Durgesh Vikram¹, Sanjay Mittal², Partha Chakroborty¹

CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 237-260, 2011, DOI:10.3970/cmes.2011.079.237

Abstract A stabilized finite element formulation is presented to solve the governing equations for traffic flow. The flow is assumed to be one-dimensional. Both, PW-type (Payne-Whitham) 2-equation models and the LWR-type (Lighthill-Whitham-Richards) 1-equation models are considered. The SUPG (Streamline-Upwind/Petrov-Galerkin) and shock capturing stabilizations are utilized. These stabilizations are sufficient for the 1-equation models. However, an additional stabilization is necessary for the 2-equation models. For the first time, such a stabilization is proposed. It arises from the coupling between the two equations and is termed as IEPG (Inter-Equation/Petrov-Galerkin) stabilization. Two behavioral models are studied: Greenshields' (GS) and Greenberg's (GB) models. Numerical tests… More >

W. A. El-Askary¹

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 203-232, 2011, DOI:10.3970/cmes.2011.074.203

Abstract Large eddy simulation (LES) is a viable and powerful tool to analyze unsteady three- dimensional turbulent flows. In this paper, the method of LES is used to compute a plane turbulent supersonic boundary layer subjected to different pressure gradients. The pressure gradients are generated by allowing the flow to pass in the vicinity of an expansion-compression ramp (inclined backward-facing step with leeward-face angle of 25 degrees) for an upstream Mach number of 2.9. The inflow boundary condition is the main problem for all turbulent wall-bounded flows. An approach to solve this problem is to extract instantaneous velocities, temperature and density… More >

Ivan Christov¹, C.I. Christov², P.M. Jordan³

CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 47-54, 2007, DOI:10.3970/cmes.2007.017.047

Abstract Two widely-used weakly-nonlinear models of acoustic wave propagation --- the inviscid Kuznetsov equation (IKE) and the Lighthill--Westervelt equation (LWE) --- are investigated numerically using a Godunov-type finite-difference scheme. A reformulation of the models as conservation laws is proposed, making it possible to use the numerical tools developed for the Euler equations to study the IKE and LWE, even after the time of shock-formation. It is shown that while the IKE is, without qualification, in very good agreement with the Euler equations, even near the time of shock formation, the same cannot generally be said for the LWE. More >

Davood Kalantari¹

FDMP-Fluid Dynamics & Materials Processing, Vol.5, No.1, pp. 81-92, 2009, DOI:10.3970/fdmp.2009.005.081

Abstract In this paper a theoretical approach is elaborated for modelling the impact and ensuing spreading behaviour of a liquid droplet after its collision with a flat and rigid surface. The major outcomes of such a study can be summarized as follows: 1) The propagating-shock-wave velocity associated with the droplet is not a constant value but depends on the impact velocity and the physical and geometrical properties of the droplet. 2) The initial radial ejection velocity of the lamella is proportional to the shock-wave velocity (ua) and the impact velocity (0) according to the expression (a-u0)1/2. 3) The deceleration behaviour of… More >

B. Srivathsa¹, N. Ramakrishnan²

CMC-Computers, Materials & Continua, Vol.7, No.1, pp. 9-24, 2008, DOI:10.3970/cmc.2008.007.009

Abstract An analytical model, describing an explosive compaction process performed axially on a powder assembly of cylindrical geometry, is discussed. The powder is encapsulated in a cylindrical metal container surrounded by an explosive pad, which is detonated parallel to the major axis of the compact. The pressure generated in the powder is a function of the nature and the thickness of the explosive material as well as the powder characteristics. The model is based on the principle of shock propagation in powder aggregate and, the detonation as well as the refraction wave characteristics of the explosives. For the purpose of validation… More >