SIMPLE Pressure Correction Algorithm Research Articles

Numerical modeling and Optimization of Respirational Emergency Drug Delivery Device using Computational Fluid Dynamics and Response Surface Method

Studies have shown that most of the particles sprayed on emergency respirational patients, accumulate inside the endotracheal tube and its connector. In this paper, applying Computational Fluid Dynamics (CFD) and Response Surface Method (RSM), an optimized geometry is introduced for higher efficiency of the drug delivery for patients with emergency respiratory diseases. In CFD modeling, finite volume method and for two-phase flow modeling, Lagrangian method is used. Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model are solved using SIMPLE pressure correction algorithm within the computational domain. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). For optimization process, six different parameters including three dimensions of the connector of the tube: connector length, connector diameter and injection diameter, injection velocity of the drug particles, air flow velocity and particle size are investigated. Using Design of Experiments (DOE) and RSM, the output efficiency of the model and second-order regression equation model are derived and accuracy of the model is confirmed. Then the effect of each input parameter on the efficiency is investigated. Dringer algorithm is applied to optimize the process and the best combination of input parameters yielding the highest efficiency is introduced.

The effect of magnetic field on the performance of new design cyclone separators

In this paper it is attempted to improve the performance of the gas–solid new design cyclones with imposing magnetic fields. First, Eulerian-Lagrangian method is used to model the flow and to track the solid particles within the new design cyclones. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). Then, to investigate the possible influence of the magnetic field, horizontal and vertical distances of the magnetic source from the coordinate origin as influential parameters are investigated. Solid particles with three different diameters and with different materials including polystyrene, ferrous and nickel are used. Results show that applying a magnetic field can improve the collection efficiency for all different particles’ materials. Analysis of results proves that there is a strong correlation between cyclone performances. It is observed that the collection efficiency is very sensitive to vertical distance of the magnetic source from the origin. Moreover, providing higher efficiency without imposing pressure drop is the advantage of implication of a magnetic field.

Numerical study of flow field in new design cyclone separators with one, two and three tangential inlets

Numerical study of the fluid flow and particle dynamics is presented by numerical techniques to characterize the performance of new design cyclone separators with one, two and three tangential inlets. The design of this cyclone is based on the idea of improving cyclone performance by increasing the vortex length. This cyclone differs from a conventional cyclone with the separation space. Instead of conical part, the separation space of this cyclone consists of an outer cylinder and a vortex limiter. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian-Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). In the results the effects of number of inlets on the different important parameters such as pressure drop, collection efficiency, axial velocity and turbulence are investigated and deeply discussed. Contours of velocity, pressure and turbulent kinetic energy within these cyclones with different number of inlets are shown. The results show that the cyclone with three inlets has more collection efficiency, less pressure drop and less turbulence distribution with respect to cyclones with one and two inlets which is good in cyclones performance. Generally it is recommended to use the new cyclone designs with higher number of inlets.

Numerical study of dense solid-liquid flow in hydrodynamic vortex separator applied in recirculating biofloc technology system

Hydrocyclone separation technique has commonly been applied in engineering for solid-liquid separation. In aquaculture, since Hydrodynamic Vortex Separator (HDVS) is able to control flocs concentration effectively, the Recirculating Biofloc Technology (RBFT) has been gradually acknowledged (Zhu et al., 2016). In order to operate RBFT system at maximum performance, the removal efficiency of HDVS at different Hydraulic Retention Time (HRT) must be fully predictable. The aim of this work is to investigate the relationship between separation efficiency and HRT of HDVS applied in RBFT system, through Computational Fluid Dynamics (CFD) method. For this, a three-dimensional unsteady transient model was developed to simulate the hydrodynamics in HDVS based on the commercial software Workbenching 17.0. A Two Fluid Model (TFM) using kinetic theory of granular flow (KTGF) has been developed to describe the dense solid-liquid (flocs-water) flow field of HDVS in RBFT system. Additionally, the Reynolds averaged Navier-Stokes (RANS) equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. Finally, pilot-scale studies were conducted to evaluate the accuracy and precision of simulation models applied. The results indicate that the flocs removal efficiency of HDVS obtained from tests were less than that from the simulation results at three different HRTs. But it decreased with the decline of HRT both for experiment and simulation. Additionally, the CFD model proposed can enhance the fundamental understanding of the effects of HRT on separation efficiency and at the same time, probably coupled with physical experiment whenever necessary, offer a more reliable way for optimum control of HDVS under varying conditions. Based on the simulation results, the flocs management in RBFT system is briefly discussed.

Numerical study of flow field in new cyclone separators

Numerical study of the fluid flow and particle dynamics is presented by numerical techniques to characterize the performance of new cyclone separators. The design of this cyclone is based on the idea of improving cyclone performance by increasing the vortex length. This cyclone differs from a conventional cyclone with the separation space. Instead of conical part, the separation space of this cyclone consists of an outer cylinder and a vortex limiter. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian–Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). In the results the dependency of collection efficiency and pressure drop on different geometrical parameters is investigated. Contours of velocity, pressure and turbulent kinetic energy within these cyclones are shown. Tangential velocity profiles and velocity vectors in different sections are investigated.

Numerical Simulation of Gas Flow Pattern in Cyclone Spray Scrubber

The numerical simulation of the fluid flow is presented by CFD technique to characterize the flow pattern of cyclone spray scrubber. In this process, the Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) for fluid flow are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the fluid computational domain. According to the computational results, the tangential velocity, axial velocity and turbulence intensity of the gas flow are addressed in the different flowrate. The results indicate that the CFD method can effectively reveal the mechanism of gas flow in the cyclone spray scrubber.

Effects of Using Ribs on Flow Pattern and Performance of Cyclone Separators

:In this paper, the effects of using ribs on the flow pattern and performance of cyclone separators are investigated using CFD techniques. The Reynolds averaged Navier-Stokes equations with Reynolds Stress Turbulence Model (RSTM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian-Lagrangian computational procedure is used to predict particles tracks in cyclones with different rib pitch to cyclone diameter (P/D) ratios. The velocity fluctuations are simulated using Discrete Random Walk (DRW). The results show that using ribs in cyclones leads to higher collection efficiency but higher pressure drop and the cyclone with P/D equal to 1 has the maximum collection efficiency among the ribbed cyclones and the cyclone without ribs has the least pressure drop.

Numerical simulation of square cyclones in small sizes

The idea of using square cyclones was first introduced in early 1990s because of some problems of big conventional (round) cyclones in Circulating Fluidized Bed (CFB) industries, such as huge volume and long start-stop time of cyclones. Now there is this question, in spite of the main reason for making square cyclones, how square cyclones behave in small sizes. In this paper, two small cyclones with the same hydraulic diameter, which one is square and the other one is round, are numerically compared. The Reynolds averaged Navier–Stokes equations with Reynolds Stress Turbulence Model (RSTM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian–Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). The results show that the pressure drop in small square cyclone is less than the pressure drop in small round one. Also at each flow rate collection efficiency of small square cyclone is less than round one, but by increasing flow rate this difference decreases.

Numerical simulation of flow field in three types of standard cyclone separators

The numerical simulation of the fluid flow and particle dynamics is presented by CFD techniques to characterize the performance of the three types of standard cyclones. The three types of cyclones named 1D3D, 2D2D and 1D2D. The length of cylindrical part of the body is equal to 1, 2 and 1 times of the body diameter, respectively; and the length of the conical part is 3, 2 and 2 times of the body diameter. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian–Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW ). The dependency of cyclone characteristics on its diameter is investigated and D 50 (Cut-Point) is calculated for different Particle Size Distributions (PSDs). The numerical results are compared with the experimental data and the theoretical model and good agreement is observed.

Simulation of Gas Flow Pattern and Separation Efficiency in Cyclone with Conventional Single and Spiral Double Inlet Configuration

The numerical simulation of the fluid flow and particle dynamics is presented by CFD technique to characterize the performance of two types of cyclones with the conventional single inlet (SI) and spiral double inlets (DI), respectively. The Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) for fluid flow are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the fluid computational domain. A Lagrangian method is employed to track the particle motion and calculate the gas–particle separation efficiency in the cyclones. According to the computational results, the differences of pressure, velocity and turbulence parameters of the gas flow are described to address the effects of the inlet geometry on the flow pattern of cyclones. Especially for the tangential velocity distribution, a key flow parameter in cyclones, are analysed using the classical Rankine vortex theories. Furthermore, the separation performances of cyclones are predicted, with the comparison of experimental data and theoretical model. The results indicate that the CFD method can effectively reveal the mechanism of gas–particle flow and separation in cyclone with different inlet configuration.

Full PDF Modelling of Reactive Sprays Via an Evaporation-Progress Variable

For reactive two-phase flows a single probability density function (PDF) is defined for the totality of all gas-phase and liquid-phase random variables. This single unconditional PDF - or equivalent^ its gas-conditional and liquid-conditional PDF together - allows a complete statistical description and hence a full modelling of reactive, laminar or turbulent, two-phase flows. For the special case of two-phase sprays, for both the gas phase and the liquid phase general PDF-transport equations are given in which the terms concerning the local and instantaneous interaction between the two phases are in closed form but certain turbulence terms would require modelling. The full model is tested by numerically simulating with a particle method two laminar one-dimensional test cases, viz., (i), a non-reactive evaporation and mixing case and, (ii), a case in which evaporation of liquid fuel, mixing of gas-phase species and gas-phase combustion take place. For - but not limited to - the test cases, a (currently but not necessarily) one-dimensional deterministic model based on four reduced variables - notably one of these variables describes the evaporation progress - is developed. For combination with the particle method, a PDF-variant of the SIMPLE pressure-correction algorithm is described.

Calculation of three-dimensional turbulent flow with a finite volume multigrid method

A numerical method for the efficient calculation of three-dimensional incompressible turbulent flow in curvilinear co-ordinates is presented. The mathematical model consists of the Reynolds averaged Navier–Stokes equations and the k–ε turbulence model. The numerical method is based on the SIMPLE pressure-correction algorithm with finite volume discretization in curvilinear co-ordinates. To accelerate the convergence of the solution method a full approximation scheme-full multigrid (FAS-FMG) method is utilized. The solution of the k–ε transport equations is embedded in the multigrid iteration. The improved convergence characteristic of the multigrid method is demonstrated by means of several calculations of three-dimensional flow cases. Copyright © 1999 John Wiley & Sons, Ltd.

A comparison of coarse and fine grain parallelization strategies for the simple pressure correction algorithm

AbstractThe primary aim of this work was to determine the simplest and most effective parallelization strategy for control‐volume‐based codes solving industrial problems. It has been found that for certain classes of problems, the coarse‐grain functional decomposition strategy, largely ignored due to its limited scaling capability, offers the potential for significant execution speed‐ups while maintaining the inherent structure of traditional serial algorithms. Functional decomposition requires only minor modification of the existing serial code to implement and, hence, code portability across both concurrent and serial computers is maintained. Fine‐grain parallelization strategies at the ‘DO loop’ level are also easy to implement and largely preserve code portability. Both coarse‐grain functional decomposition and fine‐grain loop‐level parallelization strategies for the SIMPLE pressure correction algorithm are demonstrated on a Silicon Graphics 4D280S eight CPU shared memory computer system for a highly coupled, transient two‐dimensional simulation involving melting of a metal in the presence of thermal‐buoyancy‐driven laminar convection. Problems requiring the solution of a larger number of transport equations were simulated by including further scalar variables in the calculation. While resulting in slight degradation of the convergence rate, the functional decomposition strategy exhibited higher parallel efficiencies and yielded greater speed‐ups relative to the original serial code. Initially, this strategy showed a significant degradation in convergence rate due to an inconsistency in the parallel solution of the pressure correction equation. After correcting for this inconsistency, the maximum speed‐up for 16 dependent variables was a factor of 5·28 with eight processors, representing a parallel efficiency of 67%. Peak efficiency of 76% was achieved using five processors to solve for 10 dependent variables.

The use of local mode analysis in the design and comparison of multigrid methods

In this paper we carry out a local mode analysis of the symmetric coupled Gauss-Seidel procedure of Vanka [J. Comput. Phys. 65 (1986) 138] and compare the theoretical and practical smoothing rates with those obtained for the SIMPLE pressure correction algorithm of Shaw and Sivaloganathan [Int. J. Num. Methods Fluids 8 (1988) 441].