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The purpose of this study is to investigate the inner flow field characteristics of groove textures in thrust bearings. Cavitation and vortex are studied simultaneously to enrich the theories of surface texture.

Navier–Stokes equations are solved using computational fluid dynamics. The MIXTURE model is adopted to study the gas–liquid mixture flow under the cavitation condition.

Re number, the depth ratio as well as the area ratio of the groove texture and the bottom shape are all influencing factors of the inner flow field characteristics. When cavitation region and vortex region occupy the bottom of the groove texture, these do not overlap because of the pressure gradient. The positive pressure gradient in the non-cavitation region introduces nonlinearity into the velocity profiles, which affects the load-carrying capacity and friction.

Cavitation and vortex are studied simultaneously only in this study. The characteristics of the textured thrust bearing can be analyzed and explained with the combined effect of cavitation and vortex.

The emission from marine engines has a crucial effect on energy economy and environment pollution. One of the effective emission reduction schemes is to minimize the friction loss of main friction pairs such as cylinder liner-piston ring (CLPR). Micro-groove textures were designed to accomplish this aim.

The authors experimentally investigated the effects of micro-groove textures at different cylinder liner positions. The micro-groove texture was fabricated on samples by chemical etching and cut from the real CLPR pair. Sliding contact tests were conducted by a reciprocation test apparatus.

The average friction coefficient of grooves at 30° inclination were reduced up to 58.22% and produced better tribological behavior at most conditions. The operating condition was the critical factor that determined the optimum texture pattern. The surface morphology indicated that textures could produce smoother surfaces and less scratches as compared with the untextured surface.

Inclined grooves and V-grooves were designed and applied to real CLPR pairs. The knowledge obtained in this study will lead to practical basis for tribological design and manufacturing of CLPR pair in marine diesel engines.

The purpose of the present study is to investigate the flow and turbulence characteristics of a turbulent wall jet flowing over a surface inclined with the horizontal and to investigate the effect of variation of the angle of inclination of the wall on the flow structure of the wall jet.

The high Reynolds number two-equation κ− model with standard wall function is used as the turbulence model. The Reynolds number considered for the present study is 10,000. The Reynolds averaged Navier-Stokes (RANS) equations are used for predicting the turbulent flow. A staggered differencing technique employing both contravariant and Cartesian components of velocity has been applied. Results for distribution of wall static pressure and skin friction, decay of maximum streamwise velocity, streamwise variation of integral momentum and energy flux have been compared for the cases of α=0°, 5°, and 10°.

Flow field has been represented in terms of streamwise and lateral velocity contours, static pressure contour, vorticity contour and streamwise velocity and static pressure profiles at different locations along the oblique offset plate. Distribution of Reynolds stresses in terms of spanwise, lateral and turbulent shear stresses, and turbulent kinetic energy and its dissipation rate have been presented to describe the turbulent characteristics. Similarity of streamwise velocity and the velocity parallel to the oblique wall has been observed in the developed region of the wall jet flow. A decaying trend is observed in the variation of total integral momentum flux in the developed region of the wall jet which becomes more evident with increase in oblique angle. Developed flow region has indicated trend of similarity in profiles of streamwise velocity as well as velocity component parallel to the oblique wall. A depression in wall static pressure has been observed near the nozzle exit when the wall is inclined and the depression increases with increase in inclination. Effect of variation of oblique angles on skin friction coefficient has indicated that it decreases with increase in oblique angle. Growth of the outer and inner shear layers and spread of the jet shows linear variation with distance along the oblique wall. Decay of maximum streamwise velocity is found to be unaffected by variation in oblique angle except in the far downstream region. The streamwise variation of spanwise integral energy shows increase in oblique angle and decreases the magnitude of energy flux through the domain. In the developed flow region, streamwise variation of centreline turbulent intensities shows increased values with increase in oblique angle, while turbulence intensities along the jet centreline in the region X<12 remain unaffected by change in oblique angles. Normalized turbulent kinetic energy distribution highlights the difference in turbulence characteristics between the wall jet and reattached offset jet flow. Near wall velocity distribution shows that the inner region of boundary layer of the developed oblique wall jet follows a logarithmic profile, but it shows some difference from the standard logarithmic curve of turbulent boundary layers which can be attributed to an increase in skin friction coefficient and a decrease in thickness of the wall attached layer.

The study presents an in-depth investigation of the interaction between the jet and the inclined wall. It is shown that due to the Coanda effect, the jet follows the nearby wall. The findings will be useful in the study of combined flow of wall jet and offset jet and dual offset jet on oblique surfaces leading to a better design of some mechanical jet flow devices.

The purpose of this paper is to recommend a validated numerical model for simulation the flue gases heat recovery recuperators. Due to fulfill of this demand, the influences of ash fouling characteristics during the transient/steady-state simulation and optimization of a 3D complex heat exchanger equipped with inner plain fins and side plate fins are studied.

For the particle dispersion modeling, the discrete phase model is applied and the flow field has been solved using SIMPLE algorithm.

According to obtained results, for the recuperator equipped with combine inner plain and side plate fins, determination of ash fouling characteristics is really important, effective and determinative. It is clear that by underestimating the ash fouling characteristics, the achieved results are wrong and different with reality.

Finally, the configuration with inner plain fins with characteristics of: d_i =5 mm, d_o = 6 mm, d_g = 2 mm, d_k = 3 mm and NIPFT = 9 and side plate fins with characteristics of: T_F = 3 mm, P_F = 19 mm, NSPF = 17·2 = 34, W_F = 10 mm, H_F = 25 mm, L_F = 24 mm and ß = 0° is introduced as the optimum model with the best performance among all studied configurations.

A mathematical model has been developed to study incompressible, isothermal, turbulent, confined, swirling flows. The model solves the conservation equations of mass, momentum, and two additional equations for the turbulent kinetic energy and the rate of dissipation of turbulent kinetic energy. The numerical predictions show a recirculation zone in the form of a one‐celled toroidal vortex at the combustor centreline. High levels of turbulence characterize the recirculation zone. The length, diameter and maximum velocity of the recirculation zone first decrease and then increase as the magnitude of the outer swirl number is first decreased from counter‐swirl to zero and then increased to co‐swirl flow conditions. Counter‐swirl produces steeper velocity gradients at the inter‐jet shear layer and promotes faster mixing than co‐swirl. The numerical results also indicate that the mass of the recirculation zone first decreases and then increases as the outer swirl number is first decreased from counter‐swirl to zero and then increased to co‐swirl conditions. The diameter, maximum velocity and mass of the recirculation zone are monotonically increasing functions of the inner jet swirl number. The recirculation zone length, diameter and mass are almost independent of the Reynolds number and outer‐to‐inner jet axial velocity ratio.

The purpose of this study is to numerically examine the mixed convection of CuO-water nanofluid due to a rotating inner hot circular cylinder in a 3D cubic enclosure with phase change material (PCM) attached to its vertical surface. Heat transfer and fluid flow characteristics were examined for various values of pertinent parameters.

Finite element method was used in the numerical simulation. Influence of various pertinent parameters such as Rayleigh number (between 10$^5$ and 10$^6$), Hartmann number (between 0 and 100), angular rotational speed of the cylinder (between −50 and 50), solid nanoparticle volume fraction (between 0 and 0.04) and PCM parameters (height-between 0.2H and 0.8H, thermal conductivity ratio- between 0.1 and 10) on the convective heat transfer characteristics are numerically studied.

It was observed that local heat transfer variations along the hot surface differ significantly for the cases with and without magnetic field where three distinct hot spots of peak Nusselt number are established when magnetic field is imposed. The average Nusselt number enhancement with the nanofluid at the highest particle volume fraction is 52.85 per cent at Hartmann number of 100, whereas its value is 39.76 per cent for the case in the absence of magnetic field. When the inner cylinder rotates, flow and thermal fields are affected within the cavity. The local heat transfer variations spread over the hot surface with cylinder rotation and 16.43 per cent of reduction in the average heat transfer is obtained with counter-clockwise rotation at 100 rad/sec. An enhancement in the PCM height and a reduction in the thermal conductivity of the PCM result in average heat transfer deterioration for the 3D cavity. The amount of the reduction is 43 per cent when the PCM height is increased from 0.2H to 0.8H, whereas 19.10 per cent enhancement in the heat transfer is achieved when thermal conductivity ratio (PCM) to the base fluid is increased from 0.1 to 10.

Such configurations can be designed for convection control, and in our case, various methods are available. Some of the investigated methods can be used in applications where magnetic field already exists. Convection control study in 3D cavity gives more realistic results as compared to 2D configurations, and results of the current investigation may be used for the design, optimization and flow control of many thermal applications involving magnetic field effects.

A numerical study is performed to investigate turbulent Couette flow and heat transfer characteristics in concentric annuli with a slightly heated inner cylinder moving in the flow direction. A two‐equation k‐ε turbulence model is employed to determine the turbulent viscosity and the turbulent kinetic energy. The turbulent heat flux is expressed by Boussinesq approximation in which the eddy diffusivity for heat is given as functions of the temperature variance t^2‐ and the dissipation rate of temperature fluctuations ε_t, together with k and ε. The governing boundary‐layer equations are discretized by means of control volume finite‐difference technique and numerically solved using a marching procedure. It is disclosed from the study that the streamwise movement of the inner core causes substantial reductions in the turbulent kinetic energy and the temperature variance, particularly near the inner wall region, resulting in the deterioration of the Nusselt number, and that an attenuation in heat transfer performance is induced by the velocity ratio of the moving inner cylinder to the fluid flow.

The purpose of this study is to explore the transient characteristics of mixed-flow pumps during startup process.

This study uses a full-flow field transient calculation method of mixed-flow pump based on a closed-loop model.

The findings show the hydraulic losses and internal flow characteristics of the piping system during the start-up process.

Large computational cost.

Improve the accuracy of current numerical simulation results in transient process of mixed-flow pump.

Simplify the setting of boundary conditions in the transient calculation.

The time of tightly coupled transient calculation and the accuracy of conventional loosely coupled algorithm make it difficult to meet the engineering design requirements for long-term conjugate heat transfer (CHT) problems. The purpose of this paper is to propose a new loosely coupled algorithm with sufficient accuracy and less calculation time on the basis of the quasi-steady flow field. Through this algorithm, it will be possible to reduce the update frequency of the flow field and devise a strategy by which to reasonably determine the update steps.

In this paper, the new algorithm updates the flow field by solving the steady governing equations in the fluid region and by calculating the transient temperature distribution until the next update of the fluid flow, by means of solving the transient energy equations in the entire computational domain. The authors propose a strategy by which to determine the update step, by using the engineering empirical formula of the Nusselt number, on the basis of the changes of the inlet and outlet boundary conditions.

Taking a duct heated by an inner forced air flow heating process as an example, the comparison results for the tightly coupled transient calculation by Fluent software shows that the new algorithm is able to significantly reduce the calculation time of the transient temperature distribution with reasonable accuracy. For example, the respective computing times are reduced to 22.8 and 40 per cent, while the duct wall temperature deviations are 7 and 5 per cent, using the two flow update time steps of 100 and 50 s on the variable inlet-flow rate conditions.

The new algorithm outlined in this paper further improves the calculated performance and meets the engineering design requirements for long-term CHT problems.

The purpose of this paper is to investigate flow behavior of electrorheological (ER) fluid in a closed piston–cylinder system.

A basic study of flow characteristics of ER fluid in a damper model is conducted experimentally and numerically. The electric field is applied between inner wall of the cylinder and outer wall of the piston, and the pressure difference between upper and lower chamber of the cylinder is measured. A numerical prediction of ER fluid flow in the damper model system is performed in order to study the ER fluid flow characteristics. Visualization experiment is also made and used to qualitatively verify the numerical formulation.

The agreement between the numerical predictions and experimental results is encouraging, and the ER fluid flow patterns under different piston aspect ratios, movement speeds and applied electric field strengths are presented. The results show that the piston aspect ratio has much smaller influence on the ER flow pattern than other influencing factors. Increasing piston movement speed or reducing the electric field applied is helpful to reduce the pressure response time period, which is an important indicator showing sensitiveness of the damper. It is also seen that the pressure difference between the upper and lower chamber of the cylinder increases with the electric field strength and the piston movement speed.

First time the detailed investigation into the hydrodynamics behavior in such working models of engineering applications for ER fluid.