A fourth-order accurate finite difference method to evaluate the true transient behaviour of natural convection flow in enclosures

Abstract

Purpose Modelling accurately the transient behaviour of natural convection flow in enclosures been a challenging task because of a variety of numerical errors which have limited achieving the higher order temporal accuracy. A fourth-order accurate finite difference method in both space and time is proposed to overcome these numerical errors and accurately model the transient behaviour of natural convection flow in enclosures using vorticity–streamfunction formulation. Design/methodology/approach Fourth-order wide stencil formula with appropriate one-sided difference extrapolation technique near the boundary is used for spatial discretisation, and classical fourth-order Runge–Kutta scheme is applied for transient term discretisation. The proposed method is applied on two transient case studies, i.e. convection–diffusion of a Gaussian Pulse and Taylor Vortex flow having analytical solution. Findings Error magnitude comparison and rate of convergence analysis of the proposed method with these analytical solutions establish fourth-order accuracy and prove the ability of the proposed method to truly capture the transient behaviour of incompressible flow. Also, to test the transient natural convection flow behaviour, the algorithm is tested on differentially heated square cavity at high Rayleigh number in the range of 103-108, followed by studying the transient periodic behaviour in a differentially heated vertical cavity of aspect ratio 8:1. An excellent comparison is obtained with standard benchmark results. Research limitations/implications The developed method is applied on 2D enclosures; however, the present methodology can be extended to 3D enclosures using velocity–vorticity formulations which shall be explored in future. Originality/value The proposed methodology to achieve fourth-order accurate transient simulation of natural convection flows is novel, to the best of the authors’ knowledge. Stable fourth-order vorticity boundary conditions are derived for boundary and external boundary regions. The selected case studies for comparison demonstrate not only the fourth-order accuracy but also the considerable reduction in error magnitude by increasing the temporal accuracy. Also, this study provides novel benchmark results at five different locations within the differentially heated vertical cavity of aspect ratio 8:1 for future comparison studies.

Higher Order Accurate Transient Numerical Model to Evaluate the Natural Convection Heat Transfer in Flat Plate Solar Collector

“…The stability of the method is ensured by the enhanced stability region of the RK4 scheme adopted for the transient term discretization. The complete fourth order method to evaluate the transient behaviour of natural convection flow in enclosures is described in detail in [18].…”

Archive of Mechanical Engineering

“…The same problem of natural convection has been the subject of other numerical investigations [22][23][24][25][26]. Recently, countless analytical and numerical methods have been exploited for the study of natural convection [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. In the works carried out by Belhocine et al [42][43][44][45][46], analytical and numerical methods have proven their efficiency in the treatment and resolution of certain thermal problems such as the method of separation of variables, orthogonal collocation, and the Runge-Kutta method of the fourth-order.…”