Ighoroje W. A. Okuyade, Tega Okor

The problem of transient MHD free convective chemically reacting fluid flow past a hot vertical porous plate with the attendant effects of thermal radiation, heat source and varying wall temperature, concentration and suction is investigated. The governing non-linear and coupled partial differential equations are non-dimensionalized, and linearized using the oscillating perturbation series expansion solutions. The resulting equations are solved and the expressions for the temperature, concentration, velocity, Nusselt number, Sherwood number and force on the plate wall are obtained. The flow characteristics are quantified and presented graphically. The results, amidst others, show that increase in the Hartmann number increases the velocity and skin friction; increase in the convection force increases the velocity and skin friction. Furthermore, it is seen that increase in the Raleigh number increases the temperature, velocity and skin friction but decreases the rate of heat transfer; increase in the heat source parameter increases the temperature, velocity and skin friction but decreases the rate of heat transfer; increase in the chemical reaction rate increases the concentration, Sherwood number, and velocity and skin friction. These results are bench-marked with the results in some existing literatures and they are in agreement.

]]>Mohammed A. Azim

In this study, the developing region of coaxial jets is investigated numerically by varying the swirl for a fixed velocity ratio. Obtained results show that the mean flow properties and fluctuating concentration of the jet fluids except for the swirl velocity and helicity remain unaffected for the change in swirl ratio. Further, the helicity profiles indicate that the spiral motion due to helicity may create some large-scale structures at low swirl.

]]>Hafizul Islam, Md. Mashiur Rahaman, Hiromichi Akimoto

The paper presents a case study for resistance and motion behavior of a tanker ship in oblique waves. Initially, head wave cases were simulated for the KRISO Very Large Crude Carrier 2 (KVLCC2) model using an in-house Reynolds averaged Navier Stokes (RaNS) solver, SHIP_Motion, and results are validated with experimental data. Next, simulations were performed to study the dependence of resistance prediction on ship’s degrees of freedom of motion. Finally, oblique wave (bow wave) simulations were performed with five Degrees of Freedom (5DOF) for incoming waves with 30° and 60° heading. The oblique wave results were reproduced using a potential flow based commercial solver for comparison. The paper concludes that the added resistance coefficient curve takes a leftward shift (towards shorter wave length) with reduced peak amplitude because of ship’s encountered wave length and motion response in oblique waves.

]]>Andriamahefasoa Rajaonison, Hery Tiana Rakotondramiarana

A new type of hydraulic ram pump, called "Raseta pump", was invented, patented and crafted in Madagascar. The peculiarity of this hydram pump over conventional ones is that there is a spring in each of the waste and delivery valves. In addition, the usual air balloon is replaced by a balloon with 4 springs. Thus, this paper aims at theoretically studying the behaviour of this hydram pump equipped with a system of springs. For that purpose, a model associated with the studied hydram pump was developed and coded on Matlab. Then, a global sensitivity analysis was carried out for identifying the most influential parameters of this model while successively considering as the surveyed model outputs: the amount of wasted water, the amount of pumped water and the efficiency of the pump. As results, the most dominating parameters are relatively the same as those found by previous works on the conventional hydram pump without springs: height of the water column in the delivery pipe, the height of supply tank, the weight of the waste valve, and the length of the waste valve stroke. However, there are 3 other parameters that the present study exceptionally found as among the most influential ones as well, namely: the stiffness of the spring in the waste valve, the modulus of elasticity of the fluid, and the radius of the waste valve disk. In addition, similar to the case of air balloon, the effect of the spring balloon is not relevant. An extension work could be a techno-economic investigation of a pump system constituted by a number of hydram pumps similar to the one studied here for increasing water head in a pico hydropower plant.

]]>Ashkan Shokrian, Hossein Mobli, Abbas Akbarnia, Ali Jafari, Hossein Mousazade, Baoshan Zhu

A computational fluid dynamics (CFD) simulation of solid–liquid–liquid three-phase flow was carried out on for the multiphase complex fluid flow motion in a centrifugal separate machine (Tricanter). An Euler–Euler, multiphase-flow model was used for the three-phase flow simulation. This centrifugal device is designed for separated three – phase flow, two- phase liquid (water and olive oil) and one phase solid materials (olive pomace). Results from the three-dimensional CFD include velocity and pressure distribution for solid phase flow. The simulations indicate that the velocity of solid material in near the surface bawl is maximum value but velocity in near the outer surface scroll is zero then causes the suspended solids to settle, and accumulate at the scroll wall. Also the pressure at the middle of the tricanter was lower than atmospheric pressure.

]]>E. O. Odok, C. Israel-Cookey, E. Amos

The onset of stationary and oscillatory magnetoconvection in a rotating infinitely horizontal porous layer filled with electrically conducting Newtonian fluid heated from below with temperature – dependent heat source within the Darcy limit using linear stability analysis is investigated for free – free boundaries. The effects of heat source, magnetic field and rotation parameters on the onset of convection are presented graphically and analyzed in detail. It is found that increases in magnetic and rotation parameters delayed the onset of stationary and oscillatory convection, thereby stabilizing the system. The heat source parameter increment accelerates the onset of convection and the system is more unstable; while Prandtl number slowed the onset of oscillatory convection.

]]>Reza Amini, Mehdi Kashfi, Mohsen Amini

Numerical study of effective parameters on natural convection heat transfer in a dry cooling tower is carried out by using the commercial software of Ansys-Fluent. The modelled dry cooling tower has the same geometry as in Shahid Rajaee power plant in Iran. For a particular performance of the cooling tower, numerical and experimental results are compared, and suitable algorithm and turbulence model are determined. Results show that k-e-RNG full buoyancy effect model is the most accurate approach for modeling the turbulence and COUPLED algorithm is the best for solving for the coupling between pressure and velocity fields. Grid independency is validated, and the best numerical grid is selected. Due to presence of external flow, domain independency is also checked, and the best domain is selected. Effect of wind and force convection on cooling process is also studied. At the end, effect of high velocity air injection on increasing momentum and efficiency of the cooling process is studied. At moderate atmospheric condition, air injection slightly improves the amount of heat transfer, but it can reinforce the flow in unstable conditions like stormy weather and thus sustain the cooling process.

]]>Atta Sojoudi

Mathematical modeling was performed to simulate mixed convection of Al_{2}O_{3}-Water nanofluid in a lid-driven triangular cavity employing the Lattice Boltzmann Method (LBM). Two inclined cold walls are kept at constant temperatures where the bottom lid-driven wall is subjected to sinusoidal thermal boundary condition. Different thermal conductivity and viscosity of working nanofluid were considered. The study was carried out for different Richardson numbers, 0.01≤*Ri*≤100, Aspect Ratios, 0.2≤*AR*≤1, nanoparticle solid volume fractions, 1%≤*φ*≤5% and different frequencies and amplitudes of sinusoidal thermal forcing of lid-driven wall. Results are presented in terms of stream function and temperature contours and mean Nusselt number of all heated walls at steady state condition. To have a better insight into the fluid flow, horizontal component of fluid velocity was plotted at mid-section of the cavity for all studied cases. The grid sensitivity test was carried out and results were validated against the experimental study.

Aliakbar Babajani

Ocean waves are one of the energy resources which have potential to fulfil some parts of the world’s energy requirements. Recently, existing OWECs have been evaluated to ﬁnd the most appropriate systems for the wave energy extraction of the Caspian Sea. Hence, point absorbers are found to be the most appropriate devices for this sea. Generally, the aim of this study is to study a novel ocean wave energy converter named “Searaser” which may be economical and practical for the Caspian Sea. Thus, this study presents a numerical simulation of Searaser inside a wave tank using commercial software (Flow-3D). In order to validate the simulations, the numerical and experimental results were compared with a point absorber and the both were in reasonable agreement. Afterwards, the performance of Searaser was numerically calculated for different heights of ocean waves. Accordingly, the obtained results indicate that the output flow rate and the power generation increase significantly by increment of wave heights, and using this device may have the potential to be practical and profitable for industrial applications by improving its system.

]]>Yan Zhihong, Qian Yingping, Huang Wei, Zhou Xizhi, Gong Xuedan

In this paper, the technical features of conformal cooling and enhanced heat transfer are combined. The method of heat transfer enhancement with corrugated conformal channel is proposed. The effect of size structure parameters of corrugated conformal cooling channel on heat transfer enhancement is studied. Nine corrugated conformal heat transfer structures have been established. Fluent was used to simulate the cooling of nine different design variables. The temperature and water flow velocity of various structural parameters obtained through simulation were plotted. In addition, corresponding temperature curves and water flow velocity curves were drawn. In this paper, In order to further confirm that the corrugated channel has a better heat transfer effect than the channel with the equal cross section, the temperature distribution, pressure drop distribution and water flow velocity are used as evaluation indexes to study the influence of heat transfer between corrugated channel and equal-section channel. In summary, the corrugated conformal channel has a higher heat transfer effect than the conformal water channel, and the structural parameters of the various corrugated channels are different, and the impact on the heat transfer effect is also different.

]]>