Jaimon Dennis Quadros¹, Sher Afghan Khan², Abdul Aabid^3,*, Muneer Baig³

CMES-Computer Modeling in Engineering & Sciences, Vol.137, No.3, pp. 2331-2352, 2023, DOI:10.32604/cmes.2023.028925

Abstract The application of abruptly enlarged flows to adjust the drag of aerodynamic vehicles using machine learning models has not been investigated previously. The process variables (Mach number (M), nozzle pressure ratio (η), area ratio (α), and length to diameter ratio (γ )) were numerically explored to address several aspects of this process, namely base pressure (β) and base pressure with cavity (β_cav). In this work, the optimal base pressure is determined using the PCA-BAS-ENN based algorithm to modify the base pressure presetting accuracy, thereby regulating the base drag required for smooth flow of aerodynamic vehicles. Based on the identical dataset,… More > Graphic Abstract

Javed S. Shaikh^1,*, Krishna Kumar¹, Khizar A. Pathan², Sher A. Khan³

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.6, pp. 1637-1653, 2023, DOI:10.32604/fdmp.2023.025113

Abstract The complex fluid-dynamic instabilities and shock waves occurring along the surface of a two-dimensional wedge at high values of the Mach number are studied here through numerical solution of the governing equations. Moreover, a regression model is implemented to determine the pressure distribution for various Mach numbers and angles of incidence. The Mach number spans the interval from 1.5 to 12. The wedge angles (θ) are from 5° to 25°. The pressure ratio (P₂/P₁) is reported at various locations (x/L) along the 2D wedge. The results of the numerical simulations are compared with the regression model showing good agreement. More >

Ridwan¹, Sher Afghan Khan^1,*, Jaffar Syed Mohamed Ali¹, Mohd. Azan Mohammed Sapardi¹, Abdul Aabid²

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.6, pp. 1655-1678, 2023, DOI:10.32604/fdmp.2023.025230

Abstract In the present study, the base pressure variations induced by the presence of a cavity, known to have a strong influence of the behaviour of supersonic projectiles, are investigated through numerical solution of the balance equations for mass, momentum, and energy. An area ratio of four is considered and numerical simulations are carried out at Mach M = 1.2, 1.4, 1.6, and 1.8 assuming no cavity or cavity locations 0.5D, 1D, 1.5D, and 2D. The inlet pressure of the nozzle is considered as a flow variable. The Taguchi method is also used, and the considered cases are then analyzed using… More >

Aysha Shabana^1,2,*, Asha Crasta¹, Sher Afghan Khan³, Abdul Aabid⁴, Muneer Baig⁴

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.5, pp. 1249-1267, 2023, DOI:10.32604/fdmp.2023.023158

Abstract This work aims to compute stability derivatives in the Newtonian limit in pitch when the Mach number tends to infinity. In such conditions, these stability derivatives depend on the Ogive’s shape and not the Mach number. Generally, the Mach number independence principle becomes effective from M = 10 and above. The Ogive nose is obtained through a circular arc on the cone surface. Accordingly, the following arc slopes are considered λ = 5, 10, 15, −5, −10, and −15. It is found that the stability derivatives decrease due to the growth in λ from 5 to 15 and vice versa.… More >

Abdul Aabid^1,*, Sher Afghan Khan², Muneer Baig¹

FDMP-Fluid Dynamics & Materials Processing, Vol.18, No.6, pp. 1877-1900, 2022, DOI:10.32604/fdmp.2022.021860

Abstract A method based on microjets is implemented to control the flow properties in a convergent-divergent nozzle undergoing a sudden expansion. Three different variants of this active control technique are explored numerically by means of a finite-volume method for compressible fluid flow: with the first one, the control is implemented at the base, with the second at the wall, while the third one may be regarded as a combination of these. When jets are over-expanded, the control is not very effective. However, when a favourable pressure gradient is established in the nozzle, the control becomes effective, leading to an increase in… More >

Peter Lucas¹, Alexander H. van Zuijlen¹, Hester Bijl¹

CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.1, pp. 79-106, 2010, DOI:10.3970/cmes.2010.059.079

Abstract Despite the advances in computer power and numerical algorithms over the last decades, solutions to unsteady flow problems remain computing time intensive.
In previous work [Lucas, P.,Bijl, H., and Zuijlen, A.H. van(2010)], we have shown that a Jacobian-free Newton-Krylov (JFNK) algorithm, preconditioned with an approximate factorization of the Jacobian which approximately matches the target residual operator, enables a speed up of a factor of 10 compared to nonlinear multigrid (NMG) for two-dimensional, large Reynolds number, unsteady flow computations. Furthermore, in [Lucas, P., Zuijlen, A.H. van, and Bijl, H. (2010)] we show that this algorithm also greatly outperforms NMG for parameter… More >

G. Accary¹, S. Meradji², D. Morvan², D. Fougère²

FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.4, pp. 263-270, 2008, DOI:10.3970/fdmp.2008.004.263

Abstract In the literature, only few references have dealt with mixed-convection flows in the low Mach number approximation. For this reason, in the present study we propose to extend the standard 3D benchmark for mixed convection in a rectangular channel heated from below (Medale and Nicolas, 2005) to the case of large temperature variations (for which the Boussinesq approximation is no longer valid). The Navier-Stokes equations, obtained under the assumption of a low Mach number flow, are solved using a finite volume method. The results, corresponding to the steady-state case of the benchmark, lead to the idea of launching a call… More >