Some applications of extremum principles to magnetohydrodynamic pipe flow

1974 ◽  
Vol 336 (1605) ◽  
pp. 211-222 ◽  
Keyword(s):  
Laminar Flow ◽  
Mass Flow Rate ◽  
Lower Bounds ◽  
Flow Rate ◽  
Wide Class ◽  
Pipe Flow ◽  
Asymptotic Series ◽  
Upper And Lower Bounds ◽  
Thin Wall ◽  
Square Channel

This paper is concerned with the application of extremum principles to the laminar flow of a conducting fluid along a pipe with conducting walls. The extremum principles provide upper and lower bounds to the mass-flow rate Q . While these may supply numerical bounds for Q their main application lies in the construction of asymptotic series at large Hartmann numbers. The most important result is a formula for the leading coefficient in the asymptotic series for Q for a wide class of pipe sections with thick conducting walls. A number of examples are given. A particular example is the square channel with thin conducting walls and it is shown how the ‘thin wall’ approximation can be derived from the extremum principles.

Flow-Rate Estimates for Rectilinear Pipe Flow

1974 ◽  
Vol 41 (4) ◽  
pp. 903-906 ◽  
Author(s):  
L. Wheeler
Keyword(s):  
Error Bound ◽  
Cross Section ◽  
Lower Bounds ◽  
Flow Rate ◽  
Pipe Flow ◽  
Incompressible Fluids ◽  
Upper And Lower Bounds

A means is established for finding upper and lower bounds on the flow rate of viscous incompressible fluids in straight pipes. Bounds are derived for a class of flow regions having as cross section a strip or annulus, and used to deduce an approximation appropriate to such sections when they are thin. Explicit error-bound results are included.

ON THE AVERAGE CASE CIRCUIT DELAY OF DISJUNCTION

1995 ◽  
Vol 05 (02) ◽  
pp. 275-280 ◽  
Author(s):  
BEATE BOLLIG ◽  
MARTIN HÜHNE ◽  
STEFAN PÖLT ◽  
PETR SAVICKÝ
Keyword(s):  
Lower Bounds ◽  
Wide Class ◽  
Time Complexity ◽  
Upper And Lower Bounds ◽  
Average Case ◽  
Asymptotically Optimal ◽  
Circuit Delay ◽  
Suitable Measure

For circuits the expected delay is a suitable measure for the average case time complexity. In this paper, new upper and lower bounds on the expected delay of circuits for disjunction and conjunction are derived. The circuits presented yield asymptotically optimal expected delay for a wide class of distributions on the inputs even when the parameters of the distribution are not known in advance.

scholarly journals Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system

2019 ◽  
Vol 16 (1) ◽  
pp. 33-44 ◽  
Author(s):  
M.K. Islam ◽  
Md. Hasanuzzaman ◽  
N.A. Rahim ◽  
A. Nahar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Parabolic Trough ◽  
Concentrated Solar Energy

Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.

scholarly journals Evaluate the Cooling Performance of Transmit/Receive Module Cooling System in Active Electronically Scanned Array Radar

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1044
Author(s):  
Jun Su Park ◽  
Dong-Jun Shin ◽  
Sung-Hwan Yim ◽  
Sang-Hyun Kim
Keyword(s):  
Laminar Flow ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling System ◽  
Cooling Performance ◽  
Cooling Flow ◽  
Fluid Analysis ◽  
Design Requirements

The active electronically scanned array (AESA) radar consists of many transmit/receive (T/R) modules and is used to track missiles approaching destroyers and fighters. The performance of the AESA radar depends on the T/R module temperature. The T/R module temperature should be maintained under 80 °C to guarantee the performance of the AESA radar. In order to match the design requirements of the cooling system of the AESA radar, it is necessary to evaluate the cooling performance according to various operation/installation environments. In this study, computational fluid analysis was performed by changing the number of T/R modules and the coolant mass flow rate to evaluate the cooling performance of the AESA radar coolant channel. The number of T/R modules was changed from 2 to 16, and the number of coolant inlet Re was changed from 277 to 11,116. As a result, it was confirmed that the temperature increased as the number of T/R modules increased. In addition, when the coolant status was laminar flow, it was confirmed that the cooling performance was significantly lowered. Therefore, the coolant status should be transient or turbulence to decrease the temperature of the T/R module. Additionally, the correlation between the arrangement of the T/R module and the cooling flow must be considered to cool the AESA radar.

Compressible laminar flow in a capillary

1993 ◽  
Vol 246 ◽  
pp. 1-20 ◽  
Author(s):  
H. R. van den Berg ◽  
C. A. ten Seldam ◽  
P. S. van der Gulik
Keyword(s):  
Equation Of State ◽  
Laminar Flow ◽  
Velocity Profile ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate

An equation based on the hydrodynamical equations of change is solved, analytically and numerically, for the calculation of the viscosity from the mass-flow rate of a steady, isothermal, compressible and laminar flow in a capillaiy. It is shown that by far the most dominant correction is that due to the compressibility of the fluid, computable from the equation of state. The combined correction for the acceleration of the fluid and the change of the velocity profile appears to be 1.5 times larger than the correction accepted to date.

Bounds for Initial Value Problems

1973 ◽  
Vol 40 (4) ◽  
pp. 1097-1102 ◽  
Author(s):  
C. A. Bell ◽  
F. C. Appl
Keyword(s):  
Lower Bounds ◽  
Wide Class ◽  
Initial Value Problems ◽  
Numerical Technique ◽  
Analytic Form ◽  
New Method ◽  
Upper And Lower Bounds ◽  
Initial Value ◽  
Linear Combinations

A new method has been developed for finding rigorous upper and lower bounds to the solution of a wide class of initial value problems. The method is applicable to initial value problems of the following type: x(¨t)+f(t,x,x)˙=0,x(0)=X0,x(˙0)=V0, where f is continuous with continuous first derivatives, Lipschitzian, and ∂f/∂x ≥ 0. An original bounding theorem has been formulated and proven and a numerical technique has been developed for finding the bounding functions in analytic form as linear combinations of Tchebyshev polynomials. The method has been applied to several problems of engineering interest.

The standard unit mass flow rate of gas-liquid mixtures

2020 ◽  
pp. 13-16
Author(s):  
V.N. Petrov ◽  
◽  
V.F. Sopin ◽  
L.A. Akhmetzyanova ◽  
Ya.S. Petrova ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Liquid Mixtures ◽  
Unit Mass ◽  
Standard Unit

Prediction of Leakage Mass Flow Rate Through Gas Springs

1987 ◽  
Author(s):  
Roberto Bruno Bossio ◽  
Vincenzo Naso ◽  
Marian Cichy ◽  
Boleslaw Pleszewski
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate
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