Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Journal of Theoretical and Applied Mechanics

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: frequency-dependent friction

Sortuj według:

Ogranicz wyniki do:

Analytical expressions for effective weighting functions used during simulations of water hammer

Urbanowicz K.

Journal of Theoretical and Applied Mechanics

2017

Vol. 55 nr 3

1029--1040

For some time, work has been underway aimed at significant simplification of the modelling of hydraulic resistance occurring in the water hammer while maintaining an acceptable error. This type of resistance is modelled using a convolution integral, among others, from local acceleration of a liquid and a certain weighting function. The recently completed work shows that during efficient calculations of the convolution integral, the effective weighting function used does not have to be characterised by large convergence with a classical function (according to Zielke during laminar flow and to Vardy-Brown during turbulent flow). However, it must be a sum of at least two or three exponential expressions so that the final results of the simulation could be considered as satisfactory. In this work, it has been decided to present certain analytical formulas using which it will be possible to determine the coefficients of simplified effective weighting functions in a simple direct way.

Improved lumping friction model for liquid pipe flow

Urbanowicz K., Zarzycki Z.

Journal of Theoretical and Applied Mechanics

2015

Vol. 53 nr 2

295--305

Normally, during one-dimensional pipe flow, the friction terms are calculated with the use of a numerical method (for example MOC – method of characteristics) at every computational node along the pipe and at every time step. This procedure tends to increase the computational effort greatly. A considerable increase in computational speed can be archived by calculating the frequency-dependent friction at the end of the pipe only. To avoid possible problems (no damping at closed walls, underestimate damping on high impedance components) the frequency-dependent friction term is calculated from the flow waves. The lumping friction model in this work is based on a modificated Schohl convolution integral solution. In addition, the work examined the impact of using of simplified effective weighting function on the obtained results of numerical simulations. The modified method in conjunction with the use of simplified weighting function allow determination of real-time estimate of the basic parameters representing the fluid flow in complex hydraulic systems, water supply, etc.