A finite difference scheme for unsteady pipe-flows
TL;DR: In this article, a method for finite differences for unsteady pipe flows is presented, where boundary conditions are fixed by making small approximations without much loss in accuracy leading to a simplified computer programs for calculations concerning even complicated flows.
About: This article is published in International Journal of Mechanical Sciences.The article was published on 1979-01-01. It has received 13 citations till now. The article focuses on the topics: Finite difference coefficient & Finite difference.
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01 Oct 1991
12 citations
01 Feb 1983
TL;DR: A thermodynamic simulation model for the 4-stroke cycle of a single cylinder spark ignition engine operating on neat methanol is described in this paper, which computes the gas pressure, gas temperature and the rate of formation of nitric oxide and carbon monoxide at each crank angle using basic energy equation and reaction kinetic mechanism.
Abstract: A thermodynamic simulation model for the 4-stroke cycle of a single cylinder spark ignition engine operating on neat methanol is described in this paper The development of the model for all the processes is illustrated It computes the gas pressure, gas temperature and the rate of formation of nitric oxide and carbon monoxide at each crank angle using basic energy equation and reaction kinetic mechanism A gas exchange model has been formulated by finite difference scheme to evaluate the mass flow rate through valves and the properties in the intake and exhaust systems The validation of the above model has been carried out by comparing the predicted and experimental data at different operating conditions encompassing changes in fuel-air equivalence ratio, speed, load, spark timing and compression ratio The special characteristics of methanol such as rapid burning rate, high power output and reduced nitric oxide emissions have been truthfully predicted by the model
12 citations
01 Oct 1997
11 citations
01 Sep 1986
10 citations
TL;DR: In this article, the authors compare the results of different methods for time-domain simulation and waterhammer hyperbolic partial differential equations and show that first-order Euler integration is more accurate than higher-order methods which introduce errors by violating the domain of dependence.
Abstract: Flow and pressure transients in single-phase liquid-filled closed pipes (i.e. waterhammer) are described by quasi-linear hyperbolic partial differential equations for which the preferred solution technique is the Method of Characteristics. However, this is not appropriate for control and stability analyses where a lumped-parameter single independent variable (i.e. time) model is preferred, using, intentionally or otherwise, the Method of Lines (or partial discretization). By empirical comparison of this with Method of Characteristics time-domain simulation, it has been found that certain implementations introduce avoidable numerical errors or even instabilities. Four aspects have been investigated:
(i)
the dependent variables have often been taken as the original primitive variables but Riemann or Allievi characteristic variables are preferable;
(ii)
for the waterhammer hyperbolic equations at least, a first-order discrete space interpolating polynomial represents the underlying physics better than higher-order approximations;
(iii)
terms in which finite-differences are used to represent quantities which are integrals rather than derivatives, in particular pipe friction, may introduce numerical instability and require particular care;
(iv)
for time-domain simulation, first-order Euler integration is more accurate than higher-order methods which introduce errors by violating the hyperbolic equation domain of dependence.
8 citations
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627 citations
TL;DR: In this article, a method for calculating characteristic diagrams by which the normal position diagram is replaced by a rectangular mesh is discussed, allowing for friction, heat transfer, variable entropy and gradual area changes.
207 citations
TL;DR: In this article, a review of methods for finding solutions to hyperbolic partial differential equations describing unsteady compressible fluid flow is presented, and a number of methods are discussed.
Abstract: The paper reviews briefly a number of methods which are now available to facilitate solutions to the hyperbolic partial differential equations describing unsteady compressible fluid flow. Various s...
52 citations