Some Features of Pulse-Periodic Energy Supply in Supersonic Flow

2010 ◽  
Vol 5 (2) ◽  
pp. 43-54
Author(s):  
Vladimir N. Zudov ◽  
Pavel K. Tretyakov ◽  
Andrey V. Tupikin
Keyword(s):  
Physical Model ◽  
Energy Supply ◽  
Aerodynamic Drag ◽  
Reverse Flow ◽  
High Sensitivity ◽  
Quantitative Agreement ◽  
Frequency Effect ◽  
Experimental Investigations ◽  
Supply Source ◽  
Thermal Wake

In the present work, the results of numerical and experimental investigations of supersonic flows with a localized energy supply are considered. The energy supply region (the heat source) was formed by the plasma created by a focused pulsed-periodic laser emission either by combustion in the separation zone upstream of the blunted body. The main attention is paid to the unsteady effects the role of which is determining at the integral flow structure formation. A physical model of energy source is formulated. The numerical and experimental data on the structure of the flow around the source and the characteristics of a thermal wake arising behind the source are compared. The energy pulses frequency and capacity are shown to determine the wake properties: the formation and development of subsonic regions, vortex structures, and reverse flow regions. It follows from an analysis of the aerodynamic drag variation at a flow with a thermal wake of the energy supply source around blunt bodies that the energy and pulse as well as its duration are the main parameters determining the efficiency of the frequency effect. A high sensitivity of the results to the physical model accepted in numerical investigation is shown. The pressure variation dynamics on a conical surface is presented versus the frequency of pulses. Comparison with experiment has shown a good quantitative agreement.

AMPLIFICATION AND PHASE CONJUGATION OF WEAK SIGNALS

1993 ◽  
Vol 02 (01) ◽  
pp. 85-115 ◽  
Author(s):  
O.V. KULAGIN ◽  
G.A. PASMANIK ◽  
A.A. SHILOV
Keyword(s):  
Theoretical Approach ◽  
Phase Conjugation ◽  
High Sensitivity ◽  
Optical Systems ◽  
Experimental Investigations ◽  
Weak Signals ◽  
Optical Signals ◽  
Basic Concepts

The results of the study on phase conjugation of weak optical signals with the energy of units of photons are considered. Basic concepts of a semi-classical theoretical approach to describe amplification and phase conjugation (PC) of such signals are presented. A review is given on the experimental investigations that allowed for reaching a limit (about 1 photon for a mode) sensitivity of optical systems with PC-mirrors for a large (~ 105) number of resolution elements. High-sensitivity PC-mirror optical systems are demonstrated for a variety of applications.

scholarly journals Conducting experimental investigations of wind influence on high-rise constructions

2018 ◽  
Vol 33 ◽  
pp. 02067 ◽  
Author(s):  
Olga I. Poddaeva ◽  
Anastasia N. Fedosova ◽  
Pavel S. Churin ◽  
Julia S. Gribach
Keyword(s):  
Aerodynamic Drag ◽  
Experimental Investigations ◽  
Building Structures ◽  
High Rise ◽  
Aerodynamic Pressure ◽  
Stage Of Development ◽  
Wind Influence ◽  
Under Construction ◽  
Building Designs ◽  
The Impact

The design of buildings with a height of more than 100 meters is accompanied by strict control in determining the external loads and the subsequent calculation of building structures, which is due to the uniqueness of these facilities. An important factor, the impact of which must be carefully studied at the stage of development of project documentation, is the wind. This work is devoted to the problem of studying the wind impact on buildings above 100 meters. In the article the technique of carrying out of experimental researches of wind influence on high-rise buildings and constructions, developed in the Educational-research-and-production laboratory on aerodynamic and aeroacoustic tests of building designs of NRU MGSU is presented. The publication contains a description of the main stages of the implementation of wind tunnel tests. The article presents the approbation of the methodology, based on the presented algorithm, on the example of a high-rise building under construction. This paper reflects the key requirements that are established at different stages of performing wind impact studies, as well as the results obtained, including the average values of the aerodynamic pressure coefficients, total forces and aerodynamic drag coefficients. Based on the results of the work, conclusions are presented.

scholarly journals Economic Analysis of Solar Refrigeration and Desalination System

2019 ◽  
Vol 118 ◽  
pp. 02021
Author(s):  
Xiaoman Zhang ◽  
Qin Shen ◽  
Shijun Zhu
Keyword(s):  
Mathematical Model ◽  
Economic Analysis ◽  
Physical Model ◽  
Energy Supply ◽  
Recovery Period ◽  
Heat Consumption ◽  
Refrigeration System ◽  
Generation System ◽  
Refrigeration Capacity ◽  
Solar Refrigeration

The physical model and mathematical model of solar refrigeration and desalination co-generation system were established. The performance and economy of the system were analyzed by changing the three variables of refrigeration capacity, seawater desalination effects number and three different cities. The results show that increasing refrigeration capacity is conducive to improving freshwater production and increasing freshwater efficiency, but more auxiliary heat consumption is needed, the comprehensive effect is to shorten the recovery period. Increasing desalination efficiency is conducive to increasing freshwater production and freshwater efficiency, and the auxiliary heat consumption remains unchanged. The comprehensive effect is to shorten the recovery period. Solar energy is the main energy needed in the co-generation system of the three cities, and Shenzhen has the largest proportion of energy supply, which reaches 67.8%. Compared with the solar refrigeration system, the recovery period of the co-generation system can bu shortened by 18.1%.

The influence of the thermal wake due to pulsating optical discharge on the aerodynamic-drag force

2018 ◽  
Vol 25 (2) ◽  
pp. 257-264 ◽  
Author(s):  
T. A. Kiseleva ◽  
A. A. Golyshev ◽  
V. I. Yakovlev ◽  
A. M. Orishich
Keyword(s):  
Drag Force ◽  
Aerodynamic Drag ◽  
Optical Discharge ◽  
Thermal Wake

scholarly journals DEVELOPMENT OF A HIGH-SENSITIVITY TORSION BALANCE TO INVESTIGATE THE THERMAL CASIMIR FORCE

2012 ◽  
Vol 14 ◽  
pp. 337-346 ◽  
Author(s):  
TODD GRAVESON ◽  
CHARLES RACKSON ◽  
WOO-JOONG KIM
Keyword(s):  
Casimir Force ◽  
High Sensitivity ◽  
Torsion Balance ◽  
Surface Patch ◽  
Experimental Investigations ◽  
Electric Force ◽  
Force Measurements ◽  
Semiconducting Materials ◽  
Proper Understanding ◽  
Actual Contribution

We report development of a high-sensitivity torsion balance to measure the thermal Casimir force. Special emphasis is placed on experimental investigations of a possible surface electric force originating from surface patch potentials that have been recently noticed by several experimental groups. By gaining a proper understanding of the actual contribution of the surface electric force in real materials, we aim to undertake precision force measurements to resolve the Casimir force at finite temperature in real metals, as well as in other semiconducting materials, such as graphene.

Experimental investigation of the aerodynamic drag of roof-mounted insulators for trains

2019 ◽  
Vol 234 (8) ◽  
pp. 834-846
Author(s):  
Jonathan Tschepe ◽  
Jörg-Torsten Maaß ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Energy Demand ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Resistance ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Flexible Material ◽  
High Speed Trains ◽  
The Impact

This paper presents the results of experimental investigations on the aerodynamic drag of roof-mounted insulators for use on low- and high-speed trains. Wind tunnel investigations at different Reynolds numbers in the subcritical, critical, and supercritical flow regime were performed, in addition to investigations using wall-mounted cylinders. Furthermore, the impact of insulator sheds made of flexible material was analyzed. For a better understanding of the aerodynamic behavior of the insulators when mounted on trains, different boundary conditions representing realistic configurations as found on the roof of trains were simulated. From the measured drag, the energy demand to overcome the aerodynamic resistance of different types of insulators was calculated. Depending on the above mentioned boundary conditions, a noticeable contribution of the insulators to the entire train's aerodynamic drag could be observed. With flexible insulator sheds, a further increased air resistance was observed with the onset of fluttering. Similar to the cylinder, the aerodynamic behavior of the insulators depends on the respective Reynolds number.

Investigation of the Cooling and Underbody Flow Field on a Detailed Scale Model Passenger Car: Part 2—Effect of Ground Simulation

2009 ◽  
Author(s):  
Christoffer Landstro¨m ◽  
Lasse Christoffersen ◽  
Lennart Lo¨fdahl
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Aerodynamic Drag ◽  
Scale Model ◽  
Experimental Investigations ◽  
Passenger Cars ◽  
Local Flow ◽  
Passenger Car ◽  
Reynolds Number Effects ◽  
Cooling Air

Future demands on passenger cars consist to a large extend of making them more energy efficient. Reducing the driving resistance by reducing the aerodynamic drag will be one important part in reducing fuel consumption. In most cases during passenger car development, early experimental investigations are performed in scale model wind tunnels. Considering that such models inevitably suffer from Reynolds number effects it is important to understand how this affects the test results. Investigations of the aerodynamics of a detailed scale model Volvo S60 have been performed in the aerodynamic wind tunnel at Chalmers University of Technology. The investigation aimed at increasing the understanding of how the flow field in scale model testing is affected by ground simulation and different cooling air flow configurations at different Reynolds numbers. A full width moving ground system was used in the experiments. Pressure taps were distributed between the cooling air inlets, the underbody and the vehicle base. An internal six component balance was used to measure global forces and moments. By combining the results from the measurements it was possible to increase the understanding of some of the local flow features. Results showed significant Reynolds number effects both with stationary ground as well as moving ground and rotating wheels. Global aerodynamic drag as well as front and rear axle lift was found to be affected.

Flow over a glider canopy

2014 ◽  
Vol 118 (1204) ◽  
pp. 669-682
Author(s):  
A. S. Jonker ◽  
J. J. Bosman ◽  
E. H. Mathews ◽  
L. Liebenberg
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Computational Fluid Dynamics ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Aerodynamic Drag ◽  
Canopy Gap ◽  
Experimental Investigations ◽  
Front Part ◽  
Gap Width

Abstract In order to minimise drag, the front part of most modern glider fuselages is shaped so that laminar flow is preserved to a position close to the wing-to-fuselage junction. Experimental investigations on a full-scale JS1 competition glider however revealed that the laminar boundary layer in fact trips to turbulent flow at the fuselage-to-canopy junction position, increasing drag. This is possibly due to ventilation air leaking from the cockpit to the fuselage surface through the canopy seal, or that the gap is merely too large and therefore trips the boundary layer to turbulent flow. The effect of air leaking from the fuselage-to-canopy gap as well as the size of the gap was thus investigated with the use of computational fluid dynamics. It was found that if air was leaking through this gap the boundary layer would be tripped from laminar to turbulent flow. It was also found that the width of the canopy-to-fuselage gap plays a significant role in the preservation of laminar flow. If the gap is less than 1mm wide, the attached boundary layer is able to negotiate the gap without being tripped to turbulent flow, while if the gap is 3mm and wider, it will be tripped from laminar to turbulent flow. The work shows that aerodynamic drag on a glider can be significantly minimised by completely sealing the fuselage-to-canopy gap and by ensuring a seal gap-width of less than 1mm.

scholarly journals An Investigation of r.f. Travelling Wave Current Drive Using the Model

1988 ◽  
Vol 41 (4) ◽  
pp. 587 ◽  
Author(s):  
WK Bertram
Keyword(s):  
Magnetic Field ◽  
Quantitative Agreement ◽  
Travelling Wave ◽  
Current Drive ◽  
Experimental Investigations ◽  
Initial Increase ◽  
Toroidal Plasma ◽  
Subsequent Decrease ◽  
Observed Behaviour ◽  
Drive Model

Previous experimental investigations into the use of travelling r.f. waves to drive steady toroidal currents in a toroidal plasma have shown that It, the amount of current driven, is strongly dependent on the ratio of the static toroidal magnetic field Bz, to the strength of the r.f. magnetic field BO). This dependence is characterised by an initial increase and subsequent decrease of It when Btl BfIJ increases. It is shown that this observed behaviour is entirely consistent with the behaviour predicted by the <i X B) current drive model. Results from .numerical computations using the <i X B) model show good quantitative agreement with the published experimental results.

scholarly journals Modeling of the Stepping Process of Negative Lightning Stepped Leaders

2017 ◽  
Author(s):  
Vernon Cooray ◽  
Liliana Arevalo
Keyword(s):  
Physical Model ◽  
Reasonable Agreement ◽  
Propagation Speed ◽  
Step Length ◽  
Experimental Investigations ◽  
Small Length ◽  
Return Stroke ◽  
Subsequent Formation ◽  
Peak Current ◽  
Model Based

A physical model based on the mechanism observed in experimental investigations is introduced to describe the formation of negative leader steps. Starting with a small length of a space leader located at the periphery of the negative streamer system of the stepped leader the model simulates the growth and the subsequent formation of the leader step. Based on the model, the average step length, the average step forming time and the average stepped leader propagation speed is estimated as a function of prospective return stroke peak current. The results show that the average step length and the average leader speed increases with increasing prospective return stroke current. The results also show that the speed of the stepped leader increases as it approaches the ground. For a 30 kA prospective return stroke current the average leader speed obtained is about 5 x 105 m/s and the average step length was about 10 m. The results obtained are in reasonable agreement with the experimental observations.&nbsp;

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