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The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by piezo – viscous couple stress lubricant with pressure-dependent viscosity variation.

Based upon the Stokes couple stress theory, Barus viscosity-pressure dependency relation and Christensen rough surfaces model, squeeze film characteristics between two rough parallel circular discs are obtained.

According to the results, it is found that, the combined effects of couple stresses and viscosity-pressure dependency increases squeeze film performance with respect to the classical Newtonian iso-viscous (constant viscosity) lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it.

This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with viscosity-pressure dependency, rotational inertia, couple stresses and surface roughness effects.

The purpose of this paper is to study the dimensionless characteristics of a molten salt pump and propose an approach to carry out the modeling experiment by using water instead of molten salts.

External characteristics of the pump were estimated by using the steady flow model and compared with the experimental results. By taking water as the working fluid, the pathlines in the volute of the model pump were validated by the results obtained of high-speed photography. According to the derived dimensionless characteristics of the molten salt pump, the modeling experimental schemes were proposed. Adopting the validated numerical simulation model, the performance of the molten salt pump was studied in detail.

The modeling experimental schemes designed according to the dimensionless characteristics are theoretically feasible. However, to carry out the experiment successfully, factors such as rotational speed, geometric size, flow rate and head should be taken into account. The flow in the pumps is similar under the similar operating condition and the external characteristics of the similar pump can be converted to each other. Compared with transporting water, the decline of the head and efficiency is within 5 per cent when the viscosity is lower than 0.01453 Pa · s. The pump is not suitable for running under the critical Reynolds number of 1.0 × 10⁷.

The current work revealed the relationships among the dimensionless performances of a molten salt pump and proposed a critical Reynolds number Re_Qcr for the pump running.

The purpose of this work is to study heat and mass transfer from mixed convection flow of polar fluid along a plate in porous media with chemical reaction.

The governing equations for this problem are solved numerically.

Polar fluids behave very differently from Newtonian fluids.

This work is original as little work has been reported for polar fluids.

A boundary layer solution is presented to the steady free convection from a vertical plate with uniform surface heat flux conditions and immersed in a micropolar fluid. Numerical solutions for governing nonsimilar boundary layer equations are presented for a range of values of the material properties and Prandtl number of the fluid. An asymptotic solution is developed for large distances away from the leading edge.

Laser sintering kinetics and part reliability are critically dependent on the melt viscosity of materials, including polyamide 12 (PA‐12). The purpose of this paper is to characterise the viscosity of PA‐12 powders using alternative scientific methods: constrained boundary flows (capillary rheometry) and rotational rheometry.

Various PA‐12 powders were selected and characterised by both techniques. Measurement of molecular weight was also carried out to interpret the viscosity data.

Results demonstrate conventional pseudoplastic flow in all PA‐12 materials. Zero‐shear viscosity has been quantified by rotational rheometry; a notable observation is the striking difference between virgin/used PA‐12. This is interpreted in terms of molecular weight and chain structure modifications, arising from polycondensation of PA‐12 held at the bed temperature during laser sintering.

Accurate zero‐shear viscosity data provide scope for use in predictive computational models for laser sintering processes. Careful sample preparation and equipment operation are critical prerequisites for accurate rheological characterisation of PA‐12 powders.

Differences in flow behaviour and molecular structure allow prediction and deeper understanding of process‐property relationships in laser sintering, giving potential for further optimisation of material specification and in‐process machine parameter control.

This is believed to be the first time that techniques other than melt flow rate (MFR) have been reported to measure the viscosity of PA‐12 in a laser sintering context, noting the effects of pre‐drying and molecular weight, then predicting differences between virgin/used powders in practical sintering behaviour.

The purpose of this study is to investigate the rheological behaviour of commercial lubrication oils used for cylinder lubrication in two-stroke marine diesel engines. Furthermore, it is of interest to investigate whether the viscosity of lubrication oils is affected by different levels of alkalinity.

Viscosity measurements are performed using both rotational and capillary rheometry. It was possible to measure oil viscosity in the shear rate from 0.1 to 3,000 s⁻¹ using rotational rheometry, whereas capillary rheometry allowed measurements in higher shear rates from 5 × 10⁵ to 1.3 × 10⁶ s⁻¹ at 50°C.

The viscosity measurements show that the studied lubrication oils behave as a Newtonian fluid and that the viscosities are insensitive to the level of alkalinity. Furthermore, the viscosity/temperature dependency for the lubrication oils was found to fit the Arrhenius model.

This study presents useful information about the rheological behaviour of lubrication oils, more precisely how the oil properties are affected by shear rate, temperature and level of alkalinity. The value of this research is considered to be important for designing two-stroke diesel engines and cylinder lubrication systems.

The purpose of this paper is to study the working characteristics of hydro-viscous clutch at high rotational speeds and obtain the trend of flow field variation of oil film.

The FLUENT simulation model of the oil film between the friction disks is built. The effect of variation of working parameters such as input rotational speed, oil flow rate and film thickness on two-phase flow regime and transmission torque is studied by using the volume of fluid model.

The results show that the higher the rotational speed, the severer the cavitation is. In addition, the two-phase flow region makes the coverage of oil film over the friction pairs’ surface reduce, which results in a decrease in transmission torque for the hydro-viscous clutch.

These simulation results are of interest for the study of hydro-viscous drive and its applications. This study can also provide a theoretical basis for power transmission mechanism of oil film by considering the existence of a two-phase flow regime consisting of oil and air.

The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by ferro-fluid couple stress lubricant.

Based upon the Stokes couple stress theory, ferro-hydrodynamic model of Shliomis and Christensen rough surfaces model, squeeze-film characteristics between two rough parallel circular discs considering rotational inertia effects are obtained.

According to the results, it is found that the combined effects of couple stresses and ferro-fluid lubricants increases squeeze film performance with respect to the classical Newtonian lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it.

This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with ferro- fluid, rotational inertia, couple stresses and surface roughness effects.

The purpose of this paper is to show how to find the regions of dynamic instability of a beam axially loaded and visco‐elastically constrained at its ends by Kelvin‐Voigt translational and rotational units variously arranged according to different configurations, by using the equation of boundary frequencies.

With respect to visco‐elasticity the time variable is present as a parameter so that the above‐mentioned exact approach is exploited to draw three‐dimensional diagrams of the dynamic component of the periodic load and its frequency, varying with time and with the viscosity parameter μ characterizing the restraints.

For not rigidly constrained configurations a peculiar asymptotic tendency is recognizable in both cases.

The study allows for identifying the influence of visco‐elastic restraints in the response of a beam under a dynamic axial load. Dynamic excitation occurs in several fields of mechanics: dynamic loads are encountered in structural systems subjected to seismic action, aircraft structures under the load of a turbulent flow and industrial machines whose components transmit time‐dependant forces.

Visco‐elasticity accounts for possible vibration control solutions planned to improve the dynamic response of the rod; they can consist of layers of visco‐elastic material within the body of the modelled element or local viscous instruments affecting the boundary conditions; the latter is the application this paper focuses on.

With this paper a calculation procedure to get an exact solution for particular static configurations of the beam is followed in order to define the influence of visco‐elastic restraints under a dynamic axial load; the responses are given in terms of boundary frequencies domains and are supposed to be useful to learn the behaviour in time and in dependence of the intrinsic viscosity of the restraints.

The purpose of this paper is to investigate squeezing and rotating motions between two parallel annular discs lubricated by ferro-fluid couple stress lubricant in the presence of a uniform magnetic field.

Based upon the Stokes couple stress theory and ferro-hydrodynamic model of Shliomis, squeeze film characteristics between two parallel annular discs are obtained.

According to the results, it is found that the combined effects of couple stress and ferro-fluid lubricant increase squeeze film performance with respect to the classical Newtonian lubricant. However, an increase in the rotational inertia parameter reduces squeeze film characteristics.

This paper is relatively original and describes the squeeze film characteristics between two parallel annular discs with rotational inertia, couple stress and ferro-fluid lubricant effects.