ParLeda is a software library that provides the basic primitives for parallel ‎implementation of Computational Geometry applications. It can also be used in ‎implementing a parallel application that uses geometric data structures. The parallel ‎model that we use is based on a new heterogeneous parallel model HBSP, which is ‎based on BSP and is introduced here. ParLeda uses two main libraries that are widely ‎used: MPI for its message passing in the parallel environment and LEDA for its data ‎structures and computations. Dynamic load balancing and replicating C++ objects are ‎two key features of this library. This library was implemented after a survey in ‎research on parallel Computational Geometry algorithms and selection of their ‎common primitives‏.‏

Objective: Air-lift bioreactors can play an important role in tissue engineering because of many advantages, such as; simplicity of construction, absence of moving parts, easy sterilization and low power consumption. However, optimum design of airlift bioreactors for cultivation of stem cells is still a difficult task, because of complicated relations between mixing and mass transfer, and also high sensitivity of stem cells to shear stress. In this study, Computational fluid dynamics (CFD) analysis using related software was used to characterize an internal loop airlift bioreactor for stem cell proliferation. The effect of Geometry parameters such as sparger position and configuration, ratio of the downcomer to the riser area (Ad/Ar), and height of liquid above (Ha) and below (Hb) of the draft tube was considered to identify the complex hydrodynamic environment as well as shear stress applied to suspension culture of stem cells. The results demonstrated that sparger position and configuration has maximum effect on shear stress exposure on cell although shear stress can be reduced with increasing Ha in this area. In addition, large Ad/Ar was found to be useful for minimum exposure shear stress on cells while it has negative effect on cell distribution as same as Hb. Therefore, optimum design of air-lift bioreactor can be achieved by CFD analyzing with comprehensive considering of hydrodynamic environment to apply this type of bioreactor in tissue engineering without performing costly time-consuming experiments.Materials and Methods: Computational fluid dynamic software (ANSYS 14.0) was used to consider geometric parameters of air-lift bio-reactor hydrodynamic environment to apply this kind of bio-reactor in tissue engineering for expanding stem cells.Results: The effect of Geometry parameters such as sparger position and configuration, ratio of the downcomer to the riser area (Ad/Ar), and height of liquid above (Ha) and below (Hb) of the draft tube was considered to identify the complex hydrodynamic environment as well as shear stress applied to suspension culture of stem cells. The results demonstrated that sparger position and configuration has maximum effect on shear stress exposure on cell because of effected on bubble formation and Geometry. Although shear stress can be reduced with increasing Ha in this area, in addition, large Ad/Ar was found to be useful for minimum exposure shear stress on cells while it has negative effect on cell distribution as same as Hb.Conclusion: As the above results show, optimum design of air-lift bio-reactor can be achieved by CFD analyzing with comprehensive considering of hydrodynamic environment to evaluate applicability of air-lift bio-reactor in tissue engineering without performing costly time-consuming experiments.

In the present work, an effective way is introduced to improve the efficiency of a square cyclone separator. For this aim, a dipleg is attached under the square cyclone to investigate its Geometry effect on the performance of square cyclone separator. A three-dimensional Computational fluid dynamics simulation is done by solving the Reynolds averaged Navier Stokes equations with the Reynolds stress model turbulence model and using the Eulerian-Lagrangian two phase method. The particle dispersion due to turbulence in the gas phase is predicted using the discrete random Walk model. The predicted results show that using a dipleg although produces an increase in pressure drop but it positively enhances the separation efficiency of the square cyclone. In the present results, the pressure drop is increased by about 19% by using dipleg at an inlet velocity of 28 m/s. Using dipleg significantly increases the separation efficiency of square cyclone especially at higher inlet velocity. This can be more obvious when using dipleg 1 which is minimized the 50% cut size of square cyclone by about 35.5%. Also, in higher inlet velocity, the reduction value of 50% cut size is higher which is proved that using dipleg is more effective due to stronger swirl flow.

Dual-throat Nozzle (DTN) is known as one of the most effective approaches of fluidic thrust-vectoring. It is gradually flourishing into a promising technology to implement supersonic and hypersonic thrust-vector control in aircrafts. The main objective of the present study is numerical investigation of the effects of secondary injection Geometry on the performance of a fuel-injected planar dual throat thrust-vectoring nozzle. The main contributions of the study is to consider slot and circular geometries as injector cross-sections for injecting four different fuels, moreover, the impact of center-to-center distance of injection holes for circular injector is examined. Three-dimensional compressible reacting simulations have been conducted in order to resolve the flowfield in a dual throat nozzle with pressure ratio of 4. 0. Favre-averaged momentum, energy and species equations are solved along with the standard k-ε model for the turbulence closure, and the eddy dissipation model (EDM) for the combustion modelling. Second-order upwind numerical scheme is employed to discretize and solve governing equations. Different assessment parameters such as discharge coefficient, thrust ratio, thrust-vector angle and thrust-vectoring efficiency are invoked to analyze the nozzle performance. Computationally predicted data are agreed well with experimental measurements of previous studies. Results reveal that a maximum vector angle of 17. 1 degrees is achieved via slot injection of methane fuel at a secondary injection rate equal to 9% of primary flow rate. Slot injection is performing better in terms of discharge coefficient, thrust-vector angle and thrust-vectoring efficiency, whereas circular injection provides higher thrust ratio. At 2% secondary injection for methane fuel, vector angle and vectoring efficiency obtained by slot injector is 8% and 34% higher than the circular injector, respectively. Findings suggest that light fuels offer higher thrust ratio, vector angle and vectoring efficiency, while heavy fuels have better discharge coefficient. Increasing center-to-center distance of injector holes improves thrust ratio, while having a negative effect on discharge coefficient, vector angle and vectoring efficiency. A comparison between fuel injectant of current study and inert injectant in the previous studies indicates that fuel reaction could exhibit substantial positive effects on vectoring performance. Secondary-to-primary momentum flux ratio is found to play a crucial role in nozzle performance.