S. Ghasemloo and M. Mani
The purpose of this paper is to present a non‐equilibrium viscous shock layer (VSL) solution procedure that considerably improves computational efficiency, especially for long…
Abstract
Purpose
The purpose of this paper is to present a non‐equilibrium viscous shock layer (VSL) solution procedure that considerably improves computational efficiency, especially for long slender bodies.
Design/methodology/approach
The VSL equations are solved in a shock oriented coordinate system. The method of solution is spatial marching, implicit, finite‐difference technique, which includes coupling of the normal momentum and continuity equations. In the nose region, the shock shape is specified from an algebraic expression and corrected through global passes through that region. The shock shape is computed as part of the solution beyond the nose region and requires only a single global pass. For this study, a seven‐species (O2, N2, O, N, NO, NO+, e−) air model is used.
Findings
The present approach eliminates the need for initial shock shape, which was required by previous method of solution. This method generates its own shock shape as a part of solution and the input shock shape obtained from a different solution is not required. Therefore, in comparison with the other VSL methods, the present approach dramatically reduces the CPU time of calculations. Moreover, by using the shock oriented coordinate systems the junction point problem in sphere‐cone configurations is solved.
Practical implications
This method is an excellent tool for parametric study and preliminary design of hypersonic vehicles.
Originality/value
The present method provides a computational capability which reduces the CPU time, and expands the range of application for the prediction of hypersonic heating rates.
Details
Keywords
Yumeng Hu, Haiming Huang and Zimao Zhang
The purpose of this paper is to explore the characteristics of hypersonic flow past a blunt body.
Abstract
Purpose
The purpose of this paper is to explore the characteristics of hypersonic flow past a blunt body.
Design/methodology/approach
The implicit finite volume schemes are derived from axisymmetric Navier–Stokes equations by means of AUSM+ and LU-SGS methods, and programmed in FORTRAN. Based on the verified result that a 2D axisymmetric chemical equilibrium flow has a good agreement with the literature, the characteristics of hypersonic flow past a sphere are simulated by using four different models which involve four factors, namely, viscous, inviscid, equilibrium and calorically perfect gas.
Findings
Compared with the calorically perfect gas under hypervelocity condition, the shock wave of the equilibrium gas is more close to the blunt body, gas density and pressure become bigger, but gas temperature is lower due to the effect of real gas. Viscous effects are not obvious in the calculations of the equilibrium gas or the calorically perfect gas. In a word, the model of equilibrium gas is more suitable for hypersonic flow and the calculation of viscous flow has a smaller error.
Originality/value
The computer codes are developed to simulate the characteristics of hypersonic flows, and this study will be helpful for the design of the thermal protection system in hypersonic vehicles.
Details
Keywords
Hosein Molavi, Javad Rezapour, Sahar Noori, Sadjad Ghasemloo and Kourosh Amir Aslani
The purpose of this paper is to present novel search formulations in gradient‐type methods for prediction of boundary heat flux distribution in two‐dimensional nonlinear heat…
Abstract
Purpose
The purpose of this paper is to present novel search formulations in gradient‐type methods for prediction of boundary heat flux distribution in two‐dimensional nonlinear heat conduction problems.
Design/methodology/approach
The performance of gradient‐type methods is strongly contingent upon the effective determination of the search direction. Based on the definition of this parameter, gradient‐based methods such as steepest descent, various versions of both conjugate gradient and quasi‐Newton can be distinguished. By introducing new search techniques, several examples in the presence of noise in data are studied and discussed to verify the accuracy and efficiency of the present strategies.
Findings
The verification of the proposed methods for recovering time and space varying heat flux. The performance of the proposed methods via comparisons with the classical methods involved in its derivation.
Originality/value
The innovation of the present method is to use a hybridization of a conjugate gradient and a quasi‐Newton method to determine the search directions in gradient‐based approaches.