Exploratory Studies on the Control of High-Speed Flows With Magnetogasdynamics

2002 ◽  
Author(s):  
Datta V. Gaitonde
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Control Mechanisms ◽  
Ground Testing ◽  
Simulation Efficiency ◽  
The Status ◽  
Physical Phenomena ◽  
Insight Into

Magnetogasdynamics (MGD) has the potential to lift many of the constraints presently inhibiting sustained hypersonic flight and affordable access to space. Given the difficulty of ground-testing under the expected harsh conditions, numerical methods can provide insight into the physical phenomena, and thus complement experimental investigations in the development of future concepts. This paper describes the status of an effort to develop a high-fidelity, fully three-dimensional method to explore MGD flow control in complex configurations. The theoretical model includes several non-ideal effects and takes recourse to a blend of first principles and phenomenological approaches to enhance simulation efficiency. Boundary conditions are summarized and sample verification exercises are presented. Exploratory calculations on a reentry vehicle and flow-through scramjet flowpath with MGD-bypass demonstrate the versatility of the approach and yield insight into dominant flow control mechanisms.

Seakeeping Analysis of a High-Speed Monohull With a Motion-Control Bow Hydrofoil

2004 ◽  
Vol 48 (02) ◽  
pp. 77-117 ◽  
Author(s):  
Paul D. Sclavounos ◽  
Henning Borgen
Keyword(s):  
Motion Control ◽  
High Speed ◽  
Three Dimensional ◽  
Control Device ◽  
Control Mechanisms ◽  
Hull Form ◽  
Active Motion ◽  
Seakeeping Performance ◽  
Seakeeping Analysis ◽  
Longitudinal Position

The seakeeping performance is studied of a foil-assisted high-speed monohull vessel using a state-of-the-art three-dimensional Rankine panel method. The vessel is equipped with a bow hydrofoil acting as a passive heave and pitch motion-control device in waves. The formulation of the seakeeping of ships equipped with lifting appendages is developed, and the mechanisms responsible for the reduction of the heave and pitch motions of high- speed vessels equipped with hydrofoils are studied. The sensitivity of the heave and pitch motions on the longitudinal position of the hydrofoil is studied. It is found that the most efficient location for the hydrofoil is at the ship bow leading to a 50% reduction of the root mean square values of the heave and pitch motions in a Joint North Sea Wave Project (JONSWAP) spectrum. Several extensions of the analysis of the present paper are discussed. They include the reduction of the roll motion of high-speed vessels, the design of optimal active motion-control mechanisms, and the coupling of the hull form and lifting appendage design for high-speed monohull vessels.

scholarly journals Experimental Investigations of Three-Dimensional Effects on Cavitating Hydrofoils

1961 ◽  
Vol 5 (03) ◽  
pp. 22-43
Author(s):  
R. W. Kermeen
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Pitching Moment ◽  
Two Dimensional ◽  
Dimensional Effects ◽  
Aspect Ratios

An investigation in the high-speed water tunnel of the hydsrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular plan-form, 6-deg wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

scholarly journals Prioritized Retransmission: A TCP Flow Control Mechanism

2019 ◽  
Vol 8 (4) ◽  
pp. 1680-1686 ◽  
Keyword(s):  
Flow Control ◽  
Traffic Control ◽  
High Speed ◽  
Control Mechanism ◽  
Communication Link ◽  
Control Mechanisms ◽  
Internet Communication ◽  
Buffer Overflows ◽  
Transmission Control Protocols ◽  
Retransmission Mechanism

Now-a-days, efforts have been made in the research of transmission control protocols to improve the performance of the flow control mechanism. Internet communication and services daily increase the variety and quantity of their capacity and needs. Therefore the flow control mechanism will have to consider valuable for traffic control, especially on high-speed networks. Initially there are some challenges, for instance, loss of packet, processing capacity, performance, buffer overflows and deadlocks with which daily traffic is confronted. This paper analyzes and reviewed the strengths and weaknesses of the different flow control mechanisms used in TCP. To overcome the weaknesses of these flow controls, we suggest a priority retransmission mechanism. Here we have priority on the Negative Acknowledgment (NACK), we resend the package on the basis of the minimum sequence number of the NACK. In buffer of priority retransmission Automatic Repeat request (ARQ) mechanism, the packet is released to the communication link in a First in First out (FIFO) manner. That is why the priority retransmission ARQ gives the optimum performance

Dynamics of Planar, Elastic, High-Speed Mechanisms Considering Three-Dimensional Offset Geometry: Analytical and Experimental Investigations

1983 ◽  
Vol 105 (3) ◽  
pp. 498-510 ◽  
Author(s):  
F. R. Stamps ◽  
C. Bagci
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Shock Loading ◽  
Dynamic Stress ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Planar Mechanisms ◽  
Elastic Systems ◽  
Stress Levels

Mechanisms in industrial applications in general operate as three-dimensional elastic systems, including planar mechanisms due to offsets between the planes of motion of links. This article investigates dynamic behaviors of planar mechanisms with offset geometry analytically and experimentally for dynamic stress and critical speed levels. Three-dimensional line element with irregular freedoms is used and generalized digital computer programs are prepared to perform kineto-elasto-static, dynamic stress, frequency, and critical speed analyses of three-dimensional mechanisms including the planar mechanisms with three-dimensional offsets. An experimental planar four-bar mechanism was tested for critical speed and elastodynamic stress levels with three levels of offsets. It has been determined that a mechanism experiences integer divisions of the integrated average of the three-dimensional fundamental natural frequency, ωinavg, within a cycle of the mechanism as critical speeds as well as its multiples. Recommended operating speeds of a mechanism are those in between two integer divisions of ωinavg at lower levels. Elastodynamic stress levels at these recommended speed levels are predicted analytically by kineto-elasto-static analysis and very conservatively even in the shock loading zones of the mechanism. The validity of the highly economical CGKES (Critical Geometry Kineto-Elasto-Statics) method for mechanisms having three-dimensional geometry is also verified by the experimental results.

scholarly journals Modeling the airflow field of vortex spinning

2021 ◽  
pp. 004051752110569
Author(s):  
Shanshan Shang ◽  
Zikai Yu ◽  
Guangwu Sun ◽  
Chongwen Yu ◽  
R Hugh Gong ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Wall Function ◽  
Great Insight ◽  
Spinning Process ◽  
Turbulent Airflow ◽  
Region Model ◽  
Airflow Field ◽  
Control Volumes ◽  
Insight Into

Vortex spinning technology adopts a high-speed swirling airflow to rotate the fibers with open-ends to form yarn with real twists. The airflow behavior within the nozzle has a great effect on the yarn-formation process. In this study, a three-dimensional calculation nozzle model and corresponding three-dimensional airflow region model were established to enable the numerical calculation; airflow behavior—pressure, velocity, and the turbulent airflow field, and the streamline of airflow—was investigated in the presence of fiber bundles within the vortex spinning nozzle. Hybrid hexahedral/tetrahedral control volumes were utilized to mesh the grids in the calculation region. To consider airflow diffusion and convection in the nozzle, the Realizable k- ε turbulence model with wall function was adopted to conduct the calculation. Dynamic and static pressure values were obtained by numerical analysis to predict the action of the inner surface of nozzle and the wall resistance on the high-speed swirling airflow. The numerical simulation of dynamic airflow behavior can generate great insight into the details of airflow behavior and its distribution characteristics, and is helpful for understanding the spinning mechanism and promoting optimization of the spinning process.

Tuning g-factor of electrons through spin–orbit coupling in GaAs/AlGaAs conical quantum dots

2016 ◽  
Vol 30 (13) ◽  
pp. 1642003
Author(s):  
Sanjay Prabhakar ◽  
Roderick Melnik
Keyword(s):  
Quantum Dots ◽  
Quantum Logic ◽  
Three Dimensional ◽  
Logic Gates ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Quantum Logic Gates ◽  
Spintronic Devices ◽  
Physical Phenomena ◽  
Insight Into

We investigate band structures of [Formula: see text] three-dimensional conical quantum dots (QDs). In particular, we explore the influence of the Rashba and Dresselhaus spin–orbit couplings in the variation of effective [Formula: see text]-factor of electrons in such QDs. We demonstrate that the interplay between the Rashba and Dresselhaus spin–orbit couplings can provide further insight into underlying physical phenomena and assist in the design of quantum logic gates for the application in spintronic devices.

Visualization of Three-Dimensional Flow Structures Caused by Rotating Instability

2019 ◽  
Author(s):  
Julija Peter ◽  
Paul Uwe Thamsen
Keyword(s):  
High Speed ◽  
Spectral Characteristics ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Flow Structures ◽  
Experimental Investigations ◽  
Flow Topology ◽  
Time Resolved ◽  
Characteristic Flow ◽  
Rotating Instability

Abstract The present study deals with the flow phenomenon Rotating Instability (RI), which is predominantly observed in axial compressors at off-design conditions e.g. near stall. It potentially induces noise and triggers blade vibrations. Despite numerous studies, the characteristics and the source of RI are not completely understood. The objective of this work is to identify and to visualize characteristic flow topology corresponding to RI by means of Stereo High Speed Particle Image Velocimetry (PIV). The experimental investigations were carried out in an annular compressor stator cascade with and without hub clearance at an inflow Mach number of Ma = 0.4 and the Reynolds number of Re = 300 000. The time-resolved 3C flow field is measured in a single blade passage in planes tangential to the hub. Additionally, the time-resolved pressure fluctuations are captured synchronously to the PIV system. By using combined correlation techniques the spectral characteristics, the spatial extension of the RI and the characteristic flow structures were identified and visualized in configurations with and without hub clearance. The investigations point out that the general flow mechanism of RI is similar in compressor cascades with and without hub clearance. Overall, this work gives important insights into the complex phenomenon Rotating Instability, which can be taken into account when developing compressors in the future.

Visualization of R410A Flowing in Copper and Stainless Steel Dimpled Tubes Enhanced by Petal-Shaped Patterns Under Evaporation Conditions

2020 ◽  
Author(s):  
Weiyu Tang ◽  
Zhichuan Sun ◽  
Yang Luo ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
High Speed ◽  
Three Dimensional ◽  
Superior Performance ◽  
Smooth Tube ◽  
Wall Material ◽  
Intermittent Flow ◽  
Experimental Investigations ◽  
The Impact

Abstract Experimental investigations were conducted to study the heat transfer characteristics and flow patterns of R410A during evaporation in three horizontal tubes having the same outside diameter of 12.70 mm and 180 mm in length. The tested tubes contain two tubes with three-dimensional enhanced surface structures (Cu-1EHT and SS-1EHT), and one equivalent smooth tube. This experiment was done at an evaporation temperature of 6 °C and mass flux from 100 to 200 kg/(m2·s) for vapor qualities varying from 0.2 to 0.8. For all the tube tested, flow pattern observations were obtained using a high-speed camera, and the impact of the actual flow regime on heat transfer was discussed. Results indicated that the transition from annular flow to intermittent flow began at a lower vapor quality for two enhanced tubes when compared to the smooth tube. Accordingly, both the Cu-1EHT tube and the SS-1EHT tube exhibited a superior performance than the smooth tube. In addition, the heat transfer coefficient of Cu-1EHT tube is higher than that of the stainless steel one, mainly due to the larger thermal conductivity of wall material.

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