc ◽  
Body Cross Section

Flow Control Over a Circular Cylinder Using Pulsed DBD Actuators

2012 ◽  
Author(s):  
William C. Schneck ◽  
Walter F. O’Brien
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Gas Turbine ◽  
Electric Fields ◽  
Active Flow Control ◽  
Reynolds Numbers ◽  
Pressure Gradients ◽  
High Reynolds Numbers ◽  
Pulsed Dc ◽  
High Reynolds

Immersed bodies such as struts, vanes, and instrumentation probes in gas turbine flow systems will, except at the lowest of flow velocities, shed separated wakes. These wakes can have both upstream and downstream effects on the surrounding flow. In most applications, surrounding components are designed to be in the presence of a quasi-steady or at least non-variant flow field. The presence of unsteady wakes has both aerodynamic and structural consequences. Active flow control of wake generation can therefore be very valuable. One means to implement active flow control is by the use of plasma actuation. Plasma actuation is the use of strong electric fields to generate ionized gas that can be actuated and controlled using the electric fields. The controlling device can be based on AC, DC, or pulsed-DC actuation. The present research was conducted using pulsed-DC from a capacitive discharge power supply. The study demonstrates the applicability of, specifically, pulsed-DC plasma flow control of the flow on a circular cylinder at high Reynolds numbers. The circular cylinder was selected because its flow characteristics are related to gas turbine flowpath phenomena, and are well characterized. Further, the associated pressure gradients are some of the most severe encountered in fluid applications. The development of effective plasma actuators at high Reynolds numbers under the influence of severe pressure gradients is a necessary step toward developing useful actuators for gas turbine applications beyond laboratory use. The reported experiments were run at Reynolds numbers varying from 50,000 to 97,000, and utilizing various pulse frequencies. Further, the observed performance differences with varying electric field strengths are discussed for these Reynolds numbers. The results show that flow behaviors at high Reynolds numbers can be influenced by these types of actuators. The actuators were able to demonstrate a reduction in both wake width and momentum deficit.

scholarly journals Effects of Using Channelling Devices to Increase Efficiency of Hydrokinetic Devices

2015 ◽  
Vol 52 (2) ◽  
pp. 3-12
Author(s):  
A. Kalnacs ◽  
J. Kalnacs ◽  
A. Mutule ◽  
V. Entins
Keyword(s):  
Flow Control ◽  
Flow Velocity ◽  
Cross Section ◽  
Power Output ◽  
High Importance ◽  
Different Types ◽  
The Cross ◽  
Increase Efficiency ◽  
Flow Velocities

Abstract In the rivers of Latvia and of many other countries the flow velocity in the places that are most suitable for installation of hydrokinetic devices is 0.4 to 0.9 m/s. In a stream or a river the hydrokinetic devices can reach full efficiency starting from about twice higher flow velocities. It is advisable to at least double this velocity thus increasing the efficiency and power output of the hydrokinetic devices installed in such places. Since Latvia has abundance of slow rivers and almost none are fast, research in this field is of high importance. Diversified technical methods are known that allow increasing substantially the efficiency of hydrokinetic devices. These methods include the use of diffusers, concentrators, different types of other channelling devices and means of flow control. Desirable effects are achieved through changing the cross-section and/or direction of a flow, its pressure, minimizing the turbulence, etc. This work substantiates the use of such devices for increasing the efficiency of hydrokinetic devices. A method is proposed for evaluation of the effects on power output gained owing to the use of channelling devices. Results show that the efficiency of hydrokinetic devices can be increased by at least 110%.

Experimental and numerical investigations of choked air flow and heat transfer in a ball valve for optimization the cross-sectional area

2019 ◽  
Vol 30 (5) ◽  
pp. 2705-2737 ◽  
Author(s):  
Davood Toghraie ◽  
Hojjatollah Heidari Khouzani
Keyword(s):  
Fluid Flow ◽  
Supersonic Flow ◽  
Flow Control ◽  
Cross Section ◽  
Flow Rate ◽  
Ball Valve ◽  
Flow Coefficient ◽  
Fluid Flow Rate ◽  
Content Type ◽  
Percentage Difference

Purpose The purpose of this study is to understand the functional properties of ball valve in a compressible flow and simulation of experimental data collection of ball valve, was completely simulated. Design/methodology/approach Equations are solved according to finite volume and simplified algorithms. By measuring the flow parameters, including pressure and temperature at different points in the simulation circuit, flow coefficients and localized drop in the valve were determined in different openness cases of test valve and compared with experimental results. Determining a graph for flow coefficient variations in terms of the percentage of openness of the valve is very effective on the flow control as well as on optimizing its cross-section. Findings In the supersonic flow, flow coefficients and local drops of the valve are dependent on several parameters, including fluid flow rate. Flow coefficient graphs at different angles of the test valve show that by increasing the valve opening angle, the flow coefficient increases so that it reaches from 1.72 m3/h at a 30° angle to 46.29 m3/h at a 80° angle. It should be noted that these values in the experimental test were obtained 1.53 m3/h and 49.68 m3/h, respectively, and the percentage difference of these values by simulation was obtained for the angle of 30 degrees 11.7% and for the angle of 80°, about 7% per hour at an angle of 80°. Also, the coefficients of localized loss at different angles of test valve show that by increasing the angle of opening of the valve, the amount of localized loss decreases, so that the average value of 1515.2 in the angle of 30° reaches 1.9 at an angle of 80°. The percentage difference of these values by simulation, for the angle of 30° and 3.5% for the angle of 80°, was about 11.1%. Originality/value Determining a graph for flow coefficient variations versus the percentage of openness of the valve is very effective on the flow control as well as on optimizing its cross-section. In the supersonic flow, flow coefficients and local drop coefficients of the valve are dependent on several parameters, including fluid flow rate.

Topological structure of shock induced vortex breakdown

2009 ◽  
Vol 639 ◽  
pp. 343-372 ◽  
Author(s):  
SHUHAI ZHANG ◽  
HANXIN ZHANG ◽  
CHI-WANG SHU
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Limit Cycles ◽  
Topological Structure ◽  
Stokes Equations ◽  
Vortex Breakdown ◽  
Longitudinal Vortex ◽  
Vortical Flow ◽  
The Cross ◽  
Vortex Axis

Using a combination of critical point theory of ordinary differential equations and numerical simulation for the three-dimensional unsteady Navier–Stokes equations, we study possible flow structures of the vortical flow, especially the unsteady vortex breakdown in the interaction between a normal shock wave and a longitudinal vortex. The topological structure contains two parts. One is the sectional streamline pattern in the cross-section perpendicular to the vortex axis. The other is the sectional streamline pattern in the symmetrical plane. In the cross-section perpendicular to the vortex axis, the sectional streamlines have spiral or centre patterns depending on a function λ (x, t) = 1/ρ(∂ρ/∂t+∂ρu/∂x), where x is the coordinate corresponding to the vortex axis. If λ > 0, the sectional streamlines spiral inwards in the near region of the centre. If λ < 0, the sectional streamlines spiral outwards in the same region. If λ = 0, the sectional streamlines form a nonlinear centre. If λ changes its sign along the vortex axis, one or more limit cycles appear in the sectional streamlines in the cross-section perpendicular to the vortex axis. Numerical simulation for two typical cases of shock induced vortex breakdown (Erlebacher, Hussaini & Shu, J. Fluid Mech., vol. 337, 1997, p. 129) is performed. The onset and time evolution of the vortex breakdown are studied. It is found that there are more limit cycles for the sectional streamlines in the cross-section perpendicular to the vortex axis. In addition, we find that there are quadru-helix structures in the tail of the vortex breakdown.

The Basic Performance Analysis of the Rail Vehicle Body

2013 ◽  
Vol 437 ◽  
pp. 42-46
Author(s):  
Jian Min Ju
Keyword(s):  
Cross Section ◽  
Computer Calculation ◽  
The Body ◽  
Vehicle Body ◽  
Body Structure ◽  
Load Carrying ◽  
Vehicle Structure ◽  
Overall Performance ◽  
Body Cross Section ◽  
Design And Manufacture

The design and manufacture of the vehicle structure determines of the safety and suitability during operation. For most designers, the bearing capacity of the vehicle body is not completely understood. The initial estimate of the vehicle is simply a uniform simply supported overhang beam structure. With the development of computer technology, people can use more complex and closer to the actual body computational model, but it generally requires a lot of work, and designers are often only able to see the final result. It is not clear that the factors affect Load-carrying properties of the body structure. Designers often can not look find a process of improving the design. This method to scan the body structure by a computer calculation and analysis, the geometry, mechanical properties of parameters of the body cross-section has been plotted map. You can quickly and accurately understand the overall performance of the body, analysis the performance difference of different body cross-section. Reasonableness and balance of the body can be measured and awarded. In general, it is very important for the designer of the vehicle.

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