A. Alper Ozalp

An Interactive Software Package for the Investigation of Hydrodynamic-Slider Bearing-Lubrication

The temperature dependent character of viscosity complicates the numerical analysis of hydrodynamic slider bearings and the geometry of the flow cavity plays a significant role on the design and performance of the lubrication systems. In this paper, we represent a recent software tool, named as “HYDRO‐LUB,” capable of performing constant and variable viscosity runs in various pad styles with moving boundaries. Results of the demonstrating project are not only consistent with the available literature but also show the fast and reliable character of the package; which in return put forward the advantages of applying the program in the lubrication courses of mechanical engineering.

Laminar Boundary Layer Development Around a Circular Cylinder: Fluid Flow and Heat-Mass Transfer Characteristics

This paper presents a comprehensive computational work on the hydrodynamic, thermal, and mass transfer characteristics of a circular cylinder, subjected to confined flow at the cylinder Reynolds number of Red = 40. As the two-dimensional, steady and incompressible momentum and energy equations are solved using ANSYS-CFX (version 11.0), the moisture distributions are computed by a new alternating direction implicit method based software. The significant results, highlighting the influence of blockage (β = 0.200-0.800) on the flow and heat transfer mechanism and clarifying the combined roles of β and moisture diffusivity (D = 1 × 10 -8 -1 × 10 -5 m 2 /s) on the mass transfer behavior, are obtained for practical applications. It is shown that the blockage augments the friction coefficients (C f ) and Nusselt numbers (Nu) on the complete cylinder surface, where the average Nu are evaluated as Nu ave = 3.66, 4.05, 4.97, and 6.51 for β = 0.200, 0.333, 0.571, and 0.800. Moreover, the blockage shifts separation (θ s ) and maximum C f locations (θ Cf-max ) downstream to the positions of θ S = 54.10, 50.20, 41.98, and 37.30 deg and θ Cf-max = 51.5, 53.4, 74.9, and 85.4 deg. The highest blockage of β = 0.800 encourages the downstream backward velocity values, which as a consequence disturbs the boundary layer and weakens the fluid-solid contact. The center and average moisture contents differ significantly at the beginning of drying process, but in the last 5% of the drying period they vary only by 1.6%. Additionally, higher blockage augments mass transfer coefficients (h m ) on the overall cylinder surface; however, the growing rate of back face mass transfer coefficients (h m-bf ) is dominant to that of the front face values (h m-ff ), with the interpreting ratios of h m-bf /h = 0.50 and 0.57 and h m-ff /h m = 1.50 and 1.43 for β = 0.200 and 0.800.

Entropy analysis of laminar-forced convection in a pipe with wall roughness

Momentum and heat transfer rates, as well as entropy generation have been numerically investigated for fully developed, forced convection, laminar flow in a micro-pipe. Compressible and variable fluid property continuity, Navier-Stokes and energy equations are solved for various Reynolds number, constant heat flux and surface roughness cases; entropy generation is discussed in conjunction with the velocity and temperature profiles, boundary layer parameters and heat transfer-frictional characteristics of the pipe flow. Simulations concentrated on the impact of wall roughness based viscous dissipation on the heat transfer behaviour and so occurring heating/cooling activity and the resulting overall and radial entropy generation.

Numerical analysis of choked converging nozzle flows with surface roughness and heat flux conditions

Choked converging nozzle flow and heat transfer characteristics are numerically investigated by means of a recent computational model that integrates the axisymmetric continuity, state, momentum and energy equations. To predict the combined effects of nozzle geometry, friction and heat transfer rates, analyses are conducted with sufficiently wide ranges of covergence half angle, surface roughness and heat flux conditions. Numerical findings show that inlet Mach and Nusselt numbers decrease up to 23.1% and 15.8% with surface heat flux and by 15.13% and 4.8% due to surface roughness. Considering each convergence half angle case individually results in a linear relation between nozzle discharge coefficients and exit Reynolds numbers with similar slopes. Heat flux implementation, by decreasing the shear stress values, lowers the risks due to wear hazards at upstream sections of flow walls; however the final 10% downstream nozzle portion is determined to be quite critical, where shear stress attains the highest magnitudes. Heat transfer rates are seen to increase in the streamwise direction up to 2.7 times; however high convergence half angles, heat flux and surface roughness conditions lower inlet Nusselt numbers by 70%, 15.8% and 4.8% respectively.

Nonadiabatic and frictional constant area duct flow: A visual software based simulation for compressible systems

Numerical investigation of compressible flows in constant area ducts becomes substantially complicated when the surface roughness and heat flux conditions simultaneously act as independent and considerable boundary conditions that create significant influences on the flow and heat transfer characteristics. This article presents GAS‐DYN v2.0, a specialized software package, capable of handling nonadiabatic and frictional systems with the contribution of a database, developed also by the author, which involves the real time temperature‐dependent gas properties. Results of the presented computational analysis are in harmony with the available literature, which not only indicates the reliability of the package but also points out its adaptability to MSc and PhD level research studies and for the compressible flow system design projects.

A computer-assisted approach to industrial gas turbine performance calculation

This article presents a microcomputer‐based, interactive, menu‐driven visual software package developed to investigate design, off‐design, and transient operations of single‐ and twin‐shaft industrial gas turbines, providing mechanical engineering students with the opportunity for flexible operation within the courseware and its software environment.

Slider-bearing design with micro-machined wavy-cavity: Parametric Characterization of thermohydrodynamic-operation-scheme

Slider bearings are widely applied in mechanical systems, where the design needs cover increased load capacity, lowered friction and power consumption and creative designs. This work is governed to perform a parametric characterization, by generating a novel structure on the upper slider surface, which can formally be expressed in micro-machined wavy-form, where the individual and combined influences of various structural design parameters and boundary conditions, on the performance records, are also evaluated. Computations put forward that the contribution of the wave amplitude on power loss values is highly dependent on the level of inlet pressure; higher amplitudes are determined to increase power loss in the lowest inlet pressure case of 1.01, whereas the contrary outcome is determined in the higher inlet pressure cases of 3.01 & 5.01. Designing the slider bearing system, based on optimal load capacity, produced the optimum wave number ranges as 10–45, 7–11 and 5–8 for the pad inclinations of 5°, 4° and 3° respectively.