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Article
Publication date: 20 September 2011

J. Irša and A.N. Galybin

The purpose of this paper is to consider reconstructions of potential 2D fields from discrete measurements. Two potential processes are addressed, steady flow and heat…

Abstract

Purpose

The purpose of this paper is to consider reconstructions of potential 2D fields from discrete measurements. Two potential processes are addressed, steady flow and heat conduction. In the first case, the flow speed and streamlines are determined from the discrete data on flow directions, in the second case, the temperature and flux are recovered from temperature measurements at discrete points.

Design/methodology/approach

The method employs the Trefftz element principle and the collocation. The domain is seen as a combination of elements, where the solution is sought as a linear holomorphic function a priori satisfying the governing equations. Continuity of piecewise holomorphic functions is imposed at collocation points located on the element interfaces. These form the first group of equations. The second group of equations is formed by addressing the measured data, therefore the matrix coefficients may reflect experimental errors. In the case of fluid flow, all equations are homogeneous, therefore one normalising equation is added, which provides existence of a non‐trivial solution. The system is over‐determined; it is solved by the least squares method.

Findings

For the heat flow problem, the determination of heat flux is unique, while for the fluid flow, the determined streamlines are unique and the determination of speed contains one free multiplicative positive constant. Several examples are presented to illustrate the methods and investigate their efficiency and sensitivity to noisy data.

Research limitations/implications

The approach can be applied to other 2D potential problems.

Originality/value

The paper studies two novel formulations of the reconstruction problem for 2D potential fields. It is shown that the suggested numerical method is able to deal directly with discrete experimental data.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 21 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 5 August 2019

Tao Wang, Zhanli Liu, Yue Gao, Xuan Ye and Zhuo Zhuang

The interaction between hydraulic fracture (HF) and natural fracture (NF) in naturally fractured rocks is critical for hydraulic fracturing. This paper aims to focus on…

136

Abstract

Purpose

The interaction between hydraulic fracture (HF) and natural fracture (NF) in naturally fractured rocks is critical for hydraulic fracturing. This paper aims to focus on investigating the development of tensile and shear debonding zone on the NF caused by the stresses produced by HF, and the influence of NF’s debonding behavior on the interaction between HF and NF.

Design/methodology/approach

Theoretically, tensile and shear debonding modes of NF are considered, two dimensionless parameters are proposed to characterize the difficulty of tensile and shear failure of NF, respectively. Numerically, a finite element model combining the extended finite element method and cohesive zone method (CZM) is proposed to study NF’s debonding behavior and its influence on the interaction between HF and NF.

Findings

Both theoretical analysis and numerical simulation show the existence of two debonding modes. The numerical results also show that the HF can cross, offset or propagate along the NFs depending on the parameters’ value, resulting in different fracture network and stimulated reservoir volume. When they are large, the NF’s debonding area is small, HF tends to cross the NF and the fracture network is simple; when they are small, the NF’s debonding area is large, HF will propagate along the NF. In addition, HF is easier to propagate along with NF under tensile debonding mode while it is easier to pass through NF under shear debonding mode.

Originality/value

The theoretical and numerical considerations are taken into account in the influence of the debonding of NFs on the interaction between HFs and NFs and the influence on the formation of the fracture network.

Details

Engineering Computations, vol. 36 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 April 2014

Davood Rostamy and Kobra Karimi

The purpose of this paper is to introduce a novel approach based on the high-order matrix derivative of the Bernstein basis and collocation method and its employment to…

Abstract

Purpose

The purpose of this paper is to introduce a novel approach based on the high-order matrix derivative of the Bernstein basis and collocation method and its employment to solve an interesting and ill-posed model in the heat conduction problems, homogeneous backward heat conduction problem (BHCP).

Design/methodology/approach

By using the properties of the Bernstein polynomials the problems are reduced to an ill-conditioned linear system of equations. To overcome the unstability of the standard methods for solving the system of equations an efficient technique based on the Tikhonov regularization technique with GCV function method is used for solving the ill-condition system.

Findings

The presented numerical results through table and figures demonstrate the validity and applicability and accuracy of the technique.

Originality/value

A novel method based on the high-order matrix derivative of the Bernstein basis and collocation method is developed and well-used to obtain the numerical solutions of an interesting and ill-posed model in heat conduction problems, homogeneous BHCP with high accuracy.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 2 January 2018

Beata Maciejewska, Kinga Strak and Magdalena Piasecka

This paper aims to focus on flow boiling heat transfer in an asymmetrically heated minichannel. Two-dimensional inverse heat transfer problem was solved using the Trefftz…

Abstract

Purpose

This paper aims to focus on flow boiling heat transfer in an asymmetrically heated minichannel. Two-dimensional inverse heat transfer problem was solved using the Trefftz and Beck methods. The primary purpose was to find an enhanced surface that could help intensify heat transfer.

Design/methodology/approach

The experimental set-up and methodology for FC-72 boiling heat transfer in two parallel vertical rectangular minichannels with smooth or enhanced heated surfaces was presented. The heat transfer coefficient was calculated using the Trefftz and Beck methods.

Findings

The results confirm that considerable heat transfer enhancement takes place when selected enhanced heated surface is used in the minichannel flow boiling and that it depends on the type of surface enhancement. The analysis of the experimental data revealed that the values and distributions of the heat transfer coefficient obtained using the Beck and Trefftz methods were similar.

Practical/implications

Many studies have been recently devoted to flow boiling heat transfer in minichannels because of the rapid development of high-performance integrated systems generating large amounts of heat. Highly efficient small-size cooling systems for new-generation compact devices are thus in great demand.

Originality/value

The present results are original and new in the study of cooling liquid boiling in minichannels with enhanced heated surfaces that contribute to heat transfer enhancement. The paper allows the verification of state-of-the-art methods of solving the inverse problem by using empirical data from the experiment. The application of the Trefftz and Beck methods for finding a solution of the inverse heat transfer problem is promising.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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