Modeling Dilute Gas–Solid Flows Using a Polykinetic Moment Method Approach

Modeling a dilute suspension of particles in a polykinetic Eulerian framework is described using the conditional quadrature method of moments (CQMOM). The particular regimes of interest are multiphase flows comprised of particles with diameters small compared to the smallest length scale of the turbulent carrier flow and particle material densities much larger than that of the fluid. These regimes correspond to moderate granular Knudsen number and large particle Stokes numbers in which interparticle collisions and/or particle trajectory crossing (PTC) can be significant. The probability density function (PDF) of the particle velocity space is discretized with a two-point quadrature, the minimum resolution required to capture PTC which is common to these flows. Both two-dimensional (2D) test cases (designed to assess numerical procedures) and a three-dimensional (3D) fully developed particle-laden turbulent channel flow were implemented for collisionless particles. The driving gas-phase carrier flow is computed using direct numerical simulation of the incompressible Navier–Stokes (N–S) equations and one-way coupled to the particle phase via the drag force. Visualizations and statistical descriptors demonstrate that CQMOM predicts physical features such as PTC, particle accumulation near the channel walls, and more uniform particle velocity profiles relative to the carrier flow. The improvements in modeling compared to monokinetic representations are highlighted.

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A Code for Simulating Heat Transfer in Turbulent Channel Flow

Mathematics ◽

10.3390/math9070756 ◽

2021 ◽

Vol 9 (7) ◽

pp. 756

Author(s):

Federico Lluesma-Rodríguez ◽

Francisco Álcantara-Ávila ◽

María Jezabel Pérez-Quiles ◽

Sergio Hoyas

Keyword(s):

Heat Transfer ◽

Stokes Equations ◽

Three Dimensional ◽

Turbulent Channel Flow ◽

Passive Scalar ◽

Direct Numerical Simulations ◽

Time Dependent ◽

Navier Stokes ◽

Thermal Flow ◽

Navier Stokes Equations

One numerical method was designed to solve the time-dependent, three-dimensional, incompressible Navier–Stokes equations in turbulent thermal channel flows. Its originality lies in the use of several well-known methods to discretize the problem and its parallel nature. Vorticy-Laplacian of velocity formulation has been used, so pressure has been removed from the system. Heat is modeled as a passive scalar. Any other quantity modeled as passive scalar can be very easily studied, including several of them at the same time. These methods have been successfully used for extensive direct numerical simulations of passive thermal flow for several boundary conditions.

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A Calculation Scheme for Three-Dimensional Viscous Incompressible Flows

Journal of Fluids Engineering ◽

10.1115/1.3242670 ◽

1987 ◽

Vol 109 (4) ◽

pp. 345-352 ◽

Cited By ~ 4

Author(s):

M. Reggio ◽

R. Camarero

Keyword(s):

Incompressible Flows ◽

Stokes Equations ◽

Three Dimensional ◽

Numerical Procedure ◽

Numerical Data ◽

Momentum Balance ◽

Navier Stokes ◽

Test Cases ◽

Pressure Gradients ◽

Navier Stokes Equations

A numerical procedure to solve three-dimensional incompressible flows in arbitrary shapes is presented. The conservative form of the primitive-variable formulation of the time-dependent Navier-Stokes equations written for a general curvilinear coordiante system is adopted. The numerical scheme is based on an overlapping grid combined with opposed differencing for mass and pressure gradients. The pressure and the velocity components are stored at the same location: the center of the computational cell which is used for both mass and the momentum balance. The resulting scheme is stable and no oscillations in the velocity or pressure fields are detected. The method is applied to test cases of ducting and the results are compared with experimental and numerical data.

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Techniques for Turbulence Tripping of Boundary Layers in RANS Simulations

Flow Turbulence and Combustion ◽

10.1007/s10494-021-00296-5 ◽

2021 ◽

Author(s):

Narges Tabatabaei ◽

Ricardo Vinuesa ◽

Ramis Örlü ◽

Philipp Schlatter

Keyword(s):

Boundary Layer ◽

Passive Control ◽

Target Location ◽

Turbine Blades ◽

Three Dimensional ◽

Turbulence Models ◽

Transition Process ◽

Navier Stokes ◽

Test Cases ◽

And Performance

AbstractThe exact placement of the laminar–turbulent transition has a significant effect on relevant characteristics of the boundary layer and aerodynamics, such as drag, heat transfer and flow separation on e.g. wings and turbine blades. Tripping, which fixes the transition position, has been a valuable aid to wind-tunnel testing during the past 70 years, because it makes the transition independent of the local condition of the free-stream. Tripping helps to obey flow similarity for scaled models and serves as a passive control mechanism. Fundamental fluid-mechanics studies and many engineering developments are based on tripped cases. Therefore, it is essential for computational fluid dynamics (CFD) simulations to replicate the same forced transition, in spite of the advanced improvements in transition modelling. In the last decade, both direct numerical simulation (DNS) and large-eddy simulations (LES) include tripping methods in an effort to avoid the need for modeling the complex mechanisms associated with the natural transition process, which we would like to bring over to Reynolds-averaged Navier–Stokes (RANS) turbulence models. This paper investigates the implementation and performance of such a technique in RANS and specifically in the $$k-\omega$$ k - ω SST model. This study assesses RANS tripping with three alternatives: First, a recent approach of turbulence generation, denoted as turbulence-injection method (kI), is evaluated and investigated through different test cases; second, a predefined transition point is used in a traditional transition model (denoted as IM method); and third a novel formulation combining the two previous methods is proposed, denoted $$\gamma -k$$ γ - k I. The model is compared with DNS, LES and experimental data in a variety of test cases ranging from a turbulent boundary layer on a flat plate to the three-dimensional (3D) flow over a wing section. The desired tripping is achieved at the target location and the simulation results compare very well with the reference results. With the application of the novel model, the challenging transition region can be excluded from a simulation, and consequently more reliable results can be provided.

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A Multi Blade-Row Linearised Analysis Method for Flutter and Forced Response Predictions in Turbomachinery

Volume 6: Turbomachinery, Parts A and B ◽

10.1115/gt2006-90789 ◽

2006 ◽

Cited By ~ 1

Author(s):

Gabriel Saiz ◽

Mehmet Imregun ◽

Abdulnaser I. Sayma

Keyword(s):

Travelling Waves ◽

Three Dimensional ◽

Forced Response ◽

Navier Stokes ◽

Test Case ◽

Test Cases ◽

Simple Test ◽

Analysis Method ◽

Turbine Stage ◽

Blade Row

A three-dimensional time-linearised unsteady Navier-Stokes solver is presented for the computation of multistage unsteady flow in turbomachinery. The objective is to address multistage aeroelastic effects for both flutter and forced response. Since the method is currently being developed, only forced response applications are studied in this paper. With this approach, travelling waves, known as spinning modes, are propagated across the multistage domain in order to take into account the interaction between the blade-rows. The method is first validated over two simple test cases for which analytical solutions were available. It is then tested on a turbine stage test case and multistage effects are evaluated from the contribution of one spinning mode included in the model. The results are compared with both time-linearised single-row and nonlinear multirow methods. Multi-row effects are shown not to be important in this case. However, the test case serves as a validation for the implementation of the methodology and further work will focus on the implementation of several spinning modes and the computations of forced response and flutter cases with several blade-rows.

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Numerical Simulation of Wall-Bounded Flows using a Spectral Method with Volume Penalization

ESAIM Proceedings and Surveys ◽

10.1051/proc/201863280 ◽

2018 ◽

Vol 63 ◽

pp. 280-289

Author(s):

Yoichi Sawamura ◽

Katsunori Yoshimatsu ◽

Kai Schneider

Keyword(s):

Numerical Solution ◽

Spectral Method ◽

Three Dimensional ◽

Turbulent Channel Flow ◽

Navier Stokes ◽

Penalization Method ◽

Constant Flow Rate ◽

Slip Boundary ◽

Wall Bounded Flows ◽

Volume Penalization Method

The volume penalization method, which allows to impose no-slip boundary conditions, is assessed for wall-bounded flows. For the numerical solution of the penalized equations a spectral method is used. Considering a two-dimensional Poiseuille flow, the solution of the Navier-Stokes penalized equation is computed analytically and the convergence of the numerical solution is studied. To illustrate the properties of the approach we compute a three-dimensional turbulent channel flow imposing a constant flow rate. The obtained results are compared with reference data of Kim et al. [10].

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Investigation of all-speed schemes for turbulent simulations with low-speed features

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410016687141 ◽

2017 ◽

Vol 232 (4) ◽

pp. 757-770

Author(s):

Ruofan Du ◽

Chao Yan ◽

Feng Qu ◽

Ling Zhou

Keyword(s):

Turbulent Flows ◽

Compressible Flows ◽

Three Dimensional ◽

Navier Stokes ◽

Test Cases ◽

Aerospace Vehicles ◽

Low Speed ◽

Upwind Schemes ◽

Speed Flow ◽

Dependent Parameter

Turbulence plays a key role in the aerospace design process. It is common that incompressible and compressible flows coexist in turbulent flows around aerospace vehicles. However, most upwind schemes in compressible solvers were designed to capture shock waves and have been proved to have difficulties in predicting low-speed flow regions. In order to overcome this defect, many all-speed schemes have been proposed. This paper investigates the properties of the all-speed schemes when applying to Reynolds averaged Navier–Stokes simulations with important low-speed features. First, the correctness of our code is validated. Then four test cases are adopted to evaluate the scheme performance, including a Mach 2.85 compression ramp, the NACA 4412 airfoil, a Mach 2.92 ramped cavity and a three-dimensional surface-mounted cube. Grid-converged results from the all-speed schemes show good agreement with the experimental data and remarkable improvement when compared to standard upwind schemes. Moreover, different from the traditional preconditioning methods, the all-speed schemes are simple to realize and free from the cut-off strategy or any problem-dependent parameter. Therefore, they are expected to be widely implemented into compressible solvers and applied to all-speed turbulent flow simulations.

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Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.4.2020.05.0579 ◽

2020 ◽

Vol 14 (4) ◽

pp. 7369-7378

Author(s):

Ky-Quang Pham ◽

Xuan-Truong Le ◽

Cong-Truong Dinh

Keyword(s):

Stokes Equations ◽

Three Dimensional ◽

Axial Compressor ◽

Aerodynamic Performance ◽

Numerical Results ◽

Single Stage ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Operating Stability ◽

Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

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Experimental and Numerical Analysis of a Motorcycle Air Intake System Aerodynamics and Performance

International Journal of Automotive and Mechanical Engineering ◽

10.15282/ijame.17.1.2020.10.0565 ◽

2020 ◽

Vol 17 (1) ◽

Author(s):

M. A. Abd Halim ◽

N. A. R. Nik Mohd ◽

M. N. Mohd Nasir ◽

M. N. Dahalan

Keyword(s):

Combustion Process ◽

Three Dimensional ◽

Engine Performance ◽

Internal Flow ◽

Rapid Expansion ◽

Navier Stokes ◽

Turbulent Fluctuation ◽

Ansys Fluent ◽

Induction System ◽

Acceleration And Deceleration

Induction system or also known as the breathing system is a sub-component of the internal combustion system that supplies clean air for the combustion process. A good design of the induction system would be able to supply the air with adequate pressure, temperature and density for the combustion process to optimizing the engine performance. The induction system has an internal flow problem with a geometry that has rapid expansion or diverging and converging sections that may lead to sudden acceleration and deceleration of flow, flow separation and cause excessive turbulent fluctuation in the system. The aerodynamic performance of these induction systems influences the pressure drop effect and thus the engine performance. Therefore, in this work, the aerodynamics of motorcycle induction systems is to be investigated for a range of Cubic Feet per Minute (CFM). A three-dimensional simulation of the flow inside a generic 4-stroke motorcycle airbox were done using Reynolds-Averaged Navier Stokes (RANS) Computational Fluid Dynamics (CFD) solver in ANSYS Fluent version 11. The simulation results are validated by an experimental study performed using a flow bench. The study shows that the difference of the validation is 1.54% in average at the total pressure outlet. A potential improvement to the system have been observed and can be done to suit motorsports applications.

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