Bayram Celik

Shock interaction mechanisms on a double wedge at Mach 7

Present computational study investigates formation and interaction mechanisms of shocks and boundary layer for low enthalpy Mach 7 flows of nitrogen over double wedges, which have fixed fore and various aft angles of 30° and 45°–60°, respectively. We use a density based finite-volume Navier-Stokes solver to simulate low enthalpy Mach 7 flows of nitrogen over double wedges. The solver is first and second order accurate in time and space, respectively. The meshes used in simulations of two-dimensional laminar flows consist of multiple blocks of structured mesh. Depending on the intensity, impingement angle, and impingement location of transmitted shock wave, the resulting adverse pressure gradient related disturbances on the wedge surface can trigger complex flow physics both in subsonic and supersonic regions. We observe a strong interaction between the deformation of the boundary layer and the bow shock as well as the transmitted shock for high aft angles. Comparison of the obtained results in terms of general flow physics shows that there exists an aft angle threshold value for such interaction which is in the range of 45°–50°.

Computational Investigation of Micro Bacward-Facing Step Duct Flow in Slip Regime

A comprehensive computational analysis is performed to investigate the nature of rarefied gas flow through a backward-facing step duct. A characteristic-based split Navier-Stokes FEM solver is used for the simulations of the flows found in slip regime. The second-order slip-velocity and temperature-jump boundary conditions of Beskok and Karniadakis are applied on the duct walls. Changing flow and heat transfer behavior of the flow due to the varying conditions characterized with non-dimensional parameters are presented and discussed in this article.

Micro‐scale synthetic‐jet actuator flow simulation with characteristic‐based‐split method

Purpose – The purpose of this paper is to present a computational study to investigate the effects of rectangular cavity design of a piezoelectrically driven micro‐synthetic‐jet actuator on generated flow.Design/methodology/approach – Flow simulations were done using a compressible Navier‐Stokes solver, which is based on finite element method implementation of a characteristic‐based‐split (CBS) algorithm. The algorithm uses arbitrary Lagrangian‐Eulerian formulation, which allows to model oscillation of the synthetic jets diaphragm in a realistic manner. Since all simulated flows are in the slip‐flow‐regime, a second order slip‐velocity boundary condition was applied along the cavity and orifice walls. Flow simulations were done for micro‐synthetic‐jet configurations with various diaphragm deflections amplitudes, cavity heights, and widths. All of the simulation results were compared with each other and evaluated in terms of the exit jet velocities, slip‐velocities on the orifice wall and instantaneous mo...